[1] Graduate School of Science and Engineering, Yamaguchi University, Tokiwadai, 2-16-1, Ube 755-8611, Japan
[2] Media and Information Technology Center, Yamaguchi University, Tokiwadai, 2-16-1, Ube 755-8611, Japan
[3] Department of Materials Science and Electronics, Graduate School of Science and Engineering, Tokyo University of Science, Yamaguchi, Sanyo Onoda 756-0884, Japan
[4] Yamaguchi Study Center, Open University of Japan, Sanyo Onoda 756-0884, Japan