Mathematics and Physics : [513]

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Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513
  • Crystallization Pathway for Crystallization of FeB Nanoparticles.pdf.jpg
  • Article


  • 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...

  • Distribution of Sodium and Diffusion Mechanism in Sodium Silicate Liquid.pdf.jpg
  • 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...

  • Influence of Confined Phonons on the Hall Coefficient in a Cylindrycal Quantum wire with an infinite potential (for electron – confined optical phonon scattering).pdf.jpg
  • 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...

  • Magneto – thermoelectric Effects in Compositional Superlattice in the Presence of Electromagnetic Wave.pdf.jpg
  • 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...

  • Electrochemical properties of Fe2O3 AB based composite electrodes in alkaline solution.pdf.jpg
  • 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...

  • Nonlinear Dynamic Analysis for Rectangular FGM Plates with Variable Thickness Subjected to Mechanical Load.pdf.jpg
  • 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.

  • Nonlinear Dynamic Response and Vibration of 2D Penta-graphene Composite Plates Resting on Elastic Foundation in Thermal Environments.pdf.jpg
  • 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...

  • Nonlinear Dynamic Response of Nano-composite Sandwich Annular Spherical Shells.pdf.jpg
  • 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 ...

  • Optical Simulation of Planar CH3NH3PbI3 Perovskite Solar Cells.pdf.jpg
  • 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 ...

  • Photoluminescence Emission and Raman Vibration Properties of Asymmetric Nanoparticle ZnO Doped Mn2+ Fabricated by a Solvothermal Method.pdf.jpg
  • 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.

  • Prediction of Weinberg Angle in Discretized Kaluza-Klein Theory.pdf.jpg
  • 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.

  • Synthesis of Micronano Urchin-like VO2 Particles and Its Decolorization of Methylene Blue.pdf.jpg
  • 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...

  • 4353-97-8863-1-10-20190621.pdf.jpg
  • 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...

  • 4352-97-8862-1-10-20190621.pdf.jpg
  • Article


  • 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.

  • 4351-97-8861-1-10-20190621.pdf.jpg
  • Article


  • 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 ...

  • 4347-97-8860-1-10-20190621.pdf.jpg
  • Article


  • 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

  • 4345-97-8859-1-10-20190621.pdf.jpg
  • 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

  • 4339-97-8858-1-10-20190621.pdf.jpg
  • 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...

  • 4338-97-8857-1-10-20190621.pdf.jpg
  • 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...

  • 4337-97-8856-1-10-20190621.pdf.jpg
  • Article


  • 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

Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513

Mathematics and Physics : [513]

Follow this collection to receive daily e-mail notification of new additions
Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513
  • Crystallization Pathway for Crystallization of FeB Nanoparticles.pdf.jpg
  • Article


  • 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...

  • Distribution of Sodium and Diffusion Mechanism in Sodium Silicate Liquid.pdf.jpg
  • 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...

  • Influence of Confined Phonons on the Hall Coefficient in a Cylindrycal Quantum wire with an infinite potential (for electron – confined optical phonon scattering).pdf.jpg
  • 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...

  • Magneto – thermoelectric Effects in Compositional Superlattice in the Presence of Electromagnetic Wave.pdf.jpg
  • 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...

  • Electrochemical properties of Fe2O3 AB based composite electrodes in alkaline solution.pdf.jpg
  • 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...

  • Nonlinear Dynamic Analysis for Rectangular FGM Plates with Variable Thickness Subjected to Mechanical Load.pdf.jpg
  • 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.

  • Nonlinear Dynamic Response and Vibration of 2D Penta-graphene Composite Plates Resting on Elastic Foundation in Thermal Environments.pdf.jpg
  • 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...

  • Nonlinear Dynamic Response of Nano-composite Sandwich Annular Spherical Shells.pdf.jpg
  • 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 ...

  • Optical Simulation of Planar CH3NH3PbI3 Perovskite Solar Cells.pdf.jpg
  • 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 ...

  • Photoluminescence Emission and Raman Vibration Properties of Asymmetric Nanoparticle ZnO Doped Mn2+ Fabricated by a Solvothermal Method.pdf.jpg
  • 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.

  • Prediction of Weinberg Angle in Discretized Kaluza-Klein Theory.pdf.jpg
  • 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.

  • Synthesis of Micronano Urchin-like VO2 Particles and Its Decolorization of Methylene Blue.pdf.jpg
  • 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...

  • 4353-97-8863-1-10-20190621.pdf.jpg
  • 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...

  • 4352-97-8862-1-10-20190621.pdf.jpg
  • Article


  • 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.

  • 4351-97-8861-1-10-20190621.pdf.jpg
  • Article


  • 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 ...

  • 4347-97-8860-1-10-20190621.pdf.jpg
  • Article


  • 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

  • 4345-97-8859-1-10-20190621.pdf.jpg
  • 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

  • 4339-97-8858-1-10-20190621.pdf.jpg
  • 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...

  • 4338-97-8857-1-10-20190621.pdf.jpg
  • 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...

  • 4337-97-8856-1-10-20190621.pdf.jpg
  • Article


  • 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

Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 513