1. School of Mathematical Sciences, Inner Mongolia Normal University, Huhhot 010028, China
2. School of Mathematical Sciences, Inner Mongolia University, Huhhot 010021, China
3. School of Oceanography and Atmosphere, Ocean University of China, Qingdao 266100, China
4. School of Electronic Engineering, Xidian University, Xi’an 710071, China
5. Department of Mathematics, The Chinese University of Hong Kong, Satin, Hong Kong 999077, China