1. School of Computer and Information, Hefei University of Technology, Hefei, Anhui, China
2. I+ Lab, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
3. Department of Sciences and Informatics, Muroran Institute of Technology, Muroran, Hokkaido, Japan
4. National Institute of Informatics, Chiyoda City, Tokyo, Japan