Waterloo Library Journal Publishing Service (University of Waterloo, Canada)
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2023 research outputs found
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Design of porous architectures in laser powder bed fusion: effect of hatch spacing and rotation angle on density and pore morphology
No full textBone is a complex and hierarchical structure with the ability to provide extensive structural support to the body while also being lightweight for ease of motion. Bone can be damaged due to injury or illness, requiring the need for an orthopedic implant to enhance function, to provide structure and to encourage the growth of new bone. A challenge with current metal orthopedic implants is stress shielding, where there is a mismatch of mechanical moduli between the implant and human bone. When designing implants, it is important to tailor the mechanical response of the implant to natural bone to avoid stress shielding. This research explores a new method for implant design, incorporating pores stochastically using laser powder bed fusion (PBF-LB). This type of porosity is introduced into a solid metal part during printing by altering process parameters in PBF-LB. The density and pore morphology are dictated by the hatch spacing (100 – 500 µm) and rotation angle (60° and 67°). These structures were printed in Ti-6Al-4V. The effects of the hatch spacing and rotation angle on melt pool morphology and porosity were investigated, resulting in densities of 50.20 - 99.98% and columnar and stochastic pore morphologies
The influence of elevated Fe and Zn impurities on the rapid solidification behaviour of AA6061 processed using single-track laser surface melting
No full textIncreased adoption of recycled aluminum (Al) alloys in the automotive sector can provide several economic and environmental benefits through vehicle lightweighting, decreased fuel consumption, and reduction in greenhouse gas emissions. A major challenge in the adoption of secondary Al for a broader range of products is the accumulation of impurity elements, as increased scrap use can result in the compositional drift of alloy streams, leading to degraded mechanical and electrochemical properties. The objective of the current study is to demonstrate the use of rapid solidification processing (RSP) to increase the potential adoption of recycled Al through refinement of microstructural features and reduction of cracking. Cast ingots of an Al alloy 6061 (AA6061) were produced with iron (Fe) and zinc (Zn) additions in amounts ranging from 0 to 1 wt% to simulate recycling impurities. Thermodynamic simulations were used to predict the crack susceptibility of each alloy composition. Laser surface melting (LSM) trials were performed on plates cut from each ingot to generate rapidly solidified microstructures. The simulation predictions and microstructure results suggest that alloy impurity composition does influence the cracking behaviour observed in the laser melt pools, with both Fe and Zn additions having a mitigating effect on the observed cracking behaviour. The results suggest that the adoption of techniques such as additive manufacturing and laser welding could enable greater use of recycled Al alloys, advancing their use for automotive applications
Design and mechanical analysis of additively manufactured primitive flexures
No full textIn the design of compliant mechanisms, thin flexural members, consisting of bends and curves, can be used to produce a controlled path of rotation under load, which could benefit the design of cervical artificial disc replacements (c-ADR) for example to improve compliance and avoid adjacent segment degeneration. However, to date, there is little literature to characterize the design and mechanical properties of additively manufactured flexural members, limiting crucial data needed to inform implant design. To address this knowledge gap, the goal of this work is to design and additively manufacture a family of primitive flexures to explore how different design features affect the resulting mechanical response under load. Several flexure primitive design features were varied within a common 3-prong flexure component design, including flexure thickness, overhang angle, and number of bends. The response of these designs was then analyzed through applied loading (non-destructive cyclic bending and compression to failure) based on a targeted application of a compliant mechanism for cervical artificial disc replacements. The ability to realize complex parts with latticed or flexible features has value in improving compliance in orthopaedic applications. The primitive flexure designs were printed using Ti6Al4V on the EOS M290 laser powder bed fusion system. For mechanical testing, the flexures were printed between custom-designed endplates to attach to the AMTI VIVO joint motion simulator. The deformation response was captured using the ARAMIS 3D digital image correlation system. Testing results indicated that thicknesses of at least 1mm were required in Ti6Al4V flexures to replicate the axial compressive stiffness in the cervical spine. Introduction of compliant flexure zones led to a negligible reduction in stiffness, while increasing structure compliance in compression and rotation
Alexander at Issus: A Reflection of Conquest and Destiny
No full textAs the sun rises over the Cilician Gates, I stand witness to a pale light shining upon the path that lies ahead. It feels as though the land beneath my feet is alive, holding in its breath waiting for something to release it. This stillness is broken by the clatter of boots on stone, shouted orders, and the clanging of armour as the men prepare themselves. I see my men who stand ready, with ferocity in their hearts and a wild glint in their eyes. I feel their hunger for victory and their faith in me which is as steadfast as their shields. In this moment, I know I cannot falter–not now, nor ever
Drunk and Disorderly in Vernon: The Court Martial of Fusilier Florent Labonte
No full textIt was in 1944—five years into the Second World War—that Canadian manpower began to reach its limits. The management of manpower was difficult for all countries within the British Commonwealth, but for those with nonhomogeneous populations, like Canada and South Africa, it became necessary to weigh national priorities against international commitments. For Canada, the demands of an expanded overseas role and the fact that conscription remained solely for home defence meant that there simply were not enough men to fill the replacement quotas. Having already expanded their accepted age range and health standard, officials were forced to consider their largest remaining source of men: the home defence conscripts
NFLNet: A hard hitting evaluation of deep learning approaches to tackle prediction
No full textThis paper presents four architectures for predicting
tackle probability in an NFL football game. Accu-
racy, precision, recall, loss, and F1 scores are com-
pared to identify the best classification model for
the 2024 NFL Big Data Bowl. The models leverage
NFL tacking data, including player position, speed,
direction, and location relative to key field mark-
ers. Tracking information was processed to extract
meaningful plays, determine which features should
be used in the solution, and identify plays with suc-
cessful and unsuccessful tackle outcomes. A feed-
forward network is presented as a baseline, and
the performance of a convolutional neural network,
transformer, and graph transformer are compared.
The feed-forward network yielded an accuracy of
75%, which establishes the minimum accuracy of
a simple architecture that uses minimal features.
The convolutional network outperformed the base-
line with an accuracy of 85%, but performed worse
than the transformer and graph transformer, which
achieved accuracy results of 90% and 92%, respec-
tively. Ultimately, the graph transformer is found to
be most effective at predicting the tackle probability
for a league-average player
Image Generation at Different Detail Level: Scaling Skip Connections in ViT-based Diffusion Models
No full textDenoising diffusion probabilistic models (DDPMs)
excel in image generation, but users have limited
control over the level of detail and semantic richness
in generated images. Although prompt-based
diffusion models can create more detailed images
with descriptive prompts and utilize spatial masks
to preserve unedited regions, diffusion models frequently
overlook these constraints, leading to inconsistent
image regions. Inspired by transformers,
where each feature level encodes varying semantic
information, we propose a feature scaling method
at inference for a ViT-based diffusion model, U-ViT.
Our experiments on CIFAR-10 indicate that this scaling
approach effectively adjusts the level of detail in
generated images
Does Relation between Energy and Economic Growth hold for all Indian States? Empirical Analysis using Hurlin-Venet Process
No full textElectricity consumption is often regarded as a precondition for economic growth and any
bottleneck in its production can severely hurt the growth prospects of an economy more
specifically a developing one. Representing a strong case of its value, the causal relationship between energy consumption and economic growth is addressed by extending the Granger causality framework in a heterogeneous panel setup. Exclusively four different causal behaviours are examined: Homogeneous Non-Causality (HNC), Homogeneous Causality (HC), Heterogeneous Non-Causality (HENC), and Heterogeneous Causality (HEC). Both HNC and HC hypotheses are rejected in the causality direction from Economic growth to energy consumption thereby suggesting that the panel of Indian states is not homogeneous. Following this heterogeneous causality tests (HENC and HEC) are conducted for each Indian state to check the hypothesis of causality from economic growth to energy. For 8 out of 17 Indian states strong unidirectional causality is found while for 6 other states, there is no evidence of any causality in the stated direction. The remaining 3 states show weak evidence of causality. Thus, the results are suggestive of the fact that the central government cannot dictate policies at the state level rather state needs to frame regional policies in line with the situation that suits
Beware the Jabberwock, or, Let\u27s All Do the Techno-Oligarchic Slide
No full textThe Mutant, in this case, is capitalism. Isn\u27t it always? But to be more specific: capitalism qua capitalism is not necessarily bad. Nor is it good. It\u27s like a gun – guns alone rarely kill people. Unfettered access amid a culture of violence, however, does. Ultimately, then, it is legislation that brings the necessary restrictions on money trumping Good. Anarchy can do so temporarily, as was the case in the early days of the internet. But the lack of a central system of organization or control eventually leads to the centralization of capital, and those with more begin to impose their will in order to further benefit themselves – essentially creating the missing rules in their own interest. The current state of what we generally refer to as neoliberal capitalism has meant a void filled with broligarchs (Cadwalladr, 2024)
Strong Spirits: A 1941 Court Martial Case of Canadian Sappers in England Who Decided to Shoot Up the Town
No full textThis paper presents the story of two Canadian sappers Lorne Long and Maurice Francis Flynn, who were stationed in England in February of 1941. In the true spirit of a hard days’ night, these sappers went pub crawling, got drunk, and decided to grab a rifle and shoot up the nearby town. When their bunkmate overheard the conversation, he reported it to their Lance Corporal, also drunk at the time, who in turn tried to apprehend them in the dark English countryside. Sapper Long did not like that and shot at him five times, missing every shot. Armed with a flashlight, the intoxicated Lance Corporal returned to the garrison garage and attempted to commandeer a truck for the manhunt. A sober captain stepped in and stopped him. The next morning, the hungover Long woke up in the woods as a stray dog was licking his face. He walked back, passed the guards without a problem, missed the formation while cleaning his rifle, and was promptly arrested. Looking at this incident through courts martial files and related documents, we will reconstruct the events and characters involved and try to understand why these men could behave like this only twenty years after prohibition