1. College of Information Science and Engineering, Northeastern University, Shenyang 110819, China
2. Faculty of Engineering, University of Sydney, Sydney, 2006 NSW, Australia
3. Faculty of Information and Control Engineering, Shenyang Jianzhu University, Shenyang 110168, China
4. Department of Computer Science and Technology, University of Bedfordshire, Luton LU1 3JU, UK