1. International College of Arts and Sciences, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
2. Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan
3. School of Information Science, JAIST, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan