[1] China Univ Min & Technol, Sch Math, Xuzhou 221008, Jiangsu, Peoples R China
[2] Dalian Univ Technol, Sch Energy & Power, Dalian 116024, Peoples R China
[3] Lanzhou Univ, Sch Math & Stat, Gansu Key Lab Appl Math & Complex Syst, Lanzhou 730000, Gansu, Peoples R China