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    Validated Computational Tonal Noise Prediction for Airfoils with a Laminar Separation Bubble
    (American Institute of Aeronautics and Astronautics, Inc., 2026) Zilstra, Alison; Johnson, David A.
    A computational aeroacoustic study of a laminar separation bubble (LSB) in close proximity to the airfoil trailing edge (TE) examines the aerodynamic source of the generated tonal noise and the influence of acoustic feedback on tonal noise amplification. Incompressible wall-resolved large-eddy simulation (LES) and the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy are applied to the SD 7037 airfoil at the Reynolds number, 𝑅𝑒, of 41000. At 1 deg angle of attack (AOA), the FW-H acoustic analogy accurately predicts the tonal noise frequency, which originates from the Kelvin–Helmholtz (K-H) rolls in the LSB shedding past the airfoil TE, and a secondary tone occurs due to intermittent spanwise breakdown of the K-H rolls. An estimation of the interference between the TE acoustic feedback and the recently identified LSB pressure feedback shows that destructive interference at 3 deg AOA lowers the tonal noise, while constructive interference at 1 and 5 deg AOA amplifies the tonal noise. This study of the tonal noise generated by an LSB shows that destructive interference of the LSB and TE feedback mechanisms can be exploited as a mechanism of active tonal noise control for airfoils operating at low 𝑅𝑒.
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    Implementation Techniques for Lexical Effect Handlers
    (University of Waterloo, 2026-08-10) Ma, Cong
    Effect handlers generalize exception handling to support control-flow patterns including coroutines, cooperative multitasking, and nondeterminism. Recent work advocates for lexically scoped handlers, which restore abstraction safety and enable modular reasoning: a handler is a lexically scoped capability, and an effect can be raised only to a handler whose capability is in scope. However, prior implementations of lexical effect handlers suffer from inefficiencies that could hinder their adoption in practice. This thesis shows that the static character that makes lexical scoping safe is also what makes it efficient to implement. It develops this insight into three complementary compilation techniques, embodied in our language Lexa; each technique is made precise by a formal model, proven correct, and realized in the Lexa compiler. Direct Lexa identifies each handler with the stack address where it is installed, so a raise jumps directly to its handler, without any search. Zone Lexa extends the address-based strategy to multishot resumptions by virtualizing handler identities through a software memory-management unit. Zero Lexa serves infrequent effects such as exceptions: it avoids the cost of passing down any run-time handler identity, and instead walks the stack using the static handler provenance information when an effect is raised, so effect-free execution pays nothing. A single program can choose among the three techniques per effect, matching each declared effect to its expected usage. Together, these techniques demonstrate that lexical effect handlers can be implemented efficiently. Effect handlers can be both safe and fast.
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    Galaxy evolution across the Virgo cluster environment
    (University of Waterloo, 2026-08-07) Morgan, Cameron Robert
    In this thesis, I present three studies of the properties of galaxies in the Virgo cluster with the goal of providing new insights into how we can measure the effects of the cluster environment on these member galaxies. Throughout this work, I move from analyzing integrated quantities of galaxies toward studying galaxy star formation on a spatially-resolved scale. First, I analyze deep stellar mass functions of galaxies in the Virgo cluster. I split these stellar mass functions according to star formation rate and region within the cluster. I find that the quenched fractions remain high across the cluster, including in the infall region, and especially at low stellar masses. Additionally, the shapes of the mass functions are mostly independent of position within the cluster. Using a simple model of infalling and backsplash galaxy populations, I show that the quenched fractions seen in the cluster outskirts require unrealistically high backsplash fractions, implying that galaxies are being pre-processed outside of the main cluster and are often already quenched upon first infall. The second section of this thesis focuses on quantifying the edges of star-forming disks as a means to analyze truncation and outside-in quenching. I develop a novel method for measuring disk truncation that takes advantage of the depth and spatially-resolved nature of the VESTIGE Hα data. This method involves constructing radial sSFR profiles and identifying the turn-off point where star formation drops off. I compare this edge of the star-forming disk with a measure of the expected size based on normal star-forming galaxies, which gives a measure of the degree of truncation. Ultimately, I find that moderately-severely truncated disks are ubiquitous across the cluster environment, and show only mild correlations with parameters such as stellar mass, distance from the SFMS, and HI-deficiency. I invoke toy models of RPS and starvation to show the effects that each of these mechanisms has on disk truncation. While RPS can rapidly truncate the star-forming disk, it is only particularly effective toward the cluster centre. Starvation can slowly truncate disks much earlier by cutting off a galaxy's supply of fresh gas -- as the gas density decreases, the outer part of the disk falls below the threshold necessary to sustain star formation first, causing a slow outside-in quenching. This again highlights the need for pre-processing to explain quenching in the Virgo environment, and indicates a ``slow-then-rapid'' quenching sequence. Finally, I take advantage of the spatially-resolved and multi-wavelength data available for Virgo cluster galaxies to map signatures of quenching on more local scales. I do this by empirically calculating SFRs based on both Hα and FUV fluxes, thus giving me SFRs on both ~10 and ~100 Myr timescales. Comparing the two helps to identify regions where rapid quenching is occurring. I perform spatially resolved SED fitting on a sample of Virgo galaxies using CIGALE which allows me to map out galaxy parameters. Combining the SED fitting results with emission line ratios from MaNGA, I derive corrections based on dust, NII contamination (in the Hα) and pAGB contribution to the FUV before converting the respective fluxes to SFRs. Taking the ratio of SFRha and SFRfuv allows me to visually identify interesting features in these galaxies. I identify two key features: lopsidedness in the distribution of SFRha/SFRfuv, and outer disk truncation. I quantify these metrics, and find that while a few galaxies that have strong gas asymmetries and have been identified as RPS candidates have a high degree of lopsidedness, there are no strong correlations with other galaxy parameters. I discuss the possibility that these metrics are unique signatures of processes like RPS at certain stages, though drawing strong conclusions about their nature proves difficult. I end off with future perspectives, based on my own work with the CASTOR and GIRMOS science teams, the broader context of new instrumentation and analysis tools, and my own goals for the coming years as I seek to continue work into the study of galaxy evolution. I look forward to pursuing studies with new data, exploring new redshift ranges and galaxy environments, and looking to continue developing novel techniques to help make inferences about galaxies in the broad context of understanding our Universe.
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    Drawing benefits memory and comprehension by establishing and strengthening the link between verbal and visual percepts
    (University of Waterloo, 2026-08-07) Tran, Sophia
    Researchers have long been interested in identifying ways to enhance both the quantity and quality of human memory, and the mechanisms underlying their benefit. The use of drawing as an encoding technique has been shown to reliably improve memory for lists of words, definitions of terms, and autobiographical events. What remains unexplored is how the magnitude of the benefit from drawing compares to that from other encoding techniques, and its mechanism of action. In Experiment 1, I showed that drawing, writing, and reading aloud as encoding techniques yielded better memory than silently reading words, with drawing leading to the largest boost. Importantly, age differences in memory emerged only when drawing was used as the encoding strategy, in line with previously reported age-related deficits in generating imagery, or integrating it with motoric processes. Despite this, concrete relative to abstract words that were drawn during encoding were better retained, demonstrating a stable benefit of visuo-spatial representation, regardless of age. In Experiment 2, I assessed the extent to which personally generating one’s own production was critical to the observed memory benefit. Replicating Experiment 1, drawing at encoding benefitted memory more than writing or reading words. This occurred regardless of whether it was performed or observed in-person or online. In line with common-coding-theory this finding suggests that perceiving an action activates the same motoric processes in the brain as performing it. However, the magnitude of the drawing benefit was greatest when performed rather than observed, suggesting an additional role of personal relevance in modulating the drawing benefit. In Experiment 3, I examined whether repetition by tracing one’s initial drawing, or generating multiple novel related ones, differentially benefitted memory. The former enhanced free recall of target words more than the latter. This suggests that establishing a strong visual percept underlies drawing’s benefit to memory. Finally, in Experiment 4, I assessed the utility of drawing as a cognitive tool in educational contexts. Drawing and paraphrasing of definitions of novel academic terms, during encoding, resulted in better performance on a multiple-choice test of concept comprehension, relative to silently reading. Results suggest that techniques that invoke re-representation of the to-be-remembered text into another format, be it into a picture (drawing) or personally relevant summary (paraphrasing), are particularly effective at improving cognitive task performance. The experiments in this dissertation suggest that a critical component of how drawing improves memory and comprehension is the linking of verbal information to concrete visual referents, which results in more easily retrievable representations.
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    Bidirectional insights between classical and quantum causal inference
    (University of Waterloo, 2026-08-07) Maciel Ansanelli, Marina
    Causal inference is a sub-area of statistics that investigates the causal explanations underlying observed data. The last decade has seen growing recognition of its applications to quantum physics, which include the use of causal inference to certify quantumness through violations of Bell-like inequalities. This connection places quantum physicists in a unique position to contribute to classical causal inference by addressing open problems whose solutions benefit both fields. This thesis highlights this bidirectional interplay of fields, presenting both the study of foundational problems in classical causal inference from the perspective of quantum physics and the application of these results to quantum research. An important problem in causal inference is attesting when two causal structures are in principle indistinguishable from data obtained under a given probing scheme on the visible variables. For example, passive observations on two variables cannot distinguish between a direct causal relation and a shared latent common cause. However, they {\em can} be distinguished by interventional probing schemes. The first question we address here is which causal structures remain indistinguishable even under the most informative interventional probing schemes. We derive a necessary and sufficient condition for such indistinguishability. We then consider the same question under access to passive observations only, compiling all known sufficient rules for indistinguishability and applying them to causal structures with three and four visible nodes, though a complete characterization remains open. Then, we extend these results to scenarios involving selection bias. The works described above also help identify which causal structures impose nontrivial inequality constraints on their classically realizable distributions; an example is the Bell causal structure, that imposes Bell inequalities. This has particular interest for quantum physicists, because inequality constraints are a prerequisite for a causal structure to have a quantum-classical gap (QC gap), that is, for it to explain more distributions when its latent nodes are associated with quantum systems than when its latent nodes are associated with classical variables. This is important because, when we know that a phenomenon is governed by a causal structure that presents a QC gap, observing a probability distribution over the observed variables that cannot be explained using classical latent variables in that structure certifies that the phenomenon involves genuine nonclassicality. Thus, after identifying which causal structures could potentially exhibit a QC gap, we investigate which actually do. Using techniques developed here, we show that hundreds of new causal structures have a QC gap, while previously only around a dozen examples were known.