[1] South China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China
[2] Huazhong Univ Sci & Technol, Sch Elect & Elect Engn, State Key Lab Adv Electromagnet Engn & Technol, Wuhan 430074, Hubei, Peoples R China
[3] Potsdam Inst Climate Impact Res, D-14415 Potsdam, Germany
[4] Humboldt Univ, Inst Phys, D-12489 Berlin, Germany
[5] Saratov NG Chernyshevskii State Univ, Saratov 4410012, Russia