1. Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
2. Mechanical and Aerospace Engineering and Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong, People’s Republic of China
3. Mechanical and Aerospace Engineering, University at Buffalo, State University of New York, Buffalo, New York 14260
4. Mechanical Engineering and Engineering Systems Division, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139