1. School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
2. Nature Inspired Computing and Engineering Research Group, School of Computer Science and Electronic Engineering, University of Surrey, Guildford, Surrey GU2 7XH, UK
3. School of Electrical and Mechanical, Beijing Institute of Technology, 100081 Beijing, P. R. China
4. School of Automation, Chengdu University of Information Technology, Chengdu 610225, P. R. China