1. Department of Mathematics and Physics; Fujian University of Technology; Fuzhou Fujian 350108 China
2. Department of Information Engineering and Computer Science; Feng Chia University; 100 Wenhwa Rd., Seatwen Taichung 40724 Taiwan
3. Department of Computer Science and Information Engineering; Asia University; Taichung 41354 Taiwan
4. Department of Computer Science Electrical Engineering; University of Missouri-Kansas City; 5110 Rockhill Road Kansas City MO 64110 U.S.A.