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Eurographics Symposium on Rendering 2011

作者： Chen, Jiating Wang, Bin Yong, Jun-Hai School of Software Tsinghua University Beijing China Department of Computer Science and Technology Tsinghua University Beijing China Key Laboratory for Information System Security Ministry of Education of China Beijing China Tsinghua National Laboratory for Information Science and Technology Beijing China

This paper presents an improvement to the stochastic progressive photon mapping (SPPM), a method for robustly simulating complex global illumination with distributed ray tracing effects. Normally, similar to photon mapping and other particle tracing algorithms, SPPM would become inefficient when the photons are poorly distributed. An inordinate amount of photons are required to reduce the error caused by noise and bias to acceptable levels. In order to optimize the distribution of photons, we propose an extension of SPPM with a Metropolis-Hastings algorithm, effectively exploiting local coherence among the light paths that contribute to the rendered image. A well-designed scalar contribution function is introduced as our Metropolis sampling strategy, targeting at specific parts of image areas with large error to improve the efficiency of the radiance estimator. Experimental results demonstrate that the new Metropolis sampling based approach maintains the robustness of the standard SPPM method, while significantly improving the rendering efficiency for a wide range of scenes with complex lighting. © 2011 The Author(s).

关键词： Photons

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Answering contextual questions based on ontologies and question templates

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Frontiers of computer science 2011年第4期5卷 405-418页

作者： Dongsheng WANG Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China Department of Computer Science Jiangsu University of Science and Technology Zhenjiang 212003 China

Contextual question answering （CQA）, in which user information needs are satisfied through an interactive question answering （QA） dialog, has recently attracted more research attention. One challenge is to fuse contextual information into the understanding process of relevant questions. In this paper, a discourse structure is proposed to maintain semantic information, and approaches for recognition of relevancy type and fusion of contextual information according to relevancy type are proposed. The system is evaluated on real contextual QA data. The results show that better performance is achieved than a baseline system and almost the same performance as when these contextual phenomena are resolved manually. A detailed evaluation analysis is presented.

关键词： Contextual question answering （CQA）,ontology question templates

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Fuzzy tracking control design for hypersonic vehicles via T-S model

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science China(information sciences) 2011年第3期54卷 521-528页

作者： GAO DaoXiang 1 & SUN ZengQi 2 1 School of technology, Beijing Forestry University, Beijing 100083, China 2 State key laboratory of Intelligent technology and system, department of computer science and technology, Tsinghua University, Beijing 100084, China 1. School of Technology Beijing Forestry University Beijing 100083 China2. State Key Laboratory of Intelligent Technology and System Department of Computer Science and Technology Tsinghua University Beijing 100084 China

The main focus of this paper is on designing a T-S fuzzy controller for the hypersonic vehicle. The longitudinal dynamics of the vehicle are studied using time-scale decomposition to reduce the complexity of T-S modeling. The dynamic inversion with PI control technique is applied for the slow dynamics to derive the flight path angle command and throttle setting by taking the pilot altitude and velocity command as its inputs. The T-S fuzzy controller is designed for the fast dynamics to derive the elevator deflection to track the flight path angle command. The discrepancy between the T-S model and real vehicle model is considered by using sliding mode control for the system stability. Simulation results are included to show the effectiveness of the controller.

关键词： fuzzy control T-S model sliding mode control hypersonic vehicle

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A general framework for network survivability testing and evaluation

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Journal of Networks 2011年第6期6卷 831-841页

作者： Wang, Chunlei Ming, Liang Zhao, Jinjing Wang, Dongxia Tsinghua University Department of Computer Science Beijing China National Key Laboratory of Science and Technology on Information System Security Beijing China

The survivability of network is of vital importance with respect to the normal operation of information infrastructure. The current research works in the area of network survivability generally aimed at the definitions and quantifications of specific survivability attributes or metrics for distinct network objects. Unfortunately, there is a lack of research concerning how to model, test and evaluate the survivability of network in a consistent manner, and it is helpful to the unification of network survivability testing and evaluation and the promotion of related research works in the area of network survivability. Furthermore, the requirements for network survivability testing and evaluation are variable among different application domains. Therefore, a flexible mechanism to support the customizable testing and evaluation of network survivability is needed. In this paper, we propose a unified framework for network survivability testing and evaluation which is extensible and customizable. The customization method of network survivability measurement model and the general process of network survivability testing and evaluation are analyzed in detail. The testing of network survivability is performed based upon specific network survivability measurement model, and the associated test scheme containing a set of test cases are generated. The evaluation of network survivability is performed based upon the quantification results of network survivability metrics, and multiple criteria decision making method is utilized to evaluate network survivability. The experimental results show the generality and practicability of the framework and the effectiveness of proposed network survivability test model and evaluation method. © 2011 ACADEMY PUBLISHER.

关键词： Decision making

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An example-driven symbol recognition approach based on key features in engineering drawings

An example-driven symbol recognition approach based on key f...

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12th International Conference on computer-Aided Design and computer Graphics, CAD/Graphics 2011

作者： Guo, Tiantian Zhang, Hui Wen, Yamei School of Software Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

In this paper, we present an example-driven symbol recognition algorithm based on its key features in CAD engineering drawings. When user provides an example of a specific symbol, the input symbol is analyzed and its features are extracted automatically. Based on the relation representation, the constrained tree with key feature priority can be established for this type of symbol. By this means, the symbol library can be built and expanded automatically in order to handle variety engineering drawings. In the next stage of the recognition processes, we first locate the key feature nodes in drawings, and then find other elements around which satisfy the topology structure of constrained tree. If all the elements and constrains in the tree are found, the symbol object will be recognized. Because of the accurate position, unnecessary matching calculations are greatly reduced. Experimental results validate that our approach is effective. © 2011 IEEE.

关键词： computer aided design

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Performance Improvement of the LM Device and Its Application to Precise Measurement of Motion Trajectories within a Small Range with a Machining Centre

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Modern Mechanical Engineering 2012年第3期2卷 71-85页

作者： Hua Qiu Yong Yue Akio Kubo Chao Lin Kai Cheng Dehong Huo Dayou Li 1Department of Mechanical Engineering Faculty of Engineering Kyushu Sangyo University Fukuoka City Japan Advanced Manufacturing and Enterprise Engineering Department School of Engineering and Design Brunel University Uxbridge UK Department of Computer Science and Technology University of Bedfordshire Luton UK Department of Mechanical Engineering Faculty of Engineering Kyushu Sangyo University Fukuoka City Japan Product Design and Engineering Department School of Engineering and Information Sciences Middlesex University London UK State Key Laboratory of Mechanical Transmission Chongqing University Chongqing China

In order to apply the LM device previously developed to precisely measuring small motion trajectories located on the different motion planes, three major improvements are successfully performed under the condition of completely maintaining the advantages of the device. These improvements include 1) development of a novel connection mechanism to smoothly attach the device to the spindle of a machining centre;2) employment of a new data sampling method to achieve a high sampling frequency independent of the operating system of the control computer;and 3) proposal of a set-up method to conveniently install the device on the test machining centre with respect to different motion planes. Practical measurement experiment results with the improved device on a machining centre sufficiently demonstrate the effectiveness of the improvements and confirm several features including a very good response to small displacement close to the resolution of the device, high precision, repeatability and reliance. Moreover, based on the measurement results for a number of trajectories for a wide range of motion conditions, the error characteristics of small size motions are systematically discussed and the effect of the movement size and feed rate on the motion accuracy is verified for the machining centre tested.

关键词： Motion Accuracy Measurement Device Performance Improvement Small Size Motion Machining Centre

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Lightweight Privacy-Aware Yet Accountable Secure Scheme for SM-SGCC Communications in Smart Grid

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Tsinghua science and technology 2011年第6期16卷 640-647页

作者： Wei Ren Jun Song Yu Yang Yi Ren School of Computer Science China University of Geosciences Wuhan 430074 China Shandong Provincial Key Laboratory of Computer Network Jinan 250014 China Key Laboratory of Network and Information Attack and Defense Technology of Ministry of Education Beijing University of Posts and Telecommunications Beijing100876 China Department of Information and Communication Technology University of Agder （UiA） Grimstad Norway

Smart grid is envisioned as a critical application of cyber-physical systems and of the internet of things. In the smart grid, smart meters equipped with wireless sensors can upload meter readings （data） to smart grid control and schedule centers via the advanced metering infrastructure to improve power delivery efficiency. However, data gathered in short intervals, such as 15 minutes, will expose customers＇ detailed daily activities （for example, when they get up and when they use oven） using nonintrusive appliance load monitoring. Thus, data must be hidden to protect customers＇ privacy. However, data accountability is still required for emergency responses or to trace back suspected intrusions, even though the data is anonymous. In addition to desired security requirements, this imposes two extra tasks： Sensors in smart meters usually have resource constraints; thus, the desired security protocols have to remain lightweight in terms of computation and storage cost. Furthermore, scalability and flexibility are required since there exist vast meters. This paper presents a lightweight Privacy-aware yet Accountable Secure Scheme called PASS which guarantees privacy-aware accountability yet tackles the above challenges in the smart grid. A formal secu- rity analysis justifies that PASS can attain the security goals, while a performance analysis verifies that PASS requires few computations, and is scalable and flexible.

关键词： smart grid privacy smart meter sensor accountability

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The Modelling and Verification of PLC Program Based on Interactive Theorem Proving Tool COQ

The Modelling and Verification of PLC Program Based on Inter...

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2011 International Conference on computer science and information technology(ICCSIT 2011)

作者： Litian Xiao Mengyuan Li Ming Gu Jiaguang Sun National Laboratory for Information Science and Technology Key Laboratory for Information System Security Ministry of EducationDepartment of Computer Science and Technology School of Software Tsinghua University Beijing Special Engineering Design and Research Institute National Laboratory for Information Science and Technology Key Laboratory for Information System Security Ministry of Education Department of Computer Science and Technology School of Software Tsinghua University

COQ is an interactive theorem proving tool. The paper abstractly describes the feature of COQ, the architecture and working modes of PLC program with the example of typical PLC. It also introduces the first-order logic syntax and semantics of Intuitionistic Logic. It briefly introduces the main Gallina language syntax elements, the corresponding use methods and main theorem proving tactic on COQ. The work has modeled kernel data type and basic statements and and the denotational semantics of PLC program with Gallina. It has given the correctness proof of PLC program based on theorem proving, i.e. based on semantics function the relationship of configuration between the before codes execution and the after is proved. The main purpose is to prove whether a PLC program satisfies certain nature within a scan period.

关键词： PLC Program, Embedded system, Verification, Denotational Semantics, Theorem Proving, COQ

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Network survivability against region failure

Network survivability against region failure

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2011 IEEE International Conference on Signal Processing, Communications and Computing, ICSPCC 2011

作者： Li, Ran Wang, Xiaoliang Jiang, Xiaohong Department of Commanding Information System Xi'an Communication Institute Shaanxi China State Key Laboratory of Novel Software Technology Department of Computer Science and Technology Nanjing University China Future University Hakodate Hokkaido Japan

ISBN: (纸本)9781457708947

Communication networks are now facing more and more potential large scale region threats such as natural disaster and physical attack. Under such region failure scenarios, numerous network elements within a geographically correlated region may be simultaneously destroyed, resulting a dramatical compromise or even breakdown of overall network connectivity. In this paper, we study the network survivability against a random region failure, which is modeled as a circular cut residing on the network. For a network adopting the cost effective multiple path routing mechanism, we examine how the network throughput performance degrades with region failure under the region-disjoint and node-disjoint routing constraints. The corresponding traffic throughput optimization problem and linear programming formulation are also addressed. We further discuss the problem of upgrading network with the minimal cost when the link capacity is not sufficient to protect the network against region failure. © 2011 IEEE.

关键词： Cost effectiveness

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Autocorrelation of Sequences Generated by Single Cycle T-Functions

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China Communications 2011年第5期8卷 144-150页

作者：王艳胡予濮李顺波杨旸 Ministry of Education Key Laboratory of Computer Networds and Information Security Xidian University Department of Mathematics Xi'an University of Architecture and Technology

Cryptographic properties of the single cycle T-function's output sequences are *** of autocorrelation functions of the kth coordinate sequence and bounds of state output sequence are calculated *** Maximum Sidelobe Ratio(MSR) of the kth coordinate sequence and the MSR of state output sequence are given *** bounds of autocorrelation functions show that the values of autocorrelation functions are large when shifts are *** of the autocorrelations between the state output sequence and coordinate output sequence are *** autocorrelation properties demonstrate that T-functions have cryptographic weaknesses and the illustration result shows coordinate output sequences have better autocorrelation than that of state output sequences.

关键词： cryptography pseudo-random sequences autocorrelation single cycle T-function

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