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Monte Carlo calculation method on low energy electronscattering in polybasic medium

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Chinese science Bulletin 1998年第2期43卷 171-174页

作者： TAN Zhenyu 1 and HE Yancai 2.1. College of Electric Power, shandong University of Technology, Jinan 2.0061, China 2. shanghai institute of ceramics, Chinese Academy of sciences, shanghai 2.0050, China College of Electric Power Shandong University of Technology Jinan China shanghai institute of{2. Chinese Academy of Sciences Shanghai China

A novel Monte Carlo method of simulating low energy electron (LEE) scattering in polybasic medium is presented. The Mott cross section is adopted to describe the elastic scattering of LEE, and a mean cross section idea is proposed instead of usual determination of the scattering center. The Joy’’s modified Bethe equation is used to calculate energy loss of LEE. The scattering processes of LEE in bulk PMMA have been simulated. And the electron backscattering coefficients, the electron interaction range and energy dissipation distribution of LEE in bulk PMMA have been calculated and compared with those calculated by the method of determining scattering center.

关键词： low_energy electron scattering Monte Carlo method cross_section.

Boundary element-free method for elastodynamics

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science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 641-657页

作者： CHENG Yumin1 & PENG Miaojuan2.1. shanghai institute of Applied Mathematics and Mechanics, shanghai University, shanghai 2.0072. China 2. Department of Civil Engineering, shanghai University, shanghai 2.0072. China 1. shanghai institute of Applied Mathematics and Mechanics Shanghai University 200072 Shanghai China 2. Department of Civil Engineering Shanghai University 200072 Shanghai China

The moving least-square approximation is discussed first. sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.

关键词： moving least-square approximation, improved moving least-square approximation, elastodynamics, boundary integral equation, meshless method, boundary element-free method, Fourier eigen transform.

Transverse patterns and spatiotemporal instability of a photorefractive oscillator

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Chinese science Bulletin 1997年第9期42卷 724-729页

作者： ZHUANG Jun and TAN Weihan1. shanghai institute of Optics and Fine Mechanics, Chinese Academy of sciences, shanghai 2.1800, China 2. shanghai University, shanghai 2.1800, China shanghai institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai China shanghai University Shanghai China

IN time realm,instability and chaos phenomena of a nonlinear optical system have been dis-cussed *** recent years,as much interest was attracted to the transverse ef-fects in nonlinear optics,the study was developed t... 详细信息

关键词： photorefractive oscillator spatiotemporal instability transverse patterns.

A complex variable meshless method for fracture problems

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science China(Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1 & LI Jiuhong2.1. shanghai institute of Applied Mathematics and Mechanics, shanghai University, shanghai 2.0072. China 2. Department of Building Engineering, Xi’an University of Technology, Xi’an 710048, China shanghai institute of Applied Mathematics Mechanics Shanghai University Shanghai 200072 China Department of Building Engineering Xi’an University of Technology Xi’an 710048 China

Based on the moving least-square (MLs) approximation, the complex variable moving least-square approximation (CVMLs) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.

Gas hydrate fast nucleation from melting ice and quiescent growth along vertical heat transfer tube

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science China Chemistry 2005年第1期48卷 75-82页

作者： XIE Yingming1,2. GUO Kaihua2. LIANG Deqing2. FAN shuanshi2. GU Jianming1 & CHEN Jinggui2.1. institute of Refrigeration and Cryogenics, shanghai Jiaotong University, shanghai 2.0030, China 2. Guangzhou institute of Energy Conversion, The Chinese Academy of sciences, Guangzhou 510640, China 1. institute of Refrigeration and Cryogenics Shanghai Jiaotong University 200030 Shanghai China 2. Guangzhou institute of Energy Conversion The Chinese Academy of Sciences 510640 Guangzhou China

During the observation of HCFC141b gas hydrate growth processes outside a ver- tical heat transfer tube, two exciting phenomena were found: fast nucleation of gas hydrate from melting ice, and the spontaneous permeation of water into the guest phases along the surface of heat transfer tube to form gas hydrate continuously. These two phenomena were explained with Zhou & sloan’s hypothesis and the theory of surface free energy respectively, and a novel method of gas hydrate formation was presented——gas hydrate fast nucleation from melting ice and quiescent growth along heat transfer tube. There is no mechanic stirring in this method, the formed gas hydrates are compact, the ratio of unreacted interstitial water is little, which overcome the drawback of high energy cost and high ratio of unreacted interstitial water among the formed gas hydrates in the system with mechanic stirring. This finding will benefit the gas hydrate ap- plication technologies such as natural gas storage technology or cool storage technology with gas hydrate.

关键词： gas hydrate, natural gas storage, cool storage, fast nucleation from melting ice, permeation, surface free energy.

Chinese Jingdezhen blue and white imperial porcelain

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science China(Technological sciences) 2004年第3期47卷 366-375页

作者： WU Juan1, LI Jiazhi1, DENG Zequn1 & WANG Changsui2.1. Laboratory of Ancient ceramics, shanghai{2. of ceramics, Chinese Academy of sciences, shanghai 2.0050, China 2. Department of History of science and Archaeometry, University of science and Technology of China, Hefei 2.002., China Chinese Acad sci Shanghai Inst Ceram Lab Ancient Ceram Shanghai 200050 Peoples R China Univ sci & Technol China Dept Hist Sci Archaeometry Hefei 230026 Peoples R China

Jingdezhen blue and white imperial porcelain specimens from the Yuan, Ming and Qing dynasties have been systematically analyzed using a nondestructive test method—— energy dispersive X-ray fluorescence analysis (EDXRF). The derived data of major and trace element compositions have been treated by correspondence analysis. The variation laws of the composition patterns for Jingdezhen blue and white imperial porcelain in different historical periods owing to the change in raw materials, recipe and technology have been discussed, and a time model related to variation of element composition has been preliminarily established, It would be helpful for scientific dating of Jingdezhen blue and white imperial porcelain, and even for the studies on the whole field of identification of ancient ceramics.

关键词： energy dispersive X-ray fluorescence analysis, blue and white imperial porcelain, correspondence analysis.

Origin of Chinese ancient glasses——study on the earliest Chinese ancient glasses

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science China Technological sciences 2006年第6期49卷 701-713页

作者： GAN Fuxi1,2. CHENG Huansheng1 & LI Qinghui2.1. Fudan University, 2.0 Handan Road, shanghai 2.0433, China 2. shanghai{2. of Optics and Fine Mechanics, CAs, P.O. Box 800-2.1, shanghai 2.1800, China Fudan University 220 Handan Road Shanghai 200433 China shanghai institute of Optics Fine Mechanics CAS P.O. Box 800-211 Shanghai 201800 China

The earliest Chinese ancient glasses before the West Han Dynasty (2.0 BC) from different regions are studied. The glass samples were unearthed from Hunan, Hubei, Yunnan, sichuan, Guizhou, Guangdong and Xinjiang of China. The chemical composition of these glasses samples is analyzed by proton induced X-ray emission (PIXE) technique, energy dispersive X-ray fluorescence (EDXRF) method and inductively coupled plasma atomic emission spectrometry (ICP-AEs). It is shown that the glass chemical compositions belong to barium-lead silicate BaO-PbO-siO2. potash soda lime silicate K2. (Na2.)-CaO-siO2.(K2./Na2.>1), soda potash lime silicate Na2. (K2.)-CaO-siO2.(K2./Na2.sh silicate K2.-siO2.glass systems, respectively. The origins of the earliest Chinese ancient glasses are discussed from the archaeological and historical points of view. These four types of Chinese ancient glasses were all made in Chinese territory using local raw materials. The glass preparation technology was related to the Chinese ancient bronze metallurgy and protoporcelain glaze technology. The glass technology relationship between the East and the West is analyzed at the same time.

关键词： ancient glass glass origin chemical composition analysis.

steady-state responses of axially accelerating viscoelastic beams: Approximate analysis and numerical confirmation

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science China(Physics,Mechanics & Astronomy) 2008年第11期51卷 1707-1721页

作者： CHEN LiQun1,2.& DING Hu2.1 Department of Mechanics, shanghai University, shanghai 2.0444, China 2.shanghai institute of Applied Mathematics and Mechanics, shanghai 2.0070, China Department of Mechanics Shanghai University Shanghai 200444 China shanghai institute of Applied Mathematics and Mechanics Shanghai 200070 China

Nonlinear parametric vibration of axially accelerating viscoelastic beams is inves-tigated via an approximate analytical method with numerical confirmations. Based on nonlinear models of a finite-small-stretching slender beam moving at a speed with a periodic fluctuation, a solvability condition is established via the method of multiple scales for subharmonic resonance. Therefore, the amplitudes of steady-state periodic responses and their existence conditions are derived. The amplitudes of stable steady-state responses increase with the amplitude of the axial speed fluctuation, and decrease with the viscosity coefficient and the nonlinear coefficient. The minimum of the detuning parameter which causes the existence of a stable steady-state periodic response decreases with the amplitude of the axial speed fluctuation, and increases with the viscosity coefficient. Nu-merical solutions are sought via the finite difference scheme for a nonlinear par-tial-differential equation and a nonlinear integro-partial-differential equation. The calculation results qualitatively confirm the effects of the related parameters pre-dicted by the approximate analysis on the amplitude and the existence condition of the stable steady-state periodic responses. Quantitative comparisons demonstrate that the approximate analysis results have rather high precision.

关键词： nonlinearity parametric vibration axially accelerating beam method of multiple scales numerical confir-mation

Fredholm operators in Toeplitz algebras associated with discrete abelian groups

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Chinese science Bulletin 1998年第14期43卷 1175-1179页

作者： XU Qingxiang 1 and CHEN Xiaoman 2.1. Department of Mathematics, shanghai Normal University, shanghai 2.02.4, China 2. Laboratory of Mathematics for Nonlinear sciences and{2. of Mathematics, Fudan University, shanghai 2.0433, China Department of Mathematics Shanghai Normal University Shanghai China Laboratory of Mathematics for Nonlinear sciences and institute of Mathematics Fudan University Shanghai China

The locally finite below sets are introduced and the Fredholm operators in Toeplitz algebras associated with discrete abelian groups are studied.

关键词： discrete abelian group quasi_ordered group Toeplitz operator Fredholm operator.