[1] Southeast Univ, Sch Math, Nanjing 210096, Peoples R China
[2] Yonsei Univ, Yonsei Frontier Lab, Seoul 03722, South Korea
[3] Zhejiang Normal Univ, Coll Math & Comp Sci, Jinhua 321004, Zhejiang, Peoples R China
[4] Yunnan Minzu Univ, Sch Math & Comp Sci, Kunming 650031, Yunnan, Peoples R China