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.)

Browse

Now showing 1 - 20 of 17143

Preserving and Generalizing χ-boundedness
(University of Waterloo, 2025-10-27) Chaniotis, Aristotelis
The notion of χ-boundedness, introduced by Gyárfás in the mid-1980s, captures when, for every induced subgraph of a graph, large chromatic number can occur only due to the presence of a sufficiently large complete subgraph. The study of χ-boundedness is a central topic in graph theory. Understanding which hereditary classes of graphs are χ-bounded is of particular importance for advancing our understanding of how restrictions on the induced subgraphs of a graph affect both its global structure and key parameters such as the clique number and the independence number. Which classes of graphs are χ-bounded? A method that has been used to prove that a class C of graphs is χ-bounded proceeds as follows: we prove that C can be obtained by applying operations that preserve χ-boundedness to already χ-bounded classes. This approach gives rise to the following question: which operations preserve χ-boundedness? Given k graphs G₁,…,Gₖ, their intersection is the graph (∩{i∈[k]}V(Gᵢ), ∩{i∈[k]}E(Gᵢ)). Given k graph classes G₁,…,Gₖ, we call the class {G : ∀i∈[k], ∃Gᵢ∈Gᵢ such that G = G₁ ∩ ⋯ ∩ Gₖ} the graph-intersection of G₁,…,Gₖ. In the mid-1980s, in his seminal paper “Problems from the world surrounding perfect graphs”, Gyárfás observed that, due to early results of Asplund and Grünbaum, and Burling, graph-intersection does not preserve χ-boundedness in general, and he raised some questions regarding the interplay between graph-intersection and χ-boundedness. This topic has not received much attention since then. In this thesis, we formalize and explore the connection between the operation of graph-intersection and χ-boundedness. Let r ≥ 2 be an integer. We denote by Kᵣ the complete graph on r vertices. The Kᵣ-free chromatic number of a graph G, denoted by χᵣ(G), is the minimum size of a partition of V(G) into sets each of which induces a Kᵣ-free graph. Generalizing χ-boundedness, we say that a class C of graphs is χᵣ-bounded if there exists a function f:ℕ→ℕ such that for every G∈C and every induced subgraph G′ of G, we have χᵣ(G′) ≤ f(ω(G′)), where ω(G′) denotes the clique number of G′. We study the induced subgraphs of graphs with large Kᵣ-free chromatic number. Finally, we introduce the fractional Kᵣ-free chromatic number, and for every r ≥ 2 we construct K_{r+1}-free intersection graphs of straight-line segments in the plane with arbitrarily large fractional Kᵣ-free chromatic number.
Data-Driven Decision-Making Under Uncertainty: An Empirical Study of U.S. Wildfire Management
(University of Waterloo, 2025-10-24) Garros, Gong
Wildfire management in the United States faces prediction accuracy, cost efficiency, and fiscal sustainability issues. This dissertation integrates three interrelated research topics to develop integrated decision models applicable to each stage of wildfire management. The first study evaluates the role of social media analytics (SMA) and Web 3.0 technologies towards improving wildfire prediction, real-time tracking, and response decisions. The study reviewed current social media analytics tools for crisis response, showing how they support crisis tracking, response timing, and crisis communication. The same functionality can presumably be applied to wildfire management. The second study introduces a temporal gravity model that links population- and location-weighted social media activity to wildfire response costs per acre. The model captures behavioral visibility prior to operational deployment and demonstrates stronger informational value than tweet volume alone. The third study investigates how federal budget changes relate to the accuracy of state preparedness decisions. Higher funding is associated with improved accuracy in the short term, but this association weakens in later budget cycles. The analysis treats federal budgets as exogenous inputs and uses panel methods with robustness checks to evaluate decision dynamics under fixed fiscal constraints. Across all three essays, the dissertation highlights the importance of integrating behavioral data and fiscal signals to better inform wildfire planning. It provides empirical evidence that public attention, budget expectations, and institutional coordination jointly influence the quality of response decisions. These findings suggest that effective wildfire management requires models that account for informational uncertainty, fragmented authority, and the timing structure of operational and fiscal systems. Keywords: Wildfire Management, Decision Science, Behavioral Operations Management, Crisis Informatics, Public Finance, Panel Data Analysis, Gravity Model, Time Series Analysis.
Cybersickness: Linking Postural Control to User Discomfort in a Virtual Roller Coaster
(University of Waterloo, 2025-10-23) Gulifeire, Alimu
Cybersickness (CS) remains a major obstacle to the widespread use of Virtual Reality (VR), with leading explanations emphasizing sensory conflict, sensory reweighting, and postural instability. Prior research has shown that individuals who flexibly reweight visual, vestibular, and body cues report lower CS, particularly in interactive VR tasks where users can move freely. Whether this relationship generalizes to more passive, visually intense VR experiences is less clear. This thesis examined sensory cue reweighting and postural control as predictors of CS during an immersive roller coaster simulation. Nineteen younger adults completed the Oriented Character Recognition Task (OCHART) before and after VR exposure to estimate perceptual upright and quantify cue weightings. During VR exposure, postural movement was recorded using markerless motion capture, and participants reported symptoms using the Fast Motion Sickness (FMS) scale after each trial. Contrary to findings from interactive VR contexts, sensory reweighting was not significantly associated with CS in this passive roller coaster environment. In contrast, measures of postural control, particularly total path length, were robust predictors of sickness severity, with greater displacement linked to higher FMS scores. These findings suggest that in visually dominant VR tasks with limited bodily engagement, postural instability provides a more reliable marker of CS than sensory reweighting. This work clarifies that the predictive value of sensory reweighting is context dependent, emerging more clearly in interactive than passive VR tasks. It further points toward movement-based strategies for mitigating discomfort in VR experiences where movement is restricted but visual conflict is high.
Evaluating a priori and data-driven weighting of the Healthy Eating Food Index-2019 for assessing diet quality and gastrointestinal and aerodigestive cancer risk in Canadian adults
(University of Waterloo, 2025-10-23) Singh, Navreet
Background: Diet is a modifiable exposure implicated in gastrointestinal and aerodigestive cancers. Because foods are consucmed in combination, diet quality indices are used to summarize overall dietary patterns. The Healthy Eating Food Index-2019 (HEFI-2019) measures adherence to Canada’s Food Guide 2019, and its component scores are nearly equally weighted, reflecting the importance of all foods in a healthful dietary pattern. Its discriminatory capacity for measuring diet-disease associations, and the influence of the weighting schema of the index, remains uncertain. Objective: To assess whether associations between diet quality and gastrointestinal and aerodigestive cancer risk differ among adults in Canada based on the a priori Healthy Eating Food Index-2019 (HEFI-2019) versus a novel modified version with components reweighted using a data-driven approach. Methods: A prospective cohort analysis was conducted using the Canadian Community Health Survey 2004 Nutrition (CCHS 2004) linked with the Canadian Cancer Registry (CCR) through 2016. After exclusions, 10,530 adults were included, representing approximately 23.5 million Canadians. Diet was assessed using interviewer-administered 24-hour recalls. HEFI-2019 total scores were computed using standard weights and using data-driven weights derived from ridge-penalized Cox models in 10 iterations of 80/20 training–test splits with cross-validated penalty selection. Weighted Cox proportional hazards models, adjusted for age, sex, education, income, marital status, smoking status, body mass index, and alcohol consumption, estimated associations with incident gastrointestinal and aerodigestive cancers (ICD-9 140–149, 150–159, 160–161). Discrimination was assessed with Harrell’s C-index. Results: The data-driven approach altered component weights substantially (e.g., protein foods increased from 5 to 16.4; vegetables and fruits decreased from 20 to 3.73). No associations with cancer risk were observed for either the a priori (adjusted HR per unit increase 1.01; 95% CI: 0.99, 1.04) or reweighted HEFI-2019 scores (adjusted HR: 1.00; 95% CI: 0.98, 1.02). Model discrimination was similar (Harrell’s C-index: 0.81 [95% CI: 0.77, 0.85] for a priori; 0.87 [95% CI: 0.80, 0.93] for reweighted). Discussion: Neither the a priori nor reweighted HEFI-2019 was associated with gastrointestinal and aerodigestive cancer risk. Data-driven reweighting did not meaningfully improve associations or discriminatory capacity. These findings suggest challenges in using diet quality indices for complex diet-disease relationships and highlight the need for further research on index construction and application in cancer epidemiology.
Multi-Outcome Trajectories in Traumatic Brain Injury
(University of Waterloo, 2025-10-23) Shein, Vladyslav
Traumatic Brain Injury (TBI) presents a global health challenge, affecting millions of individuals annually, resulting in diverse outcome trajectories that complicate patient management. The heterogeneity in TBI outcomes, influenced by varied clinical presentations and injury responses, requires advanced analytical approaches. The analysis of trajectories using single metrics, such as the Glasgow Outcome Scale Extended Global (GOSE), falls short of capturing the multi-faceted nature of TBI progression, often overlooking the complexity of individual patient experiences. This thesis reports on two studies. First, a systematic scoping review was conducted to synthesize the current research on trajectory analysis in TBI, followed by a modeling study. This work identifies 6 distinct multi-outcome trajectories in TBI patients by employing Latent Class Mixed Models (LCMM) and clustering approaches. Utilizing longitudinal data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury study (TRACK-TBI), a prospective multicenter observational cohort study conducted at 18 level 1 trauma centers across the United States, which includes 17 selected outcome measures collected at four time points post-injury, provides a comprehensive understanding of the heterogeneous progression of TBI. By addressing the limitations of single outcome analyses, this research contributes to a better understanding of TBI progression that can lead to the optimization of TBI management and treatment. The future integration of these trajectories will facilitate the development of personalized treatment strategies, ultimately improving patients’ recovery.
Learning-Based Stability Certification and System Identification of Nonlinear Dynamical Systems
(University of Waterloo, 2025-10-23) Zhou, Ruikun
In recent decades, by taking advantage of the abundance of sensory measurements, learning-based methods have been prevalent and shown their effectiveness in tackling challenging or intractable problems for classical approaches in systems and control. For instance, many systems with complex nonlinearities, high-dimensional state spaces, or unknown dynamics cannot be effectively handled by classical mathematical tools, and computing stability certifications for such systems is often intractable. This thesis aims to construct systematic approaches to perform system identification tasks and learning-based Lyapunov functions for nonlinear dynamical systems, with some extensions to optimal control. The first aspect of this thesis is to develop an efficient method based on a special feedforward neural network structure, an extreme learning machine, to compute stability certificates for nonlinear systems by solving linear PDEs when the dynamics are accessible. Differing from the typical neural network-based approaches that require training on high-performance computing platforms, one only needs to solve a convex optimization problem. On top of that, the proposed method can also be used to efficiently solve the notable HJB equation via policy iteration to obtain optimal control policies for nonlinear systems. The second aspect of this research is to tackle these issues for nonlinear systems with (partially) unknown dynamics. We first show that with two feedforward neural networks, the unknown system and a Lyapunov-based stability certificate can be learned simultaneously. With the help of satisfiability modulo theories (SMT) solvers, the resulting Lyapunov function can be formally verified to provide stability certificates for the unknown nonlinear system. Alternatively, in the past two decades, the Koopman operator and its generator have demonstrated advantages in identifying discrete-time systems and continuous-time systems, respectively, requiring significantly less data while achieving better performance than most existing classical methods. For unknown continuous-time dynamical systems, we propose a novel resolvent operator-based learning framework to learn the Koopman generator, which is a linear operator that describes the infinitesimal evolution of the Koopman operator. The learned generator, thereafter, can be used to identify the vector field of the nonlinear systems. Moreover, with the learned high-accuracy Koopman generator, we can also construct a Lyapunov-based stability certificate for the unknown nonlinear system in the same function space. By formulating the linear PDEs as a linear least squares problem, Lyapunov functions can be computed efficiently. The learned Lyapunov functions can be formally verified using an SMT solver and provide less conservative estimates of the region of attraction, compared to existing methods. Taken together, these contributions provide a coherent pathway that begins with model-based stability certification computation and continues to fully data-driven system identification and thereafter computing Lyapunov-based stability certificates.
Polymorphic Type Qualifiers
(University of Waterloo, 2025-10-21) Edward, Lee
Type qualifiers offer a simple yet effective mechanism for extending existing type systems to deal with additional constraints or safety requirements. For example, the const qualifier is a popular mechanism for annotating existing types to signify that the value in question is read-only in addition. A variable of type const int is both an integer and also cannot be written to. While type qualifiers themselves are well-studied, polymorphism over type qualifiers remains an area less well examined. This has led to a number of ill-desired outcomes. For one, many practical systems implementing type qualifiers in their type systems simply ignore their interaction with generic types. Other systems implement polymorphism with seemingly unique and ad-hoc rules for dealing with qualifiers. In this thesis, we show that this does not need to be the case. We start by examining three well-known qualifier systems: systems for tracking immutability, function colour, and captured variables, and show that despite their differences that they share surprising common structure. We then give a design recipe, inspired by that structure, using the mathematical structure of free lattices for modelling polymorphism over type qualifiers, to give a framework for polymorphic type qualifiers. We then show that our design recipe precisely captures this structure by recasting those three existing systems in our framework for qualifier polymorphism by free lattices. Finally, we extend type qualifiers from ranging over lattices to type qualifiers ranging over Boolean algebras, which we then use to extend an existing effect system with effect exclusion to support subeffecting as well via subqualification and subtyping.
An Empirical Study of Privacy Leakage Vulnerability in Third-Party Android Logs Libraries
(University of Waterloo, 2025-10-21) ZHAO, YIXI
Mobile logging libraries are essential tools for debugging and monitoring Android applications, yet their privacy implications remain largely unexplored. This paper presents the first large-scale empirical study of privacy risks in Android logging practices, analyzing 48,702 applications from Google Play to identify sensitive data leakage through third-party logging frameworks. Our findings reveal that while logging library adoption is limited (3.4% of applications), nearly half (49.3%) of logging-enabled applications exhibit privacy leaks, creating significant security vulnerabilities. Three dominant libraries—Timber (35.2%), SLF4J (35.1%), and Firebase (29.4%)—account for 99.7% of all verified privacy leakage instances. We identify distinct logging patterns across frameworks, with SLF4J showing balanced log level distribution, Timber concentrating heavily on DEBUG levels (78.5%), and Firebase dominated by Analytics Events (98.0%). Our analysis reveals that privacy violations predominantly stem from indirect data flows (62.5%) requiring intermediate processing steps, with most leaks occurring through moderate-complexity paths of 2-4 statements. User-info sources dominate privacy leaks (69.7%), while user-input sources represent a substantial portion (30.3%), highlighting GUI components as significant risk vectors. Longitudinal analysis of application updates demonstrates that privacy leaks tend to improve over time, indicating growing developer awareness of privacy concerns, though persistent vulnerabilities underscore the need for systematic privacy protection measures. Our study contributes the largest dataset of third-party logging-based privacy violations to date, a reproducible analysis pipeline for future research, and actionable insights for developers and library maintainers. These findings emphasize the critical need for practitioners to recognize both user information and user input as significant privacy threats when implementing third-party logging frameworks in Android applications.
Healthy living by design : Exploring the blue zones as a framework for a multi-generational housing typology
(University of Waterloo, 2025-10-20) Ali, Syed Bahroz
This thesis begins by examining the pervasive urban sprawl in Toronto, analyzing the profound health impacts associated with suburban living—challenges such as social isolation, poor walkability, and a general decline in well-being. While the city has responded to housing pressures with mid-rise densification, many existing problems persist and are often intensified: smaller living spaces and inadequate community infrastructure continue to undermine both physical and mental health. In response, the research turns to the Blue Zones—regions where people consistently enjoy longer, healthier lives, largely free from the chronic health issues prevalent in suburban and urban environments. By closely investigating the architectural and spatial qualities of these communities, the thesis explores the fundamental role of design and space in fostering well-being. The study identifies key overlaps between the principles found in Blue Zones and the recommendations outlined in age-friendly and World Health Organization guidelines. These shared values inform strategies aimed at addressing the underlying health concerns of both suburban and densified urban contexts. Central to this approach is a re imagining of housing: specifically, promoting multi generational homes and neighborhood designs that support aging in place, encourage social cohesion, and create opportunities for intergenerational connection.This thesis advances alternative models of housing and community development—drawing on co-housing and co-living precedents from Canada and the Nordic countries—that respond more effectively to Toronto’s climate and cultural context. Instead of pursuing density as an end in itself, the proposed designs emphasize creating environments where people of all ages can flourish, maintain strong social connections, and lead healthier, more fulfilling lives.
Structured Wavefunctions for Precision Quantum Metrology
(University of Waterloo, 2025-10-20) Kapahi, Connor
In this thesis, several projects from biomedical optics measurements of the retina to precision gravimetric designs with neutron interferometers are presented, united by the common theme of applied quantum information techniques to develop next-generation precision metrological instruments. In particular, we introduce theoretical tools for analyzing neutron optical experiments and highlight parallels between neutron and light optics. These tools are applied to a new neutron prism design, demonstrating significantly higher transmission than traditional designs. Designs for devices applying these techniques, including a neutron Fresnel prism, spectrum analyzer, and spin collimator, are discussed. Potential advantages in neutron flux and spectrum resolution are quantified for these designs. The isometry between neutron spin and the polarization of light is exploited to validate the neutron spin collimator experimentally. Applications of structured states of light and experiments applying spin-orbit states to create patterns in the human visual system are described. Results demonstrate an increase in the perceived extent of these patterns, from 3° for Haidinger's Brush to 10° for a spin-orbit state. Work demonstrating a new method of generating a lattice of spin-orbit states in light is applied to neutron optics. Throughout the preceding experiments, methods of modeling neutron optics experiments with light and a semi-classical path-integral approximation have been developed. These methods are then applied to design an experiment that measures the gravitational constant using a neutron interferometer. A three-phase grating moiré interferometer (3-PGMI) design is first tested with infrared light. The deflection caused by a wafer sample is measured with the 3-PGMI and found to match direct measurements. The path-integral model is then applied to determine the uncertainty in the gravitational constant that can be achieved with a near-term measurement with a neutron 3-PGMI. An experiment to measure the gravitational constant is described, with an uncertainty budget, resulting in a measurement to 150 ppm. Potential corrections to previous experiments measuring the gravitational constant, due to lunar gravitational forces are quantified. Future applications of the tools and techniques described in this thesis are then discussed.
Advancing Understanding of the Bacteriophage Lambda T4RII Exclusion (REX) Phenotype
(University of Waterloo, 2025-10-20) Alattas, Hibah
The Bacteriophage Lambda (λ) T4rII exclusion (Rex) system is a finely tuned antiviral defense mechanism in Escherichia coli (E. coli) lysogens that prevents the propagation of T4rII mutant bacteriophage. This exclusion phenotype is defined as the inability of T4rII mutant bacteriophage to propagate within λ-lysogenized E. coli cells. This phenomenon is encoded by two genes of λ (rexA and rexB), whose expression is primarily regulated and driven by the λ PM promoter under the regulation of the λ cI repressor gene. The T4rII infection of Rex+ lysogen triggers the onset of the Rex phenotype. It is characterized by a harsh cascade of cellular responses, including rapid membrane depolarization and the induction of a stress environment that mimics the physiology of the stationary phase. In addition, the disruption of the RexA:RexB balance, particularly the overexpression of rexA relative to rexB, can lead to the same manifestations without infection, indicating that the stoichiometry of RexA:RexB is relevant. Rex “activation” results in significant cell death and has been proposed to serve as an altruistic cell death system to protect the species. In contrast, despite some cell killing, infected lysogens do, to an extent, recover from Rex activation. As such, the phenotype may additionally serve as a mutualistic mechanism that protects both the λ prophage and its stability, as well as its host, by limiting superinfection. For a long time, researchers have hypothesized that E. coli host proteins are involved in this pleiotropic phenotype and identifying them has been a key goal in elucidating the Rex mechanism. Notably, Rex activation depends not only on gene expression and the stoichiometry of RexA to RexB but also on an optimal monovalent cationic environment, underscoring the importance of membrane ion channels and transport systems. Identifying all host mutations that attenuate or abrogate Rex will help in understanding the role of individual components, directly or indirectly, in triggering and inducing the cellular (physiological) manifestations of the Rex phenotype. While many E. coli membrane proteins control the passage of solutes and ions through the membranes, mutations in these proteins may disrupt the ionic environment, thereby resulting in the attenuation or abrogation of Rex. This finding was observed and confirmed by the deletion of several outer membrane proteins, including ompW, ompX, ompA, and ompF (Alattas et al., 2020). Beyond these membrane-associated proteins, the ability of additional genetic and regulatory components to modulate and influence Rex and Rex escape to varying degrees was demonstrated, including tolA, mglC, and rpoS (S). Several of the identified genes play a critical role in cellular osmotic balance and are governed by the stationary phase sigma factor (S) or envelope stress sigma factor (E) as part of the stationary phase and/or envelope distress regulons, under the control of many non-coding regulatory small RNAs. The impact of mutations in these regulatory proteins on Rex activity was examined following superinfection by T4 and T4rII, and the role of the S regulatory proteins, including RssB and IraD, in the Rex and Rex escape mechanisms was reported for the first time. However, the mechanism by which this occurs remains unclear. The impact of fluorescence fusions on colony morphology and texture was investigated, showing variations in colony size among fusion sites and Rex types. These experiments suggested that the fusion site and the expression status of the partner significantly affect Rex activity, likely by interfering with proper protein folding, complex formation, or the stoichiometric balance of RexA to RexB. N-terminal fusions severely attenuated Rex activity, while dual N-terminal tagging almost entirely abolished it. In contrast, C-terminal fusions only partially affected Rex activity, with dual C-terminal fusions showing minimal impact on exclusion capability. Together, these findings highlight the Rex system as a multifactorial, tightly regulated antiviral mechanism that integrates gene stoichiometry, membrane composition, sigma factor regulation and its RNA-mediated control. This work adopts a genetic approach to enhance and refine the existing model of Rex-mediated T4rII exclusion, leading to a new model of Rex that offers new insights into its underlying molecular determinants and paves the way for further exploration of bacteriophage-host dynamics, superinfection exclusion strategies, and programmed cell death in prokaryotes. Keyword: Rex exclusion, RexA, RexB, T4rII, T4, Rex phenotype, λ lambda, sigma factors, E. coli, bacteriophage, phage
Eye Movements: Measuring Fatigue and Attention in Natural and Urban Scenes
(University of Waterloo, 2025-10-17) Srikantharajah, Jatheesh
Exposure to nature can improve affective and cognitive states, reducing stress and arousal. Across four experiments, I measured eye movements when viewing natural and urban environments in the laboratory, recording changes in visual exploration and fatigue. My dissertation formally investigates the relationship between affective preference and visual exploration. For the first time, I gathered data from microsaccades to measure changes in fatigue and arousal while people view natural and urban environments. Natural scenes involved longer and more frequent fixations than urban scenes. I measured blink rates and microsaccade slopes as eye movement indicators associated with arousal and fatigue. These measures indicated that viewing natural scenes involved lower arousal than urban scenes. For static natural and urban scenes, preference was associated with increased fixation count. In experiment 2, I found that fractal complexity influences visual exploration and preference. More complex scenes elicited shorter saccades and were more pleasant, especially for urban scenes. In experiment 3, I contrasted different types of natural and urban environments. I showed that historic architecture was preferred to modern architecture, and that it involved lower fatigue and more exploratory eye movements. In experiment 4, I showed that differences in visual exploration and arousal between natural and urban scenes remained significant when using video stimuli, and when depleting attention beforehand using a sustained attention task. As eye-tracking grows in popularity for measuring experiences in architectural and natural environments, these experiments provide a valuable resource for understanding the relationship between eye movements, affective processing, and fatigue.
Fourier Analysis of Local Fell Groups
(University of Waterloo, 2025-10-17) Vujičić, Aleksa
In 1972, Bagget showed that a separable locally compact group G is compact if and only if its dual space G^ is discrete. Curiously however, there are non-discrete groups whose duals are compact, and such a group was identified in the same paper. In a similar vein, one can define the “Fell group”, a semidirect product of the units of the p-adic integers 𝕆ₚ* acting via multiplication on the p-adic numbers ℚₚ, which Baggett shows is a noncompact group whose dual is not countable. This Fell group forms a basis of the novel work presented in this thesis. In Chapters 3 and 4, we look at the more general setting of the p-adic integers and numbers, known respectively as discrete valuation rings (DVRs) and local fields. We compile many known results about these objects, in order to generalise the theory of the Fell group to what we call the “local Fell groups”. While this is primarily background material from a variety of sources, there is additional work required to extend these results so that the theory is coherent and complete. We also briefly study finite-dimensional vector spaces over local fields. In Chapter 5, we analyse the Fourier and Fourier-Stieltjes algebras of these local Fell groups, which are of the form A ⋊ K for A abelian and K compact. These local Fell groups fall into a particular class of groups induced by actions for which the stabilisers are ‘minimal’, and we call such groups “cheap groups”. For groups of this form, we show that B(G) = B∞(G) ⊕ A(K) ∘ qK, where B∞(G) is the Fourier space generated by purely infinite representations. We also show that in group with countable open orbits (such as the local Fell groups) this simplifies further to B(G) = A(G) ⊕ A(K) ∘ qK. In an attempt to generalise this to higher-dimensional analogues, for which the above does not hold true, we examine the structure of B∞(G). In particular, we obtain a result for dimension two in terms of the projective space, and we show that this is in some sense the ‘best’ decomposition that can be made. Finally in Chapter 6, we study the amenability of the central Fourier algebra ZA(G) = A(G) ∩ ZL1(G) for G = 𝕆ₚ ⋊ 𝕆ₚ and its local field equivalents. We show that ZA(G) contains as a quotient the Fourier algebra of a hypergroup, which is induced by action of 𝕆ₚ* ↷ 𝕆ₚ. In general, if H is a hypergroup induced by an action K ↷ A, then there is a corresponding dual hypergroup H^ by the dual action. When this is the case, we show that these satisfy A(H) ≅ L1(H^), mimicking the classical result for groups. We also show that if H^ has orbits which ‘grow sufficiently large’, then via a result of Alaghmandan, the algebra L1(H^) is not amenable. In particular, this shows that ZA(G) is also not amenable, reaffirming a conjecture of Alaghmandan and Spronk.
Reparative Infrastructure: Reimagining Water Kiosks in Ulaanbaatar’s Ger Districts
(University of Waterloo, 2025-10-17) Liu, Yiqing
Over half of Mongolia’s population lives in Ulaanbaatar, with many settling in ger districts on the urban periphery. These areas, where some residents still live in traditional gers on self-claimed plots, resemble other informal settlements lacking basic infrastructure. Following the political reforms of the late twentieth century, many rural migrants relocated here seeking better opportunities, yet their living conditions remain poor. This thesis investigates how architectural interventions can enhance daily life, public space, and a sense of nomadic identity within these rapidly urbanizing areas. Focusing on the water kiosks system, it explores how these kiosks can serve as social and spatial anchors for future development. Based on literature review, secondary data, and remote site analysis, the thesis proposes two architectural upgrades in Bayangol District. The study ultimately frames a community-driven approach for informal settlements that promotes local agency and spatial justice through reparative infrastructure.
Electroretinograms following short-term chromatic light adaptation in high myopes and non-myopes
(University of Waterloo, 2025-10-17) Bidarkar, Ashita
Purpose: Worldwide, myopia cases are on the rise and the need for finding a definitive mechanism by which myopia develops has become more imperative than ever before. Axial elongation in myopic eyes is linked to short wavelength (λ) light-dependent increases in retinal dopamine (DA). DA is associated with enhanced electroretinogram (ERG) amplitudes. This thesis seeks to examine short-term adaptation to short and long λ light at moderate and strong levels. I hypothesize that short λ light exposure differentially affects full-field ERGs (ffERGs) and central ERGs in myopic eyes compared to controls. Methods: In a multi-visit cross-over design, we compared ERGs before and after 20 minutes of full-field adaptation to long (red LED peak λ (λ 627 nm) or short (blue LED peak λ 448 nm) λ light (Espion ColorDome™, Diagnosys LLC). Human participants (ages 18-30) were healthy high myopes (≤-5 diopters (D)) and emmetropes (+1 D to - 0.25 D). Monocular, light-adapted (LA) ffERGs were recorded using skin electrodes and a handheld system that adjusted for pupil diameter in real time (RETeval™). ERG stimuli were LA standard white flash and flicker (85 Td.s), presented at 2 and 28.3 Hz, respectively. The a-wave, b-wave and flicker ERG amplitudes, and implicit times were compared as a function of pre/post adaption (time), adapting stimulus (λ), and refractive error (RE) group using a mixed model ANOVA. Monocular multi-focal ERGs (mfERGs; 61 hexagons) and pattern ERGs (PERGs; 15° field, 15’ reversing checks) were recorded with natural pupils in keeping with ISCEV standards using DTL electrodes. The Espion™ console and amplifier (Diagnosys LLC) was used for both ERG tests. The primary outcome measures analyzed were the amplitudes and implicit times of the mfERG central wavelet, mfERG average of the surrounding rings and the PERG P50 peak and were compared as a function of pre/post adaption (time), adapting stimulus (λ), and RE group using a mixed model ANOVA. Results: There were no significant differences between controls and myopes prior to adaptation (all p≥0.05) for ffERG tests. The luminance of the light had an effect such that changes in b-wave implicit time decreased with adaptation to 300 cd/m² light in controls (blue 30: -0.451 ± 1.28%; blue 300: -2.28 ± 2.56%; p≤0.001, η2G=0.14) but less so in the high myope group (blue 30: +0.05 ± 1.3%; blue 300: -1.26 ± 2.43%; p=0.01, η2G=0.05). Changes in flicker implicit time decreased with the stronger luminance level but were not different between refractive error groups (i.e. controls: blue 30: 0.15 ± 1.0%; blue 300: -1.05 ± 1.61%, myopes: blue 30: +0.44 ± 2.74%; blue 300: -1.1 ± 1.50%, p≤0.001, η2G=0.13). Stronger light conditions caused b-wave amplitudes to become less negative (smaller) (i.e. controls: blue 30: –5.38 ± 15.6%; blue 300: –3.50 ± 17.7%, myopes: blue 30: –10.9 ± 15.4%; blue 300: +0.85 ± 10.9%, p=0.02, η2G=0.05). Similarly, with v flicker amplitudes, they became less negative (smaller) with stronger luminance adaptation (i.e. controls: blue 30: –4.1 ± 13.4%; blue 300: –0.62 ± 17.1%, myopes: blue 30: –9.9 ± 18.3%; blue 300: +4.7 ± 12.0%, p=0.00, η2G=0.07). When comparing between controls and high myopes or between short and long wavelengths, changes in b-wave amplitudes did not differ. There was a significant difference between RE groups for the PERG P50 amplitude prior to adaptation (p=0.03; Cohen’s d=1.06) such that they were significantly smaller in myopes (2.63 ± 1.0 μV) than controls (3.95 ± 1.5 μV). The N95 amplitudes were also smaller (i.e. less negative) in myopes (-4.39 ± 1.82 μV) than controls (-6.58 ± 1.55 μV; p= 0.01; Cohen’s d=-1.3). The mfERGs showed no significant pre-adaptation RE differences (all p≥ 0.05; all η2G≤ 0.07). For the PERG, in both controls and myopes, the change in N95 amplitudes decreased more with long λ light (controls: -16.6 ± 23.4%; myopes: -24.7 ± 43.4%) than short λ light (controls: +10.4 ± 23.5%; myopes: +1.88 ± 26.7%; p≤ 0.001; η2G=0.541). There were no effects of adaptation on the P50 amplitude or implicit time. For mfERG, the change in N1P1 magnitude was not different between controls and myopes and was not different when comparing λs for any of the five rings (p≥ 0.05). Conclusions: There is no evidence that chromatic adaptation has a differential effect on post-adaptation ffERGs in high myopes. Long λ adaptation, especially with stronger luminance, prolongs ERG implicit times, probably reflecting relatively reduced input from the faster long cone system. There is evidence to suggest smaller central retinal responses with the PERG P50 but not with the central wavelet of the mfERG, indicating altered retinal ganglion cell function but not altered central inner retinal function in young adults with myopia. Further studies should focus on confirming whether altered central retinal function persists in adult myopes and whether longer adaptation times would yield a greater RE difference.
IN BETWEEN LAND AND SEA: Adaptive Redevelopment of the Indigenous Fishing Villages at Mumbai’s Coastal Fringes
(University of Waterloo, 2025-10-17) Dasgupta, Ahan
Architecture is often understood through the spaces it produces, but its more significant role lies in framing the relationships between people, economies, and environments. When these relationships are disrupted by ecological change and urban expansion, the focus of architecture shifts from form to the conditions that allow communities to endure. In the city of Mumbai, this shift is most visible along the coastline, where reclamation, large-scale infrastructure, and speculative real estate have steadily eroded ecological systems. Within this changing landscape, the fishing villages of the Koli community, the city's native inhabitants, continue to function as active settlements that support both livelihoods and cultural practices, even as they are reclassified as informal and placed under pressure from redevelopment. This thesis proposes a framework that responds to the challenges faced by the Koli community through an integrated approach. Ecological restoration is established as the foundation, focusing on mangrove regeneration, wetland protection, and the preservation of tidal flows. Economic resilience is addressed through cooperative infrastructure, including fishing hubs, repair yards, and storage facilities, which strengthen small-scale fishing practices. Cultural presence is supported through plazas, markets, and promenades that keep Koli life embedded within the public realm of the city. Through this lens, the thesis reframes the coastline of the Khar-Danda Village as a shared edge where ecological systems, livelihoods, and cultural practices are sustained together.
Analysis of Limitations of AI Tools for Pediatric Speech Language Pathology Documentation and Mitigation Strategies
(University of Waterloo, 2025-10-17) Tuinstra, Tia
Speech Language Pathology (SLP) is a therapy discipline offered by KidsAbility, a pediatric rehabilitation clinic in Southern Ontario. Documentation is a key part of SLP and other therapy practice guidelines and can take up significant portions of a therapist’s time. AI-based clinical documentation aids have been developed to help reduce this burden, and one such tool - MutuoHealth’s AutoScribe - has been piloted by KidsAbility. Though this AI tool has been beneficial to some therapy disciplines, the SLP clinicians face unique challenges when using these tools. The model seemed unable to recognize speech therapy strategies or to parse the play-based script of pediatric appointments. This thesis seeks to explore the issues SLPs encounter with AI documentation tools and propose potential approaches to mitigate these issues. The AI documentation process was divided into the transcription pipeline, where an audio file input produced a corresponding transcript output, and the generation pipeline, where an input transcript produced a draft SOAP note. The SLPs who had participated in the AutoScribe pilot test were interviewed about their experiences with the tool and its integration into their workflows. The issues reported by the therapists were sorted into those more closely related to the transcript and those more closely related to the drafted SOAP note. A set of sample SLP appointments from KidsAbility were gathered from an extended AutoScribe pilot, with 10 selected as examples of appointment data (audio, transcripts, drafted and final SOAP notes) to test the transcription and generation pipelines. An augmented automatic speech recognition (ASR) pipeline based on a Whisper model was used to test improvements to the transcript. However, the generated transcripts were not significantly improved from the pilot test. Instead, ground truth transcriptions were manually created from the audio files to use for testing the generation pipeline. For SOAP note generation, the addition of discipline-specific context tailored to appointment type was tested. This context was curated in collaboration with SLPs from KidsAbility to include SOAP templates, definitions of key concepts, and information about speech data. A Llama 3.3 70B model was used for SOAP note generation with ground truth transcriptions and SLP specific RAG-adjacent information as context. The input context was optimized over several iterations based on clinicians’ evaluations of generated SOAP note quality. KidsAbility’s SLPs had flagged sessions targeting speech practice as having particular difficulties with AutoScribe. The model seemed unable to make inferences about the child’s speech quality from the transcript alone. Methods of quantitatively assessing speech based on session audio were explored as ways to provide additional context on speech quality to the SOAP generation model. A sample appointment was selected for testing, and child speech samples of the targeted sound were sliced from the audio and assigned quality categories. These samples were then compared against correct productions using the cosine distance between their mel-spectrograms. The samples were also passed through a phoneme-based ASR model to get the layer activations. The cosine distances and layer outputs were then tested as predictive measures of articulation accuracy, with layer outputs yielding the best results. The resulting speech accuracy scores were then passed into the generation model as additional context, with the output containing correct statements about the nature of the child’s articulations. Though clinicians’ availability limited the extensiveness of generated SOAP note evaluations, the SOAP notes generated with SLP-specific context showed improvement compared to the basic model generation. The model also tended to repeat information from previous SOAP notes if examples were provided. It was found that quantitative speech analysis does seem possible using phoneme model layer activations and cosine distances between the mel-spectrograms of correct articulations. Based on these findings, further optimizations to the generation pipeline and work on making effective AI tools for KidsAbility’s EY SLPs will continue.
Lavender Shadows: An Analysis of the Role of Lesbian Feminism in the British Columbia Federation of Women
(University of Waterloo, 2025-10-17) VanDerAa, Ann
This thesis examines the Rights of Lesbians Subcommittee (ROLSC) of the British Columbia Federation of Women (BCFW), an umbrella organization that brought together diverse feminist groups from 1974 to the late 1980s. The ROLSC provides a lens through which to analyze the paradox of lesbian feminist politics in Canada: how could a feminist movement claim to fight for all women while continually marginalizing women who loved women? Through archival research at Simon Fraser University, the University of Ottawa, and other collections, this study reconstructs how lesbian feminists negotiated inclusion, contested heteronormativity, and reshaped the Federation from within. This thesis challenges historiographical narratives that portray lesbian feminism as separate from, or oppositional to, the broader women’s movement. Instead, the experience of the ROLSC demonstrates an alternative trajectory of integration, in which lesbian feminists strategically leveraged their position inside the Federation to achieve systemic change. By situating the ROLSC within Canadian feminist and queer historiography, this thesis shows that lesbian feminists did not merely occupy the shadows of the women’s movement. Their activism reconfigured its very terms, ensuring that feminism in Canada could not remain solely about gender but had to grapple with sexuality, heteronormativity, and the politics of self-determination.
Design, Synthesis, and Characterization of Multimetallic Complexes Supported by an Imidazopyrimidine-Based Trinucleating Ligand
(University of Waterloo, 2025-10-17) Woods, Riley
Transition metal catalysis has revolutionized chemical synthesis for decades and has allowed for the development of several Nobel prize-winning chemical reactions and processes. These catalysts, however, usually rely on the use of rare Earth metals such as platinum-group metals, mainly palladium, leading to economic and sustainability concerns. Recent studies on the use of Earth-abundant elements nickel, cobalt, and copper have revealed that these metals have the potential of offering low-cost alternatives to the traditional catalysts. Furthermore, these metals can access many more states, allowing for new and complementary reactivities to be achieved. Whilst transition metal catalysis is a large and impactful field, the majority of known catalysts are monometallic in nature. A compelling yet much underexplored area is the use of multimetallic complexes. Several studies and reviews have highlighted the beneficial effect of having multiple metal centers held in proximity. These sorts of systems often display improved catalytic performances over their monometallic counterparts. Synergy or metal-metal cooperativity between the centers is usually responsible for these observations, sometimes allowing for multielectron processes that are simply not possible with traditional monometallic catalysts. In terms of trimetallics, there is a paucity of ligand systems that can reliably produce a precise and controlled arrangement of the three metal centers in a way that is useful in catalysis. This is due to most relying on flexible organic frameworks tied to a symmetric node, additionally excluding them from heterometallic applications. Herein is reported a new trinucleating ligand framework, bpipp, specifically designed to enforce close proximity among three metal centers upon complexation. Based on the inherently unsymmetric imidazopyridmine backbone, the ligand features a tridentate pincer-like binding pocket with two additional bidentate binding pockets. This approach utilizes scalable synthetic methods to create a rigid ligand scaffold that precisely controls the spatial arrangement of the metals. The versatility of this ligand is demonstrated through the synthesis of several trimetallic complexes of Ni(II), Cu(II), Co(II); fully characterized by NMR spectroscopy, ESI-HRMS, and X ray crystallography. Notably, our ligand design achieves remarkably short metal-metal distances ranging from 3.3–3.5 Å, significantly closer than most reported trimetallic systems. This structural feature establishes an ideal platform for investigating genuine three-metal cooperative effects in catalysis.
PIECE IT TOGETHER : Rebuildable Homes for Post-Disaster Resilience
(University of Waterloo, 2025-10-17) Akhtar, Areeba
In an era marked by intensifying natural disasters, no one is immune to the risks of displacement and loss. Climate change is exacerbating extreme weather events, leading to more frequent and intense disasters that affect millions globally, with an average of 25.3 million displacements per year from sudden-onset disasters alone. While government-led disaster recovery efforts aim to restore stability, they often rely on short-term shelter solutions that leave individuals with little control over their futures. These shelters, intended as temporary, frequently become long-term residences, as seen in Haiti and Florida, where FEMA housing remained in use for over a decade. As the climate crisis increases the frequency of such events, the question is no longer if, but when, and what happens next. This thesis addresses the critical challenge of how to transition from shelter to home. It responds to two core problems: the disposability of temporary housing and the disempowerment of those who live in them. The research proposes self-build, incrementally adaptable housing systems that give displaced individuals agency over their environments. These structures can be assembled in emergency conditions and later deconstructed to support the rebuilding of permanent homes - turning what was once a temporary fix into a meaningful foundation for recovery. By leveraging Design for Disassembly (DfD) principles and flat-pack strategies, the project offers a system that is not only responsive to immediate needs but also materially and socially regenerative. Unlike standard modular pods, which are costly to store or reuse, these homes are designed as kits of parts that evolve with their users. CNC digital fabrication is used not to mass-produce standardized units, but to enable localized, rapidly deployable systems that support self-building and reduce dependency on centralized supply chains. The thesis employs iterative prototyping, drawing on literature review as a theoretical foundation, to develop a timber-based modular housing system suited to North American climates.Applying the design in post disaster scenario of Jasper Wild Fire and Florida Hurricane to evaluate how the prototypes perform under these recovery conditions - assessing adaptability, reusability, and user empowerment across both interim and long-term use phases. This research reclaims post-disaster housing as a space of autonomy, love, and growth - one where people rebuild not just structures, but lives. In doing so, it legitimizes the nonlinear, personal, and often prolonged process of healing after disaster, proposing a housing framework that is adaptable, enduring, and deeply human.

Browse

Recent Submissions