Theses

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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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Systematic Methodology for Enhanced Performance Prediction in Designing Large Active Phased Array Antennas for Satellite Communication
(University of Waterloo, 2025-11-14) Tung, Justin
The deployment of 5th generation (5G) and the development of 6th generation (6G) networks have increased the demand for global connectivity at high data rates. Traditional terrestrial infrastructure, including base stations and optical fiber, faces challenges in remote or sparsely populated regions, such as mountainous terrain and oceans. Satellite communication (SATCOM) provides a complementary solution, enabling direct wireless links between users and satellite constellations, removing the need for implementing optic fiber cables. Low earth orbit (LEO) satellites have been proposed as they reduce latency and power requirements compared to traditional geostationary satellites, but their constant motion necessitates rapid beam tracking. At the same time, Ka-band operation (27.5–31 GHz) offers wide bandwidths for high data rates but requires high-gain antennas to overcome propagation losses. Electronically steerable Phased Array Antennas (PAAs) have emerged as the leading solution to address these requirements by enabling fast beam steering without mechanical components. Achieving the necessary gain, however, demands large arrays, which introduces significant design challenges. This thesis presents a systematic design methodology for large 26.5–40 GHz (Ka)-band active PAAs and their feed networks. The methodology leverages industry-standard eletromagnetic (EM) simulation models to guide the design of antenna elements and feed networks, ensuring wideband and scalability. Using this approach, a 16 × 16 active PAA is designed, integrating 64 beamforming integrated circuits (BFICs). Critical system level considerations, including DC power delivery, digital signal integrity, and thermal management, are then analyzed to ensure reliable operation.
Examining the Effects of Traits on Early-Establishment Tree Communities Under Different Soil Water Conditions
(University of Waterloo, 2025-11-12) Galarneau, Magalie
Studies have demonstrated the existence of a positive relationship between species richness and productivity in forests around the world. This positive relationship is thought to be explained by two mechanisms: complementarity effects and selection effects. Both mechanisms rely on species’ traits, whereby the diversity of traits (under complementarity effects) or the presence of specific trait values (under selection effects) can increase productivity. However, while it has been clearly established that species richness increases productivity, few studies have tested the implicit assumption that traits underpin the established species richness-productivity relationship. To address this gap, this study examined which traits are responsible for the species-productivity relationship in temperate tree communities during the early stages of stand development, and whether they act via complementarity effects or selection effects. In addition, this study aims to determine how the observed relationship and its underlying traits change in environments with different water availabilities by assessing which traits are associated with productivity in each environment. These questions were answered using an experimental plantation of temperate tree communities in the early stages of stand development, in which water exclusion treatments were implemented. Six temperate tree species were planted in this experiment, either in a monoculture or in a three-species mixed community. To separate the effects of species and trait diversity, the mixed tree communities had a fixed species richness but varied in trait diversity. The species compositions of the mixes were selected to create a trait diversity gradient. Leaf area, leaf mass per area, stomatal density, chlorophyll concentration, specific root length, root tissue density, and root diameter were measured in each community. Community productivity was measured both as aboveground biomass and as belowground biomass. The most consistent pattern of selection in the press treatment was for leaf area, as it was under selection in combination with leaf mass per area and with stomatal density. Pairs of traits including specific root length were also under selection in the pulse and the control treatments. Selection for these traits resulted in three to fivefold increases in aboveground biomass. These results demonstrate that selection effects are the driving force of community productivity during stand establishment. Here, selection acted upon traits related to tree architecture, thermoregulation, photosynthetic rate, and water use, which illustrate the mechanisms by which selection effects drive increases in the productivity of early-establishment communities across varying soil water conditions.
Integration of Borehole Geophysical Logging with Hydraulic Tomography Analysis for Improved Groundwater Flow and Transport Predictions
(University of Waterloo, 2025-11-11) Wang, Chenxi
Hydraulic Tomography (HT) has been demonstrated to be a robust approach to characterize the subsurface heterogeneity, which employs the inversion of head data collected from multiple pumping tests to estimate the spatial distribution of hydraulic properties (e.g., hydraulic conductivity (K) and specific storage (Ss)). However, the resolution of K and Ss tomograms is reduced when the number of pumping tests and observation density gradually decrease. Another issue is that HT’s ability to predict solute/heat tracer transport behavior has not been rigorously examined for complex aquifer systems. Previous studies showed that different types of data (e.g., geological, geophysical, and other hydraulic testing data) carrying non-redundant information can be integrated with HT analysis to improve the mapping of K heterogeneity. This thesis evaluates the effectiveness of integrating geophysical logging data with HT analysis for improved imaging of K distributions. Furthermore, a heat tracer test was conducted in a highly heterogeneous glaciofluvial deposit to investigate the feasibility of reproducing the spatial distribution of observed temperature responses based on a heat transport model with HT K estimates. Five sequential studies are documented in this thesis to explore the integration of borehole geophysical logging with HT analysis for improved mapping of K and porosity heterogeneity, which enables enhanced predictions of groundwater flow and solute/heat tracer transport: (1) Study I integrated two conventional geophysical logging surveys, including electrical conductivity (EC) and gamma ray (GR) logging, with HT analysis to yield 2D K fields in a numerical sandbox experiment. A new spatial conditioning term was proposed to better delineate the hydrostratigraphy from geophysical logging data, which was used to derive the initial guess of K fields for geostatistical inverse modelling of HT analysis. The HT K models with comparative initial guesses of K distributions were evaluated based on their predictive capabilities for groundwater flow and solute transport. After demonstrating the effectiveness of integrating geophysical logging with HT analysis for improved K estimation in a numerical sandbox study, the subsequent studies were conducted at the North Campus Research Site (NCRS) underlain by a highly heterogeneous glaciofluvial deposit. (2) Study II conducted nuclear magnetic resonance (NMR) logging at the NCRS. Compared to conventional geophysical logging surveys, NMR logging can directly provide K estimates, as well as total porosity and effective porosity measurements. The petrophysical relationship between NMR signals and K was site-specifically optimized, and the NMR-derived downhole K profiles were compared with a variety of hydraulic measurements to evaluate their accuracy and resolution along boreholes. (3) Study III constructed 3D K fields based on downhole NMR K profiles and evaluated the representativeness of these K models. Various spatial interpolation approaches were employed to generate spatial K patterns. A multi-level heterogeneity characterization approach was proposed to better represent the layered porous medium at the NCRS. The model performance to predict groundwater flow was examined through simulating the observed drawdown responses from multiple pumping tests. (4) Study IV integrated NMR logging with HT analysis for improved characterization of subsurface heterogeneity. To highlight the importance of incorporating high-resolution initial K distributions to reduce the smoothness of K tomograms, a limited HT calibration dataset with fewer pumping tests and decreased observation density was utilized for model calibration. The effectiveness of this integration was evaluated through a comparative case study using varying numbers of head data for calibration and different spatial interpolation techniques for constructing initial NMR K models. (5) Study V conducted a heat tracer test at the NCRS, in which a dense monitoring network was installed to record temperature responses. The ability of various characterization approaches (e.g., HT analysis) to accurately map K heterogeneity was investigated by reproducing the complex spatial distribution of the temperature breakthrough curves (BTCs). Additionally, NMR-derived effective porosity was used to map a heterogeneous porosity field. Lastly, the sensitivities of heat tracer plume migration to flow, transport, and thermal parameters were investigated. The main contributions of these studies are: (1) conventional geophysical logging survey can provide hydrostratigraphic information to improve the resolution and accuracy of HT estimates; (2) NMR logging yields reliable downhole K estimates for interbedded layers of gravel, sand, silt and clay; (3) after spatial interpolation, 3D K models can be constructed based on NMR logging, which offers reasonable drawdown predictions to pumping tests; (4) integrating NMR logging with HT analysis can provide more representative K estimates consistent with the depositional environment, and the integrated models can still yield reliable K estimates at high resolution when only a limited head data is available for calibration; and (5) the complex temperature response from a heat tracer test can be best reproduced using HT analysis and NMR logging to represent the heterogeneous K and effective porosity fields. Based on their robust performance in predicting groundwater flow and solute/heat transport at different scales, this work advocates the joint use of HT analysis and borehole geophysical logging to characterize subsurface heterogeneity.
Unraveling the Influence of Natural Organic Matter on Lead Release in Drinking Water Distribution Systems
(University of Waterloo, 2025-11-10) Mosavari Nezamabad, Nastaran
Lead release in drinking water distribution systems remains a critical public health challenge, governed by chemistry of corrosion scales and their interactions with bulk water chemistry. Parameters such as pH, dissolved inorganic carbon, residual disinfectants, aluminum residuals, and corrosion inhibitors exert direct control over the solubility, transformation, and stability of lead-bearing components. Natural organic matter (NOM)—a heterogeneous assemblage of compounds produced by biological and geochemical processes—further complicates these processes. NOM can enhance metal mobilization through surface complexation, colloid stabilization, and modification of corrosion product surfaces. This thesis investigates the role of NOM on lead in drinking water systems with emphasis on its characterization, its influence on corrosion scales, and its effects on lead release under variable chemical conditions. NOM from Southern Ontario, Canada, riverine and lacustrine sources was analyzed using complementary techniques like liquid chromatography–organic carbon detection (LC-OCD), fluorescence excitation–emission matrix (FEEM) spectroscopy, and solid-state 13C NMR. These methods identified distinct compositional differences between riverine and lacustrine NOM. Such compositional contrasts can be translated into differential affinities for forming complexes with corrosion products and varying propensities to generate mobile colloids. A series of bench-scale galvanic corrosion cells simulating partial lead service line replacement were used to assess the effects of NOM type , NOM concentration, pH, dissolved inorganic carbon (DIC), residual aluminum, and orthophosphate on lead release under chloraminated conditions. Two-level factorial or half-fractional designs were used for experimental design. Statistical analyses, generalized additive mixed models (GAMM) and factorial analysis, were employed to evaluate the influence of studied factors and their combined impacts on lead release. These analyses consistently demonstrated that higher pH and DIC reduced total and dissolved lead release, while NOM enhanced dissolved lead mobilization. While aluminum had minimal impact in NOM-free conditions, its presence under NOM-rich conditions reduced lead concentrations. NOM also diminished the effectiveness of orthophosphate in reducing lead concentration, even under elevated pH. Corrosion scales were analyzed to identify mineral phases and morphologies. Scale analysis confirmed the predominance of smaller hydrocerussite and/or cerussite in the presence of NOM. Collectively, these findings provide mechanistic insight into the interplay between NOM, water chemistry, and corrosion control strategies. This research advances understanding of NOM–metal interactions and supports the development of more resilient strategies for managing lead in drinking water systems.
Organizational support and management of volunteer coaching pathways for girls in community sport
(University of Waterloo, 2025-11-07) Baxter, Haley
Volunteer coaches play a crucial role in teaching skills, guiding athlete development, and leading community sport programs (Cassidy et al., 2023). However, there is a notable underrepresentation of women and girl volunteer coaches in community sport, necessitating further research into their recruitment and support. Currently, little is known about the experiences of girl youth athletes related to coaching pathways and the support available to enter volunteer coaching roles despite this population representing an important pipeline of future sport coaches (LaVoi & Boucher, 2021). This dissertation explores organizational support as it relates to the management of volunteer coaching pathways for girl ice hockey players in community sport. Guided by an interpretivist approach, this dissertation is presented in an integrated article format, comprised of three manuscripts that collectively contribute to the lack of research on women and girls in volunteer sport coaching roles at the community level (Baxter et al., 2021). This qualitative study draws on data collected through semi-structured interviews conducted with nineteen self-identified girl ice hockey players ages 12 to 17 years old and ten leaders of nonprofit community ice hockey organizations located in South-Western Ontario, Canada. Data were collected to maintain the overarching purpose of the dissertation while addressing the separate research objectives of each manuscript. Subsequently, data were analyzed following Braun et al.’s (2021) reflexive thematic analysis techniques and guided by the aims and theoretical assumptions identified in each of the respective manuscripts. Theoretically, this research draws on perceived organizational support (POS) theory (Eisenberger et al., 1986). POS refers to the general belief that organizational members (e.g., employees, volunteers) hold, regarding the extent to which an organization cares about their well-being and values their contributions (Eisenberger et al., 1986). Members with positive assessments of POS tend to have higher rates of retention and commitment to an organization. In addition, the third manuscript (Chapter 4), draws on Ryan and Deci’s (2000) self-determination theory (SDT) to provide an additional analytic lens related to volunteer well-being. SDT suggests that well-being consists of three psychological needs, including the need for autonomy, competence, and relatedness. The purpose of the first manuscript (Chapter 2) was to examine perceived organizational supports for girl volunteer coaches in community sport and identify what support processes are needed to generate pathways and develop girls into sport coaching roles. The findings reveal girls' altruistic coaching intentions, the importance of relatability and communication in coaching pathways, preferences for resource equity, and the availability of coaching pathways. The research highlights girls’ aspiration to give back as future coaches despite limited awareness of coaching certification processes. The purpose of the second manuscript (Chapter 3) was to examine current challenges, strategies, and opportunities amongst club leader’s for the recruitment of girl youth ice hockey coaches in community sport clubs. The findings also reveal the lack of organizational support sport club volunteers felt from provincial and national sport organizations as acknowledged in the challenges they face in relation to the recruitment of girls and women as ice hockey coaches. Challenges include a lack of specific targets and informal strategies related to recruitment of women and girl coaches, club leaders perceived lack of interest in coaching amongst women and girls, and prioritization of elite-level sport by provincial and national sport organizations. Despite these challenges, leaders describe opportunities for engaging girl youth volunteer coaches including through the engagement of alumni networks, encouragement of volunteerism amongst current athletes, and support of the coach certification process for girl coaches. The purpose of the third manuscript (Chapter 4) was to examine how the tenets of well-being as proposed by self-determination theory - autonomy, competence, and relatedness - can enhance our understanding of the organizational supports needed to facilitate girls’ transition from players to volunteer coaches. Findings reveal that girls have positive experiences throughout their playing careers that contribute to their sense of well-being, yet there is limited knowledge of how these experiences can facilitate pathways into coaching despite an expressed interest in pursuing coaching opportunities amongst girls. Together, the three manuscripts that comprise this dissertation offer new insights to help sport governing bodies and clubs consider the importance of club level intervention to promote the recruitment of girl athletes as volunteer coaches who are, according to LaVoi and Boucher (2021), the start of a fruitful “pipeline” of future women and girl coaches. In addition, the use of POS and SDT provides a theoretical understanding of how clubs can create supportive environments to engage girls as volunteer coaches during their playing career and offers an important direction for nonprofit sport organizations seeking to improve capacity, increase the representation of women and girls in coaching and leadership positions, and deliver sustainable, high-quality sport programs in our communities for all participants (Hoye et al., 2019).
Designing for Trust: A Multi-Factor Investigation of Optometrists’ Perspectives on AI-Based Glaucoma Screening Systems
(University of Waterloo, 2025-11-07) Karim, Ali
Although glaucoma screening AI models show strong performance, their integration into clinical practice remains limited. Clinicians often face barriers rooted in technological acceptance, with trust emerging as a key determinant of adoption. Prior research has emphasized explainability, but a broader exploration of factors affecting trust is needed. This study investigates multiple factors shaping trust in AI and translates them into design requirements for next-generation glaucoma screening clinical decision support systems (CDSS). In a previous study, two real-world glaucoma patient cases, each comprising three visits at different times, were presented under both unimodal conditions (fundus images only) and multimodal conditions (fundus images, optical coherence tomography, visual fields, and medical history) through a mock interface simulating an AI-based glaucoma screening support system. During these simulated visits, nineteen licensed optometrists interacted with the system and participated in follow-up interviews, where they were asked whether they trusted the system and to explain their reasoning. The objective of this thesis is to identify the factors influencing optometrists’ trust in an AI-powered glaucoma screening tool and to propose design recommendations that can enhance trust in future iterations. The interview data were analyzed using Braun and Clarke’s thematic analysis approach. The emerging themes indicate that trust in the AI system is shaped by multiple factors: (1) alignment with clinicians’ expectations of AI’s role: flagging tool vs. consultant; (2) completeness of information; (3) communications of performance metrics: accuracy, sensitivity, confidence scores, perceived consistency and perceived quality of training data (4) clinical relevance of outputs (trends, actionable recommendations, differential diagnosis); (5) transparency in risk factor weighting, exclusions, and considered variables; (6) decision alignment between optometrists and the AI, assessed across decision inputs, identified risk factors, their relative importance, recommended actions, and the gradient of concordance in final decisions; (7) optimized the AI for cautious screening to captures all potential cases; (8) interface usability supporting timely decisions; (9) users’ self-perceived expertise, occasionally leading to overreliance; (10) onboarding and training that highlighted the system’s features and limitations; and (11) increasing familiarity over time, which helped calibrate trust. Based on these findings, 17 design principles were proposed to guide the development of the next iteration of a trust-supportive interface for glaucoma screening decision support systems.
Stream periphyton response to phosphorus loading events is constrained by antecedent conditions
(University of Waterloo, 2025-11-06) Schneider, Natalie
Phosphorus (P) loadings to streams often occur in short duration events associated with runoff from human activities. Although it has been shown that stream periphyton can uptake and assimilate event-based P, the role of antecedent P concentrations in modulating P uptake from event-based loadings and resulting effects on periphyton structure and function is not known. To assess effects of antecedent P concentration on stream periphyton response to short-term P loading events, we completed two 26-day artificial stream experiments at the Thames River Experimental Stream Sciences (TRESS) Centre in London, Canada. Experiments consisted of exposing periphyton communities in nine artificial streams to a range of 48-hour P loading event concentrations (15 to 690 μg P/L) under low (10 μg P/L) or high (50 μg P/L) antecedent P concentrations. Periphyton was sampled one day before, one day after and 10 days after P loading events to quantify periphyton structure (ash free dry mass (AFDM), chlorophyll a (chl a), P content) and function (P uptake, benthic metabolism, cellulose decomposition, biomass growth, chl a accumulation). Under low antecedent P conditions one day after the P event, P content and P uptake had a positive linear relationship with event concentration and this was similarly seen in biomass and chl a ten days after the P event. One day after the P event in high antecedent streams, P content and P uptake showed a positive linear response with P event concentration, but this additional P in periphyton did not lead to increases in biomass and chl a. Whereas, a negative linear relationship with event concentration and P uptake was seen ten days after the P event. Measures of periphyton function (benthic metabolism and cellulose decomposition) were unaffected by P event size and regardless of the antecedent condition. These findings suggest that high antecedent P concentrations caused cellular saturation of periphyton limiting the assimilation of P from event-based P loads. Therefore, streams with high antecedent P may deliver reduced water purification benefits with regards to attenuating P transport to downstream ecosystems at risk of eutrophication. Management actions to reduce antecedent P concentrations will be needed to rehabilitate ecosystem service provision in streams chronically enriched in P.
Cross-sectional Analysis of Current Care Assessment Practices in the Retirement Home Sector in Ontario
(University of Waterloo, 2025-11-06) Nasim, Anooshah
As the population of Canada ages, some older adults often have increased multimorbidity, disabilities, and frailty. As a result, they are at an increased risk of hospitalization, accelerated functional decline, and earlier institutionalization. As they face more disability and health challenges, the lack of sufficient primary, community, and home care services to support them leads many to move into retirement homes. Once there, residents continue to experience health challenges, likely as a consequence of ongoing inadequate primary care and insufficient services geared toward their needs. Yet, addressing the unmet needs of retirement home residents at the individual and population levels is made challenging by the lack of standardized information collection. While regulatory agencies stipulate that residents undergo a health assessment, there are no specific requirements as to their nature. A better understanding of their unmet needs can potentially guide better primary care planning and help identify the level of services required to deliver better resident and system outcomes. To begin, current care assessment practices and processes surrounding these assessments must first be characterized and understood before the introduction of a new standardized instrument can be contemplated.
Manifold-Aware Regularization for Self-Supervised Representation Learning
(University of Waterloo, 2025-11-04) Sepanj, Mohammad Hadi
Self-supervised learning (SSL) has emerged as a dominant paradigm for representation learning, yet much of its recent progress has been guided by empirical heuristics rather than unifying theoretical principles. This thesis advances the understanding of SSL by framing representation learning as a problem of geometry preservation on the data manifold, where the objective is to shape embedding spaces that respect intrinsic structure while remaining discriminative for downstream tasks. We develop a suite of methods—ranging from optimal transport–regularized contrastive learning (SinSim) to kernelized variance–invariance–covariance regularization (Kernel VICReg)—that systematically move beyond the Euclidean metric paradigm toward geometry-adaptive distances and statistical dependency measures, such as maximum mean discrepancy (MMD) and Hilbert–Schmidt independence criterion (HSIC). Our contributions span both theory and practice. Theoretically, we unify contrastive and non-contrastive SSL objectives under a manifold-aware regularization framework, revealing deep connections between dependency reduction, spectral geometry, and invariance principles. We also challenge the pervasive assumption that Euclidean distance is the canonical measure for alignment, showing that embedding metrics are themselves learnable design choices whose compatibility with the manifold geometry critically affects representation quality. Practically, we validate our framework across diverse domains—including natural images and structured scientific data—demonstrating improvements in downstream generalization, robustness to distribution shift, and stability under limited augmentations. By integrating geometric priors, kernel methods, and distributional alignment into SSL, this work reframes representation learning as a principled interaction between statistical dependence control and manifold geometry. The thesis concludes by identifying open theoretical questions at the intersection of Riemannian geometry, kernel theory, and self-supervised objectives, outlining a research agenda for the next generation of geometry-aware foundation models.
Towards a Novel Optical Spectroscopy Technique Using Photon Absorption Remote Sensing
(University of Waterloo, 2025-11-04) Dhillon, Jodh
Optical spectroscopy has shown great promise in the field of biomedical research. For example, works employing traditional spectroscopy approaches have demonstrated that analyzing a sample’s optical response to incoming light can effectively differentiate between healthy and diseased tissue. However, these techniques suffer from limitations due to the fact that they typically capture signals from only a single light-matter interaction type, such as absorption, scattering or fluorescence. Therefore, many traditional methods are constrained in terms of the types of samples they can feasibly analyze, as well as, potentially, the depth of their sample characterization, as they do not focus on capturing relevant information from other interaction modalities. This work employs photon absorption remote sensing (PARS) to overcome these limitations. PARS is a novel all-optical imaging technique capable of capturing radiative and non-radiative relaxation processes following electronic photon absorption. This thesis explores the initial development of the first PARS system specifically designed and optimized for optical spectroscopy applications, aimed at studying wavelength-dependent relaxation processes to characterize a wide range of liquid samples. The first step of this work was to build a non-radiative PARS spectroscopy system capable of accurately capturing the thermal and acoustic relaxation processes that arise from different ultra-violet (UV) excitation wavelengths. These signals were processed and used to construct a non-radiative PARS absorption spectrum for each sample of interest. These spectra were benchmarked against the absorption data collected from a NanoDrop spectrophotometer, which served as the ground truth in this work. This study revealed that for certain samples, such as eumelanin, which is highly absorbent to UV light and relaxes almost all absorbed energy non-radiatively, the non-radiative PARS spectroscopy system is capable of generating highly accurate absorption spectra. However, this system did not generate as close to ground truth spectra for samples that do not have as strong UV absorbing tendencies and are not as non-radiative in nature. The second step of this work was to integrate a radiative relaxation arm into the developed non-radiative PARS spectroscopy system. This pathway was configured to collect fluorescence emission spectra, which represent radiative sample relaxation, simultaneously with the collected non-radiative data. Radiative PARS absorption spectra were generated for each sample. In this way, the developed PARS system combines absorption (monitoring both relaxation pathways) and fluorescence emission spectroscopy onto a single bench-top system. The radiative PARS absorption spectra were compared to the ground truth, which revealed that molecules that are highly fluorescent in nature are more appropriately studied through the radiative relaxation arm than the non-radiative pathway. Total absorption spectra, which combine the non-radiative and radiative absorption data, were also generated, and it was determined that the absorption profiles of certain samples, such as NADH, are best studied using this approach. The final step of this work was to use the collected total absorption and fluorescence emission data from the PARS spectroscopy system to identify the composition of different mixtures of craft red and blue ink samples. Traditional linear and generalized bilinear models were employed to perform this unmixing and the results from this study indicate that the combination of the absorption and fluorescence data collected on this system allows for a more accurate identification of a mixture’s components than either data source individually. This suggests that the PARS spectroscopy system provides an increased level of detail in sample characterization compared single-modality spectroscopy systems. Ultimately, this research lays the groundwork for the development of a PARS spectroscopy system capable of being deployed in clinical settings to study samples and help inform diagnoses. This work demonstrates the feasibility of leveraging PARS for optical spectroscopy and presents a system design and framework that can be further iterated upon to enhance performance and enable a robust characterization of relevant and complex biological samples.
Polynomial Controllers for Optimal Trajectory Matching with Stability Guarantees
(University of Waterloo, 2025-11-04) Kitaev, Alexander
We formulate a trajectory matching problem in which a set of reference trajectories for a plant is given, and a control law that causes the plant’s trajectories to be as close as possible to the reference trajectories is desired. These trajectories might be generated by an implicit controller such as a model predictive control (MPC) algorithm or manually chosen by a user. This thesis presents a nonconvex optimization approach for solving the trajectory matching problem that generates explicit polynomial controllers. The value of this approach is that the explicit control laws it generates are simpler to implement, and can be used for stability analysis. Additionally, the method presented in this thesis guarantees local stability of the generated controller by ensuring local contractivity towards the generated trajectories. This thesis presents several theoretical results that justify the method described here. Firstly, a proof that the local contractivity constraints used to ensure local stability can be expressed as a set of matrix inequalities is presented, which turns an infinite set of constraints into a finite one. Secondly, a theorem that describes how symmetries in the trajectory matching problem correspond to symmetries in its solution is presented and proven, which enables a reduction in the control design problem size and resulting solution. Finally, this thesis demonstrates the method it describes on two example problems motivated by real-world applications. The first of these is stabilization and disturbance recovery for a single-machine infinite-bus (SMIB) power system, and the second is a lane change manoeuvre for Dubin’s vehicle, a simple vehicle model. In each case, the reference trajectories are generated by MPC.
Influence of the Coating on the Radiative and Conductive Heat Transfer of 22MnB5 Steel in Hot Stamping
(University of Waterloo, 2025-11-03) Bhattacharya, Ardhendu
In hot stamping of Al-Si coated 22MnB5 steel, the heat transfer coefficient (HTC) during quenching is critical for determining the microstructure and mechanical properties of the formed part. Additionally, the radiative properties elucidate how the surface transforms as the steel is heated before quenching. Knowledge of the surface transformations is paramount for understanding the damage caused by the molten Al-Si coating to ceramic rollers in a production environment. This work investigates the effect of the coating on the HTC during quenching and explores the link between radiative properties and surface state changes, including the melting of the Al-Si coating and oxide layer growth. Experiments were performed using a hydraulic press fitted with cooled dies to study the impact of interfacial pressure, coating weight, and dwell time on the HTC. The HTC increased with interfacial pressure, before saturating between 6 and 10 MPa. Specimens with higher coating weights had lower HTCs, which was corroborated by a higher arithmetic roughness for specimens with higher coating weights. Furnace dwell time did not significantly affect the HTC or the roughness of the specimen. Ex situ reflectance measurements of hot stamped specimens revealed minima and maxima between 200 and 1000 nm, due to thin film interference. Wave optics analysis on the reflectance spectra suggested that the oxide layer grew with dwell time. This was confirmed using high resolution – scanning electron microscopy, wherein the measured oxide layer thicknesses were within 50 nm of the estimated oxide layer thicknesses. Additional samples were heated in a muffle furnace for between three and sixty minutes. Wave optics analysis on the reflectance spectra suggested that the oxide layer grew parabolically, as per Wagner’s law. Microscopy measurements revealed that the interdiffusion layer grew linearly simultaneously with the oxide layer. In situ specular reflectance measurements of specimens during heating were performed using a laser-driven light source. The specular reflectance peaked twice; the first peak was attributed to initial coating liquefaction, and the second peak was attributed to subsequent intermetallic reactions. In situ measurements performed on specimens coated with Thermoboost® and iron nitrate revealed a significantly lower specular reflectance peak and higher heating rates.
Understanding and Advancing Pro-Environmental Behavior in Hospitality: A Systematic Review and Multi-Method Investigation Using the Fogg Behavior Model
(University of Waterloo, 2025-11-03) Darwazeh, Durgham
Pro-environmental behavior (PEB) has recently emerged as a prominent theme in the hospitality literature, with various scholars applying social-behavioral theories to examine the determinants of environmental behaviors. Nevertheless, few studies have applied predictive models of behavioral change to offer new insights on the interaction between internal and external factors in fostering PEB in the workplace. This dissertation addresses this gap by applying and extending the Fogg Behavioral Model (FBM) to introduce new pathways toward PEB, specifically within the hospitality industry. The dissertation is composed of three studies, which are connected and contribute to the development of theoretical and practical knowledge in the field of PEB. The first study offers a systematic review of the literature, which considers the current state of research and identifies common themes. Data for the first paper were collected using three database sources: ProQuest, Scopus, and Web of Science. After screening, 104 peer-reviewed articles were included in the study for thematic analysis. This study aims to examine the progress of the current literature in exploring the concept of PEB by answering three primary questions: 1) How has the definition of PEB evolved? 2) What theories have various authors adopted? and 3) What future research recommendations have been identified in the literature? 104 peer-reviewed articles were analyzed using thematic analysis. The results indicate that PEB definitions have been advanced to distinguish between voluntary and involuntary behaviors for employees and acknowledge the psychological effect of hotel guests on their engagement in environmental practices; traditional theories such as the theory of planned behavior and the social-oriented theories remain dominant; and most studies recommend future research to integrate constructional and psychological factors to expand on current research models. Overall, the review can be a useful tool for future studies to identify a more descriptive definition and theoretical lens. Additionally, the review calls for the use of diverse frameworks to deepen our understanding of how PEB unfolds within hospitality settings. To respond to this call, the second study adopts the FBM as a new behavioral framework to explain how employees’ motivation and ability, along with hotels’ environmental management practices (EMP), interact to influence workplace PEB. The third study extends the FBM by positioning organizational trust (OT) as a contextual-psychological factor that is influenced by behavioral change elements to enhance employees’ engagement in PEB. Thus, it offers a novel perspective on the development of PEB within organizational contexts. Data for the second and third studies were collected through Qualtrics from 337 hotel employees in the United States and Canada. Structural equation modeling—path analysis was used to test the proposed hypotheses in studies 2 and 3. The results indicate that extrinsic and intrinsic motivations, ability, EMP, and OT are key factors for fostering PEB. Firstly, environmental motivation influences PEB directly and through employees’ perceived ability and hotels’ EMP. Secondly, ability mediates the relationship between motivation and hotels’ EMP. Thirdly, EMP mediates the relationship between ability and PEB and has a positive and direct impact on PEB. Last but not least, OT is a full and partial mediator that facilitates the relationship between both ability and hotels’ EMP and PEB. Based on the outcomes, this dissertation sheds light on the important role of motivation as a powerful element in the behavioral change process, driving employees to develop a positive perception of their ability, which subsequently enhances their responsiveness to hotels’ EMP and thereby increases engagement in PEB. Nonetheless, the relationship between motivation and OT turns out to be complex and may require another factor, such as organizational support, to bridge the two constructs. However, OT plays a primary role in workplace behavior, bridging employees’ ability and hotels’ EMP (behavioral triggers) with PEB. Therefore, this dissertation contributes to the advancement of theories by utilizing the Fogg Behavioral Model as an integrative and action-oriented model that defines the interrelationship between behavioral elements in a simple, straightforward context; it reconceptualizes the role of hotels’ EMP as a catalyst that transforms employees’ motivation and ability into PEB; and it extends the FBM by positioning OT as a key component in the behavioral change process that translates employees’ confidence and hotels’ structural environmental management practices into PEB.
Effects of Phospholipase A/Acyltransferase-1 (Plaat1) gene deletion on brain molecular and biochemical measures and memory
(University of Waterloo, 2025-10-30) Cocco, Alex
Phospholipase A1/2 and Acyltransferase-1 (PLAAT1) is a small lipid metabolizing enzyme that possesses transacylase activity and is expressed highly in the rodent heart and brain. Recently, our lab has found that in vitro, PLAAT1 is capable of acylating monolysocardiolipin with an acyl chain donated from phosphatidylcholine acyl donors to produce cardiolipin. Cardiolipin is a glycerophospholipid that is essentially exclusive to the mitochondria and is vital for trans-membrane protein stability, inner mitochondrial membrane structure, apoptosis, and more. The de novo synthesis and acyl chain alterations (‘remodeling’) of cardiolipin are important for the health and proper functioning of cells. Previous work in our lab has demonstrated that mice deficient in Plaat1 (Plaat1-/-) had significant deficiencies in cardiac cardiolipin content, suggesting an in vivo role of PLAAT1 in cardiolipin metabolism. However, Plaat1-/- mice are poorly characterized, especially with regards to the brain, and study of this tissue, and phenotypic changes related to brain function, could help to delineate the role that PLAAT1 may serve there. Thus, the purpose of this thesis project was to explore the effects of Plaat1-deficiency on mouse brain cardiolipin metabolism and related functions. Lipid analyses of cardiolipin, monolysocardiolipin and phosphatidylcholine revealed small, sex-specific alterations in composition but not content, while analyses of gene expression for relevant biosynthetic and remodeling enzymes exhibited significant transcriptional downregulation in female but not male Plaat1-/- brains. Immunoblotting for mitochondrial protein markers suggested changes to mitochondrial shape in female Plaat1-/- brains, while both male and female Plaat1-/- brains experienced perturbations in subunit content for complexes of the electron transport chain. Lastly, mouse anxiety and short-term memory behaviour was tested, revealing that female Plaat1-/- mice are relatively anxiolytic (relaxed), while neither male nor female Plaat1-/- mice had altered short-term memory. Taken altogether, the data collected in this project suggests that PLAAT1 acts in a tissue- and sex-specific manner for reasons that were unable to explored within the scope of this thesis project. The present thesis project demonstrates both a cellular and physiological role of PLAAT1 in the female brain, and provides a foundation from which further work on PLAAT1 can be explored. These results have implications for the interaction of sex and cardiolipin metabolism in the function of brain mitochondria and resultant behavioural outcomes.
In silico and In vitro Discovery of Plant-Based Pro-Inflammatory Cytokine Inhibitors
(University of Waterloo, 2025-10-28) Huynh, Cassandra
Purpose: Dry eye disease (DED) is a prevalent condition range between 44.2% to 62.9% of the population, with female sex and aging being the greatest risk factors. The pathogenesis of DED is based on the dysregulation of tear film homeostasis, resulting in a vicious circle of desiccating stress, inflammation, and tissue damage. Mild DED is managed with artificial tears and warm compresses, whereas moderate-to-severe DED require additional anti-inflammatory therapies to break the vicious circle. Anti-inflammatory drugs such as corticosteroids are effective treatments but are associated with adverse side effects including increased risk of cataracts and glaucoma. Discovering novel anti-inflammatory therapeutics with minimal adverse side effects would greatly benefit DED patients who depend on anti-inflammatory treatment to mitigate symptoms. Flavonoids are a class of chemicals found in all vegetation; some are known for their anti-inflammatory effects. The numerous members of the flavonoid class could be leveraged to discover novel inhibitors against inflammatory DED targets. The purpose of this thesis was to discover a novel flavonoid that could act as an anti-inflammatory agent to treat DED. Methods: This thesis employed a hybrid approach using network analysis, computational modelling, and in vitro validation. Network analysis was employed to select DED-associated protein targets and candidate flavonoids. “Dry Eye Syndrome” proteins were extracted from the STRING-DISEASE database and were cross-referenced with drug databanks using the functional enrichment analysis tool, ToppFun, for flavonoids. A network analysis tool, Cytoscape (v 3.9.1.), was utilized to visualize and rank DED-associated proteins and flavonoids by number of edge interactions. Two proteins were selected for their distinct roles in the immune response, and two flavonoids were selected for their association with multiple pro-inflammatory DED-associated proteins. Molecular docking and molecular dynamic (MD) simulations modelled and simulated the protein-ligand complex of both protein targets with each flavonoid molecule. Four protein-ligand complexes were assessed for stability and specific residue-ligand interactions. The inhibitory effects of both flavonoids were assessed in vitro with ELISAs against both protein targets. The biocompatibility of the most effective flavonoid inhibitor was assessed with human corneal epithelial cells (HCEC) using an Alamar Blue metabolic activity assay; viability was assessed by evaluating the proportion of live, apoptotic, and dead cells. Results: The network analysis generated a protein-protein interaction network of 64 DED-associated proteins and a drug-protein network of 108 flavonoids. Tumour necrosis factor (TNF) 𝛂 interactions and interleukin (IL) 17A (14 interactions) were amongst the 5 highly ranked proteins and selected for their roles in the innate and adaptive immune response, respectively. Luteolin (19 interactions) and rutin (17 interactions) were the highest ranked flavonoids associated with DED-associated proteins. Molecular docking and MD simulations predicted that both flavonoids could bind directly to the receptor binding sites of both cytokines. However, ELISAs showed that neither luteolin nor rutin could inhibit TNF-𝛂 and TNF receptor interaction (all p≥0.07). On the other hand, both luteolin (IC50 = 16.54 mM) and rutin (IC50 = 8.73 mM) had inhibitory effects against IL-17A and IL-17A receptor interaction (all p<0.01). Metabolic activity and viability of HCEC remained high (all ≥ 85.95%) below 3.0 mM rutin; no significant difference in metabolic activity and viability were detected in all concentrations of rutin compared to the control (all p>0.06). Conclusion: This thesis identified rutin as a novel flavonoid inhibitor of IL-17A. These findings suggest that rutin may play a role in anti-inflammatory therapeutics for DED.
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.

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