1. School of Mathematics and Physics, Wuhan Institute of Technology, Wuhan 430205, China
2. Department of Public Basic Teaching and Research, Shandong Police College, Jinan 250014, China
3. School of Mathematics and Physics, China University of Geosciences, Wuhan 430074, China
4. Institute for Functional Intelligent Materials, National University of Singapore, Singapore 119077, Singapore
5. Department of Mathematics, National University of Singapore, Singapore 119077, Singapore