作者机构:[1]School of Mathematics and Scientific Computer Zhongshan University Guangzhou, 510275 P. R. China, [2]School of Mathematics and Computer Science Gannan Teachers College Ganzhou, 341000 P. R. China
相关基金:Supported in part by the Foundations of the National Natural Science Committee(No.10572154), Jiangxi Province Natural Science Committee(No.0611005) and the Foundation of Education Ministry, Jiangxi Province (No.[2006]239), China.