Seminar:

Title: XQuery Optimization

Time/Venue:

March 8, 2004
2.00pm - 4.00pm

Meeting Room, level 2, Information Building, Renmin University of China

Spearker:Yu Wang

Abstract:XQuery is a quite young standard and many issues with respect to optimization remain unresolved. We discuss the research that has been done and some open problems along with potential solutions that are associated with the XQuery. This work will focus on three aspects of optimization in XML databases being: query rewrite, cost estimation and improved methods on query evaluation.

Bio:

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Seminar:

Title:A Novel Geometric Diagram and Its Applications in Wireless Networks

Time/Venue:

March 17, 2004
2.00pm - 4.00pm

Little boardroom, level 2, Information Building, Renmin University of China

Spearker:Guangbin Fan

Abstract:Wireless networks have a lot of geometric properties since the signal strength corresponds directly to the distance. Earlier research findings in geometry, such as Voronoi diagram, have found a lot of applications in wireless networks. In this talk, a new geometric diagram, referred to as the umbrella diagram, is proposed. The umbrella diagram is comparable to the Voronoi diagram. The Voronoi diagram deals with a set of points, whereas the umbrella diagram deals with a set of different networks. The umbrella diagram of a set of hexagonal networks is to divide the plane into regions such that the points in a region have a larger distance to one network than to the other networks. Unlike the Voronoi diagram, the regions in the umbrella diagram are not necessarily convex. The paper gives an efficient solution to compute the umbrella diagram of n networks with the same cell size and orientation. Like the Voronoi diagram, the umbrella diagram has potential to be used in many areas. To illustrate its usefulness, the talk further gives two applications in wireless networks: the optimal network deployment and the maximum base station reuse. The optimal network deployment intends to find the best position to fix the network such that the network is closest to all existing base stations. The maximum base station reuse problem is to maximize the number of base stations that can be reused under a given bound.

Bio:Prof. Guangbin Fan received the B.S. degree in Computer Science from Shandong University in 1997, the M.E. degree in Computer Applications from Renmin University of China in 2000, and the Ph.D. degree in Computer Science from the University of Alabama in 2003. Currently, he is an assistant professor with the Department of Computer and Information Science at the University of Mississippi. His research interests include wireless networks and mobile computing, data management, and computational geometry. He is a member of the IEEE and of the ACM.

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Seminar:

Title: Connected Dominating Sets in Wireless Networks

Time/Venue:中国人民大学信息楼二楼会议室

Spearker:Prof. Ding-Zhu Du, University of Texas at Dallas

Abstract:The connected dominating set plays an important role in ad hoc wireless networking. Many constructions for approximating the minimum connected dominating set have been proposed in the literature. In this talk, we explain recent progress on construction of connected dominating set

Bio:Ding-Zhu Du received his M.S. degree in 1982 from Institute of Applied Mathematics, Chinese Academy of Sciences, and his Ph.D. degree in 1985 from the University of California at Santa Barbara. He worked at Mathematical Sciences Research Institutea, Berkeley in 1985-86, at MIT in 1986-87, and at Princeton University in 1990-91. He was an associate-professor/professor at Department of Computer Science and Engineering, University of Minnesota in 1991-2005, a professor at City University of Hong Kong in 1998-1999, and a research professor at Institute of Applied Mathematics, Chinese Academy of Sciences in 1987-2002.
Currently, he is a professor at Department of Computer Science, University of Texas at Dallas, a program director for Theory of Computing in National Science Foundation, USA, and also a professor at Xi'an Jiaotong University. His research interests include combinatorial optimization, communication networks, and theory of computation.
He has published more than 160 journal papers and 40 books. He is the editor-in-chief of Journal of Combinatorial Optimization and book series on Network Theory and Applications. He is also in editorial boards of more than 15 journals. He is well-known for proving the Gilbert-Pollak conjecture on the Steiner ratio, the Derman-Leiberman-Ross conjecture on optimal consecutive 2-out-of-$n$ systems in reliability, and the global convergence of Rosen gradient projection method in nonlinear programming. In 1998, he received CSTS Prize from INFORMS (a merge of American Operations Research Society and Institute of Management Science) for research excellence in the interface between Operations Research and Computer Science. In 1996, he received the 2nd Class National Natural Science Prize in China. In 1993, he received the 1st Class Natural Science Prize from Chinese Academy of Sciences. In 1992, the proof of Gilbet-Pollak conjecture was selected by 1992 Year Book of Encyclopaedia, Britannica, as the first one among six outstanding achievements in mathematics in 1991.

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