1. Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China e-mail:
2. Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China;
3. Department of Aeronautics and Astronautics, College of Engineering, Peking University, Beijing 100871, China e-mails: ;