1. Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8540, Japan
2. Panasonic Corporation, 3-1-1, Yagumo-nakamachi, Moriguchi, Osaka 570-8501, Japan
3. Panasonic Corporation, 2-1-61, Shiromi, Chuo-ku, Osaka 540-6255, Japan