1. Department of Mechanical Engineering, KAIST, 373-1, Guseong-Dong, Yuseong-Gu, Daejeon 305-701, Republic of Korea
2. Department of Environment and Energy Research Center, RIST, 32, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk 790-330, Republic of Korea
3. Corporation R&D Center, SK Corporation, Wonchon-Dong, Yuseong-Gu, Daejeon 305-712, Republic of Korea