UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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 given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Solving, Generating, and Modeling Arc Routing Problems(2017) Lum, Oliver; Golden, Bruce; Wasil, Edward; Applied Mathematics and Scientific Computation; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Arc routing problems are an important class of network optimization problems. In this dissertation, we develop an open source library with solvers that can be applied to several uncapacitated arc routing problems. The library has a flexible architecture and the ability to visualize real-world street networks. We also develop a software tool that allows users to generate arc routing instances directly from an open source map database. Our tool has a visualization capability that can produce images of routes overlaid on a specific instance. We model and solve two variants of the standard arc routing problem: (1) the windy rural postman problem with zigzag time windows and (2) the min-max K windy rural postman problem. In the first variant, we allow servicing of both sides of some streets in a network, that is, a vehicle can service a street by zigzagging. We combine insertion and local search techniques to produce high-quality solutions to a set of test instances. In the second variant, we design a cluster-first, route-second heuristic that compares favorably to an existing heuristic and produces routes that are intuitively appealing. Finally, we show how to partition a street network into routes that are compact, balanced, and visually appealing.Item An Analysis of Thermally Induced Arcing Failure of Electrical Cable(2013) Fisher, Ryan Patrick; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Arc failure of Southwire Romex Simpull non-metallic sheathed 14/2 American wire gauge (AWG) with ground cable due to external heat was examined. This type of cable was selected due to its widespread use in residential building wiring. This research is motivated by the fact that currently there are no widely accepted methods or models used to predict electric arc failure in cables exposed to thermal conditions or to determine whether an arc failure event was the cause or result of a fire. A variety of tests were performed at various temperatures to learn more about the arc failure of these cables. The cables were exposed to precise temperatures with a steady heating rate in a convection oven in order to best attempt to eliminate heat transfer through the cable. In order to explore the effect current may have on the time to arc failure of the cable, experiments at different temperatures were performed in both loaded and unloaded scenarios. During many of these tests, voltage and current measurements were collected during an arcing event. As part of the process of exploring the events leading up to arc failure, electrical resistance tests of the cable's insulation components were examined. A model was developed to predict time to arc failure at a variety of temperatures based on thermal degradation of the PVC insulation. The purpose of the developed model is to be able to predict cable failure based on known thermal conditions. The proposed values of the model developed are in examining a prior thermally induced electrical arcing incident or in determining the suitability of a cable in an abnormal thermal environment. The results of this research will be useful in continuing the research and education of the arc failure of electrical cables.Item FORENSIC INVESTIGATION TECHNIQUES FOR INSPECTING ELECTRICAL CONDUCTORS INVOLVED IN FIRES FOR ARC AND MELT BEADS(2012) Hussain, Nasir; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The objective of this research was to determine, experimentally, if distinguishing characteristics exist between the beads formed on energized and non-energized wires exposed to various thermal insults. Most of research published in the literature has not tested energized and non-energized wires under the same thermal conditions. The tests in this study were conducted using convective, radiative and combined convective/radiative thermal exposures. Wires were tested in both energized and non-energized states. Energized wires were tested under "load" and "no load" conditions. Beads formed on both the energized and non-energized wires as results of thermal exposure. Beads were analyzed externally and internally with stereo microscope, SEM/EDS, and a metallurgical microscope. No clear trends or distinguishing visual or microscopic characteristics between the beads formed on energized and non-energized wires were found. The bead analysis methods used during this research showed that it is not possible to distinguish between the beads formed on energized and non-energized wires exposed to various thermal insults.