57 số bộ dữ liệu tìm thấy

Định dạng: Word

Kết quả lọc
  • Intrinsic Efficiency Calibration for Uranium Isotopic Analysis in Soil Samples

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    In this work, we present the results of using the non-destructive gamma spectroscopic method for uranium isotopic analysis and checking the status of radioactive equilibrium between 238U and 226Ra in soil samples. In order to analyze uranium isotopes and check the status of equilibrium between 238U and 226Ra the activity ratios 235U/238U and 238U/226Ra were measured. The these activity ratios were determined based on the characteristic gamma rays and using intrinsic (relative) detection efficiency calibration method. The results obtained shows that this suggested analytical method can be used to determine the uranium concentration in the case of the samples having arbitrary shapes and it does not require the use of any reference materials.
  • The Photon - Drag Effect in Rectangular Quantum Wire with An Infinite Potential

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    The photon - drag effect with optical phonon-electron scattering in rectangular quantum wire with an infinite potential is studied. Based on the quantum kinetic equation for electrons under the action of a linearly polarized electromagnetic wave, a dc electric field and an intense laser field, analytic expressions for the density of the direct current for the case of electron – optical phonon scattering are calculated. The dependence of the direct current density on the frequency  of the laser radiation field, the frequency  of the linearly polarized electromagnetic wave, the size of the wire is obtained. The analytic expressions are numerically evaluated and plotted for a specific quantum wire, GaAs/AlGaAs. All these results of quantum wire are compared with bulk semiconductors and superlattices to show the differences.
  • On a five-dimensional scenario of massive gravity

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    A study on a five-dimensional scenario of a ghost-free nonlinear massive gravity proposed by de Rham, Gabadadze, and Tolley (dRGT) will be presented in this article. In particular, we will show how to construct a five-dimensional massive graviton term using the Cayley-Hamilton theorem. Then some cosmological solutions such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini-(A)dS spacetimes will be solved for the five-dimensional dRGT theory thanks to the constant-like behavior of massive graviton terms under an assumption that the reference metric is compatible with the physical one.
  • Mathematical Model in Studying the Stability of Dynamic Systems

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    In this paper, the author investigated the phenomenon of flutter, which may be the cause of instability of construction structure when it is affected by aerodynamics. By analyzing the effect of aerodynamic on the structure via mathematical analysis, the author has established a mathematical model to study the stability of the structure in the aerodynamic flux that moves supersonically.
  • A Simple, One-step, Seedless Hydrothermal Growth of ZnO Nanorods on Printed Circuit Board Substrate

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    High quality, high density, and well-aligned zinc oxide (ZnO) nanorods have been synthesized on cost-effective printed circuit board (PCB) substrates via a simple, seedless, one-step, low-temperature hydrothermal method based galvanic cell structure. It was found that the outer diameters of the ZnO nanorods range from 50 nm to 400 nm. The as-grown ZnO nanorods prefer to grow along the c axis. The morphologies of the ZnO nanorods were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD). The crystallinity properties were characterized by Raman spectroscopy and photoluminescence (PL) spectroscopy.
  • Enhancements of critical temperature inBi-Pb-Sr-Ca-Cu-O superconductors

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    Trong nghiên cứu này, ảnh hưởng của nhiệt độ nung thiêu kết và hiệu ứng thay thế Na lên nhiệt độ tới hạn(Tc,0) của hệ siêu dẫn Bi-Pb-Sr-Ca-Cu-O được khảo sát. Mẫu khối Bi1.6Pb0.4Sr2Ca2-xNaxCu3O10+ với hàm lượng x = 0.00 và 0.05 (BPSCCO) được chế tạo bằng phương pháp phản ứng pha rắn tại các nhiệt độ nung thiêu kết khác nhau là 840 và 850 oC. Để nghiên cứu sự cải thiện tính chất cấu trúc và tính siêu dẫn của mẫu BPSCCO, phép đo nhiễu xạ kế tia X (XRD), hiển vi điện tử quét (SEM) và đo điện trở phụ thuộc vào nhiệt độ được khảo sát. Kết quả cho thấy sự tồn tại cả hai pha Tc cao (Bi-2223) và Tc thấp (Bi-2212)ở toàn bộ các mẫu. So sánh định lượng, tỉ phần của pha Bi-2223 tăng từ 71.4 lên 75.7%, và kích thước hạt Bi-2223 tăng từ 4.5 lên 9.8 mkhi điều kiện chế tạo mẫu thay đổi. Đồng thời, kết quả phân tích sự thay đổi Tc,0 theo tỉ số điện trở dư (RRR)cũng cho thấy liên kết giữa các hạt Bi-2223 được tăng cường. Những thay đổi ưu thế này được xem là nguyên nhân tăng Tc,0 của mẫu siêu dẫn BPSCCO.
  • BLUE, GREEN AND YELLOW EMISSIONS AT THE SAME TIME FROM Mn-DOPED ZnS MICROBELTS

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    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 is presented. 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 disappeared. Photoluminescence spectra of undoped ZnS microbelts reveal a strong broad emission band at visible wavelength region and a weak ultraviolet band. Interestingly, when Mn2+ is doped into the microbelts, the visible emission band is separated into blue, green, and yellow bands peaking at around 442, 520 nm, and 572 nm, respectively. The effects of Mn2+ ions on the emission bands is discussed in detail.
  • Cyclic inequality forms with power 1/2,1/3

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    The purpose of this paper is to establish inequalities between two terms ...
  • Study of heating rate effect on thermoluminescence glow curves of LiF - Mg, Cu, P

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    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.
  • The temperature dependence of the zeta potential in porous media

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    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.
  • Electrical Properties OfNb-Doped TiO2 Thin Films Deposited By Co-sputtering Process

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    Nb-dopedTiO_2 thin films were fabricated by co-sputtering of TiO2 doped 6%wt by Nb2O5and Nb targets. The anatase polycrystalline thin films were obtained by post-annealing at 350oC in vacuum atmosphere. The electrical properties of the film were determined by the Hall method using standard clove-leaf geometry. The results indicated that: when the Nb concentration increases followed by the numbers of electrons increase from 4×1018 cm-3 to 2.4×1020 cm-3. Meanwhile the resistivity fall down from10 to 3.5×10-3Ωcm.It means that thisco-sputtering process is good method to improve conducting properties of Nb:TiO_2 thin film. With low resistivity and high optical transmittance (higher than 80% in the visible range),the fabricated thin film can be applicable for transparent conducting electrodes.
  • Streaming Potential in Unconsolidated Samples Saturated with Monovalent Electrolytes

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    The streaming potential coefficientof 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 factoretc. 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 forfour unconsolidated samples (sandpacks) saturated with four monovalent electrolytes at six different electrolyte concentrations have been performed. From the measured streaming potential coefficient, the empirical expression between the streaming potential coefficient and electrolyte concentration is obtained. The obtained expression is in good agreement with those available in literature. Additionally, it is seen that the streaming potential coefficient depends on types of cation in electrolytes and on samples. The dependence of the streaming potential coefficient on types of cation is qualitatively...
  • Design and Simulation of Micromachined Gyroscope based on Finite Element Method

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    This paper presents a design, simulation and analysis of a vibratory micromachining gyroscope. The gyroscope structure is based on the driving and sensing proof-mass configuration. The gyroscope dimensions are 1644 µm wide, 1754 µm long, 30µm thickness. The suspended spring consists of two silicon cantilevers of driving-mode and sensing-mode stiffness are 400 N/m and 165 N/m, respectively. Mass of driving proof-mass (including of 0.9408×10E-11 kg sensing proof-mass) is 0.5452×10E-7 kg. The simulated resonance frequency is 13324 Hz. The output signals are calculated based on the simulated vibration results. The structure is investigated with several input angular signals. The sensitivity of proposed structure is 100 mV/rad/s when ω changes from 0 to 1.6 rad/s.
  • Study long-lived heavy charged particles producedin pp collisions at energy 13 TeV

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    We are interested in long-lived heavy charged particlesbecause they would be possible SUSY particle candidats. This paper shows our preliminary results of long-lived heavy charged particles generation using PYTHIA 8. More than 107 events have been generated with pp collisions at energy in the center of mass = 13 TeV and about 3.27 105long-lived heavy charged particles candidates have been found in the geometric acceptance of the LHCb detector. Long-lived heavy charged particles has mass 1.025 TeV/c2 and lifetime 157.7 ns, therefore they can travel throughout all subdetectors. We try not only calculate their acceptance in function of transverse momentum and rapidity but also combine a pair of candidatswith opposite charge in order to reconstruct their invariant mass. In the next step, we have intention to identify stau using the informations from subdetectors such as the inner tracker and the muon chambers.
  • Investigation of optical properties on BaSnO3 materials

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    Perovskite BaSnO3 materials were synthesized under hydrothermal condition followed heat treatment at variable temperature 423 - 673 K. Phase structure and morphology and optical properties were characterized. Result showed band gap about 3.31 eV and highly optical transparency in the visible spectral region and average particles size 40 -45 nm. Thermal annealing process has affected on phase structure and luminescence in BaSnO3 material.
  • The zeta potential measurements in sandpacks saturated with monovalent electrolytes

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    Measurements of the zeta potential in sandpacks saturated with monovalent electrolytes at six different electrolyte concentrations have been reported. The values we record are classified into two groups based on the magnitude of the zeta potential: group 1 (samples S1 and S2) and group 2 (samples S3 and S4). The measured zeta potential in magnitude in group 1 is much smaller than that in group 2 and in literature at the same electrolyte concentration. The reason for a big variation of the zeta potential between group 1 and group 2 may be due to the difference in technique of making sand particles of different size leading to change of particle surface properties. Consequently, the zeta potential that depends on the surface properties would vary. The results show that there is a gradual decrease in the zeta potential with increase in monovalent electrolyte concentration (from 10−4 M to 10−2 M). Additionally, the empirical expressions between the zeta potential and electrolyte concentration are obtained in this work for both group 1 and group 2. The obtained expression for group 2 is in good agreement with those available in literature. From the experimental data in combination...
  • Natural radioactivity and external dose assessment of surface soils in Bolikhamxay province, Laos

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    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 equivalent actitvity (Raeq) are 0.17 ± 0.02 mSv.yr-1 and 154.8 ± 16.1 Bq.kg-1, respectively.
  • EVALUATE THE SPECTRAL CHARACTERISTICS BY EMPIRICAL METHOD AND MONTE CARLO SIMULATION

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    Nowadays, thanks to the evolution of computer science, many simulation programs based on Monte Carlo Method have been developed and used in the various labs. These programs really help the scientists working on empirical fields on modelizing the complicated experiments, calculating the optimal conditions. After that, the nonfictional one will be launched using the have-been-calculated parameters in order to reduce the cost. In this paper, two simulation program (Monte Carlo MCNP5 and Geant4) had been used to simulate the low-background gamma-ray spectrometry GMX35P4-70 detector. Finally, we found out that there is a substantially high agreement between empirical job and simulation using Monte Carlo method.
  • APPLYING THE MODIFIED PERTURBATION THEORY TO HIGH ENERGY SCATTERING IN THE QUASI-POTENTIAL APPROACH

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    Asymptotic behavior of the scattering amplitude for two scalar particles at high energy and fixed momentum transfer is reconsidered in quantum field theory. In the framework of the quasi-potential approach and the modified perturbation theory, a systematic scheme for finding the leading eikonal scattering amplitudes and its corrections are developed and constructed. The differential cross section is also discussed.
  • SOME REMARKS ON CLASS

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    We study some algebraic properties of the subclasses and of functions. We prove these classes are not Noetherian and Gaussian rings. Moreover, we prove that they are algebras in the class.
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