1. School of Mathematical Sciences and Fujian Provincial Key Laboratory on Mathematical Modeling and Scientific Computing, Xiamen University, Xiamen, Fujian, China; and School of Mathematical Sciences, Guizhou Normal University, Guiyang, Guizhou, China
2. School of Mathematical Sciences and Fujian Provincial Key Laboratory on Mathematical Modeling and Scientific Computing, Xiamen University, Xiamen, Fujian, China
3. Department of Mathematics, Southern University of Science and Technology, Shenzhen, Guangdong, China