We introduce the general AC( atlribure certificate), the role specificationAC and the rolt assignment AC We discuss the rolt-based PMI(Privilege Management Infrastructure)architecture. The role-based PMT(Public-Kty In...We introduce the general AC( atlribure certificate), the role specificationAC and the rolt assignment AC We discuss the rolt-based PMI(Privilege Management Infrastructure)architecture. The role-based PMT(Public-Kty In-frastructure) secure model forE-govcrnment isresearehed by combining the role-bastd PMI with PKI architeclure (Public Key Infrastructure). Themodel has advantages of flexibility, convenience, less storage space and less network consumptionetc. We are going to ust iht secure modelin the E-govern-ment system.展开更多
Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the...Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mis- sion. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang＇E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.展开更多
根据现有复制策略在局部节点故障时数据查找失败率高的缺点,提出一种针对Chord网络的数据复制方法——Rd-Chord(rearranged replication method based on Chord)。利用离散存储的方法,将数据复制到Chord覆盖网根节点前继相对分散的节点...根据现有复制策略在局部节点故障时数据查找失败率高的缺点,提出一种针对Chord网络的数据复制方法——Rd-Chord(rearranged replication method based on Chord)。利用离散存储的方法,将数据复制到Chord覆盖网根节点前继相对分散的节点中,即使某个甚至几个区域节点全部故障,其他区域依然有数据副本可供使用。同时,为了维护网络结构和key迁移,针对Rd-Chord提出基础更新和定期更新2种更新策略。为了验证该方法的优越性,通过计算机仿真对前继复制、后继复制和Rd-Chord方法进行了大量的比较实验。实验结果表明,Rd-Chord方法能够解决节点区域性故障问题,在保证平均查找效率的前提下,查找失败率降低了近10%,明显优于其他方法。展开更多
文摘We introduce the general AC( atlribure certificate), the role specificationAC and the rolt assignment AC We discuss the rolt-based PMI(Privilege Management Infrastructure)architecture. The role-based PMT(Public-Kty In-frastructure) secure model forE-govcrnment isresearehed by combining the role-bastd PMI with PKI architeclure (Public Key Infrastructure). Themodel has advantages of flexibility, convenience, less storage space and less network consumptionetc. We are going to ust iht secure modelin the E-govern-ment system.
基金supported by the National Basic Research Program of China("973" Program)(2012CB720000)the National Natural Science Foundation of China(11102020)the Program for New Century Excellent Talents in University and Beijing Higher Education Young Elite Teacher Project
文摘Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mis- sion. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang＇E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.
文摘根据现有复制策略在局部节点故障时数据查找失败率高的缺点,提出一种针对Chord网络的数据复制方法——Rd-Chord(rearranged replication method based on Chord)。利用离散存储的方法,将数据复制到Chord覆盖网根节点前继相对分散的节点中,即使某个甚至几个区域节点全部故障,其他区域依然有数据副本可供使用。同时,为了维护网络结构和key迁移,针对Rd-Chord提出基础更新和定期更新2种更新策略。为了验证该方法的优越性,通过计算机仿真对前继复制、后继复制和Rd-Chord方法进行了大量的比较实验。实验结果表明,Rd-Chord方法能够解决节点区域性故障问题,在保证平均查找效率的前提下,查找失败率降低了近10%,明显优于其他方法。
