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Science Letters:Model for cascading failures in congested Internet

Journal of Zhejiang University-Science A(Applied Physics & engineering) 2008年第10期9卷 1331-1335页

作者： Jian WANG Yan-heng LIU Jian-qi ZHU Yu JIAO Key Lab of Symbolic Computation and Knowledge Engineering of Ministry of Education College of Computer Science and Technology Jilin University Changchun 130012 China

Cascading failures often occur in congested networks such as the Internet. A cascading failure can be described as a three-phase process： generation, diffusion, and dissipation of the congestion. In this account, we present a function that represents the extent of congestion on a given node. This approach is different from existing fimctions based on betweenness centrality. By introducing the concept of ＇delay time＇, we designate an intergradation between permanent removal and nonremoval. We also construct an evaluation fimction of network efficiency, based on congestion, which measures the damage caused by cascading failures. Finally, we investigate the effects of network structure and size, delay time, processing ability and packet generation speed on congestion propagation. Also, we uncover the relationship between the cascade dynamics and some properties of the network such as structure and size.

关键词： Complex network Cascading failures Congestion effects Propagation model

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S-SimRank: Combining Content and Link Information to Cluster Papers Effectively and Efficiently

S-SimRank: Combining Content and Link Information to Cluster...

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4th International Conference on Advanced data Mining and Applications

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

ISBN: (纸本)9783540881919

Both Content analysis and link, analysis have its advantages in measuring relationships among documents. In this paper. we propose a new method to combine these two methods to compute the similarity of research papers so that we can do clustering of these papers more accurately. In order to improve the efficiency of similarity calculation, we develop a strategy to deal with the relationship graph separately, without affecting the accuracy. We also design an approach to assign different weights to different links to the papers, which can enhance the accuracy of similarity calculation. The experimental results conducted oil ACM data Set show that our new algorithm. S-SimRank, outperforms other algorithms.

关键词： Calculations

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The design and implementation of GML data management information system based on PostgreSQL

The design and implementation of GML data management informa...

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Geoinformatics 2008 and Joint Conference on GIS and Built Environment: Geo-Simulation and Virtual GIS Environments

作者： Zhang, Aiguo Wu, Qunyong Xu, Qifeng Key Lab. of Data Mining and Information Sharing Ministry of Education Fuzhou University Fuzhou Fujian 350002 China Institute of Surveying and Mapping Information Engineering University Zhengzhou 450052 China

ISBN: (纸本)9780819473851

GML expresses geographic information in text, and it provides an extensible and standard way of spatial information encoding. At the present time, the management of GML data is in terms of document. By this way, the inquiry and update of GML data is inefficient, and it demands high memory when the document is comparatively large. In this respect, the paper put forward a data management of GML based on PostgreSQL. It designs four kinds of inquiries, which are inquiry of metadata, inquiry of geometry based on property, inquiry of property based on spatial information, and inquiry of spatial data based on location. At the same time, it designs and implements the visualization of the inquired WKT data. © 2008 SPIE.

关键词： Information management

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Model for cascading failures in congested Internet

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2008年第10期9卷 1331-1335页

Cascading failures often occur in congested networks such as the Internet. A cascading failure can be described as a three-phase process: generation, diffusion, and dissipation of the congestion. In this account, we present a function that represents the extent of congestion on a given node. This approach is different from existing functions based on betweenness centrality. By introducing the concept of ''delay time'', we designate an intergradation between permanent removal and nouremoval. We also construct an evaluation function of network efficiency, based on congestion, which measures the damage caused by cascading failures. Finally, we investigate the effects of network structure and size, delay time, processing ability and packet generation speed on congestion propagation. Also, we uncover the relationship between the cascade dynamics and some properties of the network such as structure and size.

关键词： Complex network Cascading failures Congestion effects Propagation model

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Indexing Future Trajectories of Moving Objects in a Constrained Network

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Journal of Computer Science & Technology 2007年第2期22卷 245-251页

作者：陈继东孟小峰 School of Information Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of Education Beijing 100872 China

Advances in wireless sensor networks and positioning technologies enable new applications monitoring moving objects. Some of these applications, such as traffic management, require the possibility to query the future trajectories of the objects. In this paper, we propose an original data access method, the ANR-tree, which supports predictive queries. We focus on real life environments, where the objects move within constrained networks, such as vehicles on roads. We introduce a simulation-based prediction model based on graphs of cellular automata, which makes full use of the network constraints and the stochastic traffic behavior. Our technique differs strongly from the linear prediction model, which has low prediction accuracy and requires frequent updates when applied to real traffic with velocity changing frequently. The data structure extends the R-tree with adaptive units which group neighbor objects moving in the similar moving patterns. The predicted movement of the adaptive unit is not given by a single trajectory, but instead by two trajectory bounds based on different assumptions on the traffic conditions and obtained from the simulation. Our experiments, carried on two different datasets, show that the ANR-tree is essentially one order of magnitude more efficient than the TPR-tree, and is much more scalable.

关键词： database spatial database access methods moving objects

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CLASCN： Candidate Network Selection for Efficient Top-κ keyword Queries over databases

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Journal of Computer Science & Technology 2007年第2期22卷 197-207页

作者：张俊彭朝晖王珊聂惠静 School of Information Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of Education Beijing 100872 China Computer Science and Technology College Dalian Maritime University Dalian 116026 China

keyword Search Over Relational databases （KSORD） enables casual or Web users easily access databases through free-form keyword queries. Improving the performance of KSORD systems is a critical issue in this area. In this paper, a new approach CLASCN （Classification, Learning And Selection of Candidate Network） is developed to efficiently perform top-κ keyword queries in schema-graph-based online KSORD systems. In this approach, the Candidate Networks （CNs） from trained keyword queries or executed user queries are classified and stored in the databases, and top-κ results from the CNs are learned for constructing CN Language Models （CNLMs）. The CNLMs are used to compute the similarity scores between a new user query and the CNs from the query. The CNs with relatively large similarity score, which are the most promising ones to produce top-κ results, will be selected and performed. Currently, CLASCN is only applicable for past queries and New All-keyword-Used （NAU） queries which are frequently submitted queries. Extensive experiments also show the efficiency and effectiveness of our CLASCN approach.

关键词： relational database keyword search top-κ query candidate network

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The rewriting algorithm for disjunctive queries between peer ontologies

The rewriting algorithm for disjunctive queries between peer...

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3rd International Conference on Semantics, knowledge, and Grid, SKG 2007

作者： Qin, Biao Wang, Shan Dept. of Computer Science Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of Education Beijing 100872 China

ISBN: (纸本)0769530079

We study the problem of answering queries given a set of mappings between peer ontologies. In addition to the schema mapping between peer ontologies, there are axioms to give constraints to classes and properties. We propose a set of rules to build graphs for the axioms. Because the axioms have different properties, the generated graphs are classified into four sets. In each peer, its RDF/OWL query languages can support regular expressions. If it wants to be transitive along semantic paths in peer knowledge management systems, we must rewrite conjunctive and disjunctive queries between peers. Because conjunctive queries are well-understood, we focus on a novel algorithm to rewrite disjunctive queries along semantic paths based on the graphs. For all atoms of a disjunctive query, we consider its union as a set and find the maximum rewritings over peers through a graphical way. Finally we do extensive simulation experiments. The simulation results show our algorithm can generate more rewritings than the naive rewriting algorithm at each distance. © 2007 IEEE.

关键词： Ontology

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BASED ON SELF ORGANIZED EVOLUTIONARY ALGORITHM FOR SOLVING CONSTRAINT PROBLEM

BASED ON SELF ORGANIZED EVOLUTIONARY ALGORITHM FOR SOLVING C...

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2007中国宁波国际计算机科学与技术学术大会

作者： Zhu Lili Zhao Kong Yuan Hua Yi Rongqin Wenzhou University School of Physics & Electronic Information Suzhou Top Institute of Information Technology Key Lab.of Symbol Computation & Knowledge Engineering of the Ministry of Education College of Computer Science & Technology Jilin University

ISBN: (纸本)9780972147903

The problem of parameterization design is equivalent to the problem of solving a set of nonlinear equations *** this paper,a new optimization algorithm—self organized evolutionary algorithm(SOEA) is proposed and applied into the parameterization *** SOEA the colony is composed of the *** organizational evolutionary operators which are split operator,mergence operator and coordination operator can lead the colony to *** three kinds of operators have different functions in the *** operator limits the scale of the organization and makes sure a part of organization comes into next generation directly,which maintains the variety of the *** operator makes use of the leader's information fully and acts as a local search *** operator increases the degree of adaptability between the two organizations by the *** experiment shows that SOEA has good capability in parameterization design.

关键词： Optimal algorithm Geometric constraint solving Self organized evolutionary algorithm

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The Rewriting Algorithm for Disjunctive Queries between Peer Ontologies

The Rewriting Algorithm for Disjunctive Queries between Peer...

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2007年第三届语义和知识网格国际会议(Third International Conference on Semantics,knowledge,and Grid)(SKG 2007)

作者： Biao Qin Shan Wang Dept. of Computer Science Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of EducationBeijing 100872 China

关键词： Ontologies Resource description framework OWL Terminology database languages Connectors knowledge management Extraterrestrial measurements Computer science laboratories

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2DCMA： An Effective Maintenance Algorithm of Materialized Views in Peer data Management Systems

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Journal of Computer Science & Technology 2006年第4期21卷 503-512页

作者：覃飙王珊杜小勇 School of Information Renmin University of China Beijing 100872 P.R. China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of Education Beijing 100872 P.R. China

Update management is very important for data integration systems. So update management in peer data management systems （PDMSs） is a hot research area. This paper researches on view maintenance in PDMSs. First, the definition of view is extended and the peer view, local view and global view are proposed according to the requirements of applications. There are two main factors to influence materialized views in PDMSs. One is that schema mappings between peers are changed, and the other is that peers update their data. Based on the requirements, this paper proposes an algorithm called 2DCMA, which includes two sub-algorithms： data and definition consistency maintenance algorithm% to effectively maintain views. For data consistency maintenance, Mork＇s rules are extended for governing the use of updategrams and boosters. The new rule system can be used to optimize the execution plan. And are extended for the data consistency maintenance algorithm is based on the new rule system. Furthermore, an ECA rule is adopted for definition consistency maintenance. Finally, extensive simulation experiments are conducted in SPDMS. The simulation results show that the 2DCMA algorithm has better performance than that of Mork＇s when maintaining data consistency. And the 2DCMA algorithm has better performance than that of centralized view maintenance algorithm when maintaining definition consistency.

关键词： view maintenance peer data management system schema mapping ECA rule

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