supported by National Natural Science Foundation of China(11061032);Scientific Research Project Plan of Gansu Province for Colleges and Universities Postgraduate Tutor(1205-07)
Supported by NSFC(No.11061032);Colleges and Universities Scientific Research Plan of Gansu Province for Postgraduate Tutor(No.1205-07);Colleges and Universities Fundamental Research Funds Project of Gansu Province(2012)
Supported by the National Natural Science Foundation of China ( 11061032,30973586);the Young Fund of Northwest University for Nationalities (X2009-003)