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Recent Submissions

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    Microbial Methane Oxidation and Community Dynamics in Southern Ontario Landfill Cover Soils
    (University of Waterloo, 2026-05-08) Willms, Nathanael
    Methane emissions from municipal solid waste landfills contribute to ~10% of global methane emissions, significantly contributing to climate change. Methanotrophic bacteria present in landfill cover soils (LCS) can mitigate these emissions by oxidizing methane. In capped landfills, surface methane emissions are often concentrated at highly emissive ‘hot spots’. The spatial distribution and overall levels of methane emissions vary over daily, seasonal, and multi-year timescales, driven by landfill age and meteorological factors. Methanotrophic community composition in LCS also varies spatially and temporally in response to methane emissions, soil moisture content, temperature, pH, and nutrient availability. The research presented in this thesis surveys community composition, methane flux, and soil chemistry across a decommissioned capped landfill cover over a total period of 8 years. The overall objectives were to assess how soil bacterial and archaeal communities changed in response to shifting methane dynamics, as well as the role of key physicochemical factors in driving changes in the relative abundances of methanotrophic taxa. Surveying methane flux and soil methane concentrations at different sites across the landfill, I observed a long-term trend of disappearing methane at several former hot spots, concurrently with alterations to the landfill gas capture system that also saw two new hot spots emerge in a different area of the landfill. Active hot spots were lower in total nitrogen, NO3-, NO2-, and NH4+ relative to other sites, indicating that methanotrophy was likely N-limited in this landfill cover. Methane flux was significantly correlated with shifts in community composition, as were soil moisture content, pH, dissolved organic carbon, Ca2+, K+, Na+, and Cl-. Community profiling with 16S rRNA gene amplicon sequencing identified that active hot spots were dominated by methane oxidizing bacteria, especially by members of genera Methylobacter, Crenothrix, and Methylomicrobium, whereas sites without exposure to methane had much more diverse communities with methanotrophs constituting <1% of the community in all but one instance. Former hot spots, which experienced high methane emissions in 2020 that declined by 2022, saw an overall decline in total methanotroph relative abundance, but still maintained a higher relative abundance of methanotrophs than sites that had never been hot spots. Not all methanotrophic ASVs at these sites declined at the same rate, with some ASVs maintaining approximately the same relative abundance as during high methane efflux. Additionally, methane flux at the former hot spots was significantly more negative than at completely inactive sites, indicating oxidation of near-atmospheric concentrations of methane. These findings indicate the potential for “persistent” methanotrophs which, following methane enrichment, can survive at high proportions of a soil microbial community for long periods of time when methane availability becomes reduced and/or infrequent. Methanotrophs which pursue this ecological strategy could be crucial to the mitigation of methane emissions from older landfills with lower background levels of methane but sporadic, more intense efflux events, and could be employed in strategic microbial amendments to LCS.
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    Human Remote Sensing In Long-Term Care Facility Using Low-Cost FMCW Radar
    (University of Waterloo, 2026-05-08) Trinh, Huy
    This thesis studies privacy-preserving human remote sensing in Long Term Care (LTC) environments using low-cost 60 GHz FMCW radar. The main challenge we are addressing is the reliable sensing of weak or quasi-static human states in LTC environments, such as quiet occupancy, prolonged sitting or lying, and post-fall floor presence, which are clinically and operationally important yet difficult to detect with conventional methods. These scenarios are precisely the cases in which sensing reliability is most critical for resident safety, caregiver response, and building operation. The thesis, therefore, investigates how far a low-cost, low-resolution radar platform can be pushed through signal processing, machine learning methods, and simulation-driven data generation to deliver useful roomlevel awareness without relying on cameras or wearables. The work is organized around a practical deployment view rather than a single algorithmic contribution. It begins with the sensing hardware and baseline signal-processing chain, then develops methods for quasistatic occupancy detection and post-fall floor-occupancy detection, extends these ideas to imaging-style radar representations suitable for edge deployment, and finally studies simulation and digital-twin approaches for sim-to-real radar learning. Across these working stages, the unifying theme is the design of scalable, privacy-preserving, and energy-aware radar sensing methods for ambient assisted-living environments.
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    Making Meaning: Translating Traditional Korean Pattern Through Digital Fabrication
    (University of Waterloo, 2026-05-08) Gu, Jamie
    This thesis examines how patterns derived from Korean architectural references can be translated through contemporary fabrication without losing the relationships that make them spatially and culturally meaningful. Rather than treating pattern as a detachable surface effect, the research understands it as an architectural condition that mediates boundary, light, visibility, enclosure, and material presence through density, continuity, edge condition, thickness, and relief. Beginning from the observation that pattern changes when the conditions of making change, the thesis asks not whether a historical artefact can be reproduced exactly, but whether culturally grounded patterned relationships can remain legible through contemporary making. Through fieldwork in South Korea, pattern redrawing, and comparative prototyping across laser cutting, CNC milling, 3D printing, and mould-based casting, the research tests what survives translation, what transforms, and which design decisions preserve patterned coherence. The work evaluates these translations through criteria including density, edge clarity, continuity, relief, assembly logic, and threshold performance, considering both spatial effect and cultural continuity. The findings suggest that meaning does not depend on exact replication, but on whether key relationships among geometry, material, making, assembly, and spatial effect remain coherent through adaptation. The thesis therefore frames translation as a design responsibility and craft as a form of situated judgement exercised through both digital and material processes of making.
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    A Comprehensive Evaluation Framework for Synthetic ECG: Assessing Fidelity, Utility, and Privacy
    (University of Waterloo, 2026-05-08) Li, Yixin
    synthetic time-series data synthetic data generation privacy-enhancing technology time-series data evaluation electrocardiogram dynamic time warping membership inference attacks
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    Concordance in wetland physicochemical conditions, vegetation, and surroundign land cover is robust to data extraction approach
    (Public Library of Science, 2019-05-31) Kraft, Adam J.; Robinson, Derek T.; Evans, Ian S.; Rooney, Rebecca C.
    Concordance among wetland physicochemical conditions, vegetation, and surrounding land cover may result from the influence of land cover on the sources of plant propagules, on physicochemical conditions, and their subsequent determination of growing conditions. Alternatively, concordance may result if differences in climate, soils, and species pools are spatially confounded with differences in human population density and land conversion. Further, we expect that land cover within catchment boundaries will be more predictive than land cover in symmetrical buffers if runoff is a major pathway. We measured concordance between land cover, wetland vegetation and physicochemical conditions in 48 prairie pothole wetlands, controlling for inter-wetland distance. We contrasted land-cover data collected over a four-year period by multiple extraction approaches including topographically-delineated catchments and nested 30 m to 5,000 m radius buffers. After factoring out inter-wetland distance, physiochemical conditions were significantly concordant with land cover. Vegetation was not significantly concordant with land cover, though it was strongly and significantly concordant with physicochemical conditions. More, concordance was as strong when land cover was extracted from buffers <500 m in radius as from catchments, indicating the mechanism responsible is not topographically constrained. We conclude that local landscape structure does not directly influence wetland vegetation composition, but rather that vegetation depends on 1) physicochemical conditions in the wetland that are affected by surrounding land cover and on 2) regional factors such as the vegetation species pool and geographic gradients in climate, soil type, and land use.