We are grateful to Zhang Weiting and Li Shu for delivering important documents for me. So many grants for this paper: National Basic Research Program of China (973 Program) (No. 2012CB821900); Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China (No. 131021); The National Natural Science Foundation of China (No. 31372242, 41272006, 31230065); The General Program of Science and Technology Development Project of Beijing Municipal Education Commission of China (No. KM201210028016); Project of Outstanding Young-aged Talents of Beijing Municipal Commission of Education (No.CIT&TCD201304163); Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13081) and Project of Great Wall Scholar and KEY project of Beijing Municipal Commission of Education Project (grant KZ201310028033).