国家自然科学基金No.31272319;高等学校博士学科点专项科研基金No.20111401110010;山西省普通高校特色重点学科建设项目No.2011-SXDX-SWX-003;Supported by the National Natural Science Foundation of China No.31272319,the Specialized Fund for the Doctoral Program of Higher Education No.20111401110010 and the Special Subject and Key Project of Shanxi ProvinceNo.2011-SXDX-SWX-003