[Deng, Siqing;Chen, Fulai] Xiangnan Univ, Dept Math, Chenzhou 423000, Hunan, Peoples R China.^[Fang, Kui] Hunan Agr Univ, Sch Informat Sci & Technol, Changsha 410128, Hunan, Peoples R China.^[Fang, Kui] Hunan Norma Univ, Sch Math & Comp, Changsha 410081, Hunan, Peoples R China.^[Xie, Jin] Hefei Univ, Dept Math & Phys, Hefei 230601, Hunan, Peoples R China.