1. Faculty of Information Technology, the Beijing Key Laboratory of Computational Intelligence and Intelligent System, and the Engineering Research Center of Digital Community, Ministry of Education, Beijing University of Technology, Beijing 100124, China (e-mail: rechardhan@sina.com)
2. Faculty of Information Technology and the Beijing Key Laboratory of Computational Intelligence and Intelligent System, Beijing University of Technology, Beijing 100124, China.
3. Faculty of Information Technology and the Engineering Research Center of Digital Community, Beijing University of Technology, Beijing 100124, China.