1. Reactor Mechanical Engineering Division; Korea Atomic Energy Research Institute, 999-111 Daedeok-Daero, Yuseong-gu; Daejeon 305-353 Korea
2. Department of Aerospace Engineering Sciences; University of Colorado; Boulder CO 80309-429 USA
3. Division of Ocean Systems Engineering; School of Mechanical Engineering, KAIST; Daejeon 305-701 Korea
4. Division of Mechanical Engineering; School of Mechanical Engineering, KAIST; Daejeon 305-701 Korea