 Article
Authors: Nguyen, Thi Thanh Ha; Tran, Thuy Duong; Nguyen, Hoai Anh (2020)  Molecular dynamics simulation of sodiumsilicate has been carried out to investigate the microstructural transformation and diffusion mechanism. The microstructure of sodium silicate is studied by the pair radial distribution function, distribution of SiOx (x=4,5,6), OSiy (y=2,3) basic unit, bond angle distribution. The simulation results show that the structure of sodium silicate occurs the transformation from a tetrahedral structure to an octahedral structure under pressure. The additional networkmodifying cation oxide breaking up this network by the generation of nonbridging O atoms and it has a slight effect on the topology of SiOx and OSiy units. Moreover, the diffusion of netw...

 Article
Authors: Giap, Thi Thuy Trang; Pham, Huu Kien (2020)  In this work, we use molecular dynamic (MD) simulation to study the structure transition and crystallization of amorphous silica (SiO2) under compression. The structural evolution of amorphous SiO2 is explained through radial distribution function, coordination number distribution, bond angle distribution and visualization. Simulation result shown that there is a structural transformation from tetrahedral to octahedral network through SiO5 units. In the 515 GPa pressure range, structural transformation occurs powerfully and there are three structural phases corresponding to SiO4, SiO5, and SiO6 ones. At 15 GPa, octahedralnetwork (SiO6) is dominant. It is the first time we showed ...

 Article
Authors: Pham, Dinh Nguyen; Vu, QuangViet; George, Papazafeiropoulos; Hoang, Thị Thiem; Pham, Minh Vuong; Nguyen, Dinh Duc (2020)  This paper proposes an optimization procedure for maximization of the biaxial buckling load of laminated composite plates using the gradientbased interiorpoint optimization algorithm. The fiber orientation angle and the thickness of each lamina are considered as continuous design variables of the problem. The effect of the number of layers, fiber orientation angles, thickness and length to thickness ratios on the buckling load of the laminated composite plates under biaxial compression is investigated. The effectiveness of the optimization procedure in this study is compared with previous works.

 Article
Authors: Phan, Van Do (2020)  Borotellurite glasses were prepared by melt quenching technique. Amorphous nature of samples was confirmed through Xray diffraction (XRD) patterns. Effect of B2O3 content on the structure of glass network was studied through Fouriertransform infrared spectroscopy (FTIR) spectra. Optical band gap and Urbach energy were found from analysis of optical absorption spectra. Thermal studies were carried out by using Differential thermal analyzer (DTA) measurements.

 Article
Authors: Tran, Thi Ha; Nguyen, Thi Huyen Trang; Bach, Thanh Cong; Nguyen, Thi Dieu Thu; Nguyen, Thanh Binh; Nguyen, Viet Tuyen; Pham, Nguyen Hai (2020)  We report a facile process to fabricate cuprous thin films by thermal oxidation of copper substrates. Structure and phase identification were studied by Xray diffraction measurement and Raman spectroscopy. Scanning electron microscopy was utilized to study surface morphology of the asfabricated thin films and optical properties of the samples were investigated by diffused reflectance spectroscopy. The study shows that cuprous thin films could be obtained by controlling annealing temperature in the region of 200300 oC.

 Article
Authors: Dang, Minh Triet; Truong, Quoc Tuan; Tran, Van Thien (2020)  Colloidal gels are spacespanning networks that form solids at dilute particle volume fractions. The kinetic process of gelation is central to understand the flow of complex fluids. Here, we report a simulation study of colloidal gelation of anisotropic colloids with attractive LennardJones potential. These forces quasimodel the critical Casimir effect far from the critical solvent fluctuations acting on colloidal patches. By tuning the depths of the patchtopatch particle interactions and the selected colloidal patches, we dynamically arrest the colloids to form gels. We find that thermal density fluctuation is the key factor to activate colloidal cluster space spanning: the balan...

 Article
Authors: Dao, QuangDuy (2020)  We demonstrate an efficient bulk heterojunction (BHJ) organic solar cell (OSCs) utilizing a soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25octahexylphthalocyanine (C6PcH2), and a fullerene derivative, 1(3methoxycarbonyl)propyl11phenyl(6,6)C71 and roles of processing additive solvent on improvement of the BHJ OSCs. By adding processing additive solvent, filling factor and shortcircuit current density are improved to 0.57 and 8.6 mA/cm2, respectively. As a result, the power conversion efficiency of 3.6% is achieved. Otherwise, the effects of processing additive solvent are demonstrated by taking the absorption and photoluminescence spectra of C6PcH2 and composite thin ...

 Article
Authors: Ngo, Thi Thu Trang; Nguyen, Duc Nhan; Bui, Trung Hieu (2020)  In directdetection optical OFDM system, the nonlinear impairment is the key factor that limits the system performance. The backpropagation techniques in digital and optical domains have been proposed to compensate the nonlinear effects, however they can be unsuitable for longrange passive optical networks (LRPONs) due to their implementation at receiver. In this study, we propose an optical back propagation (OBP) approach for compensation of the nonlinear and dispersion distortions in directdetection optical OFDM system. The proposed OBP using splitstep Fourier method is implemented at transmitter that is suitable for highrate OFDMbased LRPONs applications. In this OBP, the f...

 Article
Authors: Nguyen, Trong Nghia (2020)  C2H5OH has been using as an alternative fuel for decades; HO2 also plays a pivotal role in the combustion. The kinetics and mechanism for the reaction between C2H5OH and HO2 radical have been investigated using the molecular parameters for the reactants, transition states and products predicted at the CCSD(T)//B3LYP/6311++G(3df,2p) level of theory. There are ten pair products have been found including C2H5O + H2O2 (PR1), CH3CHOH + H2O2 (PR2), CH2CH2OH + H2O2 (PR3), CH3CH2OOOH + H (PR4), C2H5 + HOOOH (PR5), CH3CH2OOH + OH (PR6), CH3CH(OH)OOH + H (PR7), HOCH2CH2OH + H (PR8), HOOCH3 + CH2OH (PR9), and CH3 + HOOCH2OH (PR10) in which the second and third ones are the major channels. The r...

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Authors: Ho, Thi Anh; Nguyen, Ngoc Huyen; Pham, Duc Thang (2020)  Nd0.6Sr0.4MnO3 sample was fabricated by a solidstate reaction method and its magnetic, magnetocaloric properties were investigated. The Curie temperature, TC, at which a ferromagneticparamagnetic transition occurred was found to be of about 270 K. An analysis using the Banejee’s criterion of the experiment results for magnetization as a function of temperature and magnetic field and the universal curves of the normalized entropy change versus reduced temperature indicated that the sample undergo the secondorder magnetic phase transition. Furthermore, the maximum magnetic entropy change that occurred near TC, measured at a magnetic field span of 50 kOe was found to be of about 6.0 J...

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Authors: Nguyen, Minh Tan; Chen, HuaMing; Giap, Binh Duong; Hoang, Le Quang Nhat (2020)  Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) techniques are combined to provide the spectrum efficiency and high data rate improvement that it was required for 4G, 5G wireless systems. Discrete Wavelet Transform (DWT) is presented as an alternative for Fast Fourier Transform (FFT) since there is no necessity for Cyclic Prefix (CP) due to the overlapping properties of DWT. By a simple replacement of the FFT with DWT in MIMOOFDM system, an improvement of performance has been detected which leads to a new system scenario MIMOOFDM based on DWT. In this thesis, the two systems are simulated with particular parameters and the performance of B...

 Article
Authors: Nguyen, Tien Cuong (2020)  In this paper, I present firstprinciple calculations which are performed by using combination of DFT and NEGF methods to investigate the adsorption of CO2 and NH3 molecules on straight and Ushaped GNRs junctions. The density of state, molecular orbital, adsorption energy, transmission spectrum, and currentvoltage characteristics were analyzed. It is found that the adsorption of CO2 and NH3 on straight GNRs at the dangling bond edges exhibit chemical interaction behavior with high adsorption energy. Besides, for Ushaped ZGRNs without adsorption, the states around Fermi level are quasibound states localized at the zigzag edges. The electrons at these localized states are almost con...

 Article
Authors: Phung, Thi Viet Bac; Pham, Trong Lam; Dinh, Van An (2020)  The adsorption mechanism of 2butanone (ethyl methyl ketone) on the surface of graphene is investigated by using Density Functionals Theory (DFT). A 2butanone molecule is chosen as a selected example of main volatile organic compounds (VOCs) in exhaled breath. To describe the absorption of 2butanone and graphene substrate, we have performed DFT simulations including van de Waals (vdW) interactions implemented in the Vienna Abinitio Simulation Package (VASP). The global minimum energy configurations and binding energies for a 2butanone molecule adsorbed on graphene are determined by using Computational DFTbased Nanoscope tool for imaging the binding possibility of the adsorbed mol...

 Article
Authors: Pham, Trong Lam; Ta, Thi Luong; Vo, Van On; Dinh, Van An (2020)  In this work, we investigated the adsorption mechanism of acetone and toluene on the surface of silicene by the quantum simulation method. The images of the potential energy surfaces for different positions of the adsorbate on the silicene surface were explored by Computational DFTbased Nanoscope tool for determination of the most stable configurations and diffusion possibilities. The charge transfer in order of 0.2 – 0.3 electrons and the tunneling gap opening of 18 – 23 meV due to acetone and toluene, respectively, suggest that silicene is considerably sensitive with these VOCs and can be used as the material in the fabrication of reusable VOC sensors.

 Article
Authors: Nghiem, Thi Minh Hoa; Dang, The Hung; Luong, Minh Tuan; Duong, Xuan Nui; Nguyen, Duc Trung Kien (2020)  In an arbitrary system subjected to a quench or an external field that varies the system parameters, the degrees of freedom increases double in comparison to that of an isolated system. In this study, we consider the quantum impurity system subjected to a quench, and measure the corresponding timeevolution of the spectral function, which is originated from the timeresolved photoemission spectroscopy. Due to the large number of degrees of freedom, the expression of the timedependent spectral function is twice much more complicated than that of the timeindependent spectral function, and therefore the calculation is extremely time consuming. In this paper, we estimate the scale of ti...

 Article
Authors: Nguyen, Thi Thanh Tan; Le, Hong Lam; Nguyen, Ha Nam (2020)  The problem of optical character and handwriting recognition has been interested by researchers in long time ago. It has obtained great results in theory as well as practical applications. However, the accuracy of identification is still limited, especially in the case of lowquality input images. In this article, we propose an efficient method to recognize information fields for identification in ID card using Convolutional Neural Network (CNN) and Long ShortTerm Memory networks (LSTM). The proposed method was trained in a large, various quality dataset including over three thousands ID card image samples. The implementation achieved better results compare to previous studies with t...

 Article
Authors: Le, Nhu Thuc; Dao, Thi Le Thuy (2020)  The production of scalar unparticle (spin  0) in the photon  electron ( e ) collider is
calculated in all s, t, and uchannels in detail as well as interference between channels together.
By searching for missing energy distributions as well as evaluating dependence of differential
cross section (DCS) on the scattering angle ( ) and cross section (CS) on the center of mass energy
( s ) , we hope that the unparticles production in high energy collider might be detected in future.

 Article
Authors: Tran, Thi Ha; Nguyen, Manh Hong; Mai, Hong Hanh; Pham, Van Thanh; Sai, Cong Doanh; Nguyen, Thanh Binh; Pham, Nguyen Hai; Nguyen, Trong Tam; Ho, Khac Hieu; Nguyen, Viet Tuyen (2020)  Thanks to unique Raman spectra of chemical substances, a growing number of
applications in environmental and biomedical fields based on Raman scattering has been
developed. However, the low probability of Raman scattering hindered its potential development
and thus, many different techniques were developed to enhance Raman signal. A key step of
surfaceenhanced Raman scattering technique is to prepare active SERS substrate from noble
metals. The main enhancement mechanism is electromagnetic enhancement resulted from surface
plasmon resonance. The disadvantages of nanoparticles based SERS substrates include high
randomness due to self  assembly process of nanoparticles. Recentl...

 Article
Authors: Vu, Minh Anh; Nguyen, Dinh Duc (2019)  The nonlinear dynamic response and vibration of the porous functionally graded cylindrical panel (PFGCP) subjected to the thermal load, mechanical load and resting on elastic foundations are determined by an analytical approach as the Reddy’s thirdorder shear deformation theory, Ahry’s function… The results for dynamic response of PFGCP present the effect of geometrical ratio, elastic foundations: Winkler foundation and Paskternak foundation, loads: mechanical load and thermal load, the material properties and distribution type of porous. The results are shown as numerical results, figures and are determined by using Galerkin methods and Fourthorder RungeKutta method.

 Article
Authors: Nguyen, Thu Ha (2019)  This paper is concerned with the robust stability for implicit dynamic equations on time scales, which is a general form of differential algebraic equations and implicit difference equations. We show the reservation of exponential stability of these equations under small Lipschitz perturbations
