1. Department of Physics, Osaka City University, Osaka 558-8585, Japan
2. NITEP, Osaka Metropolitan University, Osaka 558-8585, Japan
3. Advanced Simulation Technology of Mechanics R&D, Co. Ltd., Bunkyo, Tokyo 112-0002, Japan
4. NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan