1. Kewen Institute, Jiangsu Normal University, Xuzhou, Jiangsu, People's Republic of China
2. School of Mathematics and Statistics, Jiangsu Normal University, Xuzhou, Jiangsu, People's Republic of China
3. School of Mathematics, China University of Mining and Technology, Xuzhou, Jiangsu, People's Republic of China
4. School of Big Data, Fuzhou University of International Studies and Trade, Fuzhou, Fujian, People's Republic of China