Papers - Kobayashi, Kei

Parallel matching for ranking all teams in a tournament

Kei Kobayashi, Hideki Kawasaki, Akimichi Takemura

ADVANCES IN APPLIED PROBABILITY (APPLIED PROBABILITY TRUST)  38 ( 3 ) 804 - 826 2006.09

Accepted,  ISSN  00018678

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We propose a simple and efficient scheme for ranking all teams in a tournament where matches can be played simultaneously. We show that the distribution of the number of rounds of the proposed scheme can be derived using lattice path counting techniques used in ballot problems. We also discuss our method from the viewpoint of parallel sorting algorithms.

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Information criteria for support vector machines

Kei Kobayashi, Fumiyasu Komaki

IEEE TRANSACTIONS ON NEURAL NETWORKS (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC)  17 ( 3 ) 571 - 577 2006.05

Accepted,  ISSN  10459227

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This paper presents kernel regularization information criterion (KRIC), which is a new criterion for tuning regularization parameters in kernel logistic regression (KLR) and support vector machines (SVMs). The main idea of the KRIC is based on the regularization information criterion (RIC). We derive an eigenvalue equation to calculate the KRIC and solve the problem. The computational cost for parameter tuning by the KRIC is reduced drastically by using the Nystrom approximation. The test error rate of SVMs or KLR with the regularization parameter tuned by the KRIC is comparable with the one by the cross validation or evaluation of the evidence. The computational cost of the KRIC is significantly lower than the one of the other criteria.

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Approximation of multiplicatively weighted crystal growth voronoi diagram and its application

Kei Kobayashi, Kokichi Sugihara

Electronics and Communications in Japan, Part III: Fundamental Electronic Science (English translation of Denshi Tsushin Gakkai Ronbunshi) (Electronics and Communications in Japan, Part III: Fundamental Electronic Science (English translation of Denshi Tsushin Gakkai Ronbunshi))  85 ( 6 ) 21 - 31 2002.06

Accepted,  ISSN  10420967

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A multiplicatively weighted crystal growth Voronoi diagram is a type of planar segmentation diagram that can result when crystals grow at different speeds from several points. In this paper, we first define a multiplicatively weighted crystal growth Voronoi diagram, discuss its properties, and find the analytic solution for the simple case. The approximate solution method for the complex case is constructed by using a difference method for partial differential equations called the fast marching method. Then the multiplicatively weighted crystal growth Voronoi diagram is used to construct a technique for optimum path planning of competing mobile robots. © 2002 Scripta Technica, Electron. Comm. Jpn.

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Crystal Voronoi diagram and its applications

Kei Kobayashi, Kokichi Sugihara

Future Generation Computer Systems (Future Generation Computer Systems)  18 ( 5 ) 681 - 692 2002.04

Accepted,  ISSN  0167739X

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This paper studies the multiplicatively weighted crystal-growth Voronoi diagram, which describes the partition of the plane into crystals with different growth speeds. This type of the Voronoi diagram is defined, and its basic properties are investigated. The analytic equation describing the boundary curve is given for a simple case. For the general case, an approximation algorithm is proposed. This algorithm is based on a finite-difference method, called a fast marching method, for solving a special type of a partial differential equation. The proposed algorithm is applied to the planning of a collision-free path for a robot avoiding enemy attacks. © 2002 Elsevier Science B.V. All rights reserved.

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Crystal Voronoi Diagram and Its Applications to Collision-Free Paths

Kei KOBAYASHI, Kokichi Sugihara

Computational Science ICCS2001 (Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics))  2073   738 - 747 2001

Accepted,  ISSN  03029743

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This paper studies the multiplicatively weighted crystal- growth Voronoi diagram, which describes the partition of the plane into crystals with different growth speeds. This type of the Voronoi diagram is defined, and its basic properties are investigated. An approximation algorithm is proposed. This algorithm is based on a finite difference method, called a fast marching method, for solving a special type of a partial differential equation. The proposed algorithm is applied to the planning of a collision-free path for a robot avoiding enemy attacks. © 2001 Springer-Verlag Berlin Heidelberg.

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乗法重みつき結晶成長ボロノイ図の近似構成法とその応用

小林 景, 杉原 厚吉

電子情報通信学会論文誌A J83-A ( 12 ) 1495 - 1504 2000

Accepted