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Parameter identification theory of a complex model based on global optimization method

Science china(physics,Mechanics & Astronomy) 2008年第11期51卷 1722-1732页

作者： QU Jie1, JIN QuanLin2 & XU BingYe3 1 College of Automotive Engineering, South china university of Technology, Guangzhou 510640, china 2 beijing Research Institute of Mechanical and Electrical Technology, beijing 100083, china 3 department of Engineering Mechanics, tsinghua university, beijing 100084, china 1. College of Automotive Engineering South China University of Technology Guangzhou 510640 China 2. beijing Research Institute of Mechanical and Electrical Technology Beijing 100083 China 3. department of Engineering Mechanics Tsinghua University Beijing 100084 China

With the development of computer technology and numerical simulation technology, computer aided engineering (CAE) technology has been widely applied to many fields. One of the main obstacles, which hinder the further application of CAE technology, is how to successfully identify the parameters of the selected model. An elementary framework for parameter identification of a complex model is provided in this paper. The framework includes the construction of objective function, the design of the optimization method and the evaluation of the identified results, etc. The parameter identification process is described in this framework, taking the parameter identification of the superplastic constitutive model considering grain growth for Ti-6Al-4V at 927°C as an example. The objective function is the weighted quadratic sums of the difference between the experimental and computational data for the stress-strain relationship and the grain growth relationship; the designed optimization method is a hybrid global optimization method, which is based on the feature of the objective function and incorporates the strengths of genetic algorithm (GA), the Levenberg-Marquardt algorithm and the augmented Gauss-Newton algorithm. The reliability evaluation of parameter identification result is made through the comparison between the calculated and experimental results and between the theoretical values of the parameters and the identified ones.

关键词： constitutive model parameter identification theory inverse analysis global optimization

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Simulation of freezing and melting of soil on the northeast Tibetan Plateau

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Chinese Science Bulletin 2011年第20期56卷 2145-2155页

作者： XIA Kun 1,2,3,LUO Yong 2,4,5 & LI WeiPing 2 1 Institute of Atmospheric physics,Chinese Academy of Sciences,beijing 100029,china 2National Climate center,china Meteorological Administration,beijing 100081,china 3Graduate university of Chinese Academy of Sciences,beijing 100049,china 4 center for Earth System Science,tsinghua university,beijing 100084,china 5Key Laboratory of Earth System Numerical Simulation,Ministry of Education,beijing 100084,china Institute of Atmospheric physics Chinese Academy of Sciences National Climate center China Meteorological Administration Graduate university of Chinese Academy of Sciences center for Earth System Science Tsinghua University Key Laboratory of Earth

Using observational data spanning the period from February to December 2009 and recorded at the Suli station in Qinghai Province,the land-surface model CLM3.0 was employed to simulate the freezing and melting of *** results indicate that the simulated soil temperature is higher than the observed soil temperature and the ultimate thawing date is earlier than the observed date during the melting *** the freezing period,the simulated soil temperature is lower than the observed soil temperature and the ultimate freezing of the deep soil is earlier than that ***,the simulation of freezing is better than that of melting,and the simulation of a shallow layer is better than that of a deeper *** the original CLM3.0,it is assumed that frozen soil begins to melt when the soil temperature exceeds 0C,which is inconsistent with *** critical freeze-thaw temperature was calculated according to thermodynamics equations and the freeze-thaw condition was *** this work,the melting rate for frozen soil was reduced using the modified scheme,and the simulated soil temperature was lowered. Meanwhile,the refreezing of soil during the melting season was well simulated and more closely matched ***,it was found that the rates of melting and freezing differ,with the former being slower than the latter,but refreezing during the melting season is rather quick.

关键词：土壤温度冻结期青藏高原东北部模拟融化观测数据热力学方程表面模型

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Wave decomposition phenomenon and spectrum evolution over submerged bars

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Acta Oceanologica Sinica 2009年第3期28卷 82-92页

作者： LI Benxia YU Xiping National Marine Environmental Forecasting center State Oceanic Administration Beijing 100081China department of Hydraulic Engineering Tsinghua University Beijing 100084 China

Wave decomposition phenomenon and spectrum evolution over submerged bars are investigated by a previously developed numerical model. First, the computed free surface displacements of regular waves at various locations are compared with the available experimental data to confirm the validity of the numerical model, and satisfactory agreements are obtained. In addition, variations of decomposition characteristics with incident wave parameters and the change of energy spectrum for regular waves are also studied. Then the spectrum evolution of irregular waves over submerged bars, as well as the influence of incident peak wave period and the steepness of the front slope of the bar on spectrum evolution, is investigated. Wave decomposition and spectral shape are found to be significantly influenced by the incident wave conditions. When the upslope of the bar becomes 1：2, the length of the slope becomes shorter and will not benefit the generation of high frequency energy, so spectrum evolution is not significant.

关键词： wave decomposition spectrum evolution nonlinear waves irregular waves submerged bars

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Fluorescence fluctuation spectroscopy and its artifacts:simulations and tests

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Science china(physics,Mechanics & Astronomy) 2005年第3期48卷 336-344页

作者： MENG Fanbo 1 , CHEN Bo 1 , LIU Guang 1 , DING Jianying 1 & MA Hui 2,1 1. department of physics and Key Laboratory of Atomic and Molecular Nano Sciences, Ministry of Educa- tion, tsinghua university, beijing 100084, china 2. Graduate School at Shenzhen, tsinghua university, Shenzhen 518055, china 1. department of physics and Key Laboratory of Atomic and Molecular Nano Sciences Ministry of Education Tsinghua University 100084 Beijing China 2. Graduate School at Shenzhen Tsinghua University 518055 Shenzhen China

Fluorescence fluctuation spectroscopy (FFS) technique is capable of monitoring changes in concentration, mass, size and structure of fluorescent-labeled bio-molecules in microscopic volume and is suitable for measuring biological interactions in living cells. FFS data may be affected by many experimental factors in complicated biological systems. Using a Monte Carlo approach, we generate fluorescence fluctuation data for different experimental systems. This approach helps to separate the contributions by different experimental factors in a complicated fluorescence fluctuation spectrum. It also helps to validate new theoretical models and new fitting formulations. We describe the algorithm of the simulation program and tests on its statistical performance. The program is then used successfully to study the effects of several experimental factors on FFS detection.

关键词： fluorescence fluctuation spectroscopy, fluorescence correlation spectroscopy, Monte Carlo simulation.

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Optimizing Concurrent Product Development Process Using Genetic Algorithm

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Systems Science and Systems Engineering 2000年第4期10卷 503-510页

作者： YAN Ji\|hong,\ WU Cheng CIMS center, department of Automation, tsinghua university, beijing 100084, china

Scheduling concurrent activities is of great significance to shorten development lead time and minimize the cost, a heuristic optimization scheduling approach therefore is proposed for concurrent product development process, in which some uncertain crucial parameters are determined by genetic algorithm (GA). To ensure the optimal concurrent scheduling and the effective utilization of resources along with the fluent delivery of information, some key factors such as time order, information, resources, lead time and overlapping time of activities are taken into account adequately, and the weights of these factors are fixed by GA. In addition, role allocation and feedback revision process are realized in optimization module. The simulation example is a part of a certain product development process, and the results show the feasibility of the algorithm.

关键词： concurrent engineering product development process optimization scheduling

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Discovery of a high confidence soft lag from an X-ray flare of Markarian 421

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Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 224-227页

作者： ZHANG YouHong1,HOU ZhengTian2,SHAO Li3 & ZHANG Peng1 1 department of physics and tsinghua center for astrophysics(THCA),tsinghua university,beijing 100084,china 2 Group of Mathematics and physics,Shangqiu Medical College,Shangqiu 476100,china 3 Max-Planck-Institut für extraterrestrische Physik,Postfach 1312,Garching 85741,Germany 1. department of physics and tsinghua center for astrophysics (THCA) Tsinghua University Beijing 100084 China 2. Group of Mathematics and physics Shangqiu Medical College Shangqiu 476100 China 3. Max-Planck-Institut für extraterrestrische Physik Postfach 1312 Garching 85741 Germany

We present the X-ray variability properties of the X-ray and TeV bright blazar Mrk 421 with a-60 ks long XMM-Newton observation performed on November 9-10,*** source experienced a pronounced flare,of which the inter-band time lags were determined with a very high confidence *** soft(0.6-0.8 keV) X-ray variations lagged the hard(4-10 keV) ones by 1.09+0.11-0.12 ks,and the soft lag increases with increasing difference in the photon *** energy-dependent soft lags can be well fitted with the difference of the energy-dependent cooling timescales of the relativistic electron distribution responsible for the observed X-ray emission,which constrains the magnetic field strength and Doppler factor of the emitting region to be Bδ 1/3-1.78 Gauss.

关键词： BL Lacertae objects:individual:Mrk-421 galaxies:active radiation mechanisms:non-thermal X-rays:galaxies

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Testing local realism in P → VV decays

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Science china(physics,Mechanics & Astronomy) 2010年第5期53卷 870-875页

作者： LI JunLi1 & QIAO CongFeng1,2 1department of physics,Graduate university of Chinese Academy of Sciences,beijing 100049,china 2Theoretical physics center for Science Facilities(TPCSF),Chinese Academy of Sciences,beijing 100049,china 1. department of physics Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Theoretical Physics Center for Science Facilities (TPCSF) Chinese Academy of Sciences Beijing 100049 China

It was found that the vector meson pair from the pseudoscalar decays can form an entangled *** this work we give out detailed explanations on the polarization correlation of the two entangled vector *** is demonstrated that an experimental test of the Clauser-Horne inequality can be carried out through measuring the azimuthal distribution of four pseudoscalars in the cascade decay ηc→ VV →(PP)(PP),and the measurement of this process is feasible with the current running experiments in tau-charm ***,a brief discussion on the polarization correlation of the two vector mesons from B → VV decays is also presented.

关键词： nonlocality test high energy experiment meson decays

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Isochronous centers and Isochronous Functions

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Acta Mathematicae Applicatae Sinica 2002年第2期18卷 315-324页

作者： Li-jun Yangdepartment of Mathematical Sciences of tsinghua university, beijing 100084, china department of Mathematical Sciences of tsinghua university Beijing China

We study isochronous centers of two classes of planar systems of ordinary differential equations. For the first class which is the Lienard systems of the form x=y-F(x), y=-g(x) with a center at the origin, we prove that if g is isochronous (see Definition 1.1), then the center is isochronous if and only if F≡0. For the second class which is the Hamiltonian systems of the form i=-g(y), y=f(x) with a center at the origin, we prove that if / or g is isochronous, then the center is isochronous if and only if the other is also isochronous.

关键词： Isochronous center Lienard system monotonicity period function

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GRAPH-DIRECTED STRUCTURES OFSELF-SIMILAR SETS WITH OVERLAPSGRAPH-DIRECTED STRUCTURES OFSELF-SIMILAR SETS WITH OVERLAPSS

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Chinese Annals of Mathematics,Series B 2000年第4期21卷 403-412页

作者： HUASu RAOHUI departmentofMathematics TsinghuaUniversityBeijing100084China. departmentofMathematics WuhanUniversityWuhan430072China.

Some kinds of the self-similar sets with overlapping structures are studied by introducing the graph-directed constructions satisfying the open set condition that coincide with these sets. In this way, the dimensions ... 详细信息

关键词： Self-similar sets Graph-directed sets Overlapping Label Pisot number

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On the definition of fractional derivatives in rheology

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Theoretical & Applied Mechanics Letters 2011年第1期1卷 62-65页

作者： Fan Yang~(1,2,a)) and Ke-Qin Zhu~(1,b)) 1)department of Engineering Mechanics,tsinghua university,beijing 100084,china 2)department of physics,the Chinese university of Hong Kong,Hong Kong,china department of physics the Chinese University of Hong Kong Hong Kong China

During the last two decades fractional calculus has been increasingly applied to physics, especially to *** is well known that there are obivious differences between Riemann-Liouville (R-L) definition and Caputo definition,which are the two most commonly used definitions of fractional *** multiple definitions of fractional derivatives have hindered the application of fractional calculus in *** this paper,we clarify that the R-L definition and Caputo definition are both Theologically unreasonable with the help of the mechanical analogues of the fractional element *** also find that to make them more reasonable Theologically,the lower terminals of both definitions should be put to—∞.We further prove that the R-L definition with lower terminal—∞and the Caputo definition with lower terminal—∞are equivalent in the differentiation of functions that are smooth enough and functions that have finite number of singular *** we can define the fractional derivatives in rheology as the R-L derivatives with lower terminal—∞(or,equivalently,the Caputo derivatives with lower terminal—∞) not only for steady-state processes,but also for transient processes.

关键词： fractional derivative Caputo definition Riemann-Liouville definition Scott-Blair model

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