1. School of Computer and Communication Engineering, Changsha University of Science and Technology, Changsha, China
2. Computer Science and Engineering Department, The Hong Kong University of Science and Technology, Hong Kong, China
3. Computer Science and Technology and Management Department, Fuzhou University, Fuzhou, China
4. Department of Computer Science and Engineering, The Chinese University of Hong Kong, Hong Kong, China
5. Computer Science and Engineering, Central South University, Changsha, China