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Studies of High-Temperature Deformation Processes in Earth Materials: Experimental Investigations and Theoretical Modeling
No full textExperimental and theoretical investigations play a crucial role in advancing our understanding of high-temperature deformation processes, responsible for the plasticity and strength of the middle to lower crustal layers of continental lithospheres, plate boundaries, and subducting oceanic plates of subduction zones. I have conducted triaxial deformation experiments on naturally occurring perthitic single crystal feldspars to determine their plastic anisotropy, effects of solid solution, and exsolution and water on their mechanical properties. Deformation experiments were performed using a Griggs solid-medium apparatus, maintaining temperatures in the range of 800-900 degrees Celsius, strain rates (Epsilon) at 1.6x10^-6 s^-1 , and confining pressures ranging from 0.5 to 1.5 GPa. My findings revealed that feldspar samples compressed in [012] direction show the lowest flow strengths, while those deformed along the [001] direction displayed the highest flow strength. Deformation and strength measured in the [012] direction at different pressures (0.75-1.5 GPa) and temperatures (900 degrees Celsius) demonstrate that water weakening in feldspars due to intracrystalline defect interactions with hydrous defects depends on the water fugacity. Earthquakes occurring at depths beyond 15 km are often attributed to low effective pressures, owing to elevated pore pressures, as hydrous silicates such as serpentine dehydrate. However, recent assessments of intermediate-depth earthquakes have revealed that temperatures and pressures of seismogenic subducting slabs do not always correspond to antigorite serpentine, amphiboles, or talc dehydration. Altered mantle rocks of the upper lithosphere and mantle wedges also contain magnesian carbonates, which are stable to great depths. Carbonates of downgoing slabs are weaker than anhydrous mantle silicates. My theoretical modeling study of magnesian carbonate horizons within altered peridotite demonstrates that intermediate-depth earthquakes can result from strain localization within carbonates and thermal shear instabilities that lead to seismic rupture. Models of shear instabilities in ultramafic mantle rocks, are based on grain size-sensitive creep and changes in rheology with changes in grain size. Such analyses cannot be implemented for magnesian carbonates without a better understanding of the kinetics governing grain growth and refinement. The grain growth kinetics study of pure magnesite and Ca-rich magnesite show nearly parabolic grain growth for short annealing times in pure magnesite, when curved grain boundaries are dominant
Understanding Security Inconsistencies of Mobile and Web Integration
No full textMobile and web are two core technologies that drive an individual���s everyday life. Over the years, these technologies have evolved mostly independently while at the same time facing similar security challenges and converging to provide services that play crucial roles in various aspect of society. As these technologies have merged, the interplay between mobile and web has resulted in a unique ecosystem where both platforms are tightly integrated.
The dissertation outlines three primary research goals: systematically analyzing mobile-web integration inconsistencies, establishing a unified model for the mobile-web integration ecosystem, and proposing solutions inspired by mutual learning opportunities. We explore the security challenges that emerge when two distinct systems, mobile and web, converge to power modern applications. We show that the integration of these platforms can lead to inconsistencies in security practices across various contexts. The research contributions encompass the identification of Selective Serving inconsistencies, a large-scale measurement study of HTTP Security Header inconsistencies, the development of a client-side mobile application static analysis approach, and the proposal of a web-inspired solution for content-level security in mobile applications.
We specifically explore security challenges from three distinct perspectives, namely the remote server perspective, network data transport perspective, and the local client perspective. It is revealed that clients accessing the same application from different contexts may not receive the same security policies, and even if they do, consistent enforcement cannot be guaranteed. Our analysis of real world applications show that the identified inconsistencies have significant real-world implications for both applications and users.
This dissertation sheds light on the security challenges in the convergence of mobile and web technologies and provides insights into improving the consistency and effectiveness of security practices in this integrated ecosystem to motivate future research