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Application of asymptotic waveform approximation technique to hybrid FE/Bi method for 3. scattering

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Science in China(Series F) 2007年第1期50卷 124-134页

作者： PENG Zhen1,2.3.& SHENG XinQing2.1 institute of Electronics, Chinese Academy of Sciences, {3. {2.0, China 2.{3. of Electronic Engineering, beijing institute of technology, {3. {2.1, China 3.Graduated University of Chinese Academy of Sciences, {3. 10003., China 1. institute of Electronics Chinese Academy of Sciences Beijing 100080 China 2. department of Electronic Engineering Beijing Institute of Technology Beijing 100081 China 3. Graduated University of Chinese Academy of Sciences Beijing 100039 China

The asymptotic waveform evaluation （AWE） technique is a rational function approximation method in computational mathemetics, which is used in many appllcations in computational electromagnetlca. in this paper, the performance of the AWE technique in conjunction with hybrid finite element/boundary integral （FE/Bi） method is firstly inveetlgeted. The formuletlon of the AWE applied in hybrid FE/Bi method is given in detail. The characteristic implementation of the application of the AWE to the hybrid FE/Bi method is discussed. Numarlcel results demonstrate that the AWE technique can greatly speed up the hybrid FE/Bi method to acquire wide-band and wide-angle backecatter radar-cross-section （RCS） by complex targets.

关键词： hybrid FE/Bi AWE electromagnetic scattering RCS

Void damage model and service life prediction for solid high polymer

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Chinese Science Bulletin 2001年第21期46卷 1842-1845页

作者： SHEN Tingfangdepartment of applied Physics,{2., {3. 100081, China department of applied Physics Beijing Institute of Technology Beijing China

Based on the analysis of three void damage variety models, this note presents (i) a method that regards the void content as a damage variation of the grain and (ii) a geometric model for micro-unit of void damage. Equations of the void damage variety containing void content are analyzed. This work is focused on the measurement of internal damage level and the damage variety estimation is directly related to the life predication in the practical engineering applications. Nowadays, the critical service life of the solid grain/polymers is usually presumed at domestic and international level. The strength or strain reduction of 2.% or the stabilizer consumption of 50% is generally regarded as a critical storage life of the solid grain/polymers, and the service life is predicted by the extrapolation method on An-henius formula. The applications, however, show that the above method is unreliable and has significant errors. With the aid of the discontiguous automatic measuring device of real time volume

关键词： void content void damage thermal aging service life damage mechanics.

Accuracy of Lax-Wendroff scheme for discontinuous solutions of convection equations

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Chinese Science Bulletin 1997年第24期42卷 2047-2051页

作者： DiNG Lijuandepartment of applied Mathematics,{2., {3. 100081, China department of applied Mathematics Beijing Institute of Technology Beijing China

iT is known from Brenner, Thomee and Wahlbin that the well-known second-order Lax-Wendroff scheme is stable in L^2. but unstable in L^p, p≠2. Generally speaking, if the initialdata is smooth enough and if a difference scheme, which is stable in L^p for some p, has orderof accuracy μ, then we can expect that the solution of the difference scheme converges to thesolution of the differential equation at the rate of order μ in L^p. But for discontinuous solu-tions, which are essential to hyperbolic equations, the above expectation is not true. Error es-timates for discontinuous solutions not only have theoretical meaning, but also practical value.

关键词： Lax-Wendroff scheme modlfled equation discontinuous solutions error estimate.

MD simulation of the effect of contact area and tip radius on nanoindentation

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Science China(Physics,mechanics & Astronomy) 2004年第1期47卷 101-112页

作者： CHEN Shangda1,2.& KE Fujiu1,2.1. department of {3. Physics, {2. University of Aeronautics and Astronautics, {2. 100083. China 2. State Key Laboratory of Non-linear mechanics (LNM), institute of mechanics, Chinese Academy of Sciences, {2. 100080, China Correspondence should be addressed to Chen Shangda (email: chensd@***) Received August 2., 2.03 1. department of applied Physics Beijing University of Aeronautics and Astronautics 100083 Beijing China 2. State Key Laboratory of Non-linear mechanics (LNM) Institute of Mechanics Chinese Academy of Sciences 100080 Beijing China

Molecular dynamics simulations of nanoindentation are performed on monocrystal copper. A new contact atoms method is presented for calculating the contact area. Compared with conventional methods, this method can provide the contact area more accurately not only for sink-in but also for pile-up situation. The effect of tip radius on indentation is investigated too. The results indicate that the measured hardness of the material will become higher as the tip radius increases.

关键词： nanoindentation, molecular dynamics, contact area, zero point of penetration depth, nano- hardness.

A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

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Science China Earth Sciences 2006年第12期49卷 1311-1322页

作者： HU Heping1, YE Baisheng2. ZHOU Yuhua3.& TiAN Fuqiang1 1. department of Hydraulic Engineering, Tsinghua University, beijing {2.4, China 2. Cold and Arid Regions Environmental and Engineering Research {3., Chinese Academy of Sciences, Lanzhou 73.000, China 3. department of Civil Engineering, Massachusetts {3. of technology, USA 1. department of Hydraulic Engineering Tsinghua University Beijing 100084 China 2. Cold and Arid Regions Environmental and Engineering Research institute Chinese Academy of Sciences Lanzhou 730000 China 3. department of Civil Engineering Massachusetts Institute of Technology USA

Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth and atmosphere, human impacts on the environment and eco- system, etc. Soil freeze/thaw plays an important role in cold land surface processes. in this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied. A sophisti- cated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil, but also demon- strates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model is applied to analyze the diurnal energy and water cycle char- acteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.

关键词： land surface model,soil freeze/thaw,GAME/Tibet,simultaneous liquid,vapor and heat transfer.

Weighted estimates for the multilinear singular integral operators with non-smooth kernels

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Science China Mathematics 2011年第3期54卷 587-602页

作者： HU GuoEn1 & LU ShanZhen2.1department of applied Mathematics, Zhengzhou information Science and {2. {3., Zhengzhou 450002. China 2.0} of Mathematics, beijing Normal University, beijing 100875, China 1. department of applied Mathematics Zhengzhou Information Science and Technology Institute Zhengzhou 450002 China2. Department of Mathematics Beijing Normal University Beijing 100875 China

in this paper, by sharp function estimates and certain weak type endpoint estimates, the authors establish some weighted norm inequalities with Ap weights for the multilinear singular integral operators with non-smoot... 详细信息

关键词： approximation to the identity weighted norm inequality singular integral operator non-smooth kernel Calderón-Zygmund decomposition

On exactness and unbiasedness of confidence bands for a continuous distribution function

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