1. School of Mathematics Sciences, University of Electronic Science and Technology of China, Chengdu Sichuan 611731, China
2. Visual Computing and Virtual Reality Key Laboratory of Sichuan Province, Sichuan Normal University, Chengdu, Sichuan 610068, China
3. School of Mathematics Education, China West Normal University, Nanchong Sichuan 637002, China
4. School of Electronic Information and Electrical Engineering, Chengdu University, Chengdu, Sichuan 610106, China