出处
《通讯和计算机(中英文版)》
2008年第11期42-47,共6页
Journal of Communication and Computer
基金
Acknowledgements: This work was supported by the Foundations of Post Doctor of China (No. 20060401001) and by the Science Research Projects of Ministry of Education of China (No. 06JA630056) and by the Natural Science Foundations of Ningxia (No. NZ0848).