1. Department of Electrical and Mechanical Engineering Nagoya Institute of Technology Gokiso, Showa Nagoya 466-8555 Japan
2. Advanced Power Electronics Research Center National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba West 5E 16-1 Onogawa Tsukuba Ibaraki 305-8569 Japan
3. Frontier Research Institute of Materials Science Nagoya Institute of Technology Gokiso, Showa Nagoya 466-8555 Japan