高等学校博士学科点专项科研基金20110201130009;陕西省科学技术研究发展计划国际合作项目2012KW-39-01。@@@@Specialized Research Fund for the Doctoral Program of Higher Education, No.20110201130009;International Cooperation Program of Science and Technology Development of Shaanxi Province, No.2012KW-39-01