1. Department of Mechanical Engineering, Osaka City University, Sugimoto, Sumiyoshiku, Osaka 558, Japan
2. Department of Mechanical Engineering, Nagoya University, Furocho, Chikusaku, Nagoya 464-01, Japan
3. Ishikawajima System Technology Co., Ltd., Kudanminami 4-6-15, Chiyodaku, Tokyo 102, Japan