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Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

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Progress in Natural science:Materials International 2007年第10期17卷 1147-1151页

作者： Liu Dan1,2., Zhang Yong3.and Long Guilu1,2.1. Key laboratory for Atomic and Molecular Nano{2.s, and Department of Physics, {2. University,{3., China 2. Center of Quantum information {2. and technology, {2. national laboratory for information {2. and technology,{3., China 3. Institute of Physics, School of {2.s, beijing University of Posts and Telecommunications, beijing 100876, China) Key laboratory for Atomic and Molecular Nanosciences Department of Physics Tsinghua University Beijing 100084 China Center of Quantum information science and {2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China Institute of Physics School of Sciences Beijing University of Posts and Telecommunications Beijing 100876 China

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ>3. namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.

关键词： Heisenberg-XY chain magnetic-current phase transition.

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, {2. University,{3., China 2.2. national laboratory for information science and technology,{3., China Department of Computer science and technology Tsinghua University Beijing China tsinghua national {2. for {3. 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

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, {2. University,{3., China 2.tsinghua national laboratory for information science and technology, {2. University,{3., China Department of Computer science and technology Tsinghua University Beijing China tsinghua national {2. for {3. science and technology Tsinghua University Beijing 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 3.%. 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

Theoretical research progress in new-generation Internet architecture

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science in China(Series F) 2008年第11期51卷 1634-1660页

作者： WU JianPing1,2.3.LIU Ying2.3.& WU Qian2.3.1 Department of Computer science,tsinghua University,{2. {3.,China 2.Network Research Center,tsinghua University,{2. {3.,China 3.tsinghua {12. laboratory for information science and technology(TNList) ,{2. {3.,China Department of Computer science Tsinghua University Beijing China Network Research Center Tsinghua University Beijing China tsinghua national {2. for {3. science and technology (TNList) Beijing China

Internet has become the most important information infrastructure supporting modern socio-economic development, social progress and technological Innovation. Invented 3. years ago, today Internet is facing increasingly severe technical challenges. This paper introduces the progress of the major inter{2. newgeneration Internet research plans; analyzes its basic characteristics and the principal contradictions during the development; detsiledly introduces the research carried out by 973.Project ＂Research of Future Internet Architecture＂ on the key scientific issues of new-generation Internet architecture and its latest research results; and looks to the future of the research-focus faced with the new situations of the basic research of new-generation Internet architecture as well as the new demands of innovative applications on Internet architecture.

关键词： new-generation Internet network architecture multi-dimension scalability

A formal method to real-time protocol interoperability testing

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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 {2.,China 2.Department of Computer {3. and technology,tsinghua University,beijing {2.,China 3.tsinghua national laboratory for information {3. and technology(TNList) ,beijing {2.,China Network Research Center Tsinghua University Beijing China tsinghua national {2. for {3. science and technology (TNList) Beijing China Department of Computer science and technology Tsinghua University Beijing China

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)

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

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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 {2. national {2. for {3. science and technology,{2. University,beijing 100084,China 2.Department of Computer science and technology,{2. University,beijing 100084,China 3.Network Research Center,{2. University,beijing 100084,China tsinghua national {2. for {3. science and technology Tsinghua University Beijing China Department of Computer science and technology Tsinghua University Beijing China Network Research Center Tsinghua University Beijing China

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

Real-time reliability prediction for dynamic systems with both deteriorating and unreliable components

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science in China(Series F) 2009年第11期52卷 2234-2246页

作者： XU ZhengGuo1,2. JI YinDong2.3.& ZHOU DongHua1,2. 1 Department of Automation, tsinghua University,{2., China {2., tsinghua University,{2., China 3.Research Institute of information technology (RIIT), tsinghua University,{2., China Department of Automation Tsinghua University Beijing China tsinghua national {2. for {3. science and technology Tsinghua University Beijing China Research Institute of information technology (RIIT) Tsinghua University Beijing China

As an important technology for predictive maintenance, failure prognosis has attracted more and more attentions in recent years. Real-time reliability prediction is one effective solution to failure prognosis. Considering a dynamic system that is composed of normal, deteriorating and unreliable components, this paper proposes an integrated approach to perform real-time reliability prediction for such a class of systems. For a deteriorating component, the degradation is modeled by a time-varying fault process which is a linear or approximately linear function of time. The behavior of an unreliable component is described by a random variable which has two possible values corresponding to the operating and malfunction conditions of this component. The whole proposed approach contains three algorithms. A modified interacting multiple model particle filter is adopted to estimate the dynamic system＇s state variables and the unmeasurable time-varying fault. An exponential smoothing algorithm named the Holt＇s method is used to predict the fault process. In the end, the system＇s reliability is predicted in real time by use of the Monte Carlo strategy. The proposed approach can effectively predict the impending failure of a dynamic system, which is verified by computer simulations based on a three-vessel water tank system.

关键词： reliability failure prognostics dynamic systems fault prediction particle filtering interacting multiple model exponential smoothing,predictive maintenance

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

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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,{2. University,{3. 100084,China 2.Network Research Center,{2. University,{3. 100084,China 3.{2. national laboratory for information science and technology(TNList) ,{3. 100084,China Department of Computer science and technology Tsinghua University Beijing China tsinghua national {2. for {3. science and technology (TNList) Beijing China Network Research Center Tsinghua University Beijing China

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

Building a next generation Internet with source address validation architecture

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science in China(Series F) 2008年第11期51卷 1681-1691页

作者： WU JianPing1,3.REN Gang1,3.& LI Xing2.3.1 Department of Computer science,tsinghua University,{2. {3.,China 2.Department of Electronic Engineering,tsinghua University,{2. {3.,China 3.tsinghua {12. laboratory for information science and technology(TNList) ,{2. {3.,China Department of Computer science Tsinghua University Beijing China tsinghua national {2. for {3. science and technology (TNList) Beijing China Department of Electronic Engineering Tsinghua University Beijing China

The IP packet forwarding of current Internet is mainly destination based. In the forwarding process, the source IP address is not checked in most *** causes serious security, management and accounting problems. Based on the drastically increased IPv6 address space, a ＂source address validation architecture＂（SAVA） is proposed in this paper, which can guarantee that every packet received and forwarded holds an authenticated source IP address. The design goals of the architecture are lightweight, loose coupling, ＂multi-fence support＂ and incremental deployment. This paper discusses the design and implementation for the architecture, including inter-AS, intra-AS and local subnet. The performance and scalability of SAVA are described. This architecture is deployed into the CNGI-CERNET2.infrastructure a large-scale native IPv6 backbone network of the China Next Generation Internet project. We believe that the SAVA will help the transition to a new, more secure and dependable Internet.

关键词： IP source address validation network architecture network security