基金Supported by the National Natural Science Foundation of China under Grant Nos.90412010 60573166 (国家自然科学基金)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.2007108 (高等学校博士学科点专项科研基金)the HP University Collaborative Foundation of China under Grant No.HLCFY08-001 (惠普大学合作基金)