[1] St Marys Univ, Dept Math & Comp Sci, Halifax, NS B3H 3C3, Canada
[2] Beijing Jiaotong Univ, Weihai Inst, Weihai 264401, Shandong, Peoples R China
[3] Hunan Inst Sci & Technol, Dept Math, Yueyang 414015, Hunan, Peoples R China
[4] Northwest Univ, Inst Concepts Cognit & Intelligence, Xian 710127, Shaanxi, Peoples R China