1. School of Mathematics, Shanghai University of Finance and Economics, Shanghai200433, P. R. China
2. Institute of Computational Mathematics and Mathematical Geophysics SB RAS, Novosibirsk, Russia
3. Department of Mathematics, Hokkaido University, Sapporo, Japan
4. Institute of Textiles & Clothing, The Hong Kong Polytechnic University, Hong Kong; and School of Architecture and Art, Central South University, Changsha 410075, P. R. China
5. School of Mathematics, Shanghai University of Finance and Economics, Shanghai200433; and School of Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China