1. Nagasaki Research and Development Center, Mitsubishi Heavy Industries, Ltd., 1-1, Akunoura-cho, Nagasaki 850-90, Japan
2. Department of Mechanical Engineering, Ritsumeikan University, 56-1 Tojiin-kitamachi, Kita-ku, Kyoto 603, Japan
3. Department of Mechanical Engineering, Faculty of Engineering, Osaka Sangyo University, 3-1-1, Nakagaito, Daito-shi, Osaka 574, Japan