Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 444
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Authors: Nguyen, Van Nghia; Nguyen, Duy Hung (2018) - We present an investigation of the morphology, structure, composition and optical properties of ZnS:Mn2+ microbelts grown by the thermal evaporation method using ZnS powder and MnCl2.4H2O powder as precursor materials. The SEM images of the products show that ZnS:Mn2+ microbelts are bigger and shorter than ZnS microbelts. EDS reveals that the composition of the microbelts include Zn, S, O, Mn and Cl elements. The atom rate of oxygen composition of the doped microbelts seem to be slightly lower than undoped ones. XRD pattern of the prepared microbelts shows that ZnO coexists with ZnS on the undoped microbelts. However, at the Mn-doped microbelts, the component phase of ZnO is disappear...
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- Article
Authors: Nguyen, Phuc Duong (2018) - Samples with the compositions Y2.9Ca0.1Fe4.9Sn0.1O12 and Y3Fe4.9Sn0.1O12 were prepared by using a sol-gel technique. The influence of the substituted non-magnetic cations with different valences in the structural and magnetic properties was studied. X-ray diffraction and field-emission electron scanning microscope techniques were used to study the crystal structure and morphology. Magnetization curves in fields up to 10 kOe and in temperature range from 80 K to 570 K were measured by means of a vibrating sample magnetometer. Saturation magnetization as a function of temperature of the two samples was analyzed based on the molecular-field theory from that models for site occupancy and ...
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- Article
Authors: Phan, Van Do (2018) - Borotellurite glasses doped with Sm3+ ions were prepared by a melt–quenching technique. The studies on optical characterization of Sm3+ ions have been carried out through absorption, emission and decay spectra. Judd-Ofelt (JO) intensity analysis has been presented and JO parameters were calculated for Sm3+ ions in borotellurite glasses. Radiative properties such as transition probabilities, branching ratios, radiative lifetime of 4G5/2 level and quantum efficiency were estimated by using JO parameters.
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Authors: Trinh, Thi Loan; Nguyen, Ngoc Long (2018) - Zinc aluminate - alumina (ZnAl2O4/Al2O3) systems doped with Cr3+ different concentrations were synthesized by sol-gel method. The samples were characterized by X-ray diffraction (XRD), photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The results showed that Cr3+ dopant concentration had a significant effect on the lattice constants of ZnAl2O4/Al2O3 composite and their luminescence characteristics.
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- Article
Authors: Nguyen, Xuan Sang; Luu, Thi Lan Anh; Tran, Thanh Thai; Phan, Trung Nghia; Vo, Thach Son (2018) - Polypyrrole (PPy) nanocomposites reinforced with zinc oxide (ZnO) nanorod and nano flower were fabricated by chemical oxidative polymerization method using an ammonium per-sulphate (APS, (NH4)2S2O8) as an oxidizing agent. The polymer nanocomposite were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The results were compared with pure as-prepared PPy. The SEM images of the nanocomposites show homogeneous dispersion characteristics and different morphologies of ZnO structures such as rod and flower-like shapes. In the FTIR spectra, composite samples showed characteristic peaks of PPy shifted to higher positions co...
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- Article
Authors: Duong, Xuan Bien; Chu, Anh My; Phan, Bui Khoi (2018) - Flexible link manipulators are widely used in many areas such the space technology, medical, defense and automation industries. They are more realistic than their rigid counterparts in many practical conditions. Most of the investigations have been confined to manipulators with only rotational joint. Combining such systems with translational joints enables these manipulators more flexibility and more applications. In this paper, a nonlinear dynamic modeling and control of flexible link manipulator with rigid translational and rotational joints is presented. This model TR (Translational-Rotational) is developed based on single flexible link manipulator with only rotational joint. Finit...
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Authors: Nguyen, Thi Thanh Ha; Kankham, Keopanya; Le, Van Vinh (2018) - In this paper the structural and dynamical characteristics in alumina- silicate Al2O3–2SiO2 (AS2) liquid are investigated by molecular simulation method. Structural properties are clarified through the pair radial distribution function, distribution of TOn (T= Si, Al) coordination units and distribution of partial bond angle in TOn. Furthermore the change in diffusion mechanism between low and high pressure is revealed by transition of the structural units TOx → TOx±1. At the low-pressure configuration of the liquid AS2 exhibits the dynamics heterogeneity (DH). The original of dynamic heterogeneity is identified and liquid AS2 consists of separate mobile and immobile regions.
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Authors: Bui, Thi Hong; Vu, Anh Hung; Nguyen, Quang Mien; Bui, Van Loat (2018) - The samples of LiF: Mg,Cu,P powder (xeri: GR-200) were irradiated by the gamma radiation resource with varied exposed dose. The glow curves of thermoluminescence (TL) material were observed with the defferent heating rates. The influence of heating rate on the thermoluminescence property of LiF: Mg,Cu,P was analyzed. The results showed that as the heating rate increases, the peak intensity at the maximum decreases and shifts to higher temperature. The thermoluminesecnce sensitivity of the material also changes and has the optimal value at 6oC/s. This value is also adaptable for measurement of natural environmental and archaeologicaldose.
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- Article
Authors: Luong, Duy Thanh; Rudolf, Sprik (2018) - The streaming potential coefficient of liquid-rock systems is theoretically a very complicated function depending on many parameters including temperature, fluid concentration, fluid pH, as well as rock parameters such as porosity, grain size, pore size, and formation factor etc. At a given porous media, the most influencing parameter is the fluid conductivity or electrolyte concentration. Therefore, it is useful to have an empirical relation between the streaming potential coefficient and electrolyte concentration. In this work, the measurements of the streaming potential for four unconsolidated samples (sandpacks) saturated with four monovalent electrolytes at six different electrol...
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- Article
Authors: Nguyen, Van Nghia; Nguyen, Duy Hung (2018) - We present an investigation of the morphology, structure, composition and optical properties of ZnS:Mn2+ microbelts grown by the thermal evaporation method using ZnS powder and MnCl2.4H2O powder as precursor materials. The SEM images of the products show that ZnS:Mn2+ microbelts are bigger and shorter than ZnS microbelts. EDS reveals that the composition of the microbelts include Zn, S, O, Mn and Cl elements. The atom rate of oxygen composition of the doped microbelts seem to be slightly lower than undoped ones. XRD pattern of the prepared microbelts shows that ZnO coexists with ZnS on the undoped microbelts. However, at the Mn-doped microbelts, the component phase of ZnO is disappear...
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- Article
Authors: Hoang, Van Ngoc; Nguyen, Vu Nhan; Dinh, Quoc Vuong (2017) - The photon - drag effect with electrons – acoustic phonon scattering in cylindrical quantum wire with an infinite potential is studied. With the appearance of the linearly polarized electromagnetic wave, the laser radiation field and the dc electric field, analytic expressions for the density of the direct current are calculated by the quantum kinetic equation. The dependence of the direct current density on the frequency of the laser radiation field, the frequency of the linearly polarized electromagnetic wave and the temperature of the system is obtained. The analytic expressions are numerically evaluated and plotted for a specific quantum wire, GaAs/AlGaAs. The difference of the de...
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- Article
Authors: Hoang, Ha; Bui, Nguyen Quoc Trinh (2017) - 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 starte...
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- Article
Authors: Cao, Thi Vi Ba; Tran, Hai Hung; Doan, Minh Quang; Nguyen, Quang Bau (2017) - The Ettingshausen coefficient (EC) in a Rectangular quantum wire with an infinite potential (RQWIP)in the presence of an Electromagnetic wave (EMW) is calculated by using a quantum kinetic equation for electrons. Considering the case of the electron - optical phonon interaction, we have found the expressions of the kinetic tensors . From the kinetic tensors, we have also obtained the analytical expression of the EC in the RQWIP in the presence of EMW as function of the frequency and the intensity of the EMW, of the temperature of system, of the magnetic field and of the characteristic parameters of RQWIP. The theoretical results for the EC are numerically evaluated, plotted and disc...
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Authors: Le, Thi Thu Phuong; Tran, Thi My Duyen; Vo, Thanh Lam; Bui, Dinh Hoi (2017) - In this work, utilising the linear response theory we calculate the magneto conductivity (MC) in graphene monolayers, subjected to a static perpendicular magnetic field. The interaction of Dirac fermions with optical phonon via deformation potential is taken into account at high temperature. The dependence of the MC on the magnetic field shows resonant peaks that describe transitions of electrons between Landau levels via the resonant scattering with optical phonons. The effect of temperature on the MC is also obtained and discussed.
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Authors: Sai, Cong Doanh; Pham, Nguyen Hai; Ngac, An Bang (2017) - Cuprous oxide (Cu2O) and Au-Cu2O core-shell nanoparticles were successfully
synthesized using the chemical reduction method. The morphology of the synthesized pure
Cu2Oparticles can be controlled by varying the amount of reducing agent NH2OH.HCl. Due to
their similar crystal structure and relatively small lattice mismatch Cu2O particles are nucleated
and locally undergo an epitaxial growth on the surface of the multi-faceted Au seed resulting in a
stellated icosahedra Au-Cu2O core-shell particle. The extinction spectrum of Cu
2O particles offew
hundred-nm in size is dominated by light scattering, while that of the stellated icosahedra Au-Cu2O core-shell part...
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- Article
Authors: Le, Duc Nhien; Le, Huy Tien (2017) - In 2007, N. H. Du and L. H. Tien \cite{Du} shown that the exponential stability of the linear equation on time scales implies the exponential stability of the suitable small enough Lipchitz perturbed equation. In this paper, we shall prove that if the perturbation is arbitrary small order $1$ then the above argument is not true which is called Perron effect.
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Authors: Nguyen, Thi Thu Hang; Pham, Thanh Luan; Do, Duc Thanh; Le, Huy Minh (2017) - The analytic signals of the magnetic tensor gradient within two-and three-dimensional space can be applied as a useful tool to estimate the depth and position sources because its value characteristics only depend on location but magnetization direction of the sources of the magnetic anomaly [7]. In this paper, we present results of the study for application of the combination of derivatives of directional analytic signals of the magnetic tensor gradient to determine the edges of the sources through the new function Edge-detector (|ED|). Algorithms and programs written in the Matlab language have been used for test calculation on 3D models in correlative comparison with the method usin...
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Authors: Somsavath, Leuangtakoun; Bui, Van Loat; Vu, Thi Kim Duyen; Khong, Nam Khang (2017) - We have determined activity concentrations in 33 soil samples collected from Bolikhamxay Province, Laos. The activity concentrations of the natural radionuclides 226Ra,232Th and 40K in soil samples were measured by a gamma spectrometer with a HPGe detector. The average activity concentrations of the natural radionuclides 226Ra, 232Th and 40K are 43.8 ± 5.6, 57.0 ± 7.3 and 426.4 ± 23.1 Bq.kg-1, respectively. The average activity concentrations of 226Ra and 232Th in this work are higher than those of the world average values. Meanwhile, the activity concentration of 40 K is almost the same of the world average value. The estimated average outdoor annual effective dose (E) and radium eq...
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Authors: Nguyen, Van Nghia (2017) - In this paper, we present about influent of temperature at the possitions where we puted the silica substrates on morphology, phase and photoluminescence of ZnS microstructures by thermal evaporation of ZnS powder in Ar gas ambient at atmospheric pressure. From X-ray diffraction pattern (XRD), the prepared microstructures have wurtzite (hexagonal) structures for ZnS phase and appear ZnO phase at lower temperature areas. The morphology of the microstructures change depending on substrate temperatures. The photoluminescence spectrum (PL) at room temperature shows that the shift from ultraviolet (UV) emission at high substrate temperature to strong blue emission at lower substrate temper...
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Authors: Luong, Duy Thanh (2017) - The measurements of the zeta potential of five consolidated samples including natural and artificial ceramic rocks saturated with 5.0×10-3 M NaCl electrolyte at different temperatures have been reported. The zeta potential obtained in this work is always negative and increases in magnitude with increasing temperature for all samples (an average increase of the zeta potential of 0.4 mV/ oC in magnitude). The experimental results are in good agreement with previously published data. The experimental data is then explained by a theoretical model. It is shown that the model is able to reproduce the main trend of the experimental data from our work and from published articles.
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Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 444
