1. Department of Mechanical Engineering, Aichi Institute of Technology, Yachigusa, Yagusa-cho, Toyota, 470-03 Japan
2. Department of Mechanical Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464 Japan
3. Toshiba Co. Ltd., Nao, Asahi-cho, Mie-ken, 512 Japan