1. Laboratory of Electrochemical Energy Conversion, Faculty of Engineering, Yamanashi University, Takeda 4‐3, Kofu 400, Japan
2. Tanaka Kikinzoku Kogyo Technical Center, Shinmachi 2‐37, Hiratsuka 254, Japan
3. Stonehart Associates, Incorporated, 17 Cottage Road, P.O. Box 1220, Madison, Connecticut 06443