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A Trust-Based Access Control Management Framework for a Secure Grid Environment
Published in Yang Xiao, Security in Distributed, Grid, Mobile, and Pervasive Computing, 2007
James B. D. Joshi, Du Siqing, Saubhagya R. Joshi
X-RBAC, an XML-based specification language for RBAC model, provides a framework for expressing GTRBAC policies as well as interdomain role mappings in both loosely coupled and the federated multidomain environments [21]. In addition, it also allows specification of context-based constraints to capture context-based access requirements. Figure 13.2 shows the XML syntax for general policy specification. The key policy component definitions include XML Role Sheet (XRS), XML User Sheet (XUS), XML Permissions Sheet, (XPS), XML User-Role Assignment Sheet (XURAS), and XML Permission-Role Assignment Sheet (XPRAS), which are briefly described below. Each policy can include multiple constituent policies, thus facilitating specification of policies for multidomain environments. The relationship definition includes mapping specification between the global entities and the entities of the other domains.
Study of non-centrosymmetric to centrosymmetric structural transformation in Zr-doped Barium Titanate
Published in Phase Transitions, 2020
Md Sahanoor Islam, Jiten Ghosh
In this work, phase transformation, dielectric behavior and local atomic arrangement of BZT were analyzed using XRD, PDF, Raman, XPS and FESEM. BaZrxTi1−xO3 (x = 0.0, 0.05, 0.1, 0.3) were prepared by the solid-state reaction method. Here, we observed non-centrosymmetric to centrosymmetric structural transformation of BZT ceramics at room temperature with increasing Zr doping. Non-centrosymmetric phase was found for mole fraction x = 0.0–0.1 and for mole fraction x = 0.3 the phase was centrosymmetric. With the increase in the Zr mole fraction BZT phase changed from the orthorhombic to tetragonal phase for x = 0.05 and 0.1, respectively. The BZT transformed into centrosymmetric cubic phase for x = 0.3. FESEM revealed that with increasing Zr content crystallite size of BZT increased. Phase purity was confirmed from the XPS study. Raman study confirmed the tetragonal to cubic phase transformation for mole fraction x = 0.3. Change in the intensity for the first Ti–O pair in the PDF pattern due to the incorporation Zr in the barium titanate lattice was observed. Two extra shoulders due to the addition of Zr for the cubic phase of BZT appeared in the PDF pattern. Structural and electrical properties of BZT ceramics were influenced significantly by the addition of Zr. The value of dielectric constant significantly changed with the addition of the Zr due to the change in local atomic arrangement. It achieved highest value 1444 for mole fraction x = 0.1 due to more lattice distortion at this mole fraction.