1. LEO Business, Kobelco Research Institute, Inc., 1-5-5 Tahatsukadai, Nishiku, Kobe 651-2271, Japan
2. Department of Electrical and Electronics Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
3. Production Systems Research Laboratory, Kobe Steel, Ltd., 1-5-5 Tahatsukadai, Nishiku, Kobe 651-2271, Japan