1. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, P. R. China
2. School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
3. Department of Computer and Information Science, Faculty of Science and Technology, University of Macau, Macau
4. Department of Basic Courses, Beijing Union University, Beijing 100101, P. R. China