国家自然科学基金项目31272257、山西省自然科学基金2014011001-4和山西省青年科技基金项目2013021032-2资助 Supported by the National Natural Science Foundation of China 31272257,the Natural Science Foundation of Shanxi Province 2014011001-4 and the Youth Science and Technology Foundation of Shanxi Province 2013021032-2