1. College of Information Science and Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kasatsu, Shiga 525-8577, Japan and Institute for Computational Science and Engineering, Ocean University of China, Shandong, People's Republic of China
2. Faculty of Engineering, University of the Ryukyus, Okinawa 903-0213, Japan
3. Okinawa National College of Technology, Okinawa, Japan