1. School of Life Science and Technology Xidian University Xi'an 710126 Shaanxi P. R. China
2. Xi'an Doctor Biotechnology Co. Ltd. Xi'an 710126 Shaanxi P. R. China
3. School of Computer Science and Technology Xidian University Xi'an 710071 Shaanxi P. R. China
4. Institute of Automation Chinese Academy of Sciences Beijing 100190 P. R. China