1. Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208
2. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, P. R. C.; Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208
3. Department of Engineering Mechanics, Tsinghua University, Beijing 100084, P. R. C.
4. School of Chemical and Biological Engineering, Seoul National University, Seoul, 151-744, Korea
5. Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, TX 78705
6. Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208
7. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, P. R. C.
8. Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208;Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208
9. Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801