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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    A REDESIGN OF THE EXHAUST AND GAS SAMPLING SYSTEM OF THE FIRE PROPAGATION APPARATUS
    (2022) Roy, Shuvam; Stoliarov, Stanislav; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Standard bench scale fire apparatuses are useful tools to perform repeatable and reproducible firetests that acquire key fire properties, such as heat release rate and time to ignition, for materials in a cost-effective manner. The Fire Propagation Apparatus (FPA) is one of the only standard bench scale apparatuses that has the ability to acquire these key fire properties in a controlled environment setting. However, the design of the apparatus is quite complex. In this work, the exhaust and gas sampling system designs were redesigned and constructed to increase modularity and manufacturability, adapt to the University of Maryland’s Department of Fire Protection Engineering laboratory settings, and provide greater ease for the end user operations. After the construction of the FPA systems, tests were conducted to verify the accuracy of the measurement devices. Equations for the calculation of heat release rate from FPA sensor data were derived and used for a series of combustion experiments. These equations were compared to the ones provided in the standard to gain insight on their systematic differences.
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    LONG-TERM IMPACTS OF AMAZON FOREST DEGRADATION ON CARBON STOCKS AND ANIMAL COMMUNITIES: COMBINING SOUND, STRUCTURE, AND SATELLITE DATA
    (2020) Rappaport, Danielle I; Dubayah, Ralph; Morton, Douglas; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Amazon forest plays a vital role in the Earth system, yet forest degradation from logging and fire jeopardizes carbon storage and biodiversity conservation along the deforestation frontier. Polices to reduce forest carbon emissions (REDD+) will fall short of their intended goals unless carbon and biodiversity losses from forest degradation can be monitored over time. Emerging remote sensing tools, lidar and ecoacoustics, provide a means to monitor carbon and biodiversity across spatial, temporal, and taxonomic scales to address data gaps on species distributions and time-scales for recovery. This dissertation draws from a novel multi-sensor perspective to characterize the long-term ecological legacy of Amazon forest degradation across a 20,000 km2 landscape in Mato Grosso, Brazil. It combines high-density airborne lidar, 1100 hours of acoustic surveys, and annual time series of Landsat data to pursue three complementary studies. Chapter 2 establishes the bedrock of the investigation by using fine-scale measurements of structure sampled across a large diversity of degraded forests to model the initial loss and time-dependent recovery of carbon stocks and habitat structure following fire and logging. Chapter 3 models the interactions between sound and structure to predict acoustic community variation, and to account for attenuation in dense tropical forests. Lastly, Chapter 4 uses sound to go beyond structure to identify the specific degradation sequences and pseudo-taxa that give rise to variation in the ‘acoustic guild’ over time. Soundscapes reveal strong and sustained shifts in insect assemblages following fire, and a decoupling of biotic and biomass recovery following logging that defy theoretical predictions (Acoustic Niche Hypothesis). The synergies between lidar and acoustic data confirm the long-term legacy of forest degradation on both forest structure and animal communities in frontier Amazon forests. After multiple fires, forests become carbon-poor, habitats become simplified, and animal communication networks became quieter, less connected, and more homogenous. The combined results quantify large potential benefits to protecting already-burned Amazon forests from recurrent fires. This dissertation paves the way for greater integration of remote sensing and analysis tools to enhance capabilities for bringing biomass and biodiversity monitoring to scale. Building on this research with species-level and multi-temporal measurements will reduce uncertainty around the breakpoints that drive carbon and biodiversity loss following degradation.
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    Strategies for Improved Fire Detection Response Times in Aircraft Cargo Compartments
    (2020) Wood, Jennifer Marie; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Prompt fire detection in cargo compartments on board transport aircraft is an important safety feature. Concern has been expressed for the activation time of contemporary detection technologies installed on aircraft. This project will deliver a continuation of research on the issues that have been identified relative to fire detection improvements in cargo compartments on aircraft, with a particular emphasis on freighters. Gas sensors and dual wavelength detectors were demonstrated in a previous phase to be responsive to fires in the previous experiment program. Detectors placed inside a Unit Loading Device (ULD) responded quickly to the array of fire sources. Thus, a further exploration of these observations is conducted including wireless technology along with an analysis of the effects of leakage rates on fire signatures inside ULDs. One primary goal is to assess the differences in fire detection time for detectors located within ULD versus those located on the ceiling of the cargo compartment for fires which originate in a ULD. The results indicated the detector location with the shortest activation time is inside of the ULD. Within the ULD, the wireless detector outperformed both air sampling detectors, however, the results could vary if threshold levels were more restrictive.
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    VERIFICATION TESTS OF MASS CONSERVATION FOR FIREFOAM AND DEVELOPMENT OF A USER'S GUIDE
    (2019) Wu, Shiyun; Trouvé, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The objective of this study is to develop basic verification tests for FireFOAM, a large eddy simulation (LES) solver developed by FM Global for fire applications, and based on the general-purpose Computational Fluid Dynamics (CFD) solver called OpenFOAM. These tests will be eventually included in an upcoming User Guide for FireFOAM users. We focus here on a series of tests developed to evaluate global species mass conservation statements. The series includes a two-dimensional helium plume case, a three-dimensional helium plume case and a three-dimensional pool fire case. The two-dimensional helium plume case focuses on the effects of changing the temporal discretization scheme in FireFOAM. The three-dimensional helium plume case focuses on the effects of changing the spatial discretization scheme used to describe the convection terms in the governing equations. Finally, the three-dimensional pool fire case focuses on the effects of changing the number of outer loops used to provide coupling between the governing equations that are solved sequentially. The results of the tests provide valuable insight for FireFOAM users who need to make numerical choices on the temporal discretization scheme, the spatial discretization scheme and the number of outer loops with little guidance on the impact of these choices.
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    SIMPLIFIED STRUCTURAL DESIGN APPROACH FOR OPEN COMPARTMENTS IN THE CASE OF FIRE
    (2018) Nassiri, Parisa; Torero, Jose L.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A vast majority of modern commercial and office buildings are designed to allow for maximum tenant flexibility. This results in a high demand for open floor plans and for versatility in compartmentation and architecture. The need for a thorough understanding of the behavior of a fire in such spaces is necessary for the improvement of codes and standards as well as for performance-based design. By considering the thermal properties of typical structural materials the energy equation is studied to establish if a simplified formulation of the thermal boundary condition can be used. The simplified formulation is defined by the characteristic heating time scales and the sensitivity of the structure to develop temperature gradients. Understanding the way in which a structure heats enables engineers to establish an adequate formulation of the fire. A series of full-scale large compartment fires were conducted in order to study the influence on fire behavior on open floor plan spaces in a project called ‘Real Fires for the Safe Design of Tall Buildings’. This work presents the results from some experiments of the series. The focus is to quantify the fire behavior in what pertains the performance assessment of structural elements. The main objective is to deliver a simplified design approach based on a detailed analysis of the data. Analysis shows that simplifications can be made for boundary conditions and temperature evolution inside materials in specific conditions.
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    Predicting Fire Sprinkler Sprays
    (2018) Myers, Taylor; Marshall, Andre W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Accurate representation of fire sprinkler spray enables quantitative engineering analysis of fire suppression performance. Increasingly, fire sprinkler systems are evaluated using computer fire models in which sprinkler spray is simulated with Lagrangian particles. However, limited guidance exists as to how to predict the formation of complex, spatio-stochastic fire sprinkler spray or how to accurately represent the dispersion of spray in terms of Lagrangian particles. The current work predicts the fire sprinkler spray generated by a canonical axisymmetric sprinkler using a Deflection Atomization Dispersion (DAD) framework, developed as a predictive modeling approach generalizable to typical fire sprinklers. In a DAD framework, spray evolution is divided into three stages: deflection of the water jet by the sprinkler deflector, atomization of the resulting thin fluid sheets into an initial spray, and dispersion of the initial spray into far-field spray. Deflection is described as a free-surface flow and is modeled deterministically using a boundary integral method (BIM). Atomization of the deflected fluid sheet is described by linear-stability theory to develop scaling laws relating sheet characteristics to statistically distributed, spatially resolved initial spray characteristics including breakup radius, volume flux, drop size, and drop velocity. The resulting initial spray is then described by a multivariate probability distribution function that varies over the predicted initialization surface. This function is stochastically sampled to generate Lagrangian particles representative of the near-field spray and the dispersion of these Lagrangian particles is in turn simulated in FireFOAM (an open source computational fluid dynamics fire model) to predict the far-field spray. Modeled results are compared to highly resolved near- and far-field measurements of axisymmetric sprinkler sprays generated by the Spatially-Resolved Spray Scanning System (4S). The end results shows agreement across all three stages of modeling with less than 10\% error when compared to experimental measurements. Further, the newly implemented model shows a stronger ability to capture spray induced airflow when compared to a baseline model. This work is the first to predict sprinkler spray dispersion entirely from sprinkler deflector geometry and operating pressure.
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    Furrow
    (2017) Neal, Laura; Collier, Michael; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Furrow is a testimony of leaving and returning, challenging the quotidian perception of country life primarily rooted in rural South Carolina. The speaker is a silent observer, a witness, and at times an unwilling participant who interrogates the connections and disconnections between family and the natural world.
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    LAND USE AND LAND COVER CHANGE AS A DRIVER OF ECOSYSTEM DEGRADATION ACROSS BIOMES
    (2016) Noojipady, Praveen; Prince, Stephen D; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The expansion and intensification of agricultural production in human-dominated landscapes threaten efforts to sustain natural ecosystems and maintain agricultural production in a changing climate. Long-term use of agricultural lands, combined with conversion of natural ecosystems for agricultural production, can rapidly degrade the health of remaining natural ecosystems. The fundamental goal of this dissertation was to assess the impacts of anthropogenic degradation on stocks and sequestration of carbon. Although degradation alters a range of ecosystem services, case studies of ecosystem degradation in this dissertation focus on reductions in vegetation productivity, carbon stocks, and the extent of natural forest cover as a result of human activity. Time series of satellite remote sensing data were used to track forest and rangeland degradation in the southwestern United States, forest carbon emissions from cropland expansion in the Brazilian Cerrado, and fire-driven forest conversion for oil palm plantations in Southeast Asia. Three major themes link the regional case studies: expansion and intensification of agricultural production, market demand and certification, and agricultural management in response to climate variability. Conclusions from the dissertation underscore the widespread influence of land management on vegetation productivity and forest carbon stocks. In the Southwest United States, reductions in net primary production on managed lands were higher in forested landscapes than other cover types. In contrast, Native American Indian Reservations, often considered to be more degraded, actually had smaller absolute reductions in net primary productivity during 2000-2011. Multi-year droughts in the southwest present new challenges for managing forests and rangelands, and climate projections suggest dry conditions will intensify in the coming century. In Southeast Asia, industry-led efforts to certify sustainable palm oil production were evaluated using satellite data on fires and forest loss. Rates of fire-driven deforestation and total fire activity declined following certification, highlighting the potential for certification to reduce ignitions during El Niño years and protect remaining fragments of lowland and peat forest. Aligning certification criteria for sustainable palm oil with satellite monitoring capabilities may help accelerate compliance with environmental legislation and market demands for deforestation-free products. In Brazil, government and industry actions to limit Amazon deforestation have largely overlooked the neighboring Cerrado biome. Forest carbon emissions from deforestation for soy expansion in the Cerrado increased substantially after the implementation of the Soy Moratorium in the Brazilian Amazon, partially offsetting recent reductions in Amazon deforestation carbon emissions. The success of policies to support sustainable agricultural production therefore depends on efforts to minimize cross-biome leakage and the ability to monitor compliance and unintended consequences. Solutions for management must also confront the growing influence of climate variability. Time series of satellite data may allow early detection of degradation impacts and support efforts to mitigate the influence of sustained agricultural production on natural systems. Changes in vegetation carbon stocks from ecosystem degradation varied across case studies, underscoring the diverse nature of direct and indirect drivers of degradation across different land use systems. Direct human drivers of ecosystem degradation in the southwest United States from management of livestock grazing resulted in gradual changes in vegetation productivity, whereas mining and oil extraction areas showed large and permanent reductions. Forest carbon emissions from agriculture expansion in the Cerrado were a one-time process, as native vegetation is cleared for cropland expansion. In contrast, the carbon emissions from Southeast Asia’s forest and peatland conversion involve both sudden and gradual processes, as carbon accumulation in oil palm plantations partially compensates for emissions from forest conversion. Overall, this research made contributions to understanding of the regional impacts of human activity and the potential for climate change mitigation from sustainable land use practices in human-dominated landscapes.
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    Contemporary Forest Cover Dynamics in Myanmar
    (2016) Biswas, Sumalika; Justice, Christopher O.; Vadrevu, Krishna P.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Understanding forest cover dynamics is important for a nation’s environmental, social and political commitments. In the past decade, Myanmar had the highest deforestation rate, in mainland South East Asia (Hansen et al., 2013). Further, in 2009, Myanmar embarked on a landmark political change from military regime to democratic transition which significantly impacted its forest cover. Myanmar also ranks first with respect to forest fires in South/Southeast Asia. In Myanmar, forest cover loss and fire are intrinsically linked through the traditional taungya system of slash and burn. Thus, quantifying factors controlling forest fires in Myanmar is an important topic that needs attention. Although the Myanmar government established protected areas throughout the country to conserve forests, their effectiveness remains unevaluated. This dissertation aims to understand the current status of forest cover dynamics in Myanmar. The five chapters in this dissertation address the impact of the political transition on forest cover loss and fragmentation, fire disturbance in tropical evergreen and deciduous forests including the factors controlling vegetation fires in the protected and non-protected forests. The dissertation contributes to the existing knowledge in land cover and land use change science (LCLUC), ii especially the impact of institutional changes on forest cover in the tropics. The analysis of the relationship between forest loss, fire and effectiveness of the protected areas addressed in the study, contributes to regional knowledge on fire and conservation science respectively. The findings of this dissertation depict that in Myanmar, the political transition to democracy significantly influenced its forest cover. Our analysis showed that during 2001-2014, a total loss of 2,030,101 ha of forest occurred at the rate of 145,007.21 ha/year with a linear increase of 15,359 (±1793) ha/year. The observed increase in variance in between 2008-2011 coincides with political transition period which started with the formation of the new Constitution in 2008 and ended with the military government handing over power to the democratic government in 2011. Analysis of trend and variance patterns of two landscape fragmentation metrics (Number of Patches and Mean Patch Area) at the provincial level show the influence of the political transition on landscape fragmentation. The impact of political transition was more pronounced in provinces associated with plantations and urban areas. Among the rubber producing States, the border States, Shan, Kayah, and Kayin were more impacted compared to inland Mon. Tanintharyi and Bago Regions showed higher variance in residuals of both metrics before the transition occurred due to the military government supported oil palm and teak plantations. Fragmentation and the variance in fragmentation metrics in Kachin increased post 2008. Apart from plantation areas, urban areas like Yangon and Mandalay showed high fragmentation post 2009 period after the new government was formed. We attribute the forest loss and fragmentation to the economic and structural reforms of the democratic government, specifically to the increased granting of agricultural concessions and logging for plantations. iii A study of the fire regime from 2003 to 2012 using MODIS satellite data suggested March as the peak of the fire season with 12900 km2 of Burned Area (BA) and 95000 fire counts. Forests accounted for majority (41.3%) of the total BA and most fires (89.7%) resulted in medium or high vegetation disturbance. A higher negative correlation between BA and Gross Primary Productivity (GPP) was reported for deciduous forests than for evergreen forests (r=0.49 vs r = 0.36, p ~ 0). A maximum decrease in 29% of original GPP (2007-2012) was observed in the evergreen forest patches. The scale-dependent correlation analysis suggested significant BA-GPP correlation at 1 × 1 degree, as compared to finer resolutions. These results highlight the significance of fires impacting carbon cycle. An in-depth analysis of fire causative factors in Myanmar was studied. The mean fire density in non-protected areas was found to be two times more than in protected areas. Fire-land cover partition analysis suggested dominant fire occurrences in the savannas (protected areas) and woody savannas (non-protected areas). The five major fire causative factors in protected areas in descending order were found to be population density, land cover, tree cover percent, travel time from nearest city and temperature. The causative factors in non-protected areas were population density, tree cover percent, travel time from nearest city, temperature and elevation. The fire susceptibility analysis showed distinct spatial patterns with central Myanmar as a hot spot region of vegetation fires. Results from propensity score matching suggested that forests within protected areas have 11% less fires than non-protected areas. These findings provide information to policy makers about the current forest loss, forest fragmentation and forest fire hotspots, status of forest conservation and can be used to inform, update or evaluate policies. These findings are timely and can guide policy makers to arrive at best management strategies as the new government is formulating policies and laws and amending old ones to aid forest conservation.
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    A Generalized Model for Wall Flame Heat Flux During Upward Flame Spread on Polymers
    (2015) Korver, Kevin; Stoliarov, Stanislav; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A current model accurately predicts flame to surface heat flux during upward flame spread on PMMA based on a single input parameter, the mass loss rate. In this study, the model was generalized to predict the heat flux for a broad range of polymers by adding the heat of combustion as a second input parameter. Experimental measurements were conducted to determine mass loss rate during upward flame spread and heat of combustion for seven different polymers. Four types of heat of combustion values were compared to determine which generated the most accurate model predictions. The complete heat of combustion yielded the most accurate predictions (± 4 kW/m2 on average) in the generalized model when compared to experimental heat flux measurements collected in this study. Flame heat flux predictions from FDS direct numerical simulations were also compared to the generalized model predictions in an exploratory manner and found to be similar.