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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Now showing 1 - 4 of 4
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    SILICON NITRIDE INTEGRATED PHOTONIC DEVICES AND THEIR APPLICATIONS IN ASTRONOMY AND QUANTUM PHYSICS
    (2022) Zhan, Jiahao; Dagenais, Mario; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The photonics technology has revolutionized the telecommunication industry in the past 40 years with the deployment of the undersea fiber-optic network. Nowadays, with the maturity of silicon photonics technology, the integrated photonic platform is enabling more and more cutting-edge technologies, such as optical transceivers for data center connectivity, automotive LiDARs for self-driving vehicles, the next-generation astronomical instrumentation and nearterm photonic quantum computers, to name a few. In recent years, silicon nitride (Si3N4) material has attracted a significant amount of attention mainly due to the ultra-low loss that can be achieved. Compared to silicon, Si3N4 has a much wider transparency window, and does not suffer from two-photon absorption and free-carrier absorption over the telecommunication band. The relatively low refractive index of Si3N4 also means less sensitivity of optical modes to the waveguide sidewall roughness, therefore reducing the scattering loss. In this dissertation, I will first give an introduction of integrated photonics, and a brief overview of some novel applications and current trends. Next I will graphically show our methods for device fabrication and characterization, and then demonstrate a few integrated photonic devices implemented on the Si3N4 material platform, including Bragg gratings, multimode interferometers, polarization beam splitters, and polarization rotators, with an in-depth discussion of their potentialapplications, principles of operation, simulation and experimental results. I will then embark on a new chapter on arrayed waveguide gratings (AWGs), with emphasis on its application in integrated astronomical spectrometers. To obtain a continuous two-dimensional spectrum, cleaving at the output focal plane of the AWGis required. I will discuss and demonstrate a three-stigmatic-point AWG, which provides an elegant solution to the non-flat focal plane issue in traditional Rowland AWGs. This work is a critical step towards the development of an efficientand miniaturized astronomical spectrograph for the upcoming extremely-large telescopes. Next, I will introduce a one-dimensional nanobeam cavity enabled by a slow-light waveguide. A cubic relation between the quality factor and the length of the cavity will be derived and experimental verification will be demonstrated. The current progress towards the investigation of the Purcell effect of this nanobeam cavity will be discussed, including the platform and the loss characterization of the deposited amorphous silicon material. In the final chapter, I will first summarize the major conclusions from the previous chapters. Then I will briefly discuss some future research directions extending the work in this thesis, including ultra-broadband polarization beam splitter, the development of an on-chip Bell state analyzer, and the design of a polarization-insensitive flat-focal-field spectrometer.
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    Application of the Abstract: Making Sustainable and Solar Design a Reality through LEAFHouse
    (2007-12-17) Singleton, Kimberly; Gardner, Amy E.; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    'Sustainability' and 'green design' are two terms that have become more common in both professional practice and architectural education. They are merely abstract terms however; concepts which many students find difficult to grasp at a high enough level for thorough implementation in a design project. As a result, sustainable and solar techniques become more of an afterthought, giving students a cursory, at best, understanding of the principles, preventing an understanding of how to implement the principles. Reflecting on the process, product, challenges and achievements of both the 2007 Solar Decathlon team and the LEAFHouse, this thesis posits the importance of hands-on, interdisciplinary design and construction work for the understanding and implementation of sustainable techniques and solar technologies. In addition, it suggests a change in the way that the built environment is conceived, designed and constructed, through the collaboration of practitioners and industry professionals from a range of disciplines.
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    Sensory Integration During De-adaptation to Visuomotor Distortions
    (2006-08-31) King, Bradley Ross; Clark, Jane E.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Previous research has demonstrated that adults can adapt to novel sensorimotor perturbations, a process thought to be achieved by the gradual update of an adaptive internal representation. However, few research studies have investigated the persistence of a newly acquired representation, as assessed by the reduction of performance errors after the perturbation has been removed (i.e., de-adaptation). The primary objective of this thesis was to determine if the central nervous system (CNS) could flexibly utilize visual and proprioceptive afference to de-adapt to novel sensorimotor perturbations. It has been previously demonstrated that the CNS relies more heavily on visual information for hand localization in the azimuthal direction whereas proprioception is more heavily weighted for hand localization in the radial direction. Seventy-two right-handed adults executed reaching movements during exposure to either an incremental visuomotor rotation or gain distortion. Visual feedback provided during post-exposure was manipulated. Results indicate that the CNS predominantly utilized visual afference to de-adapt to both perturbations, despite the fact that rotation adaptation resulted in movement errors in the azimuthal direction whereas gain adaptation resulted in movement extent errors. These data suggest that the CNS did not flexibly re-weight proprioceptive afference in the absence of visual feedback during a center-out drawing task.
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    Experimental and Theoretical Investigation of Integrated Engine Generator - Liquid Desiccant System
    (2005-11-30) Nayak, Sandeep M; Radermacher, Reinhard; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Combined heat and power (CHP) involves on-site generation of electricity by using gas-fired equipment along with utilization of waste heat available from the power generation process. This research focuses on the design, installation and analysis of integration options of a modular CHP system involving the integration of a natural gas fired reciprocating engine generator with a liquid desiccant dehumidification system in a medium sized commercial office building. The engine generator provides 75 kW of electrical power fed parallel to the grid while the combined waste heat from the exhaust gases and jacket water from the engine is used to regenerate the liquid desiccant. The liquid desiccant unit dehumidifies the outdoor air and supplies it to the mixed air section of the roof top unit of the building. The experimental part of the research discusses the various aspects involved in the design and installation of the system such as the mechanical design of the structure, the heat recovery loop design and the electrical interconnection with the grid. Extensive testing and data analysis was conducted to characterize the performance of the integrated system and compare the performance with a traditional power plant as well as conventional HVAC systems. A comprehensive steady state thermodynamic model of the integrated CHP system was coded in Visual Basic .Net. After validation with experimental results, an economic and climate model was integrated into the thermodynamic model with actual electricity and gas prices as well as the climate data for different representative states in the United States to demonstrate the feasibility of the system under different scenarios. This research addresses and assesses the different integration opportunities and issues encountered during the integration of the engine generator - liquid desiccant system with the existing electrical grid and the roof top unit. Based on the hands-on experience gained during the design, installation, operation and maintenance of the integrated system as well as the results obtained from extensive simulation of the system, this research develops valuable design guidelines on the integration and operation of the packaged engine generator-liquid desiccant system in commercial office buildings for future designers and system integrators.