1. Department of Computer Science and Engineering, National Chung Hsing University Taichung 402, Taiwan, ROC. phd9308@cs.nchu.edu.tw
2. Department of Information Management, Hsiuping Institute of Technology Taichung 412, Taiwan, ROC. dstsai@mail.hit.edu.tw
3. Department of Computer Science and Engineering, National Chung Hsing University Taichung 402, Taiwan, ROC. gbhorng@cs.nchu.edu.tw