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  • Tiểu luận cuối kỳ môn Khoa học quản lý đại cương

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    Quản lý là hoạt động thực tiễn có vai trò đặc biệt quan trọng của con người. Tuy nhiên, hoạt động quản lý không thể đạt hiệu quả cao khi tuân thủ theo những nguyên tắc quản lý. Nguyên tắc là “Điều cơ bản định ra, nhất thiết phải tuân theo trong một loạt việc làm”. Nguyên tắc quản lý là hệ thống những quan điểm quản lý có tính định hướng và những quy định, quy tắc bắt buộc chủ thể quản lý phải tuân thủ trong việc thực hiện chức năng và nhiệm vụ nhằm hoàn thành mục tiêu của tổ chức.
  • Tổng hợp các tài liệu về các tiêu chí đánh giá hoạt động của một doanh nghiệp nhà nước

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    THEO THÔNG TƯ 200/2015/TT-BTC HƯỚNG DẪN MỘT SỐ NỘI DUNG VỀ GIÁM SÁT ĐẦU TƯ VỐN NHÀ NƯỚC VÀO DOANH NGHIỆP, GIÁM SÁT TÀI CHÍNH, ĐÁNH GIÁ HIỆU QUẢ HOẠT ĐỘNG VÀ CÔNG KHAI THÔNG TIN TÀI CHÍNH CỦA DOANH NGHIỆP NHÀ NƯỚC VÀ DOANH NGHIỆP CÓ VỐN NHÀ NƯỚC
  • Anharmonic Correlated Debye Model high-order Expanded Debye-Waller Factors of BCC Crystals - Applica to Metallic Wolfram

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    Anharmonic correlated Debye model is derived for Debye-Waller factors of bcc (body-centered cubic) crystals presented in terms of cumulant expansion up to the fourth order. The many-body effects are taken into account in the present one-dimensional model based on the anharmonic effective potential that includes interactions of absorber and backscatterer atoms with their first shell near neighbors, where Morse potential is assumed to describe the single-pair atomic interaction. Analytical expressions for dispersion relation, correlated Debye frequency and temperature and four first temperature-dependent XAFS (X-ray absorption fine structure) cumulants of bcc crystals have been derived using the many-body perturbation approach. Numerical results for W are found to be in good agreement with experiment.
  • The zeta potential calculation for fluid saturated porous media using linearized and nonlinear solutions of Poisson–Boltzmann equation

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    Theoretical models have been developed to calculate the zeta potential based on the solution of the linearized approximation of the Poisson-Boltzmann equation (PB). The approximation is only valid for the small magnitude of the surface potential. However, the surface potential available in published experimental data normally does not satisfy that condition. Therefore, the complete analytical solution to the PB equation (nonlinear equation) needs to be considered. In this work, the comparison between the linearized and nonlinear solutions has been performed. The results show that the linearized solution always overestimates the absolute value of the electric potential in the electric double layer as well as the zeta potential. For a small magnitude of the surface potential ( mV), the electric potential distribution predicted from the linearized solution is almost the same as that predicted from the nonlinear solution. It is also shown that the zeta potential computed from the linearized PB solution closely matches with that computed from the nonlinear solution for the fluid pH = 5 - 8 and the shear plane distance of 2.4×10−10 m. Therefore, the solution of the linearized PB...
  • The Photon-Drag Effect in Cylindrical Quantum Wire with an Infinite Potential for the Case of Electrons – Acoustic Phonon Scattering

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    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 density of the direct current in the quantum wires from quantum well and bulk semiconductor is due to potential barrier and characteristic parameters of system. These results are for every temperature and are new results.
  • Dynamic Modeling and Control of a Flexible Link Manipulators with Translational and Rotational Joints

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    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. Finite element method and Lagrange approach are used to model and build equations of the motion. PID controller is designed with parameters (Kp, Ki, Kd) which are optimized by using Particle Swarm Optimization algorithm (PSO). Errors of joints variables and elastic displacements at the end-effector point are reduced to warrant initial request. The results of this study play an important role in modeling generalized planar flexible two-link robot and in selecting the suitable structure robot with the same...
  • Characterization of Humidity Sensing of Polymeric Graphene-Quantum-Dots Composites Incorporated with Silver Nanowires

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    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.
  • Facial synthesis and characterization of polypyrrole/zinc oxide (ZnO) nanorode and flower-like shape composites

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    Polypyrrole (PPy) nanocomposites reinforced with zinc oxide (ZnO) nanorod and nano flower are 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-preparedPPy. 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 positionsconfirmed the interfacial interactions between ZnOandPPy matrix.
  • Influence of Reaction Time on Optical Property of ZnS - Mn Nanoparticles Synthesized by a Hydrothermal Method

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    ZnS:Mn (CMn = 5 %mol) nanoparticles have been synthesized by a hydrothermal method from solutions of Zn(CH3COO)2 0.1 M, Na2S2O3 0.1 M and Mn(CH3COO)2 0.01 M at 220oC for different reaction time. The result showed that increasing reaction time from 3 to 30h almost does not change cubic crystalline structure, peak positions attributed to Mn2+ ions at 585 nm in photoluminescence spectra and 392, 430, 463, 468, 492 nm in photoluminescence excitation spectra when monitoring the 585 nm band of ZnS:Mn nanoparticles but only slight increases lattice constant, the average particle size and changing their intensity. As increasing the reaction time from 3 to 10h, intensity of bands attributed to Mn2+ ions also increase, reaches the maximum at 15h and then decreases as increasing reaction time to 30 h. Cause of these phenomena have been investigated and reported.
  • Effect of Halide Anions on Structure of 1-butanol Monolayer/water Interface Probed by Sum-frequency Vibrational Spectroscopy

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    In this report, we use a sum-frequency generation vibrational spectroscopy to measure SFG spectra from 1-Butanol monolayers on pure water and halide saline solution interfaces. These spectra indicate that halide anions have different effects on the structure of 1-Butanol monolayer/water interfaces. The obtained SFG spectra suggest that the I¯ anions mostly disturb the interfacial structure due to their largest surface propensity among those investigated.
  • The Transverse Hall Effect in a Quantum Well with High Infinite Potential in the Influence of Confined Optical Phonons

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    The Transverse Hall effect (THE) has been theoretical studied in a quantum well (QW) with high infinite potential subjected to a crossed dc electric field and a magnetic field (MF) which is oriented perpendicularly to the confinement direction in the present of an intense electromagnetic wave (EMW). The analytical expression of the transverse hall coefficient (THC) which depends not only on the parameters of the system but especially on the quantum number m characterizing confined phonons, is obtained by using the quantum kinetic equation method for confined electrons - confined optical phonons interaction. The analytic expression of THC is numerically evaluated, plotted and discussed for a specific case of the AlAs/GaAs/AlAs QW. Results show the THC depends strong nonlinearly on the EMW amplitude and the MF. All results are compared with that in case of unconfined phonons to see differences.
  • Melting temperature of iron at high pressure - statistical moment method approach

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    The pressure effects on melting temperatures of iron have been studied based on the combination of the modified Lindemann criterion with statistical moment method in quantum statistical mechanics. Numerical calculations have been performed up to pressure 150 GPa. Our results are in good and reasonable agreements with available experimental data. This approach gives us a relatively simple method for qualitatively calculating high-pressure melting temperature. Moreover, it can be used to verify future experimental and theoretical works. This research proposes the potential of the combination of statistical moment method and the modified Lindemann criterion on predicting high-pressure melting of materials.
  • THE LEADING EIKONAL OF THE SCATTERING AMPLITUDE OF PARTICLES IN GRAVITATIONAL FIELD AT HIGH ENERGY USING THE PARTIAL WAVE METHOD

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    The scattering amplitudes for two spineless particles colliding at Planckian center-of-mass energies are considered by the partial wave method in quantum gravity. In the framework of the partial method, a scheme for finding the leading eikonal scattering amplitudes is developed and constructed. The connection between the solutions obtained by partial wave method, quasi-potential and functional approaches is also discussed.
  • Sm3+ DOPED BOROTELLURITE GLASS ABSORPTION, FLUORESCENCE AND OPTICAL PARAMETERS

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    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.
  • MORPHOLOGY, PHASE AND PHOTOLUMINESCENCE OF ZnS MICROSTRUCTURES GROWN BY THERMAL DEPOSITION AT DIFFERENT TEMPERATURE OF SUBSTRATES

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    ZnS microstructures were prepared by thermal evaporating ZnS powder in Ar gas ambient at atmospheric pressure. The influent of temperature at the possitions puted the silica substrates on morphology, phase and photoluminescence of ZnS was investigated. It is clearly seen from the X-ray diffraction pattern that there is only ZnS phase with hexagonal structures at high temperature. Whereas, both ZnS and ZnO appear at lower temperature areas. The morphology of the microstructures change depending on substrate temperatures. The photoluminescence spectrum (PL) at room temperature shows that there is the shift from ultraviolet (UV) emission at high substrate temperature to strong blue emission at lower substrate temperature. The origin of these bands will be discussed in detail.
  • "Calculation of the Ettingshausen Coefficient in a Rectangular Quantum Wire with an Infinite Potential in the Presence of an Electromagnetic Wave (the Electron - Optical Phonon Interaction ) "

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    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 discussed for a specific RQWIP GaAs/GaAsAL. We also compared received EC with those for normal bulk semiconductors and quamtum wells to show the difference. The Ettingshausen effect in a RQWIP in the presence of an EMW is newly developed.
  • Magneto – thermoelectric effects in quantum well in the presence of electromagnetic wave

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    We have studied magneto-thermoelectric effects in quantum well in the presence of electromagnetic wave. The analytic expression for Ettingshausen coefficient (EC) in the Quantum Well with parabolic potential (QWPP) in the presence of Electromagnetic wave (EMW) is calculated by using the quantum kinetic equation for electrons. The dependence of EC on the frequency, the amplitude of EMW, the Quantum Well parameters and the temperature are obtained. The results are numerically calculated, plotted, and discussed for GaAs/GaAsAl Quantum Well to clearly show the dependence of EC on above parameters and the results in this case are compared with the case in the bulk semiconductors. We realize that as the temperature increases, the EC decreases. The results show appearance of the Shubnikov–de Haas (SdH) oscillations when we survey the dependence of EC on the magnetic field.
  • Anharmonic correlated Debye model Debye-Waller factors of metallic Copper compared to experiment and to other theories

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    Debye-Waller factors (DWFs) of metallic Cu (fcc crystal) in X-ray absorption fine structure (XAFS) presented in terms of cumulant expansion have been studied based on the anharmonic correlated Debye model (ACDM). This ACDM is derived from the many-body perturbation approach and the anharmonic effective potential that includes the first shell near neighbor contributions to the vibration between absorber and backscatterer atoms. Analytical expressions of three first XAFS cumulants of Cu have been derived involving more information of phonon-phonon interactions taken from integration over the first Brillouin zone. Morse potential is assumed to describe the single-pair atomic interaction. Numerical results for Cu using the present ACDM show their good agreement with experiment and with those of other theories, as well as their advantages compared to those calculated using the single-pair potential.
  • Photoelectrical characteristics of UV organic thin-film transistor detectors

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    In this paper, a pentacene photo organic thin-film transistor (photoOTFT) was fabricated and characterized. The gate dielectric acted as a sensing layer thanks to it strongly absorbs UV light. Electrical behaviors of photoOTFT were measured under 365 nm UV illumination from the gate electrode side. The current in transistor channel was significantly enhanced by photoelectrons at interface of buffer/gate dielectric. Photosensitivity increased with the light intensity but decreased with the applied gate voltage. Meanwhile the photoresponsivity decreased with the light intensity and increased with the applied gate voltage. The transistor responses well with the pulse of light with many test cycles of light-on and light-off. The best photosensitivity, photoresponsivity, rising time and falling time parameters of the device were found to be about 104, 0.12 A/W, and 0.2 s, respectively. The obtained photoelectrical results suggest that the photoOTFT can be a good candidate for practical uses in low-cost UV optoelectronics.
  • Crystal Structure and Magnetic Properties for Bi1-xEuxFeO3 Compounds

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    BiFeO3 (BFO) is a promising multiferroic material due to its high ferroelectric and antiferromagnetic ordering temperatures. Substituting partially Bi by Rare-Earth (RE) seem to be one way to enhance magnetization of BFO. In this study, crystal structure and magnetic properties for Bi1-xEuxFeO3 compounds are presented. When the Eu content was below 5% (x < 0.05), no significant improvement in magnetic properties was observed. However, when x < 0.20, ferromagnetism was induced. More particularly, at x = 0.20, the compounds experienced a drastically structural transition that governs also their optical properties
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