1. Columbia Nanomechanics Research Center, Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027, United States
2. Department of Structural Engineering, University of California—San Diego, La Jolla, California 92093-0085, United States
3. State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
4. School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
5. Department of Civil & Environmental Engineering, Hanyang University, Seoul, 133-791, Korea