1. School of Mathematical Sciences, Sichuan Normal University, Chengdu 610066, China
2. Department of Mathematics, Chengdu Normal University, Chengdu 611130, China
3. School of Mathematics and Statistics, Hunan Normal University, Changsha 410081, China
4. Department of Mathematics, Sichuan Sanhe College of Professional, Luzhou 646200, China
5. School of Information Science and Engineering, Chengdu University, Chengdu 610106, China