Affiliation: | 1. Department of Computer Science and System Analysis, College of Humanities and Sciences, Nihon University, 3-25-40, Sakurajyousui, Setagaya-ku, Tokyo 156-8550, Japan;2. Division of Applied Mathematical Science, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube City 755-8611, Japan |