1. School of Electrical Engineering, Sichuan University, Chengdu, China
2. School of Mathematics, Shandong University, Jinan, China
3. Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian, China
4. School of Mathematics and Physics, Bohai University, Jinzhou, China
5. School of Mathematics Science, Liaocheng University, Liaocheng, China