1. Long Li:
Department of Mathematics and Computational Science, Hengyang Normal University, Hengyang, 421008, China
2. Tian Xu:
Department of Mathematics and Computational Science, Hengyang Normal University, Hengyang, 421008, China
3. Yan Liu:
Department of Applied Mathematics, Dalian Polytechnic University, Dalian, 116034, China
4. Jie Yang:
School of Mathematical Sciences, Dalian University of Technology, Dalian, 116024, China