Institution: | 1. School of Mathematical Sciences , South China Normal University , Guangzhou, P.R. China yanpingchen@scnu.edu.cn;3. Department of Mathematics, Hunan Key Laboratory for Computation and Simulation in Science and Engineering , Xiangtan University , Xiangtan, P.R. China;4. College of Mathematics and Computer Sciences , Chongqing Three Gorges University , Chongqing, P.R. China |