In this paper,the design and implementation of an access control model for Linux system are discussed in detail. The design is based on the RBAC model and combines with the inherent characteristics of the Linux system...In this paper,the design and implementation of an access control model for Linux system are discussed in detail. The design is based on the RBAC model and combines with the inherent characteristics of the Linux system,and the support for the process and role transition is added.The core idea of the model is that the file is divided into different categories,and access authority of every category is distributed to several roles.Then,roles are assigned to users of the system,and the role of the user can be transited from one to another by running the executable file.展开更多
分别以二正丁胺(DBA)、拟薄水铝石、磷酸和硅溶胶为模板剂、铝源、磷源和硅源,通过水热合成法,制备出纯相的SAPO-41分子筛。采用XRD、氮气物理吸附、29Si MAS NMR、SEM和吡啶红外(Py-IR)等分析表征手段,考察了DBA用量和晶化时间对SAPO-4...分别以二正丁胺(DBA)、拟薄水铝石、磷酸和硅溶胶为模板剂、铝源、磷源和硅源,通过水热合成法,制备出纯相的SAPO-41分子筛。采用XRD、氮气物理吸附、29Si MAS NMR、SEM和吡啶红外(Py-IR)等分析表征手段,考察了DBA用量和晶化时间对SAPO-41分子筛的晶体结构、孔结构、分子筛骨架中Si原子分布、形貌以及B酸中心强度的影响。降低DBA用量会减弱AFO拓扑结构的导向能力,延长晶化时间不仅有利于AFO拓扑结构的生成,而且有利于分子筛结晶度提高。展开更多
文摘In this paper,the design and implementation of an access control model for Linux system are discussed in detail. The design is based on the RBAC model and combines with the inherent characteristics of the Linux system,and the support for the process and role transition is added.The core idea of the model is that the file is divided into different categories,and access authority of every category is distributed to several roles.Then,roles are assigned to users of the system,and the role of the user can be transited from one to another by running the executable file.
文摘分别以二正丁胺(DBA)、拟薄水铝石、磷酸和硅溶胶为模板剂、铝源、磷源和硅源,通过水热合成法,制备出纯相的SAPO-41分子筛。采用XRD、氮气物理吸附、29Si MAS NMR、SEM和吡啶红外(Py-IR)等分析表征手段,考察了DBA用量和晶化时间对SAPO-41分子筛的晶体结构、孔结构、分子筛骨架中Si原子分布、形貌以及B酸中心强度的影响。降低DBA用量会减弱AFO拓扑结构的导向能力,延长晶化时间不仅有利于AFO拓扑结构的生成,而且有利于分子筛结晶度提高。