1. Computer and Network Center, Saga University, Saga 840-8502
2. Department of Applied Mathematics and Informatics, Ryukoku University, Ohtsu 520-2194
3. Cybermedia Center, Osaka University, Toyonaka 560-0043
4. Division of Mathematical Science, City College of Mie, Tsu, Mie 514-0112
5. Department of Applied Physics, University of Tokyo, Bunkyo 113-8656