1. Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500, China
2. School of Mathematics and Computer Science, Yunnan Minzu University, Kunming 650500, China
3. School of Media and Information Engineering, Yunnan Open University, Kunming 650504, China
4. College of Computer Science, Sichuan University, Chengdu 610065, China