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Level-of-Detail Rendering of Large-Scale Irregular Volume Datasets Using Particles

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Journal of Computer Science & Technology 2010年第5期25卷 905-915页

作者： Takuma Kawamura Naohisa Sakamoto Koji Koyamada member, ieee Graduate School of Engineering Kyoto University Kyoto 6068501 Japan Center for the Promotion of Excellence in Higher Education Kyoto University Kyoto 6068501 Japan

This paper describes a level-of-detail rendering technique for large-scale irregular volume *** is well known that the memory bandwidth consumed by visibility sorting becomes the limiting factor when carrying out volume rendering of such *** develop a sorting-free volume rendering technique,we previously proposed a particle-based technique that generates opaque and emissive particles using a density function constant within an irregular volume cell and projects the particles onto an image plane with *** the density function changes significantly in an irregular volume cell,the cell boundary may become prominent,which can cause blocky *** the number of the sub-pixels increases,the required frame buffer tends to be *** solve this problem,this work proposes a new particle-based volume rendering which generates particles using metropolis sampling and renders the particles using the ensemble average. To confirm the effectiveness of this method,we applied our proposed technique to several irregular volume datasets,with the result that the ensemble average outperforms the sub-pixel average in computational complexity and memory usage. In addition,the ensemble average technique allowed us to implement a level of detail in the interactive rendering of a 71-million-cell hexahedral volume dataset and a 26-million-cell quadratic tetrahedral volume dataset.

关键词： large-scale irregular volume level-of-detail volume rendering of unstructured meshes

A Multi-Key Pirate Decoder Against Traitor Tracing Schemes

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Journal of Computer Science & Technology 2010年第2期25卷 362-374页

作者：吴永东 member, ieee 邓慧杰 Institute for Infocomm Research A STAR 138632 Singapore School of Information Systems Singapore Management University 178902 Singapore

In this paper we introduce an architecture for a multi-key pirate decoder which employs decryption keys from multiple traitors. The decoder has built-in monitoring and self protection functionalities and is capable of defeating most multiple-round based traitor tracing schemes such as the schemes based on the black-box confirmation method. In particular, the proposed pirate decoder is customized to defeat the private key and the public key fully collusion resistant traitor tracing （FTT） schemes, respectively. We show how the decoder prolongs a trace process so that the tracer has to give up his effort. FTT schemes are designed to identify all the traitors. We show that decoder enables the FTT schemes to identify at most 1 traitors. Finally, assuming the decoder is embedded with several bytes of memory, we demonstrate how the decoder is able to frame innocent users at will.

关键词： broadcast encryption multi-key pirate decoder traitor tracing

Global-to-Local Approach to Rigorously Developing Distributed System with Exception Handling

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Journal of Computer Science & Technology 2009年第2期24卷 238-249页

作者：蔡超裘宗燕 Senior member, member, CCF, ieee 杨红丽赵翔鹏 LMAM and Department of Informatics School of Mathematical Science Peking University Beijing 100871 China College of Computer Sciences Beijing University of Technology Beijing 100124 China

Cooperative distributed system covers a wide range of applications such as the systems for industrial controlling and business-to-business trading, which are usually safety-critical. Coordinated exception handling （CEH） refers to exception handling in the cooperative distributed systems, where exceptions raised on a peer should be dealt with by all relevant peers in a consistent manner. Some CEH algorithms have been proposed. A crucial problem in using these algorithms is how to develop the peers which are guaranteed coherent in both normal execution and exceptional execution. Straightforward testing or model checking is very expensive. In this paper, we propose an effective way to rigorously develop the systems with correct CEH behavior. Firstly, we formalize the CEH algorithm by proposing a Peer Process Language to precisely describe the distributed systems and their operational semantics. Then we dig out a set of syntactic conditions, and prove its sufficiency for system coherence. Finally~ we propose a global-to-local approach, including a language describing the distributed systems from a global perspective and a projection algorithm, for developing the systems. Given a well-formed global description, a set of peers can be generated automatically. We prove the system composed of these peers satisfies the conditions, that is, it is always coherent and correct for CEH.

关键词： distributed system exception handling fault tolerant formal methods

Tree-Based Index Overlay in Hybrid Peer-to-Peer Systems

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Journal of Computer Science & Technology 2010年第2期25卷 313-329页

作者： InSung Kang SungJin Choi member, ieee SoonYoung Jung SangKeun Lee Computer Science and Engineering Department Korea University Seoul 136-713 Korea Corporate Center KT (Korea Telecom) Seoul 137-792 Korea Computer Science Education Department Korea University Seoul 136-701 Korea

Hybrid Peer-to-Peer （P2P） systems that construct overlay networks structured among superpeers have great potential in that they can give the benefits such as scalability, search speed and network traffic, taking advantages of superpeer-based and the structured P2P systems. In this article, we enhance keyword search in hybrid P2P systems by constructing a tree-based index overlay among directory nodes that maintain indices, according to the load and popularity of a keyword. The mathematical analysis shows that the keyword search based on semi-structured P2P overlay can improve the search performance, reducing the message traffic and maintenance costs.

关键词： tree-based index overlay keyword search fault-tolerance performance

Towards Risk Evaluation of Denial-of-Service Vulnerabilities in Security Protocols

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Journal of Computer Science & Technology 2010年第2期25卷 375-386,F0003页

作者：曹振关志陈钟 member, ieee 胡建斌唐礼勇 China Mobile Research Institute Beijing 100053 China School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Key Laboratory of High Confidence Software Technologies Ministry of Education Beijing 100871 China

Denial-of-Service （DOS） attacks are virulent to both computer and networked systems. Modeling and evaluating DoS attacks are very important issues to networked systems; they provide both mathematical foundations and theoretic guidelines to security system design. As defense against DoS has been built more and more into security protocols, this paper studies how to evaluate the risk of DoS in security protocols. First, we build a formal framework to model protocol operations and attacker capabilities. Then we propose an economic model for the risk evaluation. By characterizing the intruder capability with a probability model, our risk evaluation model specifies the ＂Value-at-Risk＂（VaR） for the security protocols. Tile ＂Value-at-Risk＂ represents how much computing resources are expected to lose with a given level of confidence. The proposed model can help users to have a better understanding of the protocols they are using, and in the meantime help designers to examine their designs and get clues of improvement. Finally we apply the proposed model to analyze a key agreement protocol used in sensor networks and identify a DoS flaw there, and we also validate the applicability and effectiveness of our risk evaluation model by applying it to analyze and compare two public key authentication protocols.

关键词： risk evaluation Denial-of-Service (DOS) Value-at-Risk (VaR)

HAG： An Energy-Proportional Data Storage Scheme for Disk Array Systems

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Journal of Computer Science & Technology 2015年第4期30卷 679-695页

作者：金培权谢希科 Christian S. Jensen 金勇岳丽华 School of Computer Science and Technology University of Science and Technology of China Hefei 230027 China Key Laboratory of Electromagnetic Space Information Chinese Academy of Sciences Hefei 230027 China Department of Computer Science Aalborg University Aalborg DK-9220 Denmark

Energy consumption has been a critical issue for data storage systems, especially for modern data centers. A recent survey has showed that power costs amount to about 50%of the total cost of ownership in a typical data center, with about 27% of the system power being consumed by storage systems. This paper aims at providing an effective solution to reducing the energy consumed by disk storage systems, by proposing a new approach to reduce the energy consumption. Differing from previous approaches, we adopt two new designs. 1） We introduce a hotness-aware and group-based system model （HAG） to organize the disks, in which all disks are partitioned into a hot group and a cold group. We only make file migration between the two groups and avoid the migration within a single group, so that we are able to reduce the total cost of file migration. 2） We use an on-demand approach to reorganize files among the disks that is based on workload change as well as the change of data hotness. We conduct trace-driven experiments involving two real and nine synthetic traces and we make detailed comparisons between our method and competitor methods according to different metrics. The results show that our method can dynamically select hot files and disks when the workload changes and that it is able to reduce energy consumption for all the traces. Furthermore, its time performance is comparable to that of the compared algorithms. In general, our method exhibits the best energy e？ciency in all experiments, and it is capable of maintaining an improved trade-off between performance and energy consumption.

关键词： energy-aware system file organization storage management

Providing Virtual Cloud for Special Purposes on Demand in JointCloud Computing Environment

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Journal of Computer Science & Technology 2017年第2期32卷 211-218页

作者： Dong-Gang Cao member, CCF, ieee, Bo An Pei-Chang Shi Huai-Min Wang Key Laboratory of High Confidence Software Technologies (Peking University) Ministry of Education Beijing 100871 China National Key Laboratory for Parallel and Distributed Processing National University of Defense and Technology Changsha 410073 China

Cloud computing has been widely adopted by enterprises because of its on-demand and elastic resource usage paradigm. Currently most cloud applications are running on one single cloud. However, more and more applications demand to run across several clouds to satisfy the requirements like best cost efficiency, avoidance of vender lock-in, and geolocation sensitive service. JointCloud computing is a new research initiated by Chinese institutes to address the computing issues concerned with multiple clouds. In JointCloud, users＇ diverse and dynamic requirements on cloud resources axe satisfied by providing users virtual cloud （VC） for special purposes. A virtual cloud for special purposes is in essence a user＇s specific cloud working environment having the customized software stacks, configurations and computing resources readily available. This paper first introduces what is JointCloud computing and then describes the design rationales, motivation examples, mechanisms and enabling technologies of VC in JointCloud.

关键词： cloud computing JointCloud virtual cloud (VC) cloud working environment

CCNoC:Cache-Coherent Network on Chip for Chip Multiprocessors

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Journal of Computer Science & Technology 2010年第2期25卷 257-266页

作者：王惊雷薛一波 member, CCF, ieee 王海霞李崇民汪东升 Senior member,CCF Department of Computer Science and Technology Tsinghua University Beijing 100084 China Tsinghua National Laboratory of Information Science and Technology Beijing 100084 China

As the number of cores in chip multiprocessors （CMPs） increases, cache coherence protocol has become a key issue in integration of chip multiprocessors. Supporting cache coherence protocol in large chip multiprocessors still faces three hurdles： design complexity, performance and scalability. This paper proposes Cache Coherent Network on Chip （CCNoC）, a scheme that decouples cache coherency maintenance from processors and shared L2 caches and implements it completely in network on chip to free up processors and shared L2 caches from the chore of maintaining coherency, thereby reduces design complexity of CMPs. In this way, CCNoC also improves the performance of cache coherence protocol through reducing directory access latency and enhances scalability by avoiding massive directories overhead in shared L2 caches. In CCNoC, coherence state caches and active directory caches are implemented in the network interface components of network on chip to maintain cache coherence states for blocks in L1 caches and manage directory information for recently accessed blocks in L2 caches respectively. CCNoC provides a scalable CMP framework to tackle cache coherency which is the foundation of CMP. This paper evaluates the performance of CCNoC. Experimental results show that for a 16-core system, CCNoC improves performance by 3% on average over the conventional chip multiprocessor and by 10% at best, while reduces storage overhead by 1.8% and saves directory storage by 88%, showing good scalability.

关键词： chip multiprocessor network on chip cache coherence protocol

Investigation on Suspended Stripline and End-Coupled Bandpass Filter

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Journal of Systems Engineering and Electronics 1991年第2期2卷 82-90页

作者： Jinxiong Xie, student member, ieee, and Weigan Lin, senior member, ieeeUniversity of Electronic Science and Technology of China, Chengdu 610054, China University of Electronic Science and Technology of China Chengdu 610054 China

In this paper, the variational method combined with Green's function is used to analyze the characteristics of suspended, stripline. The result is in good agreement with references. The design of mm-wave end-coupled bandpass filter with suspended substrate is discussed. The computer programs for design of suspended stripline and bandpass filter are established.

关键词： Millimeter wave Millimeter wave transmission line Millimeter wave passive component Bandpass filter Computer aided design.