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A particle-based method for granular flow simulation

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science china(information sciences) 2012年第5期55卷 1062-1072页

作者： CHANG YuanZhang 1,BAO Kai 2,3,ZHU Jian 1 & WU EnHua 1,2 1 department of computer and information science,university of macau,macao,china 2 State Key Laboratory of computer science,Institute of Software,Chinese Academy of sciences,Beijing 100190,china 3 Division of Mathematical and computer sciences & Engineering,KAUST,Thuwal,Saudi Arabia 1. department of computer and information science University of Macau Macao China2. State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing 100190 China3. Division of Mathematical and Computer Sciences & Engineering KAUST Thuwal Saudi Arabia

We present a new particle-based method for granular flow *** the method,a new elastic stress term,which is derived from a modified form of the Hooke's law,is included in the momentum governing equation to handle the friction of granular *** force is also added to simulate the dynamic friction for the purpose of smoothing the velocity field and further maintaining the simulation *** from the Lagrangian nature of the SPH method,large flow deformation can be well handled easily and *** addition,a signed distance field is also employed to enforce the solid boundary *** experimental results show that the proposed method is effective and efficient for handling the flow of granular materials,and different kinds of granular behaviors can be well simulated by adjusting just one parameter.

关键词： granular materials sand smoothed particle hydrodynamics SPH Hooke’s law animation simu-lation

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

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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 1. School of computer science and Technology Anhui University Hefei 230039 China2. Department of Electronic Information and Electrical Engineering Hefei University Hefei 230022 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

Image universal steganalysis based on best wavelet packet decomposition

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science china(information sciences) 2010年第3期53卷 634-647页

作者： LUO XiangYang1,2, LIU FenLin1, YANG ChunFang1 & WANG DaoShun2 1information science and Technology Institute, Zhengzhou 450002, china 2department of computer science and Technology, Tsinghua university, Beijing 100084, china 1. information science and Technology Institute Zhengzhou 450002 China2. Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Based on the best wavelet packet decomposition of images, a new universal steganalysis method with high detection correct ratio is proposed. First, the best wavelet packet decomposition of image based on the Shannon entropy information cost function is made. Second, high order absolute characteristic function moments of histogram extracted from the coefficient subbands obtained by best wavelet packet decomposition are regarded as features. Finally, these features are processed and a back-propagation (BP) neural network is designed to classify original and stego images. Three different steganalysis algorithms for three different cases of background and application condition are presented. To validate the performance of the proposed method, a series of experiments are made for six kinds of typical steganography methods, i.e. LSB, LTSB, PMK, Jsteg, F5 and JPHide. Results show that, the average detection accuracy of the proposed method exceeds at least 6.4% and up to 15.4% and has a better universal performance than its closest competitors. Furthermore, the proposed method can provide reference for designing the pattern recognition and classification algorithm based on best wavelet packet decomposition.

关键词： steganography digital images universal steganalysis best wavelet packet decomposition BP neural network

The essential ability of sparse reconstruction of different compressive sensing strategies

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science china(information sciences) 2012年第11期55卷 2582-2589页

作者： ZHANG Hai1,2,LIANG Yong3,GOU HaiLiang1 & XU ZongBen1 1 Institute for information and System science,Xi'an Jiaotong university,Xi'an 710049,china 2department of Mathematics,Northwest university,Xi'an 710069,china 3university of science and Technology,macau 999078,china 1. Institute for information and System science Xi’an Jiaotong University Xi’an 710049 China2. Department of Mathematics Northwest University Xi’an 710069 China3. University of Science and Technology Macau 999078 China

We show the essential ability of sparse signal reconstruction of different compressive sensing strategies,which include the L1 regularization,the L0 regularization(thresholding iteration algorithm and OMP algorithm),the Lq(0 2 regularization can be taken as a representative of the Lq(0 2 2 regularization always yields the sparsest solutions and when 0 2 the performance of the regularizations takes no significant *** results of this paper provide experimental evidence for our previous work.

关键词： compressive sensing regularization sparsity L1/2 regularization

Presenting degenerate Ringel-Hall algebras of type B

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science china Mathematics 2012年第5期55卷 949-960页

作者： FAN LiJuan1 & ZHAO ZhongHua2,1department of Mathematics,Beijing Normal university,Beijing 100875,china 2department of Mathematics and computer science,School of science,Beijing university of Chemical Technology,Beijing 100029,china 1. department of Mathematics Beijing Normal University Beijing 100875 China2. Department of Mathematics and Computer Science School of Science Beijing University of Chemical Technology Beijing 100029 China

We give a presentation for the degenerate Ringel-Hall algebras of type B by studying the corresponding generic extension monoid *** an application,it is shown that the degenerate Ringel-Hall algebras of type B admit m... 详细信息

关键词： degenerate Ringel-Hall algebras generic extension monoid algebras Auslander-Reiten quivers Frobenius morphism

Irregular wavelet frames on L^2 (R^n)

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science china Mathematics 2005年第2期48卷 277-287页

作者： YANG Deyun & ZHOU Xingwei department of information & Technology, Nankai university, Tianjin 300071, china department of Mathematics, Nankai university, Tianjin 300071, china department of computer science, Taishan College, Taian 271000, china 1. department of information & Technology Nankai University 300071 Tianjin China 2. department of Mathematics Nankai University 300071 Tianjin China 3. department of computer science Taishan College 271000 Taian China

In this paper, we present the conditions on dilation parameter {sj}j that ensure a discrete irregular wavelet system to be a frame on L2(Rn), and for the wavelet frame we consider the perturbations of translation para... 详细信息

关键词： wavelet transform, frame, wavelet frame, irregular dilation.

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An introduction to Tsinghua Cloud

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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 1. department of computer science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 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

A stochastic policy search model for matching behavior

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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 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 China2. Department of Computer Science and Technology Zhejiang University of Technology Hangzhou 310014 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

A user-space file system for on-demand legacy desktop software

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science china(information sciences) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1,2 , SU GeLin 1,2 & ZHENG WeiMin 1,2 1 department of computer science and Technology, Tsinghua university, Beijing 100084, china 2 Tsinghua National Laboratory for information science and Technology, Tsinghua university, Beijing 100084, china 1. department of computer science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 37%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage