[1] Department of Computer Science, South China University of Technology, Guangzhou, Guangdong Province, China
[2] Dept. of Comp. and Electron. Eng., Guangdong Prov. Inst. Tech. Person, Guangzhou, Guangdong Province, China
[3] Dept. of Mathematical Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku Tokyo 113-8656, Japan
[4] Department of Mathematics, North Dakota State University, Fargo, ND 58105, United States