F. R. Hsu, M. K. Shan**, H. S. Chao+ and R. C. T. Lee++
Department of Information Engineering and Computer Science
Feng Chia University
Taichung, 407 Taiwan
E-mail: frhsu@fcu.edu.tw
**Department of Computer Science
National Chengchi Unviersity
Taipei, 116 Taiwan
+Synopsys Taiwan Limited
++Department of Computer Science and Information Engineering
National Chi Nan University
Nantou, 545 Taiwan