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Solving the input data in error correc-tion of optical fabrication by finite Fourier coefficient algorithm

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science china(Technological sciences) 2006年第1期49卷 50-60页

作者： CHENG Haobo1,2, SUN Guozheng3 & FENG Zhijing2 1. Department of Optical engineering, beijing Institute of technology, beijing 100081, china 2. Department of Precision Instruments and Mechanology, Tsinghua university, beijing 100084, china 3. china North Industries Group Corporation, beijing 100089, china 1. Department of Optical engineering Beijing Institute of Technology Beijing 100081 China 2. Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China 3. china North Industries Group Corporation Beijing 100089 China

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influ-ence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

关键词： optical fabrication, computer controlled optical surfacing, free-form lens, finite Fourier coefficient, error correction.

维普期刊数据库

A quasi-human algorithm for solving the three-dimensional rectangular packing problem

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science china(Information sciences) 2010年第12期53卷 2389-2398页

作者： HE Kun & HUANG WenQi school of computer science and technology, Huazhong university of science and technology, Wuhan 430074, china 1. school of computer science and technology Huazhong University of Science and Technology Wuhan 430074 China

Based on the concept of maximal rectangular space that can be filled at current time and the siege warfare tactics, we make several critical improvements on the quasi-human caving-degree approach to get a stronger algorithm ICDA for a classical NP hard problem: the three-dimensional rectangular packing problem. Within similar computing time, the new algorithm gained an average volume utilization of 90.92% on the natural and difficult 100 benchmarks, called BR15, where items to be packed are almost different in size. Compared with current best record just reported in the literature in 2010, our result makes an improvement by 0.54%.

关键词： NP hard three-dimensional packing quasi-human action space caving degree

Experimental investigation of MIMO relay channels statistics and capacity based on wideband outdoor measurements at 2.35 GHz

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science china(Information sciences) 2011年第9期54卷 1945-1956页

作者： NIE Xin 1,2,ZHANG JianHua 1,2,LIU ZeMin 1 & ZHANG Ping 1,2 1 Key Laboratory of Universal Wireless communications,Ministry of Education beijing university of Posts and Telecommunications,beijing 100876,china 2 Wireless technology Innovation Institute,beijing university of Posts and Telecommunications,beijing 100876,china 1. Key Laboratory of Universal Wireless communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China2. Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

Relay,which serves to enhance the performance of future communication networks,is one of the most promising techniques for IMT-Advanced *** potential performance improvement of relay is investigated in this *** investigation consists of two *** the first step,to obtain a better understanding of the fundamental properties of relay channels,we conducted outdoor measurements at 2.35 GHz with 50 MHz bandwidth in a typical urban area of *** links constituting the relay transmission,i.e.,the link between base station and relay station,the link between relay station and mobile station and the link between base station and mobile station were measured by employing a real-time channel *** main factors that affect the MIMO channel capacity,i.e.,the channel gain and effective degrees of freedom,are *** cross-polarization discrimination was obtained by utilizing space-alternating generalized expectation-maximization *** channel parameters of the three links are statistically analyzed and *** the second step,based on the measured data,the performance of different relaying schemes,i.e.,amplify-and-forward and decode-and-forward,is *** impact of RS antenna configuration on the capacity is also *** measurement and evaluation results reveal that the relay can significantly improve the system coverage and performance.

关键词： MIMO relay channels IMT-Advanced frequency band channel characteristics relay performance evaluation

A centrality measure based on spectral optimization of modularity density

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science china(Information sciences) 2010年第9期53卷 1727-1737页

作者： FU LiDong1,2*,GAO Lin1 & MA XiaoKe1 1school of computer science and engineering,Xidian university,Xi'an 710071,china 2College of computer,Xi'an university of science and technology,Xi'an 710054,china 1. school of computer science and engineering Xidian University Xi’an 710071 China2. College of Computer Xi’an University of Science and Technology Xi’an 710054 China

Centrality analysis has been shown to be a valuable method for the structural analysis of complex *** is used to identify key elements within networks and to rank network elements such that experiments can be tailored to interesting *** this paper,we show that the optimization process of modularity density can be written in terms of the eigenspectrum of kernel *** on the eigenvectors belonging to the largest eigenvalue of kernel matrix,we present a new centrality measure that characterizes the contribution of each node to its assigned community in a network,called modularity density *** measure is illustrated and compared with the standard centrality measures by using respectively an artificial example and a classic network data *** statistical distribution of modularity density centrality is investigated by considering large computer generated graphs and two large networks from the real *** results show the significance of the proposed approach.

关键词： centrality modularity density centrality kernel matrix eigenspectrum

A new algorithm for fast mining frequent itemsets using N-lists

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science china(Information sciences) 2012年第9期55卷 2008-2030页

作者： DENG ZhiHong ,WANG ZhongHui & JIANG JiaJian Key Laboratory of Machine Perception(Ministry of Education),school of Electronics engineering and computer science,Peking university,beijing 100871,china 1. Key Laboratory of Machine Perception (Ministry of Education) School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

Mining frequent itemsets has emerged as a fundamental problem in data mining and plays an essential role in many important data mining *** this paper,we propose a novel vertical data representation called N-list,which originates from an FP-tree-like coding prefix tree called PPC-tree that stores crucial information about frequent *** on the N-list data structure,we develop an efficient mining algorithm,PrePost,for mining all frequent *** of PrePost is achieved by the following three ***,N-list is compact since transactions with common prefixes share the same nodes of the ***,the counting of itemsets’ supports is transformed into the intersection of N-lists and the complexity of intersecting two N-lists can be reduced to O(m + n) by an efficient strategy,where m and n are the cardinalities of the two N-lists ***,PrePost can directly find frequent itemsets without generating candidate itemsets in some cases by making use of the single path property of *** have experimentally evaluated PrePost against four state-of-the-art algorithms for mining frequent itemsets on a variety of real and synthetic *** experimental results show that the PrePost algorithm is the fastest in most *** though the algorithm consumes more memory when the datasets are sparse,it is still the fastest one.

关键词： data mining frequent itemset mining data structure N-lists algorithm

Study on the P2P Cloud Storage Architecture Based on Semantic Hypergraph

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china communications 2015年第S2期12卷 39-47页

作者： SONG Ningning LIN Ruijie AN Xingshuo GONG Chao YAO Zhiyong school of Mechanical engineering University of Science and Technology Beijing china Academy of Telecommunication Research of MIIT school of computer and Communication engineering University of Science and Technology Beijing

Cloud storage has the characteristics of distributed and virtual, and it makes the ownership rights and management rights of users data separated. The master-slave architecture of cloud storage has a problem of single point failure. In this paper, we provide a cloud storage architecture model based on Semantic equivalence. According to semantic matching degree, this architecture divides the nodes into node cluster by creating semantic tree and maintains system routing through semantic hypergraph. Through simulation experiments show that dividing network into semantic can enhance scalability and flexibility of the system, and it can improve the efficiency of network organization and the security of cloud storage system, at the same time, it can also reduce the cloud data storage and the delay of reading time.

关键词： cloud storage hypergraph semantic modelling p2p

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Corslet: A shared storage system keeping your data private

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science china(Information sciences) 2011年第6期54卷 1119-1128页

作者： XUE Wei 1,2 , SHU JiWu 1,2 , LIU Yang 1 & XUE Mao 1 1 Department of computer science and technology, Tsinghua university, beijing 100084, china 2 Tsinghua National Laboratory for Information science and technology, Tsinghua university, 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

With the exponential growth of digital data, it is becoming more and more popular to store data in shared distributed storage systems inside the same organization. In such shared distributed storage systems, an ordinary user usually does not have the control permission over the whole system, and thus cannot secure data storage or data sharing of his own files. To solve this issue, this paper proposes a new system architecture to secure file storing and sharing efficiently over untrusted shared storage and network environments. Based on this architecture, this paper designs and implements a stackable secure storage system called Corslet. Corslet can run directly on deployed underlying storage systems without modification, while bringing end-to-end confidentiality and integrity as well as efficient access control for user data. For individual users, Corslet is easy to use, and does not require users to maintain or manage any keys on their client machines locally. The Bonnie++ and IOzone benchmark results show that the throughput of Corslet over NFS can achieve more than 90% of native NFS throughput in most tests, proving that Corslet can provide enhanced security for user data while maintaining acceptable performance.

关键词： storage security access control key management shared file system

Self-healing routing: failure,modeling and analysis

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science china(Information sciences) 2011年第3期54卷 609-622页

作者： XU MingWei 1,2 , LI Qi 1,2 , YANG Yuan 1,2 , HOU MeiJia 1,2 & PAN LingTao 1,2 1 Department of computer science, Tsinghua university, beijing 100084, china 2 Tsinghua National Laboratory for Information science and technology (TNList), beijing 100084, china 1. Department of computer science Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology (TNList) Beijing 100084 China

Network failures occur frequently, and self-healing ability of existing routing protocols cannot guarantee fast route convergence under these failures without impacting packet forwarding. During routing convergence, network routes may be incorrect and even routing black holes and loops occur, which will result in extensive packet loss and thus influence network performance. To solve this problem, several improved routing solutions have been proposed. In this paper, we propose the concept and model of self-healing routing and analyze the key problems in current intra-domain and inter-domain self-healing routing protocols after briefly reviewing the characteristics of network failures. We classify the different self-healing solutions into two categories based on their design principles: routing restoration and routing protection, and systematically analyze these different typical solutions. Finally, we discuss several key issues in self-healing routing and propose a hybrid protection and restoration based routing scheme.

关键词： failure intra-domain routing inter-domain routing self-healing routing

Adaptive bidirectional diffusion for image restoration

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science china(Information sciences) 2010年第12期53卷 2452-2460页

作者： FU ShuJun 1,2 & ZHANG CaiMing 1 1 school of computer science and technology, Shandong university, Jinan 250101, china 2.school of Mathematics, Shandong university, Jinan 250100, china 1. school of computer science and technology Shandong University Jinan 250101 China2. School of Mathematics Shandong University Jinan 250100 China

A large number of applications in image processing and computer vision depend on image quality. In this paper, combining the forward diffusion with the backward diffusion by different weights, we present an adaptive bidirectional diffusion method for image denoising and deblurring simultaneously. Further, we introduce a gradient factor into the data fidelity term, which forms a spatially varying constraint and allows a better restoration of image edges and fine details. In order to obtain a stable solution, we develop a numerically stable scheme and give its theoretical analysis. Finally, we show advantages of this method in deblurring edges, denoising and restoring fine details of image compared with other related methods in experiments.

关键词： image restoration bidirectional diffusion inverse diffusion anisotropic diffusion stabilizing scheme spatially varying constraint