Doctoral Scientific Research Foundation of Shanxi Datong University(2014-B-11);National Natural Science Foundation of China(21174114);National Natural Science Foundation of China(21363021);Program for Changjiang Scholars and Innovative Research Team in University of M inistry of Education of China(IRT1177);Scientific and Technical plan project of Gansu province(1204GKCA006);Scientific and Technical Innovation Project of Northw est Normal University(nw nu-kjcxgc-03-63)~~