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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

Correlation between Porosity and Fracture mechanism in High Pressure Die Casting of Am60B Alloy

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Journal of materials Science & Technology 2016年第1期32卷 54-61页

作者： X.Li S.m.Xiong z.Guo School of materials Science and Engineering Tsinghua University State Key Laboratory of Automobile Safety and Energy Tsinghua University

X-ray tomography was used to characterize the porosity in high pressure die casting of Am60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosi- ties, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the po- rosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals （ESCs） were present, the crack would propagate along the ESC boundaries in an inter- granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.

关键词： High pressures die casting Am60B alloy Fracture mechanism Porosity

Benzene selective hydrogenation over supported Ni(nano-) particles catalysts: Catalytic and kinetics studies

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Chinese Journal of Chemical Engineering 2018年第3期26卷 521-528页

作者： m.H.Peyrovi N.Parsafard z.mohammadian Faculty of Chemistry Science and Petroleum Department of Physical Chemistry University of Shahid Beheshti Kosar University of Bojnord Department of Applied Chemistry

This report aims to reduce the benzene in a mixture of benzene and toluene as a model reaction using catalytic hydrogenation. In this research, we developed a series of catalysts with different supports such as Ni/HmS, Ni/HzSm-5, Ni/HzSm5-HmS, Ni/Al2O3 and Ni/SiO2. Kinetic of this reaction was investigated under various hydrogen and benzene pressures. For more study, two kinetic models have also been selected and tested to describe the kinetics for this reaction. Both used models, the power law and Langmuir-Hinshelwood, provided a good fit toward the experimental data and allowed to determine the kinetic parameters. Among these catalysts, Ni/Al2O3 showed the maximum benzene conversion （99.19%） at 130℃ for benzene hydrogenation. The lowest toluene conversion was observed for Ni/SiO2. Furthermore, this catalyst presented high selectivity to benzene （75.26%） at 130℃. The catalytic performance （activity, selectivity and stability） and kinetics evaluations were shown that the Ni/SiO2 is an effective catalyst to hydrogenate benzene. It seems that the surface properties particularly pore size are effective parameter compared to other factors such as acidity and metal dispersion in this process.

关键词： Catalytic hydrogenation Power law model Langmuir-Hinshelwood mode Selectivity Kinetics

The dynamics of a nanosecond gas discharge development with an extended slot cathode in argon

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Plasma Science and Technology 2020年第12期22卷 78-88页

作者： N A ASHURBEKOV K O ImINOV G S SHAKHSINOV m z zAKARYAEVA K m RABADANOV Dagestan State University Faculty of PhysicsMakhachkala 367000Russia Institute of Physics DFRC of RASMakhachkala 367015Russia

The article presents the results of an experimental study and numerical modelling for the formation and development dynamics of a high-voltage transverse nanosecond discharge generated by a slot cathode in an argon medium at a pressure range of 1–10 Torr. Numerical modelling was carried out under similar experimental conditions for the processes of formation and propagation of ionisation waves, electron density distribution, excited atom and average electron energy in the discharge gap, including the cavity inside the cathode. At a pressure of p=1 Torr, a classical version of a high-voltage discharge is demonstrated to take place with no penetration of the plasma into the cathode cavity and no observed hollow cathode effect. An increase in gas pressure to 5 Torr leads to a penetration of plasma into the cathode cavity with the formation of a cathodic potential drop(CPD) region. Electrons emitted from the side surfaces of the cavity pass through the CPD region without collisions, oscillate inside the cathode cavity;the hollow cathode effect is fully manifested. At р=10 Torr, the modelling results qualitatively coincide with the results at р=5 Torr;in this case, however, hardly any accelerated electrons are observed in the gap between the electrodes, due to their energetic relaxation both inside the cathode cavity and when exiting from it. In both cases, the plasma structure formed at the exit of the cathode cavity involves a concentration of charged particles an order of magnitude higher than that in the rest of the gap, leading to a self-limiting discharge current effect. The results of the numerical modelling are in good agreement with experimental data.

关键词： nanosecond gas discharge numerical simulation argon excited atoms

Fabrication and Characterization of a 2×2 microfiber Knot Resonator Coupler

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Chinese Physics Letters 2012年第8期29卷 96-98页

作者： A.A.Jasim A.z.zulkifli m.z.muhammad H.Ahmad S.W.Harun Department of Electrical Engineering University of Malaya 50603 Kuala LumpurMalaysia Photonics Research Center Department of PhysicsUniversity of Malaya50603 Kuala LumpurMalaysia

A 2×2 microfiber knot resonator(mKR)coupler is *** hybrid device is obtained by forming a knot within the coupling region of a microfiber coupler with a 50:50 splitting *** microfiber coupler is successfully fabricated by laterally fusing and tapering two optical fibers using a flame-brushing *** coupler has an overlapping length of 40 mm with a uniform waist of around 5μ*** an mKR structure,the coupler produces a resonant response at both output *** free spectral range of the output spectrum from both ports is obtained at 0.2 nm at a knot diameter of 260μ*** resonance extinction ratio of the device varies from 2 to 6 dB while the calculated Q factor and finesse are~25646 and 3.3,respectively,at both output ports.

关键词： technique fiber resonator

Impact of coupling geometry on thermoelectric properties of oligophenyl-base transistor

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Chinese Physics B 2017年第2期26卷 420-427页

作者： S Ramezani Akbarabadi H Rahimpour Soleimanit m Bagheri Tagani z Golsanamlou Computational Nanophysics Laboratory （CNL） Department of Physics University of Guilan Rasbt P. O. Box 41335-1914Iran

Thermal and electron transport through organic molecules attached to three-dimensional gold electrodes in two different configurations, namely para and meta with thiol-terminated junctions is studied theoretically in the linear response regime using Green＇s function formalism. We used thiol-terminated（–SH bond） benzene units and found a positive thermopower because the highest occupied molecular orbital（HOmO） is near the Fermi energy level. We investigated the influence of molecular length and molecular junction geometry on the thermoelectric properties. Our results show that the thermoelectric properties are highly sensitive to the coupling geometry and the molecular length. In addition, we observed that the interference effects and increasing molecular length can increase the thermoelectric efficiency of device in a specific configuration.

关键词： coupling geometry figure of merit Green's function oligophenyl thermopower

Formation of TiAlSi intermetallics during heating Ti-A356 Al mixed powder compact at semisolid temperature

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Journal of materials Science & Technology 2021年第35期94卷 247-263页

作者： m.Gao T.J.Chen z.X.zhang State Key Laboratory of Advanced Processing and Recycling of Nonferrous metals Lanzhou University of TechnologyLanzhou 730050China

Due to the similarity in composition and crystal structure of some Ti Al Si ternary intermetallics,it is quite difficult to accurately confirm their physic characteristics,and thus,to tailor microstructure to improve mechanical properties of metal materials related to the Ti Al Si ***,the formation process of Ti Al Si intermetallics was investigated during heating Ti-A356 mixed powder compact at a A356 alloy semisolid temperature of 595℃.The results indicated that two kinds of intermetallics ofτ1(tetragonal,I41/amd)andτ2(orthorhombic,Cmcm)generated,and both the concentration and supply direction of Ti atoms,which are related to local breakage of oxide films on neighboring Ti and A356 alloy powders,determined the phase and morphology of the intermetallics.τ1 andτ2 crystals all had an intrinsic plate morphology,butτ2 crystals were thinner due to more anisotropic growth resulted from their high density of stacking faults(SFs).τ1 lamellar domains generated during growth ofτ2 crystals,which were accompanied by decrease in density of *** combined effect of size difference and internal energy difference betweenτ1 andτ2 crystals made largeτ1 crystals coarsen at the expense ofτ2 crystals in Ostwald ripening,leading them to finally evolve into an agglomerate of largeτ1 plates.

关键词： Intermetallics Stacking faults Growth Phase transformation

Brownian motion and thermophoresis effects on unsteady stagnation point flow of Eyring-Powell nanofluid: a Galerkin approach

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Communications in Theoretical Physics 2020年第12期72卷 71-82页

作者： z H Khan m Usman T zubair m Hamid R U Haq State Key Laboratory of Hydraulics and mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu610065China BIC-ESAT College of EngineeringPeking UniversityBeijing 100871China State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering SciencePeking UniversityBeijing 100871China Institute of Ocean Research Peking UniversityBeijing 100871China School of mathematical Sciences Peking UniversityBeijing 100871China Department of mechanics and Engineering Science Fudan UniversityShanghai 200433China Department of Electrical Engineering Bahria UniversityIslamabad CampusIslamabad 44000Pakistan

This article concerns the analysis of an unsteady stagnation point flow of Eyring–Powell nanofluid over a stretching *** influence of thermophoresis and Brownian motion is also considered in transport *** nonlinear ODE set is obtained from the governing nonlinear equations via suitable *** numerical experiments are performed using the Galerkin scheme.A tabular form comparison analysis of outcomes attained via the Galerkin approach and numerical scheme(RK-4)is available to show the credibility of the Galerkin *** numerical exploration is carried out for various governing parameters,namely,Brownian motion,steadiness,thermophoresis,stretching ratio,velocity slip,concentration slip,thermal slip,and fluid parameters,and Hartmann,Prandtl and Schmidt *** velocity of fluid enhances with an increase in fluid and magnetic parameters for the case of opposing,but the behavior is reversed for assisting *** Brownian motion and thermophoresis parameters cause an increase in temperature for both cases(assisting and opposing).The Brownian motion parameter provides a drop-in concentration while an increase is noticed for the thermophoresis *** the outcomes and the behavior of emerging parameters are illustrated *** comparison analysis and graphical plots endorse the appropriateness of the Galerkin *** is concluded that said method could be extended to other problems of a complex nature.

关键词： Eyring-Powell fluid stagnation point flow Brownian motion and thermophoresis Galerkin method

Synergetic deformation mechanisms in an mg-zn-Y-zr alloy with intragranular LPSO structures

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Journal of magnesium and Alloys 2023年第5期11卷 1754-1768页

作者： z.z.Peng X.H.Shao z.m.Liang D.L.Wang L.W.Wang X.L.ma Hebei Key Laboratory of material Near-Net Forming Technology School of Materials Science and EngineeringHebei University of Science and TechnologyShijiazhuang 050018China Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences72 Whenua RoadShenyang 110016China

Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(mg)alloys,while the deformation twin is generally *** optimize the mechanical properties of LPSO containing mg alloy by simultaneously exciting kink and twin,we successfully prepared the mg-zn-Y-zr alloy featuring intragranular LPSO phase and free grain boundary LPSO phase by *** unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical *** high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and twining in the *** the activation of kinking and twinning depends on the thicknesses of LPSO lamellae and their relative *** results may shed light on optimizing the design of mg alloys regulating the microstructure of LPSO phases.

关键词： mg alloy LPSO distribution Kink Twin Transmission electron microscopy

Effect of Rotation Rate on microstructures and mechanical Properties of FSW mg-zn-Y-zr Alloy Joints

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Journal of materials Science & Technology 2011年第12期27卷 1157-1164页

作者： G.m. Xie z.Y. ma z.A. Luo P. Xue G.D. Wang The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China

Friction stir welding （FSW） of mg-zn-Y-zr plates with 6 mm in thickness was successfully carried out under a wide range of rotation rates of 600-1200 r/rain with a constant traverse speed of 100 mm/min. After FSW, the coarse grains in the parent material （Pm） were changed into fine equiaxed recrystallized grains at the＇nugget zone （Nz）. Furthermore, the coarse mg-zn-Y particles （W-phase） were broken up and dispersed homogenously into the mg matrix. With increasing rotation rates, the size of the W-phase particles at the Nz significantly decreased, but the recrystallized grain size tended to increase. The hardness values of the Nzs for all the FSW joints were higher than those of the Pm, and the lowest hardness values were detected in the heat affected zone （HAz）. The fracture occurred in the thermo-mechanical affected zone （TmAz） on the advancing side for all the FSW joints in the tensile test, due to the incompatibility of the plastic deformation between the Nz and TmAz caused by remarkably different orientation of grains and W-phase particles. The strength of FEW ioint reaches 90% of that of its Pm

关键词： Friction stir welding magnesium alloys microstructure mechanical property