1. Department of Computer Science, University of Salerno, Fisciano, Italy
2. Department of Computer Science and Information Engineering, Chaoyang University of Technology, Taichung, Taiwan, R.O.C. & College of Information, Changchun University of Technology, Changchun, China
3. Department of Computer Science and Information Engineering, Chaoyang University of Technology, Taichung, Taiwan, R.O.C.