1. Research Center of Intelligent Information Technology, Department of Computer Science and Technology, Faculty of Software, Dongguan University of Science and Technology, Dongguan 523808, P.R. China
2. School of Mathematics and Information Sciences, Guangzhou University, Guangzhou Higher Education Mega Center, Guangzhou 510006, P.R. China
3. Institute of Information Science, Faculty of Mathematics and Information Science, Shanxi University of Science and Technology, Hanzhong 723001, P.R. China