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    Lifecycle Management and Technical Feasibility of Hydrogen Pipeline Infrastructure for Canada’s Clean Energy Transition
    (University of Waterloo, 2026-08-28) Khaing, Myo Myo
    This thesis explores the lifecycle management and technical viability of retrofitting existing natural gas pipeline infrastructure for transport in the hydrogen context of Canada’s clean energy transition. Hydrogen is widely recognized as a critical enabler in the pursuit of a net-zero emissions economy, and yet the viability of retrofitting existing pipeline infrastructure for hydrogen service remains uncertain in the face of challenges such as hydrogen embrittlement, material degradation, and a lack of standardized retrofit methodologies. To address these challenges, this study develops an integrated framework combining lifecycle management principles with Multiphysics numerical modeling. A three-dimensional finite element model is established in COMSOL Multiphysics to simulate the behavior of a buried steel pipeline under mechanical, thermal, and hydraulic loading conditions representative of Canadian environments. The modeling approach progresses from baseline geostatic conditions to fully coupled hydro-thermo-mechanical (HTM) analysis, enabling systematic evaluation of stress distribution, deformation, and environmental interaction. The results demonstrate that internal pressure is the dominant factor governing pipeline stress, with maximum von Mises stress reaching approximately 192- 197 MPa under operating conditions, remaining within acceptable limits for X52 steel pipelines. Von Mises equivalent stress is adopted as the primary structural stress indicator because it represents the combined multiaxial stress state and enables assessment of yielding in the steel pipeline, while hoop stress is used separately to evaluate the circumferential response to internal pressure. In contrast, external surcharge loading primarily influences pipe deformation and ground settlement, with displacement increasing to approximately 6-8 mm and surface settlement exceeding 10 mm under higher loading conditions. Thermal effects are found to be negligible under near-ambient steady-state conditions, while groundwater interaction contributes to increased deformation through reductions in effective soil stiffness, without significantly altering peak stress levels. The study further validates numerical results using classical analytical solutions. Management and numerical stress analysis offer a useful framework for assessing retrofit viability. In conclusion, the research makes a specific contribution to the body of knowledge on the hydrogen pipeline retrofitting framework specific to Canada and demonstrates the technical feasibility of existing buried natural gas pipelines for hydrogen transport under specified operating and environmental conditions.
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    A Multi-Scalar Framework for Understanding Evictions: Racialization, Resistance, and Housing Justice in Toronto, Canada
    (University of Waterloo, 2026-08-28) Bonnell, Kevin
    Eviction is often framed in public discourse as the result of individual behaviour or economic hardship, particularly a tenant’s inability to pay rent (Desmond, 2016; Woodhall-Melnik et al., 2026). More recent scholarship, however, conceptualizes eviction as a structural outcome produced by housing markets, governance arrangements, and regulatory systems (Mah, 2021; Wachsmuth et al., 2023). This dissertation builds on these structural analyses while questioning a related blind spot: the limited attention paid to planning institutions and their role in shaping eviction dynamics. While this shift toward structural explanations has been important, it often leaves the processes that produce housing loss insufficiently examined. This dissertation examines eviction in Toronto as a coordinated system of governance shaped through tenancy law, municipal planning practice, redevelopment processes, and administrative routines. Evictions are formally carried out through provincial legal mechanisms. However, the institutional conditions that produce housing instability unfold across multiple sites, including planning approvals, enforcement pathways, municipal intake systems, and tribunal procedures. Eviction therefore emerges as a process structured through timing, coordination, and recognition, which determine whether housing instability is interrupted or allowed to intensify. Drawing on institutional ethnography, Critical Race Theory, and racial capitalism, this dissertation traces eviction across interconnected layers. The analysis integrates 24 tenant interviews, 9 interviews with tenant organizers, 6 interviews with urban planners, observations from 8 tenant organization meetings, and 110 observations of Landlord and Tenant Board virtual hearings. This empirical approach enables examination of eviction across systemic conditions, institutional encounters, and tenant experience. The dissertation is organized in seven chapters. Chapters 1 to 3 establish the conceptual, theoretical, and methodological foundation by framing eviction as layered governance, reviewing scholarship on eviction, planning, racialization, and resistance, and outlining the shared empirical design. Chapters 4 to 6 then present three connected manuscripts that examine eviction as administrative governance, situated resistance within institutional constraint, and cumulative harm produced through institutional time. Chapter 7 synthesizes the findings across the manuscripts and develops the dissertation’s contributions to planning, housing justice, and eviction governance. Together, the manuscript chapters move from system to encounter to lived aftermath, allowing the dissertation to trace eviction from its institutional organization, to the relational practices through which tenants and planners navigate it, to the temporal accumulation of harm that follows. The first manuscript examines the administrative organization of eviction. It demonstrates how redevelopment processes, legal notices, and coordination across tribunal, service, and property management systems produce displacement through routine bureaucratic practices. This analysis shows how eviction risk becomes predictable through standardized communication, fragmented accountability, and procedural sequencing. These processes shift interpretive and administrative work onto tenants. The second manuscript examines how tenants and tenant organizers respond to these constraints by building mutual aid infrastructures that stabilize housing. These practices include document preparation, accompaniment, interpretation, and shared navigation of notices, tribunal procedures, municipal referrals, and housing support systems. This manuscript also shows that planners participate in eviction governance through discretionary practices, including referrals, documentation, and file coordination. These actions influence whether tenant-reported instability is recognized and addressed. The third manuscript examines eviction as a temporal process. It shows how delays at the tribunal, slow or stalled administrative action, and the order of procedural steps prolong uncertainty and increase harm. These dynamics place pressure on racialized and immigrant tenants by shifting the burden of coordination, cost, and risk onto households over time. Collectively, these findings demonstrate that eviction is structured through identifiable mechanisms. These mechanisms include administrative timing, fragmented jurisdictional responsibility, and procedural rules that determine when tenant instability becomes actionable. This dissertation contributes to planning scholarship by showing how planning decisions shape eviction processes. Through redevelopment approvals, rental replacement policies, and negotiated tenant compensation requirements, planners influence when redevelopment can proceed and what protections tenants receive when displacement occurs. These conditions include redevelopment sequencing, enforcement pathways, and administrative coordination. They shape whether housing instability is mitigated or allowed to progress. By centring tenant and organizer accounts as analytic entry points into processes, this dissertation shows how housing stability is shaped by the networks of advice, organizing, and informal knowledge that tenants and organizers describe as they navigate eviction. This analysis explains how planning practice shapes eviction governance and identifies ways planning approvals, tenant protection policies, and related administrative processes can better support tenant stability.
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    Preprocessing for Hard Optimization Problems Across Structurally Diverse Models
    (University of Waterloo, 2026-08-28) Jung, Woosuk
    Difficulties in solving large-scale optimization problems often arise from structural pathologies such as ill-conditioning, Hadamard ill-posedness, and degeneracy, particularly due to the failure of constraint qualifications. While standard algorithms often struggle to address these issues, preprocessing based on structural analysis offers an effective strategy for overcoming such challenges. This thesis investigates several preprocessing methods targeting various sources of these difficulties. In Part 1, we study a nonclassical, average condition number of linear systems, the $\omega$-condition number. Our results demonstrate several advantages of the $\omega$-condition number over the classical $\kappa$-condition number. First, $\omega$ provides a more accurate measure of the conditioning of linear systems by more faithfully capturing the effects of perturbations observed in practice. Second, $\omega$ exhibits superior numerical stability compared to $\kappa$. Third, when used in preconditioner design, $\omega$ more effectively promotes eigenvalue clustering, which is crucial for the efficiency of iterative solvers. Finally, the analytical simplicity of $\omega$ enables the derivation of explicit optimality conditions, allowing for closed-form expressions of optimal preconditioners under various frameworks, including low rank updates of the generalized Jacobian for semismooth Newton methods and diagonal or block-diagonal scaling. For diagonal preconditioning, we further include a comparison between two distinct notions of conditioning. In Part II, we first answer in the affirmative a long-standing open question of whether the smooth stress function admits local nonglobal minimizers. This quartic nonconvex objective function arises in the exact recovery of a Euclidean distance matrix (EDM) of a given embedding dimension. By eliminating the Hadamard ill-posedness caused by translation and rotation invariance, we stabilize Newton's method and avoid singular Hessians. We then consider the single-element error correction problem as a case study. We first show that the projection onto the EDM cone fails to recover the correct EDM in this setting. We then introduce divide-and-conquer strategies based on facial reduction. Our approach efficiently recovers the correct EDM with high accuracy, and we further provide criteria characterizing the existence of multiple solutions. In Part III, we relate FR to the analysis of the convergence behaviour of a semismooth Newton method for projection onto a spectrahedron, i.e., the intersection of a linear manifold and the semidefinite cone. In this process, we derive an explicit formula for the projection onto a face of the semidefinite cone obtained via regularization and analyze pathologies that arise in the absence of strict feasibility. We further show that ill-conditioning of the Jacobian near optimality characterizes the degeneracy of the projection point. As an application, we consider a simplified Wasserstein barycenter problem, a well-known NP-hard problem. We compute the Wasserstein barycenter by exploiting the structure of the linear constraints to obtain a facially reduced doubly nonnegative (DNN) relaxation. This reduction provides a natural splitting for applying the symmetric alternating direction method of multipliers (sADMM). The resulting algorithm exploits structure in the subproblems to compute strong upper and lower bounds. In most of the instances, we achieve the small gap between these bounds, which means that the original problem is solved.
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    An exploratory study into the use of an emotionally aware cognitive assistant
    (University of Waterloo, 2014-08-18) Malhorta, Aarti; Yu, Celia; Schroder, Tobias; Hoey, Jesse
    This paper presents the results of a survey of human emotional responses to a set of audio-visual prompts or cues designed for assistive technology applications. Our goal in this paper is exploratory: we wish to understand how audio-visual prompts are understood by people on an emotional spectrum as a first step towards the more challenging task for designing emotionally aligned prompts for persons with cognitive disabilities such as Alzheimer's disease and related dementias (ADRD). Persons with ADRD often need assistance from a care partner to complete activities of daily living such as washing hands, making food, or getting dressed. Artificially intelligent systems have been developed that can assist in such situations by giving automated prompts or cues. Our long term aim is to enhance such systems by delivering automated prompts that are emotionally aligned with individuals in order to help with prompt adherence and with long-term adoption. As a step in this direction, this paper presents a set of prompt videos of a virtual human 'Rachel', wherein she expressively communicates prompts at each step of a simple handwashing task, with various human-like emotions and behaviours. A user study was conducted for 30 such prompt videos with respect to three basic and important dimensions of emotional experience: evaluation, potency, and activity. The results show that, while people generally agree on the evaluation (valence: good/bad) of a prompt, consensus about power and activity is not as socially homogeneous. This paper gives an overview of the hand washing system, and then details the creation process of the virtual human and the results and analysis of the user study.
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    Inferred Author Gender as a Variable Affecting LLM Behaviour
    (University of Waterloo, 2026-08-28) Hiebert, Avery
    The presence of undesirable bias in Large Language Models (LLMs) and other NLP systems has been studied extensively. However, the widespread framing of “bias” as a distinct phenomenon separable from “legitimate” uses of gender has been identified as a weakness of the existing literature, as has a lack of engagement with the meaning and use of “gender” as a category. We investigate the modeling of “author gender” as a source of gender-influenced behaviour in GPT-2, using an exploratory approach based on interpretability techniques rather than the traditional “biased/unbiased” dichotomy. A simple zero-shot prompt reveals that GPT-2 has learned to estimate author gender in some contexts. Attribution experiments reveal stereotypical associations, both stylistic and semantic, that inform the model’s estimation of author gender. Causal intervention experiments using a linear probing classifier suggest that author gender information influences model output, including reflecting stereotypical gender associations. These results have implications for the detection and mitigation of gender bias and the broader understanding of how gender is “used” by LLMs.