Fund Project:Supported by the National Natural Science Foundation of China (Grant No.10961014), the Natural Science Foundation of Jiangxi Province (Grant No.2008GZ048), the Science Foundation of the Education Department of Jiangxi Province and the Foundation of Jiangxi Normal University (Grant No.[2007]134) and the Graduate Innovation Special Foundation of the Education Department of Jiangxi Province (Grant No.YC08A044).