国家自然科学基金61273273,61175096,61271374;高等学校博士学科点专项科研基金2012110110034;北京市教委共建项目资助Supported by National Natural Science Foundation of China61273273,61175096,61271374;Research Fund for the Doctoral Program of Higher Education of China2012110110034;Specialized Fund for Joint Building Project of Beijing Municipal Education Commission