1. College of Computer Science and Technology, China University of Petroleum (East China), Qingdao, China
2. Department of Computing and Mathematics, Manchester Metropolitan University, 6H Manchester, U.K.
3. Department of Computer Science, College of Computers and Information Technology, Taif University, Taif, Saudi Arabia
4. State Key Laboratory of Integrated Service Networks, Xidian University, Xi’an, China
5. Graduate School of Science and Engineering, Hosei University, Tokyo, Japan