supported by National Natural Science Foundation of China(10971081,J0630104);Program for New Century Excellent Talents in University(NCET-08-237);Scientific Research Fund of Jilin University (200810024);Natural Science Foundation of Jilin Provincial Science & Technology Department(20101599, 201015100);985 project of Jilin University and the Doctor Foundation at Jilin University of Finace and Economics (10XB20)