基金项目: | supported in part by the National Natural Science Foundation of China(61172051,61302070,61202071, 61302072);the Fundamental Research Funds for the Central Universities (N110804003,N120804002,N120404001, N120604001);the Program for New Century Excellent Talents in University(NCET-120102);the Specialized Research Fund for the Doctoral Program of Higher Education (20120042120049) |