1. The Chugoku Electric Power Co., 4-33 Komachi, Naka-ku, Hiroshima 7308701, Japan
2. Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba 2701194, Japan
3. Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 1528552, Japan