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Relativistic symmetry of position-dependent mass particles in a Coulomb field including tensor interaction

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Chinese Physics B 2013年第3期22卷 122-128页

作者： m.Eshghi m.Hamzavi S.m.Ikhdair Physics Department Imam Hossein Comprehensive UniversityTehranIran Department of Science and Engineering Abhar BranchIslamic Azad UniversityAbharIran Department of Electrical and Electronic Engineering Near East University922022NicosiaNorthern CyprusTurkey Department of Physics Faculty of ScienceAn-Najah National UniversityNablusWest BankPalestine

The spatially-dependent mass Dirac equation is solved exactly for attractive scalar and repulsive vector Coulomb potentials,including a tensor interaction under the spin and pseudospin symmetric *** forms of the energy eigenvalue equation and wave functions are obtained for arbitrary spin-orbit quantum number κ.Some numerical results are also given,and the effect of tensor interaction on the bound states is *** is shown that tensor interaction removes the degeneracy between two states in the spin *** also investigate the effects of the spatially-dependent mass on the bound states under spin symmetric limit conditions in the absence of tensor interaction.

关键词： Dirac equation spin and pseudospin symmetries spatially-dependent mass tensor interaction

Reliability analysis of extended generalized inverted exponential distribution with applications

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Journal of Systems Engineering and Electronics 2016年第2期27卷 484-492页

作者： Arwa m.Alshangiti m.Kayid m.Almulhim Department of Statistics and Operations Research College of Science King Saud University

A general version of the inverted exponential distribution is introduced, studied and analyzed. This generalization depends on the method of marshall-Olkin to extend a family of distributions. Some statistical and reliability properties of this family are studied. In addition, numerical estimation of the maximum likelihood estimate（mLE） parameters are discussed in details. As an application, some real data sets are analyzed and it is observed that the presented family provides a better fit than some other known distributions.

关键词： inverted exponential distribution reliability properties statistical properties maximum likelihood estimates applications

Numerical and experimental analysis of the closed-cell aluminium foam under low velocity impact using computerized tomography technique

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Acta mechanica Sinica 2019年第1期35卷 144-155,I0005页

作者： S.Talebi m.Sadighi m.m.Aghdam Department of mechanical Engineering Amirkabir University of TechnologyTehranIran

In the present work, the response of closed-cell aluminum foams under low-velocity impact has been studied numerically and experimentally. Computerized tomography is employed to access three-dimensional (3D) microstructure of the closed-cell aluminum foam. Effective parameters including foam density and the velocity of impactor on foam dynamic behavior are investigated. In order to show the validity and accuracy of results, some static experiments and low-velocity impact tests have been conducted. Results in dicate a remarkable agree me nt between the simulation and experimental data. moreover, the results show that by increasing the density of foam samples, the highest difference between numerical and experimenidi results for peak stress and absorbed energy are 35.9% and 6.9%, respectively, which is related to the highest density. For impact velocities ranging from 3.1 to 4.2 m/s, the maximum discrepancy in peak stress and absorbed energy occur at an inipact velocity of 3.1 m/s in which corresponding errors are 33.3% and 6.6%, respectively. For the impact velocity of 40 m/s, the highest increase in peak stress and absorbed energy are 667.9% and 370.3% associated with the density of 0.5 and 0.3 g/cm^3, respectively.

关键词： Finite element analysis Impact Aluminum foam Experimental analysis Energy absorption

Electrodeless plasma thrusters for spacecraft: a review

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Plasma Science and Technology 2017年第8期19卷 1-24页

作者： S N BATHGATE m m m BILEK D R mCKENZIE Applied and Plasma Physics School of PhysicsUniversity of Sydney

The physics of electrodeless electric thrusters that use directed plasma to propel spacecraft without employing electrodes subject to plasma erosion is reviewed. Electrodeless plasma thrusters are potentially more durable than presently deployed thrusters that use electrodes such as gridded ion,Hall thrusters, arcjets and resistojets. Like other plasma thrusters, electrodeless thrusters have the advantage of reduced fuel mass compared to chemical thrusters that produce the same thrust. The status of electrodeless plasma thrusters that could be used in communications satellites and in spacecraft for interplanetary missions is examined. Electrodeless thrusters under development or planned for deployment include devices that use a rotating magnetic field; devices that use a rotating electric field; pulsed inductive devices that exploit the Lorentz force on an induced current loop in a plasma; devices that use radiofrequency fields to heat plasmas and have magnetic nozzles to accelerate the hot plasma and other devices that exploit the Lorentz force. Using metrics of specific impulse and thrust efficiency, we find that the most promising designs are those that use Lorentz forces directly to expel plasma and those that use magnetic nozzles to accelerate plasma.

关键词： spacecraft a review propellant Lorentz thrust rotating radiofrequency erosion presently exploit

Nonlinear buckling and postbuckling behavior of cylindrical shear deformable nanoshells subjected to radial compression including surface free energy effects

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Acta mechanica Solida Sinica 2017年第2期30卷 209-222页

作者： S.Sahmani m.m.Aghdam m.Bahrami Department of mechanical Engineering Amirkabir University of Technology P.O. Box 15875-4413 Tehran Iran

The objective of the present investigation is to predict the nonlinear buckling and postbuckling characteristics of cylindrical shear deformable nanoshells with and without initial imperfection under hydrostatic pressure load in the presence of surface free energy *** this end, Gurtin-murdoch elasticity theory is implemented into the irst-order shear deformation shell theory to develop a size-dependent shell model which has an excellent capability to take surface free energy effects into account. A linear variation through the shell thickness is assumed for the normal stress component of the bulk to satisfy the equilibrium conditions on the surfaces of nanoshell. On the basis of variational approach and using von Karman-Donnell-type of kinematic nonlinearity, the non-classical governing differential equations are derived. Then a boundary layer theory of shell buckling is employed incorporating the effects of surface free energy in conjunction with nonlinear prebuckling deformations, large delections in the postbuckling domain and initial geometric imperfection. Finally, an eficient solution methodology based on a two-stepped singular perturbation technique is put into use in order to obtain the critical buckling loads and postbuckling equilibrium paths corresponding to various geometric parameters. It is demonstrated that the surface free energy effects cause increases in both the critical buckling pressure and critical end-shortening of a nanoshell made of silicon.

关键词： Nanoscale structures Size effect Nonlinear buckling Surface free energy Boundary layer theory

Head-on collision between single-and multi-soliton heavy ion acoustic waves in multi-ion plasmas

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Plasma Science and Technology 2019年第9期21卷 58-72页

作者： m S ALAm m R TALUKDER Department of mathematics Chittagong University of Engineering and Technology Chittagong-4349 Bangladesh Plasma Science and Technology Lab Department of Electrical and Electronic Engineering University of Rajshahi Rajshahi-6205 Bangladesh

Head-on collisions among the single-and multi-soliton’s heavy ion acoustic waves(HIAWs) of multi-ion plasma are studied. The plasma consists of adiabatic positively charged inertial heavy ions, Boltzmann energy distributed light ions and kappa energy distributed electrons. The extended poincaré-Lighthill-Kuo(e PLK) method is applied for the derivation of two-sided Korteweg–de Vries(KdV) equations(KdVEs). The KdV single-soliton solutions(KdVSSs) are determined using the hyperbolic secant method and the KdV multi-soliton solutions(KdVmSs)are obtained using the Hirota method. The effects of superthermality of electrons, temperature ratios of electron to light ion and heavy ion to electron, and the density ratio of electron to heavy ion on phase shifts are investigated for the head-on collisions between two-soliton HIAWs. The effects of plasma parameters on angular frequency, phase speed, production of multi-soliton structures, and the head-on collisions among single-, double-, triple-, quadruple-, and quintuplesolitons are also studied.

关键词： HIAWs multi-soliton kappa-distribution ePLK method Hirotta's method multi-ion

Diagnostic Study of an Fe-Ni Alloy Plasma Generated by the Fundamental (1064 nm) and Second (532 nm) Harmonics of an Nd: YAG Laser

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Plasma Science and Technology 2013年第5期15卷 397-402页

作者： m.HANIF m.SALIK m. A. BAIG mCS National University of Sciences & Technology (NUST) School of Science Beijing Jiaotong University National Center for Physics Quaid-i-Azam University Campus

We studied the spatial evolution of the Fe-Ni plasma generated by the fundamental （1064 nm） and second （532 nm） harmonics of a Q-switched Nd： YAG laser. The experimentally observed line profiles of the neutral iron （Fe I） have been used to extract the plasma temperature （T e ） using the Boltzmann plot method, whereas the electron number density （N e ） has been deter- mined from the Stark broadening. In addition, we studied the spatial behavior of T e and N e with the variation of laser energy for iron plasma by placing the target material （iron-nickel alloy） in air at atmospheric pressure for both modes of the Nd： YAG laser.

关键词： iron plasma laser ablation electron temperature electron number density

An ab initio investigation of vibrational, thermodynamic, and optical properties of Sc_2AlC mAX compound

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Chinese Physics B 2016年第10期25卷 103-108页

作者： m A Ali m T Nasir m R Khatun A K m A Islam S H Naqib Department of Physics Chittagong University of Engineering and Technology Department of Arts & Sciences Bangladesh Army University of Science and Technology Department of Physics University of Rajshahi International Islamic University Chittagong

The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled mAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural properties of ScAlC are compared with the results reported earlier. The vibrational, thermodynamical, and optical properties are theoretically estimated for the first time. The phonon dispersion curve is calculated and the dynamical stability of this compound is investigated. The optical and acoustic modes are observed clearly. We calculate the Helmholtz free energy(F), internal energy(E), entropy(S), and specific heat capacity(Cv) from the phonon density of states. Various optical parameters are also calculated. The reflectance spectrum shows that this compound has the potential to be used as an efficient solar reflector.

关键词： mAX compound phonon dispersion thermodynamical properties optical properties

Stochastic seismic response of multi-layered soil with random layer heights

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Earthquake Engineering and Engineering Vibration 2010年第2期9卷 213-221页

作者： m.Badaoui m.K.Berrah A.mébarki Université Paris-Est Laboratoire Modélisation et Simulation Multi Echelle Ecole Nationale Polytechnique

This paper deals with the effect of layer height randomness on the seismic response of a layered soil. These parameters are assumed to be lognormal random variables. The analysis is carried out via monte Carlo simulations coupled with the stiffness matrix method. A parametric study is conducted to derive the stochastic behavior of the peak ground acceleration and its response spectrum,the transfer function and the amplification factors. The input soil characteristics correspond to a site in mexico City and the input seismic accelerations correspond to the Loma Prieta earthquake. It is found that the layer height heterogeneity causes a widening of the frequency content and a slight increase in the fundamental frequency of the soil profile,indicating that the resonance phenomenon is a concern for a large number of structures. Variation of the layer height randomness acts as a variation of the incident angle,i.e.,a decrease of the amplitude and a shift of the resonant frequencies.

关键词： random layer heights layered soil seismic acceleration lognormal distribution amplification factors mexico City