1. Program of Materials Science and Engineering Department of Applied Physics and Applied Mathematics Columbia University New York NY 10025 USA
2. School of Physics Huazhong University of Science and Technology Wuhan 430074 P. R. China
3. College of Engineering and Applied Science Nanjing University Nanjing 210093 P. R. China
4. Department of Earth and Environmental Engineering Columbia University New York NY 10025 USA
5. Department of Mechanical Engineering Columbia University New York NY 10025 USA
6. Visual Communication Department School of the Art Institute of Chicago Chicago IL 60603 USA