1. School of Aerospace Engineering and Applied Mechanics, Tongji University, No. 1239, Siping Road, Shanghai 200092, P. R. China
2. Department of Mathematics, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, P. R. China
3. School of Aerospace and Applied Mechanics, Tongji University, No. 1239, Siping Road, Shanghai 200092, P. R. China