1. School of Control Engineering, Chengdu University of Information Technology, Chengdu 610225, P. R. China
2. School of Electrical and Information Engineering, Tianjin University, Tianjin, 300072, P. R. China
3. School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
4. NICE Group, Department of Computer Science, University of Surrey, UK
5. School of Computer Science and Engineering, Nanyang Technological University, Singapore