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A sensitive indicator of regional space-time accessibility

Annals of GIS 2010年第3期16卷 155-164页

作者： Fang, Zhixiang Shaw, Shih-Lung Li, Qingquan State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan Hubei China Engineering Research Center for Spatio-Temporal Data Smart Acquisition and Application Ministry of Education of China Wuhan Hubei China Department of Geography University of Tennessee Knoxville TN United States

The concept of accessibility needs to take into account factors like individual needs, preferences, and abilities as well as transportation, land use, and finances. This article proposes a sensitive space-time accessibility indicator from a regional perspective. This indicator, representing cumulative available activity time with a regional context, is different from both traditional accessibility measures (e.g., gravity-based accessibility, cumulative accessibility, utility-based accessibility, and so on) and previous concepts of individual space-time accessibility. The major advantage of this indicator is its sensitivity to the location of the anchor point, the transportation network, the distribution of activity sites over the whole region, and certain individual needs such as minimum activity times and activity time budgets. Several examples are worked to demonstrate these sensitivities and an innovative accessibility pattern which was previously unknown. This indicator should be helpful for planning agencies to assess urban environmental patterns and for business owners to evaluate potential business locations. © 2010 Taylor & Francis.

关键词： Region Space-time accessibility Spatial pattern Time-geography

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An Efficient Method for Calculating Qualitative Spatial Relations

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电子学报(英文版) 2009年第1期18卷 42-46页

作者： WANG Shengsheng LIU Dayou College of Computer Science and Technology Key Laboratory of Symbolic Computing and Knowledge Engineering of Ministry of Education Jilin University Changchun 130012 China

Qualitative spatial relations are widely used in geospatial ontologies, geospatial (semantic) web services, spatial description logics etc. Methodology to obtain qualitative spatial relations (especially complex spatial relations) from Geographical information system (GIS) has not been studied in previous literatures. An efficient method for calculating complex qualitative spatial relations is discussed here. First, the multi-granularities approximate representation of spatial objects is proposed, it is designed for GIS object types (such as polygon), and requires less process time. Then some algorithms for calculating complex spatial relations based on the multi-granularities approximate representation are given. Finally, this method is implemented and used to obtain topology and direction relations from world map. The analysis and test results show that this method supports complex and integrated spatial relations and requires less process time than traditional method. This method is suitable for obtaining spatial relations for geospatial ontologies and other applications.

关键词：空间关系计算地理信息系统地理本体信息系统设计网络服务描述逻辑空间对象

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A NEW CASCADING FAILURE MODEL WITH DELAY TIME IN CONGESTED COMPLEX NETWORKS

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Journal of Systems Science and Systems engineering 2009年第3期18卷 369-381页

作者： Jian WANG Yanheng LIU Yu JIAO College of Computer Science and Technology Jilin University Changchun 130012 China Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University Changchun 130012 China

Cascading failures often occur in congested complex networks. Cascading failures can be expressed as a three-phase process： generation, diffusion, and dissipation of congestion. Different from the betweenness centrality, a congestion function is proposed to represent the extent of congestion on a given node. Inspired by the restart process of a node, we introduce the concept of ＂delay time,＂ during which the overloaded node Cannot receive or forward any traffic, so an intergradation between permanent removal and nonremoval is built and the flexibility of the presented model is demonstrated. Considering the connectivity of a network before and after cascading failures is not cracked because the overloaded node are not removed from network permanently in our model, a new evaluation function of network efficiency is also proposed to measure the damage caused by cascading failures. Finally, we investigate the effects of network structure and size, delay time, processing ability, and traffic generation speed on congestion propagation. Cascading processes composed of three phases and some factors affecting cascade propagation are uncovered as well.

关键词： Complex networks cascading failures congestion effects propagation model

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Statistical properties of visibility graph of energy dissipation rates in three-dimensional fully developed turbulence

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Physica A: Statistical Mechanics and its Applications 2010年第13期389卷 2675-2681页

作者： Chuang Liu Wei-Xing Zhou Wei-Kang Yuan School of Business East China University of Science and Technology Shanghai 200237 China Engineering Research Center of Process Systems Engineering (Ministry of Education) East China University of Science and Technology Shanghai 200237 China Research Center for Econophysics East China University of Science and Technology Shanghai 200237 China School of Science East China University of Science and Technology Shanghai 200237 China Research Center on Fictitious Economics & Data Science Chinese Academy of Sciences Beijing 100080 China State Key Laboratory of Chemical Engineering East China University of Science and Technology Shanghai 200237 China

We study the statistical properties of complex networks constructed from time series of energy dissipation rates in three-dimensional fully developed turbulence using the visibility algorithm. The degree distribution is found to have a power-law tail with the tail exponent α = 3.0 . The exponential relation between the number of the boxes N B and the box size l B based on the edge-covering box-counting method illustrates that the network is not self-similar, which is also confirmed by the hub-hub attraction according to the visibility algorithm. In addition, it is found that the skeleton of the visibility network exhibits excellent allometric scaling with the scaling exponent η = 1.163 ± 0.005 .

关键词： Turbulence Energy dissipation rate Visibility graph Degree distribution Self-similarity Allometric scaling

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Deriving all minimal consistency-based diagnosis sets using SAT solvers

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Progress in Natural Science:Materials International 2009年第4期19卷 489-494页

作者： Xiangfu Zhao a,b, Liming Zhang a,b, Dantong Ouyang a,b, Yu Jiao a,b a key laboratory of Symbolic Computation and knowledge engineering of ministry of education, Jilin University, Changchun 130012, China b School of Computer Science and Technology, Jilin University, Changchun 130012, China [a]Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University Changchun 130012 China [b]School of Computer Science and Technology Jilin University Changchun 130012 China

In this paper, a novel method is proposed for judging whether a component set is a consistency-based diagnostic set, using SAT solv- ers. Firstly, the model of the system to be diagnosed and all the observations are described with conjunctive normal forms (CNF). Then, all the related clauses in the CNF files to the components other than the considered ones are extracted, to be used for satisfiability checking by SAT solvers. Next, all the minimal consistency-based diagnostic sets are derived by the CSSE-tree or by other similar algorithms. We have implemented four related algorithms, by calling the gold medal SAT solver in SAT07 competition – RSAT. Experimental results show that all the minimal consistency-based diagnostic sets can be quickly computed. Especially our CSSE-tree has the best effciency for the singleor double-fault diagnosis.

关键词： Conjunctive normal form Consistency-based diagnosis Model-based diagnosis SAT solver

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Computing minimal diagnosis with binary decision diagrams algorithm

Computing minimal diagnosis with binary decision diagrams al...

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6th International Conference on Fuzzy Systems and knowledge Discovery, FSKD 2009

作者： Wang, Kun Li, Zhan-Shan Ai, Yang Zhang, Yong-Gang Key Laboratory of Symbolic Computation Knowledge Engineering for Ministry of Education Jilin University Jilin Changchun China

ISBN: (纸本)9780769537351

In this paper we propose an algorithm of computing minimal diagnosis based on BDD (Binary Decision Diagram). First we give the concept of disjunction equations, and map the collection of conflict sets into disjunction equations, then we compile the system into a BDD, further we compute the minimal hitting sets by solving the BDD and minimizing hitting sets. The reliability and completeness of the algorithm are proved. Variable ordering and construct controlling of BDD are used to further reduce the size of final BDD and the number of non-minimal hitting sets to be generated. The efficiency of computing minimal hitting sets is highly improved. Experimental results show that the algorithm isn't restricted by the structure of system and conflict sets, compared with three algorithms in the references, it can generate all the minimal hitting sets, and it works well in random circumstances. © 2009 IEEE.

关键词： Binary decision diagrams

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Using link-based content analysis to measure document similarity effectively

Using link-based content analysis to measure document simila...

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Joint International Conference on Advances in data and Web Management, APWeb/WAIM 2009

作者： Li, Pei Li, Zhixu Liu, Hongyan He, Jun Du, Xiaoyong Key Labs of Data Engineering and Knowledge Engineering Ministry of Education China School of Information Renmin University of China Beijing China Department of Management Science and Engineering Tsinghua University Beijing China

ISBN: (纸本)9783642006715

Along with a massive amount of information being placed online, it is a challenge to exploit the internal and external information of documents when assessing similarity between them. A variety of approaches have been proposed to model the document similarity based on different foundations, but usually they are not applicable for combining internal and external information. In this paper, we introduce a link-based method into content analysis, which is based on random walk on graphs. By defining similarity as the meeting probability of two random surfers, we propose a computational model for content analysis, which can also be integrated with external information of documents. Empirical study shows that our method achieves good accuracy, acceptable performance and fast convergent rate in multi-relational document similarity measuring. © Springer-Verlag Berlin Heidelberg 2009.

关键词： Computers

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Exploiting the block structure of link graph for efficient similarity computation

Exploiting the block structure of link graph for efficient s...

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13th Pacific-Asia Conference on knowledge Discovery and data Mining, PAKDD 2009

作者： Pei, Li Yuanzhe, Cai Hongyan, Liu Jun, He Xiaoyong, Du Key Labs of Data Engineering and Knowledge Engineering Ministry of Education China School of Information Renmin University of China Beijing China Department of Management Science and Engineering Tsinghua University Beijing China

ISBN: (纸本)3642013066

In many real-world domains, link graph is one of the most effective ways to model the relationships between objects. Measuring the similarity of objects in a link graph is studied by many researchers, but an effective and efficient method is still expected. Based on our observation of link graphs from real domains, we find the block structure naturally exists. We propose an algorithm called BlockSimRank, which partitions the link graph into blocks, and obtains similarity of each node-pair in the graph efficiently. Our method is based on random walk on two-layer model, with time complexity as low as O(n4/3) and less memory need. Experiments show that the accuracy of BlockSimRank is acceptable when the time cost is the lowest. © Springer-Verlag Berlin Heidelberg 2009.

关键词： Artificial intelligence

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Deprank: A probabilistic measure of dependence via heterogeneous links

Deprank: A probabilistic measure of dependence via heterogen...

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Joint International Conference on Advances in data and Web Management, APWeb/WAIM 2009

作者： Li, Pei Hu, Bo Liu, Hongyan He, Jun Du, Xiaoyong Key Labs of Data Engineering and Knowledge Engineering Ministry of Education China School of Information Renmin University of China Beijing China Department of Management Science and Engineering Tsinghua University Beijing China

ISBN: (纸本)9783642006715

Dependence is a common relationship between objects. Many works have paid their attentions on dependence, but many of them mainly focus on constructing or exploiting dependence graphs on some specific domain. In this paper, we give a generic definition of dependence and make equivalence to the situation of graphs, and propose an algorithm called DepRank, which quantifies the dependence degree of a node pair based on probabilities of all dependence paths. Empirical study shows that DepRank method has reasonable results and maintains a well balance between accuracy and efficiency. © Springer-Verlag Berlin Heidelberg 2009.

关键词： Artificial intelligence

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AutoPCS: A phrase-based text categorization system for similar texts

AutoPCS: A phrase-based text categorization system for simil...

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Joint International Conference on Advances in data and Web Management, APWeb/WAIM 2009

作者： Li, Zhixu Li, Pei Wei, Wei Liu, Hongyan He, Jun Liu, Tao Du, Xiaoyong Key Labs of Data Engineering and Knowledge Engineering Ministry of Education China School of Information Renmin University of China Beijing China Department of Management Science and Engineering Tsinghua University Beijing China

ISBN: (纸本)9783642006715

Nearly all text classification methods classify texts into predefined categories according to the terms appeared in texts. State-of-the-art of text classification prefer to simplely take a word as a term since it performs good on some famous datasets;some experts even pointed out that phrases don't improve or improve only marginally the classifiction accuracy. However, we found out that this is not always true when we try to categorize texts about similar topics in the same domain. With words only we can not categorize those texts effectively since they nearly share the same word set. Then we suppose the results might be improved if we also use phrases as terms. To testify our supposition, we propose our own phrase extraction way as well as select proper feature selection method and classifier by conducting experimental study on a data set which comes from paper abstracts in the field of databases. Accordingly, we also develop a system called AutoPCS which can be used to help experts in choosing relevant topics for newly coming papers from a predefined topic list only by their abstracts. © Springer-Verlag Berlin Heidelberg 2009.

关键词： Classification (of information)

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