1. Department of Aeronautics and Space Engineering, Tohoku University, Sendai 980-77, Japan
2. Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka 240-01, Japan
3. Toshiba Corporation, Heavy Apparatus Engineering Laboratory, 2-4 Suehiro-cho, Tsurumi-ku, Yokohama 230, Japan