ZHANG Zeng-Dong1, MO Zun-Li1**, BAO Qian-Qian2, MA Jin-Zhong3
1. Northwest Normal University, Lanzhou 730070, China; 2. Lanzhou College of Information Science and Technology,Lanzhou 730300, China; 3. The Ethnic Middle School of Jishishan County,Linxia 731799,China