检索结果-南通市图书馆

science china(Technological sciences) 2009年第1期52卷 72-78页

作者： WANG Bo1, WANG RongXiu2 & WU Yong1 1 School of Mathematic science, chongqing Institute of technology, chongqing 400050, china 2 department of computer science and information engineering, chongqing technology and business university, chongqing 400067, china School of Mathematic science Chongqing Institute of Technology Chongqing China department of computer science and information engineering Chongqing Technology and Business University Chongqing China

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be acceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforcement.

关键词： short-fiber reinforcement Young’s modulus finite element Gaussian distribution

The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

在线全文

学校读者我要写书评

暂无评论

中国科学:技术科学 2010年第4期 438-438页

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length,as well as on the fiber orientation *** on periodic tetrakaidecahedrons,the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also *** proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene(PP) *** fiber length/orientation distributions were modeled by Gaussian probability density *** fiber volume fractions,different lengths,and different distributions were *** predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results,and the agreement was found to be *** proposed finite element models were proved to be acceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforcement.

关键词： short-fiber reinforcement Young’s modulus finite element Gaussian distribution

A POSTERIORI ERROR ANALYSIS OF NONCONFORMING METHODS FOR THE EIGENVALUE PROBLEM

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems science & Complexity 2009年第3期22卷 495-502页

作者： Youai LiCollege of computer and information engineering, Beijing technology and business university, Beijing100048,china. College of computer and information engineering Beijing Technology and Business University Beijing China

This paper extends the unifying theory for a posteriori error analysis of the nonconformingfinite element methods to the second order elliptic eigenvalue *** particular,the authorproposes the a posteriori error estimator for nonconforming methods of the eigenvalue problems andprove its reliability and efficiency based on two assumptions concerning both the weak continuity andthe weak orthogonality of the nonconforming finite element spaces,*** addition,the authorexamines these two assumptions for those nonconforming methods checked in literature for the Laplace,Stokes,and the linear elasticity problems.

关键词： A posteriori error analysis eigenvalue problem nonconforming finite element.

In-situ Characterization of Non-aqueous Nano-dispersion Systems by Freeze-etching TEM and Comparative Study with Laser Scattering Method

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of technology(Materials science) 2010年第3期25卷 432-436页

作者：欧忠文 department of Architecture and Civil engineering Logistics Engineering University

In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was *** improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was ***,distribution and morphology of NANDS were directly *** information of particle dispersion feature and particle density can also be *** of the FETEM characterization is *** with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle ***,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.

关键词： non-aqueous nano-dispersion system dispersion state in-situ characterization freeze-etching laser scattering method

Performance Modeling and Approximate Analysis of Multiserver Multiqueue Systems with Poisson and Self-similar Arrivals

在线全文

学校读者我要写书评

暂无评论

Journal of university of science and technology Beijing 2001年第2期8卷 145-151页

作者： Zhiguang Shan, Chuang Lin, Yang Yang, Yan Wang (information engineering School, university of science and technology Beijing, Beijing 100083, china) (department of computer science and technology, Tsinghua university, Beijing 100084, china) information engineering School University of Science and Technology Beijing 100083 China

The problem of state space explosion is still ran outstanding challenge in Markovian performance analysis for multiserver multiqueue (MSMQ) systems. The system behavior of a MSMQ system is described using stochastic high-level Petri net (SHLPN) models, and an approximate performance analysis technique is proposed based on decomposition and refinement methods as well as iteration technique. A real MSMQ system, Web-server cluster, is investigated. The performance of an integrated scheme of request dispatching and scheduling is analyzed with both Poisson and self-similar request arrivals. The study shows that the approximate analysis technique significantly reduces the complexity of the model solution and is also efficient for accuracy of numerical results.

关键词： multiserver multiqueue (MSMQ) system Web-server cluster performance analysis stochastic high-level Petri net (SHLPN) request dispatching request scheduling

Seamlet carving for shape-aware image resizing

在线全文

学校读者我要写书评

暂无评论

science china(information sciences) 2012年第5期55卷 1073-1081页

作者： LIN Xiao 1,2,SHENG Bin 1,MA LiZhuang 1,SHEN Yang 1 & CHEN ZhiHua 3 1 department of computer science and engineering,Shanghai Jiao Tong university,Shanghai 200240,china 2 Academy of information technology,Luoyang Normal university,Luoyang 471022,china 3 department of computer science and engineering,East china university of science and technology,Shanghai 200237,china department of computer science and engineering Shanghai Jiao Tong University Shanghai China Academy of information technology Luoyang Normal University Luoyang China department of computer science and engineering East China University of Science and Technology Shanghai China

In this paper we propose an optimized seam-carving approach for anti-shearing image *** image/video seam-carving strategy only focuses on deleting the pixels along 8-connected seams,which may lead to the obvious information loss during *** the traditional seam-carving methods,our approach can construct a seamlet to handle the discontinuous pixels and further achieve an optimized image resizing results with *** particular,to suppress zigzag artifacts,we introduce the anti-shearing energy into the seamlet generation,which includes two steps:1) the energy map is formalized by using Gabor filtering and the saliency map;2) The energy computation is optimized in Gabor feature space to obtain the resizing results without the connectivity *** experimental results and comparisons show the effectiveness of our method.

关键词： image resizing seamlet carving saliency map

A stochastic policy search model for matching behavior

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(information sciences) 2011年第7期54卷 1430-1443页

作者： CHENG ZhenBo 1,2,ZHANG Yu 1 & DENG ZhiDong 1 1 State Key Laboratory on Intelligent technology and Systems,Tsinghua National Laboratory for information science and technology,department of computer science,Tsinghua university,Beijing 100084,china 2 department of computer science and technology,Zhejiang university of technology,Hangzhou 310014,china State Key Laboratory on Intelligent technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Computer Science Tsinghua University Beijing China department of computer science and technology Zhejiang University of Technology Hangzhou China

The matching law is one of the basic empirical laws in decision theory,and it states that a subject’s preference to optional targets depends on which choices are *** this paper,we study the possible mechanisms that explain why subjects’ decisions often obey this *** the basis of reinforcement learning theory,we put forward a decision-making model in which the policy is updated by a policy parameter,and the model might be implemented in the brain through the prefrontal cortex and the basal ganglia neural *** on this model,an algorithm that satisfies the matching law is derived under some simple *** analysis and simulation results show that the decision behavior achieved by the algorithm obeys the matching *** addition,the matching behaviors in two classical experiments are reproduced using the *** results provide a reasonable strategy for the matching law and a useful computational tool for rewarded decision-making tasks.

关键词： policy model matching law reinforcement learning decision-making model

An introduction to Tsinghua Cloud

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(information sciences) 2010年第7期53卷 1481-1486页

作者： ZHENG WeiMin1,2 1department of computer science and technology, Tsinghua university, Beijing 100084, china 2Tsinghua National Laboratory for information science and technology, Beijing 100084, china department of computer science and technology Tsinghua University Beijing China Tsinghua National Laboratory for information science and technology Beijing China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of Tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

Superconductivity of small metal grains

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 431-441页

作者： ZHENG Renrong1 CHEN Zhiqian2 & ZHU Shunquan1,3 1. department of Physics, Shanghai Normal university, Shanghai 200234, china 2. department of Physics, Southwest Normal university, chongqing 400715, china 3. department of computer and Electric technology, Shanghai business School, Shanghai 201400, china department of Physics Shanghai Normal University Shanghai China department of Physics Southwest Normal University Chongqing China department of computer and Electric technology Shanghai Business School Shanghai China

The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

关键词： size effect, superconductivity enhancements, small metallic grains.

Fast parallel algorithms for discrete Gabor expansion and transform based on multirate filtering

在线全文

学校读者我要写书评

暂无评论

science china(information sciences) 2012年第2期55卷 293-300页

作者： TAO Liang1 & GU JuanJuan2 1School of computer science and technology,Anhui university,Hefei 230039,china 2department of Electronic information and Electrical engineering,Hefei university,Hefei 230022,china School of computer science and technology Anhui University Hefei China department of Electronic information and Electrical engineering Hefei University Hefei China

The Gabor transform has long been recognized as a very useful tool for the joint time and frequency analysis in signal *** real time applications,however,were limited due to the high computational complexity of the Gabor transform *** this paper,some novel and fast parallel algorithms for the finite discrete Gabor expansion and transform are presented based on multirate *** analysis filter bank is designed for the finite discrete Gabor transform(DGT)and a synthesis filter bank is designed for the finite discrete Gabor expansion(DGE).Each of the parallel channels in the two filter banks has a unified structure and can apply the FFT and the IFFT to reduce its computational *** computational complexity of each parallel channel does not change as the oversampling rate *** fact,it is very low and depends only on the length of the input discrete signal and the number of the Gabor frequency sampling *** computational complexity of the proposed parallel algorithms is analyzed and compared with that of the major existing parallel algorithms for the finite DGT and *** results indicate that the proposed parallel algorithms for the finite DGT and DGE based on multirate filtering are very attractive for real time signal processing.

关键词： discrete Gabor expansion discrete Gabor transform critical sampling and oversampling multirate filtering analysis and synthesis filter banks