1. Tianjin University, School of Science, Mathematics Department, 135 Yaguan Road, Jinnan District, Tianjin 300350, China
2. Tianjin University, School of Science, Mathematics Department, 135 Yaguan Road, Jinnan District, Tianjin 300350, ChinabXinjiang Normal University, School of Mathematics Science, 16 Kashgar East Road, Xinshi District, Urumqi 830013, China