[Liu, Gang] Hengyang Normal Univ, Coll Math & Stat, Hunan Prov Key Lab Intelligent Informat Proc & Ap, Hengyang 421008, Hunan, Peoples R China.^[Ponnusamy, Saminathan] Indian Inst Technol Madras, Dept Math, Madras 600036, Tamil Nadu, India.^[Ponnusamy, Saminathan] IST, Chennai Ctr, 110 Nelson Manickam Rd, Madras 600029, Tamil Nadu, India.