1. University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai, China
2. State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
3. National Institute of Standards and Technology, Gaithersburg, MD, USA
4. Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA