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Numerical Simulation of Shrinkage Cavity Formation in Spheroidal Graphite Iron Castings Based on Micro Modeling

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International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 9-12页

作者： Wenzhen Li Baicheng Liu Shantong Jin (Metallurgy Engineering School, university of science and technology beijing, beijing 100083, china)(department of Mechanical Engineering, tsinghua university, beijing 100084, china) Metallurgy Engineering School University of Science and Technology Beijing Beijing 100083 China department of Mechanical Engineering Tsinghua University Beijing 100084 China

A micro-modeling method (MM) for the quantitative prediction of the shrinkage cavity formation in SGiron castings is proposed. The mathematical models describing the volume changes during the solidification ofspheroidal graphite cast iron are established based on the models of solidification kinetics. The shrinkage cavityformation of T-shaped SG iron castings is calculated with MM method. The calculated results are compared with theexperimental results. It is shown that the predicted size, shape and distribution of shrinkage cavity by MM methodare in good agreement with the measured results.

关键词： solidification shrinkage numerical simulation micro modeling spheroidal graphite cast iron

A note on the crossed product R(A, α) associated with PSL_2(R)

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science china Mathematics 2008年第11期51卷 2081-2088页

作者： WU WenMing 1 School of Mathematical and computer science, Chongqing Normal university, Chongqing 400047, china 2 department of Mathematical science, tsinghua university, beijing 100084, china School of Mathematical and computer science Chongqing Normal University Chongqing China department of Mathematical science Tsinghua University Beijing China

Given the hyperbolic measure dxdy/y2 on the upper half plane H, the rational actions of PSL2(R) on H induces a continuous unitary representation α of this group on the Hilbert space L2(H, dxdy/y2). Supposing that A = {Mf : f ∈ L∞(H, dxdy/y2)}, we show that the crossed product R(A,α) is of type I. In fact, the crossed product R(A,α) is *-isomorphic to the von Neumann algebra B(L2(P,ν))■LK, where LK is the abelian group von Neumann algebra generated by the left regular representation of K.

关键词： crossed product rational actions PSL2(R) von Neumann algebras

The structural analysis of fuzzy measures

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science china(Information sciences) 2011年第1期54卷 38-50页

作者： ZHANG Ling1,ZHANG Bo2 & ZHANG YanPing1 1 computer science College,Anhui university,Hefei 230039,china 2State Key Lab of Intelligent technology & Systems tsinghua National Lab for Information science & technology Information science & technology College,computer science & technology,tsinghua university,beijing 100084,china computer science College Anhui University State Key Lab of Intelligent technology & Systems tsinghua National Lab for Information science & technology Information Science & Technology College Computer Science & Technology Tsinghua University

From quotient space based granular computing theory we explore the fuzzy measures of fuzzy sets. Based on the structural analysis of fuzzy sets,we present an"isotropism"*** this assumption we achieved the following insights:(1)the uniqueness of a fuzzy measure being isotropic on a finite complete semi-ordered set;(2)the necessary and suffcient condition of the isomorphism for fuzzy measure functions in fuzzy mathematics;(3)the necessary and suffcient condition that fuzzy measures have fuzzy and granular monotonicity;(4)under a certain assumption,the analytic expression for fuzzy *** results clarify the relationship between fuzzy measures and granular computing,reveal the essence of fuzzy measures,and provide a simple way of constructing fuzzy measures.

关键词： quotient space fuzzy set fuzzy measure rough set structural analysis

Generalized gradient projection neural networks for nonsmooth optimization problems

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science china(Information sciences) 2010年第5期53卷 990-1005页

作者： LI GuoCheng 1 , SONG ShiJi 2 ? & WU Cheng 2 1 department of Mathematics, beijing Information science and technology university, beijing 100192, china 2 department of Automation, tsinghua university, beijing 100084, china department of Mathematics Beijing Information Science and Technology University Beijing China department of Automation Tsinghua University Beijing China

Generalized gradient projection neural network models are proposed to solve nonsmooth convex and nonconvex nonlinear programming problems over a closed convex subset of R n . By using Clarke’s generalized gradient, the neural network modeled by a differential inclusion is developed, and its dynamical behavior and optimization capabilities both for convex and nonconvex problems are rigorously analyzed in the framework of nonsmooth analysis and the differential inclusion theory. First for nonconvex optimization problems, the quasi convergence results similar to those achieved by previous work are proved. For convex optimization problems, the global convergence results are proved, i.e. any trajectory of the neural network converges to an asymptotically stable equilibrium point, which is an optimal solution of the primal problem whenever it exists. This result remains valid even if the initial condition is chosen outside the feasible set. In addition, an asymptotic control result involving a Tykhonov like regularization shows that any trajectory of the revised neural network can be forced to converge toward a particular optimal solution of the primal problem. Finally, two simulation optimization algorithms for solving the optimization and control problems are designed respectively, and three typical simulation experiments are illustrated to present the accuracy and efficiency of theoretical convergence results of this paper.

关键词： nonsmooth optimization problem generalized gradient projection networks differential inclu sions convergence

Aeroservoelastic model based active control for large civil aircraft

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science china(Technological sciences) 2010年第4期53卷 1126-1137页

作者： FAN Yong1,ZHU JiHong1,HU ChunHua2,MENG XianYu1,WANG XiangYang2 & GE AiXue1 1 department of computer science and technology,tsinghua university,beijing 100084,china 2 School of Astronautics and Aeronautics,tsinghua university,beijing 100084,china department of computer science and technology Tsinghua University School of Astronautics and Aeronautics Tsinghua University

A modeling and control approach for an advanced configured large civil aircraft with aeroservoelasticity via the LQG method and control allocation is *** models and implementation issues for the multi-input/multi-output(MIMO) aeroservoelastic system simulation developed for a flexible wing with multi control surfaces are described.A fuzzy logic based optimization approach is employed to solve the constrained control allocation problem via intelligently adjusting the components of output vector and find a proper vector in the attainable moment set(AMS) *** basic idea is to minimize the L2 norm of error between the desired moment and achievable moment using the designing freedom provided by redundantly allocated actuators and control *** the constraints of control surfaces,in order to obtain acceptable performance of aircraft such as stability and maneuverability,the fuzzy weights are updated by the learning algorithm,which makes the closed-loop system ***,an application example of flight control designing for the advanced civil aircraft is discussed as a *** studies we have performed showed that the advanced configured large civil aircraft has good performance with the proper designed control law designed via the proposed *** gust alleviation and flutter suppression are applied with the synergetic effects of elevator,ailerons,equivalent rudders and *** results show good closed loop performance and meet the requirement of constraint of control surfaces.

关键词： modeling active control aeroelastic flutter suppression control allocation

Expression of lignin peroxidase H2 from Phanerochaete chrysosporium by multi-copy recombinant Pichia strain

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Journal of Environmental sciences 2009年第2期21卷 218-222页

作者： WANG Wei,WEN Xianghua department of Environmental science and Engineering,tsinghua university,beijing 100084,china. department of Environmental science and Engineering Tsinghua University Beijing 100084 China

The lipH2 gene, encoding the expression of lignin peroxidase, was cloned from Phanerochaete chrysosporium BKM-F-1767 and expressed in Pichia pastoris X-33, a yeast. The cDNA of LiPH2 was generated from total RNA extracted from P chrysosporium by PCR with primers that do not contain a P. chrysosporium lignin peroxidase secretion signal. The gene was then successfully inserted into the expression vector pPICZα, and resulted in the recombinant vector pPICZα-lipH2. The transformation was conducted in two ways. One was using the wild Pichia pastoris as the recipients, which results in the recombinant P. pastoris with single or low lipH2 gene copy. The second was using P. pastoris and single or low lipH2 gene copy as the recipients, which results in the recombinant P. pastoris with multi-copies of lipH2 genes. This study firstly expressed the gene lipH2 in P. pastoris and achieved the successful expression of the lipH2 depending upon the generation of a recombinant strain that contained multiple copies. The lignin peroxidase activity reached a maximum of 15 U/L after 12 h induction.

关键词： heterologous expression lignin peroxidase Pichia pastoris

Remarks on the bounds for cryptanalysis of low private key RSA

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Progress in Natural science:Materials International 2009年第10期19卷 1327-1331页

作者： Haijian Zhou a,Ping Luo b,Daoshun Wang a,Yiqi Dai a a department of computer science and technology,tsinghua university,beijing 100084,china b School of Software,tsinghua university,beijing 100084,china department of computer science and technology Tsinghua University Beijing 100084 China School of Software Tsinghua University Beijing 100084 China

Boneh and Durfee have developed a cryptanalytic algorithm on low private key *** algorithm is based on lattice basis reduction and breaks RSA with private key d < N0:*** on,an improved version by Blmer and May enhan... 详细信息

Boneh and Durfee have developed a cryptanalytic algorithm on low private key *** algorithm is based on lattice basis reduction and breaks RSA with private key d 277 for ordinary RSA systems with a 1024-bit public key eN;eT.

关键词： RSA Cryptanalysis Low private key Lattice basis reduction

SUPERSATURATED DESIGN WITH MORE THAN TWO LEVELS

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Chinese Annals of Mathematics,Series B 2001年第2期22卷 183-194页

作者： LU XUAN SUN YIZHOU department of Mathematical science, tsinghua university, beijing 100084, china. department of Mathematical science Tsinghua Univeristy Beijing 100084 China

Supersaturated designs are useful in screening experiments. This paper discusses the topic of multi-level supersaturated design. Two quantities, E(d2) and Df, are proposed to evaluate the optimality of supersaturated designs. A lower bound of E(d2) is obtained with a necessary condition for achieving it. Some E(d2)-optimal supersaturated designs of 3, 4, and 5 levels are given.

关键词： D-efficiency Screening experiment Fractional factorial design Orthogonality

(2,n)secret sharing scheme for gray and color images based on Boolean operation

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science china(Information sciences) 2012年第5期55卷 1151-1161页

作者： DONG Lin 1,WANG DaoShun 1,LI ShunDong 2 & DAI YiQi 1 1 department of computer science and technology,tsinghua university,beijing 100084,china 2 School of computer science,Shaanxi Normal university,Xi'an 710062,china department of computer science and technology Tsinghua University Beijing China School of computer science Shaanxi Normal University Xi’an China

Traditional secret sharing (SS) schemes can reconstruct the secret precisely,but have high com-putation *** secret sharing (VSS) schemes use human visual system to reconstruct the secret without cryptographic computation,but have pixel expansion and loss of *** et *** a (2,n)-SS scheme for binary images based on Boolean operation,which has low computation complexity,no pixel expansion and the contrast is 1/*** this paper,we first construct an r runs (2,n)-SS scheme to improve the contrast of Wang et al.'s binary (2,n)-SS *** we present two approaches to construct r runs (2,n)-SS schemes for grayscale image and color *** two approaches are both based on Boolean operation,while one approach uses halftone technology and the other uses bit level *** proposed schemes have low computation complexity and almost ideal contrast.

关键词： secret sharing scheme Boolean operation halftone contrast