基金Supported by the National Natural Science Foundation of China(Grant No.20773103)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(2008101)+2 种基金the selected programs for scholars back fromoverseas,Ministry of Personnel(2006164)Science & Technology Program of Education Depart ment of Henan(2008A150022)the Youth Foundation of Xinyang Normal University(200932)