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    Considerations for the Design of a UD-NCF Composite Energy Absorbing Structure for Frontal and Oblique Crush Loading
    (University of Waterloo, 2026-03-27) Huang, Ningwei
    Growing concerns regarding climate change have prompted national and international regulatory agencies to implement increasingly strict regulations aimed at reducing carbon dioxide (CO₂) emissions. These regulations have driven automotive manufacturers to place greater emphasis on sustainability and improved fuel efficiency in vehicle development. Owing to their high specific strength and stiffness, and superior energy absorption capability, carbon fiber-reinforced plastic (CFRP) composites are considered promising lightweight materials for vehicle frontal crash structures. Their widespread adoption in the automotive industry was previously limited due to high manufacturing costs and challenges in accurately predicting their response under impact loading. However, CFRP components manufactured via high-pressure resin transfer (HP-RTM) with highly reactive resins enable reduced production cycle times and, thus, adoption in automotive structures. Unidirectional non-crimp fabric (UD-NCF) reinforcements offer further advantages, including reduced manufacturing costs, high in-plane mechanical properties, and enhanced design flexibility. To meet safety requirements, vehicle structures must be designed to effectively absorb energy under various impact conditions to protect the occupants from injury. Previous studies have primarily focused on evaluating the impact performance and energy absorption characteristics of CFRP composite components under axial loading. Few studies have investigated the effects of oblique loading on the crush performance of composite structures and they are mainly restricted to closed-profile tubes, which are difficult to manufacture using liquid composite molding technologies such as HP-RTM. To date, the crush performance of UD-NCF composite components under oblique loading has not been examined. Therefore, this thesis aims to design a UD-NCF composite frontal crush component capable of achieving progressive energy absorption under both axial and 30-degree oblique loading conditions. The design is limited to adhesively bonded double channel components as they can be readily fabricated using HP-RTM processes, while the scope of the study is intended to address several considerations for this design concept. Firstly, the energy absorption capability and failure modes of UD-NCF composite single and double hat channel specimens with [0/±45/90]s and [±45/02]s stacking sequences under quasi-static oblique (i.e., 30-degree off-axis) loading were experimentally investigated to provide data for validation of an impact simulation model. For the single hat channel, specimens with a [0/±45/90]s layup achieved 0.78% higher total energy absorption and 11.2% higher specific energy absorption (SEA) than specimens with a [±45/02]s layup. Specimens with both stacking sequences exhibited lamina bending during the initial crushing stage, followed by premature failure. For the adhesively bonded double hat channel, the [±45/02]s specimens yielded 6.4% higher total energy absorption and 9.95% higher SEA than the [0/±45/90]s specimens due to their higher axial stiffness. The double hat channel configuration demonstrated significant improved crush stability than single hat channels throughout the loading process, regardless of stacking sequences. Secondly, computer-aided engineering (CAE) impact simulation models were developed to predict the energy absorption capability of UD-NCF composite channels under quasi-static and dynamic crushing conditions. Simulation models for both single and double hat channel specimens were validated against the performed oblique crushing experiments and exiting axial crush test data from the literature. The results showed that the CAE impact simulation model accurately predicted the crush performance for both single and double hat channel specimens under dynamic axial loading, while having reduced accuracy under quasi-static loading conditions. Lastly, the influence of channel cross-sectional geometry and laminate stacking sequence on energy absorpiton capacility of the UD-NCF composite channels under dynamic oblique loading was investigated using the validated simlation models. Single and adhesively bonded double channels with five distinct geometries and six stacking sequences were considered in the study. All single channel geometries with a [0/±45/90]s stacking sequence exhibited similar SEA, which was the case for both axial and oblique dynamic loading. Under oblique loading, all double channel geometries with [0/±45/90]s and [0/±45/90/±30]s stacking sequences exhibited premature failure. The hat channel geometry consistently demonstrated stable progressive crushing, whereas the other geometries considered showed greater sensitivity to stacking sequence and loading angle. Across all stacking sequences considered, only channels with a [±45/02]s stacking sequence achieved stable crushing under both axial and oblique loading, while also providing the highest SEA values. The double hat channel with the [±45/02]s stacking sequence was identified as the most promising configuration for subsequent frontal crush structure design. Overall, this represents the first comprehensive assessment of the crush performance of UD-NCF composite components under oblique loading conditions. These findings contribute practical design guidelines for the future development of lightweight UD-NCF frontal crush structures in vehicles.
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    From Asymptotic to Finite-Size Security in Decoy-State Quantum Key Distribution
    (University of Waterloo, 2026-03-24) Kamin, Lars
    Quantum Key Distribution (QKD) promises information-theoretic security, yet bridging the gap between theoretical proofs and practical implementations, specifically those operating with finite resources and imperfect devices against general coherent attacks, remains a critical challenge. This thesis develops a spectrum of efficient security proof techniques within the composable security framework, calculating key rates for both fixed- and variable-length protocols while accounting for realistic imperfections. We begin by addressing detection setups through an extension of a squashing map, the flag-state squasher, used for reducing the infinite-dimensional Hilbert spaces of optical elements to finite dimensions. This extension accommodates arbitrary passive linear optical setups while allowing for the inclusion of detection inefficiencies and dark counts in the security analysis. Subsequently, we advance the analysis of decoy-state protocols and introduce two major improvements. First, we reformulate the decoy-state analysis to recover no-decoy key rates, tightening the optimization. Second, we derive a unified framework that performs the key rate optimization and decoy analysis in a single step. This enables the bounding of the relevant entropies with arbitrary precision in the finite-size regime and successfully recovers the Devetak-Winter formula in the asymptotic limit. Furthermore, we improve the security analysis for generic QKD protocols against independent and identically distributed (IID) collective attacks. Our refined analysis yields finite-size corrections proportional to detected rather than transmitted signals and, by developing sharper concentration inequalities, achieves significantly improved finite-size scaling. Finally, leveraging the marginal constrained entropy accumulation theorem (MEAT), we establish a flexible numerical Rényi security framework against coherent attacks for both fixed- and variable-length protocols. This approach consistently outperforms existing reference proof techniques, including those based on entropic uncertainty relations, providing significantly higher key rates for both qubit and practically relevant decoy-state protocols. Moreover, we present finite-size key rates for generic QKD protocols accounting for realistic intensity and phase imperfections. Overall, this thesis provides the necessary theoretical framework to bridge the gap between idealized models and experimental reality, offering a scalable path toward secure quantum communication under realistic conditions, as demonstrated by the application of these techniques in experimental collaborations.
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    [UN]PREDICTABLE SUBURBIA: An Exploration of Rules, Representation, & Rigidity
    (University of Waterloo, 2026-03-23) Ma, Nhuy Cindy
    Suburbia presents itself as an uninspiring, homogenous landscape, where our personal lot lines define our boundaries of care. Characterized by detached houses with private gardens and fences, the controlled and uniform design of these spaces, which are rooted in historical policy, greatly limits potential for social and spatial complexity. As experts in charge of understanding the rules, guidelines, and best practices that dictate the design of urban zones, we often confront this entrenched reality, built through decades of regulatory frameworks. This thesis anchors itself within urbanism, exploring the boundaries and intersections between rules, guidelines, and suggestions. It tests various design methodologies that work within established frameworks of control to subvert suburban monotony and enable greater agency and complexity. Rather than rejecting urban rules outright, the research examines how both control and agency can coexist to produce varied and unexpected outcomes within a suburban context. Drawing upon the work of Michael Sorkin’s Local Code, Alex Lehnerer’s Grand Urban Rules, Ekim Tan’s Play the City, and Archizoom’s No Stop City, the thesis develops a novel, iterative design methodology combining analytical study with tests of agency and complexity. This method critically examines and reimagines urban rules through design experimentation aimed at uncovering new possibilities for suburban transformation. This thesis offers both a theoretical critique of suburban spatial and social homogeneity, as well as a practical methodology for designers to engage with and reshape suburban environments. By reframing suburbia as a space of controlled agency, this work encourages architectural and urban innovation within traditionally rigid, mono-programmatic landscapes. Thus, suburbia is positioned not as a fixed condition, but rather a mutable environment capable of supporting complexity and social diversity.
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    Measuring the Weak Gravitational Lensing Signal from Cosmic Voids
    (University of Waterloo, 2026-03-23) Martin, Hunter
    The field of cosmology is currently in an era principally focused on statistical precision. To achieve greater precision, deeper and wider surveys are actively being developed and conducted to gather more and more information about the surrounding cosmos. Alternatively, there are efforts to develop new statistical probes to better utilize currently-existing data to obtain tighter constraints. Cosmic voids, as vast underdense regions, then represent an ideal candidate to complement the statistical information already extracted from the opposite density extremes: massive luminous galaxies and galaxy clusters. Voids have already seen some success in constraining cosmology through probes like the void size function and void-galaxy cross-correlations. This thesis introduces the matter distribution within cosmic voids as measured by weak gravitational lensing as a new probe that is significantly detectable within current and future data sets. The goal of this demonstration is to justify future efforts in extracting the cosmological information from this newfound signal. For data currently available, we make use of the large overlap of the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey (BOSS) and the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS). We measure void lensing around BOSS voids and find that we can detect the signal at 6.2 sigma significance, the most significant detection from spectroscopically-identified voids to date. We additionally are able to significantly detect differences in the void profile with void size between the larger half and smaller half of the void catalogue at 2.3 sigma. To help perform this measurement, we present and validate a novel method for computing the Gaussian component of the conventional weak lensing covariance, adapted for use with void studies. Comparing the void profile to a measurement of the void-galaxy cross-correlation to test the linearity of the relationship between mass and light, we find good visual agreement between the two, and a galaxy bias factor of 2.45 pm 0.36, consistent with other works. We additionally assist in future developments of the UNIONS data by running quality control tests for the future photometric redshift data sets. These future releases will provide additional data to make these detections stronger. For future data, we use the Flagship simulation of the Euclid survey to simulate the expected data from the Euclid VISible imager (VIS) and Near-Infrared Spectrometer and Photometer (NISP) instruments across an octant of the sky. This octant then roughly corresponds to an equivalent area of the planned second data release of the survey. We extend the methodology and covariance model to a lensing tomography setup by binning voids and sources along the line of sight. We then stack information along source bins. From this, we are able to detect the void lensing profiles with 12 sigma, 11 sigma, 7.1 sigma, and 4.7 sigma significance across the four different void redshift bins. Scaling the most significant result to the expected areas for the first and final data releases, we get 6.9 sigma and 21 sigma respectively. We additionally find a 4.4 sigma difference between the lensing profiles of the smallest voids and the largest voids.
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    Communities on-Track: A Spatial Reprogramming of Regional Railway Stations for Interinstitutional and Civic Exchange
    (University of Waterloo, 2026-03-23) Yuen, Hoi Man Neli
    As our society grows more mobile, public transport is becoming an increasingly important alternative to private transport. In Ontario, this shift is compounded by the decentralization of post-secondary education, accelerated by the expansion of satellite campuses and changing patterns of study following the COVID-19 pandemic. As a result, post-secondary students are becoming more reliant on public transport than ever before. However, in the North American context, public transit is often still seen as secondary to private transit, resulting in stations which are underutilized, and underperform socially and functionally. This work addresses the site of the regional railway station. Having once been central to the socio-economic development of towns and cities, this role has since diminished as the result of a fixation on network connectivity alone. In response, this thesis leverages the transformational developments in both sectors to propose a network-based strategy, where public transit and post-secondary systems are conceived of and developed in conjunction. By positioning stations as sites of intersection between mobility and knowledge production, the project frames them as spaces for civic exchange, where the rhythms of travel create opportunities for collective encounter. The implementation of design interventions at three stations along GO Transit’s Kitchener Line demonstrates how context-specific programming can reactivate stations as civic anchors. Together, they offer a distributed model for linking mobility, learning, and community across the regional railway network, repositioning railway infrastructure as an active component of social life rather than a purely functional system.