1. Energy Conversion Research Center, Department of Mechanical Engineering, Doshisha University, Tatara, Kyotanabe-shi, Kyoto Prefecture 610-0321, Japan e-mail:
2. Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi Prefecture 466-8555, Japan e-mail: