基金Acknowledgements: This research is supported in part by National Nature Science Foundation of China (No. 70672029 and 70532001), project of key base for studies of social science of Ministry of Education of China (No. 05JJD630023), Social Science Foundation of Tianjin (No. TJ05-GL004), base for innovation of Philosophy and Social Science 985 Project-"Management and institution innovation of Corporate in China" item.