1. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, P. R. China
2. College of Computer Science, Chongqing University, Chongqing 400044, P. R. China
3. Department of Computer and Information Science, Faculty of Science and Technology, University of Macau, Macau, P. R. China
4. School of Information Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
5. School of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454003, P. R. China