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Piezoelectric polarization and quantum size effects on the vertical transport in AlGaN/GaN resonant tunneling diodes

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Chinese Physics B 2016年第6期25卷 483-488页

作者： Dakhlaoui h Almansour s Department of Physics College of Science for GirlsUniversity of Dammam (UOD)

In this work,the electronic properties of resonant tunneling diodes（RTDs） based on GaN-AlxGa（1-x）N double barriers are investigated by using the non-equilibrium Green functions formalism（NEG）.These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field,which greatly affect the electronic transport *** electronic density,the transmission coefficient,and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric *** influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness,AlxGa1-xN width,and the aluminum concentration *** results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier;it exhibits a series of resonant peaks and valleys as the quantum well width *** addition,it is found that the negative differential resistance（NDR） in the current–voltage（I–V） characteristic strongly depends on aluminum concentration *** is shown that the peak-to-valley ratio（PVR） increases with xAlvalue *** findings open the door for developing vertical transport nitrides-based IsB devices such as Thz lasers and detectors.

关键词： nitride semiconductor resonant tunneling diode current density

Effect of temperature on pull-in voltage and nonlinear vibration behavior of nanoplate-based NEMs under hydrostatic and electrostatic actuations

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Acta Mechanica solida sinica 2017年第2期30卷 174-189页

作者： Farzad Ebrahimi s.h.s.hosseini Department of Mechanical Engineering Faculty of Engineering Imam Khomeini International University qazvinIran

This paper deals with the study of the temperature effect on the nonlinear vibration behavior of nanoplate-based nano electromechanical systems（NEMs） subjected to hydrostatic and electrostatic actuations. Using Eringen＇s nonlocal elasticity and Gurtin–Murdoch theory, the nonlocal plate model is derived through hamilton＇s principle. The governing equation which is extremely nonlinear due to the geometrical nonlinearity and electrostatic attraction forces is solved numerically using the differential quadrature method（DQM）. The accuracy of the present method is veriied by comparing the obtained results with the experimental data and those in the literature and very good agreement is obtained. Finally a comprehensive study is carried out to determine the inluence of temperature on the nonlinear vibration characteristics of NEMs made of two different materials including aluminum（Al）and silicon（si） and some conclusions are drawn.

关键词： small scale effect Nano electromechanical system Nonlinear vibration Temperature effect Pull-in voltage

Nonrelativistic shannon information entropy for Kratzer potential

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Chinese Physics B 2016年第4期25卷 37-41页

作者： Najafizade s A hassanabadi h Zarrinkamar s Physics Department University of Shahrood Department of Basic sciences Garmsar Branch Islamic Azad University

The shannon information entropy is investigated within the nonrelativistic framework. The Kratzer potential is con- sidered as the interaction and the problem is solved in a quasi-exact analytical manner to discuss the ground and first excited states. some interesting features of the information entropy densities as well as the probability densities are demonstrated. The Bialynicki-Birula-Mycielski inequality is also tested and found to hold for these cases.

关键词： schrOdinger equation Kratzer potential shannon entropy

Variation of the mechanical properties of tungsten heavy alloys tested at different temperatures

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Rare Metals 2011年第4期30卷 392-395页

作者： s.h.Islam Research Center College of EngineeringKing Saud University

The high-temperature mechanical properties of 95W-3.5Ni-1.5Fe and 95W-4.5Ni-0.5Co alloys were investigated in the temperature range of room temperature to1100℃. The yield strength and tensile strengths declined gradually, and the ductility of both alloys increased as the testing temperature was increased to 300℃. All the three properties reached a plateau at temperatures between 300 and 500℃ in the case of 95W-3.5Ni-l.5Fe and at temperatures between 350 and 700℃ in the case of 95W-4.5Ni-0.5Co. Thereafter, the ductility as well as yield and tensile strengths decreased considerably.

关键词： liquid phase sintering tungsten alloys tensile testing mechanical properties

Electron-Cyclotron Laser Using Free-Electron Two-Quantum stark Radiation in a strong Uniform Axial Magnetic Field and an Alternating Axial Electric Field in a Voltage-supplied Pill-Box Cavity

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Chinese Physics Letters 2016年第3期33卷 56-59页

作者： s.h.Kim Church Road 9236 Dallas Texas 75231 USA

We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.

关键词： of on in that Electron-Cyclotron Laser Using Free-Electron Two-Quantum stark Radiation in a strong Uniform Axial Magnetic Field and an Alternating Axial Electric Field in a Voltage-supplied Pill-Box Cavity is stark

Elastic, thermodynamic, electronic, and optical properties of recently discovered superconducting transition metal boride NbRuB:An ab-initio investigation

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Chinese Physics B 2017年第10期26卷 339-347页

作者： F Parvin s h Naqib Department of Physics University of Rajshahi

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation （GGA） and local density approximation （LDA） are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency （energy） dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.

关键词： hard materials ternary borides DFT calculations electronic band structure optical properties superconductivity

A control volume based finite element method for simulating incompressible two-phase flow in heterogeneous porous media and its application to reservoir engineering

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Petroleum science 2012年第4期9卷 485-497页

作者： sADRNEJAD s A GhAsEMZADEh h GhOREIshIAN AMIRI s A MONTAZERI G h Faculty of Civil Engineering K.N.Toosi University of Technology Research and Development Department Iranian Central Oil Field Co.

Applying the standard Galerkin finite element method for solving flow problems in porous media encounters some difficulties such as numerical oscillation at the shock front and discontinuity of the velocity field on element *** of velocity field leads this method not to conserve mass ***,the accuracy and stability of a solution is highly affected by a non-conservative *** this paper,a three dimensional control volume finite element method is developed for twophase fluid flow simulation which overcomes the deficiency of the standard finite element method,and attains high-orders of accuracy at a reasonable computational ***,this method is capable of handling heterogeneity in a very rational way.A fully implicit scheme is applied to temporal discretization of the governing equations to achieve an unconditionally stable *** accuracy and efficiency of the method are verified by simulating some waterflooding *** representative examples are presented to illustrate the capability of the method to simulate two-phase fluid flow in heterogeneous porous media.

关键词： Finite element method control volume two-phase flow heterogeneity porous media waterflooding

Application of control volume based finite element method for solving the black-oil fluid equations

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Petroleum science 2013年第3期10卷 361-372页

作者： GhOREIshIAN AMIRI s A sADRNEJAD s A GhAsEMZADEh h MONTAZERI G h Faculty of Civil Engineering K. N. Toosi University of TechnologyTehran Iran Research and Development Dept. Iranian Central Oil Field Co.Tehran Iran

This is the second paper of a series where we introduce a control volume based finite element method （CVFEM） to simulate multiphase flow in porous media. This is a fully conservative method able to deal with unstructured grids which can be used for representing any complexity of reservoir geometry and its geological objects in an accurate and efficient manner. In order to deal with the inherent heterogeneity of the reservoirs, all operations related to discretization are performed at the element level in a manner similar to classical finite element method （FEM）. Moreover, the proposed method can effectively reduce the so-called grid orientation effects. In the first paper of this series, we presented this method and its application for incompressible and immiscible two-phase flow simulation in homogeneous and heterogeneous porous media. In this paper, we evaluate the capability of the method in the solution of highly nonlinear and coupled partial differential equations by simulating hydrocarbon reservoirs using the black-oil model. Furthermore, the effect of grid orientation is investigated by simulating a benchmark waterflooding problem. The numerical results show that the formulation presented here is efficient and accurate for solving the bubble point and three-phase coning problems.

关键词： Control volume based finite element,black-oil model grid orientation porous media

OsCILLATION AND GLOBAL ATTRACTIVITY OF IMPULsIVE PERIODIC DELAY REsPIRATORY DYNAMICs MODEL

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Chinese Annals of Mathematics,series B 2005年第4期26卷 511-522页

作者： s.h.sAKER Department of Mathematics Faculty of ScienceMansoura UniversityMansoura 35516Egypt

This paper studies the nonlinear delay impulsive respiratory dynamics model. The model describes the sudden changes of the concentration of CO2 in the blood of the mammal. It is proved that the model has a unique positive periodic solution. somesufficient conditions for oscillation of all positive solutions about the positive periodic solution are established and also some sufficient conditions for the global attractivityof the periodic solution are obtained.

关键词： Periodic solutions Oscillation Global attractivity Respiratory dynamics model Impulsive differential equation