1. School of Mechanical Engineering, Yonsei University, 134 Sinchon-dong, Seodaemoon-ku, Seoul, 120-749, Republic of Korea
2. School of Mechatronics, Korea University of Technology and Education, Chonan, Chungnam, 350-708, Republic of Korea
3. Mechanical Engineering Department, Korea Power Engineering Co., Inc., 360-9 Mabuk-dong, Yongin, Gyeonggi, 446-713, Republic of Korea