国家自然科学基金资助项目30871041;陕西省科学技术研究发展计划项目2012KW-40-01;陕西省自然科学基础研究计划Supported by the National Natural Science Foundation of China30871041;Science and Technology Research and Development Program of Shaanxi Province2012KW-40-01;the Natural Science Basic Research Project of Shaanxi Province2014JM-8145