About MacSphere

MacSphere is McMaster University's Institutional Repository. MacSphere brings together the institution's scholarly works under one umbrella to preserve and provide ongoing open access to them. MacSphere works have been selected and deposited by members of the McMaster community as part of our collective committment to sharing our knowledge with the world.

MacSphere is supported and hosted by the McMaster University Libraries.

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Students wishing to deposit their PhD or Masters thesis, please follow the instructions outlined by the School of Graduate Studies.

Communities in MacSphere

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Now showing 1 - 5 of 7

Recent Submissions

Optimizing patient-important outcomes in full-thickness macular hole repair
(2026) Nanji, Keean; Ma, Jinhui; Chaudhary, Varun; Braga, Luis; Clinical Health Sciences (Health Research Methodology)
Background: Full-thickness macular holes (FTMHs) are complete defects in the fovea affecting all retinal layers. They greatly impact patients’ visual acuity (VA) and reduce their quality of life. Repair involves pars plana vitrectomy (PPV) with peeling of the internal limiting membrane (ILM), intraocular gas tamponade, and post-operative face-down positioning (FDP). This sandwich thesis presents four published articles with the focus on optimizing patient-important outcomes in the management of idiopathic FTMHs. Chapter 1 provides the relevant background information, rationale, and framework for the thesis. Chapter 2 presents the results of a systematic review and individual participant data meta-analysis of randomized controlled trials (RCTs) evaluating the impact of modifying intraoperative ILM peel size. Specifically, the review compares “small”, defined as 1 disc diameter (DD) in radius or less, compared to “large”, defined as greater than 1 DD in radius. Chapter 3 presents the results of a systematic review and meta-analysis of RCTs evaluating the impact of post-operative FDP versus no FDP. Chapter 4 presents a published editorial outlining the types, the utility, and common pitfalls to feasibility studies. Chapter 5 describes a detailed protocol for a pilot RCT. This study will assess the feasibility of a larger scale trial comparing three versus seven days of post-operative FDP following PPV for FTMH. Chapter 6 summarizes the results of the studies and presents future directions to facilitate further improvements in the management of FTMHs.
Psychological Contract Fulfillment: A Theorized Model and Meta-Analysis
(2026) Harry, Karlene; Hackett, Rick; Schat, Aaron; Business Administration
Despite decades of research on employment relationships, organizations continue to struggle with understanding how unmet or fulfilled promises shape employee commitment and performance. This dissertation addresses this persistent gap by examining the construct of psychological contract fulfillment (PCF) — the extent to which employees perceive that employers have delivered on their obligations — and by quantifying its impact across studies. Drawing from Social Exchange Theory, this thesis undertakes a meta-analysis to validate a theorized model of psychological contract fulfillment (PCF). Specifically, this dissertation is grounded in Social Exchange Theory, which explains how reciprocal obligations form the basis of enduring employee–employer relationships. Psychological contract fulfillment (PCF) represents the degree to which employees perceive that these obligations have been honored. Understanding PCF is therefore critical to clarifying how perceptions of fairness and reciprocity influence workplace behavior. Guided by this theoretical lens, the present study employs a meta-analytic approach to synthesize findings across the PCF literature and to test a comprehensive model linking antecedents, mediators, and outcomes Through meta-analysis, my aim is to bring coherence to the disparate studies on PCF, thereby advancing knowledge that directly informs applied organizational interventions such as employee engagement strategies, leadership communication practices, and HR systems designed to strengthen mutual trust and reciprocity. A key aspect of this is to review, and meta-analytically test, a PCF model proposed and assessed by researchers of primary studies. This research allows for identification of the most common variables and associations, including antecedents, consequences, mediators, and moderators. Also from this process, I develop and test (using meta-analytically derived parameter estimates and structural equation modeling -- SEM) an integrative and theoretically informed model of the antecedents, outcomes, mediators, and moderators of PCF, and propose a research agenda.
Interpretable and Risk‑Aware Decision‑Making in Rail-Truck Intermodal Dangerous Goods Transportation and Flow Estimation
(2026) Bhavsar, Nishit Shaileshkumar; Verma, Manish; Hassini, Elkafi; Computational Engineering and Science
This dissertation investigates rail–truck intermodal transportation of dangerous goods, with particular emphasis on modeling and estimating their flows within highway networks. The dissertation is structured into five chapters. Chapter 1 introduces the research context, motivation, and main contributions of the study. Chapter 2 presents the first study, which develops an alternative tactical-level approach for configuring existing rail–truck intermodal networks for dangerous goods shipments from the perspective of intermodal carriers. Transportation of dangerous goods involves inherently conflicting considerations of cost efficiency and public risk, representing the differing priorities of carriers and regulators. Rather than treating these priorities as competing objectives, the study formulates the problem as a bi-level optimization model that embeds stakeholder preferences within a unified decision-making framework. Extending the classical hub-and-spoke paradigm, the upper-level model represents carrier cost considerations through a single-allocation hub selection problem, while the lower-level model captures regulatory risk concerns. The proposed formulation contributes by (i) explicitly reconciling stakeholder objectives within a single model and (ii) simultaneously determining terminal selection and shipment routing. The model is evaluated using a real-world Canadian rail–truck intermodal network and benchmarked against a conventional bi-objective formulation. Case study results demonstrate improved solution quality and enhanced stakeholder alignment. Chapter 3 extends this work by addressing two major challenges associated with large-scale combinatorial optimization models: computational tractability under parameter variability and interpretability of solutions as operating conditions change. The second study proposes a learning-to-optimize framework that extracts structural insights from historical optimization outcomes, thereby reducing reliance on repeated computationally intensive solver-based solutions. Developed for the configuration of rail–truck intermodal networks carrying dangerous goods, the methodology is demonstrated through a case study on a realistic U.S. intermodal network. Results show that the approach facilitates decision-making under uncertainty by translating complex optimization outputs into intuitive and interpretable decision rules. Chapter 4 focuses on risk assessment in dangerous goods transportation by introducing a comprehensive data-driven, optimization-based framework to estimate dangerous goods flows on road networks. By integrating multiple data sources, the framework estimates and spatially distributes hazardous material flows using an optimization model, providing detailed exposure and vulnerability information for risk analysis and mitigation planning. A case study on gasoline transportation in Ontario, Canada, highlights spatial flow patterns and yields insights into accident dynamics involving hazardous materials, supporting more informed and proactive risk management strategies. Finally, Chapter 5 summarizes the main findings of the dissertation and outlines directions for future research.
Hybrid Manufacturing of Tungsten and Tungsten Composites
(2026) Mahmoud Seyam; Elbestawi, Mohamed; Koshy, Philip; Mechanical Engineering
Laser Powder Bed Fusion (LPBF) is one of the standard additive manufacturing processes, known for its ability to produce near net shaped components with competitive quality and geometric complexity. This technology is highly potent across many sectors, including energy, defence, and manufacturing, as it provides greater design freedom, enabling the creation of lightweight components with higher performance and energy efficiency. Tungsten has gained significant attention in recent years as a potential candidate for high heat flux exchangers in fusion reactors. The high melting temperature of tungsten makes it suitable for operation under the extremely high temperatures inside a fusion reactor. Tungsten is also used in armour piercing artillery due to a combination of high density, strength and hardness. The manufacturing industry also relies heavily on tungsten composites like tungsten carbide cobalt, which is extensively used as a tool material in machining operations due to its superior hardness and toughness. As a result, integrating LPBF into the manufacturing routes for tungsten and its composites is essential for developing the next generation of hardware that meets the demands of the modern world. This Ph.D. research is centred on exploring the application of Laser Powder Bed Fusion for the manufacturing of tungsten composites. The research began with a first phase focused on the pure metal for potential use as a plasma facing material in fusion reactors. An essential part of this phase was conducting multi objective optimization to identify the optimal process windows for dense and crack free tungsten. The outcome of this phase indicated that achieving full solid density and eliminating cracks simultaneously, which is mandatory for the said application, are two contradicting objectives and cannot be fully satisfied by sole manipulation of process parameters. However, a significant reduction in cracking is possible with only a slight sacrifice of relative density by applying multi-objective optimization instead of single-objective optimization. The second phase of this PhD research focused on Tungsten carbide cobalt (WC-Co), for potential processability via LPBF, given its extensive use in Powder metallurgy to produce cutting tools. This phase was carried out in two parts: The first part aimed at identifying the optimum process windows for LPBF of WC-Co and developing form turning tools with integrated cooling features for machining Ti6Al4V. The second part included developing WC-Co rotating tools such as endmills, while utilizing topology optimization to optimize its weight and performance. The outcomes of this phase indicated that LPBF-ed WC-Co with 17% cobalt is suitable for cutting tool applications, including fixed and rotating tools. This phase of research also demonstrated the feasibility of several novel concepts in the spectrum of tool design, such as cooling fins, guiding fins, streamlined internal channels, and lightweight topology optimized endmills. The impact of this PhD research spans both the manufacturing and application domains of WC-Co tools: it significantly reduces the energy required for tool fabrication, while simultaneously enhancing machining performance through improved tool capabilities.
Agency, Access and Action: Reimagining the role of older adults in the food justice movement
(2026) Sweetnam, Andrew Albert; Gillett, James; Health and Aging
This dissertation explores the overlooked role of older adults in the food justice movement, examining how community food organizations mediate the relationship between access to food and supporting agency in later life. While food justice efforts often emphasize equity and the right to food “for all,” the role that older adults play in this is not well understood, despite their increasing reliance on emergency food services. Through a three-article format, this study addresses this gap. The first article offers a narrative review, synthesizing the pathways, barriers, and contributions of older adults in the food justice movement. This initial exploratory paper argues for more intentional inclusion of older adults in food justice scholarship and practice. The second article draws on a community-based survey to examine how community food organizations shape older adults’ perceived food choice and control, revealing a conceptual tension between choice and agency. The third article also draws on this survey data, focusing on collective agency and exploring how community organizations might support older adults in becoming agents of social change rather than passive food recipients. The study findings suggest that while older adults may experience increased confidence and food access through community programs, structural limitations often hinder their capacity to act on that confidence in instituting broader food system change. This dissertation contributes to knowledge by clarifying the distinction between choice and agency in food contexts, reimagining aging as a site of political possibility, and positioning community organizations as key actors in enabling food justice that is both equitable and inclusive across the life course.

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