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MESHLESS METHOD FOR 2D MIXED-MODE CRACK PROPAGATION BASED ON VORONOI CELL

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Acta Mechanica Solida Sinica 2003年第3期16卷 231-239页

作者： Lou Luliang Zeng Pan (department of Mechanical Engineering,tsinghua university,beijing 100084,China) department of Mechanical Engineering Tsinghua University Beijing 100084 China

A meshless method integrated with linear elastic fracture mechanics(LEFM)is presented for 2D mixed-mode crack propagation *** domain is divided automatically into sub-domains based on Voronoi cells,which are used for quadrature for the potential energy. The continuous crack propagation is simulated with an incremental crack-extension method which assumes a piecewise linear discretization of the unknown crack *** each increment of the crack extension,the meshless method is applied to carry out a stress analysis of the cracked *** J-integral,which can be decomposed into mode Ⅰ and mode Ⅱ for mixed-mode crack,is used for the evaluation of the stress intensity factors(SIFs).The crack-propagation direction,predicted on an incremental basis, is computed by a criterion defined in terms of the SIFs. The flowchart of the proposed procedure is presented and two numerical problems are analyzed with this *** meshless results agree well with the experimental ones,which validates the accuracy and efficiency of the method.

关键词： meshless method crack propagation mixed-mode crack Voronoi cell

Timing in the Time Domain: Cygnus X-1

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Chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 313-332页

作者： Ti-Pei Li (department of Physics and Center for Astrophysics, tsinghua university, beijing 100084 High Energy Astrophysics Lab., Institute of High Energy Physics, Chinese Academy of sciences, beijing 100039)E-mail:litp@*** department of Physics and Center for Astrophysics Tsinghua University High Energy Astrophysics Lab. Institute of High Energy Physics Chinese Academy of Sciences

Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.

关键词： methods: data analysis - stars: individual (Cygnus X-1) - X-rays: stars

Electrophysiological research of synapse formation from beginning to maturity

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Chinese Science Bulletin 1998年第1期43卷 55-59页

作者： XIE Zuoping and ZHENG Yufang State Key Laboratory of Biomembrane and Membrane Biotechnique department of Biological sciences and Biotechnology, tsinghua university, beijing 100084, China State Key Laboratory of Biomembrane and Membrane Biotechnique Tsinghua University Beijing China department of Biological sciences and Biotechnology Tsinghua University Beijing China

The development of synapses is an important question in neurobiology. We employ patchclamp technique to record MEPCs and EPCs of myoballs in Xenopus cell culture. The rate of EPC/MEPC is related with synapses maturation. Accordingly, we define the mature synapses as those whose rate of presynaptic membrane’s EPC to MEPC is more than 8. The process of maturation needs about 2-5.h after neurites contact with myoballs. We divide the development of synapses into three stages: young, developing and mature. The neurotransmitters stack gradually and increase by hundreds of times along with young synapses growing into maturity. So the process of synapses maturation should include presynaptic membrane specialization, postsynaptic membrane specialization and neurotransmitters stack.

关键词： definition of mature synapse α latrotoxin (α LTX) neurotransmitter stack.

CONVERGENCE OF CHORIN-MARSDEN FOR MULA FOR THENAVIER-STOKES EQUATIONS ON CONVEX DOMAINS

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Journal of Computational Mathematics 1999年第1期17卷 73-88页

作者： Lung-an Ying(Research institute for mathematical sciences, Kyoto university, Japan department of Mathematics, Peking university, {5. 100871, China) 北京大学数学系北京

We prove the convergence of the Chorin-Marsden product formula for solving the initial-boundary value problems of the Navier-Stokes equations on convex domains. As a particular case we consider the case of the half pl... 详细信息

关键词： Navier Stokes equation vortex method fractional step method convergence

|m| Partial wave treatment for two-dimensional Coulomb-scattering and Regge pole

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Science China(Physics,Mechanics & Astronomy) 2004年第6期47卷 676-684页

作者： WANG Jing & ZENG Jinyan department of Physics,tsinghua university,beijing 100084,China School of Physics,Peking university,beijing 100871,China department of Physics Tsinghua University Beijing 100084 China School of Physics Peking University Beijing 100871 China

The symmetry and |m| partial-wave analysis for two-dimensional (2D) Coulomb-scattering is investigated. As a function of energyE, the |m| partial-wave scattering amplitudef |m|(θ) is analytically continuated to the, negativeE (complexk) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles off |m|(θ) on the positive imaginaryk axis as is expected. In addition, as a function of |m|,f |m|(θ) is analytically continuated to the complex |m| plane, the bound state energy eigenvalues are just located at the poles off |m|(θ) on the positive real |m| axis.

关键词： two-dimensional Coulomb scattering, |m| partial-wave, Regge pole.

Multiparty quantum secret sharing of classical and quantum messages

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Progress in Natural Science:Materials International 2007年第1期17卷 26-31页

作者： CHEN Pan, DENG Fuguo and LONG Guilu ( Key Laboratory for Quantum Information and Measurements, and department of Physics, tsinghua university, beijing 100084, China Key Laboratory of Beam Technology and Material Modification, MOE, Institute of Low Energy Nuclear Physics, and department of Material Science and Engineering, beijing Normal {5., beijing 100875. China beijing Radiation Center, beijing 100875. China Key Laboratory for Atomic and Molecular Nano-sciences, tsinghua university, beijing 100084, China) Key Laboratory for Quantum Information and Measurements and Department of Physics Tsinghua University Beijing 100084 China Key Laboratory of Beam Technology and Material Modification MOE Institute of Low Energy Nuclear Physics and Department of Material Science and Engineering Beijing Normal University Beijing 100875 China beijing Radiation Center Beijing 100875 China Key Laboratory for Atomic and Molecular Nano-sciences Tsinghua University Beijing 100084 China

A scheme for multiparty quantum secret sharing of classical and quantum messages is proposed by using entanglement swapping. This scheme can distribute not only the classical information but also the quantum informati... 详细信息

关键词： quantum secret sharing classical message quantum message EPR pair.

THE NAGUMO EQUATION ON SELF-SIMILAR FRACTAL SETS

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Chinese Annals of Mathematics,Series B 2002年第4期23卷 519-530页

作者： HU JIAXINdepartment of Mathematics, tsinghua university, beijing 100084, China. department of Mathematics Tsinghua University Beijing 100084 China

The Nagumo equation ut = △u+ bu(u-a)(1-u), t＞0is investigated with initial data and zero Neumann boundary conditions on post-critically finite (p.c.f.) self-similar fractals that have regular harmonic structures and satisfy the separation condition. Such a nonlinear diffusion equation has no travelling wave solutions because of the 'pathological' property of the fractal. However, it is shown that a global Holder continuous solution in spatial variables exists on the fractal considered. The Sobolev-type inequality plays a crucial role, which holds on such a class of p.c.f self-similar fractals. The heat kernel has an eigenfunction expansion and is well-defined due to a Weyl's formula. The large time asymptotic behavior of the solution is discussed, and the solution tends exponentially to the equilibrium state of the Nagumo equation as time tends to infinity if b is small.

关键词： Fractal set Spectral dimension Sobolev-type inequality Strong (Weak) solution

Closed and endoreversible chemical oscillation

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Chinese Journal of Chemistry 1994年第3期12卷 199-205页

作者： LI, Ru-Shengdepartment of Chemistry, tsinghua university, beijing 100084, China department of Chemistry Tsinghua University Beijing 100084 China

Based on a simple nonideal chemical reaction model, the closed system with reversible nonideal reactions and illumination is shown to be able to exhibit sustained oscillation. The essential points in the occurrence of such oscillations are the nonideality of reacting media, which gives rise to multiple chemical equilibria, and the energy flow through illumination and heat conduction, which gives rise to spontaneous transitions repeatedly between the multiple equilibrium states. During the oscillation, reacting media undergo only reversible chemical transformation and all irreversibilities are restricted to the coupling of the system to external world. This oscillation provides an example of the so-called endoreversible machine and a possible way to convert radiation energy of the light directly into mechanical energy.

关键词： Chemical oscillation closed system nonideality endoreversible machine illumination.

Fractal Characteristics of Round Jets in Steady Crossflow

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Communications in Nonlinear Science and Numerical Simulation 1998年第3期3卷 183-186页

作者： Yuhang LI Chaoquan CHEN and Chunbo JIANG(Hydraulic department, tsinghua university, beijing 100084, China) Hydraulic department Tsinghua University Beijing 100084 China

The fractal dimensions of turbulent round jets in steady crossflow has beenanalyzed by using planar laser-induced fluorescence (PLIF) method. The relation betweenthe fractal dimension and the momentum ratio, the variation of the fractal dimension withthe elevation of jet and the dilution have been investigated. The comparison of the fractalcharacteristics between the multiple jets and the signal jet has been carried out.

关键词： steady crossflow turbulent jet measurement of fractal dimension