1. School of Mathematics and Computer Engineering, Xihua University, Chengdu, Sichuan 610039, China
2. School of Computer and Information Technology, Liaoning Normal University, Dalian 116029, China
3. Department of Engineering, Faculty of Engineering and Science, University of Agder, 4898 Grimstad, Norway
4. Department of Computing and Mathematical Sciences, University of Glamorgan, Pontypridd CF37 1DL, UK
5. School of Engineering and Science, Victoria University, Melbourne, VIC 8001, Australia