Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513
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Authors: Pham, Huu Kien; Pham, Mai An; Nguyen, Hong Linh; Giap, Thuy Trang (2019) - The FeB nanoparticle (NP) consisting of 5000 particles (4500 Fe atoms and 500 B
atoms) has been investigated by means of molecular dynamics (MD) simulation. When the
amorphous FeB nanoparticle is annealed at temperature of 900 K for a long time, it is crystallized
into bcc crystalline structure. The simulation shows that the sample undergoes crystallization via
the nucleation mechanism. During the crystallization, B atoms diffuse to the boundary region of Fe
crystal. The crystal growth proceeds when this boundary region attains specific properties which
are defined by the fraction of B atoms and the energies of AB-atoms and CB-atoms. Further our
study indicates that the crystal...
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- Article
Authors: Nguyen, Thi Thanh Ha (2019) - Molecular dynamic simulation is employed to study the structural properties and
diffusion mechanism in sodium silicate (Na2O.4SiO4). Structural characteristics are clarified through
the pair radial distribution function, distribution of SiOx coordination units, network structure. The
simulation results reveal that the structure of Na2O.4SiO4 liquid consists of one Si-O network that
is mainly formed by SiO4 units. The spatial distribution of sodium is non-uniform; sodium tends to
be in the non-bridging oxygen-simplexes and in larger-radius simplex. Moreover, the sodium
density for non-bridging oxygen region is significantly higher than the one for others region. Further,
we find...
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- Article
Authors: Pham, Ngoc Thang; Le, Thai Hung; Do, Tuan Long; Nguyen, Quang Bau (2019) - The influence of confined acoustic phonons on the Hall Coefficient (HC) in a Cylindrycal
Quantum Wire (CQW) with an infinite potential (for electron – confined acoustic phonons
scattering). Consider a case where CQW is placed in a perpendicular magnetic field �⃗ , a constant -
electric field � ⃗⃗⃗⃗1 and an intense electromagnetic wave �⃗ = � ⃗⃗⃗⃗0 ��� Ω�. By using the quantum kinetic
equation for electrons interacting with Confined Optical Phonon (COP), we obtain analytical
expressions for (HC), which are different from in comparison to those obtained for the HC in the
case of normal bulk semiconductor and in the case of cylindrycal quantum wire with electron –
unconfined phono...
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- Article
Authors: Dao, Thu Hang; Nguyen, Thi Hoa; Nguyen, Thi Thanh Nhan; Nguyen, Quang Bau (2019) - Ettingshausen coefficient (EC) in the compositional semiconductor superlattice (CSSL)
under the influence of electromagnetic wave (EMW) is surveyed by using the quantum kinetic
equation for electrons. The analytical expressions of the Ettingshausen coefficient are numerically calculated for the GaAs/AlGaAs compositional semiconductor superlattice. It have been showed that the appearance of EMW has changed the EC’s value and the EC decreases nonlinearly when the temperature increases. Studying the dependence of EC on the magnetic field, we discovered that the superlattice period strongly affects the quantum magneto - thermoelectric effect. When the superlattice period is small, the q...
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- Article
Authors: Trinh, Tuan Anh; Bui, Thi Hang (2019) - To find a suitable material for Fe-air battery anode, Fe2O3 nanoparticles (nm) and
microparticles (µm) were used as active materials and Acetylene Black carbon (AB) as additive to
prepare Fe2O3/AB composites. The effect of grain size of iron oxide particles and additives on the
electrochemical behavior of Fe2O3/AB composite electrodes in alkaline solution have been
investigated using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance
spectroscopy (EIS) measurements. Iron oxide nanoparticles provided better cyclability than iron
oxide microparticles. Impedance of electrode increased during cycling but the nm-Fe2O3/AB
electrode gave smaller resistance th...
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- Article
Authors: Khuc, Van Phu; Le, Xuan Doan; Nguyen, Van Thanh (2019) - In this paper, the governing equations of rectangular plates with variable thickness
subjected to mechanical load are established by using the classical plate theory, the geometrical
nonlinearity in von Karman-Donnell sense. Solutions of the problem are derived according to
Galerkin method. Nonlinear dynamic responses, critical dynamic loads are obtained by using
Runge-Kutta method and the Budiansky–Roth criterion. Effect of volume-fraction index k and
some geometric factors are considered and presented in numerical results.
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- Article
Authors: Nguyen, Dinh Duc (2019) - This research demonstrates an analytical method for investigation vibration and dynamic
response of plates structure which made from 2-Dimensional (2D) penta-graphene. The density
functional theory is used to figure out the elastic modulus of single layer penta-graphene. The
classical plate theory is applied to determine basic equations of 2D penta-graphene composite plates.
The numerical results obtained using the Bubnov-Galerkin method and Rung-Kutta method. The
results in this research showed high agreement when it is compared with the other study. The results
demonstrate the effect of shape parameters, material properties, foundation parameters, the
mechanical load on the n...
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- Article
Authors: Nguyen, Dinh Duc; Vu, Thi Thuy Anh; Vu, Thi Huong; Vu Dinh Quang; Pham, Dinh Nguyen (2019) - In this research, the nonlinear dynamic response of functionally graded carbon nanotube
reinforced composite (FG-CNTRC) sandwich annular spherical shells supported by Pasternak’
foundation is considered by using the analytical approach. Unlike existing works, the structure has three layers: FG-CNTRC layer – homogeneous core – FG-CNTRC layer. Several examples are considered to analyse the behaviour of this sandwich-structured composite. The classical shell theory (CST) is used to derive theoretical formulation delineating nonlinear dynamic response of FG-CNTRC sandwich annular spherical shells. The numerical results explain the effect of material, geometrical parameters, and elastic ...
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- Article
Authors: Nguyen, Duc Cuong (2019) - 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 ...
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- Article
Authors: Nguyen, Xuan Sang; Nguyen, Thi Phuong Anh; Nguyen, Duy Dung; Nguyen, Hoang Cao Huy; Luu, Thi Lan Anh; Nguyen, Huu Tho (2019) - In this study, ZnO doped Mn2+ nanoparticle with hexagonal wurtzite phase was fabricated by a solvothermal method where various contents of Mn ion were in situ doped in ZnO nanostructure. The crystal structure and morphological properties were investigated by X-ray diffractometry, Raman spectroscopy and transmission electron microscopy. The photoluminescence (PL) was measured at room temperature showed red-shift of near-band-to-band emission and the evolution of visible emissions in the doped samples. This work analyzed the PL characteristics of synthesized samples and revealed the role of the dopant Mn2+ on defect states of ZnO.
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- Article
Authors: Nguyen, Van Dat (2019) - In Discretized Kaluza-Klein theory (DKKT) the gauge fields emerge as components of
gravity with a single coupling constant. Therefore, it provides a new approach to fix the
parameters of the Standard Model, and in particular the Weinberg angle. We show that in our
approach using DKKT, the predicted value of Weinberg angle is exactly the one measured in the
electron-positron collider experiment at Q = 91.2 GeV/c. The result is compared with the one
predicted the group theoretic methods.
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- Article
Authors: Nguyen, The Manh; Duong, Hong Quan; Vu, Thi Ngoc Minh; Pham, Vuong-Hung (2019) - Micro/nano urchin-like VO2 particles were synthesized successfully by hydrothermal
method. Vanadium pentoxide (V2O5), oxalic acid (C2H2O4) and sodium dodecyl sulfate (SDS)
surfactant were used as reagents for the synthesis of VO2. In this article, we have reported the
synthesis procedure of VO2 nanorods and micro/nano urchin-like VO2 structure and evaluating the
methylene blue (MB) adsorption properties. Morphology and particle size of VO2 were observed
by FE-SEM. The phase formation of VO2 was studied by XRD. Raman spectroscopy was also
used for characterization of VO2. Micro/nano urchin-like VO2 structure was showed good MB
adsorption properties that have potential applicatio...
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- Article
Authors: Vuong, Van Hiep; Do, Thi Kim Anh; Ngac, An Bang; Hoang, Nam Nhat; Huynh, Dang Chinh (2019) - The saturated magnetization in 20% substituted La0.8R0.2(Fe0.88Si0.12)13 (R = Sm, Tb) magneto-caloric alloys is discussed in this work. The measurements were taken up to 70 kOe (7 Tesla) to detect the saturation of magnetic moments. As reported recently [Mat. Trans. 59(7) (2018) 1068], these compounds show a large variation of magnetic entropies at low field variation (~ 1.5 T), which associate with the large relative cooling efficiency (RCP) of 52 (for Tb-doped) and 102 J/kg (for Sm-doped) even at low effective DH of ~ 15 kOe. We re-detected the effective range of field variation DH and recognized that the effective DH ~ 5 kOe which is much lower than the value of other magneto-calo...
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Authors: Nguyen, Tien Dung (2019) - In this work, we derive analytical expression for the dispersion coefficient of 85Rb atom for a weak probe laser beam induced by a strong coupling laser beams. Our results show possible ways to control dispersion coefficient by frequency detuning and of the coupling lasers. The results show that a Y-configuration appears two transparent window of the dispersion coefficient for the probe laser beam. The depth and width or position of these windows can be altered by changing the intensity or frequency detuning of the coupling laser fields.
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Authors: Bui, Nguyen Quoc Trinh (2019) - A novel concept of NAND memory array has been proposed by using only ferroelectric-gate thin film transistors (FGTs), whose structure is constructed from a sol-gel ITO channel and a sol-gel stacked ferroelectric between Bi3.25La0.75Ti3O12 and PbZr0.52TiO0.48O3 (BLT/PZT) gate insulator. Interestingly, ferroelectric cells with a wide memory window of 3 V and a large on/off current ratio of 6 orders, have been successfully integrated in a NAND memory circuit. To protect data writing or reading from disturbance, ferroelectric transistor cells are directly used, instead of paraelectric transistor cells as usual. As a result, we have verified disturbance-free operation for data reading and ...
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Authors: Hoang, Dung Nam; Nguyen, Kieu Linh (2019) - Given a finite set D of n planar discs whose centers are distributed randomly. We are interested in the expected number of extreme discs of the convex hull of D. We show that the expected number of extreme discs is at most O(log2n) for any distribution. This result can be used to derive expected complexity of convex hull algorithms
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- Article
Authors: Nguyen, Thi Kim Son; Chu, Van Tiep (2019) - The purpose of this article is to show that there exists a smooth real hypersurface germ of D'Angelo infinite type in such that it does not admit any (singular) holomorphic curve that has infinite order contact with at . 2010 Mathematics Subject Classification. Primary 32T25; Secondary 32C25
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- Article
Authors: Nguyen, Quyet Thang; Nguyen, Dinh Nam; Nguyen, Quang Bau (2019) - By using a quantum kinetic equation for electrons, we have studied the Acousto-electric effects in doped semiconductor superlattice (DSSL) under the influence of confined phonon. Considering the case of the electron - acoustic phonon interaction, we have found the expressions of the nonlinear quantum acousto-electric current. From these expression, the acousto-electric current (AEC) depends nonlinearly on temperature, acoustic wave frequency and the characteristic parameters of DSSL (For example: the doped concentration ). Moreover, the expression of the AEC under the influence of confined phonons fairly different from the case of unconfined phonons.The results are numerically calcula...
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- Article
Authors: Nguyen, Thi Lam Quynh; Cao, Thi Vi Ba; Nguyen, Quang Bau (2019) - In this paper, we have used the method of quantum kinetic equation to calculate the analytic expression for Ettingshausen coefficient (EC) under the influence of confined phonon. We considered a quantum well in the presence of constant electric field, magnetic field and electromagnetic wave (EMW) with assumption that electron – confined optical phonon (OP) scattering is essential. The EC obtained depends on many quantities in a complicated way such as temperature, magnetic field, frequency or amplitude of EMW and m - quantum number which specify confined OP. Numerical results for GaAs/GaAsAl quantum well (QW) have displayed clearly the differences in comparison with both cases of bulk...
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Authors: Do, Quoc Tuan (2019) - We will present main results of our recent investigations on the validity of the cosmic no-hair conjecture proposed by Hawking and his colleagues in some conformal-violating Maxwell models, in which a scalar field or its kinetic term is non-trivially coupled to the electromagnetic field. In particular, we will show that the studied models really admit the Bianchi type I metrics, which are homogeneous but anisotropic space time, as their stable cosmological solutions. Hence, these models turn out to be counterexamples to the cosmic no-hair conjecture
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Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513
