国家自然科学基金项目31560660;青海省科技项目2016-ZJ-729;青海大学中青年科研基金项目2015-QNY-5资助 This work was supported by the National Natural Science Foundation of China31560660;the Science and Technology Project of Qinghai Province,China2016-ZJ-729;the Scientific Research Foundation for Young and Middle-aged of Qinghai University2015-QNY-5