1. College of Science, Hunan University of Technology and Business, 410205 Changsha, Hunan, China
2. Key Laboratory of Hunan Province for Statistical Learning and Intelligent Computation, 410205 Changsha, Hunan, China
3. Department of Mathematics, University of Craiova, 200585 Craiova, Romania
4. School of Mathematics and Information, Xiangnan University, Chenzhou, 423000, Hunan, China