1. System Solution Group, Cadence Design Systems Japan, 2‐100‐45 Shin‐Yokohama Kohoku‐ku Yokohama 222‐0033 Japan
2. Graduate School of EngineeringUniversity of Hyogo, 2167 Shosha Himeji Hyogo 671‐2280 Japan
3. Mathematical Science Center, University of Yamanashi Takeda 4‐3‐11 Kofu Yamanashi 400‐8511 Japan