1. Fuji Electric Co., Ltd., 1, Fuji-machi, Hino-City, Tokyo 191-8502 Japan
2. Graduate School of Materials Science, Nara Institute of Science and Technology, Takayama-cho, Ikoma, Nara 630-0192, Japan
3. Central Research Institute of Electric Power Industry (CRIEPI), 2-6-1 Nagasaka, Yokosuka 240-0196, Japan