1. School of Mathematics, Dongguan Polytechnic , Dongguan , Guangdong 523808 , P. R. China
2. School of Mathematics and Computational Science, Huaihua University , Huaihua , Hunan 418008 , P. R. China
3. School of Mathematics and Big Data, Anhui University of Science and Technology , Huainan , Anhui 232001 , P. R. China