Institution: | 1.School of Science, Dalian Jiaotong University, Dalian, 116028, People’s Republic of China ;2.Department of Mathematics and Statistics, Zhoukou Normal University, Zhoukou, 466001, People’s Republic of China ;3.Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, P. O. Box 193, Arnesano, 73100, Lecce, Italy ; |