1. School of Mathematical Sciences and V.C. & V.R. Key Lab, Sichuan Normal University, Chengdu 610066, People’s Republic of China
2. Department of Basic Courses, Sichuan Vocational College of Finance and Economics, Chengdu 610101, People’s Republic of China
3. School of Mathematical Sciences, University of Electronic Science and Technology of China, Chengdu 611731, People’s Republic of China