1. Dept. of Computer Science and Information Management, Providence Univ., Taichung 43301, TW.
2. Dept. of Applied Mathematics, National Chung-Hsing Univ., Taichung 402, TW.
3. Institute of Information and Decision Sciences, National Taipei College of Business, Taipei 100, TW (Corresponding author), e-mail: yangdy@webmail.ntcb.edu.tw