国家自然科学基金项目81271090/H1304;北京市自然科学基金项目7162066、7162072;北京市教委科技计划重点项目 KZ201410025027Fund programsNational Natural Science Foundation of China 81271090/H1304;Beijing Natural Science Foundation 7162066、7162072; Major Projects of Science and Technology Plan from Beijing Municipal Education Commission KZ201410025027