1. Computer and Network Center, Saga University, Saga 840-8502
2. Cybermedia Center, Osaka University, Toyonaka, Osaka 560-0043
3. Department of Physics and Earth Sciences, University of Ryukyus, Okinawa 903-0213
4. Department of Aeronautics and Astronautics, University of Tokyo, Tokyo 113-8656
5. Computing Research Center, KEK, Tsukuba, Ibaraki 305-0801
6. Graduate School of Information Science, Nagoya University, Nagoya 464-8601
7. Department of Applied Physics, University of Tokyo, Tokyo 113-8656