1. Ph.D. Candidate, Dept. of Mechanical Engineering, Graduate School of Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
2. Master Student, Dept. of Mechanical Engineering, Graduate School of Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
3. Professor, School of Mechanical Engineering, Hanyang Univ., 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea (corresponding author).