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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Atomistic Modeling of Metal Oxide Behaviors in Nanothermite Reactions and Lunar Water Production
(University of Waterloo, 2026-06-02) Zhichao, Liu
This dissertation addresses two challenges in heterogeneous redox reactions of metal oxide materials, namely the reaction mechanism of Al-based energetic nanothermites and the in-situ production of water using lunar oxide materials. Although extensive theoretical and experimental efforts have been focused on both topics, a complete mechanistic understanding of the reaction mechanisms in both topics remains lacking. The first part of this work focuses on the fundamental reaction mechanisms of Al-based nanothermites, with emphasis on the typical system of Al/CuO. Despite extensive experimental and theoretical studies, the exact ion transport pathways and rate-limiting steps remain unclear because nanothermite reactions involve coupled redox processes, phase transformations, heat release, and ion transport across dynamically evolving condensedphase interfaces. In particular, the naturally formed amorphous alumina layer on Al, as the rate-limiting phase, is expected to play a crucial role in governing oxygen transport, interfacial redox chemistry, and ignition behavior. However, the mechanistic contribution of the surface amorphous alumina layer is still not fully understood. This dissertation establishes a mechanistic framework for heterogeneous redox reactions in Al-based nanothermites through systematic investigations of oxygen migration across representative bulk phases and key interfaces. The results identify the rate-controlling and exothermic steps that govern oxygen transport and ignition, and connect the proposed atomistic mechanisms to experimentally observed preignition behavior, reaction kinetics, and the wide range of reported activation barriers. The second part of this work addresses the data-driven discovery of lunar oxide materials for Solar-Wind (SW)-derived H retention and subsequent water production, especially in sunlit lunar regions. Although increasing evidence suggests that hydrogen implanted by SW can be retained in lunar mineral rims and converted to molecular water, the underlying mechanisms that govern H retention and H₂O formation remain poorly understood. In addition, the large elemental space of lunar-based oxides makes the experimental identification of promising materials highly challenging. To address this issue, this dissertation develops a data-driven materials discovery framework that integrates Density Functional Theory (DFT) calculations, materials databases, and Machine Learning (ML) models to evaluate local reaction energetics and materials screening criteria, which include H insertion energy, H₂O formation energy, H diffusion length, and the fugacity ratio of H₂O to H₂ to identify promising candidate materials. By applying these criteria, eleven high-/mixed-valence Fe-bearing oxides, together with lunar magnetite, are identified as promising materials for SW-implanted H retention and in-situ H₂O production, while most of the Fe²⁺-bearing lunar minerals are found to be intrinsically unfavorable for in-situ H₂O production. Overall, this dissertation provides new mechanistic insights into heterogeneous redox reactions in energetic and planetary oxide materials systems. The findings advance the fundamental understanding of nanothermite ignition and combustion, while also establishing a predictive framework for discovering lunar materials capable of supporting the future In-Situ Resource Utilization (ISRU).
Aluminum Nitride Photonic Integrated Circuits with Applications to Cold Atoms
(University of Waterloo, 2026-06-02) Videnov, Nikolay
Quantum sensing has become foundational to many modern technologies. Precision time keeping is core to the global positioning system (GPS), magnetometry is core to mineral discovery for mining. The ability to measure with unparalleled sensitivity has driven many major technological improvements across diverse fields. From simple neutral atom vapour cells to sophisticated ion traps, atoms are a preeminent quantum sensing platform. However, these systems remain difficult to make field-deployable, owing largely to the complexity and fragility of their optical systems. As the invention of the laser and commercialization of external cavity diode lasers (ECDL) enabled increasingly complex trapped atom experiments this thesis aims to take a step toward the next stage: scalable, robust, and portable trapped-atom-based quantum sensors. I argue that a primary limitation to achieving this goal lies in the reliance on bulk optical systems, which exhibit poor size, weight, and power (SWaP) characteristics, are prone to misalignment, and require specialized assembly. To overcome these limitations, I propose the use of photonic integrated circuits (PIC), leveraging fabrication tools and techniques from the semiconductor industry to create a versatile PIC "toolbox" for the trapped-atom community. The unique requirements of such systems motivate the choice of aluminum nitride (AlN) as the waveguiding material—a high-index, ultra-wide band gap, and electro-optically active medium that meets the optical and material needs of trapped-atom applications but has received relatively little attention compared to other established platforms. This thesis therefore details a reproducible nanofabrication process for AlN waveguides that achieves state-of-the-art propagation losses through the use of atomic layer deposition and rapid thermal annealing. Rather than treating this process as proprietary, the complete recipe is shared here for the benefit of the broader AlN research community. I also present the first demonstration of a hybrid ECDL incorporating an AlN photonic integrated circuit, an important milestone toward realizing fully integrated on-chip light sources. These hybrid ECDL operate near 852 nm and 650 nm, addressing optical transitions in cesium and barium ions. Finally, I describe a novel dual-mode phase shifter that combines electro-optic and thermo-optic tuning within a single fabrication layer, enabling both high-speed modulation and large index changes. Collectively, the work presented in this thesis represents a significant step toward fully integrated, chip-scale optical systems for trapped-atom experiments—paving the way for the next generation of compact, deployable quantum sensors.
New Techniques for Lower Bounds in Graph Streaming and Distributed Computing
(University of Waterloo, 2026-06-02) Sundaresan, Janani
In this dissertation, we study lower bounds in the streaming and distributed computing models for graph problems. Both models arise naturally in the design of algorithms for the massive graphs that are ubiquitous in practice today. In the streaming model, the edges of the graph arrive in an arbitrary order and must be processed without storing the entire graph. Of particular interest is the semi-streaming setting, in which the algorithm is allowed space that is near-linear in the number of vertices. The stream may be scanned multiple times, and the goal is to minimize the number of passes needed to solve the problem. In distributed computing, each vertex acts as a computational agent and initially knows only its immediate neighborhood. Vertices communicate by sending messages along the edges of the graph. Communication proceeds in synchronous rounds: in each round, every vertex can send a (possibly different) message to each of its neighbors, receive all incoming messages, and then perform local computation. In the CONGEST model, each such message is restricted to a length logarithmic in the number of vertices. The goal is to minimize the number of rounds required to solve the problem. We highlight three results from this dissertation for graphs with n vertices: 1) The number of passes required to find a maximal independent set in semi-streaming is Ω(log log n). Our result is tight, matching a prior algorithm. This is the first multi-pass lower bound for this problem. 2) The number of passes required to find any (1-ε)-approximation of maximum matchings is Ω(log (1/ε)) in semi-streaming. This is the first lower bound on the number of passes with a dependence on ε for any constant ε. 3) We prove an Ω(log log n) lower bound on the number of rounds required to detect a triangle in CONGEST. This is the first multi-round lower bound for this problem. Lower bounds in both models are proven via communication complexity: the input graph is split among multiple players who send messages to each other over a limited number of rounds. A common theme underlying the highlighted results is to build on and extend the round-elimination technique from communication complexity literature. Our main technical contribution is to adapt this method for a range of different settings to obtain the first nontrivial multi-pass and multi-round lower bounds for these problems.
A multi-methods investigation of a long-term care staffing policy in Ontario
(University of Waterloo, 2026-06-02) El Hajj, Karen
Introduction: Long-term care is an important sector in the care continuum of older adults in Ontario. The challenges facing long-term care include, but are not limited to, lack of funding, complicated funding structures, limited workforce availability, and growing resident acuity (Long-Term Care Staffing Study Advisory Group, 2020). In 2021, the Ontario government introduced and funded a series of programs to increase the hours of care and the number of beds available in long-term care (Office of the Premier, 2020). The policy response came at a time of growing public concerns on the state of long-term care in Ontario, and excess resident mortality during the pandemic (Office of the Premier, 2020). Through this policy initiative, the Ontario government aimed to achieve an average of four hours of direct care per resident per day, and an average of 36 minutes per resident per day of allied health care, by March 31, 2025 (Office of the Premier, 2020). In addition to the average care hour policy, the Government of Ontario (2022) announced a goal of creating 30,000 new beds by 2028. Given the complex nature of the challenges facing the long-term care sector, there is a need to understand the potential impacts of the policy initiative on Ontario’s long-term care sector and workers. Study Aims and Methods: To understand the potential impacts of the increase in hours of care policy, and its associated programs, a multi-methods investigation was conducted. Study 1 aimed to understand the impact of the staffing policy on the Government of Ontario budget. To do this, a budget impact analysis model was developed (Mauskopf et al., 2017), quantifying ministry programs and announcements. Study 2 aimed to understand the impact of the staffing policy on the long-term care sector and identify any potential effects on other parts of Ontario’s health system. Study 2 explored the grey literature published on long-term care (Godin et al., 2015); selected documents were examined using the document analysis method (Bowen, 2009) and analyzed thematically (Braun et al., 2019). The thematic analysis informed the subsequent health policy analysis using Walt and Gilson’s (1994) policy framework. In addition to the policy analysis, a theory of change (Knowlton & Philips, 2009) was developed to map the ministry’s strategies to implement the staffing policy. Study 3 aimed to understand the perspectives of long-term care staff on the introduction of the policy, identify potential barriers and facilitators to the policy’s implementation across long-term care homes and suggest additional policy initiatives that could support or enhance the policy’s implementation. For study 3, a qualitative descriptive study, as described in Sandelowski (2000) was done using semi-structured interviews. Fourteen participants were interviewed to understand their perspectives on the policy’s effects and implementation. Interview data were analyzed using qualitative content analysis (Sandelowski, 2000). Results: After creating a budget impact model for the government policies, Study 1 provided cost estimates for the ministry programs and a bed funding database based on announced ministry projects, from 2021-2022 to 2029-2030. Study 1 provided estimates for the number of direct care workers required under the new policy until 2029-2030. In a no intervention scenario, ministry spending is estimated at $7.4 billion in 2029-2030. Compared to a baseline scenario where no policy or programs are introduced, the staffing policy would increase ministry spending to $13.32 billion in 2029-2030. The policy analysis provided insight into the staffing policy’s implementation and sustainability. Competing efforts and laws from the Ontario Government were identified as a potential factor that could limit the effects of the policy. A dynamic labour market, where competition is found between operators, health sectors, and direct care workers was identified as a challenge to ensure an increased number of hours and workers across long-term care homes. In Study 3, participants provided insight on their experiences in long-term care and their opinions on the staffing policy. Participants discussed limited staff availability, limited wage compensation, the demanding nature of long-term care work and competition across health sectors as some of the challenges in recruiting and retaining long-term care workers. Facilitators of this policy’s implementation included educational programs for personal support workers, and training workers for their roles. Participants identified potential efforts for the government to consider such as regulations and initiatives that could create a better work environment for workers and improved care for residents. Conclusion: It is evident that addressing the current staffing challenges in long-term care requires efforts beyond adding more long-term care workers. The complex relation among factors including funding, work environment and rules and regulations has a direct impact on the recruitment and retention of long-term care workers. On a larger scale, better coordination between government agencies and ministries should be considered to enhance the effect of policies on the health care labour force. The introduced policy efforts coupled with supplementary policies targeting the health sector labour force and working conditions are some of the ways to ensure that the policy can influence change in long-term care. The increase in care hour policy, and the increase in beds in long-term care are important steps to start resolving the issues in long-term care. Ensuring that the policy achieves its aims has proved to be much more challenging, requiring ministry consideration of potential consequences that might affect long-term care and the larger health sector in Ontario.
Advancing characterization of spatiotemporal dynamics of dissolved organic matter after landscape disturbance to inform and protect drinking water treatability
(University of Waterloo, 2026-06-02) Klanderud, Carter
Surface waters are critical sources of drinking water globally. The quality and availability of water from these sources is threatened by landscape disturbances (e.g., urbanization, agriculture, resource extraction) including climate shocks (e.g., wildfires, intense precipitation). To ensure reliable and consistent supply of drinking water, offline reservoirs are often used for raw water storage prior to treatment. While largely designed for managing water quantity and availability, reservoir storage can also affect water quality. In addition to providing bypass capacity during contamination events (e.g., accidental spills/releases), hydrodynamic factors such as dilution, physico chemical and biological transformations occurring within reservoirs, including photodegradation, flocculation, and microbial primary production, can alter water quality relative to inflowing source water. Drinking water treatment needs and performance are driven by many aspects of source water quality, one of the most critical being organic matter. Landscape disturbances can substantially change organic matter concentration and character in source water because they alter hydrologic connectivity, mobilizing organic matter from the landscape and affecting its delivery to and transport within receiving waters. Rapid shifts in source water quality can challenge water treatment plants (WTPs), potentially increasing operational costs or leading to service outages. Raw water reservoirs can help attenuate such source water quality change; however, this is not typically done by design. Here, ultraviolet absorbance at 254 nm (UV254)—a real-time indicator of dissolved organic matter (DOM) concentration and aromaticity—was intensively monitored in a wildfire-impacted drinking water system with two off-line reservoirs in series to demonstrate how engineered storage can be leveraged to dampen landscape disturbance-associated changes in source water quality and increase treatment resilience. High-frequency sampling of UV254 did not show meaningful differences across depth, lateral position within the reservoir cells, and time of day. Notably, UV254 standard deviation was 1.6 and 2.2 times lower in the first and second reservoirs, respectively, than in the river source; respective peak UV254 values were 1.45 and 1.6 times lower, indicating effective attenuation of DOM from the river by the reservoirs in series. This attenuation also reduced polyaluminum chloride coagulant dosing by approximately 70 mg/L during a period of particularly deteriorated source water in 2023, helping reduce aluminum residuals and the potential for exceeding regulatory maxima in treated water. Accordingly, this work demonstrates that raw water reservoirs can be intentionally and strategically designed to attenuate disturbance-driven fluctuations in source water quality, thereby enhancing drinking water system resilience and supporting climate change adaptation. Watershed-scale source water quality monitoring is essential for assessing cumulative watershed effects to enable effective management of drinking water supplies and detection of threats to water treatability. However, it can pose substantial logistical challenges. Source water quality, including the concentration and character of organic matter, can change during the unavoidable period between sample collection and analysis, making effective sample preservation critical for maximizing return on monitoring effort. While a standard method is available for the preservation of dissolved organic carbon (DOC), a common surrogate for DOM, its implementation is not always feasible. Difficult access to remote or hydrologically critical headwater locations for sample collection, limitations on in situ sample preservation, and associated challenges in transporting collected samples to analytical facilities within prescribed holding times can compromise data integrity and representativeness. Several alternative preservation (e.g., filtration, freezing) techniques for organic carbon concentration and character are often used when adherence to Standard Methods is impractical; however, their efficacy is highly variable and has not been systematically evaluated. Thus, the direct and combined effects of temperature (e.g., refrigeration, freezing), filtration, and acidification were systematically investigated here using four natural water matrices of diverse quality. This analysis revealed that freezing effectively preserved DOC except when combined with acidification (which would be suggested by extension of Standard Methods); the combination of these methods caused significant shifts in DOC in some cases. Specific ultraviolet absorbance at 254 nm (SUVA) changed within 24 hours of sample collection in some water matrices; this was also reflected by change in the humic substances fraction of DOM, which was measured by size-exclusion chromatography using liquid chromatography-organic carbon detection (LC-OCD). DOC in unpreserved water samples remained stable (i.e., < 10% change) for up to seven days after collection. Accordingly, while Standard Methods remain the benchmark for preserving DOM in water samples, this work advances practical strategies to maximize the value and interpretability of monitoring data at conditions where adherence to these methods is not feasible. Collectively, these findings highlight the value of offline raw water reservoirs and robust sample preservation strategies for enhancing WTP resilience to source water quality change. Reservoirs can effectively attenuate rapid shifts in DOM concentration and character following climate shocks such as wildfires and substantially reduce extremes in coagulant demand. Understanding the stability of DOM during the unavoidable period between sample collection and analysis further helps maximize the value of raw water monitoring to inform water quality and treatability change without compromising data integrity. By integrating high-frequency reservoir monitoring with matrix-specific preservation practices, drinking water utilities can better anticipate source water variability, prepare for disturbance, and improve overall treatment performance and resilience.
Advancing ITR as a standard metric for real-time BCI performance assessment
(University of Waterloo, 2026-06-02) Li, Junsong
The current standard metric for assessing brain-computer interface (BCI) system performance is the information transfer rate (ITR). However, in our previous work using ITR to evaluate real-time BCI-controlled electric wheelchair performance, we obtained low ITR values while significantly outperforming prior studies in terms of task completion time. This led to the belief that ITR is an inconsistent metric for real-time applications, potentially indicating misleading results when comparing systems. The discrepancy in performance led to examining the limits of ITR and proposing an alternative metric, Jun’s Information Transfer Rate (JITR), aimed at addressing specific issues often overlooked in the current BCI system evaluations. In the literature, several key assumptions behind ITR are not met, including a memoryless system, independent choices, a constant update rate, and equally distributed choice probabilities. Common post-processing methods, such as weighted smoothing, feedback, and error correction, break these assumptions. As a result, ITR values become unreliable for comparison for real-time systems, motivating the use of JITR that maintains the basis of maximum channel bandwidth log2𝑁 while adding term in to penalized system delay and low accuracy. This approach affords opportunities to fine tune and optimize BCI configurations and predict task performance. To validate JITR, the update rate and weighted sum smoothing parameters were manipulated to find the configuration with highest transfer rate. Utility was tested in a simulated driving task, where performance was predicted using the JITR performance index. As a result, JITR was able to predict task completion time, if immediate pre-trial accuracy is given. JITR limitations, such as the need to model fatigue, learning effects, and false positives to improve precision and recall, and benefits are discussed, representing a step toward a reliable metric for assessing BCI systems.
Assessing the Effectiveness of Bridging Programs for Internationally Educated Physiotherapists in Canada
(University of Waterloo, 2026-06-01) Baisalov, Abdumanap
Background: Physiotherapists are regulated allied health professionals whose broad scope of practice encompasses the assessment, diagnosis, prognosis, and management of movement dysfunction and physical impairment. They play a substantial role in clinical medicine, and their work is grounded in evidence-based medicine and the principles of the applied sciences. Despite their importance in our health care system, workforce shortages for physiotherapists are being felt across Canada, with projected shortages of licensed physiotherapists worsening in the coming decades (Watson et al., 2026). An important source of new physiotherapists is the integration of internationally trained physiotherapists. A common integration pathway is through bridging programs, which support internationally educated physiotherapists (IEPTs) in adapting to the Canadian healthcare context. Developed in the late 1990s, bridging programs have been associated with smoother transition experiences and have provided useful educational inputs that improve graduates’ knowledge and skill levels (Austin & and Rocchi Dean, 2006; Chiang et al., 2024a; Johnson & Israel, 2011). However, much of the available research literature on bridging programs focuses on professions other than physiotherapy, or includes only a limited number of physiotherapist respondents, or prioritizes quantitative designs. As a result, in-depth qualitative research examining how bridging programs function for internationally educated physiotherapists remains limited. Consequently, the specific barriers IEPTs face and the form of support most likely to facilitate their successful integration remain poorly understood. Research on bridging programs for internationally educated physiotherapists remains limited, even though these professionals provide essential treatment and rehabilitation to patients across a wide range of clinical settings throughout the country. This gap warrants focused investigation, particularly inquiry directed at strengthening the training of newcomer physiotherapists, enhancing their professional knowledge and building confidence as they move on the pathway to registration. While much of the broader literature focuses on immigrant physicians and nurses, less attention has been directed to other allied health specialties, especially physiotherapists. Moreover, commonly reported indicators of program success (e.g., exam pass rates or employment) can miss the qualitative dimensions that shape the experiences, professional identity, and adaptation of bridging program graduates. This proposed study fills an important gap by exploring the lived experiences of IEPTs and how bridging programs shape their career trajectories. This study is among the first to focus on internationally educated physiotherapists and their experiences with the bridging program as they progress through the integration process into the Canadian healthcare system. Specific aims: This study aims to assess the effectiveness of bridging programs in supporting the professional adaptation of IEPTs in Canada. Also, an important part of research is identifying facilitators that improve the chances of successful integration into a new healthcare system and barriers that may delay it. Methods: Adopting a qualitative case study approach, the research involved in-depth interviews with graduates and an instructor of a bridging program for IEPTs to explore their experiences. For understanding their experience, seven participants, including six graduates who are currently practicing physiotherapists and an instructor of a bridging program in Canada, were interviewed. The interviews were conducted in a semi-structured format via one-on-one Teams videoconferences. Interviews ranged from 45 to 60 minutes in duration. Three members of the research team, the supervising professor, a graduate student, and a volunteer student, independently checked the equivalence of the transcripts and synchronized them with the audio files of the interviews. In addition, the documents of the two currently active bridging programs, the McGill University Equivalency in Physiotherapy Program and the University of British Columbia Physio Refresh, were thoroughly analyzed in comparative terms of their core elements. A rigorous thematic analysis, guided by an evaluation framework (Kirkpatrick’s New World model), was applied to ensure that all facets of “effectiveness” were considered. Codes were generated using the Braun and Clarke methods. Results: In the study, interviewed participants showed a significant positive impact of the bridging programs for adaptation in the Canadian health system. The finding also revealed factors that facilitate successful careers, and notable barriers for internationally educated physiotherapists to achieving positive outcomes on their pathway to becoming registered physiotherapists in Canada. Factors of success included early information support on accreditation processes for physiotherapists, availability of financial support, professional networking, and social support. The common barriers for our participants were financial pressure, bureaucratic uncertainty, and the complex regulation of the licensing process. Useful recommendations from the participants were to streamline the process of accreditation; unification of the process of licensing physiotherapists in Canada for those trained in historically closer health systems; in addition, graduates emphasized the crucial role of the clinical placements, the positive impact of an individual approach for every IEPT's credentials, and the importance of peer support. Discussion: This research highlights the work of bridging programs in successfully integrating internationally educated physiotherapists into Canadian practice. Within their bridging program, study respondents reported that they were introduced to cultural differences and to new professional identities that are intended to help them meet the requirements of provincial physiotherapy association norms. Graduates aimed to obtain accreditation in the provinces as an independent physiotherapist, a goal strongly associated with completing the bridging program. Provincial requirements for registering new physiotherapists in Quebec do not require a national exam after successful completion of an accredited bridging program, whereas other provinces require it. This shows one of the positive aspects of registration in Quebec, as it was continuously underscored by participants in the study. A comparative look shows that the McGill University program has a longer clinical placement, while the UBC program has a shorter overall duration and more flexible modes of delivery, such as a hybrid format or remote delivery. Notable strengths of the bridging programs were that the higher number of seats offered by UBC allows physiotherapists to have more chances of receiving an offer from the Physio Refresh program. In addition, because UBC does not mandate permanent resident status in Canada for their candidates, the Physio Refresh program might be an option for physiotherapists without permanent resident status. The McGill program offered the opportunity to omit the national exam mandate after finishing their Equivalency in Physiotherapy Program and extended clinical placement exposure. The limitations for both programs were still limited capacity of the programs, high tuition charges, and periodic repetition of course materials from students' initial degrees, and for clarity, these courses were prescribed by the regulatory body (Ordre Professionnel de la Physiothérapie du Québec, 2026) and could not be changed by the bridging programs. Conclusion: The bridging programs for internationally educated physiotherapists help their graduates improve their chances of licensing in physiotherapy in Canada and start their careers with confidence. Findings of this study identified several facilitators that have not received attention in past studies. These include peer network support for the learning process, as well as early clinical placement, interprofessional communication, exposure to new work culture, financial support, and an advanced level of professional language. Notably, barriers included complex, non-coordinated regulations governing the physiotherapy specialty and individual factors that prolonged the registration process. The findings of this study will be helpful in the design of streamlined and standardized processes for credential recognition, with a “one window” approach for candidates from regulating bodies in the provinces. For candidates, it will be more effective to understand before applying and moving to Canada, the main requirements for the licensing process, the expected timeline for credentials recognition, and the bridging programs’ curriculum. IEPT students starting the McGill University bridging program joined the mainstream master 's-level physiotherapy cohort and were not segregated into a separate Equivalency in Physiotherapy Program stream, which was a consequential facilitator of their academic and professional development. This integration created organic peer learning opportunities, reduced professional isolation, and fostered a sense of belonging within a community of practice. These relational dimensions of learning align directly with the Reaction level of the New World Kirkpatrick Model (Kirkpatrick & Kirkpatrick, 2022).
Disorder Effects in Topological Phases of Matter
(University of Waterloo, 2026-06-01) Yi, Jinmin
The thesis is divided into two parts, both focusing on the disorder effects in topological phases of matter. The first part explores the properties of Weyl semimetals with quenched disorder. A fundamental fact of condensed matter physics is that sufficient disorder typically drives a Fermi liquid metal into an Anderson insulator: a compressible but non-conducting phase. Recently, topological semimetals have emerged as another way a metallic phase can be realized. We show that, unlike ordinary metals, at least some topological semimetals are immune to localization and become a diffusive metal with a nonzero density of states at arbitrarily weak disorder. We present several physical arguments, based on diagrammatic perturbation theory and Keldysh field theory, as well as an exact mapping onto a two-dimensional array of coupled replicated Hubbard chains, to back up this claim. The second part focuses on the disorder effects in one-dimensional spin chains. We define a new notion of order and disorder parameters for Ising-symmetric spin chains with quenched disorder, and establish a rigorous trade-off theorem between them. We show that in such a disordered ensemble, the system must have one and only one of the following: a nonzero $O(1)$ order parameter or a nonzero $O(1)$ disorder parameter with even parity under the Ising symmetry. We also present a rigorous treatment of the rare region effects in the disordered Ising chain, and show that the rare regions do not destroy the trade-off theorems. This theorem also provides a foundation for string order parameters in disordered average symmetry-protected topological (SPT) phases.
Dust and Domesticity: Maintenance and Toronto’s Reform Movements (1900-1930s)
(University of Waterloo, 2026-06-01) Falif, Fathima Mahara
Maintenance practices remain an understudied area within architectural discourse. Dusting, sweeping, and mopping—in both the domestic and public spheres—have often been deemed inconsequential to our experience of the built environment. The absence of maintenance within architectural discourse seeks to preserve a facile and autonomous image of capital A architecture. By examining maintenance—specifically what is being maintained—we challenge this idealized version of architecture and instead expose its deeply interconnected social relations and systems of care. This thesis uses dust as a lens to evaluate maintenance practices within Toronto’s 19th-century reform movement. Centered on Toronto’s first immigrant neighborhood, the Ward, this thesis traces the discourse on housework in relation to concerns over nation-building within Toronto’s larger settler-colonial landscape. It contrasts two approaches to housework practices within the Ward, highlighting the tension between the institutional presence of public health and that of grassroots organizations. As dust frames the gendered, social, and material dimensions of this investigation, this thesis finds that domestic maintenance practices became deeply intertwined with questions of citizenship, belonging, and agency. Specifically, this thesis analyzes the use of sanitary inspectors, municipal housekeepers, and publications such as The Little Blue Book Series by public health to enforce a standardized ideal of housework on Toronto’s growing immigrant working class. In contrast, grassroots organizations such as Visiting Housekeepers and Settlement Houses, which operated intimately within the Ward, recognized situated domestic conditions and cultural differences and sought to use housework as a tool of empowerment. In its transgression and destabilization of spatial borders, dust defies conventions of architectural order. By examining the overlooked narratives of dust, this paper highlights the resistance of immigrant communities and challenges dominant narratives of urban reform.
Graphene Oxide Membrane Technology for Refrigerant-Free Air Dehumidification
(University of Waterloo, 2026-06-01) Burton, Nikolai
Graphene oxide membranes have emerged as promising candidates for refrigerant-free air dehumidification because they combine high water-vapour permeance with high selectivity. Practical deployment has remained limited for several reasons. Most studies have used vacuum filtration to fabricate graphene oxide composite membranes. Although vacuum filtration aligns flakes well and yields high selectivity and permeance, scale-up remains costly. The brittle nature of graphene oxide has also necessitated porous membrane supports, which add mass-transfer resistance that can exceed the resistance of the selective layer itself. As a result, reported composite membranes often show permeances close to, or below, those of graphite oxide films ≈ 6 μm thick (1.01×10-5 \frac{mol}{m^2sPa}). This outcome persists despite the thinner graphene oxide layer that should produce a higher permeance from the composite membrane architecture. As such, measured permeance and selectivity are available for graphene oxide composite membranes with varied supports and oxidation levels, but few studies have examined their integration into larger-scale applications such as HVAC dehumidification systems. These studies rarely quantify how module-scale mass-transfer resistances affect measured membrane properties across operating conditions, even at the laboratory scale. Graphene oxide membranes make this question especially important because their high water-vapour flux and selectivity can make the bulk gas-phase transport resistance non-negligible. Bulk-gas concentration polarization can then skew the measured permeance as water-vapour flux approaches the diffusion rate from the bulk gas to the membrane surface. Most laboratory studies have also explored only a narrow range of vacuum conditions and therefore do not resolve the operating envelope that governs flux, crossover, and pump demand. Reported thermodynamic metrics often rely on idealized assumptions, including isothermal vacuum compression and vacuum pumps with 90% polytropic efficiency, rather than actual vacuum-pump power consumption under realistic operation. Together, these limitations leave no clear framework for separating intrinsic membrane performance from module-scale transport losses or for identifying the operating conditions that govern practical dehumidification. This thesis addressed these gaps through scalable graphene oxide membrane fabrication, simulations with bulk mass-transfer resistances, and system-level models that include transport and realistic vacuum-pump behaviour. This work produced composite membranes with coated areas of 225 cm2 with water-vapour permeances up to 1.5×10-5 \frac{mol}{m^2sPa}, and selectivity above 1000. Electrospun polystyrene supports with 93% porosity increased permeance by up to 27%, confirming that support resistance set the observed performance ceiling. Additional experiments and simulations showed that test-cell hydrodynamics changed the apparent permeance by ≈ 20% which required correction for gas-phase and support-layer resistances to recover the intrinsic membrane properties. System-level modelling showed that real vacuum pumps, pressure losses, residence time, and driving-force collapse reduced performance and limited the coefficient of performance to below 0.5 at the tested scale. These findings establish a scalable route to high-performance graphene oxide membranes and identify membrane materials, module design, and vacuum hardware as coupled constraints on HVAC implementation. Although the work in this thesis has moved the needle forward slightly, future work should target full module optimization under realistic operating conditions. Emphasis should be placed on membrane support architecture, gas-phase transport, thermal integration, and vacuum-pump losses. Reduced-order and dimensionless models could then provide a clearer basis for membrane sizing, operating-envelope mapping, and system scale-up.
Adaptive Optimization Framework for Antenna Structure Design
(University of Waterloo, 2026-06-01) Huang, Lin
As terahertz and subterahertz technologies continue to develop, there is an increasing need for compact antennas with broad bandwidth, stable impedance matching, and reliable directional response. The micro circular log periodic antenna, or MCLPA, is a promising candidate because its self similar geometry can support wideband operation within a com-pact planar structure. However, its design is controlled by several coupled geometric param-eters, including the number of rings, scaling factor, angular spans, and tooth thickness. These parameters interact in a nonlinear way, which makes manual optimisation difficult and often requires many full wave electromagnetic simulations. This thesis presents an Efficient Self Adaptive Optimiser, or ESAO, for simulation guided antenna design under limited computational resources. Instead of using fixed objec-tive weights throughout the search, the proposed framework evolves both antenna parame-ters and objective priorities during the optimisation process. The framework combines sev-eral adaptive components, including feature salience analysis, surrogate assisted candidate screening, multi fidelity evaluation, hybrid search strategies, progressive dimensionality re-duction, and convergence control. Together, these components allow the optimiser to focus simulation effort on more informative regions of the design space while still maintaining sufficient exploration. The proposed method is applied to the design of an MCLPA operating in the millimetre wave and subterahertz range. Simulation results show that the optimised design improves the operating bandwidth and maintains stable realised gain and impedance matching com-pared with the initial seed design. The final design uses eight log periodic elements with a scaling factor of 0.78 and achieves a simulated operating band from approximately 60.3 GHz to 100.4 GHz, with an average realised gain of 6.1 dBi and a minimum reflection coef-ficient of minus 37.1 dB. To support the simulation results, selected MCLPA samples were fabricated on silicon substrates and tested using a blackbody radiation source, PTFE optical components, and high impedance voltage readout. Because calibrated terahertz power measurement and vec-tor network analysis were not available for the fabricated samples, the experimental study focuses on relative voltage response rather than absolute antenna gain or responsivity. The measured results show repeatable voltage changes under blocked and unblocked radiation conditions, an overall increase in response with blackbody temperature, and orientation de-pendent behaviour. These observations provide practical evidence that the fabricated MCLPA responds to incident broadband radiation and that the simulation guided design is physically meaningful. Overall, this work contributes a practical optimisation framework for expensive elec-tromagnetic design problems and demonstrates its use through the design, fabrication, and relative experimental characterisation of an MCLPA. The results suggest that adaptive opti-misation can reduce manual design effort while also providing interpretable relationships between antenna geometry and electromagnetic performance.
Hydrogeological, Mineralogical, and Geochemical Characterization of a Gold Mine Tailings Containment Area at the Giant Mine, NT
(University of Waterloo, 2026-06-01) Hilger, David
The Giant Mine is an underground and open-pit, greenstone-hosted gold mine in Yellowknife, Northwest Territories, Canada. Mining operations (1948-1999) resulted in waste products of flotation tailings (85 wt%) and roaster residues (14 wt%) and arsenic (As) trioxide roaster waste (ATRW; 1 wt%), which were deposited in tailings containment areas. A water treatment system has been operational since 1999, utilizing the Northwest Tailings Containment Area (NW-TCA) as intermediary storage. The hydrogeology, aqueous geochemistry, and mineralogy were examined to understand the loading and transport of As and antimony (Sb) within the NW-TCA. From 597,000 to 1,050,000 m3 of mine dewatering effluent (As: 22.2 ± 4.7 mg L-1; Sb: 0.79 ± 0.11 mg L-1) transitioned through the NW-TCA during the study period (2017-2022). A water balance, constructed with components of precipitation, evaporation, change in surface storage, effluent in, and effluent out, found that on average, 384,000 m3 y-1 of water discharged out of the NW-TCA annually. Very large, persistent downward hydraulic gradients in the southern half of the containment area indicate the predominant direction of flow. Stable water isotope and water chemistry measurements indicate porewater in areas of high-water table is influenced by mine dewatering effluent. Isotope mass balance indicates 60% of the mine dewatering effluent, which contains high concentrations of As, is sourced from water cycled through the NW-TCA. Mine dewatering effluent, NW-TCA surface-water, and the tailings porewater contain elevated concentrations of As, Sb, Zn, and other metal(loid)s. The impact of the mine dewatering effluent is minimal in areas with a deep vadose zone, containing lower concentrations of As. Hydrological simulations indicate groundwater flow rates into the deep groundwater flow system from the NW-TCA would be modest in the absence of the mine dewater pond because the system is near net evaporative in the absence of mine dewatering effluent. Acid-base accounting indicates the tailings pose low or no acid-generation risk. Oxygen concentrations indicate sulfide oxidation extends to 4 m depth. Oxidative dissolution of sulfide minerals in the vadose zone releases As, Sb, Zn, Co, Ni, and Cu to the porewater. A portion of this As is subsequently incorporated into secondary Fe(III) (oxyhydr)oxides. Below the oxidation zone, reducing conditions drive As and Sb release by reductive dissolution of Fe(III)-bearing roaster residues. At the base of the TCA, highly reducing conditions result in partial As sequestration through sulfate (SO4) reduction. Infiltration of mine dewatering effluent has resulted in elevated groundwater As in areas influenced by the holding pond. Effective management of As and Sb requires consideration of spatial- and temporal-dependent mobilization and attenuation processes within the TCA. Bulk As K-edge XANES linear combination fitting indicates that solid-phase hosts of As in the TCA are approximately equal proportions As(-I), associated with arsenopyrite and arsenical pyrite, and As(V)-O/As(III)-O associated with roaster residues and secondary Fe(III) (oxyhydr)oxides. Solid-phase hosts of Sb are primarily roaster residues based on results from SEM-EDS, Sb K-edge XANES, and chemical sequential extractions. Solid-phase characterization reveals that extensive sulfide oxidation is restricted to the upper 1 m of the profile, with the persistence of minimally altered arsenopyrite and pyrite. Alteration of Fe(III) oxide roaster residues was not detected in mineralogical or spectroscopic analysis. Aqueous As speciation contrasts with thermodynamic predictions, indicating redox disequilibrium and limits of microbial activity. Dissolved As(III) is present in the oxidizing vadose zone porewater, sourced from arsenopyrite oxidation. As(V) is present in reducing groundwater, attributed to the infiltration of oxygenated surface water and reductive dissolution of As(V)-bearing oxides. Methylated As compounds are present in the anoxic vadose zone and shallow groundwater zone, likely formed as a product of metabolic detoxification. In comparison to freshly deposited tailings analyzed in 1999, there is evidence of sulfide oxidation but low alteration of As-bearing minerals. Aqueous geochemical distributions of As and Sb in the neutral mine drainage sourced from sulfidic flotation tailings and roaster residues are not coupled. This research provides new knowledge into the hydrogeochemical processes controlling contaminant metal(loid) release and attenuation in mixed mine wastes composed of sulfidic flotation tailings and roaster residues. Remediation strategies are planned to be implemented at the NW-TCA in the near future. Completion of a year-round water treatment plant will eliminate the use of the NW-TCA as a storage reservoir for mine dewatering effluent. The findings of this study can be used to inform estimates of the rate of contaminant release, attenuation, and transport in the NW-TCA under different management scenarios.
Matroids with large branch-depth
(University of Waterloo, 2026-06-01) Turner, Lise
We prove a conjecture of DeVos, Kwon and Oum that matroids of high branch-depth have large uniform minors or large fan minors. The groundset of a large matroid of low branchdepth admits a partition into many sets such that the union of any subcollection has low connectivity. Most of the work in proving the conjecture goes into finding obstructions to finding such partitions. In particular, we prove that forbidding a given uniform matroid and a given fan as a minor guarantees the existence of such partitions in all sufficiently large matroids.
Studying quantum gravity via simplicial Lorentzian path integrals
(University of Waterloo, 2026-06-01) Padua Arguelles, Jose de Jesus
This thesis investigates the Lorentzian path integral as a framework for quantum gravity, focusing on how its off-shell causal structure shapes physical predictions. The work shows that different assumptions about causality strongly affect phenomena such as cosmological tunneling, black hole thermodynamics, and gravitational entropy. A central result is the discovery that certain off-shell causality violations in the Lorentzian path integral give rise to the Euclidean saddle points that dominate semiclassical calculations, providing a concrete mechanism through which Euclidean features emerge from fundamentally Lorentzian dynamics. To study these questions non-perturbatively, the thesis uses Regge calculus, a discrete version of General Relativity that makes Lorentzian path integrals computationally tractable. The framework enables detailed studies of two key settings: Euclidean de Sitter space and evaporating black holes. In the de Sitter case, Euclidean saddles are shown to govern both cosmological tunneling amplitudes and entropy-related state counting, requiring unusual off-shell geometries with singular causal structures. In the black hole context, the work develops a Regge-calculus approach to replica wormholes and reproduces the Page curve within a four-dimensional gravitational model that includes matter. Overall, the thesis advances both the conceptual understanding and computational treatment of Lorentzian quantum gravity, establishing Regge calculus as a powerful tool for studying quantum aspects of gravity.
Optimization-based Constrained Trajectory Generation for Autonomous Vehicles
(University of Waterloo, 2026-06-01) Kolapalli, Venkata Kameswara Praneeth
In this thesis, we study problems in constrained trajectory generation for autonomous vehicles with a focus on designing optimization-based algorithms. First, we investigate the problem of designing trajectories required to satisfy signal temporal logic specifications for non-holonomic car-like robots. Autonomous mobile robots are actively applied to execute complex tasks, such as package delivery, autonomous taxiing, and search-and-rescue. Signal Temporal Logic (STL) offers a powerful formalism for such complex tasks. We formulate the problem as a nonlinear program to generate trajectories for a multi-robot system with car-like robots to perform complex tasks specified with STL grammar. The proposed approach uses an exact closed-form nonlinear parameterization of the kinematics to evaluate the STL grammar in the NLP. We demonstrate the effectiveness and scalability of our algorithm in practice compared to a state-of-the-art baseline. Second, we also investigate the problem of designing trajectories with obstacle avoidance constraints for quadcopters. Often robots operate in obstacle-free spaces that can be approximated by orthogonal polytopes. We leverage this problem structure and design an algorithm that is massively scalable in practice. Initially, we study the combinatorial optimization problem of decomposing orthogonal polytopes into a minimum number of boxes. We design a novel integer linear program to solve the problem exactly and show that a simple rounding scheme recovers near-optimal solutions from the relaxed linear program in practice. Next, we heuristically select a subset of the boxes to traverse in and then study the continuous problem of generating piecewise trajectories constrained to stay within the selected subset of boxes. We formulate a biconvex optimization program by parametrizing the trajectory and design an algorithm to recover a locally optimal solution using convex alternating minimizations. Finally, we demonstrate that our algorithms are significantly faster than existing baselines and are scalable for large-scale real-world quadcopter scenarios. Our solution approaches focus on generating trajectories that are provably correct with optimization-based techniques. We demonstrate our algorithms on real world platforms to show that our formulation is tractable for robots in practice.
Towards Indistinguishable Photon Generation from Nanowire Quantum Dots
(University of Waterloo, 2026-06-01) Gangopadhyay, Sayan
Quantum photonic technologies require bright, deterministic sources of entangled photons. Applications such as quantum networks further demand high single-photon indistinguishability, a key requirement for quantum interference in protocols such as entanglement swapping. Semiconductor nanowire quantum dots are among the brightest on-demand sources of high-fidelity entangled photon pairs generated through the biexciton-exciton cascade. The highest values of indistinguishability from quantum dot sources are achieved using resonant excitation. However, implementing resonant excitation in nanowire quantum dots has remained a long-standing challenge due to the stringent laser suppression required in nanowire geometries. In this thesis, we establish a robust technique for resonant excitation of a quantum dot embedded in a tapered single-mode nanowire waveguide. By engineering mode matching between the incident laser and the nanowire-guided mode, efficient coupling to and from the quantum dot is achieved while simultaneously suppressing back-scattered laser light. This approach enables the realization of a one-dimensional atom, in which coherent single-photon reflection is observed. Furthermore, by combining mode matching with polarization-based rejection, we achieve laser suppression on the order of 10⁶, enabling the generation of single photons under pulsed resonant excitation. Under these conditions, we observe clear Rabi oscillations and strong antibunching in second-order correlation measurements. Two-photon interference measurements yield an indistinguishability of 0.41 at a temporal separation of 12.5 ns, indicating that residual decoherence mechanisms, such as charge noise, limit performance in the current devices. Motivated by this limitation, we propose a broadband nanowire cavity based on a quasi-bound state in the continuum (quasi-BIC) design. This cavity leverages interference between two resonances to simultaneously achieve a Purcell enhancement of 17, high extraction efficiency of 74%, and a directional emission with an 88% Gaussian overlap over a spectral bandwidth of 4 nm, sufficient to enhance both photons in the biexciton–exciton cascade. These results establish resonant excitation in nanowire quantum dots as a viable route toward generating indistinguishable single photons, while highlighting the role of residual decoherence mechanisms that currently limit performance. The proposed quasi-BIC cavity design further provides a pathway toward enhancing emission rates and photon indistinguishability in this platform. Furthermore, the realization of a one-dimensional atom in a nanowire platform opens new opportunities for exploring waveguide quantum electrodynamics, including emitter-mediated photon-photon interactions.
Enclosure to Enclosure: from Temagami Forest to the CMHC Post-War House
(University of Waterloo, 2026-06-01) Zhou, Victoria
Approximately two-thirds of Ontario, Canada is comprised of forests—making up more than one-fifth of all forests in Canada—and 90 percent of it is situated on public Crown Land. While forests are ecological lands, they are also geopolitically delineated territories and administrated provincially. Within Ontario’s system of administrated forests, Temagami Forest distinguishes itself as a site of settler-colonial experiments in property, territory, and forestry. Although the land is public, the woods are entangled with the practices of capitalist industry. Softwood dimensional lumber—colloquially referred to as wood studs or 2x4s—is the product of such capitalist interventions in the forest. The colonial impact of this material extends beyond the forest; it is essential to the development and construction of the single-family stick-frame house. This typology is implicitly associated with democracy, self-determination, and social mobility, remaining deeply tied to the institution of private property in the nation-state of Canada and the United States. Through review of literature, assembling an archive of present and historical maps, and site visits, I weave together a narrative which bridges different landscapes and scales of wood extraction. This thesis explores the use of surveying and mapping, forestry and logging administration systems, stick-frame construction methods, and the nationally distributed housing design catalogue as four mechanisms that link forested landscapes in Ontario to the dominant culture of single-family stick-frame house ownership. Throughout are also speculative pencil drawings that rethink the standard representational strategies for 2x4s and wood. I use the concept of assemblage to understand the cooperation between material and cultural aspects of dimensional lumber. Forests are not readily available “supplies” that fill the “demand” for domestic property; there are legal, cultural, material, and architectural mechanisms which transform woodlands into fungible wood prisms into stick-frame houses. The 2x4 as a narrative device to explore how the institution of property emerges across forests and stick-frame houses. Through the duality of the word “enclosure” I demonstrate how logics of capitalism enclose commons across different scales.
Investigation of Skin Epithelial Innate Immune Barrier Functions using a Xenopus laevis Cell Line
(University of Waterloo, 2026-06-01) Chhabra, Prakriti
Frog skin functions as both a physical and immunological barrier to the external environment. In addition to protection by antimicrobial peptides (AMPs) present at the skin surface, epithelial cells recognize pathogen-associated molecular patterns and coordinate local immune responses. While amphibian AMPs are well known for antimicrobial activity, their roles in regulating epithelial immunity and barrier function remain unclear, partly due to limited in vitro models. The objectives of this thesis were to use the Xenopus laevis epithelial-like cell line Xela DS2 to (1) explore whether two X. laevis AMPs, magainin II and PGLa, exert immunomodulatory effects on epithelial cells, and (2) develop an in vitro epithelial barrier model for studying anuran skin immunity. To support the first objective, Xela DS2 were examined for the presence of magainin II and PGLa transcripts and treated with AMPs or a synthetic analogue of viral double stranded RNA [poly(I:C)] to determine non-cytotoxic concentrations. Xela DS2 demonstrated little to no transcription of target AMPs. Magainin II or PGLa at concentrations ≥32 µM, or poly(I:C) at concentrations above 250 ng/mL, were cytotoxic to Xela DS2, and established non-cytotoxic concentrations for use in experiments. Initial attempts to study potential immunomodulatory activity of AMPs were unsuccessful due to an unanticipated cellular response to the vehicle control. In parallel, an air-liquid interface model was established, where cells formed highly restrictive barriers with TEER values >10,000 Ω·cm² prior to airlift and maintained above functional thresholds for 6-8 days post airlift. Barrier formation depended on seeding density and passage number, with lower-passage cells performing better. Collagen coating was not essential, and use of a mammalian ALI supplement appeared detrimental. Barrier integrity was supported by organized ZO-1 localization and reduced paracellular permeability. Together, these findings establish Xela DS2 as a platform to study epithelial barrier function, AMP activity, and host-pathogen interactions in frog skin.
A "Chronic Complainer's" Guide to the Hystericizing of Fibromyalgia
(University of Waterloo, 2026-06-01) Johnson, Melissa N.P.
In the early 2000s, a study set out to test the popular belief that fibromyalgia is “factitiously driven by misinformed media reports and an overly liberal disability compensation system” (White & Thompson 2003). Although the authors disproved this hypothesis, their findings nonetheless provoked a series of editorials that reinscribed these suspicions and were published alongside the original study in the Journal of Rheumatology. Working within feminist disability studies and using discourse analysis as a method, I examine how these editorials engage in what Anna Mollow (2014) identifies as the routine hystericization of conditions with medically unexplained symptoms. I argue that these texts mobilize an all-too common narrative of “secondary gain” whereby patients, particularly women, are cast as “chronic complainers” and suspected of feigning or exaggerating illness for some interpersonal or economic advantage. I position these representations within a longer genealogical continuum of poorly understood conditions historically framed as psychosomatic to demonstrate how these editorials recycle and repackage gendered characterizations of nineteenth century nervous disorders and apply them to their (mis)representation of fibromyalgia. By framing fibromyalgia in this way, the authors perpetuate harmful narratives that I argue contribute to the oppression of those of us with misunderstood and invisibilized illnesses. Drawing on principles of disability justice, I extend this analysis by situating these suspicions toward feminized and unverifiable illness within a broader moral economy that ties human worth to value-laden notions of citizenship, productivity, and independence. In this schema, those perceived as “unproductive” members of society with no “legitimate” claim to illness are positioned as unworthy burdens on the healthcare system and undeserving of social supports. I argue that these pejorative framings reproduce eugenic logics that construct dependency as a social and economic threat, obscuring the fundamentally interdependent nature of human life and legitimizing the restriction of care and support to those deemed undeserving. Ultimately, this dissertation traces how skepticism toward fibromyalgia is embedded in broader historical narratives and cultural ideologies that continue to shape access to care, structuring whose pain is believed, whose suffering is recognized as worthy of care, and which lives are valued and sustained.
From User-Plane Telemetry to Closed-Loop Control: NWDAF-Enabled Automation in 5G Networks
(University of Waterloo, 2026-06-01) Shafiei Ardestani, Fatemeh
The fifth generation of cellular technology (5G) delivers faster speeds, lower latency, and improved network service alongside support for a large number of users and a diverse range of verticals. This brings increased complexity to network control and management, making closed-loop automation essential. In response, the 3rd Generation Partnership Project (3GPP) introduced the Network Data Analytics Function (NWDAF) to streamline network monitoring by collecting, analyzing, and providing insights from network data. While prior research has focused mainly on isolated applications of machine learning within NWDAF, critical aspects such as standardized data collection, analytics integration in closed-loop automation, and end-to-end system evaluation have received limited attention. This work addresses existing gaps by presenting a practical implementation of NWDAF and its integration with leading open-source 5G core network solution. We designed a closed-loop-enabled system that can collect UE communication data from the User Plane Function (UPF) via the UPF Event Exposure Service (UPF EES), and provision different machine learning models based on the analytics use case using our ML Model Provision Service integrated with MLflow. Additionally, we implemented user-plane token-bucket-based rate policing to enable fine-grained traffic enforcement actions. We showed that, with one active subscriber to the Event Exposure Service, UPF increases the one-way delay by at most 0.11 ms and the CPU usage by less than 6.5\% compared to the baseline UPF across different data rates. For memory usage, we observed only a small constant overhead that was independent of throughput. We also demonstrated the scalability of our UPF EES by increasing the number of active UEs and examining its effect on the UPF’s CPU and memory utilization. Additionally, we investigated the resource usage of different NWDAF components across different reporting intervals, showing that the ML Model Provision Service is the most resource-intensive component of the NWDAF. Building on this framework, we instantiated two closed-loop use cases: (i) anomaly detection and mitigation, in which we use graph-based features derived from UPF telemetry to detect bot behavior and ban anomalous User Equipments (UEs) from the network, and (ii) dynamic QoS adaptation, in which we adjust the traffic rate of UEs based on the level of congestion using a confidence-driven heuristic that maps congestion levels to proportional rate adjustments. We demonstrate the effectiveness of each closed-loop system and identify the associated trade-off in use case (i), namely between data collection interval and detection latency. In use case (ii), we show that the proposed mechanism can protect guaranteed flows through runtime rate adaptation.

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