1. Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro,
Yuseong-gu, Daejeon 305-701, South Korea
2. Department of Civil, Structural and Environmental
Engineering, University at Buffalo, Buffalo, New York 14260, United States
3. KAIST Institute (KI) for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro,
Yuseong-gu, Daejeon 305-701, South Korea