1. Mechanical, Aerospace, and Materials Engineering, Southern Illinois University, Carbondale, Illinois 62901, United States
2. Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
3. Mechanical Engineering, Tsinghua University, Beijing 100084, China
4. Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
5. Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States