[Yang, Zhifeng] Hunan Normal Univ, Coll Math & Comp Sci, Changsha, Hunan, Peoples R China.^[Yang, Zhifeng] Hengyang Normal Univ, Dept Math & Computat Sci, Hengyang, Peoples R China.^[Zhao, Yang] Jiangmen Polytech, Dept Elect & Informat Technol, Jiangmen, Peoples R China.^[Fan, Guobing] Hunan Univ Finance & Econ, Dept Basic Subjects, Changsha, Hunan, Peoples R China.