1. Automotive Engineering Department, Chengde Petroleum College, Chengde University Park, Chengde, Hebei 067000, China;
2. School of Mechanical and Electrical Engineering, China University of Mining and Technology, No. 1, University Road, Xuzhou, Jiangsu 221116, China e-mail:
3. National Astronomical Observatories/Nanjing Institute of Astronomical Optics and Technology, Chinese Academy of Sciences, No. 188, Bancang Street, Nanjing, Jiangsu 210042, China e-mail: