1. School of Electronics and Information Science, Jiangsu University of Science and Technology, Mengxi Road 2, Zhenjiang, Jiangsu 212003, China. syinglei2013@163.com
2. Department of Information Technology and Computer Science, Clayton State University, Morrow, GA 30260, USA. jqu@clayton.edu
3. Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA. xyn@bmb.uga.edu, cai@cs.uga.edu