作者机构:[1]College of Computer Science and Technology, Jilin University, Changchun 130012, P. R. China, [2]Key Laboratory of S.vmbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012, P. R. China
相关基金:Acknowledgments This work was supported by National Natural Science Foundation of China (Grant no. 60971089), National Electronic Development Foundation of China (Grant no. 2009537), Jilin Province Science and Tech- nology Department Project of China (Grant no. 20090502).