1. School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea
2. School of Electronic and Electrical Engineering, Hongik University, 94 Wausan-Ro, Mapo-Gu, Seoul 121-791, South Korea
3. Agency for Defense Development, 4-4 Yuseong, P.O. Box 35, Daejeon 305-600, South Korea