1. Department of Mathematics, Faculty of Science, Shanghai University, Shanghai 200444, P. R. China
2. Institute for Information and System Science, Faculty of Science, Xi'an Jiaotong University, Xi'an 710049, P. R. China
3. Institute for Artificial Intelligence and Robotics, Xi'an Jiaotong University, Xi'an 710049, P. R. China
4. Key Lab of Complex Systems and Intelligent Science, Institute of Automation, Chinese Academy of Sciences, Beijing 100080, P. R. China