SHU ZHANG School of Aerospace Engineering and Applied Mechanics, Tongji University, No. 1239, Siping Road, Shanghai 200092, P. R. China Department of Mathematics, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, P. R. China zhsh886@yahoo.com.cn KWOK-WAI CHUNG∗ Department of Mathematics, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, P. R. China makchu...