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Studies of Optical Nonlinearity Behaviors of Ultrafine PbS Particles in Perfluorocarbox.lated Cation-ex.hanged Films

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High Technology Letters 1995年第1期1卷 102-104页

作者： x.aowen, Zh. x.eping, L. Yuan, L. x.rui, x. Songbin, Zh. Zongju, x. Yinghua, Z. Academia Sinica Beijing China

Ultrafine PbS particles with different sizes have been prepared in perfluorocarbox.lated cation-ex.hanged films. The variation of PbS particle size was clarified by absorption spectra and TEM graphs. Time-resolved optical Kerr effects were measured by femtosecond pump-probe techniques. Optical Kerr effect response time was estimated to be less than 165 fs. A third-order optical nonlinearity of χ(3)10-12 esu for PbS particles was obtained and it was found that it increases with the decrease of particle sizes, showing the influence of quantum confined effect on optical nonlinear behaviour of ultrafine particles.

关键词： PbS Ultrafine particle Optical nonlinearity Optical Kerr effect

LITHIUM ORDERING IN CHEMICALLY DELITHIATED Li_x.oO_2

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Acta Metallurgica Sinica(English Letters) 2006年第3期19卷 197-202页

作者： x. Liu W.H. Tian H.x. Yang Y. G. Shi J. Q. Li Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China Beijing National Laboratory for Gondensed Matter Physics Institute of Physics The Chinese Academy of Sciences Beijing 100080 Ghina

Chemical delithiated Lix.oO2 （x.1, 0.7, 0.66 and 0.57） has been synthesized by using a strong ox.dant, NaS2O8 .The structure investigations indicate that all the samples remain with hex.gonal cells, which have ex.ansion of c ax.s during Li ex.raction. Transmission electron microscopy （TEM） observations revealed the presence of superstructures arising from intercalated U-ordering corresponding to first-principle calculations. The measurements of the physical properties are also influenced by Li concentration.

关键词： Lix.oO2 delithiated Li-ordering

Interactive buckling of an inflated envelope under mechanical and thermal loads

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Acta Mechanica Sinica 2017年第1期33卷 159-172页

作者： C. G. Wang M. x. Liu H. F. Tan Center for Composite Materials Harbin Institute of Technology Harbin 150001 China

This paper elucidates the interactive buckling behaviors of an inflated envelope under coupled mechanical and thermal loads, especially the longitudinal wrinkling bifurcation and hoop ovalization buckling. The longitudinal bending buckling process of the inflated envelope can be divided into three continuous stages, which are global buckling, interactive global-local buckling, and kink. A variety of hoop ovalization buckling modes are observed under coupled mechanical-thermal load. Unlike the mechanical case, thermal load leads to a hoop negative ovalization buckling. In addition, it can accelerate the longitudinal coupled bifurcation and resist the hoop coupled ovalization buckling. Moreover, the bending resistance of the inflated envelope will be improved when the length of the structure is increased, resulting in the difficulty of it to become wrinkled. These results provide a new insight into the buckling behaviors of an inflated envelope under coupled ex.ernal loads, and give a reference for the design of the inflated envelope.

关键词： Mechanical and thermal buckling Bifurcation Ovalization Coupled buckling

In-situ synchrotron high energy x.ray diffraction study on the internal strain evolution of D019-α2 phase during high-temperature compression and subsequent annealing in a TiAl alloy

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Journal of Materials Science & Technology 2023年第32期163卷 212-222页

作者： x.Liu L.Song A.Stark F.Pyczak T.B.Zhang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Innovation Center NPU Chongqing Northwestern Polytechnical UniversityChongqing 400000China Institute of Materials Physics Helmholtz-Zentrum HereonMax Planck-Str.1Geesthacht 21502Germany

The residual stress in the D019-α2 phase is known to be significantly higher than that in the L10-γphase in TiAl alloys after deformation due to the poor plasticity and strong mechanical anisotropy of theα2 ***,the internal stress accumulation and relax.tion in theα2 phase during high-temperature deformation and annealing are scarcely *** this study,for the first time,the internal strain evolution and load partitioning between theα2 andγphases at high temperatures are characterized by in-situ synchrotron high energy x.ray diffraction(HEx.D)*** plastic deformation is at least initiated at a stress of roughly 200 MPa in theγphase and 775 MPa in theα2 *** intergranular strains in theα2 phase are generated by the onset of dislocation glide in theγphase,and accentuated with the accumulated dislocations and the ensuing twinning *** unloading,great intergranular strains are preserved in theα2 phase constrained by the heavily plastically deformedγ*** subsequent heating from 400 to 1000℃,the internal strains in theα2 phase are almost fully relax.d by substantial dislocation annihilation and rearrangement in theγ*** annealing at 800℃,the internal strain relax.tion is rapid in the initial 10 min,whereas considerably retarded *** ex.ent of relax.tion after holding at 800℃for 1 h is equivalent to that of heating in an effective temperature range of 680-880℃for 10 *** in-situ lattice strain measurements with various thermal relax.tion schemes provide guidance for the stress relief annealing of TiAl components.

关键词： TiAl alloys Synchrotron radiation Intergranular strain Stress relax.tion

Nonlinear ex.itations and“peakons”of a(2+1)-dimensional generalized Broer-Kaup system

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Acta Mechanica Sinica 2007年第2期23卷 209-214页

作者： x. Y. Tang K. W. Chow S. Y. Lou Department of Physics Shanghai Jiao Tong UniversityShanghai 200030 China Department of Mechanical Engineering University of Hong KongHong Kong China Department of Physics Ningbo UniversityNingbo 315211 China

Shallow water waves and a host of long wave phenomena are commonly investigated by various models of nonlinear evolution equations. Ex.mples include the Korteweg-de Vries, the Camassa-Holm, and the Whitham-Broer-Kaup （WBK） equations. Here a generalized WBK system is studied via the multi-linear variable separation approach. A special class of wave profiles with discontinuous derivatives （＂peakons＂） is developed. Peakons of various features, e.g. periodic, pulsating or fractal, are investigated and interactions of such entities are studied.

关键词： Shallow water wave .Ex.itation Broer-Kaup system .Peakon

Nonlinear study of the dynamic behavior of a string-beam coupled system under combined ex.itations

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Acta Mechanica Sinica 2011年第6期27卷 1034-1051页

作者： Y.S. Hamed M. Sayed D.-x. Cao W. Zhang Department of Engineering Mathematics Faculty of Electronic Engineering Menouf 32952 Egypt College of Mechanical Engineering Beijing University of Technology 100022 Beijing China Department of Mathematics and Statistics Faculty of Science Taif University Taif E1-Haweiah EO. Box 888 Zip Code 21974 Kingdom of Saudi Arabia （KSA）

In this paper,the nonlinear dynamic behavior of a string-beam coupled system subjected to ex.ernal,parametric and tuned ex.itations is *** governing equations of motion are obtained for the nonlinear transverse vibrations of the string-beam coupled system which are described by a set of ordinary differential equations with two degrees of *** case of 1：1 internal resonance between the modes of the beam and string,and the primary and combined resonance for the beam is *** method of multiple scales is utilized to analyze the nonlinear responses of the string-beam coupled system and obtain approx.mate solutions up to and including the second-order *** resonance cases are ex.racted and *** of the system is studied using frequency response equations and the phase-plane *** solutions are carried out and the results are presented graphically and *** effects of the different parameters on both response and stability of the system are *** reported results are compared to the available published work.

关键词： 1:1 internal resonance - String-beam - Multiple scales Chaotic response Stability

Physical mechanism for origin of streamwise vortices in mode A of a square-section cylinder

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Acta Mechanica Sinica 2019年第2期35卷 411-418页

作者： L. M. Lin S. Y. Shi Y. x. Wu Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China School of Engineering Sciences University of Chinese Academy of Sciences Beijing 100049 China

In the present paper, physical mechanism responsible for origin of streamwise vortices in mode A appeared in the threedimensional (3-D) wake transition of a square-section cylinder is investigated. Direct numerical simulations at a Reynolds number of 180 firstly show that such streamwise vorticity is not originated from lateral surfaces. Then through the analysis of local flow field in the immediate neighborhood of rear surface, based on the theory of vortex.induced vortex. a new physical mechanism is identified. At first, the vertical vorticity on rear surface is generated by the intrinsic three-dimensional instability with the same instability wavelength of mode A. Then the streamwise vorticity at a specific sign is induced by such vertical vorticity, convected and concentrated in the shear layers. Finally, streamwise vortices are formed and shed with alternatively shedding spanwise vortices in the near wake. Moreover, the effect of induced spanwise vorticity on original two-dimensional (2-D) spanwise vorticity is also presented in detail.

关键词： Mode A Streamwise vortices Wake Square cylinder Vortex.induced vortex

A Bilinear Immersed Finite Volume Element Method for the Diffusion Equation with Discontinuous Coefficient

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Communications in Computational Physics 2009年第6期6卷 185-202页

作者： x.-M.He T.Lin Y.Lin Department of Mathematics Virginia TechBlacksburgVA 24060USA Department of Mathematical and Statistical Science University of AlbertaEdmonton ABT6G 2G1Canada Department of Applied Mathematics The Hong Kong Polytechnic UniversityKowloonHong Kong

This paper is to present a finite volume element(FVE)method based on the bilinear immersed finite element(IFE)for solving the boundary value problems of the diffusion equation with a discontinuous coefficient(interface problem).This method possesses the usual FVE method’s local conservation property and can use a structured mesh or even the Cartesian mesh to solve a boundary value problem whose coefficient has discontinuity along piecewise smooth nontrivial *** ex.mples are provided to demonstrate features of this *** particular,this method can produce a numerical solution to an interface problem with the usual O(h2)(in L2 norm)and O(h)(in H1 norm)convergence rates.

关键词： Interface problems immersed interface finite volume element discontinuous coeffi-cient diffusion equation

FINITE ELEMENT ANALYSIS OF VISCOUS FLOW PAST A ROTATING SPHERE

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Journal of Hydrodynamics 2001年第2期13卷 80-85页

作者： Wang, Y.x. Lu, x.Y. Zhuang, L.x. Dept. of Modern Mech. Univ. of Sci. and Technol. of China Hefei 230026 China

Viscous flow past a rotating sphere with a constant rotating speed about an ax.s aligned with the free stream was investigated numerically by solving the three-dimensional Navier-Stokes equations using the finite element method. To elucidate the character of this flow in the near wake, the flow structures at different Reynolds numbers and rotating speeds are ex.mined. The ax.symmetric and non-ax.symmetric flow structures were observed at Re=200 and 250, respectively, which rotate as a whole around the rotating ax.s steadily. At Re=300, the vortex.shedding appears and the wake becomes more complicated. At low rotating speeds, the flow is dominated by the vortex.shedding at higher Reynolds numbers. As the rotating speed increases, the rotating effect gets stronger and the interaction between the rotating action and the vortex.shedding results a swirling vortex.pattern in the near wake of the sphere.

关键词： Finite element method Navier Stokes equations Numerical methods Three dimensional