1. School of Electrical and Information Engineering, Hunan Institute of Technology, Hengyang 421002, China
2. Department of Mathematics and Physics, Hunan Institute of Technology, Hengyang 421002, China
3. School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
4. School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China