1. School of Automation, Chongqing University of Posts and Telecommunications 1 , Chongqing 400065, China
2. The MOE-LCSM, School of Mathematics and Statistics, Hunan Normal University 2 , Changsha 410081, China
3. School of Science, Chongqing University of Posts and Telecommunications 3 , Chongqing 400065, China
4. Department of Physics, Lanzhou University of Technology 4 , Lanzhou 730050, China