1. Science and Technology on Electromechanical Dynamic Control Laboratory, Xi’an Institute of Electromechanical Information Technology, Xi’an, China
2. Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China
3. School of Physics, Northwest University, Xi’an, China
4. Department of Electrical and Electronic Engineering and the School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China