1. School of Mathematics and Statistics Changshu Institute of Technology Changshu Jiangsu China
2. School of Mathematics China University of Mining and Technology Xuzhou Jiangsu China
3. State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology Xuzhou Jiangsu China
4. Faculty of Science Department of Mathematics King Abdulaziz University P.O. Box 80257 Jeddah Saudi Arabia
5. School of Mechanics and Civil Engineering China University of Mining and Technology Xuzhou Jiangsu China
6. School of Mathematics and Statistics Qujing Normal University Qujing Yunnan China