1. Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
2. School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
3. Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong,
China
4. Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109-2140, USA