1. a Department of Elect. Eng. and Comp. Sci., Graduate School of Engineering, University of Hyogo , 2167 Shosha, Himeji, Hyogo, Japan , 671-2201
2. b Department of Elect. Eng. and Comp. Sci., Graduate School of Engineering, Himeji Institute of Technology , 2167 Shosha, Himeji, Hyogo, Japan , 671-2201
3. c Tokyo Research Center, TOSOH Corporation , 2743-1, Hyakawa, Ayase, Kanagawa, Japan , 252-1123