Theses and Dissertations from UMD
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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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Item Formalized Application of Systems Engineering Processes to the Development of the Purple Line SharePoint Test Tracking Tool(2020) Mehta, Hanish Gaurang; Baras, John; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Testing & Commissioning (T&C) for a $2 Billion project generally consists of more than ten thousand tests, and the Purple Line Light Rail system being constructed in Maryland is no exception. The Purple Line Light Rail is expected to have at least twenty thousand tests conducted in its T&C phase over the next 3-4 years. Given the number of tests, their pre-requirements, resources (manpower, equipment, facilities) and the test reporting procedures to be used to comply with the Maryland Transit Administration (MTA), the Purple Line Transit Constructors (PLTC) felt a need for an online system that could be used to log and track tests. This Thesis focuses on the formalized application of Systems Engineering processes, in accordance with ISO/IEC/IEEE 15288:2015, to the development of this test tracking tool. The Stakeholder requirements given by MTA and PLTC are converted to System requirements, and a Test Plan for the tool is developed in parallel. The tool is designed by PLTC in collaboration with a subcontractor to meet the System requirements and will be tested before going live.Item A SYSTEMS RELIABILITY APPROACH TO MODELING OPERATIONAL RISKS IN COMPLEX ENGINEERED SYSTEMS(2018) Komey, Adiel Ayi; Baecher, Gregory B; Modarres, Mohammad; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Since the beginning of the industrial revolution in the late 18th century, the cause of many serious accidents in hydrosystems engineering has shifted from natural causes to human and technology related causes as these systems get more complex. While natural disasters still account for a significant amount of human and material losses, man-made disasters are responsible for an increasingly large portion of the toll, especially in the safety critical domain such as Dam and Levee systems. The reliable performance of hydraulic flow-control systems such as dams, reservoirs, levees etc. depends on the time-varying demands placed upon it by hydrology, operating rules, the interactions among subsystem components, the vagaries of operator interventions and natural disturbances. In the past, engineers have concerned themselves with understanding how the component parts of dam systems operate individually and not how the components interact with one another. Contemporary engineering practices do not address many common causes of accidents and failures, which are unforeseen combinations of usual conditions. In recent decades, the most likely causes of failures associated with dams have more often had to do with sensor and control systems, human agency, and inadequate maintenance than with extreme loads such as floods and earthquakes. This thesis presents a new approach, which combines simulation, engineering reliability modeling, and systems engineering. The new approach seeks to explore the possibilities inherent in taking a systems perspective to modeling the reliability of flow-control functions in hydrosystems engineering. Thus, taking into account the interconnections and dependencies between different components of the system, changes over time in their state as well as the influence upon the system of organizational limitations, human errors and external disturbances. The proposed framework attempts to consider all the physical and functional interrelationships between the parts of the dam and reservoir, and to combine the analysis of the parts in their functional and spatial interrelationships in a unified structure. The method attempts to bring together the systems aspects of engineering and operational concerns in a way that emphasizes their interactions. The argument made in this thesis is that systems reliability approach to analyzing operational risks—precisely because it treats systems interactions—cannot be based on the decomposition, linear methods of contemporary practice. These methods cannot logically capture the interactions and feedback of complex systems. The proposed systems approach relies on understanding and accurately characterizing the complex interrelationships among different elements within an engineered system. The modeling framework allows for analysis of how structural changes in one part of a system might affect the behavior of the system as a whole, or how the system responds to emergent geophysical processes. The implementation of the proposed approach is presented in the context of two case studies of US and Canadian water projects: Wolf Creek Dam in Kentucky and the Lower Mattagami River Project in Northern Ontario.Item A Graph Transformation Method for Robotic Satellite Servicing Down-Selection(2017) Knizhnik, Jessica; Austin, Mark; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As remote robotic space satellite servicing technologies develop, each servicer satellite will need to account for a number of servicing scenarios and consider a variety of alternate design solutions to best meet the most servicing scenario requirements. This thesis presents a graph transformation method for systematically down-selecting the number of design options available, and highlighting trade-offs in sets of design solutions which best meet satellite servicing task requirements while also reducing total mass, maximum power needed and servicing time. The proposed method successfully identifies for further consideration several best design solutions from a set of approximately 10,000 potential solutions in the first test case examined, and from a set of approximately 2*1026 in the second test case examined.Item FLOOR (Framework for Linking Ontology Objects and Textual Requirements): A New Requirements Engineering Tool that Provides Real-time Feedback(2017) Zontek-Carney, Edward James; Austin, Mark A; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cost overruns on complex system-of-systems development programs frequently trace back to problems with requirements. For increasingly complex systems, a key capability is the identification and management of requirements early in a system’s life cycle, when errors are cheapest and easiest to correct. Significant work has been done to apply natural language processing (NLP) to the domain of requirements engineering. Recently, requirements engineering tools have been developed that use NLP to leverage both domain ontologies and requirement templates, which define acceptable sentence structures for requirements. Domain ontologies provide terminology consistency, and enable rule-checking during the testing of requirements. This thesis introduces FLOOR, a new software tool for requirements engineering that leverages NLP. FLOOR not only integrates domain ontologies and requirement templates, but also supports importing multiple external domain ontologies.Item Mission and Scenario Planning for Unmanned Aerial Vehicles (Path Planning and Collision Avoidance Systems)(2016) Shadab, Niloofar; Xu, Huan; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As unmanned autonomous vehicles (UAVs) are being widely utilized in military and civil applications, concerns are growing about mission safety and how to integrate dierent phases of mission design. One important barrier to a coste ective and timely safety certication process for UAVs is the lack of a systematic approach for bridging the gap between understanding high-level commander/pilot intent and implementation of intent through low-level UAV behaviors. In this thesis we demonstrate an entire systems design process for a representative UAV mission, beginning from an operational concept and requirements and ending with a simulation framework for segments of the mission design, such as path planning and decision making in collision avoidance. In this thesis, we divided this complex system into sub-systems; path planning, collision detection and collision avoidance. We then developed software modules for each sub-systemItem Optimization Models for Speed Control in Air Traffic Management(2015) Jones, James Calvin; Lovell, David J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In a typical air traffic control environment, the precise landing times of en route aircraft are not set until each aircraft approaches the airspace adjacent to the destination airport. In times of congestion, it is not unusual for air traffic controllers to subject arriving aircraft to various maneuvers to create an orderly flow of flights onto an arrival runway. Typical maneuvers include flying in zig-zag patterns, flying in race track shaped patterns and tromboning. These maneuvers serve to delay the arrival time of the flight while also burning additional fuel. On the other hand, if the arrival time was established much earlier, then such delay could be realized by simply having flights fly slower while still at a higher altitude, which would incur much less fuel burn than the described maneuvers. Yet despite its potential benefit, thus far little has been done to promote the management of flights using speed control in the presence of uncertainty. This dissertation presents a set of models and prescriptions designed to use the mechanism of speed control to enhance the level of coordination used by FAA managers at the tactical and pre-tactical level to better account for the underlying uncertainty at the time of planning. Its models deal with the challenge of assigning delay to aircraft approaching a single airport, well in advance of each aircraft’s entry into the terminal airspace. In the first approach, we assume control of all airborne flights at a distance of 500 nm while assuming no control over flights originating less than 500 nm from the airport. We propose a set of integer programming models designed to issue arrival times for controlled flights in the presence of the uncertainty associated with the unmanaged flights. In the second approach, we assume control over all flights by subjecting flights to a combination of air and ground delay. Both approaches show strong potential to transfer delay from the terminal to the en route phase of flight and achieve fuel savings. Building on these ideas we then formulate an approach to incorporate speed control into Ground Delay Programs. We propose enhancements for equitably rationing airport access to carriers and develop a revised framework to allow carriers to engage in Collaborative Decision Making. We present new GDP control procedures and also new flight operator GDP planning models. While the ability to achieve all the benefits we describe will require NextGen capabilities, substantial performance improvements could be obtained even with a near-term implementation.Item Storage-Centric Wireless Sensor Networks for Smart Buildings(2013) Wang, Baobing; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the first part of the dissertation, we propose a model-based systems design framework, called WSNDesign, to facilitate the design and implementation of wireless sensor networks for Smart Buildings. We apply model-based systems engineering principles to enhance model reusability and collaboration among multiple engineering domains. Specifically, we describe a hierarchy of model libraries to model various behaviors and structures of sensor networks in the context of Smart Buildings, and introduce a system design flow to compose both continuous-time and event-triggered modules to develop applications with support for performance evaluation. WSNDesign can obtain early feedback and high-confidence evaluation of a design without requiring any intrusive and costly deployment. In addition, we develop a graphical tool that exposes a sequence of design choices to system designers, and provides instant feedback about the influence of a design decision on the complexity of system analysis. Our tool can facilitate comprehensive analysis and bring competitive advantage to the systems design workflow by reducing costly unanticipated behaviors. One of the main challenges to design efficient sensor networks is to collect and process the data generated by various sensor motes in Smart Buildings efficiently. To make this task easier, we provide an abstraction for data collection and retrieval in the second part of the dissertation. Specifically, we design and implement a distributed database system, called HybridDB, for application development. HybridDB enables sensors to store large-scale datasets in situ on local NAND flash using a novel resource-aware data storage system, and can process typical queries in sensor networks extremely efficiently. In addition, HybridDB supports incremental $\epsilon$-approximate querying that enables clients to retrieve a just-sufficient set of sensor data by issuing refinement and zoom-in sub-queries to search events and analyze sensor data efficiently. HybridDB can always return an approximate dataset with guaranteed maximum absolute ($L_\infty$-norm) error bound, after applying temporal approximate locally on each sensor, and spatial approximate in the neighborhood on the proxy. Furthermore, HybridDB exploits an adaptive error distribution mechanism between temporal approximate and spatial approximate for trade-offs of energy consumption between sensors and the proxy, and response times between the current sub-query and the following sub-queries. The implementation of HybridDB in TinyOS 2.1 is transformed and imported to WSNDesign as a part of the model libraries.Item An Optical Density Detection Platform with Integrated Microfluidics for In Situ Growth, Monitoring, and Treatment of Bacterial Biofilms(2012) Mosteller, Matthew Philip; Ghodssi, Reza; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Systems engineering strategies utilizing platform-based design methodologies are implemented to achieve the integration of biological and physical system components in a biomedical system. An application of this platform explored, in which an integrated microsystem is developed capable of the on-chip growth, monitoring, and treatment of bacterial biofilms for drug development and fundamental study applications. In this work, the developed systems engineering paradigm is utilized to develop a device system implementing linear array charge-coupled devices to enable real time, non-invasive, label-free monitoring of bacterial biofilms. A novel biofilm treatment method is demonstrated within the developed microsystem showing drastic increases in treatment efficacy by decreasing both bacterial biomass and cell viability within treated biofilms. Demonstration of this treatment at the microscale enables future applications of this method for the in vivo treatment of biofilm-associated infections.Item SYSTEMS ENGINEERING DESIGN AND TRADEOFF ANALYSIS WITH RDF GRAPH MODELS(2012) Nassar, Nefretiti Nazarine; Austin, Mark; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As engineering systems become increasingly complex the need for automation arises. This thesis proposes a multi-level framework for design of a home theater system cast as a component-selection design problem. It explores the extent to which the resource description framework (RDF) and Python can be used in a software pipeline for systems engineering design and trade-off analysis. The software pipeline models and visualizes RDF graphs, implements inference rules for the step-by-step selection of design component combinations that satisfy system requirements, identifies non-inferior Pareto-Optimal design solutions, and tracks the size of the RDF graphs during execution of the pipeline. The use of RDF and Python for automation provides a simplified replacement for present-day Semantic Web tools and technologies.