1. Department of Computer Science and Information Management, Providence Univ., 200 Chung Chi Road, Taichung 43301, TW (Corresponding author), e-mail: wlchen@pu.edu.tw
2. Department of Computer Science and Information Management, Providence Univ., 200 Chung Chi Road, Taichung 43301, TW, e-mail: chwen@pu.edu.tw
3. Department of Computer Science and Information Management, Providence Univ., 200 Chung Chi Road, Taichung 43301, TW, e-mail: czh.bruce@gmail.com