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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2013 - 20192

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Author: search.filters.author.Bakhshi, RoozbehSubject: search.filters.subject.Mechanical engineering

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    MAXIMIZING THE FINANCIAL RETURNS OF USING LIDAR SYSTEMS IN WIND FARMS FOR YAW ERROR CORRECTION APPLICATIONS
    (2019) Bakhshi, Roozbeh; Sandborn, Peter A; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wind energy is an important source of renewable energy with significant untapped potential around the world. However, the cost of wind energy production is high and efforts to lower the cost of energy generation will help enable more widespread use of wind energy. Ideally, wind turbines have to be aligned with wind flow at all times. However, this is not the case and there exists and angle between a wind turbine nacelle’s central axis and the wind flow. This angle is called yaw error. Yaw error lowers the efficiency of turbines as well as lowers the reliability of key components in turbines. LIDAR devices can correct the yaw error; however, they are expensive and there is a trade-off between their costs and benefits. In this dissertation, a stochastic discrete-event simulation is developed that models the operation of a wind farm. By maximizing the Net Present Value (NPV) changes associated with using LIDAR devices in a wind farm, the optimum number of LIDAR devices and their associated turbine stay time will be determined. These optimum values are a function of number of turbines in the wind farm for specific turbine sizes. The outcome of this dissertation will help wind farm owners and operators to make informed decisions about purchasing LIDAR devices for their wind farms.
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    Reliability Assessment of Voided Microvias in High Density Interconnect Printed Circuit Boards under Thermo-Mechanical Stresses
    (2013) Bakhshi, Roozbeh; Pecht, Michael G; Azarian, Michael H; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Microvias allow signal and power transmission between layers in high density interconnection printed circuit boards. Presence of voiding in filled microvias due to defective manufacturing process has raised concerns in industry. Voids can vary widely in shape and size and have been observed in both stacked and single-level microvias. IPC standards have addressed the presence of voids in microvias using void size as the acceptance criterion. The purpose of this study is to determine how voiding affects the degradation of microvias; if void size is the only parameter that needs to be taken into consideration or void shape is important as well. Voided as well as non-voided microvias were tested using liquid-to-liquid thermal shock to understand the difference between behavior of voided and non-voided microvias under thermo-mechanical stresses.