This thesis explores possibilities of using recently introduced ensemble-based component models (represented by the DEECo model) as a management layer in a cloudlet-like environment for mobile computation offloading, which can lead to savings of limited mobile-specific resources such as battery life. As a part of the solution, the goal is analyzed, possible issues and problems are identified and then addressed by designing and implementing a reference architecture for computation offloading of parts of mobile applications managed by a DEECo-based control layer. The implementation is presented in the form of an offloading framework, whose use is demonstrated on two applications for the Android platform. Finally, the framework's performance and utility is evaluated by comparing offloaded and local executions of the same application. Powered by TCPDF (www.tcpdf.org)

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<p> Environmental Barrier Coatings (EBCs) protect ceramic gas turbine engine components from corrosion by high temperature water vapor, but the coatings often form complex metastable microstructures upon plasma spray deposition. In ytterbium disilicate (YbDS) and its yttrium-doped counterpart (Y/YbDS), two coatings compatible with SiC/SiC parts, plasma spray forms a largely cracked, mechanically weak amorphous phase comprising up to ~80% of the coating’s volume. Therefore, the coatings must undergo a pre-service heat treatment to crystallize into stable phases and heal cracks. During the treatment, however, interplay between thermal expansion and crystallization contraction can cause vertical cracks which expose the component to the corrosive atmosphere. Remedial treatments with long, high temperature holds (~1300 ºC) can both crystallize the coating and heal existing cracks. However, these temperatures cause unnecessary grain growth that reduces the structural integrity of the coating over its lifetime.</p> <p>Here we propose an alternate heat treatment informed by experiments and modelling that removes metastable phases, heals cracks, and reduces time at temperature to prevent significant grain growth. First, we determine crystallization and phase change kinetics by applying the Ozawa-Flynn-Wall and Vyazovkin kinetic methods to differential scanning calorimetry (DSC) data. Next, we track locations and microstructural effects of phase evolution using correlative Raman spectroscopic mapping, scanning electron microscopy (SEM), and X-Ray diffraction (XRD). We interpret the formation of three distinct phases – a major phase of stable β-YbDS, and minor phases of stable Χ2-YbMS and metastable α-YbDS – within the existing framework of kinetic theory and quantify differences in their transformations between YbDS and Y/YbDS. We find that cracks in the coating heal through the crystallization of the amorphous phase and the transformation of the metastable phase although the mechanisms remain unclear. Each phase transformation causes a bulk volumetric change which we measure using dilatometry and use to calculate delamination stresses during a simulated heat treatment. Lastly, we determine the viability of our heat treatment compared to the industry standard.</p>

Designing Resilient Distributed embedded Systems is a challenging task. One of the design issues is to guarantee correct behavior of the system during the runtime. It demands verification that information propagated through the system is reliable. The goal of this thesis is a research and implementation of an analysis that should identify obsolescence of variables due to delays caused by scheduling and communication in real-time systems. Analysis will be designed for Ensemble-Based Component System (EBCS) semantics because it enables precise specification and analysis of important properties. The main problem is to find a suitable input model of the analysis and find its possible limits. Effort should be put in balancing between the level of abstraction given to a RDS developer and power of the analysis itself. The main benefit of the analysis will be detection of situations in which data processed in RDS are outdated and can cause incorrect behavior of particular components.

<p dir="ltr">A current engineering challenge is to understand and validate material systems capable of maintaining structural viability under the elevated temperature and environmental conditions of hypersonic flight. One aspect of this challenge is the joining of multiple materials with thermal expansion mismatch, which can lead to residual stress, resulting in debits in component lifetime under in-service loading. The focus of this work is a series of studies focused on a ceramic-metal composite (WC/Cu), a zirconia coating applied to a carboncarbon (C/C) composite, and a silicide (R512E) coating applied to a Nb-based alloy (C103). Each of these material systems are candidates for elevated temperature applications in which dissimilar constituents result in residual stress in the material. Each study leveraged experimental residual strain measurements, with the primary focus on the use of synchrotron X-ray diffraction, in conjunction with representative models, and microscopy to illuminate the active mechanisms in the development and evolution of residual stress in the bulk material. The combination of experimental and modeling predictions provides a framework to inform the viability and lifing of material systems exhibiting dissimilar expansion properties.</p>