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stochastic method to determine the scale and anomalous diffusion of gusts in a windy atmospheric boundary layer

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Chinese science Bulletin 2014年第2期59卷 4890-4898页

作者： Xueling Cheng fei Hu qingcun zeng state Key laboratory of Atmospheric Boundary layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

In the atmospheric boundary layer, especially during strong wind period, the coherent structures are obvious and related to the direct interaction of the air masses with the ground. In this paper, we used the observation data during dust weather in Northwest Gansu to study the coherent structure and their ‘‘anomalous diffusion''. The structures in the atmospheric boundary layer included turbulent fluctuations and gusty wind disturbances, and could be denoted as ‘‘critical events' '. Their fractal dimensions were expressed by the complex index l of waiting times. Although the complex index can indicate the ability of the system to generate coherent structures, it has a strong dependence on the threshold marking the‘‘critical events' '. Hence, the continuous time random walk method was used to analyze the coherent structures. The scaling law of anomalous diffusion of coherent structures was obtained, and the diffusion scaling exponent H that indicated the ability of diffusion of different structures was analyzed. The exponents changed with structure scales which were affected by velocities and heights. At small scales, it was almost isotropic, and at large scales, the coherent structures were obvious and the diffusion was anomalous.

关键词：大气边界层结构反常扩散随机游动阵风相干结构扩散能力相互作用观测数据

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Adiabatic shear instability in a titanium alloy:Extreme deformation-induced phase transformation,nanotwinning,and grain refinement

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Journal of Materials science & Technology 2023年第19期150卷 104-113页

作者： X.R.Guan q.Chen s.J.qu G.J.Cao H.wang A.H.feng D.l.Chen school of Materials science and Engineering Tongji UniversityShanghai 201804China southwest Technology and Engineering Research Institute Chongqing 400039China shanghai Key laboratory of D&A for Metal-functional Materials School of Materials Science&EngineeringTongji UniversityShanghai 201804China Key laboratory for light-weight Materials Nanjing Tech UniversityNanjing 210009China Interdisciplinary Center for Additive Manufacturing School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 2000093China Department of Mechanical and Industrial Engineering Toronto Metropolitan University(formerly Ryerson University)TorontoON M5B 2K3Canada

Increasingly harsh service conditions place higher requirements for the high strain-rate performance of titanium *** shear band(AsB),a phenomenon prone to dynamic loading,is often accom-panied by catastrophic ***,it is unclear how the internal nanostructures are related to shear *** we report detailed microstructural evolution in the AsB of a titanium alloy via in-depth focused ion beam(fIB),transmission Kikuchi diffraction(TKD),and high-res.l.tion transmission electron microscope(HRTEM)analyses,with the deformation instability phenomenon discussed from the energy *** AsB interior undergoes multifaceted changes,namely deformation-induced beta-to-alpha transformation and deformation-induced martensitic transformation to form substantially refined and heterogeneous ***,two types of extremely fine twins are identified to occur within both nano-sized martensite and alpha *** critical plastic work representing the onset of adiabatic shear instability and dynamic equilibrium is observed to be constant for a specific structure in the same deformation *** energy analysis could be extended to other materials subjected to high strain-rate dynamic deformation.

关键词： Adiabatic shear instability Deformation-induced phase transformation Deformation-induced nanotwinning Dynamic recovery Energy analysis

ElECTROCHEMICAl NOIsE fEATUREs Of PURE AlUMINUM DURING PITTING CORROsION IN NEUTRAl NaCl s.l.TION

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Acta Metallurgica sinica(English letters) 2003年第1期16卷 20-30页

作者： f.H.Cao Z.Zhang Y.l.Cheng J.f.li J.q.Zhang J.M.wang C.N.Cao Department of Chemistry Zhejiang UniversityHangzhou 310027China state Key laboratory for Corrosion and Protection of Metals Institute of Metal ResearchThe Chinese Academy of SciencesShenyang 110016China

spontaneous electrochemical noise (EN) can be a rich source of information concerning the processes simultaneously occurring at a corroding interface. Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride s.l.tion are investigated, and the breakdown and restoration of passive metal's film are studied using potentiodynamic scanning (PDs) measurements and electrochemical impedance spectroscopy (EIs) technique. Two capacitance loops are observed in the Nyquist plots in two kinds of concentration, and the corrosion process is under activation control at first, then become diffusion control within the oxide film and corrosion products of (Al(OH)p-mCl-m) accumulated on the surface of the corroding electrode. It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wt% than in 2.0wt% NaCl s.l.tion, and the high concentration of chloride ion in s.l.tion inhibits the repassivation of a metastable pit. The corrosion rate deterministic step does not involve Cl-.

关键词： pure aluminum pitting corrosion electrochemical noise electrochemical impedance spectroscopy potentiodynamic scanning

Electron kinetic effects in back-stimulated Raman scattering bursts driven by broadband laser pulses

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Matter and Radiation at Extremes 2024年第4期9卷 54-67页

作者： q.K.liu l.Deng q.wang X.Zhang f.q.Meng Y.P.wang Y.q.Gao H.B.Cai s.P.Zhu Graduate school China Academy of Engineering PhysicsBeijing 100088China Institute of Applied Physics and Computational Mathematics Beijing 100094China school of Nuclear science and Technology University of Science and Technology of ChinaHefei 230026China shanghai Institute of laser Plasma Shanghai 201800China HEDPs Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China school of Physics Zhejiang UniversityHangzhou 310027China

We examine electron kinetic effects in broadband-laser-driven back-stimulated Raman scattering(BsRs)bursts using particle-in-cell *** bursts occur during the nonlinear stage,causing reflectivity spikes and generating large numbers of hot ***-duration simulations are performed to observe burst events,and a simplified model is developed to eliminate the interference of the broadband laser’s random intensity *** the simplified model,we is.l.te and characterize the spectrum of electron plasma *** spectrum changes from a sideband structure to a turbulence-like structure during the burst.A significant asymmetry in the spectrum is *** asymmetry is amplified and transferred to electron phase space by high-intensity broadband laser pulses.l.ading to violent vortex-merging and generation of hot *** proportion of hot electrons increases from 6.76%to 14.7%during a single violent burst *** demonstrate that kinetic effects profoundly influence the BsRs evolution driven by broadband lasers.

关键词： scattering kinetic simplified

EffECTs Of TREATMENT TEMPERATURE ON THE MICROsTRUCTURE AND MAGNETIC PROPERTIEs Of fe-N THIN fIlMs

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Acta Metallurgica sinica(English letters) 2007年第4期20卷 293-300页

作者： B.l. li H.M. Du X.f. wang E.Y. Jiang Z.q.li P. Wu Department of Applied Physics Institute of Advanced Materials Physics School of Science Tianjin University Tianjin 300072 China Tianjin Key laboratory of low Dimensional Materials Physics and Preparing Technology Tianjin University Tianjin 300072 China

fe-N thin films were fabricated on both 100si and NaCl substrates by Rf magnetron sputtering under low nitrogen partial pressure. The microstructure and magnetic properties of fe-N thin films were investigated with the increase of the substrate temperature （Ts） and the annealing temperature （Ta）. It is more difficult for nitrogen atoms to enter the fe lattice under higher Ts above 150℃. The phase evolution is visible at higher Ta above 200℃. The phase transformation of α＇＇-fe16N2 occurred at 400℃. The change of crystal size with Ta was clearly visible from bright and dark field images. The clear high-res.l.tion electron microscope （HREM） images of 110α, 111γ＇, 112α＇＇, and 200α＇＇ phases were observed. The interplanar distances from TEM （transmission electron microscope） and HREM match the calculated values very well. from the res.l.s of the vibrating sample magnetometer （VsM）, the good magnetic properties of fe-N films were obtained at 150℃ of Ts and 200℃ of Ta, respectively.

关键词： fe-N thin film magnetic property HREM α''-fe16N2

Transfer or blockage:Unraveling the interaction between deformation twinning and grain boundary in tantalum under shock loading with molecular dynamics

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Journal of Materials science & Technology 2023年第25期156卷 118-128页

作者： Z.C.Meng M.M.Yang A.H.feng s.J.qu f.Zhao l.Yang J.H.Yao Y.Yang q.B.fan H.wang Interdisciplinary Centre for Additive Manufacturing (ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China school of Materials science and Engineering University of Science and Technology of ChinaShenyang 110016China school of Materials science and Engineering Tongji UniversityShanghai 201804China Academy for Advanced Interdisciplinary studies Southern University of Science and TechnologyShenzhen 518055China National Key laboratory of science and Technology on Materials Under shock and Impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The interaction between{112}deformation twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of twin transfer(TT)or twin blockage(TB),i.e.,twin transfer occurs at MA≤29°with twin blockage *** TT,the value of m’affects the s.l.ction of twin variants.,i.e.,the twin system with a larger m’is easier to *** morphology of twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including grain boundary dislocation emission.

关键词： Plasticity Grain boundary Twin Atomistic simulation Tantalum

Nonlinear mechanics of a ring structure subjected to multi-pairs of evenly distributed equal radial forces

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Acta Mechanica sinica 2017年第5期33卷 942-953页

作者： q. Chen f. sun Z. Y. li l. Taxis N. Pugno Biomechanics.l.boratory School of Biological Science and Medical Engineering Southeast University state Key laboratory of Mechanics and Control of Mechanical structures Nanjing University of Aeronautics and Astronautics school of Chemistry Physics and Mechanical EngineeringQueensland University of Technology (QUT) laboratory of Bio-Inspired and Graphene Nanomechanics Department of Civil Environmental and Mechanical Engineering University of Trento school of Engineering and Materials science Queen Mary University of London Ket lab Italian Space Agency Via del Politecnico snc

Combining the elastica theory, finite element (fE) analysis, and a geometrical topological experiment, we studied the mechanical behavior of a ring subjected to multi-pairs of evenly distributed equal radial forces by looking at its seven distinct states. The res.l.s showed that the theoretical predictions of the ring deformation and strain energy matched the fE res.l.s very well, and that the ring deformations were comparable to the topological experiment. Moreover, no matter whether the ring was compressed or tensioned by N-pairs of forces, the ring always tended to be regular polygons with 2N sides as the force increased, and a proper compressive force deformed the ring into exquisite flower-like patterns. The present study s.l.es a basic mechanical problem of a ring subjected to lateral forces, which can be useful for studying the relevant mechanical behavior of ring structures from the nano- to the macro-scale.

关键词： Ring structures Mechanical properties shape strain energy

Dominant effect of residual secondary phase of powders on Jc and microstructure of Bi-2212 superconducting wires

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superconductivity 2023年第4期8卷 1-8页

作者： l.H.Jin G.q.liu J.q.feng X.Y.Xu G.f.Jiao s.N.Zhang q.B.Hao P.X.Zhang C.s.l. superconducting Materials Research Center Northwest Institute for Nonferrous Metal ResearchShaanxiXi’an 710016China

Bi_(2)sr_(2)CaCu_(2)O_(8+δ)(Bi‐2212)superconducting round wires exhibited great potential for use in high‐field *** purity of the precursor powders is critical for the transport current of the ***,the role of the residual secondary phase in the precursor powders is not fully ***,the origin of the secondary phase was investigated in precursor powders that were prepared using ultrasonic spray pyrolysis(UsP)and calcination *** microstructure and phase evolution of the precursor powders during the crystallization process were ***,the effects that the residual secondary phase has on melting behavior,morphology properties,and the supercurrent flow of Bi‐2212 multi‐filamentary wires are systematically *** residual secondary phase in the filament caused further crystallization,and this.l.d to the formation of more and larger Bi‐2201 grains at the onset of the melting *** poor microstructure and low critical current of the final Bi‐2212 wires can be attributed to the presence of the residual copper‐rich ***‐2212 wires that were prepared with fully crystallized powders had a high critical current density(J_(c))of 6773 A/mm^(2) at 4.2 K,s.l.‐*** was revealed that control of the secondary phases in precursor powders is greatly significant for achieving superior values of J_(c).

关键词： superconductor Bi‐2212 wire Residual secondary phase Powder

fAsT Pulsar *** Profiles of 682 Pulsars

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Research in Astronomy and Astrophysics 2023年第10期23卷 71-175页

作者： P.f.wang J.l.Han J.Xu C.wang Y.Yan W.C.Jing W.q.su D.J.Zhou T.wang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China school of Astronomy University of Chinese Academy of SciencesBeijing 100049China

Pulsar polarization profiles form a very basic database for understanding the emission processes in a pulsar *** careful polarization calibration of the 19-beam l-band receiver and verification of beamoffset observation res.l.s,we obtain polarization profiles of 682 pulsars from observations by the five-hundredmeter Aperture spherical radio Telescope(fAsT)duringthe Galactic Plane Pulsar snapshot survey and other normal fAsT *** them,polarization profiles of about 460 pulsars are observed for the first *** profiles exhibit diverse *** pulsars have a polarization position angle curve with a good s-shaped swing,some with orthogonal modes;some have components with highly linearly polarized components or strong circularly polarized components;some have a very wide profile,coming from an aligned rotator,and some have an interpulse from a perpendicular rotator;some wide profiles are caused by interstellar *** derive geometric parameters for 190 pulsars from the s-shaped position angle curves or with orthogonal *** find that the linear and circular polarization or the widths of pulse profiles have various frequency *** with a large fraction of linear polarization are more likely to have a large Edot.

关键词： polarization (stars:)pulsars:general astronomical databases:miscellaneous