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Two New Solutions of Non-constant-α Force-Free Magnetic Field

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Communications in Theoretical Physics 2006年第3X期46卷 561-562页

作者： XIE bai-Song Key Laboratory of Beam Technology and Materials Modification of Ministry of Education Beijing Normal UniversityBeijing 100875 China Institute of Low Energy Nuclear Physics Beijing Normal University Beijing 100875 China Beijing Radiation Center Beijing 100875 China

Two new solutions for non-constant-α force-free magnetic field are found analytically. Implications of the results to astrophysical solar plasmas as well tokamak plasmas are discussed.

关键词： magnetohydrodynamics magnetic confinement and equilibrium

Efficient and Reliable Nanoindentation Simulation by Dislocation Loop Erasing Method

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Acta Mechanica Solida Sinica 2020年第5期33卷 586-599页

作者： Fei Shuang Pan Xiao yilong bai LNM Institute of MechanicsChinese Academy of SciencesBeijing100190China Department of Mechanical and Aerospace Engineering University of FloridaGainesvilleFL32611USA

Nanoindentation is a useful technique to measure material properties at microscopic ***,the intrinsically multiscale nature makes it challenging for large-scale simulations to be carried *** is shown that in molecular statics simulations of nanoindentation,the separated dislocation loops(SDLs)are trapped in simulation box which detrimentally affects the plastic behavior in the plastic zone(PZ);and the long-distance propagation of SDLs consumes much computational cost yet with little contribution to the variation of tip *** tackle the problem,the dislocation loop erasing(DLE)method is proposed in the work to alleviate the influence of artificial boundary conditions on the SDL–PZ interaction and improve simulation *** results indicate that the force–depth curves obtained from simulations with and without DLE are consistent with each other,while the method with DLE yields more reasonable results of microstructural evolution and shows better *** new method provides an alternative approach for large-scale molecular simulation of nanoindentation with reliable results and higher efficiency and also sheds lights on improving existing multiscale methods.

关键词： Nanoindentation Dislocation loops Boundary effects Molecular statics

Plastic deformation behavior of Mg97Zn1y2 extruded alloys

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Transactions of Nonferrous Metals Society of China 2010年第7期20卷 1259-1268页

作者： K.hAGIhARA A.KINOShITA y.SUGINO M.yAMASAKI y.KAWAMURA h.y.yASUDA y.UMAKOShI Division of Materials and Manufacturing Science Graduate School of EngineeringOsaka University2-1Yamada-okaSuitaOsaka 565-0871Japan Department of Materials Science Kumamoto University2-39-1KurokamiKumamoto 860-8555Japan National Institute for Materials Science 1-2-1SengenTsukubaIbaraki 305-0047Japan

The mechanical properties of the Mg97Znly2 extruded alloy containing the long-period stacking ordered phase, the so-called LPSO-phase, with a volume fraction of 24%-25%, were examined by compression tests and cyclic tension-compression deformation tests. The plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2y0.6 and Mg89Zn4y7 （molar fraction, %）, which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1y2 Mg/LPSO two-phase alloy, respectively, were also prepared. By comparing their mechanical properties, the strengthening mechanisms operating in the Mg97Zn1 y2 extruded alloy were discussed. Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion, which led to a large increment of the strength of alloy. In addition, the LPSO-phases, which were aligned along the extrusion direction in Mg97Zn1y2 extruded alloy, acted as hardening phases, just like reinforced fibers.

关键词： plastic deformation yield stress LPSO-phase dislocation twinning

RESEARCh ON REFRACTORy SUPERALLOyS IN ThE hTM 21 PROJECT

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Acta Metallurgica Sinica(English Letters) 2005年第1期18卷 74-80页

作者： y. yamabe-Mitarai h. harada high-Temperature Materials Group National Institute for Materials Science Sengen 1-2-1 Tsukuba Ibaraki 305-0047 JapanHigh-Temperature Materials Group National Institute for Materials Science Sengen 1-2-1 Tsukuba Ibaraki 305-0047 Japan

It was proposed that a new class of alloys based on platinum group metals (PGMs) were called refractory superalloys. These refractory superalloys have an fcc and L12 coherent two-phase structure (similar to that of Ni-based superalloys), high melting temperatures and good potential as structural materials used at temperatures up to 1800 ℃. Our recent results on the microstruc-ture evolution, deformation and fracture behavior of some of these refracotry superalloys, especial Ir- and Rh-base refractory superalloys were reported.

关键词： platinum group metals refractory superalloy microstructure deformation behavior

On M-theory on real toric fibrations

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Communications in Theoretical Physics 2021年第8期73卷 67-74页

作者： A Belhaj h Belmahi M Benali S-E Ennadifi y hassouni y Sekhmani Equipe des Sciences de la matière et du rayonnement ESMaRDépartement de Physique Facultédes SciencesUniversitéMohammed V de RabatMorocco LhEP-MS Département de PhysiqueFaculte des SciencesUniversitéMohammed V de RabatMorocco

Borrowing ideas from elliptic complex geometry, we approach M-theory compactifications on real fibrations. Precisely, we explore real toric equations rather than complex ones exploited in F-theory and related dual models. These geometries have been built by moving real toric manifolds over real bases. Using topological changing behaviors, we unveil certain data associated with gauge sectors relying on affine lie symmetries.

关键词： real fibrations M-theory toric real manifolds affine lie symmetries

Drag reduction characteristics and flow field analysis of textured surface

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Friction 2016年第2期4卷 165-175页

作者： Qingshun bai Jinxuan bai Xiangpan MENG Chengcheng JI yingchun LIANG School of Mechanical and Electrical Engineering Harbin Institute of Technology Harbin 150001 China Shanghai Satellite Equipment Research Institute Shanghai 200000 China

A textured surface with a micro-groove structure exerts a distinct characteristic on drag reduction behavior. The fluid dynamic models of four textured surfaces are constructed in various profile geometries. Computational fluid dynamics is used to study the friction factors and drag reduction properties with various flow speeds on the textured surfaces. The friction coefficient varieties in the interface between the fluid and the textured surface are examined according to the simulation of the four geometries with V-shaped, saw tooth, rectangular, and semi-circular sections. The drag reduction efficiencies decrease with the increase in water velocity while it is less than a certain value. Moreover, the simulation results of the velocity, shear stress, energy, and turbulence effect on the V-shaped groove surface are presented in comparison with those of the smooth surface to illustrate the drag reduction mechanism. The results indicate that the peaks of the V-shaped grooves inhibit the lateral movement of the turbulent flow and generate the secondary vortex, which plays a key role in the impeding momentum exchange, thereby decreasing turbulent bursting intensity and reducing shear stress in the near-wall flow field. The kinetic energy and turbulence analysis shows that the vortex in the near-wall flow field on the textured surface is more stable compared to that on the smooth surface.

关键词： textured surface drag reduction micro-groove computational fluid dynamics (CFD)

Enhanced nitrogen electroreduction performance by the reorganization of local coordination environment of supported single atom on N(O)-dual-doped graphene

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Nano Research 2023年第7期16卷 9099-9106页

作者： Zhiqiang bai Wenhua Zhang yufang Liu School of Physics Henan Normal UniversityXinxiang 453007China School of Cable Engineering Henan Institute of TechnologyXinxiang 453000China hefei National Research Center for Physical Sciences at the Microscale CAS Key Laboratory of Materials for Energy Conversion and Synergetic Innovation Centre of Quantum Information&Quantum PhysicsUniversity of Science and Technology of ChinaHefei 230026China

Developing stable and efficient catalysts for the electroreduction of nitrogen remains a huge challenge and single atom catalysts(SACs)are expected to achieve relatively high ammonia selectivity at low applied *** on density functional theory calculations,the potential application of 27 single transition metal(TM=Sc-Zn,y-Ag,hf-Au)atoms supported by N(O)-dualdoped graphene(TM-O_(2)N_(2)/G)for the electroreduction of nitrogen is intensively *** low nitrogen coverage,W(Mo,Nb,Ta)-O_(2)N_(2)/G are predicted to yield low ammonia selectivity(h side-on mode,*** the increasing N_(2)coverage,the TM-O_(2)N_(2)/G is reconstructed as TM-(N_(2))2N_(2)/*** electroreduction of nitrogen proceeds from end-on adsorbed nitrogen molecule with high ammonia selectivity,and the limiting-potentials are theoretically predicted as-0.20,-0.40,-0.29,and-0.21 V on W(Mo,Nb,Ta)-(N_(2))2N_(2)/G,*** is suggested that utilizing the reorganization of local coordination environments of SACs by high coverage of reactant molecules under reaction condition can not only enhance the activity at lower limiting-potential but also improve the ammonia selectivity.

关键词： nitrogen reduction reaction single atom catalysis local structure reorganization doped graphene electroreduction

Comparative in vitro Study on Pure Metals(Fe,Mn,Mg,Zn and W) as Biodegradable Metals

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Journal of Materials Science & Technology 2013年第7期29卷 619-627页

作者： J.Cheng B.Liu y.h.Wu y.F.Zheng Center for Biomedical Materials and Tissue Engineering Academy for Advanced Interdisciplinary StudiesPeking University State Key Laboratory for Turbulence and Complex System and Department of Materials Science and Engineering College of EngineeringPeking University

Five pure metals including Fe, Mn, Mg, Zn and W have been investigated on their corrosion behavior and in vitro biocompatibility by electrochemical measurement, static immersion test, contact angle measurement, cytotoxicity and hemocompatibility tests. It is found that the sequence of corrosion rate of five metals in hank＇s solution from high to low is： Mg 〉 Fe 〉 Zn 〉 Mn 〉 W. Fe, Mg and W show no cytotoxicity to L929 and ECV304 cells, Mn induces significant cytotoxicity to both L929 and ECV304 cells, and Zn has almost no inhibition effect on the metabolic activities of ECV304 while largely reduces the cell viability of L929 cells. The hemolysis percentage of five pure metals is lower than 5% except for Mg and platelets adhered on Zn has been activated and pseudopodia-like structures can be observed while platelets on the other four metals keep normal.

关键词： Biodegradable metals Cytotoxicity Corrosion Biocompatibflity

EFFECT OF CARBON AND BORON ON MICROSTRUCTURE AND MEChANICAL PROPERTIES OF A SINGLE CRySTAL SUPERALLOy RR 2072

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Acta Metallurgica Sinica(English Letters) 2005年第1期18卷 33-38页

作者： D.h.Kim D.h.ye J.h.Lee y.S.yoo C.y.Jo high Temperature Materials Laboratory Korea Institute of Machinery&Materials 66 SangnamChangwonKyungnam 640-010S.Korea Dept.of Metallurgy Changwon National Univerisity 9 SarimChagwonKyungnam 640-773S.Korea

Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal *** this study the effect of boron on solidification behavior and creep properties of the carbon doped single crystal RR 2072 has been *** order to understand solidification behavior with boron addition,the solid/liquid interface morphology and solidification microstructure were examined with solidification *** relationship between mi-crostructural evolution and creep properties of the carbon and boron modified single crystal has been also investigated.

关键词： single crystal superalloy defect tolerance directional solidification creep rupture