Faculty of Graduate Studies Online Theses

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Exploring Patterns of Emergency Department Use for People Experiencing Homelessness in New Brunswick
(2025-12-15) Jenna, Hepburn; No; Master of Science; Department of Community Health & Epidemiology; Received; n/a; Not Applicable; Leslie Anne Campbell; Kavish Chandra; Daniel Dutton
Background: Homelessness is a complex and growing issue that negatively affects both individuals and communities. People experiencing homelessness (PEH) often have high levels of unmet health care needs resulting from higher risk of poor health and greater challenges in accessing appropriate health care than the general population. In Atlantic Canada, housing prices are rapidly increasing, reducing housing affordability and accessibility. These population-level factors may play a role in the health of PEH. Objectives: 1) Among individuals with visits to the Emergency Department at Horizon Health, identify PEH and people not experiencing homelessness (“controls”) and describe their demographics, reasons for using the ED, triage level, number of ED visits, and whether they have a primary care provider; 2) To compare ED use among PEH and controls to determine whether there is a difference in the total number of visits, triage level, and whether they have a primary care provider; 3) To determine whether changing housing prices are associated with differences in ED presentation (number of visits and/or reasons) for PEH and controls between 2020 and 2024 across three cities (Fredericton, Moncton, and Saint John). Methods: A repeated cross-sectional study was conducted using administrative health data from four hospitals across three NB cities. Patients were defined as homeless if they were identified as experiencing homelessness in their record or give the address of a shelter or hotel. Nearest neighbour propensity score matching was used to establish a comparable control group, matching patients on facility, sex, and age. Generalized linear models (GLM) were used to assess the effect of experiencing homelessness on the total number of visits (Poisson), average triage level (linear), and primary care provider status (logistic) of PEH and matched controls. Rental price and vacancy rates were graphed by city and year, and correlation coefficients are estimated against ED visits. Results: Between 2020 and 2024, there were 810 PEH and 226,729 housed individuals who presented to the ED. Compared to matched controls, the rate of ED use for PEH was 1.55 times greater for PEH than matched controls (IRR = 1.55, CI: [1.45, 1.66], p < 0.001). Mental health presentations were four times more common among PEH (18.5%) than among controls (4.7%). PEH have 57.7% lower odds of having a primary care provider compared to controls (OR = 0.42, CI: [0.34, 0.52], p < 0.001). PEH had an average 0.11 point lower average CTAS score (coef. = -0.11, CI: [-0.18, -0.03], p = 0.004). ED visits by PEH increased in all cities over the study period, with a particularly sharp rise in Saint John. Rental prices also increased and correlated positively between ED visits by PEH and lowest quartile rental prices (r = 0.36 for one-bedroom units), and negatively with vacancy rate (r = -0.27). Conclusion: This study provides one of the first population-level analyses of ED use among PEH in NB. PEH have higher ED utilization, more acute presentations, and lower access to primary care compared to housed individuals. Patterns of ED use appeared to reflect broader trends in housing affordability, highlighting the need for coordinated housing and healthcare policy interventions.
Access status: Open Access ,
UNCERTAINTY AWARE TEMPORAL RELATIONSHIP MODELLING IN KNOWLEDGE GRAPHS
(2025-12-15) Ramachandran, Deepa; Not Applicable; Master of Computer Science; Faculty of Computer Science; Not Applicable; na; Not Applicable; Dr. Evangelos Milios; Dr. Gabriel Spadon De Souza; Dr. Ga Wu; Dr. Frank Rudzicz
Existing approaches for constructing knowledge graphs (KGs) from text sources effectively capture structural relationships but often struggle to represent the temporal uncertainty inherent in event-based information. Their temporal encoding typically relies on exact timestamp matching, which limits the ability to handle natural temporal variation among events. This thesis introduces Probabilistic Temporal Relationship Modeling (PTRM), a framework that represents events as temporal distributions to capture uncertainty in timing and relationship propagation. PTRM employs distributional embeddings that jointly encode semantic and temporal uncertainty, enabling soft temporal matching through probabilistic overlap computation. Experiments involving 200,000 events from the ICEWS and GDELT datasets demonstrate that PTRM substantially outperforms existing baselines, including temporal knowledge graph embedding methods and classical approaches, while maintaining strong calibration properties essential for decision-critical applications. The results demonstrate that PTRM bridges the gap between rigid timestamp-based methods and the temporal flexibility required for real-world reasoning, achieving state-of-the-art performance in temporal relationship inference under uncertainty.
Access status: Open Access ,
PUBLICLY FUNDED GUIDELINE-RECOMMENDED MEDICATIONS DISPENSED TO COMMUNITY-DWELLING OLDER ADULTS IN NEW BRUNSWICK FOLLOWING HOSPITAL DISCHARGE FOR MYOCARDIAL INFARCTION BETWEEN 2009 AND 2017
(2025-12-11) Manning, Devin; No; Master of Science; Department of Community Health & Epidemiology; Received; na; No; Dr. Sanja Stanojevic; Dr. Rob Stevenson; Dr. Daniel Dutton; Dr. Adrian Levy
BACKGROUND: Pharmacologic therapy plays a central role in secondary prevention following myocardial infarction (MI). Evidence from randomized controlled trials has demonstrated that β-blockers, statins, renin–angiotensin–aldosterone system (RAAS) inhibitors, and antiplatelet agents, particularly P2Y12 inhibitors, reduce mortality, recurrent infarction, and stroke post-MI. Studies in Canada have shown that their use in routine practice remains variable and have not examined the determinants of medication use since P2Y12 inhibitors became standard of care. In New Brunswick (NB), population-based evidence is limited. Understanding these variations is critical for assessing the quality of post-MI care and informing system-level improvements. OBJECTIVES: This study aimed (1) to calculate the annual proportion of community-dwelling older adults (66 years or older) in NB with publicly funded drug insurance and received a dispensation for each guideline-recommended medication class: β-blockers, statins, RAAS agents, and P2Y12 inhibitors, within 90 days of discharge for MI between 2009 and 2017, and determine whether this changed over time; and (2) to determine whether characteristics of the discharging physician were associated with the likelihood of an individual receiving a P2Y12 inhibitor within 90 days of discharge. METHODS: A retrospective, population-based cohort study was conducted using linked administrative health data. The cohort included community-dwelling older adults who were discharged alive from hospital with a primary diagnosis of MI (ICD-10 I21) and had public drug coverage during the study period. Dispensation of each recommended medication within 90 days of discharge was identified from outpatient pharmacy claims. Logistic regression models with generalized estimating equations were used to estimate the associations between physician characteristics and P2Y12 inhibitor use, adjusting for patient age, sex, and length of hospital stay. RESULTS: Among the 2,674 eligible patients, the median age was 78 years (IQR: 71 to 84), and 47% were female. Overall, 79% of patients received a β-blocker, 83% a statin, 72% a RAAS inhibitor, and 70% a P2Y12 inhibitor within 90 days of discharge. Dispensation rate for β-blockers, statins, and P2Y12 inhibitors remained stable across the study period, while RAAS inhibitor use declined. Physician-level variation was evident, compared to cardiologists, patients discharged by general practitioners (OR 0.38; 95% CI 0.28, 0.51) or other specialists (OR 0.47; 95% CI 0.32, 0.68) were less likely to receive P2Y12 inhibitors post-discharge. Patients discharged by female physicians were less likely to receive P2Y12 inhibitors (OR 0.69; 95% CI 0.51, 0.92). No statistically significant associations were found with physician graduation decade or training location. DISCUSSION: Post-MI use of evidence-based pharmacotherapies among publicly insured older adults in NB was comparable to rates reported elsewhere in Canada and remained below recommended targets. The observed variation in P2Y12 inhibitor use across physician groups suggest that structural factors, such as clinical specialization, and drug reimbursement policies, may influence access to guideline-recommended therapies.
Access status: Open Access ,
Integrating DVFS and Task Scheduling to Improve Energy Efficiency for Heterogeneous Edge Devices: A Reinforcement Learning Approach
(2025-12-13) Wang, Haoyu; Not Applicable; Master of Computer Science; Faculty of Computer Science; Not Applicable; n/a; Not Applicable; Saurabh Dey; Jie Gao; Qiang Ye; Man Lin
Energy efficiency is a primary design objective for embedded and edge computing platforms, which operate under tight power and thermal constraints while serving latency-sensitive workloads. In this thesis, we focus on CPU power management on heterogeneous big.LITTLE systems for single-threaded, periodic tasks that operate under a soft Target Execution Time (TET) constraint. Specifically, we design and implement a user-space, reinforcement-learning-based controller that jointly performs dynamic voltage and frequency scaling (DVFS) and task scheduling on heterogeneous edge devices. The controller uses a learned policy to select both the CPU cluster and operating performance point in each execution window so as to minimize per-window energy consumption while satisfying TET constraints. A compact, time-aware state representation makes the policy explicitly TET-conditioned, enabling it to adapt to different TET values at runtime without retraining. Using a hardware-in-the-loop evaluation on an ODROID-N2+ platform, we compare the learned policy against the standard Linux \texttt{ondemand} governor on keyword spotting (KWS) and YOLO-lite object detection workloads. With TETs randomly drawn from the 3.5--4.5\,s range, the proposed controller reduces per-cycle energy by up to 10.6\% for KWS and 7.3\% for YOLO-lite while maintaining high TET satisfaction rates.
Access status: Open Access ,
'And that one takes a big bite of one of those nice red apples': Portraits of Native Women in Thomas King's Green Grass. Running Water and Medicine River
(1998-04) McKay, Christina A.S.; Not Applicable; Master of Arts; Department of English; Not Applicable; unknown; Not Applicable; Patricia Monk; R. Tetreault; J.A. Wainwright
Given the multiplicity of voices and perspectives (female and male, Native and non-Native) existing in Canada, the question now is how we might collectively learn to reconcile our differences. In western culture, both gender and culture are thought to be fixed, predetermined and separate. But when viewed from a Native perspective, gender and culture are actually aspectival, rather than essential. The women in Thomas King's novels Green Grass, Running Water and Medicine River shed light on a Native world view which resists white western patriarchal assumptions about culture and gender and suggests entirely different roles for women and a new paradigm for human relationships. In Chapter One, I explore how and why the essentialized image of the "Imaginary Indian" arose and persists in white western culture and the consequences this stereotype has for Native peoples, and Native women in particular. In Chapter Two, I examine the ways both the Native and non-Native women in GGRW and MR are marginalized by the white western culture's essential views about race and gender. The women in King's novels prove their capacity to resist racism and sexism and survive by showing their communities how to look at the world from multiple perspectives. Chapter Three looks at the strategies Native women use not only to resist maginalization, but to re-imagine and transform the culture(s) they live in. These strategies are based on the Native practice of braiding. In the same way that different strands weave together to form a braid, culture and gender are also not individualistic (essential), but individualized (aspectival). My conclusion will extend my discussion of Thomas King's writing to address the question of cultural difference and Native values in Canada. I will make particular reference to the current debate about Canadian immigration policy, which, rather than embracing difference, suggests that immigrants must conform to the cultural norms of the dominant society in Canada.
Access status: Open Access ,
Neural Compression for Scalable Question-Answer Retrieval
(2025-12-11) Khiet, Moamen; Yes; Master of Computer Science; Faculty of Computer Science; Not Applicable; n/a; Not Applicable; Dr. Hassan Sajjad; Dr. Frank Rudzicz; Dr. Ga Wu
Question-answering systems at scale face fundamental performance barriers when traditional vector databases transition from exact to approximate search, causing substantial degradation in both query throughput and retrieval quality. While compression can address these challenges, existing compression approaches either apply generic transformations ignoring retrieval task structure (PCA) or require retraining entire embedding models (Matryoshka), limiting practical applicability. This thesis introduces neural compression for question-answer retrieval through two-stage learning that compresses 384-dimensional context embeddings to 32 or 64 dimensions while preserving semantic information. The approach trains an autoencoder to compress context embeddings using cosine similarity loss, then trains a mapper network to predict compressed codes directly from question embeddings using mean squared error loss in compressed space. Both networks are trained on the training split (72%, 86,400 pairs). We evaluate this approach on 120,000 question-answer pairs spanning six knowledge domains, comparing against six baseline methods (FAISS, HNSW, ScaNN, PCA, Matryoshka, zero-shot) across six dataset scales (20K to 120K) with three iterations per configuration, totaling in 198 experimental runs. Results demonstrate that neural compression achieves 0.1725 ROUGE-1 score compared to FAISS’s 0.1624 (+6.2% improvement) while reducing storage from 184 MB to 7.7 MB (96% reduction) and increasing throughput from 151 to 7,861 queries per second (52× speedup). Neural compression is the only method whose quality improves with scale (+2.5% from 20K to 120K samples) while all baselines degrade (-6% to -13%). The performance crossover occurs at approximately 40K samples, earlier than hypothesized, as FAISS quality degrades from curse of dimensionality effects before its algorithmic transition to approximation. These results show that task-specific learned compression through asymmetric architecture compressing only contexts while keeping questions full dimensional enables exact search at scales where high dimensional methods must approximate, fundamentally changing scalability characteristics of retrieval systems.
Access status: Open Access ,
Assessing the effects of sampling design and data integration in spatio-temporal fisheries models
(2025-12-11) McDonald, Raphaël; No; Doctor of Philosophy; Department of Mathematics & Statistics - Statistics Division; Not Applicable; Dvora Hart; Yes; Orla Murphy; Craig Brown; Joanna Mills Flemming; David Keith
Many communities around the world depend on the socio-cultural and economic benefits derived from fisheries. To ensure these continued benefits, fisheries management relies on accurate estimates of fish population size and health obtained through the stock assessment process. This thesis develops and improves upon various statistical methods used within the stock assessment process. We first show how common sampling designs do not strongly impact model results, but also how sampling effort allocation can introduce time-varying biases if the strata-specific sampling effort is not proportional to strata size. We next turn our attention to analyses that occur early in the stock assessment process, such as length-weight relationships. While complex statistical models are often necessary to estimate these relationships, their outputs are routinely used without accounting for their associated uncertainties. We present simple methods to highlight the increase in precision achieved by error propagation. The next two chapters focus on developing methods for the inclusion of novel types of data within stock assessment models. The first is a benthoscape map. Focusing on sea scallops in the Bay of Fundy, we demonstrate how benthoscape maps can be interpreted as habitat features and help inform the estimation of catchability and probabilities of encounter to improve parameter estimation and identify biologically meaningful area boundaries. The second is drop camera data. We propose various model modifications to account for the resolution difference between datasets. This work identifies a previously unknown relationship between the size of survey tows, the underlying spatial distribution of the population, and the accuracy of the survey. High aggregation or high noise in the spatial distribution results in the survey indices being more precise than the drop camera indices even with substantially smaller sample sizes. This thesis develops novel statistical methods useful to the broader field of fisheries science, with contributions for improved data integration, error propagation, and sampling design, while opening various new avenues of future work in all these same fields.
Access status: Open Access ,
GRPO-Rad: Group Relative Policy Optimization for Radiology Report Summarization
(2025-12-10) Nassiri, Fargol; Not Applicable; Master of Computer Science; Faculty of Computer Science; Not Applicable; N/A; No; Vlado Keselj; Hassan Sajjad; Frank Rudzicz
Radiology report summarization requires condensing detailed findings into concise impressions, a task where traditional supervised fine-tuning (SFT) often struggles to balance syntactic correctness, clinical accuracy, and brevity. This thesis investigates Group Relative Policy Optimization (GRPO) as a superior alternative, enabling direct optimization of a composite reward function combining ROUGE-L syntactic similarity and length constraint. Using the MIMIC-III dataset and Qwen 3.0 decoder-only models (0.6B and 1.7B parameters) with parameter-efficient LoRA fine-tuning, we systematically evaluate 24 configurations varying model size, prompting, and few-shot learning. Results demonstrate that GRPO consistently outperforms both zero-shot baseline and SFT across syntactic (ROUGE-L) and clinical (F1-RadGraph) metrics. The optimal GRPO configuration achieves 32.65 ROUGE-L and 30.28 F1-RadGraph, representing a 16% improvement over SFT with statistical significance (p < 0.05). This work presents the first application of GRPO to medical text, establishing it as a robust framework for clinical documentation tasks requiring multi-objective optimization.
Access status: Open Access ,
Design, Simulation, and Techno-Economic Evaluation of a Novel Process for Ethanol Recovery from Fermentation Broths
(2025-12-09) Campos Assumpcao de Amarante, Rafael; Not Applicable; Doctor of Philosophy; Department of Process Engineering and Applied Science; Not Applicable; Dr. Xianshe Feng; Yes; Dr. Jan Haelssig; Dr. Darrel Doman; Dr. Adam Donaldson
Addressing rising energy needs, particularly in industry, transportation, and heating, while simultaneously decreasing the rate of greenhouse gas emissions, is a critical challenge facing society nowadays. Liquid biofuels produced from renewable sources, such as ethanol, have received increased research attention because they show long-term viability potential and fit the current transportation infrastructure. Ethanol is produced by the anaerobic fermentation of sugars obtained from renewable biomass. Conventionally, ethanol is recovered from the aqueous fermentation broth using at least two distillation steps combined with a dehydration step. However, this configuration requires large amounts of energy and is particularly inefficient, mainly due to the low ethanol concentrations achieved in the fermentation broth, and the formation of an ethanol-water azeotrope. In this thesis, a new extraction-pervaporation system was proposed and investigated for use in ethanol recovery. In this process, ethanol is extracted from the fermentation broth using organic solvents and recovered from this mixture by pervaporation. It was envisioned that this new process configuration would lead to improved energy efficiency and economics for the ethanol production process. The proposed process was investigated using numerical and experimental techniques. New polymeric membranes were developed and were shown to be effective in separating ethanol/2-ethylhexanol and ethanol/pentanol mixtures. The permeates were obtained at similar or higher concentration than that achievable in enriching distillation columns. The pervaporation mass transfer process was modelled accounting for the effect of concentration polarization and for concentration-dependent diffusion in the membrane layer, and results showed that, under the conditions studied, the mass transfer resistance in the membrane controls the pervaporation process. It was also shown that higher temperatures and feed concentrations result in higher fluxes through the membrane. A pervaporation numerical model incorporating a membrane permeability model based on the results achieved in previous sections was developed. Ethanol extraction from the broth was also modelled, as well as the fermentation process. A techno-economic analysis was carried out and results indicated that, although the current economic performance is lacking, the extraction-pervaporation process is more energetically efficient than the distillation process, achieving similar ethanol concentrations while requiring less than half of the amount of energy input.
Access status: Embargo ,
ANALYSIS OF SUSTAINABLE MINING SUPPLY CHAINS
(2025-12-10) Amegboleza, Angela Akofa; Not Applicable; Doctor of Philosophy; Department of Industrial Engineering; Not Applicable; Dr. Mehmet Gumus; Yes; Dr. Uday Venkatadri; Dr. Alexander Engau; Dr. Yana Fedortchouk; Dr. Ali Ulku
The future of mining relies on solutions that are sustainable, efficient, and credible for the communities that live alongside mining operations. This research provides an integrated framework that addresses both ends of the spectrum: artisanal and small-scale mining (ASM), where immediate water conservation and basic treatment capabilities are crucial; large-scale mining operations, where decarbonized energy logistics within transparent governance structures are essential; as well as a unified decision analytics framework for conflict management in mining communities. This research addresses these gaps through four interrelated studies.. First, the review of sustainable operational efficiency (SOE) in the mining industry (MI). Second, the establishment of multi-stage water treatment networks that meet regulatory standards for reuse. Third, the development of transport modes for natural gas (NG) delivery to decrease the effects of traditional fuels. Finally, the implementation of commitment mechanisms that transform benefit-sharing and grievance processes from aspirations into realities. At the core of this framework are multi-objective optimization models that evaluates trade-offs aligned with the quadruple bottom line (QBL) of the sustainability framework. As well as decision analysis models for effectively translating stakeholder preferences into clear priorities through sensitivity assessments. Together, this dissertation contributes a cohesive field-ready methodology for designing mining systems for both ASM and large scale mining that preserve waterbodies, minimize emissions, and secure license to operate by aligning engineering design with responsible community-informed governance.
Access status: Open Access ,
Linking foraging behaviour of female grey seals (Halichoerus grypus) to population size, diet, and reproductive success
(2025-12-10) Henry-Adams, Max; Not Applicable; Master of Science; Department of Biology; Received; Xavier Bordeleau; Not Applicable; Dr. Nell Den Heyer; Dr. Robert Lennox; Dr. Sara Iverson; Dr. Don Bowen
Understanding the movement patterns and foraging behaviour that marine predators use to navigate and adapt to patchy and unpredictable prey availability has important implications for individual fitness. In capital breeding animals where the acquisition and storage of energy is critical to financing the costs of reproduction, these species offer interesting model systems to study the relationships between foraging behaviour, diet, and reproductive success. Northwest Atlantic grey seal (Halichoerus grypus) females are wide-ranging, long-lived, capital breeders, that are known to undergo extensive pre-breeding period foraging trips where they gain body mass prior to expending roughly a third or more of parturition body mass to support a single precocial pup during a short lactation period. Using hidden Markov Model estimates of foraging behaviour derived from satellite telemetry data obtained between 1995 and 2018, this study first uses generalized linear models (GLMs) to explore the potential effects of age and population density-dependent regulation of foraging behaviour in a grey seal population experiencing decelerating population growth. Results from 62 female deployments suggest that foraging behaviour leading up to the breeding season is impacted by increasing population size, likely because of intraspecific competition for access to the main prey during this foraging period. Although the impact of female age was less than population size, I found a dome-shaped pattern where the total distance travelled and the number of foraging locations used peaked in prime-age females. To test whether these differences in foraging tactics relate to variation in female diet, GLMs were then used to relate estimates of foraging behaviour from 50 deployments to diet estimated at instrument recovery through stable isotope (SI) signatures and quantitative fatty acid signature analysis (QFASA). The total distance travelled was linked to the spatial distribution of the primary prey species found in the diet, where individuals with more redfish (Sebastes sp.) in the diet travelled greater distances than females with sand lance (Ammodytes dubius)/mixed diets. Females that travelled greater distances and spent more time in area-restricted search also consumed relatively energy dense prey species. Finally, foraging behaviour and diet estimates were related to maternal postpartum mass (MPPM) and pup weaning mass to evaluate the fitness consequences associated with different foraging tactics and diets. The foraging tactics used appeared to depend on female size, with those estimated to be using more benthic foraging tactics having a higher MPPM. At the same time, diet diversity was negatively related to MPPM, but energy density was not, suggesting that larger females may have been foraging more efficiently or using a “quantity over quality” foraging tactic, although future studies using simultaneous estimates of the quantity of prey consumed would be required to confirm this hypothesis. Regardless, there was no detectable relationship between estimated foraging effort and diet metrics and pup weaning mass once MPPM and maternal age were included in models. With these data collected on an increasing grey seal population, evidence suggests that the environmental conditions and prey abundance were sufficient to support multiple foraging tactics leading to high population-level reproductive rates. This work demonstrates that individual variation in foraging behavior and diet contributes to individual fitness and population dynamics in free-ranging marine predators.
Access status: Embargo ,
Evaluation of Protein Markers and Development of Reporter Cell Lines for Detecting Mitochondrial Stress in the Context of Splicing Kinase Loss
(2025-12-10) Gibson, Alexander; Not Applicable; Master of Science; Department of Pathology; Not Applicable; Dr. Neale Ridgway; Not Applicable; Dr. Shashi Gujar; Dr. Jayme Salsman; Dr. Graham Dellaire
Mitochondrial homeostasis is essential for cellular function, and its dysregulation is implicated in cancer and neurodegenerative disease. I evaluated methods for assessing mitochondrial stress to study how splicing kinase loss affects homeostasis. Mitochondrial health relies on fission, fusion, and mitophagy. Based on prior work linking PRP4K to autophagy regulation, I hypothesized that PRP4K loss might cause damaged mitochondria accumulation. Bulk protein assays (western blotting for TOM20, ATP synthase γ, MTCO2) showed no significant changes. To overcome this, I used MitoTracker imaging in cells with CCCP, a mitophagy inducer, and found PRP4K depletion consistently elevated MitoTracker intensity, suggesting increased mitochondrial mass. Using CRISPR/Cas9, I generated a mitophagy reporter MCF7 cell line expressing Mito-Rosella, a tandem pHluorin/dsRed mitochondrial reporter. This assay allowed measurement of mitophagy changes following PRP4K depletion, establishing a platform to assess the role of PRP4K and its regulated splicing events in mitophagy and mitochondrial homeostasis.
Access status: Embargo ,
Corrosion Behavior and Electrochemical Stability of Additively Manufactured Copper-Based Alloys for Marine Applications
(2025-12-09) MORSHEDBEHBAHANI, KHASHAYAR; Not Applicable; Doctor of Philosophy; Department of Mechanical Engineering; Not Applicable; Dr. Suraj Persaud; Yes; Dr. Mohammad Saeedi; Dr. Kyle Tousignant; Dr. Ali Nasiri; Dr. Paul Bishop
The fabrication of metallic components through advanced 3D printing has created new opportunities for producing intricate geometries and complex shapes that are difficult, if not impossible, to achieve using conventional manufacturing methods. While additive manufacturing (AM) offers these advantages, industries such as the marine sector require a thorough understanding of the properties of AM-produced alloys to ensure they meet the minimum performance requirements for service. In particular, marine applications demand not only sufficient mechanical strength but also reliable corrosion resistance. This thesis focuses on a comprehensive investigation of the corrosion behavior of additively manufactured nickel–aluminum bronze (NAB) and Monel 400—two alloys widely used in marine engineering. Their corrosion performance in 3.5 wt.% NaCl solution, representing seawater, is systematically compared with that of their wrought counterparts. To achieve this, the microstructural features, crystallographic texture, and phase distribution of the alloys are first characterized using advanced analytical techniques. Subsequently, their passivity and electrochemical corrosion behavior are evaluated over different immersion periods. The findings reveal that NAB develops a relatively stable corrosion product film after approximately 40 hours of immersion. However, post-heat treatment, while necessary for achieving the desired mechanical properties and reducing susceptibility to localized corrosion, negatively impacts the alloy’s overall corrosion resistance. The results further indicate that the corrosion response of heat-treated AM NAB is primarily governed by its microstructure and remains isotropic regardless of the AM technique used. Surface condition also plays a significant role, with a moderately roughened surface providing the best corrosion resistance. In the case of AM Monel 400, chemical composition emerges as the dominant factor influencing corrosion resistance. Unlike NAB, heat treatment enhances the corrosion performance of Monel 400. Although extended immersion reduces its resistance, the performance remains satisfactory for marine service.
Access status: Embargo ,
Blended to be better: Design, characterization, and functionalization of recombinant chimeric spider silks for tailored biomaterials
(2025-12-09) Ghimire, Anupama; No; Doctor of Philosophy; Department of Biochemistry & Molecular Biology; Not Applicable; Dr. Keiji Numata; Yes; Dr. Stephen L. Bearne; Dr. Kathryn Vanya Ewart; Dr. Danielle Tokarz; Dr. Jan K. Rainey
Spider silks are protein-based biomaterials renowned for their exceptional strength and extensibility, with potential applications in the biomedical, textile, and automotive industries. Orb-weaver spiders produce up to seven silk types for functions such as locomotion, web construction, egg protection, and prey wrapping. The cannibalistic and territorial behavior of spiders limits large-scale harvesting of natural silk, highlighting the importance of recombinant silk production. This thesis focuses on the design, production, and characterization of recombinant chimeric silks with tailored properties. A pyriform-aciniform silk fusion protein, Py2W2, was engineered by fusing two pyriform (Py) and two aciniform (W) silk repeat units. When wet-spun into fibers and stretched in air, water, or ethanol, Py2W2 exhibited tunable mechanics. Air-stretched fibers reached ~157% extensibility, comparable to natural flagelliform silk, while ethanol-stretched fibers achieved superior strength. These properties exhibited a correlation with secondary structure, where increased β-sheet content enhanced strength. Py2W2 fibers also showed water-compatibility absent in Py2 fibers and outperformed Py2 and W2 fibers in mechanical tests. As an alternative strategy, composite fibers (Py2+W2) were produced by mixing Py2 and W2 proteins prior to spinning. Like Py2W2, composite fibers displayed tunable mechanics influenced by post-spin stretching, though variability was observed in some spinning conditions. Further optimization of spinning process offers a practical route for generating tunable composite fibers without complex fusion designs. To introduce biological functionality, a chimeric protein W2Cma2ap-55 was designed by combining aciniform repeats (W2), a major ampullate silk C-terminal domain (Cma2), and the G-protein-coupled receptor (GPCR) ligand apelin-55 (ap-55). Films and fibers derived from W2Cma2ap-55 retained intact ap-55, as confirmed by antibody recognition. Compared with W2Cma2 fibers, W2Cma2ap-55 fibers exhibited higher strength and toughness with similar extensibility. Both film types were noncytotoxic to HEK 293A cells, and W2Cma2ap-55 films activated ERK phosphorylation, confirming apelin-55-mediated GPCR signaling. Similarly, cells adhered to W2Cma2ap-55 fibers, demonstrating their suitability as bioactive scaffolds. Overall, this work establishes chimeric silks as versatile biomaterials. Rational protein design and processing enabled tailoring of mechanical properties (Py2W2, Py2+W2) and the integration of bioactivity (W2Cma2ap-55). These findings highlight the potential of engineered spider silks for advanced biomedical and functional applications.
Access status: Open Access ,
A Critical Discourse Analysis of News Media on the Portapique (Nova Scotia) Mass Shooting
(2025-12-08) Scott, Diane; Not Applicable; Master of Social Work; School of Social Work; Not Applicable; Dr. Ardath Whynacht; Not Applicable; Dr. Nancy Ross; Dr. Marjorie Johnstone
The deadliest mass shooting to occur in Canadian history began in the town of Portapique, Nova Scotia, in April of 2020. The study employed critical discourse analysis in a media analysis of written news coverage of the Portapique mass shooting published between 2020 and 2024. The analysis revealed epistemic injustices in how the Portapique mass shooting was narrated as news media reflected and reproduced colonial forms of power within the socio-political, cultural, and historically shaped context. Findings include the failure of news media to contextualize the mass shooting as an act of gendered violence in both the creation and responses to the Portapique mass shooting, how the place identity of rural Nova Scotia diverted attention from the social context of the Portapique mass shooting, and how carceral logic through discourse on criminalization, police reform, and legislative changes, created a simulacrum of justice while sustaining the violence that carceral systems are meant to address. These findings demonstrate how news media consistently decontextualize the mass shooting from its root causes through narratives that align with carceral logic and patriarchal neoliberal ideologies. The study demonstrates how news media discourse can perpetuate and maintain existing power relations that enable mass violence, such as the Portapique mass shooting, to occur.
Access status: Open Access ,
Practical Application of Large Language Models in the Nuclear Power Generation Industry
(2025-12-04) de Costa, Mishca; Not Applicable; Master of Science; Department of Engineering Mathematics & Internetworking; Not Applicable; n/a; Not Applicable; Dr. Guy Kember; Dr. Hamed Aly; Dr. Issam Hammad
Nuclear power organizations steward large, fragmented, and partially digitized textual corpora that impede knowledge access and complicate decision support. Effective application of large language models (LLMs) is further hindered by dense, site-specific Canada Deuterium Uranium (CANDU) jargon and multi-definition acronyms underrepresented in public training data. Existing applied nuclear LLM efforts emphasize isolated retrieval or proprietary model announcements, leaving gaps in integrated, auditable workflows for safety classification, terminology normalization, and structured outputs. This thesis contributes a deployment-first, prompt-centric framework comprising: (i) a GPT based Station Condition Record (SCR) safety event scoring approach emphasizing balanced recall/precision over an imbalanced corpus; (ii) an ensemble jargon detection and expansion pipeline combining LLM heuristics with deterministic and probabilistic methods; and (iii) structured output / function-calling patterns that enhance traceability and governance readiness when mining data from structured nuclear databases using hybrid NL-to-SQL techniques. Collectively, the results provide an evidence-based blueprint indicating when prompt engineering plus glossary normalization can defer costly domain pretraining, complementing parallel work on retrieval augmentation and secure local experimentation.
Access status: Open Access ,
On Ornstein-Uhlenbeck State Space Models
(2025-12-08) Li, Shanglun; Not Applicable; Doctor of Philosophy; Department of Mathematics & Statistics - Statistics Division; Not Applicable; Liqun Wang; Not Applicable; Théo Michelot; Mike Dowd; Hong Gu; Toby Kenney
This dissertation develops and applies the Ornstein--Uhlenbeck state space model (OUSSM) for analyzing noisy, irregularly sampled, and multi-dimensional time-series data, with a particular focus on human microbiome dynamics. We first introduce the OUSSM framework to account for measurement errors in microbiome data, providing more reliable estimation of mean reversion rates and robust profile likelihood confidence intervals. A likelihood-based testing procedure is proposed to compare microbial dynamics between datasets, for example before and after periods of disruption. These methods are validated through simulations and applied to microbiome datasets. We then investigate the optimal sampling scheme for the OUSSM. Theoretical results and extensive simulations reveal that estimation accuracy exhibits a U-shaped dependence on the sampling interval, with moderate gaps yielding the most efficient inference. Repeated measurements are shown to substantially improve estimation. Allocating 10\%--20\% of the samples to repeated samples at already-sampled time points achieved the most accurate estimation of mean-reversion rate across a range of simulations. The choice of which time points should be repeatedly sampled made very little difference to the estimation. Finally, we extend the OUSSM framework to the multi-dimensional setting by developing a factor OUSSM, addressing identifiability challenges via parameter constraints and proposing estimation procedures based on the Kalman filter. Simulation studies demonstrate the model's ability to recover latent dynamics under a range of scenarios, while real-data applications illustrate how multidimensional interactions among microbial genera can be captured more effectively than with traditional one-dimensional approaches. Together, these contributions establish a comprehensive methodological framework for modeling, inference, and sampling design in the OU process with measurement error. The results not only improve the statistical characterization of microbial temporal dynamics but also extend broadly to applications in ecology, finance, and beyond.
Access status: Embargo ,
Assessing UAV Operability and Estimating Probability of Detection in Arctic Search and Rescue Operations Using Fuzzy Logic
(2025-12-06) Hakimipanah, Mona; Not Applicable; Master of Applied Science; Department of Industrial Engineering; Not Applicable; Peter Kikkert; Not Applicable; Hamid Afshari; Ronald Pelot; Floris Goerlandt
Unmanned Aerial Vehicles (UAVs) are increasingly used to support Search and Rescue (SAR) operations in Canada’s Arctic and Northern regions, where long distances, severe weather, and limited infrastructure create major response challenges. Yet, year-round UAV operability and detection performance in these environments remain under-examined. This study addresses that gap through two objectives: RQ1 evaluates UAV operability across Northern Canada using environmental thresholds and hourly ECCC weather data (2018-2024) for 46 communities and 2 staffed High Arctic outposts. RQ2 develops a fuzzy-logic model of the Probability of Detection (PoD) using a Type-1 Mamdani FIS built from expert-elicited factors. Operability findings show strong geographic and seasonal variability, with high operability during summer and sharply reduced opportunities in winter months. The PoD model highlights Crew Experience, Contrast, and Flight Speed as major contributors to detectability. Together, the results provide a decision-support framework to guide UAV-SAR planning and operational readiness across northern Canada.
Access status: Open Access ,
Crossed Modules of Inverse Semigroups as Internal Categories
(2025-12-05) Zeidler, David; Not Applicable; Master of Science; Department of Mathematics & Statistics - Math Division; Not Applicable; na; Not Applicable; Theo Johnson-Freyd; Neil Julien Ross; Dorette Pronk; Darien DeWolf
A classical result of Spencer and Brown (1976) shows that the category of crossed modules of groups is equivalent to the category of 2-groups. We extend this equivalence to inverse semigroups. We construct a notion of crossed module of inductive groupoids, equipped with a groupoid action. Inductive groupoids are equivalent to inverse semigroups via the Ehresmann–Schein–Nambooripad Theorem (Schein, 1965). We show that crossed modules of inductive groupoids are equivalent to a category of categories internal to inductive groupoids, and consider examples of such crossed modules arising in the work of Dokuchaev, Khrypchenko, and Makuta (2022). The intuitions developed in proving the groupoid case allow us to show that crossed modules of inverse semigroups, defined using a semigroup action and modified crossed module axioms, are equivalent to a category of categories internal to inverse semigroups. Finally, we show that the two categories of crossed modules we have defined are equivalent.
Access status: Open Access ,
Investigation of the Semi-Mechanistic Boiling Model for use in Numerical Aeroengine Fire Tests
(2025-12-03) Logan, Dylan; No; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; Dr. Michael Pegg; No; Dr. Baafour Nyantekyi-Kwakye; Dr. Dominic Groulx; Dr. Mohammad Saeedi
This thesis investigates the application of the semi-mechanistic boiling model within the mixture multiphase framework in ANSYS Fluent to improve the accuracy of numerical simulations of aeroengine fire tests. Developed in collaboration with Pratt & Whitney Canada (PWC), this work addresses critical limitations in existing computational methods which fail to capture the complex multiphase heat transfer processes, particularly those involving the boiling of lubricating oils under fire conditions. The research includes an investigation of the boiling model and its tunable parameters through calibration against experimental data of a publicly available channel cooling test case, and an application to a simplified oil tank geometry representative of a complex aeroengine component. The findings demonstrate that the selected model effectively captures boiling-induced cooling and vapor generation effects, leading to more accurate temperature predictions and improved simulation reliability.

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