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Truncation error calculation based on Richardson extrapolation for variable-step collaborative simulation

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Science china(information Sciences) 2011年第6期54卷 1238-1250页

作者： ZHAng HeMing 1 , LIAng SiLu 2 , SOng ShiJi 1 & WAng HongWei 3 1 Department of Automation, TNList, tsinghua university, beij.ng 100084, china 2 computer and information management center, tsinghua university beij.ng 100084, china 3 Engineering Design Centre, Engineering Department, Cambridge university, Cambridge CB2 1PZ, UK 1. Department of Automation TNList Tsinghua University Beijing 100084 China2. Computer and Information Management Center Tsinghua University Beijing 100084 China3. Engineering Design Centre Engineering Department Cambridge University Cambridge CB2 1PZ UK

Collaborative simulation is an effective approach to performing simulation analysis for complex systems by integrating models developed for different engineering disciplines. Collaborative simulation issues include the modeling of coupled multidisciplinary systems, and the simulation running time integration of these models that are solved parallelly. Estimation of the local truncation error of coupling models is the key to solve multidisciplinary collaborative simulation problem, which is actually used to restrict the simulation step. This paper presents a variable-step method based on Richardson extrapolation for calculating the local truncation error to solve collaborative simulation problem of multidisciplinary coupling models. Formulas for estimating the local truncation error are derived through theoretical analysis by using integration methods and interpolation technologies, respectively. The simulation experiments are illustrated to validate the accuracy and efficiency of proposed collaborative simulation algorithm in comparison with the usual combinative algorithm.

关键词： multidisciplinary systems collaborative simulation variable-step algorithm error estimation

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, beij.ng 100084, china 2 tsinghua National Laboratory for information Science and Technology, tsinghua university, beij.ng 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

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,beij.ng 100084,china 2 Network Research center,tsinghua university,beij.ng 100084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beij.ng 100084,china 1. Department of computer Science 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

Internet has become the most important information infrastructure supporting modern socio-economic development, social progress and technological Innovation. Invented 30 years ago, today Internet is facing increasingly severe technical challenges. This paper introduces the progress of the major international 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

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, beij.ng 100084, china 2tsinghua National Laboratory for information Science and Technology, beij.ng 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 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,beij.ng 100084,china 2 Department of computer Science and Technology,tsinghua university,beij.ng 100084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beij.ng 100084,china 1. Network Research center Tsinghua University Beijing 100084 China 3. tsinghua National Laboratory for information Science and Technology (TNList) Beijing 100084 China 2. Department of computer Science and Technology Tsinghua University Beijing 100084 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)

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,tsinghua university,beij.ng 100084,china 2 Network Research center,tsinghua university,beij.ng 100084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beij.ng 100084,china 1. Department of computer Science and Technology Tsinghua University Beijing 100084 China 3. ]tsinghua National Laboratory for information Science and Technology (TNList) Beijing 100084 China 2. Network Research center Tsinghua University Beijing 100084 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

ENTROPY,information,NOISE-STUDIES ON SYSTEM EVOLUTION

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Systems Science and Systems Engineering 2003年第1期12卷 2-12页

作者： Weimin ZHEngSchool of Economics and management tsinghua university. beij.ng 100084, china School of Economics and management Tsinghua University

Universe, ecosystem, social system, etc. are evolving systems. The evolving processes of these systems have gradual small changes and rapid drastic changes with uncertainties under the constraints of environment. Systems, as a whole, are evolving toward complexity, diversity and variety with fluctuations and jumps. New order emerges from 'mutations'. The evolution is both chance-dependent and path-dependent. In this paper three basics: entropy, information and noise are emphasized with regard to system evolution which is a field that can give people wisdom to solve system problems with domain knowledge.

关键词： Entropy information noise

The structural analysis of fuzzy measures

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Science china(information Sciences) 2011年第1期54卷 38-50页

作者： ZHAng Ling1,ZHAng Bo2 & ZHAng YanPing1 1 computer Science College,Anhui university,Hefei 230039,china 2State Key Lab of Intelligent Technology & Systems tsinghua National Lab for information Science & Technology information Science & Technology College,computer Science & Technology,tsinghua university,beij.ng 100084,china 1. computer Science College Anhui University Hefei 230039 China2. State Key Lab of Intelligent Technology & Systems tsinghua National Lab for information Science & Technology information Science & Technology College Computer Science & Technology Tsinghua University Beijing 100084 China

From quotient space based granular computing theory we explore the fuzzy measures of fuzzy sets. Based on the structural analysis of fuzzy sets,we present an"isotropism"*** this assumption we achieved the following insights:(1)the uniqueness of a fuzzy measure being isotropic on a finite complete semi-ordered set;(2)the necessary and suffcient condition of the isomorphism for fuzzy measure functions in fuzzy mathematics;(3)the necessary and suffcient condition that fuzzy measures have fuzzy and granular monotonicity;(4)under a certain assumption,the analytic expression for fuzzy *** results clarify the relationship between fuzzy measures and granular computing,reveal the essence of fuzzy measures,and provide a simple way of constructing fuzzy measures.

关键词： quotient space fuzzy set fuzzy measure rough set structural analysis

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, beij.ng 100084, china 2 tsinghua National Laboratory for information Science and Technology, tsinghua university, beij.ng 100084, china 3 Research Institute of information Technology (RIIT), tsinghua university, beij.ng 100084, china Department of Automation Tsinghua University Beijing 100084 China tsinghua National Laboratory for information Science and Technology Tsinghua University Beijing 100084 China Research Institute of information Technology (RIIT) Tsinghua University Beijing 100084 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