1. School of Mathematics and Statistics, Changsha University of Science and Technology, Changsha, Hunan, People's Republic of China
2. Hubei Key Laboratory of Power System Design and Test for Electrical Vehicle, Hubei University of Arts and Science, Xiangyang, Hubei, People's Republic of China
3. School of Mathematics and Statistics, Hubei University of Arts and Science, Xiangyang, Hubei, People's Republic of China
4. School of Mathematics and Computational Science, Xiangtan University, Xiangtan, Hunan, People's Republic of China
5. School of Mathematics and Statistics, Hunan Normal University, Changsha, Hunan, People's Republic of China