1. Yamaguchi University, Tokiwadai, Ube, Yamaguchi 755-8611 , Japan
2. Tokyo University of Science, Katsushika-ku, Tokyo 125-8585 , Japan
3. Sanyo-Onoda City University, Sanyo-Onoda, Yamaguchi 756-0884 , Japan
4. Blue Energy Center for SGE Technology (BEST), Ube, Yamaguchi 755-8611 , Japan