[1] Guangzhou Univ, Sch Math & Informat Sci, Guangzhou 510006, Guangdong, Peoples R China
[2] Guangzhou Univ, Key Lab Math & Interdisciplinary Sci Guangdong Hi, Guangzhou 510006, Guangdong, Peoples R China
[3] Beijing Univ Posts & Telecommun, Sch Sci, Beijing 100876, Peoples R China
[4] Shanghai Dianji Univ, Dept Math & Phys, Shanghai 201306, Peoples R China