Theses

Permanent URI for this collectionhttps://uwspace.uwaterloo.ca/handle/10012/6

The theses in UWSpace are publicly accessible unless restricted due to publication or patent pending.

This collection includes a subset of theses submitted by graduates of the University of Waterloo as a partial requirement of a degree program at the Master's or PhD level. It includes all electronically submitted theses. (Electronic submission was optional from 1996 through 2006. Electronic submission became the default submission format in October 2006.)

This collection also includes a subset of UW theses that were scanned through the Theses Canada program. (The subset includes UW PhD theses from 1998 - 2002.)

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Load Variation Resilient and Average Efficiency Enhanced Power Amplifiers for 5G/6G Beamforming System
(University of Waterloo, 2026-05-06) Yu, Hang
The deployment of Fifth Generation (5G) and Sixth Generation (6G) infrastructure relies heavily on high-frequency beamforming architectures to deliver high data rates and spectral efficiency. However, the physical realization of these systems faces critical challenges: the need for high circuit integration, energy efficiency under high Peak-to-Average Power Ratio (PAPR) signals, and robustness against dynamic load variations inherent in large-scale arrays. This doctoral thesis addresses these requirements through the development of three advanced integrated circuit objectives, progressing from theoretical derivations in load variation resiliency (Voltage-Standing-Wave-Ratio (VSWR) resiliency) to front-end architectural synthesis for Power Amplifiers (PAs). To improve circuit integration and performance for Time-Division Duplex (TDD) operation in beamforming systems, Chapter 3 focuses on the co-design of a Transmit/Receive (T/R) Front-End Module (FEM). Traditional FEMs suffer from insertion loss and area overhead due to additional Single-Pole Double-Throw (SPDT) switches. To resolve this, this work presents an architecture that integrates a Doherty Power Amplifier (DPA) in the transmit path, which also functions as a switchless T/R isolation network during receive operation. On the receiver side, an embedded switching network maximizes isolation and bandwidth while jointly optimizing the overall FEM performance and integration trade-offs. A 39 GHz prototype was fabricated using the GlobalFoundries 45nm Silicon-On-Insulator (SOI) CMOS process and achieves a Transmit (TX) mode gain of 15 dB, a saturated output power of 20 dBm, and a Power-Added Efficiency (PAE) of 23%/15% at peak and 6-dB back-off, respectively. In Receive (RX) mode, it delivers 20 dB of gain, a 4.5-dB noise figure, and an input 1-dB compression power of -16.5 dBm while consuming 32 mW. Occupying a core area of just 0.5 x 0.75 mm^2, this architecture demonstrates a highly competitive efficiency-noise-integration trade-off, achieving state-of-the-art performance for high-frequency FEMs. While integration and performance improvements are critical for beamforming systems, the load variation induced by antenna mutual coupling in Large-Scale Antenna Arrays (LSAAs) presents another critical challenge. Chapter 4 proposes a dual-mode PA design, utilizing different gate biasing to reconfigure its operational state. The work features a 'VSWR resiliency mode' to maintain robust performance under high load mismatch, and an 'Output-Back-Off (OBO) efficiency enhancement mode' to maximize efficiency under minimal load variation. Central to this design is a novel combiner network synthesized to support two distinct operational regimes: it can emulate the characteristics of balanced architectures (symmetric drain currents) for load-variation resiliency, or Doherty load modulation (asymmetric drain currents) for efficient OBO operation. A 29 GHz prototype was fabricated using GlobalFoundries' 22nm Fully-Depleted SOI CMOS process to validate the concept. Under a 50-ohm load, the VSWR-resilient mode achieves 16.5-dB gain, 12.5-dBm output power, and 18%/7.5% PAE at peak/6-dB OBO. The OBO efficiency-enhanced mode delivers 13-dBm output power with 19%/12.5% PAE at peak/6-dB OBO. Across a load of 2.5:1 VSWR over a 360-degree phase range, the VSWR-resilient mode exhibits only 0.5-dB average saturated-power degradation compared to 1~dB in the OBO efficiency-enhanced mode. Modulated measurements under varying VSWR loads further confirm the superior load-variation tolerance of the proposed architecture. The above-mentioned dual-mode approach offers flexibility between VSWR resiliency and efficiency improvements; however, communication protocols often demand simultaneous efficient and robust operation. Consequently, Chapter 5 unifies these requirements by establishing the theory and design of a "VSWR-Resilient DPA," extending the analytical framework of Chapter 4 to ensure robust performance across multiple power regimes. The analysis yields architectures that maintain the OBO efficiency profile of a DPA while simultaneously delivering load-variation insensitivity against Multiple-Input-Multiple-Output (MIMO) beamforming array mismatch. A prototype targeting 8 GHz is designed using a commercial MACOM GaN bare-die transistor on a multi-layer PCB substrate; however, due to procurement delays, experimental validation is deferred to future work. In EM circuit co-simulation, the architecture achieves 10-dB SS gain, 45-dBm saturated output power, and 49%/35% PAE at peak/6-dB OBO under a 50-ohm load, while maintaining less than 1.5-dBm saturated power variation and 1.55× normalized Class-B efficiency at 6-dB OBO across different antenna loads on the 3:1 VSWR circle.
Sustainable Strategies for Arctic Lifelines: Funding Decisions in the Face of Climate-Change Uncertainty
(University of Waterloo, 2026-05-06) GHOLAMI, HAMED
Remote Arctic communities rely on ephemeral winter roads for the affordable delivery of essential goods. As climate change destabilizes the physical foundation of these supply chains, policymakers face a complex stochastic allocation problem: how to optimally divide a constrained budget between supply-side infrastructure investments (to extend road duration) and demand-side consumer subsidies (to bolster household purchasing power). In this thesis, we develop a stylized stochastic optimization model to analyze this trade-off, formulating a capacity-budget gap parameter to capture the dual-bottlenecks of physical throughput versus financial liquidity. We prove that the optimal funding strategy, serving as a stochastic hedge, is strictly bounded between the supply-constrained and demand-constrained deterministic solutions. Through comparative statics, we uncover counter-intuitive operational tradeoffs, including a price-affordability tradeoff and a logistics efficiency tradeoff, where improvements in supply chain economics rationally trigger infrastructure divestment due to an underlying income saturation effect. Furthermore, we analyze the compound effect of climate change: a secular decline in mean winter duration combined with rising interannual volatility. We demonstrate that for the most vulnerable communities, this compound shock pushes the system into a dilution state where higher volatility counter-intuitively reduces the optimal investment level. Our findings suggest that as climate uncertainty accelerates and mean operational windows shrink, relying on winter road infrastructure becomes economically unsustainable, necessitating a strategic policy pivot toward direct income support and alternative logistics.
Feature Representation for Sea Ice Mapping
(University of Waterloo, 2026-05-06) Noa Turnes, Javier
Sea ice monitoring is essential for climate research, Arctic navigation, and operational decision-making. Synthetic aperture radar (SAR) imagery is the primary sensing modality used by national ice services because of its independence of atmospheric and lighting conditions, and sensitivity to surface structure. However, SAR-based sea ice classification remains challenging due to spatially non-stationary statistics caused by incidence angle effects, seasonal transitions, and strong within-class variability. These factors complicate feature extraction and limit the robustness and transferability of conventional deep learning models. This thesis investigates feature representation learning for sea ice classification in SAR imagery through both supervised and self-supervised paradigms. The first contribution introduces a supervised semantic segmentation framework that integrates convolutional neural networks (CNNs), transformers, and unsupervised region segmentation. The proposed Irregular Tokens on Transformers (ITT) architecture forms multi-scale, homogeneous tokens using Iterative Region Growing on Semantics (IRGS) and applies self-attention to capture long-range spatial dependencies. A multi-task training scheme combines pixel-level and region-level loss functions, encouraging region-consistent feature representations while preserving fine-grained boundaries. Experiments on multi-season RADARSAT-2 scenes demonstrate improved overall accuracy, sharper boundary delineation, and reduced predictive uncertainty compared to a CNN baseline. An expert audit conducted by the Canadian Ice Service further supports the operational relevance and stability of the approach across freeze-up and melt conditions. While supervised learning delivers strong performance when annotations are available, SAR labeling remains costly and domain specific. The second contribution explores self-supervised pre-training toward a SAR foundation model for sea ice classification. By leveraging masked representation learning and multi-task objectives, the proposed framework learns transferable representations from unlabeled SAR imagery. The study evaluates whether large-scale pre-training alone is sufficient to address domain shifts across sensors and seasons, or whether task-specific adaptations remain necessary. Results show that self-supervised pre-training substantially improves downstream performance and generalization, but optimal accuracy is achieved when combined with structured fine-tuning aligned with sea ice semantics. Overall, this thesis demonstrates that robust sea ice classification fundamentally depends on how feature representations are learned, and provides principled strategies for improving scalability, generalization, and operational viability in Arctic SAR applications.
Leveraging Interactive Human–AI Collaboration Methods to Enhance Key Stages of Programming Workflows
(University of Waterloo, 2026-05-06) Liu, Xuye
Beyond writing code, programmers routinely move through several complementary tasks as they develop, refine, and share their work. These workflows typically involve recurring stages: understanding and documenting code, checking correctness and debugging, improving efficiency and scalability, and sharing results with others. Each stage has its own challenges: documentation often becomes outdated or inconsistent with evolving code, debugging can be time-consuming and opaque, performance improvements require balancing competing goals (e.g., speed, memory, and clarity), and communicating results usually demands extra manual effort. This thesis investigates how human–AI collaboration can support programmers across four key stages of the workflow. To address these challenges, I begin by studying the needs and practices of programmers to understand where current tools fall short. Based on these insights, I design interactive systems that integrate with common tools such as computational notebooks and IDEs and operate on invariant components (code cells, execution outputs, text) so results remain compatible with common practices. Across the four stages, these systems provide context-aware code understanding across multiple cells, purpose-driven documentation from code and its execution results for different communicative purposes, presentation slides from code and results, and real-time, multi-dimensional code evaluation and optimization support during development, with authors remaining in control to inspect, edit, and refine outputs throughout. I conduct user studies and case studies to evaluate system usability and to assess how these approaches improve programmers’ productivity, confidence, and ability to share their work.
Habitat Restoration Strategies for Eastern Meadowlark (Sturnella magna, L.) in Ontario
(University of Waterloo, 2026-05-06) Atherton, Claire
Eastern Meadowlark (Sturnella magna, L.) is an at-risk grassland bird in Ontario. S. magna is declining in part from breeding habitat loss and quality decline. Habitat restoration has been proposed as a recovery measure. Information on S. magna’s habitat preferences and current S. magna restoration initiatives are lacking in Ontario. I studied microhabitat characteristics within restored tallgrass prairie sites in Norfolk County, Ontario. No S. magna were observed on the study sites. I compared microhabitat characteristics between potential nest attempt periods, between sites, and to time since disturbance. Visual obstruction was the only characteristic that differed between nest attempts (p < 0.05). All microhabitat characteristics differed between sites (p < 0.05). All characteristics except woody vegetation cover (dCor = -0.00038, p = 0.52) showed a correlation with time since disturbance. The levels of significance for all tests were determined to be artefacts of the small sample size and do not necessarily reflect true trends. Comparisons to the literature suggest that percent grass cover may have been too low and percent total cover too high to support S. magna, but results differed and were too sparse to make meaningful comparisons. Likely not enough time has passed since restoration for the sites to become suitable for S. magna. I distributed an online questionnaire to 334 people knowledgeable of S. magna, tallgrass prairies, and/or grassland birds about past, current, and future restoration strategies in Ontario. Thirty-five responses were received. Projects have occurred across southern Ontario with clusters near Windsor and in Northumberland County.Delayed hay harvesting was the most common management strategy in restored areas. About half of respondents indicated that post-restoration monitoring occurs at least some of thetime. Sixty-three percent of respondentsindicatedthat projects used interventions.Most respondents indicated that projects lacked in sufficiency and effectiveness. Limiting factors included finances and maintenance, and strengths included having a broad focus, planning, and monitoring. Key targets for future projects were southern and eastern Ontario. Key targets for future research were a better understanding of S. magna’s habitat needs and lifecycle, responses to restoration, and use of anthropogenic grasslands. This thesis provides an overview of the state ofS. magnarestoration in Ontario. It provides a roadmap for restoration ecologists and conservation biologists to use when managing habitat for grassland birds in Ontario.
Surface Wave Propagation using Ray Optics with Applications to Hamilton Harbour
(University of Waterloo, 2026-05-05) Bhavsar, Khush
Surface gravity waves are a commonly observed phenomenon in closed lakes. They are primarily generated by winds, but may also be generated by wakes of vessels in the water or tidal forces. These waves are known to undergo refraction and changes in energy (and therefore, amplitude and speed) as they propagate over variable depths in a closed lake. In this thesis, we use the linearized ray optics equations to study the propagation of surface waves in closed lakes with variable bathymetry. We assume that the fluid is inviscid, irrotational and incompressible. We further assume that the wavelength of these waves is much smaller than the length scales over which bathymetry (depth) varies – in other words, we assume the waves propagate in a slowly varying environment. We perform a series of numerical simulations of surface wave propagation with various initial conditions and bathymetries to validate the model, as well as gain insights on the effects of roughness of the bathymetry in diverting the expected trajectories of these waves. Finally, we present a case study on Hamilton Harbour. This watershed has been under scrutiny for several years due to rising eutrophication levels affecting the dissolved oxygen levels in the basin. We apply the numerical model to the bathymetry of Hamilton Harbour to locate hotspots of wave accumulation in the lake, which may provide inference of regions in the lake where we expect sediment resuspension which is one of the primary factors of internal loading of phosphorus in lakes.
Facilitating Game Development From Requirements to Code with LLMs
(University of Waterloo, 2026-05-05) El Shatshat, Ahmed
Large Language Models (LLMs) are seeing further integration into the software development process, in part due to their strength as code-drivers. In defiance of prompt engineering, I put forth Software Requirements Specification (SRS) as the only necessary input to such systems. An extension of Bingyang Wei’s work on a progressive prompting method to develop code, this thesis explores the capacity of Wei’s Progressive Prompting Method (WPPM) to facilitate game development, using a Tailored Large-Language Model (TLLM). I investigate the following four research questions: 1. Does the WPPM facilitate game development? 2. What strengths and weaknesses emerge in the use of the WPPM to develop a game app? 3. What impacts do the results of such an exploration have on the software development process? 4. Are requirements all you need to persuade the TLLM to generate executable code that fulfills those requirements? Through case studies exploring the main facets of game development, insights are extracted demonstrating that game development under such conditions is possible, and deserves further analysis against traditional development processes. This thesis highlights the strengths of LLMs for software development, and addresses how oversight by a domain expert can mitigate the associated weaknesses. This thesis also serves to combat dominant narratives over-estimating the capabilities of LLMs, which seek to push such systems as a silver bullet for all software problems. Further research in accurately assessing the capacity of the technology is suggested, highlighting the importance of a cost analysis against the traditional manual development process.
Overcoming Critical Challenges Hindering Resistance Spot Welding of Dissimilar Advanced High Strength Steel Joints: LME Mitigation and Weld Class Prediction
(University of Waterloo, 2026-05-04) Nooranfar, Melika
Reducing carbon dioxide emissions from the transportation sector has driven demand for lighter vehicles. Advanced high-strength steels (AHSS) enable the use of thinner gauges without compromising crashworthiness due to ability to absorb high fracture energy. Because these materials are exposed while in-service AHSS are typically zinc-coated for corrosion protection. However, excellent mechanical strength is insufficient for these materials to be used for automotive application, they must also be capable of being welded into the automotive structure. Resistance spot welding remains the dominant joining method in automotive body-in-white production, yet two challenges affect weld quality in dissimilar stack-ups: liquid metal embrittlement (LME) cracking and the absence of reliable offline quality prediction. Most existing studies have focused on similar stack-ups, leaving dissimilar joints inadequately addressed. This research examines both challenges using dissimilar configurations representative of industrial practice. The first part investigates LME mitigation in two-sheet joints of zinc-coated 3G-980 AHSS and interstitial-free steel. A short high-current pre-pulse (16 kA, 20 ms) reduced the crack index from 0.56 to 0.14, a 75% reduction. Cross-sectional analysis revealed that the pre-pulse shifted the nugget toward the IF sheet, increasing the distance between the susceptible 3G-980 surface and the fusion boundary. This geometric shift reduced the overlap between liquid zinc and tensile stresses, suppressing crack formation. Contrary to welding made in similar material joint configurations where high-current pre-pulses intensified cracking, the same approach effectively mitigates LME in dissimilar configurations. The second part develops a machine learning framework for weld quality classification in three-sheet dissimilar AHSS stack-ups. Each weld was classified as acceptable (Ok), No weld, or Expulsion based on online assessments. Random Forest and XGBoost classifiers were trained on a 137-sample dataset, with XGBoost achieving 89.3% accuracy and superior performance near class boundaries. The trained models enabled identification of no weld regions and provided a basis for adaptive parameter selection. Both LME severity and weld class are critical indicators of joint integrity yet have rarely been addressed together for dissimilar coated AHSS. This thesis provides an experimentally grounded vii framework linking welding parameters to quality outcomes, offering practical pathways for process optimization in automotive resistance spot welding.
Grinds and Slides: Skateboarding as an Architectural Pedagogy
(University of Waterloo, 2026-05-04) Neal, Janson
This thesis examines the intersection of skateboarding and architecture, proposing that skateboarding is, in effect, a spatial and architectural pedagogy. This work aims to prove that through acts of movement, seeing, and reappropriation, skateboarders learn from and teach through their engagement with the built environment. The act of skateboarding reveals how materials, spatial conditions, and social interactions shape the way architecture is experienced and understood. Skateboarding turns the city into both a classroom and a stage, revealing the architectural potential beyond its anticipated program. The foundation of my research begins with my own lived experience as a skateboarder and a student of architecture. Drawing from both experiences I intend to prove this thesis’ argument that skateboarding is an architectural pedagogy. The research centers around filtering through and documenting architecturally interesting and significant skatespots—the informal sites of skateboarding—presented in skate videos and magazines. From this archiving and analysis of skate media, spots were selected and catalogued for analysis and further investigation as case studies. These spot investigations and documentations include actively skating them, drawing, photography, measuring, on site conversations, and observations. Skateboarders have a unique lived experience and perspective that offers insight into the stuff, people and place of architecture. Architecture is made up of stuff. Stuff supports the spatial and material dimension of skateboarding. It is the architectural elements, the surfaces, textures, and forms that define space, inform use and how it feels to move through space. In this thesis stuff falls into three conditions: edges, surfaces, and voids, and from there investigated and defined spot typologies. It is clear that skateboarding does foster an understanding of form and architecture. Skateboarding is so invested in the stuff of architecture that it has even developed its own architectural lexicon that is unversally shared throughout skateboarding and other peripheral action sports. Architectural elements like curbs, rails, banks, and ledges become moments of exploration and sites of performance. Skateboarding transforms these everyday materials and assemblies into an design knowledge, demonstrating how physical conditions teach through active engagement. The skateboarder is not only a user engaged in convetional understanding of stuff, but also an active and subversive participant and critic of said stuff. The investigation of these various uses and engagements falls within the category of people. Through exploring the skateboarder’s lived experience of spot-finding, modification, and resistance, we understand that skaters engage with the city on their own terms. They reinterpret public space, ownership, and play—sometimes being perceived as vandals and misfits—which often results in adversity and resistance. Skateboarding challenges conventional boundaries and expectations between occupant and designer. Skateboarding’s spatial participation is proof of an understanding and appreciation of architecture and form; additionally, this participation forces others to see space from a new perspective to combat the act. Skateboarding teaches both skaters and non-skaters about architectural form and the response it ignites. Place, or spot, is the composite of the greater architectural site combining building, landscape, and stuff. I visited various spots and documented skateboarding and its reactive relationship to the architecture of the site. Skateboarders transform ‘ordinary’ places into culturally significant spots, and in turn reveal new appreciation for those spots are already deemed extraordinary architectural sites. A plaza, a set of stairs, or a handrail becomes a landmark beyond design intention because of collective action and memory. Skateboarders know and understand these sites through time spent with them. Places gain communal value through use, history, and documentation. This research demonstrates how architecture establishes meaning not only through form, but through interaction. Interaction, like skateboarding, fosters expertise. Skateboarding teaches a way of reading and engaging with architecture that is physical, intuitive, and critical. It establishes the urban landscape as something dynamic and malleable, shaped by movement, touch, and time. Skateboarders preserve, reimagine, and archive architectural space, often extending its cultural and material lifespan through stewardship, occupation, and documentation. These actions demonstrate that architecture is not static, but alive through those who move within it. In this way, skateboarding becomes more than recreation, sport or art; it becomes a form of architectural thinking and learning. It fosters knowledge through experience, collaboration, and care. It shows that the city can be both teacher and stage, that architecture is not only designed but discovered. Skateboarding, in its everyday practice, becomes architecture’s most unorthodox but adventurous pedagogy.
Synthesis of Ta-doped Li7La3Zr2O12 for application in solid-state electrolyte
(University of Waterloo, 2026-04-30) Yan, Xinmei
Solid-state batteries have emerged as a major focus in rechargeable battery research. Among them, cubic-phase of lithium lanthanum zirconium oxide (LLZO) demonstrates excellent room-temperature ionic conductivity, low activation energy, and high thermal stability against lithium metal. Conventional LLZO synthesis struggles with particle size control and large-scale uniform production, limiting commercial applications. Thus, developing an efficient synthesis route for high-quality LLZO is critical. In this work, a refined standard operating procedure (SOP) for fabricating dense pellets from powder was established using commercial powder. Systematic optimization of green body properties and sintering yielded ceramics with 95.8% relative density, 0.49 mS cm⁻¹ conductivity at 20 °C and 0.25 eV activation energy (20–40 °C). Furthermore, the study introduces a spray-drying synthesis approach for cubic-phase Ta-doped LLZO powder. Compared to commercial powders, the synthesized LLZTO produced similarly dense pellets (up to 96.4%) with comparable electrochemical performance. The best sample reached an ionic conductivity of 0.36 mS cm⁻¹ at 20 °C and 0.52 mS cm⁻¹ at 40 °C, with a minimum activation energy of 0.23 eV. Preliminary tests integrated synthesized LLZTO into 3D printing inks. After de binding and sintering, phase stability or crystallite size were unaffected, but mechanical fragility prevented reliable electrochemical testing. Overall, this study demonstrates both an effective spray drying route for scalable LLZTO synthesis and the feasibility of fabricating oxide-based solid electrolytes via 3D printing. Further optimization is needed to improve the mechanical strength and reproducibility of printed structures before achieving consistent electrochemical characterization.
Efficient Inference-time Control and Alignment
(University of Waterloo, 2026-04-30) Rashid, Ahmad
Modern foundation models are typically trained in three broad stages. First, large-scale pre-training is performed using self-supervised learning on massive corpora. Second, models are adapted through mid-training using supervised fine-tuning or instruction tuning on labeled datasets. Finally, a post-training stage is often applied using preference data and reinforcement learning in order to align the model and improve its safety, reliability, and usefulness. Although effective, post-training methods can be computationally expensive and inflexible once large models are deployed. This thesis explores an alternative paradigm: enforcing behavioral objectives at inference time rather than modifying model parameters during post-training. In this approach, smaller modular control models are combined with a base model to shape predictions during the decision process. Our aim is to design alignment mechanisms that are both mathematically grounded and empirically strong while remaining computationally efficient and easy to deploy. We apply this perspective of inference-time control to three problems. First, we address reliability in neural classifiers. We introduce PreLoad, an inference-time mechanism that mitigates arbitrarily high confidence on inputs that lie outside the training support while preserving accuracy and training efficiency. Second, we study reward-guided text generation (RGTG) in large language models as a form of inference-time alignment. We show that stable reward-guided decoding requires carefully designed token-level reward models and propose two algorithms, PARGS and FaRMA, that enable effective reward-guided generation. Third, we address the computational cost of RGTG and propose an efficient algorithm that adds only a minor overhead during inference while preserving the performance and benefits of reward-guided decoding. Together, these results demonstrate that inference-time control provides a flexible and computationally efficient framework for shaping the behavior of modern neural systems. By decoupling representation learning from the decision-time objectives, this work introduces new tools for improving the reliability, alignment, and efficiency of large-scale machine learning models without retraining them.
On Induced Saturation in Graphs and Tournaments
(University of Waterloo, 2026-04-30) Fan, Xinyue
Let H be a graph. A graph G is H-induced-saturated if G is H-free — meaning that no induced subgraph of G is isomorphic to H — and adding or removing any edge in G leaves a graph that is no longer H-free. In this thesis, we study the following question: For which graphs H does there exist an H-induced-saturated graph G? A full answer remains out of reach; indeed, it remains open whether H-induced-saturated graphs exist for every even cycle H. This is particularly intriguing because, in contrast, Behrens et al. [1] gave a short proof that H-induced-saturated graphs exist when H is an odd cycle (except for the triangle, which is complete). A “halfway” result toward settling the case of even cycles is due to Tennenhouse [16], who showed that for every even cycle H, there exists a (non-complete) graph G that is H-free such that adding any edge to G creates an induced copy of H. Tennenhouse’s construction is remarkably simple, but it does not satisfy the edge-deletion property. Our first result complements this: We prove that for every even cycle H, there exists a (non-empty) graph G that is H-free such that deleting any edge from G creates an induced copy of H. The construction of such a graph G is rather involved, and yet unfortunately does not satisfy the edge-addition property. We also study our deletion-only relaxation of induced saturation for other choices of H. In particular, we consider the case where H is a tree, and prove that for every non-complete tree H with two leaves at distance at most three, there exists a (non-empty) graph G that is H-free such that deleting any edge of G creates an induced copy of H. In fact, we prove that every non-complete graph H with two leaves at distance at most three has this property. This follows from an even stronger result for graphs with two leaves satisfying certain technical conditions. Finally, we examine the tournament analog of induced saturation: For which tournaments H does there exist a tournament G that is H-free such that flipping the orientation of any arc of G creates a copy of H? The case where H is transitive is particularly interesting, since Ramsey’s theorem implies that only finitely many H-free tournaments exist in the first place. We prove that for every transitive tournament H, if the critical tournament exists for H, then it also exists for the tournament Δ(1, 1, H), obtained from a cyclic triangle by blowing up one vertex into a copy of H.
Sex- and-Gender-Based Analyses of Penicillin Allergy Labels, Outcomes, and Delabeling Interventions
(University of Waterloo, 2026-04-30) Maximos, Mira
Background: Penicillin allergy labels (PALs) affect approximately 10% of the population, yet over 95% of labeled individuals tolerate penicillin following delabeling interventions. For patients who are considered low risk, oral challenge (OC) and direct delabeling (DD) are increasingly favored over penicillin skin testing (PST), although definitions of low risk vary. Sex-based differences in PAL prevalence and clinical characteristics remain poorly defined. Females are more frequently labeled with penicillin allergy and receive antibiotics more often than males, yet sex-based differences in PAL prevalence, delabeling outcomes, and antibiotic utilization practices remain poorly characterized. A clearer understanding of how sex influences PAL reporting, delabeling strategies, and antibiotic selection is needed to optimize allergy evaluation and antimicrobial stewardship. Objectives: This thesis examined sex-based differences in PAL, delabeling strategies, and antibiotic utilization. A systematic review and meta-analysis evaluated effectiveness and safety of DD and OC in low-risk patients and assessed sex and gender differences in reporting and outcomes. A descriptive analysis characterized OC protocols, hypersensitivity reactions, and reported predictors of adverse events. A cross-sectional study assessed associations between sex and PAL in an ambulatory care hospital in Ontario, including differences in β-lactam allergy reporting, reaction severity, and comorbidities. Finally, a cohort study evaluated whether sex modifies the association between PAL and antibiotic prescribing, including antibiotic class selection and use of second-line agents when β-lactams are indicated. Methods: This thesis is based on research utilizing multiple diverse study designs, including a systematic review and meta-analysis, a descriptive epidemiologic analysis, and cross-sectional and cohort studies. A PRISMA-guided quantitative systematic review was conducted through February 2024 to identify studies evaluating direct delabeling (DD) or oral challenge (OC) in low-risk patients compared with no intervention, penicillin skin testing, or alternative strategies. Study quality was independently assessed by two reviewers. Random-effects meta-analyses were performed, with subgroup analyses conducted in the presence of substantial heterogeneity (I² >75%), and qualitative data were synthesized narratively. Data from included OC studies were further analyzed descriptively to characterize challenge protocols, adverse reactions, and reported predictors of hypersensitivity, with reactions classified by timing and pooled adverse event rates estimated using random-effects models. A STROBE-guided cross-sectional study of adults attending an ambulatory urgent medicine clinic in Ontario (2015–2024) examined associations between sex and penicillin allergy labels (PALs) using multivariable logistic regression. A retrospective cohort study of the same population assessed whether sex modified the association between PAL status and antibiotic prescribing, including antibiotic class selection and β-lactam use when indicated, using multivariable logistic regression with interaction terms; Firth’s bias-reduced methods were applied when separation occurred. Results: Across 28 studies included in the systematic review and meta-analysis (2 randomized trials, 26 quasi-experimental), sex was reported in 86%, with females comprising 61% of participants; however, only 18% disaggregated outcomes by sex and no studies reported gender variables. OC was similarly effective to PST in randomized trials (RR 1.04, 95% CI 0.95–1.13), while quasi-experimental studies reported high delabeling rates for OC (~90%). Direct delabeling was possible in approximately 27% of those included with a study arm for DD. A descriptive epidemiologic analysis of 26 OC studies demonstrated a pooled reaction or non-delabeling rate of 4% (95% CI 3–6%), most commonly mild cutaneous reactions, with higher baseline allergy burden and shorter intervals since index reaction being identified as potential risk factors. In a cross-sectional study of 29,645 ambulatory care patients in Ontario, 9.4% had a penicillin allergy label (PAL), most of which were low risk; females were significantly more likely to have a PAL than males, report multiple medication allergies, and demonstrate sex-specific associations between PAL and comorbidities. In multivariable analysis, female sex, atopic disease, older age, and number of other medication allergies were independently associated with PAL. In the cohort study, PAL was independently associated with increased antibiotic use, while female sex was associated with lower odds of antibiotic prescribing. Effect modification by sex was not detected between PAL and antibiotic use, class selection, or guideline-recommended therapy. Conclusion: PALs remain common and are disproportionately reported among females, despite high tolerability of penicillin following evaluation. Low-risk delabeling strategies, particularly OC, are safe and effective, yet sex- and gender-disaggregated outcomes are infrequently reported limiting understanding of clinical implications. Although female sex was independently associated with PAL and distinct comorbidity patterns, sex did not modify the relationship between PALs and antibiotic utilization. These findings highlight persistent gaps in sex- and gender-sensitive evidence across the management of patients presenting with infections that have a PAL.
Use of Steel Fibres in Bridge Decks to Improve Serviceability and Reduce Top Mat Reinforcement Requirements
(University of Waterloo, 2026-04-30) Rezaee, Bibi Saida
This study examined a practical strategy to enhance the long-term performance of bridge deck slabs, which are highly susceptible to deterioration due to corrosion of conventional steel reinforcement. While glass fibre reinforced polymer (GFRP) bars offer corrosion resistance, their low stiffness often necessitates increased reinforcement ratios to meet serviceability requirements, diminishing their economic and practical benefits. To address this limitation, the study investigated the use of steel fibre reinforced concrete (SFRC) with steel macrofibres to improve service performance and reduce top mat reinforcement demands. The research program integrated concrete mixture development, material characterization, and large-scale structural testing. Practical SFRC mixtures were developed to evaluate material properties including workability, compressive strength and direct tensile response to support mixture selection for structural testing. Six large-scale one-way bridge deck slab strip specimens were tested to failure, simulating deck overhang behaviour. The test variables included GFRP reinforcement ratios of 0.6% and 0.8% and steel fibre volume fractions of zero, 0.5%, and 1.0%. A conventionally steel reinforced slab without fibres served as a control. The results demonstrated that the incorporation of steel fibres significantly improved crack control, stiffness, and flexural capacity in GFRP reinforced slabs. Fibre reinforced specimens exhibited service and strength performance comparable to or exceeding that of the steel-reinforced control slab, with improvements increasing with fibre dosage. Notably, comparable serviceability was achieved even with reduced flexural reinforcement when steel fibres were present. Collectively, the findings indicated that SFRC can effectively mitigate the serviceability limitations of GFRP reinforcement enabling more durable, efficient, and lower maintenance bridge deck construction.
Ahsan Hdeyeh 3ana
(University of Waterloo, 2026-04-30) Jabbour, Sandra
Ahsan Hdeyeh 3ana consists of a series of large-scale India ink paintings on fabric, that stem from my experience as a second-generation Lebanese-Syrian woman born in Canada. This body of work references my familial archive of VHS home videos from the late 90s and early 2000s, encompassing my childhood in Canada and my parent’s life in Syria and Lebanon, to depict themes of cultural in-betweenness, family dynamics, memory, and multilingualism. Notably, this work centers on my childhood as it was recorded on these VHS tapes which were later sent to my family members in the Middle East so that they could watch my brother and I grow up despite the geographical distance. Even though I have not met many of them face-to-face, the exchange of these video tapes fostered a close family relationship between myself and my relatives. As VHS tapes deteriorate overtime, my paintings capture some of the memories contained in this forgotten media, while also allowing me to recontextualize imagery from the past and the present, reflecting on my diasporic connection to my Syrian-Lebanese identity.
The effect of exotic species on native species reintroductions: Ontario's lake trout reintroductions
(University of Waterloo, 2026-04-30) Therrien, Christian
Reintroduction programs are important tools for reversing extirpations of fishes in freshwater environments, but only 25-50% of reintroduction programs are successful. Exotic species are present in many habitats that are targeted for restoration, and exotic species can negatively affect reintroduced species through predation, competition, and changes in the quantity and/or quality of available prey. Thiamine (vitamin B1) is an important nutrient in the diet of fishes. There is growing concern that consumption of thiaminase, an enzyme that degrades thiamine and is found in the exotic prey fish rainbow smelt (Osmerus mordax), may be impacting reintroductions of lake trout (Salvelinus namaycush) in lakes where they are present. Ongoing programs to reintroduce lake trout in Ontario, specifically in the Sudbury Basin and Lake Ontario, provide an opportunity to study how the outcome of reintroduction efforts is influenced by (1) the presence of exotic rainbow smelt; and (2) identity of source population (with specific focus on previous exposure to exotic prey species). I used a multi-lake study to determine if presence of exotic rainbow smelt resulted in decreased tissue thiamine concentrations in lake trout and compared fish body condition and growth between lakes that do and do not contain rainbow smelt. I found that while muscle thiamine concentrations of lake trout did not differ between lakes with and without rainbow smelt, an instance of thiamine deficiency was observed in a lake that contains rainbow smelt. I also found that body condition was significantly lower in lake trout from lakes with rainbow smelt and the asymptotic length of lake trout populations declined with increasing proportion of smelt in the diet. My results suggest that consumption of exotic rainbow smelt can cause thiamine deficiency, decrease body condition and lower asymptotic length in lake trout, and ultimately may be a factor contributing to the failure of programs to reintroduce lake trout throughout Ontario. Next, I compared the effects of diets designed to mimic the thiaminase activity of exotic prey fishes, including rainbow smelt, on survival and performance-related traits between two hatchery strains (Seneca Lake and Slate Island) of lake trout that differ in historical exposure to diet-derived thiaminase. Results indicated that, regardless of strain, the diet containing thiaminase negatively affected most performance-related traits and while most of the negative effects of the thiaminase diet did not differ between the two strains, an increase in red pigmentation and decrease in survival was observed in Seneca Lake fish that had received the thiaminase diet. By comparing the response of two hatchery strains of lake trout to a diet containing thiaminase, I found evidence that pre-existing adaptations to thiaminase differ among hatchery strains of lake trout. Of the hatchery strains I examined, the Slate Island strain is the best environment match and is likely the most suitable for reintroduction into lakes where exotic prey fishes occur. Lastly, I captured a fish of presumed wild origin from Tyson Lake, which has been subjected to reintroductions of lake trout since the 1970s but previously had no records of natural reproduction. Using a combination of methods, I confirmed the fish was, indeed, of wild origin and represents the first documentation of natural reproduction in Tyson Lake. The fish was assigned to both the Lake Manitou and Iroquois Bay strains, which suggests that these two strains of lake trout may be best suited for reintroduction into lakes in the Sudbury Basin, due to their ancestry match to extirpated populations of lake trout in the area. By incorporating multiple methods, this thesis identifies some of the major factors influencing the success of reintroductions of lake trout and advances our understanding of best practices for species reintroductions.
Process Intensification of Sustainable Production Systems through Integrated Modeling and Optimization
(University of Waterloo, 2026-04-30) Roth, Taylor
This thesis aims to advance the sustainability of emerging resource production processes through the application of process intensification and integrated modeling and optimization techniques. Two process optimization frameworks are developed and tailored for the optimization of sustainable agriculture and aviation fuel production processes, which are applied through case studies. The first study develops an optimization framework to determine optimal operating strategies in monoculture and polyculture hydroponic systems considering uncertainty and disturbances. A key novelty of this work is the development of a polyculture hydroponic model incorporating interspecies nutrient interactions and dynamic environmental factors into the optimization problem, offering insights for system management and sustainability. Mechanistic nutrient uptake and growth models are validated using experimental data to effectively capture system dynamics, and used to improve resource efficiency while accounting for parameter uncertainty and external disturbances. A case study of hydroponic polyculture soybean and tomato plants demonstrates the benefits of this approach. Results show that hydroponic systems increase yield by over 60% compared to traditional farming. Compared to monoculture hydroponics, polyculture methods reduce nitrogen consumption by 40% and increase annual profit by 3.91% per kilogram of fruit. These findings highlight the importance of nitrogen supply management and demonstrate how computational optimization can advance sustainable agriculture. The second study determines optimal process designs of intensified catalytic distillation (CD) columns for Alcohol-to-Jet (ATJ) sustainable aviation fuel (SAF) production to improve aviation sector sustainability. Sequential CD columns with separate oligomerization and hydrogenation reactions are compared to a fully intensified CD column with simultaneous reactive sections. Although prior studies emphasize the importance of ATJ kinetic modeling, validated models and experimental data remain limited. Accordingly, a first-order kinetic model containing 46 parameters is developed using experimental data and a genetic algorithm to support the SAF CD model. A key contribution is the application of an enhanced parallel hybrid deterministic–stochastic algorithm (eHDSA) for the optimization of SAF CD systems with multiple reactive sections and integer decision variables, including the quantity and location of reactive stages. The eHDSA is modified from prior work to improve performance for complex SAF optimization problems, achieving average total annualized cost (TAC) reductions of 40% compared to a purely stochastic approach. Replacing two sequential CD columns with a single intensified column yields TAC reductions exceeding 86%, with sensitivity analyses indicating strong design robustness. Results demonstrate that CD intensification can reduce capital and energy requirements, improving resource efficiency and environmental sustainability for SAF production within the ATJ pathway.
Understanding Diverse Needs for Justice: The Role of NGOs in Advocating for Victims/Survivors of Wartime Sexual Violence in the Occupied Territories of Ukraine
(University of Waterloo, 2026-04-30) Iovenko, Marianna
Since Russian armed aggression against Ukraine began in 2014, conflict-related sexual violence (CRSV) has been systematically employed against the Ukrainian population, yet the institutional response has remained structurally misaligned with what survivors actually need. This thesis examines how NGO-based service providers and survivor-led networks (SLNs) in Ukraine conceptualize and respond to CRSV survivors’ justice needs, and what their accounts reveal about the failures of the state’s retributive approach. Drawing on ten semi-structured interviews with representatives of Ukrainian NGOs and SLNs, alongside critical discourse analysis of institutional documents, organizational reports, and government forms, the thesis identifies three interconnected findings. First, the bureaucratic architecture through which the Ukrainian state recognizes CRSV survivors functions as a mechanism of institutional betrayal: survivors are required to translate their experiences into administrative categories designed for different forms of harm, and the formal CRSV survivor status adopted in November 2024 has yet to produce any viable pathway to support. Second, Ukrainian civil society organizations have become the primary providers of care in the space the state has failed to fill, but their donor-dependent, fragmented structure cannot substitute for sustained state provision. The emergence of SLNs represents a qualitative shift in this fragmented landscape of care, as survivors move from beneficiaries to rights-holders demanding meaningful participation in policymaking. Third, survivors’ self-defined understandings of justice diverge significantly from the retributive model the state prioritizes: rather than punishment as an end in itself, survivors seek acknowledgment, transformation from passive victim to active agent, and holistic support that addresses present material and social needs. Together, these findings advance a survivor-defined model of justice that reframes the demand for state accountability not around prosecution outcomes but around recognition and reintegration on survivors’ own terms. The thesis contributes the first empirically grounded analysis of Ukrainian CRSV survivors’ justice needs developed through a feminist sociolegal framework and interview-based methodology, filling gaps that both domestic criminological scholarship and Western feminist legal critique have left unaddressed.
Weyl's Equidistribution Theorem in function fields and multivariable generalizations
(University of Waterloo, 2026-04-30) Champagne, Jérémy
This thesis is concerned with the problem of finding a satisfactory function field analogue to Weyl's Equidistribution Theorem, a task that was initiated by Carlitz in 1952. More specifically, we are looking at the equidistribution of polynomial values $f(x)$ as $x$ runs over the ring $\mathbb{F}_q[T]$, where $f(X)$ is a polynomial with coefficients taken from $\mathbb{F}_q\big((T^{-1})\big)$, the field of formal Laurent series in $T^{-1}$. Classically, results of this type were restricted to the case where the degree of $f$ is less than $p:=\text{char}\,\mathbb{F}_q$, and this \textit{characteristic barrier} was broken about a decade ago by L\^e, Liu and Wooley using new developments surrounding Vinogradov's Mean Value Theorem. Here, we resolve a remaining conjecture made by L\^e, Liu and Wooley, thus establishing the largest class of equidistributed polynomial sequences $f(x)$ determined by irrationality conditions on the coefficients of $f(X)$. We also consider further generalisations of the resulting theorem, which we phrase in terms of additive polynomials related to $f(X).$ In any case, the main difficulty that we encounter arise from some possible interference occurring between terms of the form $\alpha X^k$ with those of the form $\beta X^{p^\upsilon k}$ appearing in the expansion of $f(X)$. To avoid problems of this type, we introduce a transformation $f(X)\mapsto f^\tau(X)$ which preserve the size of Weyl sums, and has the property that $f^\tau(X)$ does not involve any terms of the form $\beta X^{pk}$. In a different but related direction, we generalize the method of L\^e, Liu and Wooley for multivariate polynomial sequences $f(x_1,...,x_d)$ where $(x_1,...,x_d)$ run over $\mathbb{F}_q[T]^d$, and we also consider the case where each of $x_1,...,x_d$ is required to be monic. Similarly to the original paper, the method consists in establishing a minor arc estimate for multivariate Weyl sums using the Large Sieve Inequality together with a multivariate version of Vinogradov's Mean Value Theorem in function fields obtained previously by Kuo, Liu and Zhao.
Love is (not) a Woman’s Topic. Images of Femininity in the Context of Romantic Relationships in Works by Contemporary German-speaking Female Authors
(University of Waterloo, 2026-04-30) Owtscharenko, Sophie Theresa
This thesis examines the representation of femininity and romantic love in contemporary German-language literature, focusing on three works: Miroloi by Karen Köhler, Hey guten Morgen, wie geht es dir? by Martina Hefter, and Die schönste Version by Ruth-Maria Thomas. It analyzes how romantic relationships shape female identities and how these representations are reflected, questioned, and reworked in the selected literary texts. The study is based on the assumption that romantic love functions as a central cultural narrative that influences female life models and contributes to the stabilization of social norms. The thesis shows that all three works engage critically with established models of femininity and romantic love. While the texts differ in tone and structure, they each illustrate how female identities are shaped in relation to romantic relationships and how these frameworks can be challenged or transformed. Overall, the study demonstrates that contemporary German-language literature contributes to an ongoing discussion about femininity, love, and social ex-pectations.

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