1. College of Physics and Electronics, Central South University, Changsha 410083, China
2. Provincial Key Laboratory of Informational Service, for Rural Area of Southwestern Hunan, Shaoyang University, Shaoyang 422000, China
3. School of Mathematics and Statistics, Hunan University of Technology and Business, Changsha 410205, China
4. School of Computer Science and Engineer, Central South University, Changsha 410083, China