检索结果-南通市图书馆

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

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 department of computer science and technology Tsinghua University tsinghua National Laboratory for Information science and technology Tsinghua University

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

RRM:An incentive reputation model for promoting good behaviors in distributed systems

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 in china(Series F) 2008年第11期51卷 1871-1882页

作者： ZHANG Hong1,2,DUAN HaiXin1,3 & LIU Wu1,3 1 tsinghua National Laboratory for Information science and technology,tsinghua university,beijing 100084,china 2 department of computer science and technology,tsinghua university,beijing 100084,china 3 Network Research Center,tsinghua university,beijing 100084,china tsinghua National Laboratory for Information science and technology Tsinghua University department of computer science and technology Tsinghua University Network Research Center Tsinghua University

Reputation systems represent soft security mechanisms that complement traditional information security mechanisms. They are now widely used in online e-commerce markets and communities in order to stimulate good behaviors as well as to restrain adverse behaviors. This paper analyzes the limitations of the conversational reputation models and proposes an incentive reputation model called the resilient reputation model （RRM） for the distributed reputation systems. The objective of this reputation model is not only to encourage the users to provide good services and, therefore, to maximize the probability of good transaction outcomes, but also to punish those adverse users who are trying to manipulate the application systems. The simulation results indicate that the proposed reputation model （RRM） could effectively resist against the common adverse behaviors, while protecting the profits of sincere users from being blemished by those adversaries.

关键词： reputation model distributed system trust soft security

A formal method to real-time protocol interoperability testing

在线全文

学校读者我要写书评

暂无评论

science in china(Series F) 2008年第11期51卷 1723-1744页

作者： WANG ZhiLiang1,3,YIN Xia2,3 & JING ChuanMing2,3 1 Network Research Center,tsinghua university,beijing 100084,china 2 department of computer science and technology,tsinghua university,beijing 100084,china 3 tsinghua National Laboratory for Information science and technology(TNList) ,beijing 100084,china Network Research Center Tsinghua University department of computer science and technology Tsinghua University tsinghua National Laboratory for Information science and technology (TNList)

Interoperability testing is an important technique to ensure the quality of implementations of network communication protocol. In the next generation Internet protocol, real-time applications should be supported effectively. However, time constraints were not considered in the related studies of protocol interoperability testing, so existing interoperability testing methods are difficult to be applied in real-time protocol interoperability testing. In this paper, a formal method to real-time protocol interoperability testing is proposed. Firstly, a formal model CMpTIOA （communicating multi-port timed input output automata） is defined to specify the system under test （SUT） in real-time protocol interoperability testing; based on this model, timed interoperability relation is then defined. In order to check this relation, a test generation method is presented to generate a parameterized test behavior tree from SUT model; a mechanism of executability pre-determination is also integrated in the test generation method to alleviate state space explosion problem to some extent. The proposed theory and method are then applied in interoperability testing of IPv6 neighbor discovery protocol to show the feasibility of this method.

关键词： protocol testing interoperability testing real-time testing test generation timed input output automata(TIOA)

A TTCN-3-based protocol testing system and its extension

在线全文

学校读者我要写书评

暂无评论

science in china(Series F) 2008年第11期51卷 1703-1722页

作者： YIN Xia1,3,WANG ZhiLiang2,3,JING ChuanMing1,3 & SHI XinGang2,3 1 department of computer science and technology,tsinghua university,beijing 100084,china 2 Network Research Center,tsinghua university,beijing 100084,china 3 tsinghua National Laboratory for Information science and technology(TNList) ,beijing 100084,china department of computer science and technology Tsinghua University Network Research Center Tsinghua University tsinghua National Laboratory for Information science and technology (TNList)

The protocol testing technology used in the next generation Internet should satisfy some new challenges and requirements. This paper focuses on the test suite description and test implementation techniques. TTCN-3 is chosen as the test suite description language and extended in both syntax and semantics to satisfy the requirements of protocol robustness testing. PITSv3, a protocol integrated testing system based on TTCN-3, is developed, and the extensions for robustness testing are implemented. Finally, two practical test applications are presented.

关键词： protocol testing TTCN-3 PITSv3 robustness testing

在线全文

学校读者我要写书评

暂无评论

Lp shape deformation

science china(Information sciences) 2012年第5期55卷 983-993页

作者： GAO Lin1,ZHANG GuoXin 1 & LAI YuKun 2 1 department of computer science and technology,tsinghua university,beijing 100084,china 2 School of computer science and Informatics,Cardiff university,Wales CF24 3AA,UK department of computer science and technology Tsinghua University School of computer science and Informatics Cardiff University

Shape deformation is a fundamental tool in geometric *** methods consider preserving local details by minimizing some energy functional measuring local distortions in the L 2 *** strategy distributes distortions quite uniformly to all the vertices and penalizes ***,there is no unique answer for a natural deformation as it depends on the nature of the *** by recent sparse signal reconstruction work with non L 2 norm,we introduce general L p norms to shape deformation;the positive parameter p provides the user with a flexible control over the distribution of unavoidable *** with the traditional L 2 norm,using smaller p,distortions tend to be distributed to a sparse set of vertices,typically in feature regions,thus making most areas less distorted and structures better *** the other hand,using larger p tends to distribute distortions more evenly across the whole *** flexibility is often desirable as it mimics objects made up with different *** specifying varying p over the shape,more flexible control can be *** demonstrate the effectiveness of the proposed algorithm with various examples.

关键词： shape deformation Lp norm geometric modeling

Image universal steganalysis based on best wavelet packet decomposition

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 Information science and technology Institute department of computer science and technology Tsinghua University

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

Large-scale P2PVOD system:Focusing on clients

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8期54卷 1677-1690页

作者： HUANG Yan 1,XU Ke 2,LI HaiTao 2 , CAO Yang 1 & YAO Xin 1 1 Shanghai SynaCast Media Tech Co.,Ltd,Shanghai 201204,china 2 department of computer science & technology,tsinghua university,beijing 100084,china Shanghai SynaCast Media Tech Co. Ltd. department of computer science & technology Tsinghua University

Using P2P network to provide video on demand (VOD) service can support large-scale users so as to save the bandwidth cost of *** VOD must support VCR characters (drag,pause,randomly choosing watching position,etc.),building a large-scale expansion of high-performance VOD system still faces huge *** paper first presents a P2P based reference model,defines the design object,and analyzes the *** then taking PPLive demand system as an example,it gives client-based solutions,including disk cache-out strategy,memory cache prefetch strategy,maintaining relations between neighbors,task scheduling,data upload strategies and so ***-demand systems are putting into practice at present with satisfactory fluency and drag *** largest number of simultaneous online users is over 210000,and online video data is over 700. Compared with traditional client-server model,the average bandwidth saving rate of servers is 88% or more,and the bandwidth saving rate of user-number's the peak value can be up to 93%.

关键词： P2P VOD server bandwidth saving rate fluency drag delay

Predicting the behavior of large scale P2P systems by parallel discrete event simulation

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6期53卷 1109-1121页

作者： ZHENG WeiMin1,YU HongLiang1,SHI GuangYu2 & CHEN Jian2 1department of computer science and technology,tsinghua university,beijing 100084,china 2Huawei Technologies Co.,Ltd,Shenzhen 518129,china department of computer science and technology Tsinghua University Huawei Technologies Co. Ltd

P2P systems are becoming the dominator of *** systems are typically composed of thousands to millions of physical computers,which make it difficult to predict their behaviors without a large scale distributed system *** paper is an attempt to predict the behavior of large scale P2P systems by building a novel parallel simulator:AegeanSim,which provides parallel discrete event simulation of such systems on high performance server *** abstract the execution of P2P applications with a specific event model,and parallel the simulation of events in a cluster,thus expanding the simulation scale and boosting the simulation process dramatically.A 1-stage synchronization method is proposed to improve the *** event callback interface is designed to implement their application logic easily while keeping the simulator *** use AegeanSim to predict the behavior of a typical P2P system:*** comparing the simulation behavior of BT with that of related BT studies and verifying its efficiency,scalability and accuracy,we make predictions about the behavior of BT system assuming they are assaulted by different man-made system *** reasonable results are found:(1) Tracker isolation can hardly work because of its short attacking time window.(2) Limiting the bandwidth of BT may be an efficient way to control it.

关键词： P2P simulation parallel

The Relation of department Components and Activity in Spatial Information Infrastructure

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Wuhan university Journal of Natural sciences 2001年第Z1期6卷 460-466页

作者： Yi Shan zhen 1, Zhou Li zhu 1,Cheng Ji cheng 2, Li Qi 2 1.department of computer science and technology,tsinghua university, beijing 100084, china 2.Institute of Remote Sensing and Geographical Information System,Peking university,beijing 1008 department of computer science and technology Tsinghua University Beijing 100084 China

Spatial Information Infrastructure (SII) facilitates the sharing, interoperability and integration of geographical information among department components of a region or a country. The SII is developed and shared by different department components. The relation of department components is a fundament for collaborating tasks and information exchange in SII. There are two kinds of department components, one is the provider which produces geospatial data of SII, other is the consumer which uses geospatial data of SII. The consumer includes two kinds of user, one is the user which only uses and does not produce geospatial data in SII, other is the special user which not only uses but also produces geospatial data in SII. The provider includes different hierarchies corresponding to different kinds of geospatial data in SII. All providers in the hierarchies form provider actor set PA. All consumers also form consumer actor set CA. The sender recipient relation SR and SRI are defined on Cartesian product of PA and CA. Five tasks and information flow in SII demonstrate the geospatial data acquisition, information production, management, and application among department components. The tasks and their sub tasks are subdivided activities. Each activity corresponds to the relation SR or RSI. The activity along with the relation of provider and consumer forms a scheme of geographical information exchange between department components.

关键词： geographical information exchange relation activity information infrastructure