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Whirl Flutter Investigation for Rotor Discs and Two-Bladed Systems
Get PDFThis thesis details the investigation of flutter and divergence instabilities of rotor shafts with two or more blades, developing a detailed computational tool that can determine the corresponding stability boundaries. This development addresses the propeller whirl flutter phenomenon by exploring various physical principles and operational parameters using quasisteady theory, and developing the dynamic equations of motion. The computational tool provides a detailed framework for predicting and analyzing propeller whirl flutter behaviour in different operational scenarios. Additionally, this study focuses on analyzing the dynamic and static stability characteristics of the propeller–pylon–wing system while deliberately neglecting the structural elasticity of the supporting wing. The propeller and pylon dynamics, which may include flexibility depending on the modeling approach, are retained to capture key aeroelastic interactions. This simplification enables a more focused investigation of whirl flutter behaviour by isolating the influence of propeller parameters and mounting configurations without the added complexity introduced by wing flexibility
A Multivariate Characterization Shows that Bilingualism Predicts Attention
Get PDFA common, yet controversial, claim is that bilingualism confers domain-general cognitive processing benefits. Many studies support this claim, but others do not. Multiple sources of heterogeneity—including how bilingualism and cognition are conceived and measured—complicate attempts to synthesize the literature. Language questionnaires have brought some consistency to how bilingualism is measured, but the extent to which they measure common constructs is unclear. In this study, I aimed to assess the overlap between questionnaires and determine their ability to predict cognitive performance. I administered seven questionnaires and conducted a multiple factor analysis to find factors that capture variance across questionnaires. Then, I used partial least squares path modeling to determine whether these factors predict cognitive performance on four tasks measuring task switching and inhibition. Results support the adaptation theory hypothesis that bilingualism hones a low-level executive attention process that explains covariance in task performance
Exploring the Reproductive Ecology and Glochidia-Host Relationships of Freshwater Mussels in a Canadian Context
Get PDFUnionid mussels have a unique lifecycle in which their larval phase must successfully attach to a suitable host (usually a fish) in order to metamorphose into their juvenile phase. Their hosts serve a dual purpose of providing nutrition and dispersing offspring. This thesis compiled current knowledge via a literature review on the larval hosts of all 55 unionid species in Canada, providing an updated library of unionid-host interactions and highlighting needs for future studies. Furthermore, it generated new knowledge on the reproductive ecology of the Eastern Elliptio (Elliptio complanata), the most abundant unionid species in Canada. This includes novel data for the reproductive timing of this species in Canada as well as some preliminary investigation on the impact of an invasive piscivore introduction on unionid reproduction. Collectively, this body of work provides valuable information that can be used by researchers and managers to conduct future research or inform conservation efforts
Learning Safe and Efficient Driving Policy with Proximal Policy Optimization (PPO) using Rule-Based Rewards and Real-World Offline Data
Get PDFDesigning an effective reward function is essential yet challenging for developing robust autonomous driving policies. Many existing approaches focus on specific tasks or rely on implicit rule learning, which may hinder generalization. This work introduces explicit, rule-based reward functions to promote safe and compliant driving behavior, such as maintaining a safe distance from leading vehicles and adjusting speed based on traffic context. The policy is trained using a real-world offline dataset and optimized with the Proximal Policy Optimization algorithm (PPO). Two state representations are evaluated: a rasterized bird’s-eye view with a convolutional neural network (CNN), and a vectorized format processed by a graph-attention network. Simulation results show that the CNN-based model performs better, achieving a safe distance ratio of 0.96 in light traffic conditions—compared to 0.90 with a baseline—and a speed error of 1.875 m/s. These results demonstrate the reward functions’ effectiveness and highlight areas for further improvement
A Community-Scale Perspective on the Diversification of Tetrapod Ecology and Botanical Turnover based on the Pennsylvanian of the Maritimes Basin, Atlantic Canada
Get PDFModern terrestrial communities are complex and diverse, their assembly being influenced by a litany of abiotic and biotic drivers and constraints. Some of the most basic factors that govern their structure and function are thought to have been established in the Pennsylvanian (~323-299 Ma), as the ecological roles of terrestrial tetrapods rapidly diversified. At a global scale, the expansion of tetrapod ecology occurred roughly in concert with major disruption in plant community composition, leading some to propose a causal link between the two phenomena. My dissertation focuses on addressing whether plant community disruption and functional diversification of tetrapods occurred in concert at the community scale, using the Lower-Middle Pennsylvanian Maritimes Basin of Atlantic Canada as a case study. For this dissertation, I use body mass and diet as the variables through which I study tetrapod functional diversity. In the course of this investigation, I ask three foundational questions about community structure developments through the Lower-Middle Pennsylvanian of the Maritimes Basin: Did plant community assembly significantly change? Was there a significant shift in the body mass distributions of tetrapods? Was there any expansion in the dietary niches occupied by tetrapods? I show that two significant floral turnovers occurred during the studied interval, including one which likely involved a major disruption in community assembly rules, and that these are roughly concurrent with similar plant community disruption events from elsewhere in Euramerica. I expand upon a method of body mass estimation based on the dimensions of vertebral centra to show that body mass distributions did not change significantly through the studied interval. My body mass results also demonstrate that taphonomic biases may also explain the majority of differentiation between Pennsylvanian fossil body mass distributions and those of modern tropical estuarine environments. Lastly, I use a combination of both tooth morphology and biogeochemistry to make inferences of tetrapod diet, showing no conclusive evidence of expansion in tetrapod dietary ecology. Put together, the results of my dissertation reject the hypothesis that ecological diversification of tetrapods was a response to plant community disruption, and improve our understanding of the foundational processes driving terrestrial community structure
Becoming “Lesbian” in TV land: Television as an Interlocutor of Queer Consciousness & Community
Get PDFThis research interrogates questions of queer consciousness and queer community as influenced by television, or other visual media formats. Utilizing intersectional queer perspectives, I draw on José E. Muñoz’s queer longing and queer utopia as the basis of my theoretical framework. Extrapolating from queer phenomenology as my methodological approach, I conducted four semi-structured interviews. All participants identified as lesbian, lived in Ottawa, Ontario, were between ages 18 and 25, and spoke English. Three main themes were found in the interviews detailing the relationship between television and queer identity: availability and access, finding community in adulthood, and a lingering absence in representation. The interviews outlined several failures of television to represent queerness in accurate and non-normative ways. The narrators confirmed that television, alongside other media formats, is influential in queer subjectivity and community formation