1. Department of Applied Mathematics, Guangzhou Huashang College, Guangzhou 511300, China
2. College of Mathematics and Statistics, Guangdong University of Finance and Economics, Guangzhou 510320, China
3. School of Computer Science and Information Security, Guilin University of Electronic Technology, Guilin 541004, China
4. School of Mathematics, Guangdong University of Education, Guangzhou 510303, China