1. Department of Mechanical Engineering, POSTECH, Pohang 790-784, South Korea
2. Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-794, South Korea
3. School of Mechanical and Automotive Engineering, Kunsan National University, Kunsan 573-701, South Korea
4. Division of Mechanical System Engineering, Incheon National University, Incheon 406-772, South Korea