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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.{2. 2. Department of Building Engineering, Xi’an University of Technology, Xi’an 710048,{2. Shanghai institute of Applied Mathematics and mechanics Shanghai University Shanghai China Department of Building Engineering Xi’an University of Technology Xi’an 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.

Study of thin cloud removal method for CBERS-02.image

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Science china(Technological Sciences) 2005年第S2期48卷 91-99页

作者： MA Jianwen1, GU Xingfa1, FENG Chun2.& GUO Jianning2.1. institute of Remote Sensing Application, Chinese Academy of Sciences, beijing 100101,{2. 2.{2. Center for Resource Satellite Data and Applications, beijing 100073,{2. institute of Remote Sensing Application Chinese Academy of Sciences Beijing 100101 China china Center for Resource Satellite Data and Applications Beijing 100073 China

The china Brazil Earth Resources Satellite (CBERS) ended the dependence on foreign satellites. Along with the series of CBERS and the enhancement of satellite applications, it is necessary to search correlative data processing methods. Because cloud appears in the atmosphere, an image with clear sky conditions is often hard to obtain. How to remove cloud is an important sector of increasing image quality. An improved homomorphism filtering method is adopted to remove thin cloud qualitatively at first, and all bands are selected to classify pixels. Based on the fact that visible band images contain more aerosol effects than infrared bands, visible bands are used to determine clear or hazy regions and the reflectances of different surface classes in clear regions are calculated. At last the mean reflectance of the same classes in clear and hazy regions is matched to remove cloud. The image visual effect is improved; meanwhile, the ground reflectance is retrieved to meet the needs of remote sensing quantification.

关键词： CBERS-02 cloud removal surface reflectance mean reflectance matching.

Plus cupping degrees do not form an ideal

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Science in china(Series F) 2004年第5期47卷 635-654页

作者： LI Angsheng1,2.& ZHAO Yicheng1 1. institute of Software,Chinese Academy of Sciences,beijing {2.,china 2. School of Information Sciences,beijing Normal University,beijing 100871,china institute of Software Chinese Academy of Sciences Beijing China School of Information Sciences Beijing Normal University Beijing China

A computably enumerable (c.e.,for short)degree a is called plus cupping,if every c.e. degree x with 0 详细信息

A computably enumerable (c.e.,for short)degree a is called plus cupping,if every c.e. degree x with 0

关键词： computably enumerable set Turing degree definability.

Evaluation of the Interfacial Adhesion between Brittle Coating and Ductile Substrate by Cross-Sectional Indention

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材料热处理学报 2004年第5B期25卷 1187-1190页

作者： SUJian-yu ZHANGKun CHENGuang-nan instituteofmechanics ChineseAcademyofSciencesBeijingChina／／GraduateSchooloftheChineseAcademyofSciencesBeijingChina instituteofmechanics ChineseAcademyofSciencesBeijingChina

The cross-sectional indentation method is extended to evaluate the interfacial adhesion between brittle coating and ductile substrate. The experimental results on electroplated chromium coating/steel substrate show that the interfacial separation occurs due to the edge chipping of brittle coating. The corresponding models are established to elucidate interfacial separation processes. This work further highlights the advantages and potential of this novel indentation method.

关键词：分界面附着刻痕可锻衬底应力涂层铬钢

Solving the input data in error correc-tion of optical fabrication by finite Fourier coefficient algorithm

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Science china(Technological Sciences) 2006年第1期49卷 50-60页

作者： CHENG Haobo1,2. SUN Guozheng3 & FENG Zhijing2.1. Department of Optical Engineering, beijing institute of Technology, beijing 100081, china 2. Department of Precision Instruments and Mechanology, Tsinghua University, beijing 100084, china 3. china North Industries Group Corporation, beijing 100089, china Department of Optical Engineering Beijing Institute of Technology Beijing China Department of Precision Instruments and Mechanology Tsinghua University Beijing China china North Industries Group Corporation Beijing China

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influ-ence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

关键词： optical fabrication, computer controlled optical surfacing, free-form lens, finite Fourier coefficient, error correction.

A new DNA algorithm to solve graph coloring problem

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Progress in Natural Science:Materials International 2007年第6期17卷 733-738页

作者： Jiang Xingpeng1, Li Yin2. Meng Ya3 and Meng Dazhi2.1. National Laboratory of Pattern Recognition,institute of Automation, Chinese Academy of Sciences, beijing 1.0080,{2. 2. College of Applied Sciences, beijing University of Technology, beijing 10002.,{2. 3. School of Science, beijing institute of Technology, beijing 100081,{2.) National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Beijing 100080 China College of Applied Sciences Beijing University of Technology Beijing 100022 China School of Science Beijing Institute of Technology Beijing 100081 China

Using a small quantity of DNA molecules and little experimental time to solve complex problems successfully is a goal of DNA computing. Some NP-hard problems have been solved by DNA computing with lower time complexity than conventional computing. However, this advantage often brings higher space complexity and needs a large number of DNA encoding molecules. One example is graph coloring problem. Current DNA algorithms need exponentially increasing DNA encoding strands with the growing of problem size. Here we propose a new DNA algorithm of graph coloring problem based on the proof of four-color theorem. This algorithm has good properties of needing a relatively small number of operations in polynomial time and needing a small number of DNA encoding molecules (we need only 6R DNA encoding molecules if the number of regions in a graph is R).

关键词： DNA computing NP-hard problem graph coloring problem.

Case studies on mesoscale structures of heavy rainfall system in the Yangtze River generated by Meiyu front

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Science china Earth Sciences 2005年第8期48卷 1303-1311页

作者： LIU Liping1, RUAN Zheng1 & QIN Danyu2.1. Chinese Academy of Meteorological Sciences, beijing 100081, china 2. Nanjing {2. of Meteorology, Nanjing 2.0044, china Chinese Academy of Meteorological Sciences Beijing China Nanjing institute of Meteorology Nanjing China

A heavy rainfall system was observed over the Yangtze River during Meiyu season by using dual-Doppler radar systems in the field experiment conducted by the project of National Fundamental Research Planning “Research on formation mechanism and the prediction theory of hazardous weather over china”. The three-dimensional mesoscale kinematic structure and process of a heavy rain on 2. and 2. July, 2.02.are investigated by using the radial velocity and dual-Doppler radar technique. The results show that a southwest-northeast oriented rain band with the length of about 1000 km involves numbers of meso-β or meso-γ-scale convective cells with the size of 2.―50 km. The heavy rain band in the middle reaches of the Yangtze River ex-ists in a low-level wind shear. The interaction between southwest low-level jet on the southern side of wind shear and east wind on the northern side formed the updraft. The wind disturbance, wind shear and convergence generate the convective action. The new cell developed in right rear flank of rain band and moved to the southwest wind area, where the vapor is abundant. This kind of echo can last a long time and developed well. The strong convective echoes are often ac-companied by the meso-γ-scale vortex and convergence.

关键词： heavy rainfall in Meiyu front, mesoscale structure, dual-Doppler radar, middle reaches of the Yangtze River, low-level jet.

Integrative inversion of land surface component temperature

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Science china Earth Sciences 2005年第11期48卷 2011-2019页

作者： FAN Wenjie1 & XU Xiru1,2.1. institute of Remote Sensing and Geographical Information System, Peking University, beijing 100871,{2. 2. Center of Remote Sensing and GIS of beijing Normal University, beijing 100875,{2. institute of Remote Sensing and Geographical Information System Peking University Beijing China Center of Remote Sensing and GIS of beijing Normal University Beijing China

In this paper, the row winter wheat was selected as the example to study the com-ponent temperature inversion method of land surface target in detail. The result showed that the structural pattern of row crop can affect the inversion precision of component temperature evi-dently. Choosing appropriate structural pattern of row crop can improve the inversion precision significantly. The iterative method combining inverse matrix was a stable method that was fit for inversing component temperature of land surface target. The result of simulation and field ex-periment showed that the integrative method could remarkably improve the inversion accuracy of the lighted soil surface temperature and the top layer canopy temperature, and enhance inver-sion stability of components temperature. Just two parameters were sufficient for accurate at-mospheric correction of multi-angle and multi-spectral thermal infrared data: atmospheric trans-mittance and the atmospheric upwelling radiance. If the atmospheric parameters and component temperature can be inversed synchronously, the really and truly accurate atmospheric correction can be achieved. The validation using ATSRII data showed that the method was useful.

关键词： components temperature, inverse pattern, atmospheric correction

Lie symmetries of mechanical systems with unilateral holonomic constraints

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Chinese Science Bulletin 2000年第15期45卷 1354-1358页

作者： ZHANG Yi & MEI Fengxiang1. Department of Basic Courses, Suzhou institute of Urban Construction & Environmental Protection, Suzhou 2.5011, china 2. Department of Applied {2., beijing institute of Technology, beijing 10008I, china Department of Basic Courses Suzhou Institute of Urban Construction & Environmental Protection Suzhou China Department of Applied mechanics Beijing Institute of Technology Beijing China

In the recent twenty years, the study on the Lie symmetries and conserved quantities of constrained mechanical systems has been making great progress[1-5]. Up to now, however, all the studies are limited to the mechanical systems with ideal bilateral constraints. This note further studies the Lie symmetries of mechanical systems with unilateral holonomic constraints, and two problems of Lie symmetries for the systems are put forward and solved, i.e. finding the conserved quantity from a Lie symmetric transformation of the system and finding the corresponding Liesymmetry from an integral of the systemi ? 梛 ? Jsymmetry from an integral of the system.

关键词： analytical mechanics unilateral constraint holonomic system Lie symmetry conserved quantity.