国家自然科学基金项目31470224,31400430;国家国际科技合作专项项目2014DFA91340;甘肃省国际合作基金项目No.1504WKCA089-2National Natural Science Foundation of China31470224,31400430;National International Scientific and Technological Cooperation Special Projects2014DFA91340;Gansu Province International Cooperation Fund1504WKCA089-2