1. Principal Researcher, 8th R&D Institute, Agency for Defense Development, Taean P.O. Box 1, Taean-eup, Taean-gun, Chungnam 357-900, Republic of Korea (corresponding author).
2. Professor, Dept. of Mechanical Design Engineering, Chungnam National Univ., 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea.