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Parallel propagating modes and anomalous spatial damping in the ultra-relativistic electron plasma with arbitrary degeneracy

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Chinese Physics B 2017年第11期26卷 76-82页

作者： h Farooq m Sarfraz Z Iqbal G Abbas h A Shah Department of Physics Government College University Government College University

The dispersion relations of parallel propagating modes（Langmuir mode, right and left handed circular polarized waves） in the weak magnetic field limit ｜ω-k·v｜〉〉？ are considered for ultra-relativistic arbitrary degenerate electron plasma. The results are presented in terms of moments of Fermi-Dirac distribution. The increase in the electron equilibrium number density from negative large（weakly degenerate） to positive large（highly degenerate） values of μ/Te is observed（where μ is the electron chemical potential and Te is the electron thermal energy）. As a result, shifting of the cutoff points in all the real dispersion branches towards the higher values and increasing in the band gap between unmagnetized longitudinal and transverse modes in k-space are examined. Also, the suppression of the weak magnetic field effects in weakly magnetized right handed and left handed circular polarized waves and a decrease in the longitudinal and transverse screening effects are observed in the graphical patterns due to an increase in the equilibrium number density.

关键词： degenerate Fermi gases relativistic plasmas electromagnetic waves

Is there more than one stickiness criterion?

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Friction 2023年第6期11卷 1027-1039页

作者： Anle WANG martin h.müSER Department of material Science and Engineering Saarland UniversitySaarbrücken66123Germany INm—Leibniz Institute for New materials Saarbrücken66123Germany

Adhesion between an elastic body and a smooth,rigid substrate can lead to large tensile stresses between ***,most macroscopic objects are microscopically rough,which strongly suppresses adhesion.A fierce debate has unfolded recently as to whether local or global parameters determine the crossover between small and large ***,we report simulations revealing that the dependence of the pull-off force Fn on the surface energyγdoes not only have two regimes of high and low adhesion but up to four *** are related to contacts,which at the moment of rupture consist of(i)the last individual hertzian-shaped contact,in which is linear inγ,(ii)a last meso-scale,individual patches with super-linear scaling,(iii)many isolated contact patches with extremely strong scaling,and(iv)a dominating largest contact patch,for which the pull-off stress is no longer negligible compared to the maximum,microscopic pull-off ***(iii)can be seen as a transition *** is located near the point where the surface energy is half the elastic energy per unit area in conformal contact.A criterion for the transition between regimes(i)and(ii)appears difficult to grasp.

关键词： adhesion pull-off force rough contact stickiness

Study of Three Different Types of Plasma Ion Sources

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Plasma Science and Technology 2009年第5期11卷 604-608页

作者： m.m.ABDELRAhmAN h.EL-KhABEARy Accelerators & Ion Sources Department Nuclear Research CenterAtomic Energy Authority

Three types of plasma ion sources designed, manufactured and optimized in the Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority are introduced. Different means were investigated to generate the discharge current and ion beam current extracted from the plasma. The various plasmas described include a DC glow discharge plasma, an arc discharge plasma and a radio frequency discharge plasma.

关键词： ion sources ionization processes sputtering and etching processes

Thermal vibration of functionally graded porous nanocomposite beams reinforced by graphene platelets

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Applied mathematics and mechanics(English Edition) 2020年第8期41卷 1209-1226页

作者： m.h.YAS S.RAhImI Department of mechanical Engineering Razi UniversityKermanshah 67346-67149Iran

The thermal vibration of functionally graded(FG)porous nanocomposite beams reinforced by graphene platelets(GPLs)is *** beams are exposed to the thermal gradient with a multilayer *** temperature varies linearly across the thickness *** different types of dispersion patterns of GPLs as well as porosity distributions are *** material properties vary along the thickness *** using the mechanical parameters of closed-cell cellular solid,the variation of Poisson’s ratio and the relation between the porosity coefficient and the mass density under the Gaussian random field(GRF)model are *** using the halpin-Tsai micromechanics model,the elastic modulus of the nanocomposite is *** equations of motion based on the Timoshenko beam theory are obtained by using hamilton’s *** equations are discretized and solved by using the generalized differential quadrature method(GDQm)to obtain the fundamental *** effects of the weight fraction,the dispersion model,the geometry,and the size of GPLs,as well as the porosity distribution,the porosity coefficient,the boundary condition,the metal matrix,the slenderness ratio,and the thermal gradient are presented.

关键词： thermal vibration functionally graded(FG) porous material graphene platelet(GPL) Timoshenko beam

Calculation of the infrared frequency and the damping constant (full width at half maximum) for metal organic frameworks

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Chinese Physics B 2019年第6期28卷 324-331页

作者： m Kurt h Yurtseven A Kurt S Aksoy Department of Physics Canakkale 18 Mart University17100 CanakkaleTurkey Department of Physics Middle East Technical University06531 AnkaraTurkey Lapseki ICDAS CIB mTAL high School 17100 CanakkaleTurkey

The ρ(Nh2) infrared(IR) frequencies and the corresponding full width at half maximum(FWhm) values for(Ch3)2 Nh2 FeⅢ m Ⅱ(hCOO)6(DmFe m, m = Ni, Zn, Cu, Fe, and mg) are analyzed at various temperatures by using the experimental data from the literature. For the analysis of the IR frequencies of the ρ(Nh2) mode which is associated with the structural phase transitions in those metal structures, the temperature dependence of the mode frequency is assumed as an order parameter and the IR frequencies are calculated by using the molecular field theory. Also, the temperature dependence of the IR frequencies and of the damping constant as calculated from the models of pseudospin(dynamic disorder of dimethylammonium(DmA+) cations)–phonon coupling(PS) and of the energy fluctuation(EF), is fitted to the observed data for the wavenumber and FWhm of the ρ(Nh2) IR mode of the niccolites studied here. We find that the observed behavior of the IR frequencies and the FWhm of this mode can be described adequately by the models studied for the crystalline structures of interest. This method of calculating the frequencies(IR and Raman) and FWhm of modes which are responsible for the phase transitions can also be applied to some other metal organic frameworks.

关键词： infrared(IR) frequency full width at half maximum(FWhm) phase transitions ρ(Nh2) mode niccolites

Dynamic and buckling analysis of polymer hybrid composite beam with variable thickness

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Applied mathematics and mechanics(English Edition) 2020年第5期41卷 785-804页

作者： S.AFShIN m.h.YAS Department of mechanical Engineering Razi UniversityKermanshah 67149Iran

This work deals with a study of the dynamic and buckling analysis of polymer hybrid composite(PhC) beam. The beam has variable thickness and is reinforced by carbon nanotubes(CNTs) and nanoclay(NC) simultaneously. The governing equations are derived based on the first shear deformation theory(FSDT). A three-phase halpinTsai approach is used to predict the mechanical properties of the PhC. We focus our attention on the effect of the simultaneous addition of NC and CNT on the vibration and buckling analysis of the PhC beam with variable thickness. Also a comparison study is done on the sensation of three impressive parameters including CNT, NC weight fractions, and the shape factor of fillers on the mechanical properties of PhC beams,as well as fundamental frequencies of free vibrations and critical buckling load. The results show that the increase of shape factor value, NC, and CNT weight fractions leads to considerable reinforcement in mechanical properties as well as increase of the dimensionless fundamental frequency and buckling load. The variation of CNT weight fraction on elastic modulus is more sensitive rather than shear modulus but the effect of NC weight fraction on elastic and shear moduli is fairly the same. The shape factor values more than the medium level do not affect the mechanical properties.

关键词： polymer hybrid composite(PhC) halpin-Tsai carbon nanotube(CNT) nanoclay(NC) free vibration buckling load

Electrical features of radio-frequency atmospheric pressure helium discharge with and without dielectric electrodes

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Plasma Science and Technology 2019年第2期21卷 60-67页

作者： h AShRAF S Z A ShAh h I A QAZI m A KhAN S hUSSAIN m A BADAR S NIAZ m ShAFIQ Department of Physics University of Sargodha Department of Physics Quaid-i-Azam University

A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes,impedance measurements have been performed and compared with equivalent circuit *** measured impedance data is found to be in good agreement with simulated data.

关键词： radiofrequency atmospheric pressure glow discharge dielectric electrodes plasma stability control

New ternary superconducting compound LaRu2As2： Physical properties from density functional theory calculations

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Chinese Physics B 2017年第3期26卷 453-460页

作者： m A hadi m S Ali S h Naqib A K m A Islam Department of Physics University of Rajshahi Rajshahi 6205 Bangladesh Department of Physics Pabna University of Science and Technology Pabna 6600 Bangladesh International Islamic University Chittagong Chittagong 4203 Bangladesh

In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elas- tic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh＇s ratio as well as Poisson＇s ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating （TBC） material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.

关键词： new superconductor LaRu2As2 density functional theory (DFT) calculations mechanical proper-ties electronic features

Plasmonic Nanostructured Electromagnetic materials

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Chinese Physics Letters 2012年第9期29卷 133-137页

作者： h.Sadeghi h.Khalili m.Goodarzi Department of Physics Faculty of ScienceArak UniversityArak 8349-8-38156Iran

We study the materials that are composed of metals and *** plasmonic and non-plasmonic materials are ordered in geometric arrangements with dimensions that are fractions of the wavelength of light.A theoretical model is developed to simulate the refractive index of these nano-structured electromagnetic materials which support surface plasmon *** contributing to the refractive index sensitivity are explored *** with size parameters smaller by much less than 1 have optical properties accurately predicted by the quasi-electrostatic theory while particles with larger size parameters necessitate *** simulate a type of refractive index material composed of metal and insulating dielectric nano-spheres,which are able to sustain the propagation of infrared or visible frequency electromagnetic waves known as surface plasmon polaritons.

关键词： refractive size arrangement