Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2010 - 20182

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    RELIABILITY OF CERAMIC ELECTRODES OF SOLID OXIDE FUEL CELLS
    (2018) Patel, Nripendra Kumar; Pecht, Michael G; Das, Diganta; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid oxide fuel cells (SOFCs) are highly efficient chemical to electrical energy conversion devices that have potential in a global energy strategy. The wide adoption of SOFCs is currently limited by cell durability and manufacturing cost. Ceramic anodes show promise for improved durability and are prominent candidate for electrodes of SOFCs. Ishikawa diagram was developed and a comprehensive failure modes, mechanisms, effects, and criticality analysis (FMMECA) methodology is applied to ceramic anodes of SOFCs to understand possible causes of failure. Despite high conductivity and better performance of conventional ceramic electrodes i.e. strontium-based perovskite electrodes, there is a concern that humidity, especially high humidity and high temperature, during storage can affect the properties prior to installation. Degradation mechanisms which can manifest themselves during storage was found and empirical degradation model was developed to determine the storage specification for strontium-based perovskite electrodes of SOFCs.
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    Characterization and Modeling of High Power Microwave Effects in CMOS Microelectronics
    (2010) Holloway, Michael Andrew; O'Shea, Patrick G; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The intentional use of high power microwave (HPM) signals to disrupt microelectronic systems is a substantial threat to vital infrastructure. Conventional methods to assess HPM threats involve empirical testing of electronic equipment, which provides no insight into fundamental mechanisms of HPM induced upset. The work presented in this dissertation is part of a broad effort to develop more effective means for HPM threat assessment. Comprehensive experimental evaluation of CMOS digital electronics was performed to provide critical information of the elementary mechanisms that govern the dynamics of HPM effects. Results show that electrostatic discharge (ESD) protection devices play a significant role in the behavior of circuits irradiated by HPM pulses. The PN junctions of the ESD protection devices distort HPM waveforms producing DC voltages at the input of the core logic elements, which produces output bit errors and abnormal circuit power dissipation. The dynamic capacitance of these devices combines with linear parasitic elements to create resonant structures that produce nonlinear circuit dynamics such as spurious oscillations. The insight into the fundamental mechanisms this research has revealed will contribute substantially to the broader effort aimed at identifying and mitigating susceptibilities in critical systems. Also presented in this work is a modeling technique based on scalable analytical circuit models that accounts for the non-quasi-static behavior of the ESD protection PN junctions. The results of circuit simulations employing these device models are in excellent agreement with experimental measurements, and are capable of predicting the threshold of effect for HPM driven non-linear circuit dynamics. For the first time, a deterministic method of evaluating HPM effects based on physical, scalable device parameters has been demonstrated. The modeling presented in this dissertation can be easily integrated into design cycles and will greatly aid the development of electronic systems with improved HPM immunity.