VNU-UET Repository: No conditions. Results ordered -Date Deposited.
2024-03-28T20:57:08Z
EPrints
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https://eprints.uet.vnu.edu.vn/eprints/
2023-06-15T04:10:13Z
2023-06-15T04:10:13Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4818
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2023-06-15T04:10:13Z
Electrical measurement-type surface plasmon resonance sensor, electrical measurement-type surface plasmon resonance sensor chip, and method for detecting change in surface plasmon resonance
An electricity measuring type surface plasmon resonance sensor includes: a plasmon resonance intensifying sensor chip in which a prism and a sensor chip including an electrode, a silicon semiconductor film, and a plasmon resonance film electrode arranged in this order are arranged in an order of the prism, the electrode, the silicon semiconductor film, and the plasmon resonance film electrode; and an electric measuring apparatus which directly measures a current or voltage from the electrode and the plasmon resonance film electrode.
Armita SANA
Giles ALLISON
Hironori SUZUKI
Hidemi KATO
Masao ANDO
Viet Cuong LE
2022-10-26T21:59:41Z
2022-10-26T21:59:41Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4757
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4757
2022-10-26T21:59:41Z
Electrical measurement-type surface plasmon resonance sensor, Electrical measurement-type surface plasmon resonance sensor chip, and method for detecting change in surface plasmon resonance
Amrita Sana
Giles Allison
Hironoki Suzuki
Hidemi Kato
Masao Ando
Viet Cuong Le
2022-09-20T15:38:40Z
2022-09-20T15:38:40Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4759
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4759
2022-09-20T15:38:40Z
Electricity measuring type surface plasmon resonance sensor, Electricity measuring type surface plasmon resonance sensor chip, method for detecting surface plasmon resonance changes
Amrita Sana
Giles Allison
Hironoki Suzuki
Hidemi Kato
Masao Ando
Viet Cuong Le
2022-08-22T04:06:17Z
2022-08-22T04:06:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4773
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4773
2022-08-22T04:06:17Z
Vortex particle method with iterative Brinkman penalization for simulation of flow past sharp-shape bodies
This paper presents a Lagrangian vortex method combined with iterative Brinkman penalization for the simulation of incompressible flow past a complex geometry. In the proposed algorithm, particle and penalization domains are separately introduced. The particle domain is for the computation of particle convection and diffusion, while the penalization domain is the enforcement of the wall boundary conditions. In iterative Brinkman penalization, the no-slip boundary condition is enforced by applying penalization force in multiple times within each time step. This enables large time step size reducing computational cost and maintains the capability in handling complex geometries. The method is validated for benchmark problems such as an impulsively started flow past a circular cylinder, normal to a flat plate, and a symmetric airfoil at Reynolds numbers ranging from 550 to 1000. The vorticity and streamline contours, drag, and lift coefficients show a good agreement with those reported in literature.
Dung Duong Viet
duongdv@vnu.edu.vn
Zuhal Lavi Rizki
2022-08-22T03:59:25Z
2022-08-22T03:59:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4714
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4714
2022-08-22T03:59:25Z
Modified Savonius Wind Turbine for Wind Energy Harvesting in Urban Environments
Anh Dinh Le
anh.ld@vnu.edu.vn
Duc Minh Banh
Hoang Van Tam
Tran The Hung
2022-08-22T03:56:59Z
2022-08-22T03:56:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4735
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4735
2022-08-22T03:56:59Z
Comparison of Numerical and Experimental Methods in Determining Boundary Layer of Axisymmetric Model
Anh Dinh Le
anh.ld@vnu.edu.vn
2022-08-19T05:36:10Z
2022-08-19T05:36:10Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4733
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4733
2022-08-19T05:36:10Z
Low-Reynolds-number wake of three tandem elliptic cylinders
The flow around three elliptic cylinders with equal spacing and aspect ratio in tandem arrangements was numerically investigated through direct numerical simulation. The spacing ratio (L/D, where D and L are the major axis and the center-to-center distance of two adjacent elliptic cylinders, respectively) ranging from 1.5 to 10 and the Reynolds numbers of
Duong Viet Dung
duongdv@vnu.edu.vn
Nguyen Van Duc
Nguyen Van Tien
Ngo Ich Long
2022-08-19T05:34:26Z
2022-08-19T05:35:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4742
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2022-08-19T05:34:26Z
Support Vector Machine-based Phase Prediction of Multi-principal Element Alloys
Designing new materials with desired properties is a complex and time-consuming process. One of the most challenging factors of the design process is the huge search space of possible materials. Machine learning methods such as k-nearest neighbours, support vector machine (SVM) and artificial neural network (ANN) can contribute to this process by predicting materials properties accurately. Properties of multi-principal element alloys (MPEAs) highly depend on alloys’ phase. Thus, accurate prediction of the alloy’s phase is important to narrow down the search space. In this paper, we propose a solution of employing support vector machine method with hyperparameters tuning and the use of weighted values for prediction of the alloy’s phase. Using the dataset consisting of the experimental results of 118 MPEAs, our solution achieves a cross-validation accuracy of 90.2%. We confirm the superiority of this score over the performance of ANN statistically. On the other dataset containing 401 MPEAs, our SVM model is comparable to ANN
and exhibits 70.6% cross-validation accuracy. We also found that additional variables, including average melting temperature and standard deviation of melting temperature, increase prediction accuracy by 3.34% in the best case.
Hai Chau Nguyen
chaunh@vnu.edu.vn
Masatoshi Kubo
masa104k@ruri.waseda.jp
Viet Hai Le
16020936@vnu.edu.vn
Tomoyuki Yamamoto
tymmt@waseda.jp
2022-03-21T00:42:18Z
2022-03-21T00:42:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4698
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2022-03-21T00:42:18Z
Application of RANS turbulence model in simulation base flow of axisymmetric body in wide range of Mach number
Tran The Hung
Dao Cong Truong
Do Van Minh
Nguyen Minh Trang
Pham Chung
Anh Dinh Le
anh.ld@vnu.edu.vn
2022-03-21T00:32:31Z
2022-03-21T00:32:31Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4715
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4715
2022-03-21T00:32:31Z
Assessment of Flow Fluctuation Pressure Models for Simulating the Cavitating Flow
Anh Dinh Le
anh.ld@vnu.edu.vn
Linh Ngoc Le
Anh Viet Truong
Hung The Tran
2021-12-10T10:55:34Z
2021-12-10T10:55:34Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4632
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2021-12-10T10:55:34Z
Study of Thermodynamic Effect on the Mechanism of Flashing Flow under Pressurized Hot Water by a Homogeneous Model
Anh Dinh Le
anh.ld@vnu.edu.vn
2021-11-27T02:35:16Z
2021-11-27T02:35:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4628
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4628
2021-11-27T02:35:16Z
Effect of the Mesh Types on the Prediction of Flow Aerodynamic around Airfoil
Anh Dinh Le
anh.ld@vnu.edu.vn
Hoang Van Tam
2021-11-27T02:35:03Z
2021-11-27T02:35:03Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4631
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4631
2021-11-27T02:35:03Z
Improvement of Mass Transfer Rate Modeling for Prediction of Cavitating Flow
Anh Dinh Le
anh.ld@vnu.edu.vn
Tran The Hung
2021-11-27T02:34:37Z
2021-11-27T02:34:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4630
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4630
2021-11-27T02:34:37Z
Experimental study of the skin-friction topology around the Ahmed body in cross-wind condition
Tran The Hung
Anyoji Masayuki
Nakashima Takuji
Shimizu Keigo
Anh Dinh Le
anh.ld@vnu.edu.vn
2021-10-31T00:46:00Z
2021-10-31T00:46:00Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4590
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4590
2021-10-31T00:46:00Z
Experimental and Numerical Evaluation of a Simplified Thermodynamic Model for NACA0015 Hydrofoil Cavitation in Hot Water
Anh Dinh Le
anh.ld@vnu.edu.vn
2021-10-31T00:45:33Z
2021-10-31T00:45:33Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4538
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4538
2021-10-31T00:45:33Z
Khảo sát sự tương tác của ánh sáng Vis-NIR đến da người
(Interaction of Vis-NIR Light on Human Skin)
Hấp thụ của phổ ánh sáng nhìn thấy và cận hồng ngoại (Vis-NIR) phụ thuộc vào cấu trúc tế bào sắc tố (chromophore cells) năm ở lớp biểu bì, lớp hạ bì và lớp mỡ dưới da. Hấp thụ ánh sáng làm thay đổi lượng sắc tố melanin hình thành ở các lớp dưới da, do đó ảnh hưởng đến màu sắc của da người.
Cường / Kiên Nguyễn
2021-10-31T00:44:02Z
2021-10-31T00:44:02Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4627
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4627
2021-10-31T00:44:02Z
Improvement of Mass Transfer Rate Modeling for Prediction of Cavitating Flow
Anh Dinh Le
anh.ld@vnu.edu.vn
Hung The Tran
2021-07-06T02:48:22Z
2021-07-06T02:48:22Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4529
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4529
2021-07-06T02:48:22Z
Physico-chemical characterization of forest and agricultural residues for energy conversion processes
Agricultural and forest residues could become potential sources of energy in various countries. However, incomplete understanding regarding physico-chemical properties of these residues presents the main challenges for energy conversion processes. This study presented a complete and comprehensive database of characteristics and compositions of a wide range of agricultural and forest residues. Physical characteristics (moisture, bulk density, calorific value, volatile matter, fixed-carbon content, and ash content), elemental compositions (C, H, N, O, and S), as well as lignocellulosic compositions (cellulose, hemicellulose, and lignin) of ten biomass residues were analyzed. The major impacts of the variability in biomass compositions to biochemical and thermochemical processes were also discussed.
Hong Nam Nguyen
Ngoc Linh Vu
vungoclinh96@gmail.com
Duc Dung Le
Thi Thu Ha Vu
2021-06-28T02:42:11Z
2022-08-22T03:59:29Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4498
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2021-06-28T02:42:11Z
NANOSTRUCTURED LAYERS AND LANGMUIR-SCHAEFER FILMS OF TUNGSTEN TRIOXIDE
Global warming is a pressing issue and many studies have been performed to solve this problem, including applications of nanomaterials in energy-saving systems. This research focuses on the fabrication of tungsten trioxide (WO3) films, a nanomaterial, used in electrochromic devices such as smart window due to its chromic properties.
We synthesized stable floating layers of octadecylamine (ODA) and Na2WO4 in the interface of water-air employing Langmuir-Blodgett method. The compression and chemical volumes were precalculated using Hyperchem to find optimal values. Sodium tungstate salt dissolved in double-distilled water and was poured into the trough. Solution ODA in chloroform was spread on the surface of a liquid by Hamilton syringe and then compressed with the rate of 1.42 cm2/min. The obtained complex ODA and anion was transferred to a glass substrate, annealed at above 350°C, and analyzed. Available wetting methods showed that the substrate turned from a hydrophobic state to a hydrophilic state upon annealing. The absorbance spectrum showed increased absorption in the UV region and relatively low absorption in the visible region (bleached state). Under SEM analysis, the particles were distributed evenly, with some inconsistent particle groupings. Further improvements will be implemented with film quality and annealing temperatures, as well as deposition methods.
Thi Thao Vu
vtthao@vnu.edu.vn
Tri Duc Luong
Thanh Hung Chu
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
2021-06-28T02:36:05Z
2021-06-28T02:36:05Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4293
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2021-06-28T02:36:05Z
Facile Preparation, Characterization of Flexible
Organic Solar Cells Using P3HT-MWCNTS
Composite Photoactive Layer
Multiwalled carbon nanotubes (MWCNTs) mixed in poly(3-hexylthiophene)
(P3HT) were used as a photoactive layer for organic solar cells (OSC). The
flexible OSCs of a structure of PET/rGO-P3HT/P3CT/PCBM/LiF-Al were
prepared by spincoating. The UV-Vis absorption spectra of the photoactive
films and current-voltage characteristics of the OSCs showed the advantage of
the composite devices above the pristine-polymeric ones. Under illumination
of light with a 100 mW/cm2-powerdensity, the photoelectrical conversion efficiency
(PCE) of the OSCs with 3.0 wt% MWNCTs embedded in the photoactive
layer possess a value as large as 2.35%. The obtained results suggest
further useful applications of the flexible large-area solar cells.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2021-06-28T02:34:32Z
2021-06-28T02:34:32Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4548
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2021-06-28T02:34:32Z
Electrodeposited nickel–graphene nanocomposite coating: influence of graphene nanoplatelet size on wear and corrosion resistance
In this paper, we broaden our previous work, which investigated the influence of graphene nanoplatelets (GNPs) size on
microstructure and hardness of composite coatings, to determine the effect of GNP size on wear-resistance and anti-corrosion
property of GNP-reinforced nickel coating (Ni/GNPs). The experimental results indicated that the small GNP material size
could enhance the wear resistance for nickel composite coating with the wear rate of 13.2 × 10–
4 mm3/
Nm, the wear depth
of 17.69 μm. Meanwhile, the anti-corrosion property is enhanced significantly, this is shown via the low corrosion current
density (Icorr value of 1.16 × 10–
7 A/cm2) and the high corrosion potential (Ecorr value of − 0.1661 V). In addition, the mass
lost in salt fog testing is low with the weight of 12.3 mg, which decreased down to ~ 55.27% compared to pristine Ni coating.
These results are attributed to the uniform distribution of the small GNP size inside Ni matrix as well as the grain refinement
effect of composite coating when using the small GNP size.
Van Hau Tran
Van Trinh Pham
Van Tu Nguyen
Nguyen Duc Duoc Phan
Thi Phuong Mai
Xuan Toan Nguyen
Dinh Phuong Doan
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Dinh Lam Vu
Ngoc Minh Phan
Hung Thang Bui
thangbh@ims.vast.vn
2021-06-21T07:06:26Z
2021-06-21T07:06:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4500
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4500
2021-06-21T07:06:26Z
Structural evolution and magnetic properties of Bi0.86Nd0.14Fe1-xTixO3 ceramics
Ceramic Bi0.86Nd0.14Fe1-xTixO3 (0.02 ≤ x ≤ 0.1) compounds were prepared to study the structural evolution, microstructure, and magnetic properties. The structural analysis by X-ray diffraction and Rietveld refinement revealed a coexistence of the polar rhombohedral (R3c symmetry) and antipolar orthorhombic (Pbam symmetry)
structures over the entire composition range, while Raman scattering spectroscopy detected not only the phonon
vibrations of the R3c and Pbam but also the Pbnm symmetries. The microstructure investigation showed the small
and large grain size regions corresponding to the R3c and Pbam/Pbnm phases, respectively. The dependence of
magnetization on the Ti concentration suggested that the weak ferromagnetism observed in the compounds arised from the intrinsic collapse of cycloidal order rather than defect-induced magnetism. The magnetic aging observed at room temperature was explained on the basic of phase switching and spin frustration at the phase boundary. The influence of phase switching induced by an external electric field on the magnetic properties was also studied to reveal the contribution of phase boundary spins to the net magnetization.
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Dang Co Nguyen
cond@vnu.edu.vn
Thi Anh Ho
anhht@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
2021-06-21T07:06:12Z
2021-06-21T07:06:12Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4499
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2021-06-21T07:06:12Z
Electronic structure and multiferroic properties of (Y, Mn)-doped barium hexaferrite compounds
We have systematically studied the crystal and electronic structures and the magnetic and electrical polarization properties of polycrystalline Ba0.95Y0.05Fe12−xMnxO19 (denoted as BaYFe12−xMnxO19) compounds with x = 0–2. The analyzes of X-ray diffraction patterns and Raman scattering spectra indicated their single phase in the M-type hexaferrite structure. With increasing x, the lattice constant a slightly increased while c decreased, which related to the Jahn-Teller effect. Though an increase of x reduced gradually magnetization in a range of 23–32 emu/g, the coercive force increased from 3.3 kOe for x = 0 to about 4 kOe for x = 0.5–2. The study of the electrical polarization properties proved the dependence of the shape of electric hysteresis loops on x and applied electric field. The samples with x = 0 and 0.5 exhibit a weak ferroelectricity with the maximum polarization of ~0.11 μC/cm2 for x = 0, and of ~0.06 μC/cm2 for x = 0.5. Meanwhile, the other samples showed nearly circular hysteresis loops, which are characteristic of conductive materials. Detailed investigations indicated an increase in leakage current when x increased. All of such phenomena are tightly related to the chemical shift of Mn2+ → Mn3+ and the replacement of Mn2+,3+ for Fe3+ in BaYFe12−xMnxO19. These oxidation states and the chemical shift of Mn have been confirmed upon analyzing X-ray absorption spectra
Duc Thang Pham
pdthang@vnu.edu.vn
Dang Co Nguyen
cond@vnu.edu.vn
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Thi Anh Ho
anhht@vnu.edu.vn
2021-06-21T07:04:31Z
2021-06-21T07:04:31Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4496
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2021-06-21T07:04:31Z
CÔNG NGHỆ PHÂN TÍCH KHÍ ỨNG DỤNG NÂNG CAO
HIỆU SUẤT CHÁY NHIÊN LIỆU TRONG SẢN XUẤT
XIMĂNG
Bài báo trình bày tổng quan về các công nghệ phân tích khí và ứng dụng chúng trong công nghiệp
sản xuất ximăng. Công nghệ phân tích khí được trình bày về các cảm biến khí dựa trên nguyên lý hấp
thụ hồng ngoại theo cấu hình không tán sắc (NDIR) và điện hóa được sử dụng trong các kỹ thuật phân
tích theo kiểu trích xuất (extractive) và trực tiếp (in-situ). Ở đây, chúng tôi nhấn mạnh vào cảm biến khí
hấp thụ hồng ngoại và ứng dụng trong công nghệ phân tích khí cho phản hồi vận hành lò nung ủ
Clinker để nâng cao hiệu suất cháy nhiên liệu. Kết quả ban đầu của nhóm nghiên cứu về hai loại cảm
biến khí hấp thụ hồng ngoại và cảm biến khí điện hóa cho ứng dụng trong sản xuất ximăng ở Việt Nam
cũng được thể hiện.
Trường Giang Hồ
gianght@ims.vast.ac.vn
Quang Ngân Phạm
Hồng Thái Giang
Thị Anh Thư Đỗ
Thanh Trung Đỗ
Ngọc Thành Vinh Lê
Ngọc Toàn Nguyễn
2021-05-31T11:03:51Z
2021-05-31T11:03:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4444
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4444
2021-05-31T11:03:51Z
Assessment of a Homogeneous Model for Simulating a Cavitating Flow in Water under a Wide Range of Temperatures
The cavitating flow on a NACA0015 hydrofoil in water under a wide range of temperatures is simulated with or without non-condensation gas using a homogeneous model. Our simplified thermodynamic model is coupled with governing equations to capture the latent heat transfer in cavitation. A numerical evaluation proves its applicability through a comparison with experimental data. As a result, the numerical evaluation illustrates good agreement with measured data for both simulations with or without non-condensation gas. The expected prediction pressure coefficient is in better agreement with experimental data for high-temperature water compared to the existing numerical data. Although the temperature depression inside the cavity is confirmed numerically, the thermodynamic effect shows a weak impact on the cavitation behavior near the boiling temperature (100oC). The cavitating flow can therefore be simulated reasonably by an iso-thermal approach at a reasonable cost. The suppression of the void fraction as the water temperature increases is deduced by the flow behavior rather than the thermodynamic effect. Finally, the impact of a non-condensation gas is closely linked to the thermodynamic properties of the water and the flow behavior. The attached cavity position shifts closer to the hydrofoil leading edge significantly in high-temperature water, while an identical position is reproduced for room temperature conditions in comparison with the simulation without a non-condensation gas.
Anh Dinh Le
anh.ld@vnu.edu.vn
2021-05-31T11:03:11Z
2021-05-31T11:03:11Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4447
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4447
2021-05-31T11:03:11Z
Fluid–structure coupling in time domain for dynamic stall using purely Lagrangian vortex method
This paper presents the purely fast Lagrangian vortex method (FLVM) for the simulation of the external incompressible flows past heaving and pitching bodies with high-frequency oscillation. The Nascent vortex element is introduced to the flow field to retain the Lagrangian characteristics of the solver. The viscous effect is modeled using a core spreading method coupled with the splitting and merging spatial adaptation scheme. The particle’s velocity is calculated using Biot–Savart formulation. To accelerate computation, a fast multipole method (FMM) is employed. The validity of FLVM solver is verified by temporal and spatial convergence studies for the case of flows past an impulsively started cylinder at the Reynolds numbers ranging from 50 to 9500. The accuracy of FLVM is then confirmed for the simulation of flows around the pitching flat plate and oscillating airfoil. The time history of drag and lift coefficients and the vorticity contours show a good agreement with those reported in literature. Furthermore, the FLVM is employed to determine the flutter derivatives and flutter speed of an oscillating flat plate. Results are compared with theoretical solutions based on Theodorsen’s function. In general, the results agree well with those obtained by the inviscid theory.
Duong Viet Dung
duongdv@vnu.edu.vn
Zuhal Lavi Rizki
Muhammad Hari
2021-05-31T11:01:47Z
2021-05-31T11:01:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4446
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4446
2021-05-31T11:01:47Z
Turbulence cascade model for viscous vortex ring-tube reconnection
The reconnection of a vortex ring and a vortex tube in a viscous fluid with the effects of two vortex core sizes (σ 0 = 0.12r 0 and 0.24r 0 , where r 0 are initial ring radius) and three initial flow configurations (left-offset, center and right-offset) at Reynolds number (Re Γ) of 10000 was investigated using a high-order Vortex-in-cell method combined with a Large-eddy simulation model. For the left-offset case, a large part of the ring, slipping over the tube, associates with a small part of the tube to establish a new vortex ring, whereas the rest of the tube is reconnected by another part of the ring. For the center case, half of the ring joins with a part of the tube to construct an elliptical vortex ring while the rest connects because of viscosity. The reconnected ring and tube become more stable and are like the initial ones in the ultimate stage. For the right-offset case, both the ring and tube's reconnection occurs, and the reconnected elliptical vortex ring is rapidly distorted. The proportion of reconnected ring increases, and then this ring section loses its integrity, decaying into a complex cluster of various-scales vortex structures in different shapes. At σ 0 = 0.12r 0 , the secondary vortex structures surrounding the tube and ring appear in three cases, while they are only observed for the center case at σ 0 = 0.24r 0. For three flow configurations and two vortex core sizes, after the reconnection, the energy cascade of the flow approaches a k −5/3 slope of Kolmogorov's similarity hypotheses and a k −3 slope in the ranges of wavenumbers (k) from 3 to 10 and from 10 to 40, respectively. The highest population of small-scale coherent vortex structures is observed for the right-offset, followed by the center and left-offset. In addition, a larger number of these structures were observed for a smaller core size. This validates that the mixing performance is the best at a small vortex core and in the right-offset configuration.
Duong Viet Dung
duongdv@vnu.edu.vn
Nguyen Van Duc
Nguyen Van Luc
nguyenvanluc@tdtu.edu.vn
2021-03-24T04:48:56Z
2021-03-24T04:48:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4395
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4395
2021-03-24T04:48:56Z
Vortex ring-tube reconnection in a viscous fluid
The vortex ring-tube reconnection in a viscous fluid was investigated using a proposed vortex-in-cell method combined with a large eddy simulation model (LVIC). This method was verified using simulations of the Taylor–Green vortex flow at the Reynolds numbers (Re) 200 and 2000. The results show that the present method can capture the small-scale vortex structures in turbulent flows well. Besides, a Lagrangian method for passive scalar transport was successfully developed to track the vortex dynamics. The LVIC was then applied to three simulations of the interaction of a vortex ring at RerΓ(Γ/ν)=10000 and a vortex tube at RetΓ=1000, 5000, and 10 000. At RerΓ=10000 and RetΓ=1000, the effects of the tube on the ring are trivial while the ring breaks it into two parts and entrains them. The flow’s energy spectrum remains unchanged with time, the small-scale vortices are not generated, and the ring’s motion plays a key role in the flow. Moreover, the helicity distribution on the vortices is negligible. At RerΓ=10000 and RetΓ=5000, the tube breaks into two parts, and the leaving part of the tube interacts forcefully with the ring to form the small-scale vortices at the high wavenumbers. The population of small-scale vortex structures increases with time, and the large-scale vortices are twisted after the impingement. At RerΓ=10000 and RetΓ=10000, the impingement of the ring on the tube leads to their breakdown and reconnection. A part of the ring interacts with the leaving part of the tube to form a secondary ring, while the rest replaces the leaving part to reconnect the tube. The population of small-scale vortex structures and helicity distribution increase in this flow stage because of the interaction of the secondary ring wake and connection vortices. However, after the reconnection, the population and helicity distribution on the vortex structures significantly decrease. The smallest-scale vortex structure and the most effective mixing occur with RerΓ=10000 and RetΓ=5000.
Nguyen Van Luc
nguyenvanluc@tdtu.edu.vn
Duong Viet Dung
duongdv@vnu.edu.vn
2021-03-15T04:23:59Z
2021-03-15T04:23:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4389
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4389
2021-03-15T04:23:59Z
Phase Prediction of Multi-principal Element Alloys Using Support Vector Machine and Bayesian Optimization
Designing new materials with desired properties is a complex and time-consuming process. One of the challenging factors of the design process is the huge search space of possible materials. Machine learning methods such as k-nearest neighbours, support vector machine (SVM) and artificial neural network (ANN) can contribute to this process by predicting materials properties accurately. Properties of multi-principal element alloys (MPEAs) highly depend on alloys’ phase. Thus, accurate prediction of the alloy’s phase is important to narrow down the search space. In this paper, we propose a solution of employing support vector machine method with hyperparameters tuning and the use of weights values for prediction of the alloy’s phase. Using the dataset consisting of the experimental results of 118 MPEAs, our solution achieves the cross-validation accuracy of 90.2%. We confirm the superiority of this score over the performance of ANN statistically. On the other dataset containing 401 MPEAs, our SVM model is comparable to ANN and exhibits 70.6% cross-validation accuracy.
Hai Chau Nguyen
chaunh@vnu.edu.vn
Masatoshi Kubo
masa104k@ruri.waseda.jp
Viet Hai Le
Tomoyuki Yamamoto
tymmt@waseda.jp
2020-12-31T01:59:52Z
2020-12-31T01:59:52Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4352
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4352
2020-12-31T01:59:52Z
Cảm biến khí O2 ứng dụng trong ôtô
Truong Giang Nguyen
Ngoc Ha Ngo
Ngoc Khai Nguyen
Dinh Tuan Pham
tuanpd@vnu.edu.vn
Thi Hien Hoang
Truong Giang Ho
2020-12-31T01:56:47Z
2020-12-31T01:56:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4350
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4350
2020-12-31T01:56:47Z
TÌNH TRẠNG PIN LƯU TRỮ (LiFePO4) SỬ DỤNG TRONG ĐÈN BÁO HIỆU
ĐƯỜNG THỦY NỘI ĐỊA
Pin Li-ion LiFePO4 được dùng phổ biến trong đèn báo hiệu đường thủy nội địa ở
Việt Nam do giá thành rẻ, và hiệu quả trong hệ thống đèn sử dụng nguồn năng lượng pin mặt trời và chiếu sáng LED. Tuy vậy, hiện tại đèn báo hiệu dạng này có thời gian sống khá thấp so với thời gian sống thông thường của pin LiFePO4. Trong bài báo này, chúng tôi trình bày tình trạng và một số tham số có thể ảnh hưởng làm giảm tuổi thọ hoạt động của loại pin LiFePO4 dùng trong hệ thống đèn báo hiệu đường thủy nội địa. Các tham số điều kiện môi trường hoạt động như độ ẩm, nhiệt độ, ánh sáng và quá trình sạc/xả được cho là nguyên nhân chính tác động đến thời gian sống của pin trong các đèn báo hiệu.
Truong Giang Nguyen
ntgiang@utc.edu.vn
Sy Hieu Nguyen
Truong Giang Ho
Ngoc Khai Nguyen
Dinh Tuan Pham
tuanpd@vnu.edu.vn
Thi Hoa Nguyen
nthoaly@utc.edu.vn
2020-12-26T09:05:53Z
2020-12-26T09:05:53Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4324
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4324
2020-12-26T09:05:53Z
Hệ thống bốc số xếp hàng đồng bộ thời gian thực đa giao thức
Multi-protocol real-time synchronous queuing system
Theo thống kê mới nhất của Adsota Việt Nam, đầu năm 2020, gần 50% dân số Việt Nam đang dùng điện thoại thông minh (smartphone) với tổng số khoảng 43,7 triệu smartphone; Nhiều người cùng lúc sử dụng hơn 2 chiếc điện thoại với tỷ lệ sở hữu máy trung bình là 1,7 máy/người; Nhiều người Việt lên mạng bằng điện thoại nhiều hơn cả máy tính, con số cụ thể là 68%. Hiện nay, tại Việt Nam có 70% các thuê bao di động đang sử dụng internet từ 3G hoặc 4G với tốc độ trung bình là 14,6 Mbps [1].
Nguyen Thuc Vu
thucvn@vnu.edu.vn
Hoang Gia Nguyen
2020-12-20T15:58:26Z
2020-12-20T15:58:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4294
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4294
2020-12-20T15:58:26Z
Khảo sát sự phục hồi da bằng phương pháp điều trị quang sinh học
Skin Healing with Photobiomodulation Therapy
Quang sinh học (photobiomodulation, PBM) là việc sử dụng ánh sáng đỏ/cận hồng ngoại (NIR) gây ra hiệu ứng sinh học trong các lớp mô (tissues) để chữa lành, phục hồi và kích thích các quá trình sinh lí và phục hồi những tổn thương do chấn thương hoặc bệnh gây ra. Trong bài này giới thiệu PBM được sử dụng cho điều trị da có mụn do trứng cá, da bị bạch tạng (lang ben), rối loạn sắc tố da, bỏng da và sẹo da do bỏng...Thông số điều trị: như bước sóng ánh sáng, công suất, mật độ chiếu xạ...đến sự phục hồi da đã đượ thảo luận trong báo cáo.
Cường / Kiên Nguyễn
cuongnk@vnu.edu.vn
2020-12-16T01:43:30Z
2020-12-16T01:43:30Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3632
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3632
2020-12-16T01:43:30Z
Nghiên cứu vi nấm nội sinh cây Thạch tùng răng cưa (Huperzia serrata) có khả năng sinh tổng hợp enzyme β-galactosidase
Enzyme β-galactosidase được khai thác ứng dụng trong các lĩnh vực khác nhau như y tế, công
nghiệp chế biến thực phẩm, công nghệ sinh học. Trong nghiên cứu này, 45 chủng vi nấm nội
sinh phân lập từ cây thảo dược Thạch tùng răng cưa phân bố tại Việt Nam được sàng lọc khả
năng sinh tổng hợp enzyme β-galactosidase. Kết quả tuyển chọn được 2 chủng có khả năng tổng
hợp β-galactosidase, trong đó chủng TĐL28.1 có hoạt tính enzyme đạt 1,92 IU/ml cao hơn
chủng TĐL5v (0,36 IU/ml). Hai chủng đã được dịnh danh là Aspergillus niger TĐL28.1 và
Fungal sp. Tsp5v.
Thị Minh Thành Lê
Thị Hồng Anh Hoàng
Thi Quyen Ha
quyenht@vnu.edu.vn
Thị Tuyên Đỗ
2020-12-14T07:27:55Z
2020-12-14T07:27:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3282
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3282
2020-12-14T07:27:55Z
Analysis of gene encoding haemolysin A of Vibrio cholerae isolated in Vietnam
Vibrio cholerae is the cholera causing agent, divided into two biotypes, including the classical biotype and ElTor biotype. Both of these biotypes caused cholera epidemics in the world. The classical biotype caused 6th cholera pandemic (from 1921 to 1961), and ElTor biotype caused 7th cholera pandemic (from 1961 to the 70s). Haemolysin A, a hemolytic protein of V. cholerae ElTor biotype, is encoded by the hlyA gene. This gene is often used for analyzing genetic relationship between strains in the same species or between species in the same Vibrio genus. Results of analyzing nucleotide and amino acid sequences of hlyA gene of V. cholerae strain causing cholera in Vietnam (named hlyA.VN) showed that: the hlyA.VN gene sequence was similar to the hlyA gene sequences of V. cholerae strains of the 6thand 7thcholera epidemics. The hlyA gene of the 6th cholera epidemic strain was deficient in 11 nuleotides (this deficiency leading to the loss of 4 amino acids in the haemolysin A protein) comparing to hlyA.VN gene and hlyA gene of the 7th cholera epidemic strain. The results of genetic distance analysis as well as phylogenetic tree construction also confirmed V. cholerae causing cholera in Vietnam was closely relationship to the strains causing cholera pandemics in the world. It is great significance for the surveillance of molecular epidemiology to prevent cholera effectively.
Thi Quyen Ha
quyenht@vnu.edu.vn
2020-12-14T05:03:26Z
2020-12-14T05:03:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4263
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4263
2020-12-14T05:03:26Z
Màng nổi của 5,10,15-triphenylcorrole
Đã nghiên cứu thực nghiệm và lý thuyết sự tạo màng nổi Langmuir-Blodgett của 5,10,15-triphenylcorrole H3[(ms-Ph)3Cor] từ dung dịch dichloromethane (c=1.2x10-4 mol/l) với tốc độ nén màng v= 2.3 cm2/phút. Kết quả cho thấy khi phủ từ 4.3 đến 92.8% bề mặt nước bằng các phân tử corrole và nén, các màng mỏng cấu trúc nano khác nhau (từ mono-(2D), đến bi- và tetralayer (3D)) mà thành phần tạo nên chúng là các nanoaggregates với sự định hướng của phân tử theo các cách khác nhau face-on, edge-on đã được hình thành. Điều kiện tồn tại ổn định của các lớp màng và các đặc tính cơ bản các loại màng nổi thu được đã được xác định cụ thể. Trên dữ liệu thực nghiệm và tính toán mô hình các thông số màng đã thiết lập được pasport về quá trình tạo màng nổi đặc trưng riêng cho ligand corrole và đây chính là cơ sở để kiểm soát tính chất màng nổi ở cấp độ phân tử theo yêu cầu trước khi chuyển chúng lên đế rắn để nghiên cứu và ứng dụng vào các lĩnh vực thực tiễn.
Thi Thao Vu
vtthao@vnu.edu.vn
2020-12-11T23:17:42Z
2020-12-14T07:36:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4252
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4252
2020-12-11T23:17:42Z
Characterization of COOH-Molecules Self-Asembled on Gold Nanoparticles
11-MUAsolution of the concentration of 10mM was deposited on a gold sutface through the self-assembled molecules. The gold surface was characterized by AFM-topography and XRD-spectrum. Both results show that the gold surface was composed of gold nanoparticles (AuNPs) piling up on each other and the most significant peak, centered at 2θ = 38.2°, is originated from the face centered cubic gold, respectively. COOH-functional molecules were self-assembled onto AuNPs surface through the reaction between thiol molucules and AuNPs to from the AuS binding. The IR spectrum of a COOH-terminated AuNP sample show the existence of carbonyl (C=O) and hydroxyl (OH) molecules on AuNP surface. Furthermore, COHNFITC@SiO2 bonding to AuNPs, observed on a confocal microscope, also revealed the COOH-molecules selft-assembled to AuNP-sample.
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2020-12-11T01:40:47Z
2020-12-11T01:40:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4237
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4237
2020-12-11T01:40:47Z
Synthesis and optical characterization of asymmetric multilayer metal–insulator nanocrescent in aqueous solutions
The metal–insulator–metal (MIM) nanostructures on polystyrene sphere (PS) were fabricated by the sputtering method. Asymmetric PS-MIM nanocrescent (AMNC) was separated and dispersed into the solution employing the sonication method. The absorption properties of AMNC colloidal solution were measured and calculated with the use of spectroscopy and discrete dipole approximation methods. The results indicated that hybridization of elementary plasmons of individual AMNC particles played an important role in determining optical properties of this colloidal solution, which were determined to be functions of component layer thickness and particle density. These findings are expected to enhance the pharmaceutical deliveries and biosensor fabrication.
Tien Thanh Pham
Dinh Dat Pham
Thi An Hang Nguyen
Minh Thong Vu
Lien Ha Thi Nghiem
Tien Van Nguyen
Daisuke Tanaka
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
2020-12-11T01:38:52Z
2020-12-23T03:15:00Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4226
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4226
2020-12-11T01:38:52Z
Structural, Optical, Ferroelectric and Ferromagnetic Properties of Bi1xGdxFeO3 Materials
Bi1xGdxFeO3 (BGFO) (x = 0.00 7 0.15) materials were prepared by a sol-gel method. The effect of Gd doping on the structural, ferromagnetic, and ferroelectric properties of BiFeO3 (BFO) were analyzed using x-ray diffraction, Raman scattering, energy-dispersive x-ray spectroscopy, ferroelectric hysteresis loop and magnetic hysteresis loop measurements. All samples showed
a rhombohedral structure of the perovskite type. The a and c lattice parameters decreased with Gd content, obeying Vegard’s law, from 5.583 A˚ to 5.511
A˚ , and from 13.869 A˚ to 13.741 A˚ , respectively. The optical band gap (Eg) also decreased with Gd content, from 2.02 eV to 1.60 eV at x = 0.00 to x = 0.15,
respectively. The ferroelectric and ferromagnetic properties of the BGFO materials were enhanced compared with those of the pure BFO material. Maximum saturation polarization (Ps) and saturation magnetization (Ms) values of 6.88 lC/cm2 and 0.386 emu/g were obtained. We found that the optimum Gd doping content to enhance multiferroic properties of BFO material is in range from x = 0.10 to x = 0.125. The origin of ferromagnetic
and ferroelectric properties of BGFO materials were also discussed.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
2020-12-11T01:37:56Z
2020-12-11T01:37:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4209
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4209
2020-12-11T01:37:56Z
Fabrication and characteristics of Zn1–xSnxO nanorod/ITO composite photocatalytic films
Zn1−xSnxO NRs/ITO composite photocatalytic films were fabricated by the hydrothermal method. A
concentration of Sn dopant in Zn1−xSnxO nanorods(NRs)was varied from 0% to 7%. The structural
and surface morphology characteristics of Zn1−xSnxO NRs/ITO composite photocatalytic films were
investigated by X-Ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. In
addition, photocatalytic properties of synthesized materials were evaluated by degradation rates of
Rhodamine-B aqueous solutions under UV light irradiation. The SEM results indicated that, with an
increasing concentration of Sn dopant in Zn1−xSnxO NRs/ITO, the effective surface areas were
declined by an exponential decay function and the reduction was negligible as the Sn doping
concentration was higher than 3%. With the similarity in effective surface area, the contribution of Sn
in the enhancement of the photocatalytic activity of Zn0.93Sn0.07O NRs/ITO is clearly observed with
41% improvement in comparison to ZnO NRs/ITO.
Thi Dung Nguyen
Tran Chien Dang
Duc Thien Trinh
Anh Tuan Duong
Duc Thang Pham
Nang Dinh Nguyen
Dinh Lam Nguyen
2020-12-11T01:37:43Z
2020-12-26T14:26:01Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4208
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4208
2020-12-11T01:37:43Z
Experimental and numerical study on photocatalytic activity of the ZnO nanorods/CuO composite film
The photocatalytic activity of the ZnO NRs/CuO composite film was investigated by using both experimental and numerical methods. The ZnO NRs/CuO composite film exhibits significantly enlarge absorption range to visible-light and suppress the recombination rate of the photogenerated electron-hole pairs, which can be well utilized as a photocatalyst. The ZnO NRs/CuO composite film also presents good stability, and reusability, and durability for photo-decomposition purpose. The optimal ZnO NRs/CuO composite film contains 1μ-thick of CuO film and 10 nm-thick of ZnO NRs film. The donor concentration in ZnO NRs film should be lower than 1016 cm−3. The short circuit current density of the optimal composite film is 25.8 mA/cm2 resulting in the calculated pseudo-order rate constant of 1.85 s−1. The enhancement in degradation efficiency of this composite film is attributed to the inner electric field and large effective surface area of ZnO NRs film.
Thi Dung Nguyen
dungtnguyen@vnu.edu
Minh Duc Tran
minhductran911@gmail.com
Van Thanh Hoang
hoangvanthanh12b4ksa2015@gmail.com
Duc Thien Trinh
Duc Thang Pham
thangducpham@yahoo.com
Dinh Lam Nguyen
Lamnd2005@gmail.com
2020-12-10T11:00:58Z
2020-12-10T11:00:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4234
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4234
2020-12-10T11:00:58Z
Modelling of Lattice Constants of the Garnet Structured Compounds Using Machine Learning
Garnet structured compounds have been widely utilized as the host materials of phosphors. Due to their complicated structures with numerous atoms in a unit cell of the garnet structure, it is difficult to predict their crystal structures accurately by the first principles calculation, especially when they include magnetic elements. It was proposed to predict the structural parameters for spinel compounds by the empirical model employing ionic radii
and electronegativities, which reproduced the experimental structural parameters of spinels successfully. In the present work, we propose a comprehensive and reliable model to explain and/or predict the structural parameters of the garnet structured materials using the machine learning. The lattice parameters of 182 garnet compounds reported in the database are compiled in our dataset to train the model. Using the ionic radii and electronegativities of the constituent elements of considered garnet compounds, we constructed the linear regression model fitted to the garnets' lattice constants in the dataset. The predicted values obtained as a result of the training of the model exhibited high correlation with the actual lattice constants, having the correlation coefficient of 0.988. For each composition in our dataset, the relative error between experimental and calculated lattice constants was less than 1.60%.
Masatoshi Kubo
masa104k@ruri.waseda.jp
Hai Chau Nguyen
chaunh@vnu.edu.vn
Sergey Brik
Tomoyuki Yamamoto
tymmt@waseda.jp
2020-12-08T09:33:08Z
2021-06-28T02:41:34Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4148
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4148
2020-12-08T09:33:08Z
Nanomaterials for Organic Optoelectronic Devices: Organic Light-Emitting Diodes,
Organics Solar Cells and Organic Gas Sensors
This paper presents a unified view on applied nanomaterials that have been developed for a group of organic optoelectronic devices such as
Organic Light-Emitting Diodes (OLEDs), Solar Cells (OSCs) and Gas Sensors (OGSs). From recent references, included our unpublished one, it
has been demonstrated that nanostructured particles of metals, semiconductors, and oxides in conducting polymers embedded in conducting
polymers have significantly contributed to improving both the performance parameters and working time of devices. The presence of inorganic
nanoparticles in polymeric matrices has strongly influenced all physical properties of the polymers. However, herein the most interesting
properties of OLEDs, OSCs, and OGSs are of electro-luminescence, photo-electrical conversion, and gas sensing, respectively. A publication has
been seen regarding the nanostructured materials used for the fabrication of nanocomposite devices which aim at different practical purposes.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2020-12-08T09:32:58Z
2020-12-08T09:32:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4131
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4131
2020-12-08T09:32:58Z
Effect of crystallization temperature on energy-storage density and efficiency of lead-free Bi0.5(Na0.8K0.2)0.5TiO3 thin films prepared by sol–gel method
Lead-free Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT) ferroelectric films were synthesized on Pt/Ti/SiO2/Si substrates via the chemical solution deposition. The influence of the crystallization temperature on the microstructures, the ferroelectric and energy-storage properties of the films was investigated in detail. The results showed that the BNKT films have reached the well crystallized state in the single-phase perovskite structure at 700 °C. Ferroelectric and energy-storage properties of the films were significantly enhanced by increasing the crystallization temperature. The remnant polarization (2Pr) and maximum polarization (2Pm) reached the highest values of 18.4 μC/cm2 and 61.2 μC/cm2, respectively, under an applied electric field of 300 kV/cm. Thanks to the strong enhancement in 2Pm and the large Pmax - Pr value, the highest energy-storage density (Jreco) and efficiency of 2.3 J/cm3 and 58.2%, respectively, were obtained. These results indicate that the BNKT films have application potentials in advanced capacitors.
Dang Co Nguyen
cond@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Viet Cuong Le
cuonglv@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
2020-12-04T08:33:25Z
2020-12-04T08:33:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4142
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4142
2020-12-04T08:33:25Z
DEVELOPMENT OF A MULTI-WAVELENGTH RANGE DEVICE
USING HIGH POWER LEDS FOR PHOTOTHERAPY
Abstract. Phototherapy has been used since ancient times using sunlight. Nowadays,
thanks to the development of semiconductor technology, compact and convenient use of
phototherapy devices can be manufactured. In this report, we present the results of
fabricating a phototherapy device using multi-wavelength LEDs, in the range from red to
near-infrared. The device uses optical fiber bundles, very flexible to use, with an optical
power of each output over 300mW, operating in pulsed and continuous mode. Techniques
to use the equipment fabrication will be briefly described. Some basic parameters of LED
devices have been studied and investigated. The multi-wavelength phototherapy LED
device could be used for research in open wound recovery, chronic wound healing, pain
relief, as well as treatment of current osteoarthritis diseases based on photobiomodulation
mechanisms.
Bui Binh Nguyen
Duc Loi Tang
Mikulich Aliaksandr
Thi Yen Mai Nguyen
2020-12-04T08:33:11Z
2020-12-04T08:35:14Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4144
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4144
2020-12-04T08:33:11Z
REALIZATION A FAST OPTICAL SHUTTER
The precision in time of light exposure requires the optical shutter in an optical
system to work with high-speed response and rapid change between close/open state,
however, a motor-driven system cannot attain perfect accuracy due to the system
response. This is the unsolvable problem that comes when designing an optical shutter;
and with different methods to approach the problem, many types of shutter with various
parameters have been built. The most popular optical shutters now in the market are made
by Thorlabs with acceptable responses to the controller but they are very expensive. In
this paper we have developed an optical shutter system using Arduino software and hard
disk drive base, which is superior to some characteristic of Thorlabs' shutter (e.g transfer
initialize, transfer open, minimum open pulse), but also much cheaper and can be widely
manufactured.
Thuy Linh La
Quoc Tien Tran
Quang Cong Tong
Mikulich Aliaksandr
Thi Yen Mai Nguyen
mainty85@gmail.com
2020-12-04T08:30:59Z
2020-12-04T08:30:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4145
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4145
2020-12-04T08:30:59Z
NGHIÊN CỨU THIẾT KẾ CHẾ TẠO BỘ ĐIỀU KHIỂN LÀM LẠNH
CHO LASER BÁN DẪN CÔNG SUẤT CAO
Điều khiển nhiệt độ cho pin nhiệt điện công suất cao nhằm làm lạnh cho laser
bán dẫn là vấn đề quan trọng giúp laser hoạt động ổn định, tăng hiệu suất, tuổi thọ làm
việc. Phương pháp làm lạnh cho laser bán dẫn đã được nghiên cứu chế tạo trên cơ sở
pin nhiệt điện Peltier và cảm biến nhiệt độ bán dẫn. Công trình nghiên cứu này giới
thiệu một số kết quả nghiên cứu thiết kế chế tạo bộ điều khiển làm lạnh cho laser bán
dẫn công suất cao sử dụng pin nhiệt điện Peltier (TEC) với các ưu điểm vượt trội đáp
ứng hiệu suất làm mát nhanh mang lại hiệu quả cao không chỉ về mặt công suất mà
còn cả mặt kinh tế, chi phí giá thành thấp lại nhỏ gọn. Các kỹ thuật sử dụng để chế tạo
bộ điều khiển làm lạnh cho laser được thiết kế, mô tả, ứng dụng thử nghiệm trong việc
điều ổn định nhiệt độ cho laser. Những vấn đề cơ bản của thiết bị như công suất hoạt
động, khả năng đáp ứng kiểm soát, độ ổn định nhiệt độ hoạt động của bộ điều khiển
ổn định nhiệt độ đã được nghiên cứu khảo sát.
Đức Lợi Tăng
Bình Nguyên Bùi
Mikulich Aliaksandr
Thi Yen Mai Nguyen
mainty85@gmail.com
2020-12-04T08:30:01Z
2020-12-04T08:30:01Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4127
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4127
2020-12-04T08:30:01Z
Using cassava waste of the cassava starch processing as food for raising African Nightcrawler (Eudrilus eugeniae) to obtain vermicomposting and earthworm biomass
The raising earthworms by cassava waste is a useful solution to reduce environmental pollution caused by cassava starch
processing. In this study, cassava waste (including cassava peel, cassava pieces and soil) was used as a food source for
raising African Nightcrawler (Eudrilus eugeniae) with experiments as follows: Experiment 1: earthworms were raised in
crushed cassava waste right after being discharged; Experiment 2: earthworms raised in crushed cassava waste that had
been incubated with organic matter decomposing microbiological preparation for the previous two weeks; Experiment 3:
earthworms were raised in crushed cassava waste that had self-decomposed naturally for the previous two weeks. The
cassava waste was decomposed naturally for 4 weeks for the control. Besides, the crushed cassava waste was also
incubated by organic matter decomposing microbiological preparation for 4 weeks for getting more data for comparison
between experiments (Experiments 4). The experiments were followed for 4 weeks. The results showed that the content of
organic matter, humic acid and total nitrogen in organic cassava humus obtaining from experiments increased comparing
to the control: total organic matter content reached from 10.4%-15.7%, higher than the control (8.2%) from 1.27-1.92
times, humic acid content reached 0.6 - 0.8% and total nitrogen reached 0.3%. In which, the experiment 3 had the highest
quality of humus (organic matter content 15.7%, total nitrogen 0.3%, humic acid 0.7% and fulvic acid 0.5%). The
experiment 3 also had the highest earthworm biomass (3.6kg), increasing 30.5% comparing to experiment 1 and 19.4%
comparing to experiment 2. Therefore, experiment 3 was proposed for application in treatment of cassava waste in larger
scale. The organic humus obtaining from raising earthworms by cassava waste can be used as raw materials for producing
vermicompost. The earthworm biomass can be used as protein rich food for domestic animals (such as chicken, tortoise,
eel, fish...) or used as nutritious fertilizer.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Minh Thanh Le
minhthanh.ibt@gmail.com
2020-12-04T08:29:45Z
2020-12-04T08:29:45Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4126
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4126
2020-12-04T08:29:45Z
Selection of nitrogen fixation and phosphate solubilizing
bacteria from cultivating soil samples of Hung Yen province
in Vietnam
The nitrogen fixing bacteria (NFB) and phosphate solubilizing bacteria (PSB) are used widely for producing of
microbiological fertilizers. This study aims to seek nitrogen-fixing and phosphate-solubilizing bacteria strains to add to
the collection of candidate strains for producing single and multi-function microbiological fertilizers. From 40 soil
samples of 8 fields for cultivating rice, medicinal plants and vegetables, 15 NFB strains and 12 PSB strains were
isolated and determined the ability of fixing nitrogen and solubilizing inorganic phosphate compound through creation
of NH4+ and PO4- in culture medium. Among 15 NFB strains, the fixing nitrogen activities of 7 strains were much higher
than the remaining strains, including NFBR3, NFBV2, NFBM5, NFBM3, NFBM1, NFBV5 and NFBR2 with NH4+
concentration 18.85 mg/l, 18.41 mg/l, 17.32 mg/l, 16.19 mg/l, 15.49 mg/l, 12.83 mg/l and 12.57 mg/l, respectively
Among 12 PSB strains, The ability of solubilizing phosphate of 5 strains were higher than the others, including PSBM2,
PSBR1, PSBV1, PSBR5 and PSBR3 with PO4- concentration 14.49 mg/l, 11.83 mg/l, 11.33 mg/l, 10.65 mg/l, 10.37 mg/l,
respectively.. 3 NFB strains (NFBR3, NFBV2, NFBM5) and 3 PSB strains (PSBM2, PSBR1, PSBV1) with higher activity were
identified by 16S-rDNA sequence analysis and comparing to some homologous sequences in genbank. The results
showed that NFBR3 was identified as Azotobacter vinelandii, NFBV2 as Azopirillum brasilense, NFBM5 as Azotobacter
chroococum, PSBM2 and PSBV1 as Pseudomonas fluorescens and PSBR1 as Bacillus subtilis.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Thu Ha Chu
hachuthi@yahoo.com
2020-12-04T08:28:24Z
2020-12-04T08:28:24Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4124
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2020-12-04T08:28:24Z
ĐIỀU TRA VI SINH VẬT TRONG ĐẤT NÔNG NGHIỆP VÀ NƯỚC TƯỚI
Ở MỘT SỐ XÃ THUỘC TỈNH HƯNG YÊN
Vi sinh vật trong đất là một trong các dấu hiệu để đánh giá chất lượng đất nông nghiệp. 40 mẫu đất trồng các loại cây khác nhau được thu từ 8 ruộng và 20 mẫu nước tưới được thu từ 6 nguồn nước tại khu vực đồng ruộng của 4 xã thuộc huyện Khoái Châu và Yên Mỹ của tỉnh Hưng Yên được phân tích đánh giá sự đa dạng của một số nhóm vi sinh vật. Kết quả cho thấy số lượng vi sinh vật đạt giá trị cao nhất lần lượt trong các mẫu đất và nước như sau: vi sinh vật hiếu khí tổng số: 1x107 CFU/g và 2,7x106 CFU/ml; vi khuẩn cố định đạm sống tự do Azotobacter: 4,2x103 CFU/g và 4x101 CFU/g; vi khuẩn cố định đạm sống hội sinh Azospirillum: 2,5x102 CFU/g và 1,9x 101 CFU/ml; vi sinh vật phân giải phosphate: 4,2x105 CFU/g và 8,3x101 CFU/ml; vi khuẩn phân giải cellulose: 3,4x106 CFU/g và 7,8x102 CFU/ml, xạ khuẩn phân giải cellulose: 3,2x105 CFU/g và 6,7x101 CFU/ml, vi nấm phân giải cellulose: 2,4 x 104 CFU/g và 5,6 x 101 CFU/ml. Với mật độ vi sinh vật rất thấp cho thấy chất lượng đất trồng tại đây đang bị giảm sút. Vì vậy cần hạn chế sử dụng phân bón và thuốc trừ sâu hóa học, đồng thời chú trọng đến biện pháp canh tác hữu cơ nhằm gia tăng quần thể vi sinh vật tự nhiên có lợi trong đất, từ đó cải thiện chất lượng đất trồng.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Thu Ha Chu
hachuthi@yahoo.com
Thi Minh Thanh Le
minhthanh.ibt@gmail.com
2020-12-04T08:21:28Z
2020-12-04T08:21:28Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4034
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4034
2020-12-04T08:21:28Z
Designing and patterning a thermotherapy device for inflammation and pain
This technical report will present the experimental approaches to realize a thermotherapy device for inflammation and pain. The objective is to develop a device for cool therapy. Peltier battery is chosen for cooling. Aluminum plates are used for transferring heat.
Thi Yen Mai Nguyen
mainty85@gmail.com
2020-11-30T07:04:33Z
2020-11-30T07:04:33Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4094
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4094
2020-11-30T07:04:33Z
Quy trình chế tạo mặt nạ kim loại sử dụng máy khắc Laze Fiber thương mại, ứng dụng trong kỹ thuật phún xạ để chế tạo các chi tiết có kích thước cỡ mili-mét
Anh Tam Ho
hoanhtam@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Khac Quynh Le
2020-11-30T07:04:27Z
2020-11-30T07:04:27Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4092
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4092
2020-11-30T07:04:27Z
Bộ phận dẫn tập trung và khuếch đại từ thông dạng vành khuyên và hệ thống tích hợp
Sáng chế đề cập tới mạch dẫn, tập trung từ thông có dạng hình vành khuyên (1) có kết cấu bao gồm: giới hạn bởi 2 hai đường tròn có đường kính ngoài là D_ng và và đường kính trong là D_tr bố trí lệch tâm tạo thành 2 phần không đối xứng với một bên dày hơn có độ rộng w và một bên mỏng hơn có độ rộng s. Trên đường kính là trục đối xứng của hai vòng tròn này có khoét một lỗ 4 có đường kính h nằm ở bên phía ra dày hơn của mạch dẫn này. Lỗ khoét này chính là vị trí kênh dẫn vi lưu để dẫn hạt từ 2 chạy xuyên qua. Phía bên kia của mạch dẫn tại vị trí mỏng nhất, một khe hở 5 có độ rộng g và chiều ngang là s được tạo ra ra để để đặt cảm biến 3 vào chính giữa phần không gian khe hở này. Khoảng cách từ tâm hạt từ đến tâm cảm biến là L và độ dày của tấm này là t. Các kích thước này đã được tính toán và lựa chọn tối ưu cho từ trường tập trung mạnh nhất.
Hệ thống tích hợp bao gồm kênh dẫn vi lưu cảm biến ừ và mạch dẫn tập trung và khuếch đại từ thông hình vành khuyên có kết cấu bao gồm: mạch dẫn và tập trung từ thông 1 như mô tả trong khía cạnh thứ nhất nhất của sáng chế này, cảm biến đo từ trường 3 có kích thước tương thích với kích thước của hạt từ 2 cần dò tìm có sẵn các điện cực 7, hệ thống kênh dẫn vi lưu 6 dẫn chất lỏng có chứa các hạt hát từ tính chạy xuyên qua lỗ 4 trên mạch dẫn tập trung từ thông 1 được thực hiện ở khía cạnh thứ nhất của sáng chế này.
Anh Tam Ho
hoanhtam@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Anh Tuan Phung
Viet Hung Nguyen
viethung1996vn@gmail.com
2020-11-30T07:04:13Z
2020-11-30T07:04:13Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4091
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2020-11-30T07:04:13Z
LINH KIỆN CẢM BIẾN ĐO TỪ TRƯỜNG 3 TRỤC VÀ PHƯƠNG PHÁP CHẾ TẠO LINH KIỆN NÀY, THIẾT BỊ ĐO TỪ TRƯỜNG TRÁI ĐẤT ĐIỆN TỬ TÍCH HỢP VỚI HỆ THỐNG ĐỊNH VỊ GPS VÀ TRUYỀN PHÁT KHÔNG DÂY PHỤC VỤ KHẢO SÁT, THĂM DÒ VÀ VẼ BẢN ĐỒ TỪ TRƯỜNG CÓ LINH KIỆN CẢM BIẾN NÀY
Sáng chế là tạo ra linh kiện cảm biến đơn trục cho phép đo và xác định thành phần từ trường dọc theo trục cảm biến cả về cường độ và dấu (cùng hướng hay ngược hướng của trục cảm biến). Đây là bộ phận cảm biến hoạt động dựa trên hiệu ứng tổ hợp từ điện có độ nhạy, độ phân giải cao, độ ổn định và lặp lại cao nhờ sử dụng vật liệu với cấu hình thiết kế phù và chế tạo phù hợp. Mục đích khác của sáng chế là chế tạo linh kiện cảm biến 3 trục 18 có kết cấu bao gồm 3 linh kiện cảm biến đơn trục 1 ở trên được bố trí theo 3 cạnh vuông góc không chung đỉnh với nhau trong một hình hộp lập phương. Mục đích khác của sáng chế là đề xuất thiết bị điện tử đo từ trường trái đất có kết cấu bao gồm linh kiện cảm biến 3 trục 18 ở trên kết nối với mạch điện tử có chức năng đo lường và xử lý tín hiệu số và hệ thống cảm biến chuyển động. Mục đích khác của sáng chế là tạo ra hệ thống đo và vẽ từ trường trái đất có sử dụng thiết bị điện tử đo từ trường trái đất 3 trục ở trên tích hợp với hệ thống định vị GPS và hệ thống truyền phát không dây đáp ứng yêu cầu của thiết bị với độ phân giải từ trường 0.1 nT tuyến tính trong toàn dải đo từ -120.000 đến 120.000 nT và độ phân giải góc 10-1 độ. Hệ thống cho phép định vị vị trí trong không gian với độ chính xác cỡ 3 m và truyền phát không dây trong bán kính lên đến 8 km.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Anh Tam Ho
hoanhtam@vnu.edu.vn
Viet Hung Nguyen
viethung1996vn@gmail.com
Thi Ngoc Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
Anh Tuan Phung
Dinh Cuong Trinh
Dinh Duong Do
Ba Bien Nguyen
2020-11-30T07:04:01Z
2020-11-30T07:04:01Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4090
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4090
2020-11-30T07:04:01Z
NGHIÊN CỨU XÁC ĐỊNH DẤU VẾT TỪ TRƯỜNG
CỦA MỘT SỐ MÔ HÌNH VỎ TÀU SẮT TỪ
Ngày nay, tàu mặt nước và tàu ngầm đều được chế tạo bằng vật liệu sắt từ, nên chúng dễ bị đối phương “nhìn thấy” dấu vết từ trường khi hoạt động trên biển. Do đó, việc nghiên cứu các phương pháp, kỹ thuật để phân tích, xác định và khử dấu vết từ trường là một vấn đề rất cần thiết, cấp bách và mang tính thời sự. Tuy nhiên, việc xác định dấu vết từ trường cho tàu thực tế rất phức tạp và yêu cầu khối lượng tính toán lớn. Chính vì vậy, người ta thường nghiên cứu trên các mô hình có cấu trúc tương đương với hình dạng của vỏ tàu thực tế. Với mục đích đó, bài báo sẽ tập trung vào tính toán và mô phỏng mô hình vỏ tàu hình cầu và hình cầu kéo dài, sử dụng kết hợp 3 phương pháp: giải tích, phần tử hữu hạn và bán giải tích, để đưa ra các nhận xét và đánh giá sơ bộ về đặc điểm, xu hướng dấu vết từ trường; đánh giá hiệu quả và khả năng vận dụng trong các nghiên cứu về phát hiện và tàng hình từ trường cho các tàu mặt nước và tàu ngầm.
Dinh Cuong Trinh
Dinh Duong Do
Le Ha Vu
Thi Huong Giang Do
giangdth@vnu.edu.vn
Anh Tuan Phung
2020-11-30T07:03:47Z
2020-11-30T07:03:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4089
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4089
2020-11-30T07:03:47Z
Giant magnetoelectric effects in serial-parallel connected Metglas/PZT arrays with magnetostrictively homogeneous laminates
To ensure the magnetostrictive softness, the homogeneity, the decrease of the shear-lag effect and the
space-saving construction of narrowed longitudinal-transverse L-T magnetoelectric (ME) composites, a
novel parallel-connected-multi-bars (PCMB) geometry of PZT/Metglas is proposed and investigated by
simulation and experiment. In this case, Metglas layers are structured in different geometries from the
conventional single bar (c-SB) to conventional separated multiple bars (c-SMB), elongated separate
multi-bar (e-SMB) and n-magnetic-bar based PCMB (n-PCMB). This n-PCMB geometry divides the conventional
ME configuration into n parallel-connected ME units (n-PCMEU) according to the magnetic
geometries. The optimal ME performance with the largest ME voltage coefficient aE of 630 V/cm.Oe is
achieved in PCMEU with two Metglas bars (n = 2). The ME voltage coefficient can be further enhanced by
integrating m of these optimal PCMEUs in series to form a serial-parallel ME unit array m-S (n-PMEU)A.
The aE value increases by a factor of 3.6 and reaches 2.238 kV/cm.Oe for 4-S (2-PMEU)A, a factor that is
almost equal to m. The resulting 4-S (2-PMEU)A sensor possesses an extremely high sensitivity of
18.1 mV/nT, with a resolution of 10�1 nT.
Dinh Cuong Trinh
Viet Hung Nguyen
viethung1996vn@gmail.com
Le Ha Vu
Anh Tuan Phung
Dinh Duong Do
Anh Tam Ho
hoanhtam@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2020-11-30T07:03:26Z
2020-11-30T07:03:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4088
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4088
2020-11-30T07:03:26Z
Magnetoelectric Vortex Magnetic Field Sensors Based
on the Metglas/PZT Laminates
This paper describes the route, from simulations toward experiments, for optimizing the
magnetoelectric (ME) geometries for vortex magnetic field sensors. The research is performed on the
base of the Metglas/Piezoelectric (PZT) laminates in both open and closed magnetic circuit (OMC and
CMC) geometries with di�erent widths (W), lengths (L), and diameters (D). Among these geometries,
the CMC laminates demonstrate advantages not only in their magnetic flux distribution, but also in
their sensitivity and in their independence of the position of the vortex center. In addition, the ME
voltage signal is found to be enhanced by increasing the magnetostrictive volume fraction. Optimal
issues are incorporated to realize a CMC-based ME double sandwich current sensor in the ring shape
with D � W = 6 mm � 1.5 mm and four layers of Metglas. At the resonant frequency of 174.4 kHz,
this sensor exhibits the record sensitivity of 5.426 V/A as compared to variety of devices such as the
CMC ME sensor family, fluxgate, magnetoresistive, and Hall-e�ect-based devices. It opens a potential
to commercialize a new generation of ME-based current and (or) vortex magnetic sensors.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Anh Tam Ho
hoanhtam@vnu.edu.vn
Thi Ngoc Khanh Vu
Trong Vinh Nguyen
Anh Tuan Phung
Van Tuan Nguyen
Thi Ngoc Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
2020-07-29T08:16:59Z
2020-07-29T08:16:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4035
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/4035
2020-07-29T08:16:59Z
Nanomaterials for Organic Optoelectronic Devices: Organic Light-Emitting Diodes, Organics Solar Cells and Organic Gas Sensors
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Si Trong Khanh Tran
Minh Long Lam
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2020-07-18T01:57:55Z
2020-07-18T01:57:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3975
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2020-07-18T01:57:55Z
Characteristics of Zn1-xAlxO NR/ITO Composite Films Oriented Application for Optoelectronic Devices
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2020-07-18T01:57:08Z
2020-07-18T01:57:08Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3974
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3974
2020-07-18T01:57:08Z
Modelling and numerical analysis of ZnO/CuO/Cu2O heterojunction solar cell using SCAPS
In this work, the SCAPS-1D program was utilized to perform simulations of ZnO/CuO/Cu2O thin-film solar cells. Based on the cell structure and device fabrication process, solar cell structureparameters such as the thickness of the CuO layer, ZnO layer, donor density in the ZnO layer wereevaluated in detail. The results indicated that an optimal structure of ZnO/CuO/Cu2O thin-film solarcell could be obtained when the thickness of the ZnO layer, CuO layer, and donor density in the ZnOlayer is 100 nm, 500 nm, 1×1017cm−3, respectively. The optimized solar cell structure ofZnO/CuO/Cu2O shows a potential efficiency of about 12% under the 1 sun air mass 1.5 G spectrumillumination. Besides that, the performance of the cell under individual solar concentrations andoperating temperatures was also investigated
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2019-12-30T03:20:41Z
2019-12-30T03:21:02Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3914
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2019-12-30T03:20:41Z
NGHIÊN CỨU XÂY DỰNG HỆ THỐNG CÁC MODULE ĐIỀU KHIỂN CHIẾU SÁNG TÍCH HỢP KIỂM SOÁT TRÊN ĐIỆN THOẠI THÔNG MINH
Việc phát triển kết nối mạng và thiết bị phổ biến mọi nơi đang tạo ra một làn sóng thiết bị thông minh mới với thiết bị điện tử cảm biến và kết nối không dây có thể thu thập, xử lý và trao đổi dữ liệu. Thường được gọi là Vạn vật kết nối (IoT), không giới hạn ở các mạng cảm biến không dây, tự động hóa gia đình, thiết bị di động và hệ thống điều khiển ánh sáng. Hệ thống chiếu sáng thông minh được đặc biệt quan tâm khi chúng phát triển từ điều khiển chiếu sáng truyền thống tới điều khiển ánh sáng tự động thông qua phản hồi từ cảm biến tích hợp, dữ liệu người dùng, dịch vụ đám mây và đầu vào của người dùng, mang lại nhiều lợi ích bao gồm lợi ích tiết kiệm năng lượng, tăng cường chức năng, và ánh sáng lấy người dùng làm trung tâm. Nghiên cứu này, xem xét hiện trạng của công nghệ chiếu sáng thông minh, tập trung vào các hệ thống chiếu sáng thông minh tiết kiệm năng lượng. Hơn nữa, nghiên cứu cũng trình bày một đánh giá về các tùy chọn kết nối ánh sáng thông minh và thảo luận về những tiến bộ tiềm năng thông qua việc tích hợp công nghệ điều khiển hệ công suất cũng như quản lí hệ thống đèn chiếu sáng ứng dụng trong chiếu sáng của gia đình. Kết quả nghiên cứu đã thiết kế và thử nghiệm thành công panel Led và mạch điều khiển công suất . Nguồn cấp cho mạch 220(V) xoay chiều mạch điều khiển điện áp trong dải 12-180(V) với mỗi dòng cấp cho Led ổn định là 350(mA). Ngoài ra từ kết quả này sẽ đóng góp một phần đáng kể cho việc ứng dụng và làm chủ công nghệ trong chiếu sáng cũng như tiết kiệm năng lượng.
Thanh Tung Nguyễn
tungng.ies@gmail.com
2019-12-30T03:19:49Z
2019-12-30T03:19:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3915
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3915
2019-12-30T03:19:49Z
Light Intensity-dependent Variation in Defect Contributions to Charge Transport and Recombination in a Planar MAPbI3 Perovskite Solar Cell
We investigated operation of a planar MAPbI3 solar cell with respect to intensity variation ranging from 0.01 to 1 sun. Measured J-V curves consisted of space-charge-limited currents (SCLC) in a drift-dominant range and diode-like currents in a diffusion-dominant range. The variation of power-law exponent of SCLC showed that charge trapping by defects diminished as intensity increased, and that drift currents became eventually almost ohmic. Diode-like currents were analysed using a modified Shockley-equation model, the validity of which was confirmed by comparing measured and estimated open-circuit voltages. Intensity dependence of ideality factor led us to the conclusion that there were two other types of defects that contributed mostly as recombination centers. At low intensities, monomolecular recombination occurred due to one of these defects in addition to bimolecular recombination to result in the ideality factor of ~1.7. However, at high intensities, another type of defect not only took over monomolecular recombination, but also dominated bimolecular recombination to result in the ideality factor of ~2.0. These ideality-factor values were consistent with those representing the intensity dependence of loss-current ratio estimated by using a constant internal-quantum-efficiency approximation. The presence of multiple types of defects was corroborated by findings from equivalent-circuit analysis of impedance spectra.
Shinyoung Ryu
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
Na Young Ha
Hui Joon Park
huijoon@ajou.ac.kr
Y. H. Ahn
Ji-Yong Park
jiyong@ajou.ac.kr
Soonil Lee
soonil@ajou.ac.kr
2019-12-26T10:58:19Z
2019-12-26T10:58:33Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3904
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3904
2019-12-26T10:58:19Z
Hệ thống hỗ trợ ra quyết định quản lý tổng hợp tài nguyên nước: Thử nghiệm phân tích quản lý đập Đakmi 4
The Ba Dang
badt@vnu.edu.vn
2019-12-24T04:45:51Z
2019-12-24T04:45:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3871
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3871
2019-12-24T04:45:51Z
Hệ thống báo cháy nhanh qua internet sử dụng giao thức truyền dữ liệu hai chiều (websocket).
In recent years, along with the general development of economy and society, the
situation of fire and explosion has also occurred more and more complicatedly. There are
many solutions to minimize the damage of fire, one of which is to improve the efficiency of
receiving and sending fire alarms. Many companies and researcher have developed fire
alarm systems from central fire alarm box via the internet to firefighting office, but the
above solutions have some disadvantages such as: delay in sending fire alarms, high cost,
complicated use process for soldiers who receive fire alarms…. This research proposes a
solution to design and develop fire alarm system via the Internet using Websocket protocol.
Websocket is a new protocol that has many advantages such as: high speed, low data
transmission, easy programming, deployment and good security. This research also uses
Android phones as communication devices, this is a new ideal, which can help users to be
proactive in selecting devices and reducing product costs. In addition, the research also
develop the fire alarm management with many features, aiming to deploy a comprehensive
and comprehensive system on the whole country
Nguyen Thuc Vu
thucvn@vnu.edu.vn
2019-12-24T04:45:18Z
2019-12-24T04:45:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3869
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3869
2019-12-24T04:45:18Z
THIẾT KẾ VÀ XÂY DỰNG HỆ THỐNG BÁO CHÁY NHANH QUA INTERNET
SỬ DỤNG GIAO THỨC WEBSOCKET
DESIGN AND DEVELOP QUICK FIRE ALARM SYSTEM ON INTERNET BY
USING WEBSOCKET PROTOCOL
Trong những năm qua cùng với sự phát triển chung của kinh tế, xã hội thì tình hình
cháy nổ cũng xảy ra nhiều hơn và có diễn biến ngày càng phức tạp. Có nhiều giải pháp để
hạn chế tối đa những thiệt hại do cháy nổ ra gây ra, một trong số đó là nâng cao hiệu quả
của việc tiếp nhận và gửi tin báo cháy. Nhiều nhà nghiên cứu và công ty đã phát triển các
hệ thống truyền tin báo cháy từ tủ trung tâm qua mạng internet đến trung tâm tiếp nhận tin
báo cháy của cảnh sát Phòng cháy chữa cháy và cứu hộ cứu nạn (PCCC & CNCH). Tuy
nhiên, các giải pháp trên vẫn còn những nhược điểm như: có độ trễ khi gửi tin báo cháy qua
internet, chi phí cao, quá trình sử dụng còn phức tạp với cán bộ chiến sĩ tiếp nhận tin báo
cháy…. Nghiên cứu này đề xuất giải pháp thiết kế và xây dựng hệ thống báo cháy nhanh
qua internet bằng giao thức Websocket. Websocket là giao thức mới được phát triển có
nhiều ưu điểm như: tốc độ nhanh, dữ liệu truyền ít, dễ lập trình, triển khai và bảo mật tốt.
Nghiên cứu này cũng sử dụng điện thoại Android làm thiết bị truyền tin. Đây là hướng đi
mới, có thể giúp người dùng chủ động trong việc lựa chọn thiết bị và giảm giá thành sản
phẩm. Ngoài ra, nghiên cứu cũng xây dựng hệ thống quản lý và tiếp nhận tin báo cháy với
nhiều tính năng vượt trội hướng đến triển khai hệ thống đồng bộ, toàn diện trên địa bản cả
nước.
Nguyen Thuc Vu
thucvn@vnu.edu.vn
Tuan Tu Dang
2019-12-24T04:41:28Z
2019-12-24T04:54:29Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3849
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3849
2019-12-24T04:41:28Z
Ứng dụng và phát triển của pin nhiên liệu
Thi Ngoc Anh Mai
anhmtn@vnu.edu.vn
2019-12-24T04:39:03Z
2020-12-23T03:14:41Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3857
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3857
2019-12-24T04:39:03Z
STRUCTURAL, MAGNETIC AND ELECTRICAL PROPERTIES
OF Ho AND Ni CO-DOPED BiFeO3 MATERIALS
Pure BiFeO3 (BFO) and Bi1-xHoxFe0.97Ni0.03O3 (x = 0, 0.025, 0.05, 0.075, and 0.1)
materials were synthesized by a sol-gel method. The influence of (Ho, Ni) co-doping on structural,
magnetic and electrical properties of BFO materials were investigated by different techniques as
X-ray diffraction (XRD), energy dispersion X-ray (EDX), Raman scattering, magnetic hysteresis
(M-H) loops, and complex impedance spectra measurement. XRD results showed that all samples
were crystallized in the rhombohedral structure with R3C space group. Crystal lattice parameters
(a, c) and average crystal size LXRD were (a = 5.584 Å, c = 13.867 Å, LXRD = 60 nm) for pure BFO,
(a = 5.589 Å, c = 13.875 Å, LXRD = 60 nm) for BiFe0.97Ni0.03O3 sample, and then decreased with
increasing of Ho content in (Ho, Ni) co-doped samples. Similarly, Raman scattering spectra
showed the left shift of active modes Fe-O bonds when doping Ni and right shift when co-doping
Ho. These observations confirmed the successful substitution of Ho3+ and Ni2+ ions into the host
BFO crystal lattice. Magnetic hysteresis loops measurement indicated that all samples exhibited
weak ferromagnetic behavior with saturation magnetization Ms and remnant magnetization Mr of
(Ms ~ 0.047 emu/g, Mr ~ 0.008 emu/g) for pure BFO which increased gradually for (Ho, Ni) codoped samples, reached to (Ms ~ 0.702 emu/g, Mr ~ 0.169 emu/g) for x = 0 sample. Origin of the
enhancement of ferromagnetization in (Ho, Ni) co-doped samples have been discussed
Dinh Tu Bui
buidinhtu@vnu.edu.vn
2019-12-20T04:40:18Z
2019-12-20T04:46:38Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3809
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3809
2019-12-20T04:40:18Z
Influences of growth durations on characteristics of NaYF4:(Yb,Tm) upconversion materials
NaYF4:(Yb,Tm) upconversion materials were synthesized by the simple hydrothermal method. Growth duration was varied from 4h to 12h under a growth temperature of 150oC. The structural, optical and surface morphology characteristics of the NaYF4:(Yb,Tm) UC materials were investigated. The XRD and SEM results illustrated that the NaYF4:(Yb,Tm) materials were transformed from the multiple phases (hexagonal and cubic) to the single-phase (hexagonal prism) as growth duration being longer than 8h with the average diameter and length of these prisms being about 0.5 µm and 2 µm, respectively. Under 980 nm laser excitation, the NaYF4:(Yb,Tm) emits at peaks of 450 nm (1D2→ 3F4), 475 nm (1G4→3H6), 647 nm (1G4→3F4) and 697 nm (3F3→3H6), with the highest emission belonging to NaYF4:(Yb,Tm) grown for 8h.
Thi Dung Nguyen
Dung.nguyenthi.tunhien@gmail.com
Van Thanh Hoang
Dinh Lam Nguyen
lamnd2005@gmail.com
2019-12-20T04:36:56Z
2019-12-20T04:37:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3778
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3778
2019-12-20T04:36:56Z
Comparative study of three MPPT methods for Photovoltaic systems
In order to ensure that the photovoltaic (PV) module always operates at the maximum power point for any weather conditions, a maximum power point tracking (MPPT) system is indispensable. This paper presents a comparative analysis of three methods MPPT: Perturb and observe (P&O), Fuzzy Logic Controller (FLC) and Backstepping Controller. The parameters considered for the comparison are the performance of these MPPTs such as the extracted power from the PV system, steady and dynamic response of the system under various conditions like changing solar irradiance or temperature. Simulations results, obtained by using MATLAB/Simulink, shown that the MPPT controller based on the Backstepping technique is the most robust controller under changing conditions.
Cong Hung Tran
tchung@vnu.edu.vn
2019-12-12T10:59:58Z
2019-12-20T04:45:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3592
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2019-12-12T10:59:58Z
LIGHT ABSORPTION AND PHOTOLUMINESCENCE QUENCHING
PROPERTIES OF BULK HETEROJUNCTION MATERIALS BASED ON THE
BLEND OF POLY(N-VINYLCARBAZOLE)/POLY(N-HEXYLTHIOPHENE)
Abstract. The enhancement of light absorption and photoluminescence quenching properties
of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK);
poly(N-hexylthiophene) (P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-
[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the
region from ultra violet to near infra-red and the photoluminescence quenching higher than 90%.
The obtained results provide further insight into photophysics of the heterojunction system and
device performance improvement by using this system as an active layer.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Nang Dinh Nguyen
nndinh@vnu.edu.vn
Dinh Long Phan
2019-12-12T09:42:23Z
2019-12-12T11:02:40Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3596
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3596
2019-12-12T09:42:23Z
Enhanced hardness of nickel coating reinforced functionalized
carbon nanomaterials via an electrodeposition technique
In this paper, the nickel (Ni) coatings reinforced carbon nanomaterials including graphene
nanoplatelets (GNPs), multi-walled carbon nanotubes (MWCNTs) andMWCNTs/GNPs hybrid
material prepared by the electrodeposition technique were investigated. GNPs andMWCNTswere
functionalized with carboxylic (–COOH) function groups (GNPs–COOH,MWCNTs–COOH) then
uniformly dispersed into Watts solution for the electrodeposition process. The obtained results
revealed that the microhardness of the Ni coating reinforcedCOOHfunctionalized carbon
nanomaterials is much improved compared to the bare Ni coating and Ni coating containing carbon
nanomaterials without functional groups. The Ni coating containingMWCNTs–COOH/GNPs–
COOHhybrid material showed the highest hardness value of 270HVthat is higher 44.7% compared
to the bare Ni coating. The enhancement was attributed to the uniform dispersion of functionalized
carbon nanomaterials in Ni matrix, the synergistic strengthening effect of theMWCNTsand GNPs,
the grain refinement of Ni matrix and the enhanced load transfer effect from Ni matrix toMWCNTs
and GNPs via atomic bonding during the electrodeposition process.
Van Hau Tran
Van Trinh Phan
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Dinhh Lam Vu
Ngoc Minh Phan
Hung Thang Bui
thangbh@ims.vast.vn
2019-12-10T03:37:57Z
2019-12-10T03:37:57Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3660
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3660
2019-12-10T03:37:57Z
CẢM BIẾN ĐIỆN HÓA SỬ DỤNG ĐIỆN CỰC La0.8Sr0.2MnO3 ĐO KHÍ O2 NHẰM ỨNG DỤNG CHO ĐIỀU KHIỂN ĐỐT CHÁY NHIÊN LIỆU
Cảm biến khí đo O2 kiểu điện hóa hoạt động nhiệt độ cao được ứng dụng phổ biến trong điều khiển phản hồi cho quá trình đốt cháy nhiên liệu của nhiều ngành công nghiệp. Cảm biến điện hóa đo khí O2 thương mại thông dụng có cấu trúc gồm lớp điện ly YSZ (ZrO2 pha tạp Y2O3) và hai điện cực kim loại Pt. Cảm biến loại này được thiết kế khi hoạt động với một điện cực Pt ở trong môi trường khí so sánh (biết trước nồng độ khí O2) và điện cực còn lại đặt trong môi trường khí cần xác định nồng độ khí O2. Hiện nay, các nhà nghiên cứu đang quan tâm phát triển loại cảm biến điện hóa có khả năng hoạt động trực tiếp trong môi trường khí cần xác định nồng độ O2 mà không cần thêm môi trường khí so sánh. Một cách tiếp cận được nghiên cứu phổ biến là một điện cực Pt được bổ sung thêm lớp đệm oxit kim loại nhằm khống chế sự khuếch tán khí O2 đến biên tiếp giáp “điện cực - chất điện ly” để tham gia phản ứng điện hóa, từ đó điều khiển được tín hiệu lối ra của cảm biến phụ thuộc tuyến tính vào nồng độ khí O2. Công trình này trình bày các kết quả nghiên cứu chế tạo cảm biến điện hóa với cấu hình Pt/YSZ/PtLa0.8Sr0.2MnO3-Pt và các đặc trưng nhạy khí. Tín hiệu lối ra của cảm biến thể hiện đáp ứng tốt và phụ thuộc tuyến tính vào nồng độ khí O2 trong dải từ 0 - 20% thể tích trong vùng nhiệt độ khảo sát từ 500 đến 800 oC.
Dinh Tuan Pham
tuanpd@vnu.edu.vn
2019-12-09T09:27:34Z
2019-12-09T09:27:34Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3758
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3758
2019-12-09T09:27:34Z
InGaP Nano-pattern Structure Realized by Thermally Dewetted Au Nanoparticles and Anisotropic Dry Etching
Abstract: Background: Optical reflection loss can be reduced more than 30% when multilayers ARC are deposited on the optoelectronic devices surface. Besides that, sub-wavelength structures, which have a period sufficiently smaller than the wavelength of light, have been introduced as an antireflection layer to offer a new possibility to suppress the Fresnel reflection. Normally, e-bean and nano-imprint lithography techniques are used to create nano-scale etch mask patterns. Metallic nanoparticles, which can be formed by a thermal dewetting process of metal thin film without any nanolithography techniques, can be utilized as an etch mask for the nano structure fabrications. The nano-patterned structures were fabricated on a silicon nitride passivation layer of a GaInP/GaAs/Ge triple-junction solar cell and showed an enhancement of its performance due to improved optical transmission and current matching.
Objective: Investigate the influences of InGaP nano-pattern structures on the optical characteristics and applied for compound solar cells. Methods: In this report, disordered InGaP nano-pattern structures were formed by thermally dewetted Au nanoparticles and anisotropic dry etching processes. The effects of the InGaP nano-patterned
structure on the optical reflection characteristics were investigated.
Results: The result indicated that the InGaP nano-patterned structure can reduce the optical reflection
in a wide range of wavelengths and, thus, can work as an antireflection layer. The InGaP nanostructure can improve up to 14.8% in the short circuit current density compared to that of the planar cell.
Conclusion: The InGaP nano structures have been successfully fabricated by thermal dewetted Au nanoparticles and anisotropic dry etching methods. The fabricated Au nanoparticles pattern was found to be the best when annealing temperature is 400°C for 30 minutes with the 5nm thick of Au film. By controlling dry etching time, the height of InGaP nanostructures can be varied from 95 nm to 150 nm. With the increasing of the height, the optical reflectance can be down to 22%. The InGaP nanostructure with the height of 150 nm was also introduced to the window layer of a single junction GaAs soar cell. The result indicated that the InGaP nanostructure only affects on the short circuit current density.
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2019-12-06T11:47:07Z
2019-12-06T11:47:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3627
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2019-12-06T11:47:07Z
Quy trình chế tạo kênh dẫn vi lưu sử dụng laze CO2 kết hợp với cơ cấu quét chùm tia bằng đầu lắc Galvo và đóng kín kênh bằng cách ép cơ học
Anh Tam Ho
hoanhtam@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Viet Hung Nguyen
viethung1996vn@gmail.com
2019-12-06T11:45:52Z
2019-12-09T03:46:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3690
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2019-12-06T11:45:52Z
Raman Signal Enhancement of Rhodamine 6G on Gold Nanoparticles for Detecting Chemical Residues
Chemical residues at lower than 10-4 M conc. has not usually been detected by a common Raman spectrometer. However, they can be detected at the lower 10-4 M conc., even up to of 10-9 M conc. when their deposition on a surface-enhanced Raman scattering (SERS) surface. In this paper, a SERS surface was prepared gold nano-particles (AuNPs) of 5nm diameter, synthesized from the HAuCl4 precursor and then was arranged as a SERS/AuNP- layer of 25nm in thickness. A Rhodamine 6G (Rh6G) dye-indicator, chosen as the SERS-probe molecules to detect the enhanced Raman amplitude, was diluted at different solution, ranging from 10-4 M to 10-9M conc. With the same 10-4 M conc. of Rh6G dye, typical Raman peaks of the Rh6G deposited on the AuNPs surface can be clearly detected while these peaks of Rh6G on a blank glass surface could not be seen. Even if, the Rh6G solution on the AuNP surface was diluted up to 10-9M conc. its typical peaks can be still detected clearly. The significant enhancement of the surface Raman signals at the different conc. of the Rh6G solution, deposited on AuNP surface, will be later discussed in the paper.
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2019-12-04T03:58:16Z
2019-12-04T03:58:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3628
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2019-12-04T03:58:16Z
Phương pháp tự động dò tìm và bắt bám vệ tinh địa tĩnh ứng dụng cho các trạm thu di động tín hiệu vệ tinh đặt trên các phương tiện di chuyển
Anh Tam Ho
hoanhtam@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Van Muoi Dang
Dinh Van Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
2019-11-29T05:23:05Z
2020-12-14T07:29:12Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3630
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3630
2019-11-29T05:23:05Z
Nghiên cứu khả năng sinh hoạt tính kháng khuẩn của vi nấm nội sinh cây Thạch tùng răng cưa (Huperzia serrata) phân bố tại Lâm Đồng - Việt Nam
Vi khuẩn kháng kháng sinh đang là mối quan tâm trên toàn cầu. Việt Nam là một trongcác nước có tỷ lệ kháng thuốc kháng sinh cao trên thế giới. Hướng tới việc tìm kiếm các hoạt chất, kháng sinh mới có nguồn gốc từ vi sinh vật nội sinh cây thảo dược, 45 chủng vi nấm nội sinh phân lập từ cây thảo dược Thạch tùng răng cưa phân bố tại lâm Đồng-Việt Nam được sàng lọc hoạt tính kháng 3 loại vi khuẩn kiểm định Escheria coli, Moraxella cataharrlis, Staphylococus aureus và nấm men Candida albicans. Hai mươi chín chủng nấm nội sinh có hoạt tính kháng khuẩn từ 1-4 loài vi sinh vật kiểm định được khảo sát, trong đó có 5 chủng cho khả năng ức chế cao đồng thời cả 4 lòai vi sinh vật kiểm định với đường kính vòng kháng khuẩn từ 16-36 mm. Bằng phương pháp định danh truyền thống và sinh học phân tử, 5 chủng vi nấm đã dược định danh là Trichoderma sp. TĐL1, Fusarium sp. TĐL1, Fungal endophyte sp. RĐL4, TĐL51 và LĐL15.
Thi Minh Thanh Le
minhthanh.ibt@gmail.com
Thi Hong Anh Nguyen
Van Quyen Dong
Thi Quyen Ha
quyenht@vnu.edu.vn
2019-11-29T03:43:50Z
2019-11-29T03:43:50Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3626
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3626
2019-11-29T03:43:50Z
Linh kiện cảm biến đo dòng điện và phương pháp chế tạo
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Anh Tam Ho
hoanhtam@vnu.edu.vn
2019-11-29T03:40:16Z
2019-12-20T04:32:54Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3597
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2019-11-29T03:40:16Z
ỨNG DỤNG PHƯƠNG PHÁP NGHIỀN BI NĂNG LƯỢNG CAO ĐỂ NÂNG
CAO HIỆU QUẢ PHÂN TÁN VẬT LIỆU GRAPHEN ĐA LỚP
TRONG CHẤT LỎNG
Độ ổn định phân tán vật liệu graphen trong chất lỏng đóng vai trò rất quan
trọng để nâng cao hiệu quả ứng dụng trong nhiều lĩnh vực, như trong chất lỏng
nano, vật liệu tổ hợp, lĩnh vực y sinh, …. Do kích thước của vật liệu graphen
ảnh hưởng lớn đến sự phân tán và độ ổn định của graphene, vì vậy chúng tôi
hướng đến cách tiếp cận rất mới là sử dụng phương pháp nghiền bi năng lượng
cao nhằm giảm kích thước và tăng diện tích bề mặt riêng cho vật liệu graphen
đa lớp (GNPs). Các phép đo bề mặt (FE-SEM), quang phổ raman, phổ hấp thụ
hồng ngoại FTIR, phép đo diện tích bề mặt riêng (BET) được sử dụng để đánh
giá các đặc tính vật liệu, khả năng phân tán và độ ổn định phân tán trong chất
lỏng của vật liệu GNPs sau khi nghiền. Kết quả nghiên cứu cho thấy nghiền bi
năng lượng cao là phương pháp rất hiệu quả để nâng cao khả năng phân tán và
độ ổn định của vật liệu GNPs trong chất lỏng, nghiên cứu chỉ ra rằng vật liệu
GNPs được nghiền với thời gian 5 giờ có kích thước 218 nm, diện tích bề mặt
196,63 m2/g tăng 555% so với vật liệu graphen ban đầu, cho độ ổn định phân
tán tốt nhất với thế zeta đo được là 29,2 mV.
Hung Thang Bui
thangbh@ims.vast.vn
Ngoc Minh Phan
pnminh@vast.vn
Van Hau Tran
Van Trinh Pham
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Thi Thanh Cao
Dinh Lam Vu
2019-11-29T03:38:21Z
2019-12-20T04:36:32Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3629
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2019-11-29T03:38:21Z
NGHIÊN CỨU CHẾ TẠO VÀ KHẢO SÁT HẠT CHITOSAN ĐỂ HẤP THỤ PHÂN ĐẠM URE
Trong các loại dưỡng chất thiết yếu cho cây trồng phân ure được sử dụng nhiều nhất trong số các loại phân đạm. Tuy nhiên, cây trồng chỉ hấp thụ được chỉ từ 30-40% lượng ure cung cấp do phân ure dễ bị phân hủy và rửa trôi trong đất gây lãng phí và ô nhiễm môi trường. Trong công trình này, nghiên cứu chế tạo hạt chitosan để hấp thụ và giải phóng ure. Hạt gel chitosan được chế tạo bằng cách bơm dung dịch chitosan vào dung dịch chất hoạt động bề mặt natri dodecyl sulphat (SDS) hoặc dung dịch muối Na¬2HPO4. Hạt gel chitosan tương ứng tạo thành có dạng hình cầu rỗng và hình cầu đặc với đường kính hạt gel phụ thuộc vào thể tích giọt dung dịch chitosan. Hạt chitosan mang phân đạm ure được tạo ra bằng cách ngâm các hạt gel chitosan trong dung dịch ure với các nồng độ khác nhau. Sự có mặt của ure trong hạt gel được khẳng định bằng phương pháp phổ hồng ngoại chuyển đổi chuỗi Fourier (FTIR). Ure được định lượng bằng phương pháp phổ hấp thụ UV-vis tại bước sóng 437 nm sử dụng thuốc thử 4-(Dimethylamino)benzaldehyde (DMAB). Thời gian để lượng ure hấp thụ tối đa vào hạt gel chitosan là 30 phút. Hạt chitosan đường kính 1mm được tạo bởi dung dịch SDS với khối lượng 30.3 mg/10 hạt có tỉ lệ phần trăm khối lượng ure lớn nhất, khoảng 96%.
Thi Hien Le
lehien@vnu.edu.vn
Van Dung Do
dodunguet@gmail.com
2019-11-28T09:01:47Z
2019-11-29T05:48:15Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3587
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2019-11-28T09:01:47Z
High thermoelectric power factor in SnSe2 thin film grown on Al2O3 substrate
Thermoelectric figure of merit (ZT) is highly sensitive to the carrier concentration and maximizes within the narrow region of 1019–1020 cm−3. The SnSe2 single crystal is predicted to have a high ZT value with carrier concentration in the range of 1019–1020 cm−3. Here, we grew SnSe2 thin film on Al2O3 substrate by pulsed laser deposition (PLD) with post-annealing at 400 °C in Argon for 60 min. The annealed thin film shows a high thermoelectric power factor up to 8 μW cm−1 K−2 at 220 K with a carrier concentration of 5.2 × 1019 cm−3. A hexagonal crystal structure of the SnSe2 thin film was confirmed by X-ray diffraction and Raman spectra measurements. The thin film showed an n-type semiconductor behavior. Maximum electrical conductivity and Seebeck coefficient were obtained at 220 K with the values of 210 Scm−1 and −192 μVK−1, respectively.
Anh Tuan Duong
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
Manh Nghia Nguyen
Thi Minh Hai Nguen
Anh Duc Nguyen
Anh Tuan Pham
Parman Ullah
Tahir Zeeshan
Yong Soo Kim
Quang Trung Do
Tu Nguyen
Van Hao Bui
Das Raja
Thanh Huy Pham
Sunglae Cho
2019-11-28T09:00:47Z
2019-11-29T05:54:54Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3560
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2019-11-28T09:00:47Z
Influences of PbS quantum dot layers on power conversion efficiency of single junction GaAs solar cells
PbS quantum dots were coated on the surface of single junction GaAs solar cells by a drop coating method. The thickness of PbS quantum dot layer was controlled through changing the number of coating layers. The influences of PbS coating layers on characteristics of GaAs single junction solar cells were investigated through I-V characteristic measurements, optical reflectance spectra, and quantum efficiencies. The results indicated that, the short-circuit current can be improved up to 15% with two PbS coating layers. Other parameters such as Voc and FF are hardly affected by the number of PbS coating layers. Based on the results of optical reflectance spectra and quantum efficiencies, the enhancement in the short-circuit current can be attributed to the antireflection of the PbS layers and the ability to transfer high energy photon-generated charge carriers.
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2019-11-28T01:47:40Z
2019-11-28T01:49:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3616
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2019-11-28T01:47:40Z
LIGHT ABSORPTION AND PHOTOLUMINESCENCE QUENCHING
PROPERTIES OF BULK HETEROJUNCTION MATERIALS BASED ON THE
BLEND OF POLY(N-VINYLCARBAZOLE)/POLY(N-HEXYLTHIOPHENE)
The enhancement of light absorption and photoluminescence quenching properties
of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK);
poly(N-hexylthiophene) (P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-
[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the
region from ultra violet to near infra-red and the photoluminescence quenching higher than 90%.
The obtained results provide further insight into photophysics of the heterojunction system and
device performance improvement by using this system as an active layer.
Dinh Long Phan
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2019-11-27T07:06:06Z
2019-11-27T07:06:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3406
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2019-11-27T07:06:06Z
Enhanced magneto-transport and thermoelectric properties of MnP nanorod thin flms grown on Si (1 0 0)
The MnP thin flms were grown on Si (1 0 0) substrates at 300 and 400 °C using molecular beam epitaxy (MBE). The flms crystallize in an orthorhombic structure. FESEM images indicated that both flms are composed of vertically aligned MnP nanorods. However, the density of the nanorods in the flm grown at 400 °C is higher
than that grown at 300 °C, leading to a considerable decrease of resistivity in this sample. Both flms showed a ferromagnetic behavior, but the Curie temperature
increased from 275 K for the flm grown at 300 °C to 325 K for the flm grown at 400 °C. Anomalous Hall effect (AHE) and negative magneto-resistance (MR) were
observed in the flms. While both flms exhibited a metallic behavior, a higher thermoelectric power factor (PF) was achieved for the flm grown at 400 °C
Anh Tuan Duong
Thi Minh Hai Nguyen
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
Das Raja
Huu Tuan Nguyen
Bach Thang Phan
Sunglae Cho
2019-11-27T06:57:06Z
2019-11-27T06:57:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3618
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2019-11-27T06:57:06Z
Lagrangian Vortex Particle Method for Complex Flow Simulation
In order to solve complicated simulation problem for complex deforming objects under complicated motions found in aerospace, aerodynamic, meteorology, biology engineering, this paper presents Lagrangian vortex method based on Brinkman penalization. The Brinkman penalization acts as an external force, which is implicitly enforced into Navier-Stokes equation in the velocity-vorticity form. The advantage of the method is the capability to remove the pressure factor which causes errors in other numerical methods due to the complexity of shape of the object. Furthermore, the method is able to model the complex geometry, complex motions as well as 3D deformation of the object. In particular, the Navier-stokes equation can be solved in a classical strategy: applying Bio-Savart law formula is to deal with the convection process; employing fast multipole method to accelerate the velocity computation. The convergence is verified in several simulation applications such as air flow over low aspect ratio wing, rotation wings, influent of wind gust on high-raised building, and fish swimming.
Viet Dung Duong
duongdv@vnu.edu.vn
Zuhal Lavi Rizki
Muhammad Hari
2019-10-22T07:17:39Z
2019-10-22T07:17:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3579
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2019-10-22T07:17:39Z
Optical simulation of planar CH3NH3PbI3 perovskite solar cells
In this work, optical simulation results of planar CH3NH3PbI3 solar cells using a MATLAB script developed by McGehee’s group (Stanford University) are presented. The device structure is of FTO/HEL/AL/ETL/LiF/Al, where HEL is the hole-extraction layer, AL is the active layer (CH3NH3PbI3), and EEL is the electron-extraction layer. In this MATLAB script, the transfer matrix method was used, where transmission and reflection were calculated for each interface in the stack as well as attenuation in each layer. The wavelength-dependent optical constants (n and k) of each layer were measured by spectroscopic ellipsometry (SE). The exciton generation rates within the active layer were calculated based on data of optical constants, as well as the thickness of each layer. Considering the Internal Quantum Efficiency (IQE) equal to 100% at all wavelengths, the predicted short-circuit currents (JSC) were also estimated. The obtained results show a good agreement with the experimental values of JSC measured on real devices.
Keywords: planar solar cells, CH3NH3PbI3 perovskite, optical simulations, spectroscopic ellipsometry.
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
2019-10-01T03:02:40Z
2019-10-01T03:02:40Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3536
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2019-10-01T03:02:40Z
Khảo sát tính chất quang & cơ tính của ống đồng (Cu) sản xuất trên dây chuyền công nghiệp
Ống đồng được chế tạo tại nhà máy ống đồng Toàn Phát (Việt nam) trên dây chuyền công nghiệp có mức độ tự động hóa cao. Ống đồng có các kích thước khác nhau theo yêu cầu của thực tế được khảo sát theo đổi màu ống (tính chất quang) do quá trình oxy hóa khử (REDOX), độ bền giãn đứt, độ cứng bề mặt, kích thước hạt…Kết quả nghiên cứu cho thấy cơ tính: độ bền giãn đứt, độ giãn đứt giảm và kích thước hạt tăng, độ sáng của ống đồng tăng đáp ứng yêu cầu chất lượng theo tiêu chuẩn qui định.
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2019-08-21T03:37:07Z
2019-08-21T03:37:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3543
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3543
2019-08-21T03:37:07Z
Effect of Crystallization Temperature on Energy-Storage Density and Efficiency of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Thin Films Prepared by Sol-Gel Method
Dang Co Nguyen
nguyendangco.95@gmail.com
Viet Cuong Le
cuonglv@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Xuan Dien Luong
Ngoc Hung Vu
Duc Quan Ngo
2019-07-05T03:10:53Z
2019-07-05T03:10:53Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3538
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3538
2019-07-05T03:10:53Z
Effect of Crystallization Temperature on Energy-Storage Density and Efficiency of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Thin Films Prepared by Sol-Gel Method
Lead-free Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT) ferroelectric films were synthesized on Pt/Ti/SiO2/Si substrates via the chemical solution deposition. The influence of the crystallization temperature on the microstructures, the ferroelectric and energy-storage properties of the films was investigated in detail. The results showed that the BNKT films have reached the well crystallized state in the single-phase perovskite structure at 700oC. Ferroelectric and energystorage properties of the films were significantly enhanced by increasing the crystallization
temperature. The remnant polarization (2Pr) and maximum polarization (2Pm) reached the highest values of 18.4 µC/cm2 and 61.2 µC/cm2, respectively, under the electric field of 300 kV/cm. Thanks to the strong enhancement in 2Pm and the large Pmax - Pr value, the highest energy-storage density (Jreco) and efficiency of 2.3 J/cm3 and 58.2%, respectively, were obtained. These results indicate that the BNKT films have application potentials in advanced
capacitors.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Dang Co Nguyen
nguyendangco.95@gmail.com
Viet Cuong Le
cuonglv@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
2019-07-05T03:09:24Z
2019-07-05T03:09:24Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3495
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2019-07-05T03:09:24Z
LIGHT ABSORPTION AND PHOTOLUMINESCENCE QUENCHING
PROPERTIES OF BULK HETEROJUNCTION MATERIALS BASED ON THE
BLEND OF POLY(N-VINYLCARBAZOLE)/POLY(N-HEXYLTHIOPHENE)
The enhancement of light absorption and photoluminescence quenching properties
of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK);
poly(N-hexylthiophene) (P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-
[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the
region from ultra violet to near infra-red and the photoluminescence quenching higher than 90%.
The obtained results provide further insight into photophysics of the heterojunction system and
device performance improvement by using this system as an active layer.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Dinh Long Phan
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2019-07-05T01:40:55Z
2019-07-05T01:40:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3541
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3541
2019-07-05T01:40:55Z
Simple planar Hall effect based sensors for
low-magnetic field detection
Magnetic field sensors based on the planar Hall effect using single layer Ni80Fe20 thin films have
been designed, fabricated and characterized. By optimizing the sensor’s dimension, such as the
thickness and the length to width ratio, experimental results have shown that the sensor’s
sensitivity could be increased up to three times thanks to the enhancement of the shape magnetic anisotropy. The highest sensitivity of 100 μV Oe−1 corresponding to the relative resistance change up to 20 mΩ/Oe was achieved at a supplied DC current of 5 mA for the cross-shaped geometry of the sensor with 5 nm in the thickness and a length/width ratio of 10. Simple structure, low fabrication cost, and low power consumption make this sensor very promising for
low field magnetic field sensing such as geomagnetic field detections.
Khac Quynh Le
The Hien Nguyen
thehien@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2019-06-20T22:40:12Z
2019-06-24T06:45:13Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3516
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3516
2019-06-20T22:40:12Z
Resonator for magnetic sensor applications based on the magnetoelectric thin film integrated on Si
Magnetoelectric (ME)-based sensors have been demonstrated as a promising alternative for the magnetic field detection with high sensitivity on the order of a few tens of nanoteslas [1,2]. To date, most applications focus on laminated composites of using bulk piezoelectric (PZT) materials, which is a critical limit for miniaturizinginto micrometer-sized devices.This work shows the first attempts of a resonator based on multi-ferroic PZT/TbFeCo multilayers, where magnetic signal was very sensed by the shift of the resonant frequency. In this device, TbFeCo layer acts as a micro-actuator, while the PZT thin film as a micro-sensor. In magnetic field range less than 0.2 T, the sensor’s sensitivity as high as 250 Hz/T and 487 Hz/T were achieved in vacuum environments of … and 5 mbar, respectively). A smaller size and lower power consumption provide a significant advantages in terms of micro-ME-sensors for sensing magnetic field.
Thi Ngoc Nguyen
G. Agnus
S. Matzen
T. Maroutian
Thi Huong Giang Do
giangdth@vnu.edu.vn
P. Lecoeur
2019-06-20T22:39:58Z
2019-06-24T06:45:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3515
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3515
2019-06-20T22:39:58Z
Design, simulation and fabrication of a high sensitivity micro-magnetometer integrated with microfluidics system and flux concentrators for biomedical applications
Biomagnetism is the phenomenon of magnetic fields emitted by living organisms including cells. Magnetic field strength produced by cells or even with cells marked by magnetism (called biomarkers) are generally very weak. For this reason, cells/biomarkers (bio-samples) detection usually were done by directly contacting the bio-samples with sensor surface that would cause to degradation of sensor performance after some measurements. To deal with such situation, using an annular-shaped flux concentrator made by a high magnetic permeability material to increase magnetic amplification in sensor’s surface is necessary. Beside, this solution also supports for the measurement without contact. In this paper, we describes the results in design, simulation and fabrication of a high sensitivity micro-magnetometer integrated with microfluidics system and flux concentrators for biomedical applications (Fig. 1a). From simulation toward experiment, the results showed that by using the optimal annular-shaped flux concentrator to focus flux lines on sensor’s surface, the sensor signals is more than ten times higher than in the case directly contact method (Fig. 1b). The system opens up the potential for widespread use in lab-on-a-chip for biomedical applications and commercialization
Anh Tam Ho
hoanhtam@vnu.edu.vn
Van Hung Nguyen
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Kim CheoGi
2019-06-20T22:39:49Z
2019-06-24T06:43:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3514
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3514
2019-06-20T22:39:49Z
High sensitivity marine electronic compass equipment based on magnetoelectric effect of magnetostriction-piezoelectric composites
A novel marine electronic compass devices has been developed by integrating magnetoelectric geomagnetic sensors. The 1-D single sensors were fabricated using laminated composites of soft magnetic Ni-based Metglas ribbons and piezoelectric plate. The compass device consists of two 1-D single sensors in an orthogonal arrangement that permit to determine the angle respect to the magnetic North (Azimuth angle) by simultaneously measuring two components of geomagnetic field in horizontal plane. The investigations were performed by modelling and theory calculating for optimizing configuration, size and shape of single sensor element as well as optimizing noise floor in orthogonal assembly. With extremely high sensitivity (~ 1 V/Oe) and resolution magnetic field (~ nT) thanks to the enhancement of magnetic softness and uniaxial magnetic anisotropy, a highly sensitive angular sensor was successfully investigated and manufactured. Based on sensor working principles, an electronics circuit was developed, designed, assembled and packaged. The algorithms included auto-offset compensation, orthogonal error estimate, auto-calibration and Azimuth angle calculation were built that enables precisely measure angular position with a high sensitivity of 0.1 degree. This investigated high sensitivities but low-cost instrument are comparable with current commercial products
Anh Tuan Phung
Van Tuan Nguyen
Ba Bien Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2019-06-20T22:39:00Z
2019-06-24T06:46:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3513
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2019-06-20T22:39:00Z
Closed magnetic circuit magnetoelectric composites for extremely high sensitivity and electromechanical resonances controllable current sensor
Many assiduous researches have been taken into account by improving the increasing the soft intrinsic magnetic susceptibility of ribbon ferromagnetic phase or optimizing shape and size as well as piezoelectric/magnetostrictive volume ratio. All of these efforts lead to abate the demagnetization field. This paper describes from simulation toward experiment to find out the most effective method for enhancing magnetoelectric effect (ME) in current sensing applications. By using ring-shape magnetoelectric composites, many advantages were found includes: (i) enhance of the magnetic field concentration and (ii) eliminate impact of demagnetization field between magnetic layers thanks to closed magnetic circuit; (iii) easy to tune electromechanical resonances; and (iv) independent of the distance from the current-carrying cable. Indeed, it shows a variable resonant frequency from 20 to kHz 175 kHz depending on the size and structuce. An excellent linearly and an extremely high current sensitivity ~ 10 V/A was achieved in the Metglas/PZT/Metglas penta-layered laminates. Compared with the other close-magnetic-circuit-type current sensor topologies reported, this sensitivity is several hundred times higher. This sensor has great potential for further current sensing applications.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Trong Vinh Nguyen
Thi Ngoc Khanh Vu
Anh Tam Ho
Anh Tuan Phung
Huu Duc Nguyen
ducnh@vnu.edu.vn
2019-06-03T04:19:45Z
2019-06-03T04:19:45Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3451
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3451
2019-06-03T04:19:45Z
Characterization of performance parameters of organic solar cells with a buffer ZnO layer
By embedding a thin ZnO layer sandwiched between the hole transport and photoactive layers, organic solar cells (OSC) based on poly(3-hexylthiophene) (P3HT) were prepared by spincoating. UV-Vis spectra of the composite films showed that ZnO exhibited a suitable buffer layer that could block holes movement throughout the heterojunction of ITO/ZnO. The enhancement in the fill factor (FF) of the buffer-OSC (BOSC) is attributed to the presence of nanoheterojunctions of ZnO/PCBM and ZnO/ITO. For the normal temperature, the increase of the open-circuit potential and short-circuit current resulted in an overall increase of the energy conversion efficiency. Comparing to OSCs without buffer layer (WOSC), the laminar structure of ITO/ZnO/P3HT/PCBM/Li/Al cells possess a much larger photovoltaic energy conversion efficiency, namely 2.12% (for BOSC) compared to 1.75% (for WOSC).
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Hyung-Kook Kim
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
Duc Cuong Nguyen
cuongnd@vnu.edu.vn
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2019-01-07T03:14:44Z
2019-01-07T03:14:44Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3399
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3399
2019-01-07T03:14:44Z
Nanometer-scale local probing of X-ray absorption spectra of Co/Pt multilayer film
We report our local X-ray absorption spectra (XAS) measurement mapping for a Co/Pt multilayer using
scanning transmission microscopy with 25-nm spatial resolution and 0.1-eV spectral resolution. We have
systematically analyzed the two-dimensional XAS intensity variation over the corresponding magnetic domain
patterns, revealing a XAS profile across the magnetic domain wall as well as the simultaneous high-throughput
measurement of local XAS spectra.
Duy Truong Quach
Duc Thang Pham
pdthang@vnu.edu.vn
Djati Hankodo
Je-Ho Shim
Dong Eon Kim
Kyung-Min Lee
Jong-Ryul Jeong
Namdong Kim
Hyun-Joon Shin
Dong-Hyun Kim
2019-01-07T03:12:06Z
2019-01-07T03:12:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3400
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3400
2019-01-07T03:12:06Z
Alternative approaches used to assess structural changes of natural zircon caused by heat treatment
Thi Thu Huong LE
ltthuongvnu@yahoo.com
Thi Minh Thuyet Nguyen
The Long Phan
Ngo Tran
Ngoc Toan Dang
Duc Thang Pham
pdthang@vnu.edu.vn
The Huy Bui
2019-01-07T02:43:25Z
2019-01-07T02:43:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3401
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3401
2019-01-07T02:43:25Z
Crystal Structure and Magnetic Properties of La0.8R0.2(Fe0.88Si0.12)13 (R = Sm and Tb) Compounds
Van Hiep Vuong
Khac Thuan Nguyen
Thi Kim Anh Do
Nam Nhat Hoang
nhathn@vnu.edu.vn
2019-01-07T02:40:13Z
2019-01-07T02:40:13Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3402
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3402
2019-01-07T02:40:13Z
Low Field Magnetocaloric Effect in Bulk and Ribbon Alloy La(Fe0.88Si0.12)13
Van Hiep Vuong
Thi Kim Anh Do
Duy Thien Nguyen
Quang Hoa Nguyen
Nam Nhat Hoang
nhathn@vnu.edu.vn
2019-01-07T02:36:19Z
2019-01-07T02:36:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3403
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2019-01-07T02:36:19Z
Valence Illustration for Large Structure: A Fast Empirical
Approach Based on Bond-Valence Method
Nam Nhat Hoang
nhathn@vnu.edu.vn
2019-01-07T02:34:43Z
2019-01-07T02:34:43Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3404
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3404
2019-01-07T02:34:43Z
Raman Spectroscopy of CaCu3Ti4O12 Ceramics Revisited
Nam Nhat Hoang
2019-01-07T02:01:03Z
2019-01-07T02:01:03Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3397
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3397
2019-01-07T02:01:03Z
Fabrication of Microsized Magnetic Materials by Ink-Jet Printing
Micro-magnetic structures including Nd-Fe-B microsized particles were produced by the ink-jet printing technique. The Nd-Fe-B particles were commercial MQP-B particles with a Nd2Fe14B phase and an average diameter of 6 µm. The particles were milled to a mean particle
size of about 300 nm before being added to the standard ink, MFL-003. The resultant magnetic suspension contained nanosized Nd-Fe-B particles with a suitable weight percentage (43%) and displayed a negligible difference in parameters, such as viscosity, pH, etc., compared to
those of the standard ink. The produced magnetic structure, that can be used to trap magnetic particles and can be developed into a microsized
magnetic source, consists of squares with thickness of 40 µm and surface area of 500 × 500 μm2. Also, the properties of the magnetic structure
were discussed. The obtained results show that the ink-jet printing technique is a simple and fast method for fabricating microsized magnetic
structures.
Viet Cuong Le
cuonglv@vnu.edu.vn
K Thuan Nguyen
Duc Thang Pham
pdthang@vnu.edu.vn
2019-01-07T02:00:01Z
2019-01-07T02:00:01Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3398
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3398
2019-01-07T02:00:01Z
Minor hysteresis patterns with a rounded/sharpened reversing behavior in ferromagnetic multilayer
Hysteresis of ferromagnetic system exhibits a fundamental stimulus-response behavior, thereby
casting all the important macromagnetic system parameters such as coercivity, nucleation feld,
saturation magnetization, and hysteresis loss. Recently, increasing attention has been paid to
exploration of relatively less understood minor loop behavior, since faster operation of magnetic
devices is inevitably accompanied by minor hysteresis behavior from cycling among unsaturated
ferromagnetic states. Here, we report our microscopic investigation of unusual minor hysteresis loop
behavior, represented by rounded or sharpened response of minor hysteresis loop of (CoFeB/Pd)4
multilayer flm. It is observed that rounded and sharpened response in the minor hysteresis response
could be manifested under proper conditions. The minor loop behavior has been systematically
investigated by direct microscopic magnetic domain observation using magneto-optical Kerr
microscopy. The rounded response of magnetization at the reversing external feld along the minor
hysteresis curve, so far neglected or considered as one of ‘unusual’ behaviors, has been found to be
elaborately controllable by tuning the reversing feld strength and the feld sweep rate for multilayers
with low repeat numbers. Variable roundedness of the minor hysteresis loop is understandable based on
the analysis of magnetic domain dynamics such as domain nucleation and the domain wall velocity.
Duy Truong Quach
Duc Thang Pham
pdthang@vnu.edu.vn
Duc The Ngo
The Long Phan
Seung-Young Park
Sang-Hyuk Lee
Dong-Hyun Kim
2019-01-04T00:18:29Z
2019-01-04T00:21:14Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3396
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3396
2019-01-04T00:18:29Z
Characterization of NH3 sensing properties of P3HT+rGO+CNT composite films made by spin-coating
Thin films of poly(3-hexylthiophene) (P3HT) incorporated with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (CNTs) were prepared by spin-coating technique.
Atomic force microscope (AFM) surface morphology, UV-Vis spectra and NH3 gas sensing of the films were studied. Results showed that the P3HT embedded with a content of 20 wt.% of rGO and 10 % of CNTs (abbreviated to P3GC) resulted in the formation of nanostructured composites,
exhibiting 1.50 nm-roughness surface and a semiconducting material with a bandgap of 1.92eV. These structure and composition of the P3GC film are appropriate for making film sensors, whose resistance changes as a function of gas concentration. Monitoring ammonia gas by the sensors showed that the responding time of the sensing reached a value as fast as 30 s, the response at ammonia gas content of 10 ppm attained a value as large as 0.8% and the relative sensitivity was
of 0.05 %/ppm.
Minh Long Lam
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Quang Trung Tran
2019-01-02T03:16:15Z
2019-01-02T03:16:15Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3351
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2019-01-02T03:16:15Z
Xác định gốc tự do hydroxyl radical trong nước khử ion được chiếu xạ plasma
Hydroxyl radical (•OH) là một loại gốc tự do (reactive oxygen species, ROS) được tạo ra trong môi trường nước tinh khiết (distilled water) bằng chiếu xạ plasma với thời gian chiếu xạ thay đổi từ 0s đến 300s. Hydroxyl radical được xác định bằng chất chỉ thị terephthtalic acid (TPA) do •OH radical tác dụng với chất TPA tạo nên chất 2-hydroxyl-terephthtate (HTPA) có khả năng phát huỳnh quang tại bước sóng 425nm có cường độ phụ thuộc thời gian chiếu xạ plasma. Kết quả phân tích phổ huỳnh quang của dung dịch HTPA cho thấy •OH radical đã được tạo ra trong dung dịch TPA khi bị chiếu xạ plasma; Thời gian chiếu xạ 120s cho cường độ huỳnh quang của HTPA là lớn nhất tương ứng với nồng độ •OH radical được tạo ra trong dung dịch TPA là cao nhất. Điều này cho phép tối ưu thông số chiếu xạ của thiết bị plasme sao cho nồng độ •OH radical được tạo ra lớn nhất.
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2019-01-02T03:14:11Z
2019-01-02T03:14:11Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3380
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3380
2019-01-02T03:14:11Z
Conducting Polymers incorporated with Related Graphene compound films for use for humidity and NH3 gas sensing
Using spin-coating technique, PEDOT:PSS+GQD+CNT (GPC), PEDOT:PSS+GQD+AgNW (GPA) films used for humidity sensors and P3HT+rGO+CNT (P3GC) films used for NH3 gas sensors were prepared. At room temperature and atmospheric pressure, all the sensing devices have extremely simple structure and they respond well to the humidity change (for GPC and GPA) and NH3 gas (for P3GC). The sensitivity of both the GPC and GPA humidity sensing devices was foud to be dependent on the additives of CNT or AgNW. For the GPA sensors the best sensitivity attained a value as large as 15.2 % with a response time of 30 s.
For the NH3 gas sensors made from P3GC films with a content of 20 wt.% of rGO and 10 % of CNTs, the best performance parameters were obtained, such as responding time of ca. 30 seconds, sensing response of 0.8% at ammonia gas concentration of 10 ppm and a relative sensitivity of 0.05 %/ppm. The fact that the P3HT+rGO+CNT sensors do not respond to humidity suggests useful applications in gas thin film sensors for selectively sensing ammonia gas in a humid environment.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2018-12-25T03:53:28Z
2019-01-07T03:17:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3384
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2018-12-25T03:53:28Z
Thiết kế và mô phỏng tính toán cấu hình khuếch đại và tập trung từ thông tích hợp trong các hệ vi từ kế cho các ứng dụng y-sinh
Cùng với sự phát triển của công nghệ Micro và Nano và sự tiến bộ của khoa học công nghệ trong lĩnh vực vi cảm biến kích thước micro, nhiều ứng dụng trên các sản phẩm này đặc biệt trong khoa học sự sống như y, sinh học và môi trường đã được phát triển mạnh mẽ và đem lại nhiều thành tựu. Trong những năm gần đây, công nghệ vi lưu nhận được sự quan tâm lớn từ phía các nhà khoa học, đặc biệt là từ các quốc gia có nền khoa học chưa thực sự phát triển. Một trong những định hướng nghiên cứu trong nghiên cứu này là hướng đến ứng dụng sản phẩm trong thử nghiệm, đo đạc, xét nghiệm nhanh các thông tin liên quan đến Hemoglobin và các ứng dụng khác liên quan như bệnh sốt rét và phát hiện một số chủng vi khuẩn/vi-rút khác, dựa vào sự thay đổi tính chất từ của chúng trong những điều kiện khác nhau. Đối với các phần tử sinh học không thể hiện rõ tính chất từ, phương án lai hóa các phần tử sinh học sau với các hạt từ có thể dễ dàng được phát hiện bởi các vi cảm biến từ độ nhạy cao là một trong các hướng nghiên cứu trọng tâm của Phòng thí nghiệm Trọng điểm Công nghệ Micro và Nano, Trường ĐH Công nghệ, ĐHQGHN. Theo định hướng nghiên cứu này, việc tìm ra giải pháp giúp tăng cường độ nhạy, độ phân giải của hệ thống cảm biến nhưng đồng thời mang lại hiệu quả kinh tế đã được nhóm nghiên cứu tập trung theo hướng sử dụng các bộ tập trung và khuếch đại từ trường – concentrator được thiết kế tính toán và chế tạo phù hợp tích hợp với vi cảm biến. Báo cáo này sẽ tập trung trình bày các kế quả thiết kế và mô phỏng tính toán cấu hình khuếch đại và tập trung từ thông cho các ứng dụng này. Đây là hướng nghiên cứu có tiềm năng, không chỉ tạo ra các sản phẩm nghiên cứu có chất lượng cao mà còn định hướng ứng dụng cho ra các sản phẩm thương mại trong mục đích y-sinh chuẩn đoán và phát hiện nhanh các bệnh thông qua phương pháp đánh dấu từ.
Anh Tam Ho
hoanhtam@vnu.edu.vn
2018-12-19T09:39:41Z
2018-12-21T01:10:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3346
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3346
2018-12-19T09:39:41Z
Design Optimization of an Anisotropic Magnetoresistance Sensor for Detection of Magnetic Nanoparticles
Recent studies have shown that the magnetic field sensitivity of an anisotropic
magnetoresistance (AMR) sensor using a single-layer Ni80Fe20 thin film can be
considerably improved by increasing the shape anisotropy of the film. In this
work, an effective approach for improving the sensitivity and reducing the
magnetic coercive field as well as the thermal noise contribution in an AMR
Wheatstone bridge sensor is proposed by combining multiple resistors in the
series–parallel combination circuits. Four different AMR sensor designs,
consisting of a single resistor, three and five resistors in series and six resistors
in series–parallel connection, were fabricated by using Ta (10 nm)/Ni80Fe20 (5 nm)/Ta (10 nm) films grown on thermally oxidized Si substrates under the presence and the absence of a biasing magnetic field (900 Oe). The results showed that the sensors based on series–parallel combination gain a magnetic sensitivity (SH) 1.72 times higher than that of the sensor based on the series connection. This optimized sensor has improved the capacity of detecting various oncentrations of magnetic nanoparticles with a detection limit of magnetic moments estimated to be about 0.56 microemu
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Khac Quynh Le
quynhlk@gmail.com
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Anh Tuan Phung
Thi Dung Tran
Viet Anh Cao
2018-12-19T05:07:30Z
2018-12-19T09:21:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3324
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3324
2018-12-19T05:07:30Z
Influences of Morphology of Window Layer on the Characteristics of PbS Quantum Dot Solar Cells
Background: In QDs-based solar cell devices, the PbS QDs layer was mainly focused
to optimize. The ZnO electron acceptor layer attracts less attention whereas it shows the key
roles in extracting and transporting charge carriers in heterojunction. The utilization of 1-D ZnO
structures has been demonstrated to be large interface areas and good carrier pathways for efficient carrier collection. However, the influences of the morphology of metal oxide nanostructures on the photovoltaic performance of QD-based solar cells have been few in-depth reports.
Objective: In this work, ZnO NRs/PbS QD based solar cells were fabricated. The influences of
the ZnO NRs array structures on characteristics of ZnO NRs/PbS QD based solar cells were investigated.
Method: ZnO NRs/PbS QD based solar cells were fabricated via spin coating method. XRD,
SEM, UV-VIS-NIR spectrophotometer, I-V and EQE measurement systems were utilized to investigate the fabricated samples.
Results: We have found optimum combinations of the linked parameters of ZnO NRs, their
length of (230 ± 5) nm and density of (1.50 ± 5)x1010 # of rods.cm-2, that exhibit maximum efficiency of ∼2.5% for the ZnO NR/PbS QDs based solar cell.
Conclusion: The influences the ZnO NRs structures on the solar cell characteristics, including
the absorption, external quantum efficiency, and current density-voltage curves, were investigated. There seems to be an optimum between NR length and their density for resulting in maximum efficiency. This could be due the interplay of solar flux absorption and junction area controlled by these two parameters of ZnO NR morphology.
Thu Ha Nguyen
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2018-12-17T09:42:49Z
2018-12-17T09:42:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3322
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3322
2018-12-17T09:42:49Z
Mechanism of the photocatalytic activity of p-Si(100)/n-ZnO nanorods heterojunction
A heterojunction of p-Si(100)/n-ZnO nanorods was fabricated by a simple hydrothermal method. The
photocatalytic activity of this heterojunction was examined by degradation of Rhodamine B (RhB) under
UV light irradiation. The results indicated that the p-Si(100)/n-ZnO nanorods heterojunction exhibits
higher photocatalytic activity compared to that of a glass/n-ZnO nanorods. The inner electric field created
by the space charge region of heterojunction will oppose the recombination of photogenerated electrons
and holes. Furthermore, this heterojunction serves as a convenient recyclable and effective photocatalyst.
The photodecomposition rate of RhB after 5 cycles is negligible change in an experiment using this
heterojunction.
Thi Hoa Nguyen
Van Cuong Vuong
Dinh Lam Nguyen
lamnd2005@vnu.edu.vn
2018-12-17T03:59:53Z
2018-12-18T07:02:57Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3298
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3298
2018-12-17T03:59:53Z
NGHIÊN CỨU CHẾ TẠO NANG CHITOSAN HYDROGEL ĐỂ ĐÓNG GÓI NANOCURCUMIN
Chitosan đang được nghiên cứu làm vỏ bao nang thuốc thay thế cho gelatin vì chitosan có tính tương thích sinh học và phân hủy sinh học và có thể thay đổi cấu trúc như một polyme thông minh để đáp ứng sự thay đổi pH ở môi trường axit. Trong công trình này, chitosan được chế tạo dưới dạng cấu trúc nang hydrogel để bảo vệ niosome-curcumin (curcumin trong chất mang kích thước nano) khỏi môi trường axit thấp của dạ dày, giúp cho niosome-curcumin đến được ruột non. Nang chitosan hydrogel được tạo ra bằng phương pháp gel hóa dung dịch chitosan nhờ chất hoạt động bề mặt sodium dodecyl sulfate (SDS), sau đó loại bỏ SDS để tạo nang chitosan hydrogel tương thích sinh học. Kết quả này được khẳng định bằng phương pháp phân tích phổ hồng ngoại chuyển đổi chuỗi Fourier (FTIR). Nang chitosan hydrogel tương đối đồng đều với đường kính ngoài khoảng 3 mm, khối lượng trung bình khoảng 10 mg/hạt. Quá trình hấp thụ và giải phóng dược chất được nghiên cứu bằng phương pháp phổ huỳnh quang vì curcumin là chất huỳnh quang. Mười nang chitosan hydrogel hấp thụ được 4,67 mg niosome-curcumin (tương đương với 30 microgram curcumin). Nang chitosan hydrogel bảo vệ niosome-curcumin tại pH 1,5 và giải phóng được khoảng 5% curcumin ở giá trị pH 1,5 sau hai giờ.
Thi Hien Le
lehien@vnu.edu.vn
Thi Yen Nguyen
hoangyen666.yh@gmail.com
2018-12-14T10:07:41Z
2018-12-14T10:07:41Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3283
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3283
2018-12-14T10:07:41Z
PHÂN TÍCH TRÌNH TỰ GEN MÃ HÓA ĐỘC TỐ TẢ
CỦA MỘT SỐ CHỦNG VIBRIO CHOLERAE
Vibrio cholerae, the major agent causing cholera, contains more than 200 serotypes based on O antigen. But only two serotypes of O1 and O139 have caused cholera pandemics in the global. The previous studies have shown that cholera toxin gene have been presented not only in epidemic strains, but also presented in strains of non-O1 / non-O139 serotypes. Opposite, V. cholerae O1 and O139 strains could also have no toxin gene.
In this papers, we selected the sequences of cholera toxin genes (ctx) from some of V. cholerae isolates representing the O1 serotype (the sixth and the seventh cholera pandemic strains) and non-O1 / non-O139 serotypes (strains of O27, O37 and O105 serotypes), that were isolated in different geographical regions of Asia for analyzing and comparison to cholera toxin gene of V. cholerae strain in Vietnam. By using MEGA version 6.0 software, the statistical data as well as the phylogenetic trees showed that cholera toxin gene of V. cholerae in Vietnam was different and always form a separate branch comparing to the cholera toxin genes of other strains. This proved that ctx gene of V.cholerae in Vietnam has own genetic characteristics comparing to ctx genes of the strains in other geographic zones.
The results have demonstrated it’s necessary of determining the changes of cholera toxin gene of V.cholerae strains in different geographical areas. This not only provides information for epidemiological surveillance but also provides important data for cholera disease prevention, because of differences in cholera toxin genes can lead to the ability of different anti-cholera toxin immune response during infecting by these pathogenic clones.
Thi Quyen Ha
quyenht@vnu.edu.vn
2018-12-14T01:39:32Z
2018-12-21T01:12:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3244
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3244
2018-12-14T01:39:32Z
The modification of the curing properties of Bis phenol F epoxy resin by nanosilica SiO2
The modification of nanosilica SiO2 to the curing of Bis phenol F epoxy resin (epoxy F) by triethyl tetraamine (TETA) was characterized. The curing properties of the nanocomposite epoxy F:SiO2 membranes are better than Bis phenol F epoxy films. With the content from 0,1 to 0,3% of SiO2 the films epoxy F:SiO2 show the excellent curing properties which get higher 96% of the gelation. The quantum size effect of nanosilica SiO2 was also discussed.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2018-12-12T02:54:41Z
2018-12-12T02:54:41Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3207
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3207
2018-12-12T02:54:41Z
LIGHT ABSORPTION AND PHOTOLUMINESCENCE QUENCHING PROPERTIES OF BULK HETEROJUNCTION MATERIALS BASED ON THE BLEND OF POLY(N-VINYLCARBAZOLE)/POLY(N-HEXYLTHIOPHENE)
The enhancement of light absorption and photoluminescence quenching properties of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK); poly(N-hexylthiophene) (P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the region from ultra violet to near infra-red and the photoluminescence quenching higher than 90%. The obtained results provide further insight into photophysics of the heterojunction system and device performance improvement by using this system as an active layer.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2018-11-24T01:58:46Z
2018-11-24T01:58:46Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3001
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3001
2018-11-24T01:58:46Z
Investigation on solution-processed In-Si-O thin film transistor via spin-coating method
In this work, we have explored optimum fabrication condition by a solution processing method for 3 at.% Si doped indium oxide thin-film transistors (TFTs). In-Si-O (ISO) thin films were investigated by X-ray reflectivity (XRR) and X-ray diffraction (XRD) techniques, and the operation of TFTs were characterized by a conventional three-probe method. XRR results suggested that as the annealing temperature increased, the film thickness decreased. In addition, according to XRD measurement, the ISO film started crystalline from 850 °C regardless the film thickness. The best ISO TFT showed the value of VT of –5 V, µ of 1.32 cm2/Vs, SS of 1 V/dec, and on/off current ratio about 107.
Ha Hoang
Tatsuki Hori
To-oru Yasuda
Takio Kizu
Kazuhito Tsukagoshi
Toshihide Nabatame
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
Akihiko Fujiwara
2018-11-20T09:05:19Z
2018-11-20T09:05:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3164
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3164
2018-11-20T09:05:19Z
Si-doping effect on solution-processed In-O thin-film transistors
In this work, silicon-doped indium oxide thin-film transistors (TFTs) have been fabricated for the first
time by a solution processing method. By varying the Si concentration in the In2O3–SiO2 binary oxide
structure up to 15 at%, the thicknesses, densities, and crystallinity of the resulting In–Si–O(ISO) thin
films were investigated by x-ray reflectivity (XRR) and x-ray diffraction techniques, while the
produced TFTs were characterized by a conventional three-probe method. The results of XRR analysis
revealed that the increase in the content of Si dopant increased the thickness of the produced film and
reduced its density, and that all the Si-doped ISO thin films contained only a single amorphous phase
even after annealing at temperatures as high as 800 °C. The manufactured ISO TFTs exhibited a
reduction in the absolute value of threshold voltage VT close to 0 Vand low current in the off-state, as
compared to those of the non-doped indium oxide films, due to the reduced number of oxygen
defects, which was consistent with the behavior of ISO TFTs fabricated by a sputtering method. The
ISO TFT with a Si content of 3 at% annealed at 400 °Cdemonstrated the smallest subthreshold swing
of 0.5 V/dec, VT of−5 V, mobility of 0.21 cm2 V−1s−1, and on/off current ratio of about 2×107.
Ha Hoang
Tatsuki Hori
To-oru Yasuda
Takio Kizu
Kazuhito Tsukagoshi
Toshihide Nabatame
Nguyen Quoc Trinh Bui
Akihiko Fujiwara
2018-10-29T04:32:17Z
2019-01-07T07:57:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3122
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3122
2018-10-29T04:32:17Z
Region-based deformation transfer
Mesh deformation is a fundamental technique
for geometric modeling which is applied successfully
in a wide range of applications from shape
design to computer animation. Normally, the deformation
transferred from one actor to another actor is based
on all vertices and triangles of a mesh, leading to timeconsuming
in terms of a 3D sequential model. To address
this problem, we propose a region-based deformation
transfer that automatically identifies several regions with
the largest displacement in time series, and then exploits
those deformations of such regions. Our experimental
results demonstrate that we can obtain the similar deformed
mesh in spite of using approximately 50% – 60%
of the facial area, therefore the time decrease significantly
for deformation transfer step.
Khac Phong Do
phongdk92@gmail.com
Thi Chau Ma
chaumt@vnu.edu.vn
Hoang Giang Cao
Thi Thu An Nguyen
2018-10-09T09:59:51Z
2018-10-09T09:59:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3090
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3090
2018-10-09T09:59:51Z
2d-Arrrays of Cu Nanodisks on Anodic Aluminum Oxide (AAO) Template for Sers Applications
Copper nanodisks (Cu NDs) of 50 nm were prepared on square-inch anodic aluminum oxide substrates by sputtering method. The samples were annealed at 450oC, then the walls of AAO substrates were lift off in a solution of acid phosphoric. The 2D arrays of Cu NDs were fabricated in high quality. Morphology of the substrates were observed by scanning electron microscopy. Surface plasmon resonance absorption was observed with different peaks in the range of 400-1400nm wavelengths that means the substrate is promising for SERS application. To demonstrate, we observed Raman spectrum of Rhodamine 6G using the enhancement effect of the substrate.
Thi Yen Mai Nguyen
mainty85@gmail.com
Thi Ha Nguyen
2018-10-09T09:58:45Z
2018-10-09T09:58:45Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3089
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3089
2018-10-09T09:58:45Z
Fabrication of Ferrite-Based Integrated Micro-Inductors onto Silicon Wafer
In this work, the technology for fabricating integrated micro-inductors onto silicon is
developed. The paper will report the experimental process and technology development to
fabricate the micro-inductor on-to silicon substrates with the hybrid integration approach.
Copper is used for the fabrication of the conductor windings and vias. Electro-deposition is
chosen for depositing copper. Via is electro-deposited to make the connection between bottom
tracks and top tracks. The ferrite core is fabricated and sintered from in-house ferrites or
commercial ferrite films.
Yen Mai Nguyen
mainty85@gmail.com
Magali Brunet
2018-07-06T03:27:37Z
2018-07-06T03:27:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3038
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3038
2018-07-06T03:27:37Z
The Nutritional Value of Three Species of Microalgae for Clam larvae, Meretrix meretrix
A feeding trial was conducted to assess the nutritional value of three monospecific microalgal diets for clam larvae, Meretrix meretrix. The three species tested were Chaetoceros TH01, Pavlova TH03 và Thalassiosira TH06. The fatty acids of Chaetoceros TH01, Pavlova TH03 were saturated fatty acids ranged 71.36 to 73.76%; Pavlova TH03 had amounts of HUFAs fatty acids 70,53%, of which MUFAs 31,77%, PUFAs 38,76%. Diatoms contained HUFAs as Eicosatetraenoic acid (ETA), Arachidonic acid (AA), Eicosapentaenoic Acid (EPA). Three species of microalgae included Chaetoceros TH01, Pavlova TH03 and Thalassiosira TH06 all showed good growth in larval size and improved survival rate. Pavlova TH03 was the most suitable for growth stages of clam larvae, with a survival rate of more than 90%, average length of shells met the standard of growth stages of clam which were 120.5 μm (veliger larvae); 420.5 μm (spat larvae). The results iliustrate the importance of experimental testing of algal diets for larvae rather than sole reliance on published nutritional values.
Dang Khoa Tran
khoatd@vnu.edu.vn
Thi Bich Dao Pham
Thi Hoai Ha Nguyen
2018-07-06T03:25:55Z
2018-07-06T03:25:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3037
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3037
2018-07-06T03:25:55Z
Analysis of gene encoding haemolysin A of Vibrio cholerae isolated in Vietnam
Vibrio cholerae is the cholera causing agent, divided into two biotypes, including the classical biotype and ElTor biotype. Both of these biotypes caused cholera epidemics in the world. The classical biotype caused 6th cholera pandemic (from 1921 to 1961), and ElTor biotype caused 7th cholera pandemic (from 1961 to the 70s). Haemolysin A, a hemolytic protein of V. cholerae ElTor biotype, is encoded by the hlyA gene. This gene is often used for analyzing genetic relationship between strains in the same species or between species in the same Vibrio genus. Results of analyzing nucleotide and amino acid sequences of hlyA gene of V. cholerae strain causing cholera in Vietnam (named hlyA.VN) showed that: the hlyA.VN gene sequence was similar to the hlyA gene sequences of V. cholerae strains of the 6thand 7thcholera epidemics. The hlyA gene of the 6th cholera epidemic strain was deficient in 11 nuleotides (this deficiency leading to the loss of 4 amino acids in the haemolysin A protein) comparing to hlyA.VN gene and hlyA gene of the 7th cholera epidemic strain. The results of genetic distance analysis as well as phylogenetic tree construction also confirmed V. cholerae causing cholera in Vietnam was closely relationship to the strains causing cholera pandemics in the world. It is great significance for the surveillance of molecular epidemiology to prevent cholera effectively.
Thi Quyen Ha
quyenht@vnu.edu.vn
2018-07-06T03:25:16Z
2018-07-06T03:25:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3036
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3036
2018-07-06T03:25:16Z
NGHIÊN CỨU GEN CÓ VAI TRÒ CHẨN ĐOÁN VI KHUẨN SALMONELLA TYPHIMURIUM
Research and detection of genes having function for diagnose pathogenic bacteria are essential for environmental and safe food surveillance. In this study, we designed specific primers and constructed a thermal cycle to amplify the specific fragment of the invA gene that encodes the protein invasion of Salmonella typhimurium, having function for infection to the host. In addition, the bacterial clones containing invA gene has been cloned. The exact determination of the invA gene in this report was confirmed by nucleotide sequencing and compared to homology sequences in Genbank. The results of this study could be used to develop a Salmonella Diagnostic Kit using PCR. And the clones containing the invA gene would be stored to provide target genes for continuing studies.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Minh Tu Hoa
hoaminhtu@gmail.com
2018-07-06T02:56:40Z
2018-07-06T02:56:40Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3040
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3040
2018-07-06T02:56:40Z
Integrated inductor fabrication by monolithic approach
This technical report will present the experimental approaches and technological processes to realize the ferrite-based micro-inductor. The objective is to develop a technology for fabricating integrated micro-inductors on/in silicon based on ferrite as magnetic cores. Copper is chosen for the winding as top tracks, bottom tracks and vias. Electro-deposition technology is used for copper deposition.
Thi Yen Mai Nguyen
mainty85@gmail.com
2018-07-06T02:55:37Z
2018-07-06T02:55:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3035
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/3035
2018-07-06T02:55:37Z
Chế tạo & khảo sát tăng cường phổ Raman của hạt nano vàng
của SERS ứng dụng xác định dư lượng hóa chất (Fabrication & Characterization of Gold Nanoparticles on a Surface Enhancing Raman Spectra (SERS) to Dectect Chemical Residuals)
Tăng cường tín hiệu phổ tán xạ Raman (SERS) đang được nghiên cứu để xác định các dư lượng hóa chất có nồng độ rất nhỏ (< 10-9M) có trong thực phẩm và các sản phẩm y-dược. Màng SERS được chế tạo từ các hạt nano vàng (AuNPs), có kích thước 3-5 nm và xếp chồng trên bề mặt đế thủy tinh. Tín hiệu phổ tán xạ Raman được tăng lên gấp nhiều lần khi chiếu vào bề mặt SERS. Điều này được chứng minh bằng cách phủ bề mặt SERS bằng chất màu phát quang Rhodamine 6G (Rh6G) ở nồng độ rất nhỏ 10-9M. Kết quả đo phổ tán xạ Raman cho thấy Rh6G ở nồng độ 10-9 M vẫn xuất hiện các đỉnh đặc trưng của Rh6G. Điều đó cho phép dùng màng SERS để đo dư lượng các chất hóa học có nồng độ rất thấp, đủ để ứng trong thực phẩm và y-dược.
Keywords: Hạt nano vàng (AuNPs), tăng cường tín hiệu phổ tán xạ Raman trên cơ sở hiệu ứng bề mặt (SERS), Rhodamine
6G (Rh6G).
Cường / Kiên Nguyễn
cuongnk@vnu.edu.vn
2018-07-06T02:54:06Z
2018-07-06T02:54:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2981
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2981
2018-07-06T02:54:06Z
Preparation and Characterization of Reduced Graphene-P3HT Composite Thin Films for Use as Transparent Conducting Electrodes
With the aim of producing simple and effective transparent conducting electrodes,
the conducting polymer poly(3-hexylthiophene) (P3HT) incorporated
with reduced graphene oxide film (rGO) (called rGO-P3HT) was prepared by
spin-coating method. Structural, electrical and optical characterization
showed that rGO-P3HT films 9.0 wt% P3HT exhibited good stability when
exposed to the ambient atmosphere. These composite films of 200 nm thickness
possess a sheet resistance and transparency of R
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Minh Long Lam
Dinh Long Dang
Trong Tinh Nguyen
Antonovic Chizhik Sergei
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2018-06-18T07:54:20Z
2018-06-18T07:54:20Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2998
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2998
2018-06-18T07:54:20Z
Solution-processed CuO thin films with various Cu2+ ion concentrations
Presented herein is a report on cupric oxide (CuO) thin films prepared on glass substrates by using a solution process with varying nominal concentrations of Cu2+ ions at 0.15 M, 0.20 M, and 0.25 M. X-ray diffraction patterns and scanning electron microscopy (SEM) micrographs were analyzed to evaluate the crystalline structure and surface morphology of the CuO thin films. The fabricated CuO thin films exhibited a single-phased monoclinic structure with (200) and (111) orientations. The grain size of the CuO thin films was observed to increase with higher concentration, by SEM observation. The electrical and optical properties of the CuO thin films were investigated using a four-probe measurement system and UV/VIS spectrometer, respectively. The thin films showed a minimum resistivity of 0.085 Ωcm corresponding to the 0.25 M concentration, and a bandgap energy ranging from 2.10 eV to 2.15 eV. In addition, the light-harvesting ability of CuO thin films was considered by the absorption figure of merit (a-FOM), in correlation with the global solar spectrum. A maximum a-FOM value of 12.79 Ω-1cm-1 was attained for the sample with a Cu2+ ion concentration of 0.25 M.
Quang Hoa Nguyen
Van Dung Nguyen
Akihiko Fujiwara
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2018-06-14T07:58:37Z
2018-06-14T07:58:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2999
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2999
2018-06-14T07:58:37Z
Conductive-perovskite LaNiO3 thin films prepared by using solution process for electrode application
: Lanthanum nickel oxide LaNiO3 (LNO) is extensively known as one of typical perovskite-structured materials with metallic conductivity, which is suitable for the electrode application in electronic devices such as transistors or solar cells. Since LNO is a low-cost material and a simple fabrication process, it has been attracted much attention for commercialization. In this paper, we have focused on optimizing the fabrication process of LNO thin films on SiO2/Si substrate and Al foil by using a solution process. The crystal structure and surface morphology were characterized by using X-ray diffraction and field-emission scanning electron microscopy (FE-SEM), respectively. It was found that the LNO thin films annealed in range of 550-700oC for 30 minutes exhibited a well-formed crystallization and a dense microstructure. According to the SEM cross-sectional observation, the thickness of LNO thin films was estimated about 80 nm. Also, from the four-probe measurement method, the electrical resistivity of LNO thin film annealed at 600oC had a minimum value of 0.42 × 10-2 Ωcm, which was possibly comparable to conventional conductive oxides. As a result, the capacitor using Pb1.2(Zr0.4Ti0.6)O3 ferroelectric layer annealed at 600oC and LNO bottom electrode provided an interesting ferroelectricity, which included a remnant polarization of 21 µC/cm2 and a saturated polarization of 35 µC/cm2. Moreover, the leakage current density was lower than 2 × 10-5 A/cm2.
Quang Hoa Nguyen
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2018-02-06T06:47:38Z
2018-02-06T06:48:01Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2922
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2922
2018-02-06T06:47:38Z
Study on current–voltage characteristics of OLEDs using
Alq3 as the electron transport layer
This paper describes changes in current-voltage (I-V) characteristic of an organic lightemitting
device (OLED) stacked as a multilayer of ITO/MEH-PPV/Alq3/Al. The ordered, stacked
ITO/MEH-PPV/Alq3/Al multi-layers were fabricated by spin-coating and thermal vacuum
evaporation methods. First, dissolved MEH-PPV solution was spin-coated on ITO-electrodes that
had been covered on a glass-slide. Subsequently, an Alq3 layer was evaporated thermally on the
MEH-PPV-coated layer. Finally, an Al-electrode was evaporated also on the electron transport
layer. UV-vis absorption and photoluminescent characterization of the MEH-PPV and Alq3 layer
as well as their surface images were performed. All spectra obtained revealed the MEH-PPV and Alq3 were deposited as given structure. The I-V characteristics show the present of the Alq3-electron transport layer deposited between the MEH-PPV emissive layer and Al-cathode could enhance current-voltage characteristic reducing the threshold voltage and turn-on voltage.
Keywords: UV-vis absorption, photoluminescence, electron transport layer, current-voltage characteristics.
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2018-02-06T06:47:28Z
2018-02-06T06:47:28Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2921
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2921
2018-02-06T06:47:28Z
Synthesis and optical properties of CdSe/CdSe1-xSx
heterostructure nanorods using Oleylamine
Colloidal CdSe/CdSe1-xSx heterostructure nanorods were synthesized by the seeded growth method. By changing the temperature, type of ligand, we synthesized the Wz-CdSe
nanocrystals as seeds for growth of CdSe/CdSe1-xSx heterostructure nanorods. The yield of heterostructure nanorods depend on the amount of oleylamine in the reaction mixture. Their morphology, crystalline structure and optical properties were investigated by transmission electron microscopy, X-ray diffraction, optical absorption and photoluminescence spectroscopy.
Keywords: heterostructure nanorods, oleylamine, photoluminescence.
Luyến / Thị Nguyễn
luyen0803@gmail.com
Nghĩa / Xuân Nguyễn
Cường / Kiên Nguyễn
cuongnk@vnu.edu.vn
Liễu / Thị Thúy Nguyễn
2018-02-06T06:47:21Z
2018-02-06T06:47:21Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2920
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2920
2018-02-06T06:47:21Z
Quantitative analysis of COOH-terminated alkanethiol SAMs on gold nanoparticle surfaces
Surface-functionalization of a self-assembled monolayer (SAM) can be achieved byintroducing functional molecules
at the terminal. To immobilize biomolecules on a gold
substrate, COOH-terminated alkanethiol SAMs are preferably employed. Thiol molecules adsorption on gold surface was performed using thioglycolic acid (TGA, HS-CH2-COOH) monomers and a self-assembled technique.
Characterization by Fourier transform infrared (FTIR) spectroscopy revealed gold–sulfur (Au–S) bonding through confirming the presence and disappearance of thiol molecules on the Au surface before and after the sample’s immersion in the TGA solution. Moreover, FTIR spectra also proved the presence of carboxyl molecules (C=O; OH) at the free end on the gold nanoparticle (AuNP) surface. Quantitative analysis of the carboxyl molecules interacted with methylene blue (MB) ones, and then identification by UV-Vis absorption spectroscopy showed
that the average density of the carboxyl molecules on the free end of the alkanethiol SAM was about 3.9 × 1014 molecules per cm2
Keywords: Au–S bond, self-assembled monolayer (SAM), thioglycolic acid (TGA), carboxyl molecular density
Cường / Kiên Nguyễn
cuongnk@vnu.edu.vn
2018-02-06T06:43:34Z
2018-02-06T06:43:34Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2919
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2919
2018-02-06T06:43:34Z
Effects of nitrogen incorporation on structure of a-C:H films deposited on polycarbonate by plasma CVD
Nitrogen-incorporated-hydrogenated amorphous carbon (a-C:H:N) films were deposited on polycarbonate (PC) substrates by r.f. plasmaenhanced chemical vapor deposition (PECVD). Effects of nitrogen incorporation on microstructure, bonding states, chemical composition,
internal stresses, and friction coefficients of deposited films were investigated. The films were characterized by X-ray photoelectron microscopy, infrared microscopy (IR), Raman spectroscopy and friction tests. Results from the measurement indicate that incorporated nitrogen content has considerable effects on film properties. Raman spectra of the a-C:H:N films are broad, asymmetric and centered at around wavenumber of 1500 cm-1. Shifting of the G-peak toward the higher wavenumber, narrower bandwidth of the G-peak and an increase of the ID/IG ratio demonstrate the graphitic character of the a-C:H:N films with the further increase of the atomic fraction of nitrogen (N/C). IR spectra demonstrate nitrogen bonded to carbon and hydrogen as CZN, CMN, N–H and C–H bonding configurations in the aC:H:N films. The internal stress considerably decreased as well as the friction coefficient is low when the N/C fraction increased. The surface roughness of the a-C:H:N films estimated by atomic force microscopy (AFM) seems to be less smooth with the increase in the N/C fraction.
Keywords: Nitrogen incorporation; a-C:H:N films; Plasma-enhanced chemical vapor deposition (PECVD); Polycarbonate
Cường/ Kiên Nguyễn
cuongnk@vnu.edu.vn
M. Tahara
N. Yamauchi,
T. Sone
2018-01-11T09:29:47Z
2018-01-11T09:29:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2675
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2675
2018-01-11T09:29:47Z
STUDY ON GENE FOR DIAGNOSIS OF SALMONELLA TYPHIMURIUM
Research and detection of genes having function for diagnose pathogenic bacteria are essential for environmental and safe food surveillance. In this study, we designed specific primers and constructed a thermal cycle to amplify the specific fragment of the invA gene that encodes the protein invasion of Salmonella typhimurium, having function for infection to the host. In addition, the bacterial clones containing invA gene has been cloned. The exact determination of the invA gene in this report was confirmed by nucleotide sequencing and compared to homology sequences in Genbank. The results of this study could be used to develop a Salmonella Diagnostic Kit using PCR. And the clones containing the invA gene would be stored to provide target genes for continuing studies.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Minh Tu Hoa
hoaminhtu@gmail.com
2018-01-09T03:16:07Z
2018-01-09T03:16:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2885
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2885
2018-01-09T03:16:07Z
Modelling the helium plasma jet delivery of
reactive species into a 3D cancer tumour
Cold atmospheric plasmas have attracted significant worldwide attention for their potential beneficial effects in cancer therapy. In order to further improve the effectiveness of plasma in cancer therapy, it is important to understand the generation and transport of plasma reactive species into tissue fluids, tissues and cells, and moreover the rates and depths of delivery,
particularly across physical barriers such as skin. In this study, helium (He) plasma jet treatmentof a 3D cancer tumour, grown on the back of a live mouse, induced apoptosis within the tumour to a depth of 2.8 mm. The He plasma jet was shown to deliver reactive oxygen species through the unbroken skin barrier before penetrating through the entire depth of the tumour. The depth
and rate of transport of He plasma jet generated H2O2, NO3− and NO2−, as well as aqueous oxygen [O2(aq)], was then tracked in an agarose tissue model. This provided an approximation of the H2O2, NO3−, NO2− and O2(aq) concentrations that might have been generated during the
He plasma jet treatment of the 3D tumour. It is proposed that the He plasma jet can induce apoptosis within a tumour by the ‘deep’ delivery of H2O2, NO3− and NO2− coupled with O2(aq); the latter raising oxygen tension in hypoxic tissue.
Keywords: tissue oxygenation, tissue model, plasma jet, hypoxia, hyperbaric medicine, reactive
oxygen species (ROS) and reactive nitrogen species (RNS), cancer therapy
J Szili Endre
Endre.Szili@unisa.edu.au
Oh Jun-Seok
Hideo Fukuhara
Bhatia Rishab
Gaur Nishtha
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
Hong Sung-Ha
Satsuki Ito
Kotaro Ogawa
Chiaki Kawada
Shuin Taro
Tsuda Masayuki
Matsuo Furihata
Atsushi Kurabayashi
Furuta Hiroshi
Masafumi Ito
Inoue Keiji
Hatta Akimitsu
Short Robert D
2018-01-05T02:43:58Z
2018-01-05T02:43:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2898
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2898
2018-01-05T02:43:58Z
Nghiên cứu chế tạo hạt nano COP bằng phương pháp điện hóa siêu âm
Phương pháp điện hóa siêu âm là phương pháp điện hóa kết hợp với sóng siêu âm để chế tạo các hạt nano. Các hạt nano CoP được chế tạo bằng phương pháp điện hóa siêu âm tại nhiệt độ phòng. Cơ chế lắng đọng và thế điện hóa được xác định bằng phương pháp Vol-Ampe vòng. Cấu trúc tinh thể và hình thái học của mẫu được phân tích bằng nhiễu xạ tia X (XRD), hiển vi điện tử quét (SEM). Thành phần của mẫu được xác định bằng phổ tán sắc năng lượng tia X (EDS). Đường cong từ trễ được đo bằng thiết bị từ kế mẫu rung (VSM). Quan sát giả đô nhiễu xạ tia X cho thấy, cấu trú tinh thể của hạt nano CoP là cấu trú lụ giác xếp chặ hcp (100) và hcp (002).
Ảnh hiển vi điện tử quét chỉ ra rằng các hạt nano tạo thành có đường kính trong khoảg 100-300 nm. Kết qua đo
tính chất từ cho thấy, lực kháng từ của mẫu CoP cỡ 756 Oe. Ảnh hưởng của thế lắng đọng và tần số xung siêu
âm lên kích thước hạt cũng đã được nghiên cứu
Quang Ngoc Do
Kim Liet Hoang
Thi Nu Hoang
Duy Thien Nguyen
Thi Huong Giang Do
giangdth@vnu.edu.vn
Minh Hoang Nguyen
Tuan Tu Le
letuantu@vnu.edu.vn
2018-01-05T02:43:10Z
2018-01-05T02:43:10Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2899
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2899
2018-01-05T02:43:10Z
Nghiên cứu, chế tạo cảm biến từ dựa trên hiệu ứng hall phẳng (PHE)
Hệ các cảm biến đo từ trường dạng chữ thập và dạng cầu Wheatstone dựa trên hiệu ứng Hall phẳng (PHE), cấu trúc với màng mỏng đơn lớp Ni80Fe20 đã được chúng tôi nghiên cứu và chế tạo dựa trên thiết bị phún xạ sputtering ATC-2000FC. Các nghiên cứu theo hướng tối ưu hóa cấu trúc, hình dạng cảm biến với mục đích tăng cường độ nhạy theo từ trường, bao gồm cảm biến có các kích thước: 3×1mm, 5×1mm, 10×1mm, 10×0,5mm, có độ dày lớp màng mỏng từ tính khác nhau 5, 10, 20 nm. Kết quả nghiên cứu cho thấy, độ nhạy của cảm biến phụ thuộc mạnh vào tính dị hướng hình dạng và bề dày của lớp NiFe. Tính dị hướng hình dạng càng lớn, bề dày lớp màng NiFe càng mỏng thì độ nhạy cảm biến càng cao. Độ nhạy lớn nhất đạt được trên cảm biến chữ thập có kích thước 10×0,5mm, có bề dày lớp NiFe 5 nm có giá trị 30 µV/Oe, tại dòng cấp 3 mA, tương đương với độ nhạy 10 mΩ/Oe. Với qui trình công nghệ chế tạo đơn giản, cấu trúc màng đơn lớp nhưng độ nhạy của cảm biến có thể so sánh được với các cảm biến có cùng loại, cùng chức năng được chế tạo từ màng đa lớp rất phức tạp như cảm biến cấu trúc van – spin (VS), cảm biến từ điện trở xuyên hầm (TMR) đã công bố.
Khac Quynh Le
Xuan Toan Nguyen
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2018-01-05T02:42:08Z
2020-12-04T08:16:48Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2900
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2018-01-05T02:42:08Z
Thiết bị đo huyết áp liên tục không xâm nhập ứng dụng trong phẫu thuật dựa trên cảm biến từ - điện độ nhạy cao
Trong hồi sức bệnh nhân trong và sau phẫu thuật tim, việc theo dõi huyết áp liên tục là một trong các thông số rất quan trọng cần được theo dõi đảm bảo vận chuyển và phân bố khối lượng máu đến các cơ quan trong cơ thể. Một kỹ thuật đo đang được sử dụng trong bệnh viện hiện nay là thông qua đo trực tiếp áp lực máu truyền qua một màng rung. Để có thể sử dụng được phương pháp này, một ống thông (catheter) sẽ được luồn vào bên trong động mạch cổ tay hoặc động mạch phổi ở cổ để truyền máu dẫn đến màng rung và được duy trì trong suốt quá trình đo. Đây là phương pháp xâm lấn, đòi hỏi bác sỹ có trình độ và kinh nghiệm mới có thể sử dụng được kỹ thuật này. Bên cạnh đó, nguy cơ nhiễm trùng cũng rất cao khi thực hiện kỹ thuật này. Trong bài báo này, chúng tôi sử dụng một phương pháp đo hoàn toàn mới, cho phép theo dõi đồng thời huyết áp của bệnh nhân cũng như nhiều thông tin liên quan khác liên tục nhưng không xâm lấn sử dụng thông qua đo từ trường nhờ sử dụng một hệ thống nam châm vĩnh cửu và cảm biến đo từ trường độ nhạy cao dựa trên hiệu ứng từ-điện. Một số kết quả đo đạc đã được thực hiện trên các tình nguyện viên cho thấy triển vọng ứng dụng rất lớn của phương pháp đo này trong lĩnh vực y học sử dụng công nghệ cao hiện nay.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Van Tuan Nguyen
Khac Quynh Le
Xuan Toan Nguyen
Nguyen Thuc Vu
thucvn@vnu.edu.vn
Anh Tuan Phung
Ba Bien Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
2018-01-05T02:41:17Z
2018-01-05T02:41:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2901
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2018-01-05T02:41:17Z
Mô phỏng tối ưu cấu hình cho cảm biến từ trường hoạt động dựa trên hiệu ứng từ-điện
Trong xu thế của cuộc cách mạng công nghiệp 4.0, thị trường cảm biến đang ngày càng được mở rộng cả về số lượng và chủng loại, trong đó đặc biết chú ý đến cảm biến không dây. Trong số đó, phải kể đến cảm biến từ trường dựa trên hiệu ứng từ-điện tổ hợp của hai hiệu ứng từ giảo-áp điện (ME) quan sát được trên các loại vật liệu tổ hợp đa pha sắt từ-sắt điện. Trong bài báo này, nhằm nâng cao hiệu ứng ME để tăng cường độ nhạy cho cảm biến, chúng tôi tiến hành tối ưu cấu hình thiết kế cảm biến theo hướng cực tiểu hóa đóng góp trường khử từ sử dụng phần mềm để mô phỏng tính toán và chế tạo thực nghiệm một số cấu hình cảm biến để kiểm chứng kết quả mô phỏng tính toán thu được. Theo nguyên lý thiết kế này, từ thông sẽ được cải thiện khi chế tạo vật liệu theo cấu hình mạch từ khép kín không có khe từ theo đó ảnh hưởng của trường khử từ được suy giảm mạnh và do đó, hiệu ứng từ-điện đo được từ thực nghiệm cho thấy được tăng cường mạnh nhất. Các kết quả thu được tạo tiền đề cho các nghiên cứu chế tạo cảm biển cho nhiều ứng dụng trong lĩnh vực đo đạc độ nhạy và độ chính xác cao.
Van Tuan Nguyen
Khac Quynh Le
Anh Tuan Phung
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2018-01-04T09:53:11Z
2018-01-04T09:53:11Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2882
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2882
2018-01-04T09:53:11Z
Enhancing efficiency of dye-sensitized solar cell by mesoporous-macroporous TiO2 photoanode using ZnO template
Thi Thu Trang Pham
2018-01-04T09:52:36Z
2018-01-04T09:52:36Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2874
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2874
2018-01-04T09:52:36Z
Thiết bị đo huyết áp liên tục không xâm nhập ứng dụng trong phẫu thuật dựa trên cảm biến từ - điện độ nhạy cao
Thi Huong Giang Do
giangdth@vnu.edu.vn
2018-01-04T09:51:59Z
2018-01-04T09:51:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2875
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2875
2018-01-04T09:51:59Z
Nghiên cứu bào chế niosome làm hệ mang thuốc nano ứng dụng cho indomethacine
Thi Hien Le
lehien@vnu.edu.vn
Hong Nhung Luong
Van Thuan Tuong
tvthuan96@gmail.com
2018-01-04T09:51:26Z
2018-01-04T09:51:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2879
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2879
2018-01-04T09:51:26Z
Printable WO3 Electron Transporting Layer for Perovskite Solar Cells: Influence on Device Performance and Stability
Thi Thu Trang Pham
2018-01-04T09:51:07Z
2018-01-04T09:51:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2881
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2881
2018-01-04T09:51:07Z
Fabrication of Copper(I) Bipyridyl Complex Based Dye Sensitized Solar Cells
Thi Thu Trang Pham
2018-01-04T09:50:44Z
2018-01-04T09:50:44Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2880
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2880
2018-01-04T09:50:44Z
Fabrice Odobel and Johann Boucle, Toward Efficient Solid-State p-type Dye-sensitized Solar Cells: The dye matters
Thi Thu Trang Pham
2018-01-04T09:48:37Z
2018-01-04T09:48:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2878
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2878
2018-01-04T09:48:37Z
Nanomaterials: a guide to fabrication and applications
Van Hieu Nguyen
2018-01-04T09:48:06Z
2018-01-04T09:48:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2854
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2854
2018-01-04T09:48:06Z
SO SÁNH KHẢ NĂNG NHẠY KHÍ NH3 CỦA MÀNG TỔ HỢP PEDOT:PSS/GO/CNT VÀ P3HT/GO/CNT
Màng tổ hợp được chế tạo dựa cơ sở các chất bán dẫn loại P như các polymer dẫn PEDOT:PSS và P3HT, chúng được sử dụng như một chất nền để tạo sự kết dính với các thành phần khác trong tổ hợp nanocomposite như GO (Graphite Oxide) và MWCNT (Multiwall carbon nanotube), đây là các thành phần có hoạt tính xúc tác quan trọng trong tổ hợp với chất nền là polymer P3HT và PEDOT:PSS. Qua nghiên cứu và tổng hợp về nanocomposite, chúng tôi đã so sánh tính chất nhạy khí và chọn lọc của các tổ hợp này với nhau.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Long Lam
2018-01-04T09:47:03Z
2018-01-04T09:47:03Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2876
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2876
2018-01-04T09:47:03Z
Functional integral method in quantum field theory of plasmons in graphene
Nguyen Duc Duoc Phan
Van Hau Tran
2018-01-03T07:27:09Z
2018-01-03T07:27:09Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2873
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2873
2018-01-03T07:27:09Z
Nguồn gốc vi mô của hiện tượng bão hòa từ ở từ trường cao của các màng mỏng đa lớp Co/Pt
Duc Thang Pham
pdthang@vnu.edu.vn
D.Truong Q.
2018-01-03T07:25:27Z
2018-01-03T07:25:27Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2893
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2893
2018-01-03T07:25:27Z
Epitaxial-like growth of solution-processed PbZr0.4Ti0.6O3 thin film on single-crystal Nb-doped SrTiO3 substrate
PbZr0.4Ti0.6O3 (PZT) thin films have been conventionally fabricated on traditional silicon substrates with a platinum bottom electrode; however, as a consequence of unit cell mismatch, the films are difficult to form as an epitaxial-like growth. Hence, PZT films deposited on single-crystal niobium doped SrTiO3(111) substrates (Nb:STO) are promising to solve this issue thanks to the similar perovskite structure between PZT and STO. Essentially, Nb:STO material is a conductor, playing a part in both bottom electrode and epitaxial substrate. In this work, 200-nm-thick PZT films were successfully fabricated on Nb:STO substrates by a solution process. One obtained that PZT(111) peak started to appear on the Nb:STO substrate at a low annealing temperature of 450oC. Also, scanning electron microscopy observation shows smooth and homogeneous surface of PZT films on Nb:STO substrate with no grain boundary, which evidences for epitaxial-like growth of PZT thin films. Remnant polarization of 6 µC/cm2 and leakage current of 8×10-8 A were obtained at applied voltage of 5 V.
Ha Hoang
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2018-01-03T06:53:17Z
2018-01-03T06:53:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2872
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2872
2018-01-03T06:53:17Z
Khảo sát tính chất và tương tác ma sát điện giữa sợi nano polyvynyl clorua và nhôm
Hai Phan
Duc Thang Pham
pdthang@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2018-01-03T06:52:42Z
2018-01-03T06:52:42Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2883
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2883
2018-01-03T06:52:42Z
Influence of size and shape of sub-micrometer light scattering centers in ZnO-assisted TiO2 photoanode for dye-sensitized solar cells
Thi Thu Trang Pham
2017-12-27T01:25:17Z
2018-01-10T08:37:30Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2860
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2860
2017-12-27T01:25:17Z
Enhancement of the sensitivity of magnetic field sensor based on anisotropic magetoresistance effect in NiFe thin films
The sensitivity magnetic sensors have become essential for applications in many fields such as biomedicine, computer memories, geophysics and etc. It is known that the sensitivity of magnetic anisotropy sensor depends on current density as well as the rotation of the magnetic moments corresponded to the external magnetic field. In this study, we fabricated and investigated a number of different configurations of resistor bar in the Wheatone bridge sensor. The samples were made in magnetic field pins with varying intensity from 0 to 900 Oe. Furthermore, different shapes of resistor, as in circle, rectangle, ellipse, were fabricated with the film thickness of 15 nm. The analyzed results indicated that the rotation of the magnetic moments occurs rapidly and sharp in the small magnetic field (0 - 3 Oe) with samples fabricated in the high magnetic field pinned. The strong magnetic anisotropy was also observed in the rectangular configuration. In addition, the sensors have been optimized for measuring small magnetic field.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Khac Quynh Le
Viet Cuong Le
cuonglv@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2017-12-27T01:24:16Z
2017-12-27T01:24:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2859
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2859
2017-12-27T01:24:16Z
CONJUGATE POLYMER PEDOT:PSS INCORPORATED WITH NANO-PARTICLES USED FOR GAS SENSIN
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) incorporated with nanocrystalline TiO2 (PEDOT:PSS+nc-TiO2) and silver nanoparticles (PEDOT:PSS+AgNP) films were prepared by a spin-coating technique. AFM and FE-SEM surface morphologies, UV-Vis spectra and NH3 gas sensing characteristic of the composite films were studied. The results showed that the PEDOT:PSS+nc-TiO2 film with a content of 7.0 wt.% of TiO2 is suitable for both the hole transport layer and the NH3 sensing characteristic. The response time of the sensor made from this composite film reached a value as fast as 30 s. The rapid response to NH3 gas could be attributed to the efficient movement of holes as the major charge carriers in the PEDOT:PSS+nc-TiO2 composite films. Useful applications in the organic electronic devices like light emitting diodes and gas thin film sensors can be envisaged.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Long Lam
2017-12-27T01:23:22Z
2017-12-27T01:23:22Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2858
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2017-12-27T01:23:22Z
Characterization of Humidity Sensing of Polymeric GrapheneQuantum-Dots Composites Incorporated with Silver Nanowires
Graphene quantum dots (GQDs) were synthesized and incorporated with polyethylenedioxythiophene:poly(4-styrenesulfonate) (PEDOT:PSS), Ag nanowires (AgNWs) to form a composite that can be used for enhancement of relative humidity (RH%) sensing. The composite films contained bulk heterojunctions of AgNW/GQD and AgNW/PEDOT:PSS. The sensors made from the composites responded well to relative humidity in a range from 10% to 50% at room temperature. With an AgNWs content ranging from 0.2 wt.% to 0.4 wt.% and 0.6 wt.%, the sensitivity of the relative humidity sensing devices based on AgNWs-doped GQDs+PEDOT:PSS composites was increased from 5.5% to 6.5 % and 15.2 %, respectively. The response time of the composite sensors was much improved due to AgNWs doping in the composites. For the 0.6 wt.% AgNWs-doped GQDs+PEDOT:PSS films, the best value of the recovery time was found to be of 30 s.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Long Lam
2017-12-27T01:22:47Z
2017-12-27T01:22:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2857
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2857
2017-12-27T01:22:47Z
Optical and NH3 Gas Sensing Properties of Hole-Transport Layers Based on PEDOT: PSS Incorporated with Nano-TiO2
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) incorporated with nanocrystalline TiO2 powder (PEDOT:PSS+nc-TiO2) films were prepared by spin-coating technique. SEM surface morphology, UV-Vis spectra and NH3 gas sensing of were studied. Results showed that the PEDOT:PSS+nc-TiO2 film with a content of 9.0 wt% of TiO2 is most suitable for both the hole transport layer and the NH3 sensing. The responding time of the sensor made from this composite film reached a value as fast as 20 s. The rapid responsiveness to NH3 gas was attributed to the efficient movement of holes as the major charge carriers in PEDOT:PSS+nc-TiO2 composite films. Useful applications in organic electronic devices like light emitting diodes and gas thin film sensors can be envisaged.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Long Lam
2017-12-27T01:21:07Z
2017-12-27T01:21:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2855
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2855
2017-12-27T01:21:07Z
Nghiên cứu ảnh hưởng của dây nano bạc trong vật liệu tổ hợp P3HT/GO nhạy khí NH3
Sử dụng phương pháp hóa dung dịch, vật liệu tổ hợp nano dưới dạng màng được chế tạo ra từ polymer dẫn điện P3HT kết hợp ôxit graphite và dây nano bạc (P3HT/GO/Ag NW). Độ nhạy khí của vật liệu P3HT/GO/Ag NW được điều chỉnh bằng cách thay đổi độ dày của màng. Khảo sát hình thái học bề mặt và tính chất nhạy khí của màng tổ hợp trên cho thấy tiếp xúc giữa dây nano bạc với các khối GO trong polymer đóng vai trò cầu dẫn hạt tải sinh ra trong quá trình hấp phụ khí. Điều này làm tăng độ nhạy của cảm biến khí NH3 trên cơ sở màng tổ hợp P3HT/GO/Ag NW đáp ứng yêu cầu giám sát lượng khí này dư thừa trong môi trường với nồng độ trong dải 10100 ppm.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Long Lam
2017-12-27T01:19:45Z
2018-01-10T08:42:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2850
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2017-12-27T01:19:45Z
Mô phỏng, tính toán độ dày tối ưu của vật liệu tổ hợp cấu trúc nano hấp thụ năng lượng sóng điện từ
Nghiên cứu tối ưu hóa khả năng hấp thụ năng lượng sóng điện từ trong các vật liệu tổ hợp điện môi - từ đang được quan tâm nhiều trong những năm vừa qua. Trong báo cáo này, chúng tôi trình bày một số kết quả nghiên cứu ban đầu về mô phỏng, tính toán để xác định độ dày tối ưu cho một số vật liệu tổ hợp có cấu trúc nano khác nhau. Chương trình tính được xây dựng trên cơ sở các biểu thức tính toán và các phương trình liên quan đến đặc trưng hấp thụ sóng điện từ của hệ vật liệu tổ hợp và phần mềm lập trình Matlab. Các thông số về hằng số điện môi, độ từ thẩm của các vật liệu và tần số/bước sóng cần hấp thụ cũng sẽ được sử dụng. Việc mô phỏng đã được tính toán cho 3 hệ vật liệu tổ hợp gồm các hạt nano CoFe2O4, ZnFe2O4, Zn0,5Co0,5Fe2O4 với chất nền polymer Cellwax plus với tỉ lệ pha trộn là 50% về thể tích. Kết quả cho thấy các vật kiệu tổ hợp trên sẽ hấp thụ tối ưu với các chiều dày 2,5; 2,75 v à 2 mm tương ứng. Bên cạnh đó, phần mền với giao diện thân thiện và tiện ích còn có thể phát triển thêm để ứng dụng trong nghiên cứu và sản xuất vật liệu hấp thụ năng lượng sóng điện từ nhằm phục vụ các lĩnh vực y-sinh học, bảo vệ môi trường và khoa học kỹ thuật quân sự.
Dang Co Nguyen
Van Hiep Tran
Duc Huy Tran
Quoc Viet Dong
Viet Cuong Le
cuonglv@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
2017-12-27T01:18:25Z
2018-01-10T08:34:48Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2852
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2017-12-27T01:18:25Z
NGHIÊN CỨU CHẾ TẠO CÁC NGUỒN VI NĂNG LƯỢNG VĨNH CỬU DỰA TRÊN VẬT LIỆU FePt
Các vi cấu trúc từ ngoài việc được sử dụng trong các cơ cấu vi chấp hành, vi hệ thống, còn đang được dùng như các nguồn năng lượng nhỏ, bền vững theo thời gian nhằm ứng dụng trong y sinh. Các vi cấu trúc từ này thường đòi hỏi phải có kích thước nhỏ, tạo ra được không gian từ trường với cường độ từ trường và độ biến thiên từ trường mong muốn. Trong bài báo này, vi cấu trúc từ FePt được nghiên cứu chế tạo bằng phương pháp phún xạ kết hợp với công nghệ quang khắc. Vi cấu trúc từ này gồm các hình khối có diện tích 60×60µm2 và chiều dày 500 nm, phân bố cách nhau 40 µm trên đế Si có diện tích 1×1 cm2. Cấu trúc từ chế tạo được này có dị hướng từ vuông góc với mặt phẳng đế với các giá trị đặc trưng đo theo phương vuông góc như lực kháng từ HC┴ ~ 4 kG và độ từ dư MR┴ ~ 200 emu/cm3. Mỗi vi cấu trúc từ này có thể tạo ra một nguồn năng lượng với giá trị lên đến 126 kJ/m3, có tiềm năng cho ứng dụng trong bắt giữ các phần tử kích thước micro-nano.
Viet Cuong Le
cuonglv@vnu.edu.vn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Doan Thanh Nguyen
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Duy Truong Quach
Duc Thang Pham
pdthang@vnu.edu.vn
2017-12-25T04:18:58Z
2018-01-10T08:35:54Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2848
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2017-12-25T04:18:58Z
CHẾ TẠO THIẾT BỊ ĐO ĐẶC TRƯNG MỘT SỐ LINH KIỆN BÁN DẪN PHỤC VỤ TRONG HỌC TẬP VÀ GIẢNG DẠY
Thiết bị được thiết kế dựa trên vi điều khiển Atmega328 kết hợp kết hợp với mạch cấp dòng và thu nhận tín hiệu điện áp từ các linh kiện bán dẫn và được ghép nối với máy tính để thu nhận và xử lý tín hiệu thông qua cổng giao tiếp chuẩn UART và phần mềm Labview. Thiết bị sẽ xác định giá trị Ungưỡng của các linh kiện bán dẫn và bước sóng của các linh kiện phát quang, pin mặt trời. Công suất tiêu thụ của thiết bị ~0.3W/h, độ chính xác của thiết bị so với các thiết bị thương mại nhập khẩu (giá thành rất cao) có sai số 10 nm khi đo giá trị bước sóng và 0.1 mV khi đo giá trị Ungưỡng của các linh kiện bán dẫn
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Duc Huy Tran
cmcbkit@gmail.com
Viet Cuong Le
cuonglv@vnu.edu.vn
Van Hiep Tran
Dang Co Nguyen
Ngoc Huyen Nguyen
2017-12-25T04:18:35Z
2018-01-10T08:34:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2849
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2849
2017-12-25T04:18:35Z
NGHIÊN CỨU CHẾ TẠO MẠCH GIÁM SÁT HỆ THỐNG CHIẾU SÁNG LED DÙNG TRONG NÔNG NGHIỆP
Ứng dụng công nghệ cao đang là yêu cầu tất yếu của mỗi nền nông nghiệp hiện đại. Một điều kiện quan trọng và có tính tiên quyết trong thành công của nông nghiệp công nghệ cao đó là hệ thống chiếu sáng cung cấp photon ánh sáng cho quá trình quang hợp của cây xanh. Trong báo cáo này là kết quả thiết kế, chế tạo một hệ thống chiếu sáng thông minh được tính toán dựa trên việc thu nhận tín hiệu của cảm biến ánh sáng. Các cảm biến có thời gian đáp ứng < 100 ms, chuẩn hóa với hệ thống chiếu sáng LED tiêu chuẩn trong nông nghiệp (bước sóng 450 nm và 640 nm), được tích hợp với mạch giám sát và thử nghiệm tại Khoa Vật lý kỹ thuật và Công nghệ nano, Trường Đại học Công nghệ. Hệ thống được thiết kế dựa trên sự kết hợp giữa CPU nhúng thuộc họ ARM và vi điều khiển họ AVR cùng với các hệ thống SoC và được kết nối với mạng internet để thu nhận và xử lý tín hiệu. Hệ thống hoạt động ổn định ở các điều kiện khác nhau, phù hợp với khí hậu ở Việt Nam. Hệ thống thiết bị này cho phép giám sát và điều khiển tự động hệ thống chiếu sáng trong nông nghiệp và là một giải pháp tiết kiệm năng lượng nói chung.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Van Hiep Tran
Dang Co Nguyen
Duc Huy Tran
Viet Cuong Le
cuonglv@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
2017-12-25T03:34:00Z
2018-01-10T08:33:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2846
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2846
2017-12-25T03:34:00Z
Nghiên cứu, chế tạo cẩm biến từ dựa trên hiệu ứng Hall phẳng(PHE)
Hệ các cảm biến đo từ trường dạng chữ thập dựa trên hiệu ứng Hall phẳng (PHE), cấu trúc màng mỏng đơn lớp Ni80Fe20 đã được chúng tôi nghiên cứu và chế tạo dựa trên thiết bị phún xạ sputtering ATC-2000FC. Các nghiêncứu theo hướng tối ưu hóa cấu trúc, hình dạng cảm biến với mục đích tăng cường độ nhạy theo từ trường, bao gồm cảm biến có các kích thước: 1×5 mm 202, 1×7 mm2, 1×10 mm2 và có độ dày lớp màng mỏng từ tính khác nhau 5, 10, 15 nm. Kết quả nghiên cứu cho thấy, độ nhạy của cảm biến phụ thuộc mạnh vào tính dị hướng hình dạng và bề dày của lớp NiFe. Tính dị hướng hình dạng càng lớn, bề dày lớp màng NiFe càng mỏng thì độ nhạy cảm biến càng cao. Độ nhạy lớn nhất đạt được trên cảm biến chữ thập có kích thước 1×10 mm, có bề dày 5 nm cho giá trị S(H)= 0,1 mV/Oe, tại dòng cấp 5 mA, tương đương với độ nhạy 20 mΩ/Oe. Với qui trình công nghệ chế tạo đơn giản, cấu trúc màng đơn lớp nhưng độ nhạy của cảm biến có thể so sánh được với các cảm biến có cùng loại, cùng chức năng được chế tạo từ màng đa lớp rất phức tạp như cảm biến cấu trúc van-spin (VS),cảm biến từ điện trở xuyên hầm (TMR), từ điện trở dị hướng (AMR) đã công bố.
Khac Quynh Le
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Xuan Toan Nguyen
Tien Dung Tran
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2017-12-11T09:39:44Z
2017-12-11T17:29:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2749
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2749
2017-12-11T09:39:44Z
Cải tiến mã khối hạng nhẹ họ LED và Neokeon
Họ mã khối Neokeon được đề xuất vào năm 2000 bởi bốn nhà khoa học Daemen, Peeters, Van Assche và Rijme. Môt trong các ưu điểm của Neokeon đó là nhỏ gọn, nhanh chóng triển khai trên phần cứng chuyên dụng, ngoài ra nó còn yêu cầu về bộ nhớ RAM rất thấp và hoạt động hiệu quả trên đa nền tảng. Nhưng trong thuật toán họ Neokeon sử dụng rất nhiều các ánh xạ tuyến tính và sử dụng khóa trực tiếp trong khi mã hóa mà không thông qua những phép biến đổi làm việc trước với khóa. Do đó, Neokeon dường như khá mong manh trước những dạng thám mã tuyến tính. LED là thuật toán được thiết kế và đề xuất bởi Guo, Peyrin, Poschmann và Robshaw vào năm 2011, là một trong những thuật toán mã hóa nhẹ khá mới. Kích thước khối tin 64-bit với hai biến thể của khóa lần lượt là 64-bit và 128-bit. Thiết kế của LED có nhiều điểm tương đồng với thuật toán AES. Trong bài báo này, chúng tôi thực hiện cải tiến thuật toán LED và Neokeon, đối với Neokeon chúng tôi ngẫu nhiên hóa dữ liệu tại những ánh xạ tuyến tính và thao tác làm việc với khóa, nhằm mục
đích nâng cao độ an toàn của Neokeon trước các thám mã tuyến tính nhưng không làm thay đổi nhiều những ưu điểm sẵn có của Neokeon, đối với LED chúng tôi thực hiện cải tiến xử lý dữ liệu trong khối step của
thuật toán này.
Keywords-mã khối hạng nhẹ; led; neokeon; tuyến tính
Phe Do Le
dolp@vnu.edu.vn
Trung Thuc Le
thuclt12a@gmail.com
Manh Trung Mai
mmtrung@unti.edu.vn
Thi Len Le
phalebl@gmail.com
Khac Hung Nguyen
nguyenhung.tlh@gmail.com
Thi Hang Nguyen
themoonit@gmail.com
Van Manh Tran
manhtv@outlook.com
2017-11-29T03:49:10Z
2017-11-29T03:49:10Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2680
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2680
2017-11-29T03:49:10Z
Preparation and characterization of niosome encapsulated curcumin
Niosome encapsulated curcumin were prepared by ethanol injection method with continuous ethanol evaporation using non-ionic surfactant span 80, cholesterol and curcumin. Curcumin-niosomes were purified from unencapsulated curcumin and impurities by size exclusion chromatography. Field emission scanning electron microscopy (FE-SEM) demonstrated that curcumin-niosomes had relatively uniform, spherical shapes with estimated diameters of 50 nm. Dynamic light scattering (DLS) analysis indicated that the size of particles hardly depended on the solvent evaporation time. Niosomal encapsulation efficiency of curcumin (EE), which was determined by fluorospectrometer, incredibly increased after 2-hour ethanol evaporation. It reached the highest value of 98% after 5 hours of ethanol evaporation for the mixture of span80, cholesterol, curcumin in a molar ratio of 45: 30: 1.
Thi Hien Le
lehien@vnu.edu.vn
Thi Yen Nguyen
hoangyen666.yh@gmail.com
Van Thuan Tuong
tvthuan96@gmail.com
Thi Hai Yen Tran
tranyen82@gmail.com
Thi Huyen Vu
huyenbionano@gmail.com
2017-11-16T04:29:00Z
2017-11-16T04:29:00Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2634
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2634
2017-11-16T04:29:00Z
Huge on-Current Ferroelectric-Gate Thin Film Transistor with Solution-Processed Indium Tin Oxide Channel
We have demonstrated ferroelectric-gate thin film transistors (FGTs) using solutionprocessed
indium tin oxide (ITO) film as an oxide-semiconductor channel and Pb1.2Zr0.4Ti0.6O3
ferroelectric film as a gate insulator on a poly-crystalline 100-nm-STO/SiO2/Si substrate or a
single-crystalline STO(111) wafer. The FGTs show a clear memory function with an on/off
current ratio of more than 105 and a memory window of 2 V. It is interesting that even using
solution-processed ITO channel, the saturated “on” current in the FGT reached as high as 4.6 mA
at operation voltages of 8 V, corresponding to a field-effect mobility of 8.0 cm2/Vs, for the case of
single-crystalline STO(111) wafer. The large “on” current is mainly due to the huge induced
charge of the ferroelectric gate, compensated to the small mobility of the ITO channel.
Hong Minh Do
Thi Huyen Trang Vu
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-16T04:26:31Z
2017-11-16T04:26:31Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2633
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2017-11-16T04:26:31Z
STUDY ON ITO THIN FILMS PREPARED BY
MULTI-ANNEALING TECHNIQUE
Indium tin oxide (ITO) thin films have been successfully prepared by a solution process
followed by a multi-annealing method. In this study, we focus on the use of multi-annealing
method, for which each layer was annealed at a suitable temperature, instead of a conventional
annealing way, by means of a rapid thermal annealing system, in order to improve the film
quality. The crystalline structure and surface morphology of the ITO thin films were investigated
by using X-ray diffraction (XRD) spectrometer, atomic force microscope (AFM) and scanning
electron microscope (SEM). It has been obtained that all of ITO films exhibit a single phase with
(200)- and (444)-preferred orientations. The AFM and SEM observations show that the particle
size of ITO films was about 10 nm and the ITO film thickness was 180 nm, respectively. In
sequence, the electrical properties of ITO thin films were evaluated by using four-point probe
and Hall effect measurement methods, and the optical properties were investigated by UV/VIS
spectrometer. The achievement results show that the optimum ITO films possessed electrical
resistivity of 2.6 × 10-3 Ωcm and transparency higher than 90%, which strongly supports to the
application of electrode in solar cell, LED or transistor devices from viewpoints of low-cost
production and low-energy consumption.
Quang Hoa Nguyen
Thi Xuyen Nguyen
Quoc Viet Vuong
Thi Huyen Trang Vu
Ha Hoang
Thi Thanh Tam Hoang
Thi Dung Vu
Van Dung Tran
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-16T04:26:10Z
2017-11-16T04:26:10Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2632
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2632
2017-11-16T04:26:10Z
INVESTIGATION ON STRUCTURAL AND FERROELECTRIC PROPERTIES OF Bi3.25La0.75Ti3O12 THIN FILMS
Lanthanum doped bismuth titanate (Bi3.25La0.75Ti3O12 abbreviated as BLT) has been known
as one of typical materials for Bi-layered perovskite structure which possess several unique
properties such as good fatigue with metal electrode and stable remanent polarization, hence it
has potential applications in ferroelectric random access memory. In this work, the BLT thin
films were fabricated on Pt/TiO2/SiO2/Si substrates by using a solution process, and then their
features including crystal structure, surface morphology, and electrical properties were
characterized by using X-ray diffraction system (XRD), scanning electron microscopy (SEM),
and electrical measurement system (Radiant Precision LC 10), respectively. The obtained results
point out that the BLT thin film annealed at 725oC is mostly optimum from a viewpoint of film
quality and ferroelectricity. In particular, the optimum BLT thin film having a thickness of 200
nm does not contain any cracks on the sample surface, and the grain size is closed to 400 nm from
SEM observation. XRD patterns imply that the BLT thin film had stoichiometric structure with
preferred orientations of (117) and (006), when annealed at temperatures higher than 725oC. In
addition, we found the influence of La (0.75) dopping on c-axis-oriented growth of BLT thin
films is clear from the structural analysis. The remanent polarization of optimum BLT thin film is
approximately 10 µC/cm2, but the ferroelectric hysteresis loops are not saturated at low applied
voltages.
Van Dung Tran
Ha Hoang
Thi Thanh Tam Hoang
Thi Dung Vu
Van Dung Nguyen
Hong Minh Do
Thi Huyen Trang Vu
Quang Hoa Nguyen
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-16T02:41:03Z
2017-11-16T02:41:03Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2637
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2637
2017-11-16T02:41:03Z
Photoluminescence and I -V Characteristics of
Blended Conjugated Polymers/ZnO Nanoparticles
Abstract: The investigation of photoluminescence and current-voltage (I-V) characteristics of the
MEH-PPV/PVK blended polymers doped with ZnO nanoparticles (ZnO NPs). First, PVK polymers were mixed with MEH-PPV in respect to the mass-ratio of 100:15, respectively. And
then the MEH-PPV/PVK composites were doped with ZnO NPs with the mass-ratio of 10 wt%, 15 wt% and 20 wt% of total weight blended polymers. Polymer light-emitting diodes (PLEDs), based on a hybrid composite, having structure of ITO/ MEH-PPV/PVK/ZnO/Al were made by spincoated,and subsequently vacuum-thermally evaporated.
UV-Vis absorption, photoluminescence properties, SEM micrographs of the hybrid compositelayer as well as I -V characteristics of the PLED based on the MEH-PPV/ZnO-and PVK/ZnOheterojunction were investigated. Results obtained show that the turn-on voltage of the polymers/ZnO-based PLED is lower than that of the polymers-based PLED without doped ZnO NPs. This is due to the Auger-assisted energy up-conversion process occurring at the polymers/ZnO-heterojunction that could enhance the luminescence efficiency of the PLED.
Keywords: PLED, photoluminescence efficiency, MEH-PPV, PVK, SEM, spin coating, thermal
vacuum evaporation
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
2017-11-09T03:23:15Z
2017-11-09T03:23:15Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2626
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2626
2017-11-09T03:23:15Z
Solution-processed doping and undoping zinc-oxide and copper-oxide thin films
Zinc-oxide (ZnO) and copper-oxide (CuO) based thin films have attracted a huge attention owing to controllable electrical conductivity and low-cost materials for manufacturing electronic and photonic devices. In this work, we have characterized on physical properties of undoped and doped (ex.: Ag, Al) ZnO and CuO thin films, prepared by using a solution process. For formation of precursor solution, zinc/copper nitrate hexahydrate (original or doping), water and citric acid were used as metal salt, solvent and stabilizer, respectively. After that, using the precursors mixed, ZnO/CuO thin films were spin-coated on glass substrates followed by an annealing process below 550oC. Structural, morphological, optical and electrical properties of the thin films were, in turn, evaluated by using X-ray diffraction, scanning electronic microscopy, UV-vis, and four-probe measurement systems. Achievement results show that, when annealing temperatures increased from 450°C to 550°C, the thin films were oriented more preferentially along (100) (002) and (102) directions. ZnO based thin films were relatively porous, and whose band-gap energy was closed to 3.2 eV. In addition, characterization on CuO thin films will be discussed in this conference.
Van Dung Nguyen
Quang Hoa Nguyen
Van Dung Tran
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-09T03:22:25Z
2017-11-09T03:22:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2625
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2625
2017-11-09T03:22:25Z
Nanoimprinting Lithography Patterned Thin-Film Transistors with Sn-Doped Indium Oxide Channel
Sn-doped indium oxide (ITO) semiconductor thin films have been extensively applied in electronic devices such as photonics and thin film transistors, owing to high transparence and controllable mobility and conductivity. Past few years, we reported a success to demonstrate a ferroelectric thin-film transistor (FeTFT) by using all solution processes, in which 450oC ITO thin film used as a channel, and perovskite-structured thin film used as a gate insulator [1]. In sequence, sub-100 nm FeTFT patterned by using electron beam lithography [2] and low temperature process of FeTFT [3] have been verified as well. In this study, we succeed to fabricate sub-micro and sub-100 nm FeTFTs with precise alignment, whose typical operations possess an on/off current ratio of 4 to 5 orders, memory window of about 1.5 V, and on-current amplitude of several 100 A levels. Therefore, we present achievement on FeTFT by using the patterns of nanoimprinting lithography in micrometer and nanometer scales, and compare with conventional techniques, in this conference.
Van Loi Nguyen
Van Loi Vu
Quoc Huy Hoang Bui
Hong Minh Do
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-09T03:21:27Z
2017-11-09T03:21:27Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2624
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2624
2017-11-09T03:21:27Z
Low-temperature PZT thin-film ferroelectric memories fabricated on SiO2/Si and glass substrates
In a ferroelectric-gate thin film transistor memory (FGT) type structure, the gate-insulator layer is
extremely important for inducing the charge when accumulating or depleting. We concentrated on the
application of low-temperature PZT films crystallized at 450, 500 and 550 �C, instead of at conventional
high temperatures (�600 �C). Investigation of the crystalline structure and electrical properties indicated
that the PZT film, crystallized at 500 �C, was suitable for FGT fabrication because of a high (111) orientation,
large remnant polarization of 38 mC/cm2 on SiO2/Si substrate and 17.8 mC/cm2 on glass, and low
leakage current of 10�6 A/cm2. In sequence, we successfully fabricated FGT with all processes below
500 �C on a glass substrate, whose operation exhibits a memory window of 4 V, ON/OFF current ratio of
105, field-effect mobility of 0.092 cm2 V�1 s�1, and retention time of 1 h.
Hong Minh Do
Van Loi Nguyen
Huu Duc Nguyen
ducnh@vnu.edu.vn
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-09T03:19:54Z
2017-11-09T03:19:54Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2627
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2627
2017-11-09T03:19:54Z
CHARACTERIZATION ON CuO THIN FILMS DEPOSITED BY SOLUTION PROCESS
Copper oxide (CuO) thin films have been successfully prepared by a solution process. In this study, we find out an optimum condition to form CuO precursors solution, as well as to fabricate CuO thin fims. To improve the films quality, analysis on crystalline structure and surface morphology of CuO thin films was systematically carried out by using X-ray diffraction (XRD) spectrometer and scanning electron microscope (SEM). We obtained that whole CuO thin films exhibit a single phase with monoclinic structure. The SEM images show that the particle size of CuO thin films was about 20÷30 nm, and the thickness of CuO thin film was 180 nm. In sequence, the electrical property of CuO thin films was evaluated by using four-point probes measurement, and the optical property was investigated by UV/VIS spectrometer. We achieved that the optimum CuO thin films possessed an electrical resistivity of 9.02 kΩ/. Also, from absorbance spectra, we extracted that band-gap energy of CuO thin films was ranged from 2.20 eV to 2.30 eV.
Quang Hoa Nguyen
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2017-11-08T07:18:14Z
2017-11-08T07:18:14Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2621
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2621
2017-11-08T07:18:14Z
Interface Charge Trap Density of Solution Processed Ferroelectric Gate Thin Film Transistor Using ITO/PZT/Pt Structure
The conductance method was applied to investigate the interface charge trap density
(Dit) of solution processed ferroelectric gate thin film transistor (FGT) using indium-tin
oxide (ITO)/ Pb(Zr,Ti)O3 (PZT)/Pt structure. As a result, a large value of Dit of MFS
capacitor, i.e., Pt/PZT/ITO, was estimated to be 1.2 × 1014 eV−1 cm−2. This large Dit
means that an interface between the ITO layer and the PZT layer is imperfect and it is
one of themain reasons for the poor memory property of this FGT. By using transmission
electron microscopy (TEM), this imperfect interface was clearly observed. Thus, it is
concluded that improvement of this interface is critical for better memory performance.
Van Thanh Pham
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
Miyasako Takaaki
Trong Tue Phan
Tokumitsu Eisuke
Shimoda Tatsuya
2017-11-08T07:15:36Z
2017-11-08T07:15:36Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2620
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2620
2017-11-08T07:15:36Z
Switchable Voltage Control of the Magnetic Anisotropy in Heterostructured Nanocomposites of CoFe/NiFe/PZT
In this work, we study the magnetic properties of a CoFe/NiFe/PZT heterostructured nanocomposite
that is affected by the strain in the PZT substrate when a voltage in the range from –250
to 250 V is applied. An interesting electric-voltage-controlled magnetic anisotropy, with a relative
increase in magnetization up to above 100%, is observed. This brings a new challenge to operate a
low-power-consuming spin electronic device. We also utilize a theoretical model based on interfacecharge-
mediated and strain-mediated magnetic-electric coupling to understand the change in the
magnetic properties of the investigated material.
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Ba Doan Nguyen
Huy Tiep Nguyen
Viet Cuong Le
cuonglv@vnu.edu.vn
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
Duc Thang Pham
Dong-Hyun Kim
2017-11-06T05:20:10Z
2017-11-06T05:20:10Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2610
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2610
2017-11-06T05:20:10Z
Nghiên cứu bào chế niosome làm hệ mang thuốc nano ứng dụng cho indomethacine
Một trong những hướng phát triển mạnh của công nghệ nano sinh học là nghiên cứu chế tạo và ứng dụng các chất mang nano (nanocarier) để phân phối các chất có hoạt tính sinh học với mục đích tăng tính sinh khả dụng của chúng. Niosome là một dạng tiểu phân nano mang thuốc có cấu trúc dạng túi với nhân bên trong là một khoang chứa nước và lớp vỏ là màng kép chất hoạt động bề mặt không mang điện. Indomethacin là thuốc kháng viêm không steroid dùng để điều trị các bệnh về cơ xương khớp. Do indomethacin ít tan trong nước, độ thẩm thấu qua da không cao và có thể gây kích ứng với da, nên đóng gói indomethacine bằng niosome sẽ góp phần cải thiện các hạn chế của thuốc này khi bôi ngoài da. Niosome-indomethacine được tạo thành bằng phương pháp tiêm ethanol từ các tá dược span 80, cholesterol và dược chất indomethacin ở nhiệt độ 65°, sau đó được tinh sạch bằng kỹ thuật sắc ký lọc gel. Thành phần hóa học tiểu phân được xác định bằng phổ hồng ngoại biến đổi chuỗi Fourier (FTIR). Ảnh chụp bằng kính hiển vi điện tử quét phát xạ trường (FESEM) cho thấy tiểu phân niosome-indomethacin có dạng hình cầu và kích thước tương đối đồng đều khoảng 50 nm. Phương pháp phân tích phổ hấp thụ UV-vis cho thấy hiệu suất nạp thuốc đạt tối đa 97% sau 1 giờ chế tạo với tỉ lệ số mol span 80: cholesterol: indomethacin là 60: 40: 4.5.
Thi Hien Le
lehien@vnu.edu.vn
Hong Nhung Luong
nhungluong223@gmail.com
Thi Yen Nguyen
hoangyen666.yh@gmail.com
Van Thuan Tuong
tvthuan96@gmail.com
Thi Hai Yen Tran
tranyen82@gmail.com
2017-07-24T04:00:09Z
2017-07-24T04:00:09Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2561
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2561
2017-07-24T04:00:09Z
Annual Scientific Report 2017 (ASR 2017)
The VNU-UET Annual Scientific Report has been started from 2016.
Xuan Tu Tran
tutx@vnu.edu.vn
Xuan Hieu Phan
hieupx@vnu.edu.vn
Duc Tan Tran
tantd@vnu.edu.vn
Manh Thang Pham
thangpm@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Bao Son Pham
sonpb@vnu.edu.vn
2017-06-29T15:14:04Z
2017-06-29T15:14:04Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2542
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2542
2017-06-29T15:14:04Z
Na-doped La 0.7 Ca 0.3 MnO 3 compounds exhibiting a large magnetocaloric effect near room temperature
Dinh Chi Linh
Nguyen Thi Ha
Huu Duc Nguyen
ducnh@vnu.edu.vn
Le Viet Bau
Nguyen Manh An
Seong-Cho Yu
Tran Dang Thanh
2017-06-10T11:28:30Z
2017-06-10T11:28:30Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2469
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2017-06-10T11:28:30Z
Polymer dẫn và điôt phát quang hữu cơ
Trong gần 15 năm lại đây nhóm chúng tôi đã tiến hành các nghiên cứu khoa học về vật liệu và linh kiện trên cơ sở polymer dẫn và tổ hợp nanô polymer với ôxit kim loại. Các loại linh kiện được tập thể khoa học tập trung nghiên cứu và triển khai ứng dụng là OLED, pin mặt trời hữu cơ (OSC) và sensor màng mỏng hữu cơ (OTFS). Nhằm phần nào đáp ứng nhu cầu người đọc về vật liệu polymer và linh kiện vi điện tử hữu cơ đầy triển vọng ứng dụng này, tác giả tập trung biên soạn sách chuyên khảo “Polymer dẫn và điôt phát quang hữu cơ”. Sách được biên soạn một cách chọn lọc, cập nhật phân tích các công trình khoa học của nhiều tác giả trên thế giới và một phần đáng kể từ các công trình khoa học, luận án tiến sĩ của các thành viên trong Nhóm. Sách này có thể làm tài liệu học tập, tra cứu, tham khảo trong lĩnh vực chuyên sâu về polymer dẫn và OLED.
Sách gồm Phần mở đầu, 5 chương và Kết luận. Các chương là:
CHƯƠNG I. POLYMER DẪN ĐIỆN VÀ LINH KIỆN PHÁT QUANG HỮU CƠ
CHƯƠNG 2. CÁC KĨ THUẬT SỬ DỤNG TRONG CÔNG NGHỆ CHẾ TẠO VÀ ĐẶC TRƯNG TÍNH CHẤT VẬT LIỆU VÀ LINH KIỆN OLED
CHƯƠNG 3. TÍNH CHẤT CỦA VẬT LIỆU VÀ LINH KIỆN OLED THUẦN KHIẾT POLYMER
CHƯƠNG 4. VẬT LIỆU TỔ HỢP CẤU TRÚC NANÔ KHỐI VÀ LINH KIỆN OLED
CHƯƠNG 5. VẬT LIỆU VÀ LINH KIỆN OLED PHÁT XẠ NGƯỢC
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-12-31T14:34:59Z
2016-12-31T14:34:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2339
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2016-12-31T14:34:59Z
The mechanical effect and physics properties of ZnO nanoparticles in nanocomposite organic solar cell P3HT:PCBM
Doping particles into composite materials can mechanically stabilize these structure. At nanoscale, doping nanoparticles not only strengthen the material structure but also improve some mechanical and physical properties of materials. In this work, we will investigate the role of ZnO nanoparticles (NPs) doping into the nanocompsite multilayer organic solar cell (OSC) with the active layer composed of P3HT:PCBM. ZnO NPs is an economical ingredient for some applications in organic solar cell devices. They not only enhance significantly the absorption of the incident light but also make the composite nanostructure in OSC more durable. The absorption properties such as the absorption intensity can be explained by Mie scattering theory and studied numerically using finite element method (FEM). The mechanical effects can be illustrated by Young and Bulk modulus.
Dinh Long Dang
ddlong@vnu.edu.vn
Dinh Duc Nguyen
ducnd@vnu.edu.vn
2016-12-31T14:30:59Z
2016-12-31T14:30:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2336
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2016-12-31T14:30:59Z
The Physics of Spin-1/2 XY Model with Four-Site Exchange Interaction on the Kagome Lattice
The quantum spin liquid (QSL) state, proposed more than three decades ago by Fazekas and Anderson remains surprisingly elusive. Although recent experiments provide a strong evidence of their existence in the frustrated spin systems, the microscopic model for this state is still rare. The extensive theoretical framework, developed over decades, continues to extend further motivated by these and other discoveries from large-scale computer simulations of a relatively small number of models. In this work, we discuss the physics of the ground-state phase diagram of a two- dimensional Kagome lattice spin-1/2 XY model with a four-site ring-exchange interaction using quantum Monte Carlo simulation. We found the second order phase transition from superfluid state to a Z2 quantum spin liquid phase driven by the four-site ring exchange interaction. We have characterized the QSL by its vanishing order parameters such as the spin-spin structure factor, the plaquette-plaquette structure factor. Moreover, we have found the large anomalous exponent ηXY* ≈ 1.325 which belongs to a different universality class other than 3D XY universality class. There is no signal of supersolid phase intervening between the superfluid state and QSL state.
Thi Kim Oanh Nguyen
Thanh Dai Pham
Dinh Long Dang
ddlong@vnu.edu.vn
2016-12-31T14:28:29Z
2016-12-31T14:28:29Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2334
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2334
2016-12-31T14:28:29Z
Electric-field Control of a Spin “bit” Configuration in MERAM Model: A Monte Carlo Study
Magnetoelectric (ME) effect can be realized in multiferroic composites composed of the alternative ferromagnetic (FM) and ferroelectric (FE) multilayer such as FM layer grown on top of FE layer (FM/FE). In this work, we have shown that the spin orientation in FM layer can be controlled by using the electrical field indirectly via the elastic mechanism between these layers. There is a critical electric field for each FM layer such as Fe, Fe3O4, which is the minimum electric field to switch the spin to the different directions in space. The Monte Carlo simulation has been applied for the anisotropy model taken into account the magnetocrystalline anisotropy and shape anisotropy as well as the effective anisotropy field. The particular spin switching, i.e. an angle of 90 degree switching, corresponding to bit “0” and “1” switching in magnetoelectric random access memory (MERAM) will be discussed.
Long Dang
ddlong@vnu.edu.vn
2016-12-31T14:23:03Z
2016-12-31T14:23:03Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2269
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2016-12-31T14:23:03Z
Measurement of Iron-Oxide Fluids Using a Magnetoelectric Sensor
Iron oxide fluids have been measured by using a magnetoelectric (ME) effect - based magnetic sensor with a long-type sandwiched composite of Metglass/PZT/Meglass laminates of 1×15 mm2 in dimension. In homogeneous magnetic fields, the sensor exhibits a sensitivity of 307.453 mV/Oe. The minimum measurable signal (i.e. noise level) of this experimental setup was found as small as 0.782 mV, which reveals a possible detection limit of 3×10−8 emu . Our report presents the simulation and the measurement of magnetic fluids of various magnetic Fe3O4 nanoparticle concentrations. The results open a possibility of using this sensor for medical and bioengineering applications.
Xuan Toan Nguyen
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2016-12-31T14:20:18Z
2016-12-31T14:20:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2335
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2335
2016-12-31T14:20:18Z
Preparation and characterization of nanorod-like TiO2 and ZnO films used for charge- transport buffer layers in P3HT based organic solar cells
With the aim of findingout the appropriate buffer layers for organic solar cells (OSC), TiO2 and ZnO on ITO/glass were prepared as nanorod-like thin films. The TiO2 films were crystallyzed in the anatase phase and the ZnO films, in the wurtzite structure. The nanorods in both the fims have a similar size of 15 to 20 nm in diameter and 30 to 50 nm in length. The nanorods have an orientation nearly perpendicular to the ITO-substrate surface. From UV-Vis data the bandgap of the TiO2 and ZnO films were determined tobe 3.26 eV and 3.42 eV, respectively. The laminar organic solar cells with added TiO2 and ZnO, namely ITO/TiO2/P3HT:PCBM/LiF/Al (TBD) and ITO/ZnO/P3HT:PCBM/LiF/Al (ZBD)were made for characterization of the energy conversion performance. As a result, comparing to TiO2,the nanorod-likeZnO filmwas found to be a much better buffer layer that made the fill factor improve from a value of 0.60 for TBD to 0.82 for ZBD, and consequently thePCE was enhanced from 0.84 for TBD to 1.17% for ZBD.
Thi Thao Tran
thaott@vnu.edu.vn
Dinh Long Dang
ddlong@vnu.edu.vn
Van Truong Vo
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-12-31T10:22:45Z
2016-12-31T10:22:45Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2380
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2380
2016-12-31T10:22:45Z
Lipid biosynthesis of ten Thraustochyrid strains isolated from mangrove Xuan Thuy, Nam Dinh
The features of polyunsaturated fatty acid-PUFA structures were corresponded to each separate functions as adjusting the cellular physiology and gene expression. Therefore, lack of PUFA could lead to abnormalities in skin, kidney, neural networks, immune responses and inflammation; cardiovascular, endocrine, respiratory and reproductive systems. In fish oil, PUFA content were low, thus it was difficult to produce on a large scale. Therefore, the exploration of PUFA sources particularly as arachidonic acid-AA, eicosapentaenoic acid EPA, docosapentaenoic acid-DPA/DHA attracted many researches. Heterotrophic microalgae Thraustochytrids were capable of producing high amounts of DHA and PUFA composition varied. DHA can be synthesized by the metabolism of AA, EPA and DPA. The different types of PUFA reflected relationships in classification. Ten heterotrophic microalgae thraustochytrids isolated from mangrove Xuan Thuy, Nam Dinh contain fatty acid composition varied from C12 to C28. Especially, they had two important fatty acids of PUFA as EPA and DPA. Polyunsaturated fatty acids - PUFA content of ten thraustochytrid strains were from 28.95 to 49.62% total lipid. DPA compared to other PUFA were high for all thraustochytrid strains studied, accounting 20.22 to 39.35% TFA. Ten thraustochytrid strains had the highest growth with carbon source as glucose, total lipid reached 7 to 12.35 % dry weight biomass after 72 hours. Growth rate and lipid biosynthesis in organic nitrogen source were higher than in inorganic nitrogen sources. The best source of nitrogen for growth and lipid biosynthesis of ten thraustochytrid strains is yeast extract, total lipid were 8.57 to 18.87% dry weight biomass after 72 hours.
Thi Bich Dao Pham
Dinh Tuan Nguyen
Dang Khoa Tran
khoatd@vnu.edu.vn
Thi Huyen Chu
Hoang Thanh Do
Thi Hoai Ha Nguyen
2016-12-31T10:21:25Z
2016-12-31T10:21:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2211
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2211
2016-12-31T10:21:25Z
Detection of magnetic nanoparticles using simple AMR sensors in Wheatstone bridge
Wheatstone bridges incorporating a serially connected ensemble of simple AMR elements of Ni80Fe20 film were produced, targeting an application of a pinned magnetic field along the sensing magnetoresistor length. For the optimal dimension, the magnetoresistive element with length l 4 µm, width 150 µm and thickness 5 nm still shows a rather modest AMR ratio (of about 0.85% only). However, the resulting bridge exhibits a sensitivity as large as 2.15 mV/Oe. This is according to a standard sensitivity of 1.80 mV/V/Oe and a detection limit better than 10_6 emu, which is almost doubled with respect to that in the typical commercial AMR devices and is comparable with Permalloy based PHE sensor. This is suitable to detect the superparamagnetic fluid of 50 nm-Fe3O4-chitosan.
Khac Quynh Le
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Xuan Dang Dang
Quoc Viet Dong
Thi Hien Le
lehien@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2016-12-31T10:18:46Z
2016-12-31T10:18:46Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2212
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2212
2016-12-31T10:18:46Z
Detection of magnetically labeled DNA by a magnetic sensor
operating with a disposable card
Disposable cards with immobilized bioreceptors are being increasingly investigated and developed in biomedical analysis systems because they have significant advantages. In our work, a biosensor system consisting of an anisotropic magnetoresistive (AMR) sensor operating with a disposable card was developed for magnetically labeled DNA detection. The SPA/SAA/APTES/PDMS/Si as-prepared disposable card involves DNA probes specific for the 16S rRNA gene of Streptococcus suis. A single-stranded target DNA was hybridized with the DNA probe on the disposable card, which was subsequently magnetically labeled with superparamagnetic beads for detection using the AMR sensor. An almost linear response between the output signal of the AMR sensor and amount of single-stranded target DNA varied from 4.5 to 18 pmol was identified. This novel approach opens up new possibilities for the development of a sensitive, easy to use and low-cost DNA biosensor system.
Thi Hien Le
lehien@vnu.edu.vn
Khac Quynh Le
Thi Huyen Vu
Thi Yen Nguyen
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Hong Nhung Pham
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2016-12-31T10:14:37Z
2016-12-31T10:14:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2352
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2352
2016-12-31T10:14:37Z
Aspects of nondestructive detections using a magnetoelectric sensor
This article deals with the state-of-the-art techniques in the field of nondestructive (and/or distance) detections. Illustrations are described for a wide range of applications from local evaluations of magnetic nanoparticles at a depth of several centimeters in the body during clinical interventions to blood pulse analysis and pipe and cable monitoring. Developments are implemented using a magnetoelectric based magnetic sensor with a long type sandwich Metglas/PZT/Meglas laminate composite of 1×15 mm2 dimension. In the resonant mode, the sensor exhibits a sensitivity better than 200 mV/Oe and a detection limit of 3×10−8 emu. This method can detect a spot with at least 50 µg iron oxide magnetic nanoparticles at a distance of about 10 mm from the skin surface. For the radial pulse analysis, thanks to the disturbance created by blood flowing through a localized magnetic field, not only the information of the heard rate, but also the radial blood flow waveforms are monitored (fig. 1), which strongly supports the traditional Chinese medicine. Moreover, this universal detector type can also be performed for locating wood, metal, copper, iron and live wires in the walls. It is indispensable tools for any contractors in the building who have to drill holes into walls as well as building inspectors who want to making a report on a site. The magnetoelectric sensors, thus, exhibit a high potential of applications.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2016-12-31T10:13:42Z
2018-01-05T09:58:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2351
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2351
2016-12-31T10:13:42Z
Distance magnetic nanoparticle detection using a magnetoelectric sensor for clinical interventions
Distance magnetic nanoparticle detections were investigated by using a magnetoelectric based magnetic sensor with a long type bilayer Metglas/PZT laminate composite. In homogeneous magnetic fields, the sensor exhibits a sensitivity of 307.4 mV/Oe, which is possible for a detection limit of 2.7×10−7 emu. This sensor can detect an amount of 0.31 µg of the superparamagnetic Fe3O4-chitosan fluid at 2 mm height above the sensor surface. To detect a spot with magnetic nanoparticles at a distance of about 7.6 mm, it should contain at least 50 µg of iron oxide. This approach is able to develop for local detection of magnetic nanoparticles at a depth of centimeters in the body during clinical interventions
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Xuan Dang Dang
Xuan Toan Nguyen
Van Tuan Nguyen
Anh Tuan Phung
2016-12-31T10:06:32Z
2016-12-31T10:06:32Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2201
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2201
2016-12-31T10:06:32Z
Light Absorption And Luminescence Properties of the Blend Pol(N-Vinylcarbazole)/Poly(N-Hexylthiophene)
We have investigated the enhancement of light absorption and luminescence properties of the blend conducting polymers using poly(N-vinylcarbazole) and poly(N-hexylthiophene). The optimizedmaterial showed a broad absorption in the region from ultra violet to near infra-red and the better of luminescence ability than the pristine conducting polymers. The remarkable improvements in photoluminescence of the blends provide useful information to the application of this material in fabrication of optical – electronic devices.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Mai Ha Hoang
Trinh Tung Ngo
Dinh Long Dang
ddlong@vnu.edu.vn
Khac Quan Nguyen
Duy Lien Vu
2016-12-29T12:52:51Z
2017-01-12T16:10:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2354
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2016-12-29T12:52:51Z
A Novel Behavior-based Navigation Architecture of Mobile Robot in Unknown Environments
This study proposes behavior-based navigation architecture, named BBFM, for mobile robot in unknown environment with obstacles. The architecture is carried out in three steps: (i) analyzing the navigation problem to determine parameters of the architecture; (ii) designing the objective functions to relate input data with the desired output; and (iii) fusing the output of each objective function to generate the optimal control signal. We use fuzzy logic to design the objective functions and multi-objective optimization to find the Pareto optimal solution for the fusion. A number of simulations, comparisons, and experiments were conducted. The results show that the proposed architecture outperforms some popular behavior- based architectures in navigating the mobile robot in complex environments.
Thi Thanh Van Nguyen
vanntt@vnu.edu.vn
Manh Duong Phung
duongpm@vnu.edu.vn
Anh Viet Dang
vietda@vnu.edu.vn
Quang Vinh Tran
vinhtq@vnu.edu.vn
2016-12-27T07:27:52Z
2016-12-27T07:27:52Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2268
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2016-12-27T07:27:52Z
DNA-magnetic bead detection using disposable cards and the anisotropic magnetoresistive sensor
A disposable card incorporating specific DNA probes targeting the 16 S rRNA gene of
Streptococcus suis was developed for magnetically labeled target DNA detection. A singlestranded
target DNA was hybridized with the DNA probe on the SPA/APTES/PDMS/Si asprepared
card, which was subsequently magnetically labeled with superparamagnetic beads for
detection using an anisotropic magnetoresistive (AMR) sensor. An almost linear response
between the output signal of the AMR sensor and amount of single-stranded target DNA varied
from 4.5 to 18 pmol was identified. From the sensor output signal response towards the mass of magnetic beads which were directly immobilized on the disposable card surface, the limit of detection was estimated about 312 ng ferrites, which corresponds to 3.8 μemu. In comparison with DNA detection by conventional biosensor based on magnetic bead labeling, disposable cards are featured with higher efficiency and performances, ease of use and less running cost with respects to consumables for biosensor in biomedical analysis systems operating with immobilized bioreceptor
Thi Hien Le
lehien@vnu.edu.vn
Khanh Quynh Le
Thi Huyen Vu
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Phuong DM
Nhung PH
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
2016-12-14T08:32:58Z
2016-12-14T08:32:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2006
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2006
2016-12-14T08:32:58Z
Fabrication of Graphene Quantum Dots Based Fluorescent Sensor for Detection of Clenbuterol
Thi Thanh Hop Tran
Mai Ha Hoang
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Thi Lan Nguyen
Thi Nhung Hac
Van Chuong Dao
Van Thu Le
Nhu Hai Luong
Ngoc Dung Ta
Dai Lam Tran
Duc Nghia Nguyen
Trinh Tung Ngo
2016-12-14T08:29:23Z
2016-12-14T08:29:23Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2027
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2027
2016-12-14T08:29:23Z
Selection of lactic acid bacteria producing bacteriocin
In this work, lactic acid bacteria were isolated from 10 samples of the traditionally fermented foods (5 samples of Vietnamese fermented pork roll and 5 samples of the salted field cabbage) and 5 samples of fresh cow milks. These samples were collected from households in Vietnam. 22 strains of lactic acid bacteria were isolated for inhibition to Lactobacillus plantarum JCM 1149. Of these, only 2 strains including DC1.8 and NC1.2 have rod shape, the others have coccus shape. There were 7 strains showing higher antibacterial activity and selected forchecking spectrum of antibacteria with indicator bacteria consistting of Bacillus subtilis ATCC 6633, Enterococcus faecium JCM 5804 and Staphylococcus aureus TLU. . . By which, 3 strains including NC3.5 (from Vietnamese fermented pork roll), DC1.8 (from salted field cabbage) and MC3.19 (from fresh cow milk) were selected because of their higher antibacterial ability. However, the antibacterial activity of the lactic acid bacteria can be based on disposable compounds of them and some other antibacterial compounds produced during of their growth (such as lactic acid, H2O2, bacteriocins, …). For seeking lactic acid bacteria with capability of producing bacteriocins, antibacterial compounds with protein nature, , 3 above strains were checked sensitive to proteases (including protease K, papain, α – chymotrypsin and trypsin). Because bacteriocins are proteinaceous antibacterial compounds, so their antibacterial activity will be reduced if proteases are added. The result showed DC1.8 and MC3.19 were capable of producing bacteriocin during culture process. These two strains were classified to species based on analysis chemical characterisitcs by standard API 50 CHL kit and phylogeny relationship by 16s rRNA sequences. DC1.8 was identified as Lactobacillus acidophilus and MC3.19 as Lactococcus lactis.
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Minh Tu Hoa
hoaminhtu@gmail.com
2016-12-12T03:52:24Z
2016-12-12T03:52:24Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2005
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2005
2016-12-12T03:52:24Z
Synthesis of Gold Nanoparticles Capped with Quaterthiophene
for Transistor and Resistor Memory Devices
Mai Ha Hoang
Thanh Toan Dao
Thi Thu Trang Nguyen
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Trinh Tung Ngo
2016-12-08T03:46:19Z
2016-12-08T03:46:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2023
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2023
2016-12-08T03:46:19Z
Preparation and characterization of La0.67-xLi3xTiO3 solid-state electrolyte used for electrochromic mirrors
With the aim of producing all-solid-state electrochromic mirrors, La0.67-xLi3xTiO3 (LLTO) and the WO3 were prepared by electron beam deposition. The LLTO (with x = 0.11) powder was synthesized by thermally ball-grinding method and the Li+ ionic conductivity of the LLTO ceramic targets was found to be of ca. 3.25 10-3 S/cm. Using LLTO targets for e-beam evaporation, 300 nm – thick films with the Li+ ionic conductivity of 5.50 10-5 S/cm were deposited. Combining LLTO films with WO3/ITO and LiMn2O4 layers, all-solid-state electrochromic mirrors with a laminar structure of Al/LiMn2O4/LLTO/WO3/ITO were prepared. The reversible reflectance of the mirrors was well controlled by applying polarized potentials onto the ITO electrode. The obtained results suggest useful applications for electrochromic windows working as a smart reflectance mirror that can be used for auto rear-view mirrors.
Dinh Trong Le
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Hong Thanh Do
2016-12-08T03:40:11Z
2016-12-08T03:40:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2004
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2004
2016-12-08T03:40:11Z
Synthesis and Characterization of Polymeric Graphene-Quantum-Dots based Nanocomposites for Humidity Sensing
Graphene quantum dots (GQDs) were synthesized and incorporated with polyethylenedioxythiophene: poly(4-styrenesulfonate) (PEDOT:PSS) and carbon nanotube (CNT) to form a composite that can be used for humidity sensors. The 600 nm-thick composite films contained bulk heterojunctions of CNT/GQD and CNT/PEDOT:PSS. The sensors made from the composites responded well to humidity in a range from 60 to 80% at room temperature and atmospheric pressure. With a CNT content of 0.4 wt.% (GPC-1) to 0.8 wt.% (GPC-2) and 1.2 wt.% (GPC-3), the sensitivity of the humidity sensing devices based on CNT-doped graphene quantum dot-PEDOT:PSS composites was increased from 4.5% (GPC-1) to 9.0 % (GPC-1) and 11.0 % (GPC-2), respectively. The fast response time of the GPC sensors was about 20 s and it was much improved due to CNTs doping in the composites. The best value of the recovery time was found to be of 40 s, for the GPC composite film doped with 1.2 wt.% CNT content.
Minh Long Lam
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Quang Trung Tran
2016-12-07T08:26:35Z
2016-12-07T08:27:20Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2022
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2022
2016-12-07T08:26:35Z
Characterization of Electrochromic Properties of Polyaniline Thin Films Electropolymerized in H2SO4 Solution
Polyaniline (PANI) onto indium-doped tin-oxide (ITO)-coated glass samples were prepared by electroopolymerization in 0.5 M H2SO4 solution. Structure and morphology characterization of the PANI films demonstrated that the films were grown onto ITO substrates in the form of polycrystalline microbelts separated by micropores. By analysing the UV-Vis absorption spectra of the PANI films, the energy bandgap was found to be approximately 2.75 eV. The PANI/ITO films exhibited a good reversible electrochromic display (ECD) performance when cycled in 0.1 M LiClO4 + pro-pylene carbonate. The response time of the ECD coloration was found to be as small as 15 s and the coloration efficiency was found to be 8.85 cm2 C-1. After 100 cycles of the ECD performance, the cyclic voltammetry curve of the working electrode maintained unchanged. This demonstrates that the electropolymerized PANI films can be served as a good candidate for ECD applications, taking advantage of their excellent properties in terms of chemical stability.
Hai Ninh Dang
Thi Thao Tran
thaott@vnu.edu.vn
Duy Long Pham
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-12-04T13:44:22Z
2017-01-17T02:46:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2062
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2062
2016-12-04T13:44:22Z
The 2016 Annual Scientific Report of VNU University of Engineering and Technology
The University of Engineering and Technology (UET) was founded in 2004 as a member university of Vietnam National University, Hanoi (VNU).
The last only five years have seen immense progresses in the development of our university in various aspects of its activities thanks to the great efforts put in by the government with strong financial supports, by the VNU with steering leadership and administration, by the national and international educational institutions and corporations in fruitful collaborations and advices, and by all the staff and students of the UET with determination, hard work and patience.
Today, our university has built up a solid foundation for a sustainable and dynamic development in coming years. This solid foundation consists of a completed system of well-designed programs at both undergraduate and graduate levels, renovated teaching and learning facilities, a just limited but strong and advanced research infrastructure with state-of-the-art and completed equipment systems, a sustainable and fruitful collaboration with leading research and educational institutions in the country, and a bright, young, well-educated and welltrained faculty who are eager to take on advanced research and studies. All these have made our university a prestigious institution and firmly established its education and research capabilities. This is proved by the facts that only in the last four years our university has established close and solid ties and cooperation with prestigious foreign universities, just to name a few, the University Paris-Sud 11 (France), Japan Advanced Institute of Science and Technology, the National University of Singapore, Nanyang Technological University (Singapore), University of New South Wales and with famous international industrial and technological corporations such as Samsung, Toshiba, NEC, Mitani, Human Resocia, IBM, and other well-known institutions in the region and around the world. This is also proved in a convincing way by the facts that only in the last two years, our university has been granted several significant research projects from various national research programs. Our university has become an attractive destination for talented students at all training levels. We are proud that our university is the only Vietnamese higher-education institution that has one among the 100 best student’s teams all over the world participating the World Final of the ACM International Collegiate Programming Contest (rank #29 in 2015). We are also proud that in this year, our faculty has won an award in the National Contest in Information Technology entitled “Vietnamese Talent Award” and three awards in the VNU Science & Technology Award for the period of 2011-2015. In the coming period, we shall put our great efforts to solidify our strength and prestige. We shall widen our training scope while paying significant attention to further improvement on the education quality. We shall strongly enhance our concentrated research activity by exploring efficiently and effectively our well established foundation for a further dynamic development and, thus, contributing our crucial part to the socio-economic development of our nation and fulfilling our great missions clearly assigned by the government in the decision on the establishment of our university. To do that, innovative thinking and acting by all faculty, administrative staff and students are of deciding role and of crucial importance.
Xuan Tu Tran
tutx@vnu.edu.vn
Anh Cuong Le
cuongla@vnu.edu.vn
Duc Tan Tran
tantd@vnu.edu.vn
Manh Thang Pham
thangpm@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-12-02T06:51:59Z
2016-12-02T06:51:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2024
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/2024
2016-12-02T06:51:59Z
Synthesis and Characterization of Ag/PEDOT:PSS films used for NH3 selective sensing
Nano-Ag/PEDOT-PSS films were prepared by spin-coating technique. SEM surface morphology, Raman spectra and gas sensing of methanol, humidity and NH3 were studied. The obtained results showed that the resistance of Ag/PEDOT:PSS sheets exposed to gases related to the generation of electrons from the gases adsorption that eliminated holes as the major carriers in PEDOT:PSS. For NH3 gas the largest change of the resistance of Ag/PEDOT:PSS was observed. The less sensitivity of humidity and ethanol sensing was explained due to less dedoping reaction between H2O and ethanol vapor with Ag/PEDOT:PSS, recpectively. This suggests a potential application of the nano-Ag/PEDOT-PSS sensors for the selective monitoring NH3 gas in environment.
Minh Long Lam
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Quang Trung Tran
2016-07-18T03:22:23Z
2016-07-18T03:24:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1795
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1795
2016-07-18T03:22:23Z
Magnetic Behaviors of Arrays of Co-Ni-P Nanorod: Effects of Applied Magnetic Field
The Co-Ni-P nanorods were fabricated by electrodeposition method by using the porous polycarbonate template. The investigation by mean of X-ray diffraction and high-resolution transmission electron microscopy indicated that samples were nanocrystalline clusters embedded in the amorphous base. The samples exhibited a room temperature ferromagnetism with the high magnetic anisotropy along the rod. The applied magnetic fields during the fabrication of the Co-Ni-P nanorods was strongly influenced by the magnetic properties. The MR/MS ratio and coercivity rapidly increased when the magnetic applied field changed from 0 to 0.21 T.
V. Thiem L.
Duc Thang Pham
pdthang@vnu.edu.vn
D. Dung D.
T. Tu L.
G. Kim C
2016-07-18T03:20:06Z
2016-07-18T03:21:04Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1801
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1801
2016-07-18T03:20:06Z
Dye-sensitized solar cells composed of photoactive composite photoelectrodes with enhanced solar energy conversion efficiency
Phosphor particles were introduced as a luminescent medium to improve the overall efficiency of dye sensitized solar cells (DSSCs). In the preparation process, TiO2 and phosphor particles were mixed to make photoelectrodes with bilayer (TiO2/mix), 3-layer (TiO2/mix/TiO2) and 4-layer (TiO2/mix/TiO2/mix) structures. The cell with the bilayer structure (TiO2/mix) after treating with TiCl4 solution showed the highest light-to-electric energy conversion efficiency (8.78%), which was ∼25.8% higher than that of a cell with a pure TiO2 layer under the same experimental conditions. The improvement in the energy conversion efficiency of DSSCs was attributed to phosphor enhanced incident light-harvesting via up- and down-conversion luminescence processes, resulting in an increase in the photocurrent.
Thi Hong Ha Vu
Sh. Atabaev Timur
Young Ahn Ji
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Kook Kim Hyung
Hwae Hwang Yoon
2016-07-18T03:18:27Z
2016-07-18T03:19:47Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1818
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1818
2016-07-18T03:18:27Z
Microalgae as indicators of eutrophication in Hoan Kiem lake, Hanoi, Vietnam
Thi Hoai Ha Nguyen
Thi Bich Dao Pham
Thanh Loan Dang
Ngoc Thanh Nguyen
Dinh Tuan Nguyen
Thi Mai Pham
Dang Khoa Tran
khoatd@vnu.edu.vn
2016-07-18T03:17:20Z
2016-07-18T03:18:12Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1824
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1824
2016-07-18T03:17:20Z
Sub-100 nm Ferroelectric-Gate Thin-Film Transistor with Low-Temperature PZT Fabricated on SiO2/Si Substrate
Thin film transistor which uses an active oxide-semiconductor channel and a ferroelectric-gate insulator, so-called FGT, has wide attention for the application of a new nonvolatile memory owing to its prominent features such as simple structure, high speed and low power consumption. Previously, we have reported on demonstration of the FGTs operation, but the ones developed have channel lengths (LDS) more than 100 nm, which should be reduced for high-density storage in integration circuits. In this work, a new technique has been proposed to fabricate the sub-100 nm FGT using low-temperature PZT thin film, whose source-drain gap would be mainly created from electron beam lithography, dry etching and ashing. With the new technique, the memory functionality of the fabricated sub-100 nm FGTs are comparable with that of the sub-μm sized FGT. In particular, the ON/OFF current ratio is about 104–105, the memory window is 2.0, 1.8 and 1.7 V, and the field-effect mobility is 0.12, 0.07 and 0.16 cm2V−1s−1 for the LDS of 100, 50, and 30 nm, respectively.
Hong Minh Do
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2016-07-15T09:44:40Z
2016-07-15T09:45:29Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1823
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1823
2016-07-15T09:44:40Z
Điều tra sự nhiễm virus black queen cell gây bệnh thối mũ chúa trên các đàn ong mật tại Việt Nam
Thi Thuy Duong Bui
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Thu Ha
Thuy Linh Mai
Hong Thai Pham
Van Quyen Dong
2016-07-15T09:42:53Z
2016-07-15T09:44:22Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1822
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1822
2016-07-15T09:42:53Z
Nghiên cứu phát hiện virus gây bệnh thối đen mũ chúa (black queen cell virus) trên ong mật ở một số tỉnh miền Bắc Việt Nam năm 2013
Thi Quyen Ha
quyenht@vnu.edu.vn
Thi Thu Ha
Thuy Duong Bui
Van Quyen Dong
2016-07-13T10:04:04Z
2016-07-13T10:06:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1820
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1820
2016-07-13T10:04:04Z
Immobilization and characterization of functional groups deposited on gold nanoparticles for biosensor applications
Kien Cuong Nguyen
cuongnk@vnu.edu.vn
Stathis Efstathios
I. Meletisa
2016-07-13T10:02:43Z
2016-07-13T10:03:38Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1819
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1819
2016-07-13T10:02:43Z
Ứng dụng thuốc thú y mới Argumistin trên nền hạt nano bạc để điều trị bệnh viêm nội mạc tử cung sau sinh ở bò.
Thi Hien Le
lehien@vnu.edu.vn
Thi Huyen Vu
A. Krutyakov Yu
2016-07-11T12:47:41Z
2016-07-11T12:49:19Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1817
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1817
2016-07-11T12:47:41Z
Luminescence Properties of Ce/Tb/Sm Co-Doped Tellurite Glass for White Leds Application
In this work, the Ce/Tb/Sm doped glasses with the composition of TeO2-B2O3-ZnO-Na2O were synthesized by melt quenching process. The photoluminescence properties of glasses doped with Ce3+, Tb3+ and Sm3+ single, doubly and triply doped TeO2-B2O3-ZnO-Na2O (TBZN) were studied by mean of emission and excitation spectra. There was an overlap between Ce3+ emission and Tb3+, Sm3+ absorption in the wavelength range of 350–500 nm. Therefore, it was expected that an efficient energy transfer occurred from Ce3+ to Tb3+ and Ce3+ to Sm3+ ions. When excited by ultraviolet wavelengths the co-doped glasses emit a combination of blue, green and red orange forming white light.
Thi Hong Tran
hongtt@vnu.edu.vn
Duc Huyen Yen Pham
Xuan Quang Vu
Tien Dung Phan
2016-07-11T12:46:42Z
2016-07-11T12:47:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1816
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1816
2016-07-11T12:46:42Z
Stable Gold Carbide Nanostructures
The exemplars of gold carbide AuC in cubic F-43m structure and cluster form Au<sub>6</sub>C<sub>3</sub> are reported. The characteristics of structures were obtained on basis of Time-Dependent Density Functional Theory (TD-DFT) embedded within the framework of Generalized Gradient Approximation (GGA) and utilized Pardew-Burke-Ernzerhof functional (PBE) and spin-polarized wave functions. We found that the modeled forms of gold carbide exhibited no ferromagnetism while maintaining metallic ground state. The calculation showed the dominance of optical transitions which preserved spin.
Khac Thuan Nguyen
Van Hiep Vuong
Thi Kim Anh Do
Nam Nhat Hoang
nhathn@vnu.edu.vn
2016-07-11T12:45:54Z
2016-07-25T06:50:24Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1815
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1815
2016-07-11T12:45:54Z
Cảm biến từ trường siêu nhạy dựa trên hiệu ứng từ- điện cho việc phát hiện nhanh các hạt từ kích thước nano
Xuan Toan Nguyen
Xuan Dang Dang
Khac Quynh Le
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-07-11T12:44:42Z
2016-07-11T12:45:38Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1814
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1814
2016-07-11T12:44:42Z
Fabrication and investigation of magnetic sensor based on anisotropy magnetoresistance effects for magnetic beads detection
K. Quynh L.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
X. Dang D.
Quoc Viet Dong
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Hien Le
lehien@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-07-11T12:43:26Z
2016-07-11T12:44:28Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1813
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1813
2016-07-11T12:43:26Z
Research, manufacturing optimal structure sensor measure the low magnetic field structure Wheatstone bridge based on anisotropic magnetoresistance effects
K. Quynh L.
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Quoc Viet Do
T. Thuy N.
Xuan Toan Nguyen
Mau Danh Tran
danhtm@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-07-11T12:42:04Z
2016-07-11T12:42:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1812
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1812
2016-07-11T12:42:04Z
The MEH-PPV/YAG:Ce Hybrid Nanocomposite Material for Solution Processing Fabrication of Optoelectronic Device
The fabrication and the property investigation of the hybrid nanocomposite material made of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) polymer and Y 3 Al 5 O 12 :Ce (YAG:Ce) with the relative weight ratio of 1 : 1 in order to apply for optoelectronic devices are reported. Thermal analysis showed the hybrid material’s deterioration or decomposition when the temperature exceeded 200°C under inert gas atmosphere. Rheological measurement concluded that the material solution can be used for spinning or soft moulding lithography making large- or flexible substrate surface. Optical properties of the hybrid material are investigated. The effect of thermal treatment on the optical properties showed that, at 180°C under inert gas environment, the optical properties were enhanced. An MEH-PPV/YAG:Ce hybrid nanocomposite converted LED lamp was fabricated showing that the hybrid material is suitable as conversion material for white LED fabrication.
Van Chau Dinh
dinhchau@vnu.edu.vn
Van Thuong Dinh
2016-07-11T12:40:48Z
2016-07-11T12:41:42Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1811
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1811
2016-07-11T12:40:48Z
MEH-PPV: PCBM Solution for Screen-printing Technique in Polymer Solar Cell Fabrication
The fabrication and property characterization of bulk heterojunction photoactive layer made of blend of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) and fabricated by screen-printing technique was carried out. Effects of the photoactive solid concentration, temperatures at 15, 25 and 35°C and shear rate ranging from 100-104 sec–1 on the viscosity was investigated and shows that 1, 3 and 5% solid concentrated solutions are possible for using as ink in this technique in term of rheological property. Thickness of the films fabricated from different solid concentrated solutions at different print speed was measured and show a dependency of film thickness on print speed as well as exponential law dependence on solid concentration of the solution. Surface morphology and absorption coefficient of the films was also carried out and confirms that the films formed by the screen printer is well-adapted for fabricate photovoltaic devices.
Van Chau Dinh
dinhchau@vnu.edu.vn
Van Thuong Dinh
2016-07-11T12:39:42Z
2016-07-11T12:40:30Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1809
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1809
2016-07-11T12:39:42Z
Estimation of Valence Distribution in Perovskites using the Bond Valence Method
This paper presents the application of the bond valence method to estimate the valence charge distribution in several perovskite systems: La1-xxPbxMn03 (x=0.1-0.5), La0.6Sr0.4.xTixMnO3 (x=0.0- 0.25) and La1=xSrxCoO3 (x=0.1-0.5). The results showed a failure of elastic bonding mechanism in all compounds and revealed a deficit of valence charge in the unit cells. This valence deficit was not associated with the structural defects and is equally localized in all coordination spheres. As the content of substitution increased, the charge deficit declined systematically from balanced level, signifying the transfer of charge from the B-O6 to A-O12 spheres. This transfer reaches near 2 electrons per unit cell. The possible impact of the limitted accuracy of available structural data was considered.
D.H. Yen P.
T. Hang N.
Van Chau Dinh
dinhchau@vnu.edu.vn
Van Thuong Dinh
Nam Nhat Hoang
nhathn@vnu.edu.vn
2016-07-11T12:38:17Z
2016-07-11T12:39:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1808
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1808
2016-07-11T12:38:17Z
Effect of Cerium Doping on Crystal Structure and Magnetic Properties of La1-yCeyFe11.44Si1.56 Compounds
Kim Anh Do
Van Chau Dinh
dinhchau@vnu.edu.vn
Nam Nhat Hoang
nhathn@vnu.edu.vn
Van Hiep Vuong
Kurisu Makio
2016-07-11T12:36:59Z
2016-07-11T12:37:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1807
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1807
2016-07-11T12:36:59Z
Room-temperature ferromagnetism in Fe-doped wide band gap ferroelectric Bi0.5K0.5TiO3 nanocrystals
We reported the room-temperature ferromagnetism in iron doped Bi0.5K0.5TiO3 nanocrystals. The reduction of band gap from 3.31 eV to 2.27 eV was obtained after introduction of iron to Bi0.5K0.5TiO3 with concentration up to 7 mol%. The first-principles density function theory (DFT) calculations indicate that the reduction of band gap is due to the presence of conduction bands of iron, and the ferromagnetism in iron-doped Bi0.5K0.5TiO3 samples was explained by the exchange splitting between spin subbands through crystal field theory. This method may provide an available way to get single-phase multiferroics and resolve the problem of the scarcity of single-phase multiferroics in nature.
Duc Dung Dang
Van Thiet Duong
Odkhuuc Dorj
Viet Cuong Le
cuonglv@vnu.edu.vn
Hoang Tuan Nguyen
Cho Sunglae
2016-07-11T12:34:06Z
2016-07-11T12:35:05Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1806
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1806
2016-07-11T12:34:06Z
Sorting and Trapping Human Cells Using a Matrix of Square Micro-Magnets
In this work we present a study on sorting and trapping some living human cells, including red blood cells (RBCs) and breast cancer cells (denoted T47D), by using patterned micro-magnets with dimensions of each micro-magnet 50 × 50 µm<sup>2</sup>. The diamagnetic properties of these cells and the force exerted on them along the <i>z</i>-axis have been investigated. The diamagnetic levitation height of each cell has been both theoretically calculated and experimentally studied. The results open a novel possibility for positioning living cells with further applications to medical diagnostics.
Viet Cuong Le
cuonglv@vnu.edu.vn
Xuan Nghia Nguyen
Duc Thang Pham
pdthang@vnu.edu.vn
2016-07-11T12:31:32Z
2016-07-11T12:33:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1805
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1805
2016-07-11T12:31:32Z
Characterization of organic solar cells made from conjugate polymer and CdSe, CdS quantum dots thin films, Advances in Optics Photonics
Thi Thao Tran
thaott@vnu.edu.vn
Thi Thuy Nga Nguyen
Van Truong Vo
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-07-11T12:30:31Z
2016-07-11T12:31:18Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1804
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1804
2016-07-11T12:30:31Z
Development of laser beam diffraction technique for determination of thermal expansion coefficient of polymeric thin films
Laser beam diffraction by a patterned surface has been investigated theoretically and experimentally for the determination of the thermal expansion coefficient (a) of polymeric materials. By tracking the deviation of the first order diffraction mode from surface-patterned polymers, expansion coefficients in a range 10-7 to 10-4 K-1 can be measured by temperature changes less than 100 oC. A set-up of laser diffraction (SLD) was made, using a He-Ne laser (l = 632.8 nm) and thin film casting technique. The results of measurements on the SLD system for polymers like PVK polycarbonate, PDMS, organic complex (chitosan) and conducting polymer (P3HT) showed that SLD technique can be applied to determine thermal expansion coefficients of different polymeric materials with a considerably small volume. Especially, the fact that a of P3HT-composite films was found to be much lower than that of the pure P3HT suggests a potential application of polymeric composites for organic devices working at elevated temperature, for organic solar cells (OSC) in particular.
Nguyen Van Thuan, Tran Vinh Son, Tran Quang Trung, Tran Thi Thao, Nguyen Nang Dinh
Van Thuan Nguyen
Vinh Son Tran
Quang Trung Tran
Thi Thao Tran
thaott@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-07-11T12:28:23Z
2016-12-10T10:59:26Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1803
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1803
2016-07-11T12:28:23Z
Light Absorption and Luminescence Quenching Properties of Hybrid Bulk Heterojunction Materials Based on the Blend Conducting Polymers
We have investigated the enhancement absorption light and luminescence quenching properties of the hybrid bulk heterojunction systems which were fabricated using poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV); poly(3-hexylthiophene) (P3HT); fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6] C61 (PCBM) and TiO2 nanocrystals. The optimized material showed a broad absorption in the region of 350 to 670 nm and the luminescence quenching higher 85%. The obtained results provide further insight into photophysics of the heterojunction system and device performance improvement by using this system as an active layer.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Thu Ha Le
Trinh Tung Ngo
2016-07-11T12:25:27Z
2016-07-11T12:27:41Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1802
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1802
2016-07-11T12:25:27Z
Characterzation of the Li-ionic Conductivity of La(2/3-x)Li3xTiO3 ceramics used for all-solid-state batteries
Dinh Trong Le
Thi Thao Tran
thaott@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-07-06T06:38:25Z
2016-07-06T06:39:02Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1800
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1800
2016-07-06T06:38:25Z
Enhancement of Power Efficiency and Stability of P3HT-based Organic Solar Cells under Elevated Operating-Temperatures by using a Nanocomposite Photoactive Layer
With the aim to find out an enhanced operating-temperature range for photovoltaic device parameters, two types of the photoactive layer were prepared: poly(3-hexylthiophene) (P3HT) and P3HT+nc-TiO2 (PTC) thin films. The enhancement obtained for the photoelectrical conversion efficiency of the composite based OSCs is attributed to the presence of nanoheterojunctions of TiO2/P3HT. For the temperature range of 30–70°C, the decrease of the open-circuit potential was compensated by an increase of the fill factor; and the increase in the short-circuit current resulted in an overall increase of the energy conversion efficiency. At elevated temperatures of 60–80°C the efficiency of the P3HT- and PTC-based cells reached a maximum value of 1.6% and 2.1%, respectively. Over this temperature range the efficiency of P3HT-based OSC decreased strongly to zero, whereas for the PTC cells it maintained a value as large as 1.2% at the temperature range of 110–140°C. The improved thermal stability of the composite-based device was attributed to the lowered thermal expansion coefficient of the nanocomposite photoactive layer.
Thi Thao Tran
thaott@vnu.edu.vn
Quang Trung Tran
Van Truong Vo
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-07-06T06:37:03Z
2016-07-06T06:38:00Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1799
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1799
2016-07-06T06:37:03Z
Crystal Structure and Photoluminescence Properties of Eu-Doped Y2O3 Nanoparticles Prepared by Mechanical Milling
We have used a top-down approach of the mechanical milling to fabricate Y2O3:Eu3+ nanoparticles (NPs), and then studied their crystal structure and photoluminescence (PL) properties based on X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and PL spectroscopy. XRD results revealed that the change of the milling time (tm) from 0 to 540 minutes (min) decreased the average crystallite size (d) of NPs from ³83 nm (for tm = 0 min) to below 3.5 nm (for tm = 540 min). This varied lattice strain and defects, and caused the structural changes, which influenced directly the PL properties of NPs. Among the fabricated NP samples, those with tm = 510 min (corresponding to d μ 2540 nm) offer strongest PL intensity at ³611 nm (due to the electronic transition 5 D0 ¼ 7 F2). The increase of the longer milling time (i.e., lowering d) reduces quickly the intensity of this emission, but slightly increased the intensity of auxiliary emissions. The nature of the observed phenomena was discussed.
L. Phan T.
Ngoc Chung Do
chungdn@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
C. Yu S.
2016-07-06T06:36:05Z
2016-07-06T06:36:48Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1798
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2016-07-06T06:36:05Z
Critical behavior and magnetocaloric effect of Pr1-xCaxMnO3
The critical behavior of Pr1− x Ca x MnO3 samples with x = 0.25, 0.27, and 0.29 has been investigated. Detailed analyses of magnetic-field dependences of magnetization at temperatures around the paramagnetic-ferromagnetic transition, M(H, T), reveal that the samples undergo a second-order magnetic phase transition. The Arrott plot method predicts the values of critical parameters to be T C ≈ 118 K, β = 0.351 ± 0.003, γ = 1.372 ± 0.002, and δ = 4.90 ± 0.02 for x = 0.25; T C ≈ 116 K, β = 0.362 ± 0.002, γ = 1.132 ± 0.004, and δ = 4.09 ± 0.03 for x = 0.27; and T C ≈ 110 K, β = 0.521 ± 0.002, γ = 0.912 ± 0.005, and δ = 2.71 ± 0.02 for x = 0.29. The values of β = 0.351 (for x = 0.25) and β = 0.362 (for x = 0.27) are close to the value β = 0.365 expected for the 3D Heisenberg model, proving an existence of short-range ferromagnetic interactions in these samples. A slight increase in Ca-doping content (x = 0.29) leads to the shift of the β value (=0.521) towards that of the mean-field theory (with β = 0.5) characteristic of long-range ferromagnetic interactions. The samples also exhibit a magnetocaloric effect: around T C of Pr1− x Ca x MnO3 compounds, magnetic-entropy change reaches the maximum values of about 5.0, 4.1, and 2.5 J kg−1 K−1 for x = 0.25, 0.27, and 0.29, respectively, under an applied-field change of 50 kOe. Magnetic-field dependences of the maximum magnetic-entropy change (ΔS max) obey a power law |ΔS max(H)| ∝ Hn , where exponent values n = 0.68–0.74 are close to those obtained from the theoretical relation n = 1 + (β − 1)/(β + γ).
T. A. Ho1, T. D. Thanh1,2, Yu3, D. M. , T. O. Ho4, P. D. Thang5, Anh-Tuan Le6, The-Long Phan1 and S. C. Yu
A. Ho T.
D. Thanh T.
Yikyung Yu
M. Tartakovsky3 D.
O. Ho T.
Duc Thang Pham
pdthang@vnu.edu.vn
Anh Tuan Le
The Long Phan
C. Yu S.
2016-07-06T06:35:15Z
2017-06-15T01:55:53Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1797
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1797
2016-07-06T06:35:15Z
Critical Behavior of La0.7Ca0.3MnO3 Nanoparticles
We used the modified Arrott plot method to analyze magnetic-field dependences of magnetization, M(H), around the ferromagneticparamagnetic
(FM-PM) phase-transition temperature (TC) of three nanocrystalline La0.7Ca0.3MnO3 samples with average crystallite sizes d = 40,
23, and 16 nm. The analyses obtained the values of critical parameters to be TC µ 261 K, ¢ = 0.485 « 0.005, £ = 1.051 « 0.094 and ¤ = 3.1 «
0.1 for the sample with d = 40 nm, TC µ 252 K, ¢ = 0.525 « 0.010, £ = 0.893 « 0.139 and ¤ = 2.7 « 0.1 for d = 23 nm, and TC µ 236 K,
¢ = 0.621 « 0.008, £ = 0.825 « 0.007 and ¤ = 2.2 « 0.2 for d = 16 nm. With these critical values, the M(H) data points around TC of the
samples fall into two universal branches of a scaling function M(H, ¾) = «¾«
¢f«(H/«¾«
¢+£
), with ¾ = (T ¹ TC)/TC, f+ for T > TC and f¹ for T < TC.
The results reveal that the crystallite-size reduction of nanoparticles decreases the TC value. This is ascribed to the decrease of FM doubleexchange
interactions between Mn3+ and Mn4+ ions, which is related to the ¢ change from 0.485 for d = 40 nm to 0.621 for d = 16 nm,
corresponding to the change in FM order from the long-range type to the short-range one.
A. Ho T.
D. Thanh T.
V. Manh T.
O. Ho T.
Duc Thang Pham
pdthang@vnu.edu.vn
L. Phan T.
C. Yu S.
2016-07-06T06:33:35Z
2016-07-06T06:35:07Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1796
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1796
2016-07-06T06:33:35Z
Local geometric and electronic structures and origin of magnetism in Co-doped BaTiO3 multiferroics
We have prepared polycrystalline samples BaTi1−xCoxO3 (x = 0–0.1) by solid-state reaction. X-ray diffraction and Raman-scattering studies reveal the phase separation in crystal structure as changing Co-doping content (x). The samples with x = 0–0.01 are single phase in a tetragonal structure. At higher doping contents (x > 0.01), there is the formation and development of a secondary hexagonal phase. Magnetization measurements at room temperature indicate a coexistence of paramagnetic and weak-ferromagnetic behaviors in BaTi1−xCoxO3 samples with x > 0, while pure BaTiO3 is diamagnetic. Both these properties increase with increasing x. Analyses of X-ray absorption spectra recorded from BaTi1−xCoxO3 for the Co and Ti K-edges indicate the presence of Co2+ and Co3+ ions. They locate in the Ti4+ site of the tetragonal and hexagonal BaTiO3 structures. Particularly, there is a shift of oxidation state from Co2+ to Co3+ when Co-doping content increases. We believe that the paramagnetic nature in BaTi1−xCoxO3 samples is due to isolated Co2+ and Co3+ centers. The addition of Co3+ ions enhances the paramagnetic behavior. Meanwhile, the origin of ferromagnetism is due to lattice defects, which is less influenced by the changes caused by the variation in concentration of Co2+ and Co3+ ions.
The-Long , P. D. Thang2, T. A. 1, T. V. Manh1, Tran Dang Thanh1,3, V. D. Lam3, N. T. Dang4 and S. C. Yu
The Long Phan
Duc Thang Pham
pdthang@vnu.edu.vn
A. Ho T.
V. Manh T.
Dang Thanh Tran
D. Lam V
T. Dang N.
C. Yu S.
2016-05-27T03:13:37Z
2016-05-27T03:14:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1757
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1757
2016-05-27T03:13:37Z
Fabrication and characterization of PZT string based MEMS devices
String based MEMS devices recently attract world technology development thanks to their advantages over cantilever ones. Approaching to this direction, the paper reports on the micro-fabrication and characterization of free-standing doubly clamped piezoelectric beams based on heterostructures of Pd/FeNi/Pd/PZT/LSMO/STO/Si. The displacement of strings is investigated in both static and dynamic mode. The static response exhibits a bending displacement as large as 1.2 μm, whereas the dynamic response shows a strong resonance with a high quality factor of 40 depending on the resonant mode at atmospheric pressure. These findings are comparable with those observed in large dimension membrane and cantilever based MEMS devices, which exhibit high potentials in variety of sensor and resonant actuator applications.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
G. Agnus
T. Maroutian
Philippe Lecoeur
2016-05-23T07:45:08Z
2016-05-23T07:46:45Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1586
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1586
2016-05-23T07:45:08Z
Electric field-controlled magnetization in exchange biased IrMn/Co/PZT multilayers
Electric-field modulating exchange bias and near 180 ◦ deterministic magnetization switching
at room temperature are demonstrated in simple antiferromagnetic/ferromagnetic/ferroelectric (AFM/FM/FE) exchange-coupled multiferroic multilayers of IrMn/Co/PZT. A rather large exchange bias field shift up to 1 Hex/ Hex = 500% was obtained. This change governs mainly the electric-field strength rather than the applied current. It is explained as being realized through the competition between the electric-field induced uniaxial and unidirectional anisotropies. These results show good prospects for low-power spintronic devices.
Thi Huong Giang Do
giangdth@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
G. Agnus
Philippe Lecoeur
2016-05-23T02:17:06Z
2016-05-23T02:19:58Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1565
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2016-05-23T02:17:06Z
Sub-100nm ferroelectric-gate thin film transistor fabricated by two-step patterning method
Ferroelectric-gate thin film transistor (FGT) which uses an active oxide-semiconductor channel and a ferroelectric-gate insulator has attracted wide attention for the application of a new nonvolatile memory because of its prominent features such as simple device structure, high-speed operation and low power consumption. Recently, we have reported on demonstration of the of FGTs operation. However, the FGTs developed have channel lengths (LDS) more than 100 nm, which should be reduced for high-density storage in integration circuits.1-2) In this paper, we will present a new method to fabricate the sub-100 nm FGT, of which the source-drain gap would be surely created, in principle, comparing with the conventional patterning method. Electrical properties and memory functionalities of the fabricated sub-100nm FGTs will be investigated and discussed in detail.
Hong Minh Do
Duc Thang Pham
pdthang@vnu.edu.vn
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2016-05-23T01:28:55Z
2016-05-23T01:31:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1568
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2016-05-23T01:28:55Z
Research, manufacturing optimal structure sensor measure the low magnetic field structure Wheatstone bridge base on anistropic magnetoresistance effects
Fabrication and study of sensors applied to measure low magnetic fields whose the Wheatstone structure basing on anisotropic magnetoresistance effects. The configuration optimatization of sensors was conducted by varying the thickness of NiFe layers (5, 10, 15 nm) as well as the structure of resistive bars. Two types of sensor with the sizes of 50×250 μm and 10×250 μm were examined. The results revealed the significant dependence of sensor signals on sensor shape anisotropy. The resistivie difference (ΔR), the sensitity (SH) and the shape anisotropy were observed to increase as decreasing the thickness of NiFe layer. The highest values (ΔR and SH were obtained to be 10Ω and 0.88 Ω/Oe (~ 0,88 mV/Oe), respectively) were found in the sensor with the size of 10×250 μm and 5 nm-thickness. The function of the output voltage versus the Earth's magnetic field and the sensor axis was fitted to be V = A + B*cosα (A, B are empirical constants), and Sα = 8.8 (μV/deg.)
Khac Quynh Le
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Q. Viet D.
T. Thuy N.
Xuan Toan Nguyen
Mau Danh Tran
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-05-23T01:25:57Z
2016-05-23T01:26:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1569
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2016-05-23T01:25:57Z
Chế tạo, nghiên cứu cấu trúc và tính chất của một số hệ màng mỏng hợp kim AuFe
Công nghệ cấy ion bằng máy gia tốc hiện nay là một trong những phương pháp rất hiện đại trong việc chế tạo và nghiên cứu tính chất của vật liệu, đặc biệt trong việc chế tạo các vật liệu khó hòa tan như H, C ...vào các màng mỏng kim loại. Màng mỏng hợp kim AuFe được chế tạo bằng phương pháp bốc bay nhiệt trong chân không. Sau đó, bằng máy gia tốc pelletron 5SDH-2 chúng tôi đã cấy ion C để tạo nên 5 hệ mẫu AuFe+C với nồng độ C khác nhau. Các hình thái cấu trúc, các tính chất điện, từ, quang học cũng đã được chúng tôi khảo sát. Các kết quả cho thấy rằng, màng mỏng AuFe được hình thành với tỉ lệ 1:3 và tương đối đồng đều. Các màng mỏng AuFe+C đã có sự thay đổi kích thước ô mạng, đặc biệt độ dẫn tương đối của màng này lớn hơn với màng AuFe gốc và thể hiện tính dẫn điện khá tốt, đỉnh hấp thụ cực đại nằm trong vùng ánh sáng tím và đặc biệt là sự xuất hiện của đỉnh phát xạ ở khoảng 415nm. Ngoài ra, chúng tôi còn khảo sát thêm một số tính chất khác của màng mỏng này như tính chất từ tại vùng nhiệt độ từ 80K đến 1000K.
Khac Thuan Nguyen
Nam Nhat Hoang
nhathn@vnu.edu.vn
2016-05-23T01:16:42Z
2016-05-23T01:18:11Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1571
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2016-05-23T01:16:42Z
Nonlinear Dynamic Response and Vibration of Imperfect Shear Deformable Functionally Graded Plates Subjected to Blast and Thermal Loads
Based on Reddy’s higher-order shear deformation plate theory, this paper presents an analysis of the nonlinear dynamic response and vibration of imperfect functionally graded material (FGM) thick plates subjected to blast and thermal loads resting on elastic foundations. The material properties are assumed to be temperature-dependent and graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. Numerical results for the dynamic response and vibration of the FGM plates with two cases of boundary conditions are obtained by the Galerkin method and fourth-order Runge- Kutta method. The results show the effects of geometrical parameters, material properties, imperfections, temperature increment, elastic foundations and boundary conditions on the nonlinear dynamic response and vibration of FGM plates.
Duc Tuan Ngo
Phuong Tran
Quoc Quan Tran
Dinh Duc Nguyen
ducnd@vnu.edu.vn
2016-05-23T01:14:46Z
2016-05-23T01:23:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1572
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1572
2016-05-23T01:14:46Z
Phát hiện lượng hạt từ kích thước nano bằng cảm biến từ trường siêu nhạy
Phát hiện các hạt siêu thuận từ kích thước nano đòi hỏi phải có một cảm biến từ trường với độ nhạy cao, độ phân giải lớn và tỷ số tín hiệu/nhiễu cao. Chúng tôi đã chế tạo thành công cảm biến dựa trên hiệu ứng từ-điện (ME - magnetoelectric) trên vật liệu tổ hợp Metglas/PZT đạt độ phân giải trong khoảng nanoTesla. Báo cáo này trình bày các kết quả đo đạc thực nghiệm trên dung dịch chứa các hạt siêu thuận từ Fe3O4 kích thước 20 nm ở các nồng độ khác nhau sử dụng cảm biếm tự chế tạo. Kết quả đo đạc thực nghiệm với cảm biến tự chế tạo đã phát hiện được lượng rất nhỏ (~100 nanogram) các hạt siêu thuận từ mà các phương pháp đo không tiếp xúc thông thường không phát hiện được. Các kết quả nghiên cứu này mở ra khả năng chế tạo các cảm biến sinh học dùng trong các bộ KIT nhận biết và đo đạc định lượng các phần tử sinh học có đánh dấu từ rất nhỏ với độ chính xác và độ tin cậy cao.
Xuan Toan Nguyen
Xuan Dang Dang
Khac Quynh Le
Dinh Tu Bui
buidinhtu@vnu.edu.vn
Huu Duc Nguyen
ducnh@vnu.edu.vn
Thi Huong Giang Do
giangdth@vnu.edu.vn
2016-05-23T01:09:24Z
2016-05-23T01:12:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1573
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1573
2016-05-23T01:09:24Z
Optical Property and Photoelectrical Performance of a Low-Bandgap Conducting Polymer Incorporated With Quantum Dots Used for Organic Solar Cells
By using spin-coating technique, a low bandgap conjugated polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopen-ta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and its composite thin films have been prepared. The optical absorption and photoconductive properties with over a wide spectral range, from 350 to 950 nm, were characterized. The obtained results showed that PCPDTBT:10 wt% CdSe composite is the most suitable for efficient light-harvesting in polymer-based photovoltaic cells. The photoelectrical conversion efficiency (PCE) of the device with a multilayer structure of ITO/PEDOT/ PCPDTBT:CdSe /LiF/Al reached a value as large as 1.34% with an open-circuit voltage (Voc) = 0.57 V, a short-circuit current density (Jsc) = 4.29 mA/cm2, and a fill factor (FF) = 0.27. This suggests a useful application in further fabrication of quantum dots/polymers based solar cells.
Thi Thao Tran
Quang Trung Tran
Van Truong Vo
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2016-05-20T09:05:44Z
2016-05-20T09:06:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1510
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1510
2016-05-20T09:05:44Z
Nghiên cứu cố định protein BSA lên bề mặt polymer PDMS chức năng định hướng ứng dụng trong chế tạo cảm biến sinh học
Thi Ngoc Tran
Hong Nhung Luong
Thi Hien Le
lehien@vnu.edu.vn
Thi Huyen Vu
2016-03-27T08:07:29Z
2016-03-27T08:07:29Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1487
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1487
2016-03-27T08:07:29Z
Results of some R-D projects on the non-conventional (green) energy
Non-conventional energy or Green energy includes Solar, Wind, Sea-waves energy and also Energy-efficient windows are subjects that are being intensively carried-out in University of Engineering and Technology, Vietnam National University (UET-VNU) for further application in Vietnam. In this report we present main research results concerning to solar energy. There are R-D groupe of projects in following fields: The first, research and application of how to use solar radiation most efficiently, so called "Energy-Efficient Windows", The second, research and produce of solid-state lighing sources - the most efficiently lighting lamps; and the last, research of new type of solar cells, such as Organic Solar Cells (OSC).
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
2015-11-19T07:29:25Z
2015-11-19T09:20:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1260
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1260
2015-11-19T07:29:25Z
Effect of Silver Nanowire Dimension to Ammonia Adsorption of Graphene-silver Nanowires Hybrid
In this report, we study the effect of silver nanowires (AgNws) dimension to electrical properties of rGO/AgNws hybrid. The alteration of these electrical properties leads the difference of ammonia sensibility of the rGO/AgNws hybrid based sensing devices. When the rGO is accompanied by AgNws of different sizes from ∼500$ nm to >10μm, the ammonia sensitivity of these hybrids change from 60% to 340% alteration compared with the bare rGO material.
Tran My Hoa Huynh
Thi Thu Hoang
Phan Phuong Ha La
Ha Phuong Le
Quang Trung Tran
Van Thuan Nguyen
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Minh Hanh Phan
2015-11-19T07:26:51Z
2015-11-19T07:28:49Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1262
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1262
2015-11-19T07:26:51Z
Conducting Nano Films based on Multi-Walled Carbon Nanotubes and Poly(3,4-ethylene Dioxy, Thiophene-poly(styrene sulfonate) for Organic Light-Emitting Diode
It is well known that multi-walled carbon nanotubes (MWCNTs) are an excellent nanomaterial. In this paper, the nanocomposite ultra-thin films were fabricated consisting of MWCNTs and poly (3,4-ethylene dioxy thiophene-poly(styrene sulfonate) (PEDOT-PSS) for organic light-emitting diode (OLED). The field-emission scanning electron microscopy (FESEM) images of MWCNTs thin films show that the diameter of MWCNTs are 10–30 nm and their length is 300–500 nm. Electrical and optical properties of the films are investigated and the sheet resistance can reach minimum value at 36.5 Ω sq−1 and the transparency of the film is about 80%. The current density–voltage (J–V) characteristics of the devices were also studied.
Phuong Hoai Nam Nguyen
namnph@vnu.edu.vn
2015-11-19T04:16:07Z
2015-11-19T04:17:48Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1252
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1252
2015-11-19T04:16:07Z
Synthesis and Characterization of Ce-doped Y3Al5O12 (YAG:Ce) Nanopowders used for Solid State Lighting
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Ngoc Chung Do
chungdn@vnu.edu.vn
Ngoc Hieu Do
Thi Thao Tran
thaott@vnu.edu.vn
Van Truong Vo
2015-11-19T04:14:55Z
2015-11-19T09:22:13Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1256
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1256
2015-11-19T04:14:55Z
Photoluminescence Quenching of Nanocomposite Materials Used for Organic Solar Cells
In this work, we have studied the photoluminescence (PL) quenching of two polymeric composites, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT) in presence of nc-TiO2 particles by PL- spectroscopy. PL quenching values are 19.2\% and 45.5\%, for MEH-PPV+nc-TiO2 and P3HT+nc-TiO$_{2}$, respectively. The obtained results on the relationship of PL quenching and photoelectrical efficiency (PCE) of an OSC showed that the quenching coefficient of a semiconducting polymer can be considered as apreliminarycriterion for choosing an appropriate polymeric composite being used for OSC preparation. Under illumination of solar energyof 56 mW/cm2, P3HT+TiO2 based OSC possess FF, V$_{OC}$, J$_{SC}$ and PCE of 0.64, 0.243 V, 1.43 mA/cm2 and 0.45\%, respectively.
Thi Thao Tran
thaott@vnu.edu.vn
Ngoc Chung Do
chungdn@vnu.edu.vn
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Van Truong Vo
2015-11-19T04:10:36Z
2015-11-19T09:20:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1254
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2015-11-19T04:10:36Z
Annealing Effect on the Ionic conductivity of La0,67-xLi3xTiO3 made by Double Mechanical Alloying Method
Perovskite La2/3-xLi3xTiO3 with x = 0.11 (called LLTO11) powders were prepared by double mechanical alloying method from TiO2 (99.99%), Li2CO3, (99.99%) and La2O3 (99.9%) powders, in ideal cation stoichiometry for La2/3-xLi3xTiO3. The obtained single phase of LLTO11 powder was isostatically pressed under a pressure of 450 MPa and annealed at a temperature ranging from 1,100 °C to 1,250 °C. Optimal morphology and grain structure for the ionic conductivity of the samples were achieved at annealing
temperature of 1,200 °C. For this ceramic, the lithium ionic grains and grain-boundaries conductivities at room temperature possess a value of 1.5 × 10-3 S/cm and 4.8 × 10-5 S/cm, respectively. The improvement in the grain-boundaries conductivity was explained due to the decrease of the number of grains, included grain boundaries and the diminution of the pores in LLTO samples annealed at 1,200 °C. The obtained results suggest useful applications of La(2/3)-xLi3xTiO3 (x = 0.11) ceramics for the production of the solid state electrolytes,for high-temperature Li-ionic batteries, in particular.
Dinh Trong Le
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Duy Long Pham
2015-11-19T04:05:50Z
2015-11-19T04:07:09Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1255
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2015-11-19T04:05:50Z
Characterization of Organic Solar Cells Made from Hybrid Photoactive Materials of P3HT:PCBM/nc-TiO2
Nanorod-like TiO2 was grown on Ti wafers by annealing at 700oC for 1.5h. Hybrid Organic Solar Cells (HOSC) were then prepared by using a nano hybrid material of P3HT:PCBM/nc-TiO2. The HOSC have the laminar structure of Al/P3HT:PCBM/TiO2/Ti, where P3HT:PCBM were made by spincoating. Under illumination of the standard light wavelength ( = 470 nm), the polymer luminescence quenching was observed at the heterojunctions, resulting in the charge separation. With an illumination power of 56 mW/cm2, a best hybrid solar cell exhibited an open circuit voltage of 0.60 V, short cut current density of 4.60 mA/cm2, fill factor of 0.54 and photoelectrical conversion efficiency of 2.6 %. This suggests a useful application for fabricating “reverse” OSCs, where the illumination light goes-in through the windows of Al-electrode cathode, instead of the indium tin oxide (ITO). For these devices, the Ohmic contact of wires to metallic Ti-substrates can be made much better than to ITO electrode. Keywords: Organic Solar cell (OSC); nanorod-like TiO2, P3HT:PCBM/nc-TiO2 heterojunctions; polymer quenching.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Thi Thao Tran
thaott@vnu.edu.vn
Ngoc Chung Do
chungdn@vnu.edu.vn
2015-11-09T05:51:15Z
2015-11-09T05:53:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1264
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2015-11-09T05:51:15Z
Critical Behavior of Y-doped Nd0.7Sr0.3MnO3 Manganites Exhibiting the Tricritical Point and Large Magnetocaloric Effect
We have determined the values of critical exponents of two polycrystalline samples (Nd1−xYx)0.7Sr0.3MnO3 (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties. The results reveal the samples exhibiting the crossover of first-order and second-order phase transitions, where the exponent values β = 0.271 and γ = 0.922 for x = 0, and β = 0.234–0.236 and γ = 1.044–1.063 for x = 0.07 determined by using modified Arrott plots and static-scaling hypothesis are close to those expected for the tricritical mean-field theory (β = 0.25 and γ = 1.0). Particularly, the TC of x = 0 and 0.07 can be any value in the temperature ranges of 240–255 K and 170–278 K, respectively, depending on the magnitude of applied magnetic field and determination techniques. Around the TC, studying the MC effect of the samples has revealed a large magnetic-entropy change (ΔSm) up to ∼8 J/kg K for the applied field interval ΔH = 50 kOe, corresponding to refrigerant capacity values of 200–245 J/kg. These phenomena are related to the crossover nature and the persisting of FM/anti-FM interactions even above the TC, as further confirmed by electron-spin-resonance data, Curie–Weiss law-based analyses, and an exponential parameter characteristic of magnetic order n = dLn|ΔSm|/dLnH.
The Long Phan
T.A Ho
Duc Thang Pham
pdthang@vnu.edu.vn
Q.T Tran
D. Thanh Tran
X. Phuc Nguyen
M. H Phan
T. Huy Bui
S.C. Yu
2015-11-09T05:46:23Z
2015-11-09T05:56:39Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1265
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2015-11-09T05:46:23Z
Inhomogeneous ferromagnetism and spin-glass-like behaviour in (Nd1-xYx)0.7Sr0.3MnO3 with x = 0.21 - 0.35
The magnetic properties of polycrystalline ceramic samples (Nd1-xYx)0.7Sr0.3MnO3 with x = 0.21 - 0.35 were studied by means of dc magnetization and ac susceptibility measurements. Experimental results reveal a strong decrease of the ferromagnetic (FM)-paramagnetic phase-transition temperature (TC) from 97 to 65 K as increasing x from 0.21 to 0.35, respectively. There is magnetic inhomogeneity associated with short-range FM order. Particularly, the samples undergo a spin-glass (SG) phase transition at the so-called blocking temperature (TB) below TC, which shifts toward lower temperatures with increasing the applied field, Hex; TB → Tg (the SG phase-transition temperature) as Hex → 0. The existence of the SG behavior in these samples was also confirmed by frequency (f) dependences of the ac susceptibility. For the in-phase/real component, χ'(T), it shows a frequency-dependent peak at the SG freezing temperature (Tf); Tf → Tg as f → 0. Dynamics of this process were analyzed by means of the slowing down scaling law, τ/τ0 ∝ (Tf /Tg - 1)-zv, where τ0 and zv are the characteristic time and critical exponent, respectively. Fitting the experimental Tf (f) data to the scaling law gave the results of zv = 10.1-12.3 and τ0 = 10-21-10-15s. These values are different from those expected for canonical SG systems with zv = 10 and τ0 = 10-13s, revealing the cluster-SG behavior of (Nd1-xYx)0.7Sr0.3MnO3 samples. Notably, the increase in Y content leads to the shift of τ0 and zv values toward those of canonical SG systems, which is ascribed to an expansi- n of SG clusters.
T.L Phan
V.D Nguyen
T.A Ho
V. Khiem Nguyen
D. Thanh Tran
X. Phuc Nguyen
Duc Thang Pham
pdthang@vnu.edu.vn
S.C. Yu
2015-11-08T08:54:43Z
2015-11-08T08:55:51Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1266
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2015-11-08T08:54:43Z
Electrical Field Induced Magnetization Switching in CoFe/NiFe/PZT Multiferroics
In this paper, we have investigated the change in magnetization of multiferroic material, based on magnetic nanostructured CoFe/NiFe film grown on the piezoelectric lead zirconate titanate (PZT), under the effect of the strain originated from PZT layer. In this material, a converse magnetoelectric effect and especially, an electric field-induced magnetic anisotropy and magnetization switching process have been observed at the changing stages of applied electric voltage. In addition, a significant relative change in magnetization, above 100%, is obtained, which facilitates practical applications of the materials. This opens possibilities in achieving new types of memory devices, the low energy consumption devices, as well as other functionalities, such as voltage-tunable field sensing. A simple theory based on strain-mediated magnetic-electric coupling is also presented to understand the origin of the change in magnetic properties of the materials.
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Thai Ha Pham
Viet Cuong Le
cuonglv@vnu.edu.vn
T. Long Pham
Duc Thang Pham
pdthang@vnu.edu.vn
2015-11-08T08:53:38Z
2015-11-08T08:54:27Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1267
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1267
2015-11-08T08:53:38Z
Influence of the change in oxidation number of Mn on magnetic properties of BaTi1-xMnxO3
We prepared BaTi1-xMnxO3 samples (x = 0 and 0.05) by standard solid-state reaction at 700 degrees C and 900 degrees C in an Ar ambient to change oxidation number of Mn dopants. The fabricated samples were then studied structural characterization and electronic structures by means of X-ray diffraction and absorption, and Raman scattering and electron-spin-resonance spectrometers. We found oxidation numbers 2+ and 3+ of Mn ions coexisting in BaTi1-xMnxO3 with x = 0.05, where the Mn2+/Mn3+ ratio is about one for the sample annealed at 700 degrees C. These Mn ions prefer locating at the Ti site in the tetragonal BaTiO3 host lattice. In particular, there is a change in the oxidation number of Mn2+ -> Mn3+ when the annealing temperature changes from 700 degrees C to 900 degrees C. Their magnetic properties are accordingly changed. Meanwhile, annealing pure BaTiO3 in an Ar ambient at 700 degrees C and 900 degrees C does not lead to ferromagnetic (FM) order; they are almost diamagnetic. With the obtained results, we believe that FM order in Mn-doped BaTiO3 annealed in an Ar ambient is associated with exchange interactions of Mn2+ ions mediated by oxygen vacancies rather than associated with Mn3+ ions.
Influence of the Change in Oxidation Number of Mn on Magnetic Properties of BaTi1−xMnxO3.
T. L Phan
D. Thanh T.
T. A Ho
Duc Thang Pham
pdthang@vnu.edu.vn
S.C. Yu
2015-11-08T08:51:53Z
2015-11-09T05:56:20Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1268
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1268
2015-11-08T08:51:53Z
The Temperature-Sensitivity of a Critical Electric Field Induced Magnetic Easy-Axis Reorientation Ferromagnetic/Ferroelectric Layered Heterostructures
We have investigated the effects of temperature on the magnetic easy axis reorientation (EARs) in polycrystalline ferromagnetic (FM) nano-scale thin films, i.e. (001)-oriented cubic films such as Fe, Ni, CFO and (0001)-oriented hexagonal films such as Co, grown on ferroelectric (FE) substrates, for example PZT, BTO substrates. The model of FM/FE bilayered heterostructures has been applied to study the total free energy of the FM films. By minimizing this energy, we have shown that temperature has a significant effect on a critical electric field induced magnetic reorientation.
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Dinh Long Dang
ddlong@vnu.edu.vn
Thai Ha Pham
Ngoc Trung Nguyen
Hong Cong Pham
Dinh Duc Nguyen
ducnd@vnu.edu.vn
2015-11-07T15:30:10Z
2015-11-07T15:31:43Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1269
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2015-11-07T15:30:10Z
Influence of Magnetic Field on Positioning of Some Molecules
Viet Cuong Le
cuonglv@vnu.edu.vn
Thi Hien Nguyen
Duc Thang Pham
pdthang@vnu.edu.vn
2015-11-07T15:28:36Z
2015-11-07T15:29:48Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1270
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1270
2015-11-07T15:28:36Z
Room-temperature Ferromagnetism in Nickel-Doped Wide Band Gap Ferroelectric Bi0.5K0.5TiO3 Nanocrystals
Van Thiet Duong
Duc Cuong Do
Huu Bac Luong
Viet Cuong Le
cuonglv@vnu.edu.vn
Dang Khoa Ha
Duc Dung Dang
2015-11-07T15:27:17Z
2015-11-07T15:28:22Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1271
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2015-11-07T15:27:17Z
A Simple Process to Fabricate Micro Flux Sources with High Magnetic Field Gradient
In this paper, we present a fabrication process to produce the micro-sized magnetic structures based on the hard magnetic powders. Under the magnetic field originated from a micro patterned hard magnetic film, these magnetic powders are magnetically aligned to form arrays of the micro magnets on a polydimethysiloxane (PDMS) substrate. The high magnetic field gradient and stable magnetic flux can be obtained at certain micro-sized area on the surface of the micro magnets. The fabricated structures have been used for trapping iron oxide particles. Generally this fabrication process is simple, low cost and the micro magnets can be used for further applications in biology, medicine and beyond.
Viet Cuong Le
cuonglv@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
The Hien Nguyen
thehien@vnu.edu.vn
2015-11-07T15:26:12Z
2015-11-07T15:26:59Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1272
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1272
2015-11-07T15:26:12Z
Influence of magnetic field applied on magnetic properties of electrodeposited co-ni-p nanowires
Tuan Tu Le
Van Thiem Luu
Duc Thang Pham
pdthang@vnu.edu.vn
2015-11-07T15:25:12Z
2015-11-07T15:25:53Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1273
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1273
2015-11-07T15:25:12Z
Structure and magnetic properties of PZT/CoCr heterostructures
The microstructure, crystallographic structure and magnetic properties of ferroelectric-ferromagnetic PZT/CoCr heterostructures have been investigated by using XRD, SEM and VSM.~Upon applying an electric field, the in-plane magnetization of the heterostructures decreases at various bias magnetic fields. The change in magnetization and the magnetization reversed voltage were obtained. The results demonstrate that the change in magnetic anisotropy can be controlled by electric field via strain-mediated magnetoelectric coupling.
Thi Minh Hong Nguyen
hongntm@vnu.edu.vn
Duc Thang Pham
pdthang@vnu.edu.vn
Thai Ha Pham
2015-11-07T15:23:18Z
2015-11-07T15:23:50Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1275
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2015-11-07T15:23:18Z
Optimizing Active Layer Morphology of a Bulk Heterojunction Organic Photovoltaic Cell
Van Chau Dinh
dinhchau@vnu.edu.vn
Van Thuong Dinh
2015-11-07T13:24:55Z
2015-11-09T05:59:16Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1277
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1277
2015-11-07T13:24:55Z
Application of Bond Valence Method to Estimate the Valence Charge Distribution in the Metal-to-Oxygen Bonding Spheres in Perovskites
Van Chau Dinh
dinhchau@vnu.edu.vn
Van Thuong Dinh
Nam Nhat Hoang
nhathn@vnu.edu.vn
Thi Hang Nguyen
2015-11-07T13:24:00Z
2015-11-09T05:55:17Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1278
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1278
2015-11-07T13:24:00Z
Structure and Electrical Properties of the Thin Gold Leaves Fabricated by Vietnam Traditional Laminating Technology
The structure and electrical properties of the thin gold leaves fabricated by Vietnam traditional laminating technology are introduced. The gold leaves are usually created with the average size of 3x3cm, and 200nm thickness, they can easily be broken when handling carelessly. By the measurements of X-ray Diffraction (XRD), and Electron Scanning Microscopy (SEM), the structure and surface morphology were investigated. We have also measured the absorption spectra and determined the resistivity of the samples and found that the gold films possessed the Ca impurities stuck on the surface of the leaves. The conductivity of the films is relatively higher and the absorption maximum is red-shifted in comparison with that of the bulk.
Khac Thuan Nguyen
Nam Nhat Hoang
nhathn@vnu.edu.vn
2015-11-07T13:21:25Z
2015-11-07T13:23:44Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1279
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1279
2015-11-07T13:21:25Z
Structure and Properties of Double Perovskite System La2Co1−xFexMnO6
The Tan Pham
Huyen Yen Pham
Nam-Nhat Hoang
nhathn@vnu.edu.vn
Quang Hoa Nguyen
2015-11-07T13:19:20Z
2015-11-09T05:56:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1280
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2015-11-07T13:19:20Z
Electrical and Magnetotransport Properties of La0.7Ca0.3Mn1−xCoxO3
This paper presents a detailed study on the Co-doping influence on the electrical and magnetotransport properties of La0.7Ca0.3Mn1-xCoxO3(x = 0.09-0.17) prepared by solid-state reaction. Magnetic measurements versus temperature revealed a gradual decrease of the magnetization (M) and Curie temperature (T-C) with increasing Co concentration (x). The T-C values vary from 194 to 159 K as changing x from 0.09 to 0.17, respectively. H/M versus M-2 performances around T-C prove the x = 0.09 sample undergoing a first-order magnetic phase transition (FOMT) while the samples with x >= 0.11 undergo a second-order magnetic phase transition (SOMT). The other with x = 0.10 is considered as a threshold concentration of the FOMT-SOMT transformation. Considering temperature dependences of resistivity, rho(T), in the presence and absence of the magnetic field, the samples (excepting for x = 0.17) exhibit a metal-insulator transition at T (P) = 60-160 K, which shifts toward lower temperatures with increasing x. In the metallic-ferromagnetic region, the rho(T) data are well fitted to a power function rho(T) = rho(0) + rho(2) T-2 + rho(4.5) T-4.5. This indicates electron-electron and electron-magnon scattering processes are dominant at temperatures T < T (P). In addition, the conduction data at temperatures T > theta(D)/2 (theta(D) is the Debye temperature) and T (P) < T < theta(D)/2 obey the small-polaron and variable-range hopping models, respectively. The values of activation energy E-p, and density of states at the Fermi level N(E-F) were accordingly determined. Here, N(E-F) increases while E-p decreases when an external magnetic field is applied. We also have found that N(E-F) increases when materials transfer from the FOMT to the SOMT, and N(E-F) value becomes smallest for the sample having the coexistence of the FOMT and SOMT (i.e., x = 0.10).
Dang Thanh Tran
T. L Phan
Quoc Thanh Phung
Nam-Nhat Hoang
nhathn@vnu.edu.vn
Anh Tuan Duong
S. C Yu
2015-11-07T13:16:44Z
2015-11-07T13:19:00Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1281
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1281
2015-11-07T13:16:44Z
Optical and Magnetic Properties of Mn-Doped ZnS Nanoparticles Synthesized by a Hydrothermal Method
The Mn-doped ZnS nanoparticles with T2d - F4̅3m cubic structure and an average crystalline size of about 16 nm were synthesized using the hydrothermal method at 220 °C for 15 h from Zn(CH3COO)2 (0.1M), Mn(CH3COO)2 (0.01M), and Na2S2O3 (0.1 M) as the precursors. The appearance of characteristic photoemission bands of Mn2+ (3d5) ions at 390, 430, 467, and 493 nm in the photoluminescence excitation spectra while monitoring the yellow-orange band at 585 nm showed that the Mn2+ (3d10) ions substituted for Zn2+ (3d10) ions in ZnS matrix and caused the ferromagnetism of Mn-doped ZnS nanoparticles. The dependence of photoluminescence, photoluminescence excitation spectra, and magnetization curves on Mn content and the wavelength of excitation radiation were reported.
Hong Van Bui
Hoang Nam Nguyen
Nam-Nhat Hoang
nhathn@vnu.edu.vn
Thanh Trung Truong
Van Ben Pham
2015-11-07T04:44:47Z
2015-11-07T04:46:06Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1282
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2015-11-07T04:44:47Z
The Changes in Antigenic Components of Vibrio Cholerae Strains Isolated in Vietnam
Toàn bộ tế bào của các chủng Vibrio cholerare typ huyết thanh Inaba và typ huyết thanh Ogawa (chủng I389 và O395) được sử dụng để gây miễn dịch trên thỏ thu kháng huyết thanh (KHT). Các KHT này được ký hiệu là KHTInaba và KHTOgawa được dùng để thực hiện phản ứng miễn dịch với các thành phần kháng nguyên của 25 chủng V. cholerae phân lập từ 5 tỉnh thành của Việt Nam và hai chủng chuẩn I389 và O395) bằng kỹ thuật Western-blot. Phân tích kết quả lai miễn dịch cho thấy, có tổng số 11 thành phần kháng nguyên (TPKN) có kích thước khoảng 79kDa, 62kDa, 52kDa, 45kDa, 42kDa, 38kDa, 35kDa, 31kDa, 26kDa, 23kDa và 20kDa. Có 6 TPKN chung giữa 25 chủng với kích thước 79kDa, 62kDa, 45kDa, 35kDa, 31kDa và 20kDa, trong đó các kháng nguyên 45kDa, 31kDa và 20kDa có kích thước trùng với kháng nguyên OmpS, Omp- 31kDa và TcpA -là những kháng nguyên quan trọng trong nghiên cứu phòng bệnh tả. Ngoài ra có 23/25 chủng có kháng nguyên 42kDa tương đương với protein OmpT- cũng là kháng nguyên quan trọng trong phòng bệnh; 5/25 chủng không có kháng nguyên 38kDa và 23kDa và 11/25 chủng không có kháng nguyên 26kDa. Các chủng 17-19 của Hà Nội và 22-25 của Hải Phòng xuất hiện các thành phấn kháng nguyên (TPKN) giống hoàn toàn với kháng nguyên của chủng chuẩn I389 thuộc typ huyết thanh Inaba. Các chủng 1AG, 5HN, 6HN, 8HN, 20HN và 21HN có TPKN giống cả chủng I389 và O395. Các chủng 2AG, 3AG, 4CM, 7HN, 9HN, 10HN, 11HP, 12AG, 13HP, 14HP, 15HN và 16QN lại thiếu hụt một vài TPKN so với chủng I389. Tuy nhiên, biến đổi kháng nguyên của chúng chỉ là sự thiếu hụt TPKN chứ không phải xuất hiện TPKN mới. Các kết quả nghiên cứu này có thể được xem là nền tảng ban đầu cho các nghiên cứu về miễn dịch và dự phòng bệnh tả
Thi Quyen Ha
quyenht@vnu.edu.vn
Duy Khang Dinh
2015-11-07T04:42:50Z
2015-11-09T05:54:56Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1285
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1285
2015-11-07T04:42:50Z
Huge on-current Ferroelectric-gate Thin Film Transistor with Solution-Processed Indium Tin Oxide Channel
We have demonstrated ferroelectric-gate thin film transistors (FGTs) using solution-processed indium tin oxide (ITO) film as an oxide-semiconductor channel and Pb1.2Zr0.4Ti0.6O3 ferroelectric film as a gate insulator on a poly-crystalline 100-nm-STO/SiO2/Si substrate or a single-crystalline STO(111) wafer. The FGTs show a clear memory function with an on/off current ratio of more than 105 and a memory window of 2 V. It is interesting that even using solution-processed ITO channel, the saturated “on” current in the FGT reached as high as 4.6 mA at operation voltages of 8 V, corresponding to a field-effect mobility of 8.0 cm2/Vs, for the case of single-crystalline STO(111) wafer. The large “on” current is mainly due to the huge induced charge of the ferroelectric gate, compensated to the small mobility of the ITO channel. Keywords: PZT, Thin film transistor (TFT), ferroelectric, ITO, FeRAM.
Hong Minh Do
Thi Huyen Trang Vu
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2015-11-07T04:41:23Z
2015-11-07T04:42:37Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1286
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2015-11-07T04:41:23Z
Low-temperature PZT Thin-film Ferroelectric Memores Fabicated on a Glass Substrate
H. Minh D.
Q. Hoa N.
H. Tiep N.
Nang Dinh Nguyen
dinhnn@vnu.edu.vn
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2015-11-07T04:39:51Z
2015-11-09T05:57:15Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1287
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1287
2015-11-07T04:39:51Z
Operation Stability of Ferroelectric-gate Thin-Film Transistor with LaTaO/PZT Stacked Structure
T.H. Trang V.
V. Dung T.
H. Minh D.
Q. Hoa N.
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
2015-11-07T04:38:37Z
2015-11-07T04:39:36Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1288
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1288
2015-11-07T04:38:37Z
Effect of storage time and pretreatment on seed germination of the threatened coniferous species Fokienia hodginsii
We report the effects of storage time and pretreatment on seed germination of Fokienia hodginsii. Lower mean germination was observed in seeds stored for 2 years (6.41 ± 1.23 seeds/replicate) compared with those stored for 1 year (8.52 ± 1.06 seeds/replicate). Seeds collected from a southern location had statistically higher mean germination (9.67 ± 1.28 seeds/replicate) than those collected from a northern location (7.99 ± 1.36 seeds/replicate). Higher mean T50 was observed in seeds stored for 2 years (37.02 ± 4.43 days) compared with those stored for 1 year (30.69 ± 5.06 days). Mean germination of untreated fresh seeds was 9.97 ± 1.34 seeds/replicate and that of treated fresh seeds in 60°C water was 12.95 ± 1.24 seeds/replicate. Fresh seeds treated with 50°C and 70°C water had a significantly lower mean germination compared with untreated seeds and seeds treated in 60°C water. Mean T50 was lowest in seeds treated with 60°C water.
Duc Quang Nguyen
quangbio@vnu.edu.vn
Thi Phuong Hoa Phan
Van Tan Dao
2015-08-12T03:40:02Z
2015-08-14T07:50:20Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1284
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1284
2015-08-12T03:40:02Z
120 nm Channel Length Ferroelectric Gate Thin-Film Transistor by Nano-imprinting Lithography
K. Nagahara
Nguyen Quoc Trinh Bui
trinhbnq@vnu.edu.vn
E. Tokumitsu
S. Inoue
T. Shimoda
2015-08-12T03:37:36Z
2015-08-12T03:37:36Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1283
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/1283
2015-08-12T03:37:36Z
Preparation of Positively Charged Membrane from Natural Rubber Latex Blending with Chitosan
Film formation of natural rubber latex (NRL) blended with various concentrations of chitosan was investigated. Atomic force microscopy (AFM) images clearly showed that the NRL film covered chitosan phase. Roughness of the films which was calculated from AFM image increases with increasing chitosan concentration. Miscibility of NRL and chitosan in solution was investigated by using dynamic mechanical thermal analysis (DMTA) and found that chitosan incorporated with NRL less than 40 weight percentage (wt%) was partially miscible. Films of the chitosan blending with higher NRL contents exhibited two peaks of glass transition temperatures. Interfacial polarization and dielectric properties of polymer films were improved with increasing NRL contents. Chemical structure of the blends was characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).
Taweepreda Wirach
Tuaybut Supawadee
Puangmanee Sineenart
Dang Khoa Tran
khoatd@vnu.edu.vn
2015-01-29T07:45:55Z
2015-01-29T07:46:42Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/707
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/707
2015-01-29T07:45:55Z
Absorption and Radiation Transitions in Configuration of Mn-Doped ZnS Nanoparticles Synthesized by a Hydrothermal Method
Bui Hong Van
Pham Van Ben
Tran Minh Thi
Hoang Nam Nhat
2013-06-13T06:00:45Z
2016-05-21T03:44:55Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/155
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/155
2013-06-13T06:00:45Z
Metglas/PZT-Magnetoelectric 2-D Geomagnetic Device for Computing Precise Angular Position
A magnetoelectric two-dimensional (2-D) geomagnetic device for the precisely angular position computation is provided. The magnetic sensor module consists of two Metglas/PZT magnetoelectric 1-D sensors in an orthogonal arrangement. The sensor signals are excited and detected by a self-made digital lock-in amplifier. For mapping output sensor signals, normalization was performed on the operational module. Both the spatial (azimuth and pitch) angles are then easily computed while rotating and/or swinging the sensor module. This simple and low-cost geomagnetic device is integrated with mobile transceivers for automatic determination and control of the latter antenna direction with respect to the position of the geostationary satellite in communication.
Huu Duc Nguyen
ducnh@vnu.edu.vn
Dinh Tu Bui
Thi Ngoc Nguyen
V. Lap
Thi Huong Giang Do
giangdth@vnu.edu.vn
2013-03-27T06:27:03Z
2013-04-01T06:59:25Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/143
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/143
2013-03-27T06:27:03Z
Magnetic, Mossbauer and magnetostrictive studies of amorphous Tb(Fe0.55Co0.45)1.5 films
The Tb(Fe0.55Co0.45)1.5 films were fabricated by rf magnetron sputtering from a composite target. Samples were investigated by means of x-ray diffraction, vibrating sample magnetometer, conversion electron Mössbauer spectra, and magnetostriction measurements. The as-deposited film is an amorphous alloy with a perpendicular magnetic anisotropy and an intrinsic magnetostriction λ=1080×10-6 in an applied field of 0.7 T. In this state, it was determined that the hyperfine field Bhf=23.5 T and the cone-angle between the Fe moment direction and the film-normal direction β=12°. After annealing in the temperature range of TA=250–450 °C the amorphous structure still remained, however the anisotropy was changed to a parallel one. The soft magnetostrictive behavior has also been improved by these heat treatments: the parallel magnetostriction λ||=465×10-6 was almost developed in low applied fields of less than 0.1 T and, especially, a huge magnetostrictive susceptibility χλ=dλ||/d(μ0H)=1.8×10-2 T-1 was obtained at μ0H=15 mT. © 2000 American Institute of Physics.
T.M. Danh
danhtm@vnu.edu.vn
N.H. Duc
ducnh@vnu.edu.vn
H. N. Thanh
J. Teillet
2013-03-27T06:25:31Z
2013-03-27T06:25:31Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/138
This item is in the repository with the URL: http://eprints.uet.vnu.edu.vn/eprints/id/eprint/138
2013-03-27T06:25:31Z
Ab Initio Study of the Optical Phonons in One-Dimensional Antiferromagnet Ca2CuO3
We present the cluster-model ab initio study of the optical phonons in the one-dimensional antiferromagnet Ca2CuO3 based on the Hartree–Fock self-consistent field calculation with the 3-21G basis set. The obtained results showed very good agreement with the observed data. The Cu–O bands generally showed lower shifts in Ca2CuO3 than in pure CuO and were primarily composed of the vibrations of the oxygen in static host lattice, whereas the Cu movements only happened in the collective lattice vibrations. An almost complete classification of the forbidden phonons is presented.
Nam-Nhat Hoang
Thu-Hang Nguyen
Chau Nguyen
2013-03-27T06:17:43Z
2013-06-29T04:34:42Z
http://eprints.uet.vnu.edu.vn/eprints/id/eprint/140
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2013-03-27T06:17:43Z
Large Magnetostrictive Susceptibility in Tb2013 FeCo/FeCo Multilayers
Tb(Fe0.55Co0.45)1.5/Fen and Tb(Fe0.55Co0.45)1.5/(Fe0.5Co0.5n multilayers were fabricated by rf-magnetron sputtering from composite targets. Magnetostriction was measured using an optical deflectometer. The as-deposited films showed a soft magnetic and magnetostrictive character, with a coercive field μ0Hc=5 mT and a parallel magnetostrictive susceptibility χλ||=dλ||/d(μ0H)=1.4×10-2 T-1. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5×10-2 T-1 in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. © 2001 American Institute of Physics.
N.H. Duc
ducnh@vnu.edu.vn
T.M. Danh
danhtm@vnu.edu.vn
N. A. Tuan
J. Teillet