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Numerical investigation of effect of mechanical compression on the transport properties of fuel cell microporous layer using a pore-scale model
Full text linkThe microporous layer (MPL) plays an important role in water and thermal management of proton exchange membrane fuel cells (PEMFCs). An in-depth investigation of the mechanical compression effect on transport properties in the MPL can help optimize cell performance. In this work, the microstructure of the MPL is numerically reconstructed and the finite element method is applied to simulate mechanical behavior. Besides, the distribution of stress-strain, porosity, and pore size in the MPL under ten different levels of mechanical compression strains are studied. Lastly, the pore-scale model is employed to investigate the effective transport properties of the MPL as a function of compression strain. The analysis reveals that as the MPL strain increases from 0% to 40%, there is a 29% decrease in porosity, a 50% reduction in average pore diameter, a 60% decrease in effective gas diffusivity, a 100% increase in tortuosity, and an 80% increase in electrical and thermal conductivity. With the escalation of mechanical compression, both the magnitude and uniformity of stress-strain-displacement concurrently rise. Mechanical compression strains below 20% exhibit a lesser impact on transport properties. Beyond this threshold, exceeding the 20% compression strain point, mechanical stress assumes a critical role in influencing MPL transport properties.This work was supported by National Natural Science Foundation of China (grant numbers 52306270); the Guangdong Basic and Applied Basic Research Foundation (grant number 2022A1515110456); Donghai Laboratory Open-end Fund, Zhoushan, China (grant number DH-2022KF0305); the research innovation team construction plan of Wuhan City Polytechnic College (grant number 2023whcvcTD01).FacultyReviewe
The Use of Digital Technologies by Teachers in Their Pedagogical Practice and the Experiences and Conditions that Enable Their Work: A Case Study
No full textDigital technologies are pervasive in many areas of life in the 21st century, including education (Haleem et al., 2022), and teachers and schools have traditionally been associated with being responsible for developing in students the competencies that will allow them to fully participate in society. There are different frameworks and theories that discuss how student teachers should be educated to use digital technology pedagogically and how students in schools should learn to use it. Based on a selection of three theories, Digital Literacies, Technological Pedagogical Content Knowledge (TPACK), and Maker Pedagogy and Pedagogical Hacking, this study sought to investigate how and to what purposes teachers used digital technologies in their practice for teaching and learning. Additionally, it aimed at understanding some of the experiences and conditions that allowed teachers to do the work they did.
Framed as a qualitative case study, this research drew on literature, the researcher experience, curricular policies, and the experiences and perceptions of four teachers who were known in their schools for the work they did with digital technologies. Findings show that formal education played a decisive role in educating teachers to use digital technologies in their practice. Constant changes brought about by new technological inventions, curriculum renewal, and teachers recognizing themselves as unfinished contributed to teachers engaging in continuing learning practices. These practices happened mainly by means of collaboration with peers and students, professional development opportunities, and looking for help online.
Regarding digital literacies, participants recognized the importance of exposing students to different genres and giving learners the opportunity to communicate their learning and express themselves by means of different formats. Participants also recognized that equipment availability, connection reliability, and foundational digital competencies were required for any work with digital technologies to be properly done in schools. Student privacy appeared as paramount for participants. There were different systems in place such as lessons, discussions, and privacy impact assessments (PIAs) to guarantee student safety when going online, and these promoted different strategies that allowed students to develop a sense of digital citizenship. In conclusion, the study indicated that technology played an important role in instructional delivery and in student activities with a focus on real-life application. Surprisingly, teacher librarians demonstrated a vital role in the schools, providing support for both teachers and students.Graduat
A Near Glimpse into a Distant Past: Chemical Analyses of Ancient Milky Way Satellite Galaxies Using High-Resolution Stellar Spectroscopy
No full textThe least-luminous galaxies ever detected, ultra-faint dwarf (UFD) galaxies, are ancient, metal-poor, dark-matter dominated, and likely represent the floor of the galaxy luminosity function. Their stars preserve the signatures from early chemical evolution, and their dark matter haloes are testing grounds for Lambda-CDM cosmological models. UFDs are subject to tidal interactions with the Milky Way and dwarfs, which visually range from disrupted streams to slightly elongated structures. An extended structure may also be the result of a minor merger of dwarfs. To further our understanding of these extended structures, we examine high-resolution spectra of stars in the outskirts of UFDs. It is expected that signatures of one or just a few early supernovae may be detectable in the chemical abundance patterns of UFD stars. High-resolution spectroscopy of the brightest individual stars allows us to recover these signatures, and piece together the chemodynamical history of these galaxies. We use Gemini/GRACES to obtain high-resolution spectra of potential members in the outskirts of three ultra-faint dwarf (UFD) galaxies: Coma Berenices (>2Rh), Ursa Major I ( 4Rh), and Boötes I ( 4Rh), as well as a new member in the central region of Ursa Major I (where the half-light radius Rh is the radius within which half of the galaxy’s light is contained, measured along the semi-major axis). Targets were selected with a new Bayesian technique which uses Gaia EDR3 photometry and astrometry to determine stellar membership to UFDs. All 5 stars are determined to be members by precision radial velocities and metallicities that confirm their associations with the UFD galaxies. The spectra were also used to measure absorption lines for 10 elements (Na, Mg, K, Ca, Sc, Ti, Cr, Fe, Ni, and Ba), which confirm that the chemical abundances of the outermost stars are in good agreement with stars in the central regions. The abundance ratios and chemical patterns of the stars in Coma Berenices are consistent with contributions from SN Ia, which is unusual for its star formation history and in conflict with previous suggestions that this system evolved chemically from a single core collapse supernova event. The chemistries for all three galaxies are consistent with the outermost stars forming in the central regions, then moving to their current locations through tidal stripping and/or supernova feedback. In Boötes I, however, the lower metallicity and lack of strong carbon enrichment of its outermost stars could also be evidence of a dwarf galaxy merger. To pursue further high-resolution spectroscopic observations of UFD stars, I carried out an internship at the Gemini South telescope Observatory which was timed with the commissioning of the Gemini High Resolution Optical SpecTrograph (GHOST). Target selection, logkeeping, early data reduction, calibration tests and instrument operation tasks were completed during 17 nights of commissioning between June and September 2022. Since commissioning, I performed bug-testing and developed streamlined methods for processing data to work towards completion and refinement of the data reduction
pipeline. With this experience and relative expertise, I worked with the science team towards the goal of publishing our first science results. GHOST has been integrated into the Gemini instrumentation suite and is available for observing proposalsGraduat
Examining the Intersections of Brain Injury, Mental Health & Addictions: A Systematic Evidence Map of Treatments and Analysis of Community-Based Stakeholders’ Priorities for Future Research
Full text linkIntroduction: Acquired brain injury (ABI) and mental health and addiction (MHA) related conditions are leading causes of death and disability worldwide. Despite their high comorbidity and the devastatingly synergistic effects of their co-occurrence, ABI and MHA are frequently studied and managed as separate entities in both research and clinical practice. Addressing the profound need to better understand the intersections of ABI and MHA, this thesis involved two innovative community-engaged studies: (1) a systematic evidence map of interventions for MHA in ABI populations, completed with an interactive tool for knowledge users; and (2) a collaborative priority-setting study that identified stakeholders’ top ten priorities for research.
Methods: Study 1: Evidence mapping methodology was used to identify relevant literature. PsycINFO, SCOPUS, MEDLINE, the Cochrane Library (Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials), Web of Science, and CINAHL were searched. The Measurement Tool to Assess Systematic Reviews 2nd edition (AMSTAR-2) evaluated methodological quality, and an iterative prototyping design was employed to develop the evidence map user interface. Study 2: A multi-phasic health research priority-setting process was co-designed and executed with community-based stakeholders, including researchers, clinicians, service providers, policy makers, and people with lived experience. Stakeholders’ ideas led to the generation of research questions, which were prioritized at a one-day workshop and analyzed using an equation we created, the Question Priority Composite (QPC) formula.
Results: Study 1: From the 63,843 identified records, a total of 485 studies involving 735,203 participants with ABI were included, comprised of 283 impact evaluations, 119 systematic reviews and meta-analyses, 39 clinical trial registries, 31 published study protocols, and four clinical practice guidelines. AMSTAR-2 ratings varied, with most falling within the low-quality range. Cerebrovascular injuries, pharmacological interventions, and studies examining depression were among the most researched topics. Several gaps in the evidence base were identified, particularly for housing interventions and treatments for substance use post-ABI. Study 2: Fifty-nine stakeholders participated in the priority-setting activity during the workshop. Analysis of QPC scores resulted in a rank-ordered list of the top ten questions for research addressing the intersections of ABI and MHA. Questions identified touched on several pressing issues (e.g., opioid crisis, homelessness), encompassed multiple sub-types of ABI (e.g., hypoxic-ischemic, mild traumatic), and involved different domains (e.g., identification, intervention) of health research.
Conclusions: The present thesis led to two main outcomes. The evidence mapping review, the first of its kind in the field, resulted in the development of DECISION–MAP (Database of Evidence Concerning Interventions Supporting the Intersections Of Neurotrauma–Mental health, & Addictions Problems), a practical tool that culminates research on interventions for MHA in ABI populations while highlighting gaps in the knowledge base (www.decision-map.com). The priority-setting study led to a rank-ordered community driven list of ten research priorities, acting as a blueprint for high impact investigations that address stakeholders’ most urgent needs. Together, these studies underscore the multitude of complexities that lie within the intersections of ABI and MHA and serve as catalysts for future research and improvements in clinical care.Graduate2025-04-1
Whose Values on Whose Lands? An Exploration of Perspectives on Indigenous Conservation Financing in Canada
Full text linkWhile Indigenous knowledge is increasingly recognized as crucial in addressing the global environmental crisis, the application of Indigenous knowledge(s) in environmental management realms remains underfunded globally, posing significant challenges to the effective stewardship of lands and waters. Conservation finance, defined as mechanisms that generate, manage, and deploy financial resources for environmental conservation, has recently emerged as an alternative to traditional grant funding for conservation activities. However, little research has documented conservation finance in practice, specifically, the emerging mechanisms which support Indigenous stewardship and conservation in Canada, and their impacts. This research asks: 1) What is the current landscape of Indigenous conservation finance in Canada? And 2) What are the key perceptions of peoples involved in these conservation finance initiatives? A Postcolonial Critical Realism methodological approach, a theoretical literature review, a landscape analysis, and semi-structured interviews were conducted to answer both these research questions. The landscape overview found that Indigenous conservation finance in Canada is diverse in mechanism type, size, and location and is evolving as Indigenous Peoples imbed local values in mechanisms and financing processes. Perspectives on these mechanisms varied; nonetheless, two key characteristics of the sector emerged: firstly, its association with extractive industries, and secondly, the role of conservation finance mechanisms in either reinforcing colonial values or resisting them. How values were enmeshed in these mechanisms greatly impacted the outcomes of initiatives, and power was demonstrated in ways in which communities could influence what was financed and how it was financed. This research contributes to the field of scholarship on conservation finance, mainly as it explores how financial mechanisms can support or subvert Indigenous values through their design.Graduat
The Quirky Case of Quirky Case: Understanding Dative Subjects in Icelandic
Full text linkGrammatical case is a structural relation where a DP, the dependent, is marked for its grammatical relation to the head, the verb. One language which has contributed significantly to linguists’ understanding of case is Icelandic. Though most Icelandic subjects are marked using nominative case, so-called ‘quirky’ subjects are marked using a non-nominative case. Dative subjects have received significant attention in the literature. This project aims to provide an overview of the features of dative subjects in Icelandic and outline past analyses of these arguments, assessing their strengths and weaknesses from a Minimalist framework. Ultimately, I will outline several limitations of using θ-roles as a framework for analyzing quirky case and follow Wood (2015) and Wood and Sigurðsson (2014) (as well as Cuervo’s (2003) work on Spanish dative subjects) in arguing that dative subjects are best analyzed as applied arguments introduced in spec-Appl before moving to the subject position spec-TP, which explains their subject-like properties. I will argue for the importance of accounting for grammaticalization and historical processes in our models of syntax, using current and historical changes in Icelandic and its relatives. Finally, I will compare Icelandic with other languages with oblique subjects, contrasting it with languages in which subject case marking varies with tense, aspect, and/or volitivity and/or which may have a lower final position than spec-TP.Jamie Cassels Undergraduate Research Awards (JCURA)UndergraduateReviewe
Robust and efficient uncertainty-aware multi-object tracking through vision-based ego-motion awareness
No full textThis thesis presents the development and refinement of the UVEMAP system, an \textbf{U}ncertainty-aware \textbf{V}ision-based \textbf{E}go-\textbf{M}otion-\textbf{A}ware target \textbf{P}rediction module designed for robust multi-object tracking using only monocular camera inputs.
This work aims at improving the performance of Multi-Object Tracking (MOT) systems by the incorporation of ego-motion and depth estimation uncertainty through a heuristic and computationally efficient solution.
The first step involves separating the impact of camera movement in Kalman-based MOT algorithms. This helped to increase tracking precision by ensuring that the vehicle ego-motion did not negatively impact the targets' anticipated location. The work is continued by creating a pure vision system that uses only the image stream from a monocular camera; thus removing the requirement for other sensor data, like IMUs, GPS, and wheel encoders. This strategy improves the system adaptability and applicability in many contexts as the proposed solution can completely be agnostic of the metric scale such as depth and translation vector.
One of the main contributions is the integration of visual odometry and depth estimation using a modified Monodepth2, which estimates depth and camera motion by employing a self-supervisory signal generated by image reprojection error. The modifications to Monodepth2 guarantee its compatibility with UVEMAP, allowing precise depth and pose estimation from monocular images. In order to account for uncertainty in depth estimation, a conformal prediction method is applied which identifies prediction intervals to gauge the level of uncertainty associated with each depth estimation by computing nonconformity scores in the dataset. This utilization of data enhanced the capability of the Kalman filter to handle occlusions and noisy readings.
The incorporation of unified scale depth and pose estimations as well as depth uncertainty quantification into the proposed target prediction module resulted in a substantial improvement in performance metrics compared to baseline methods. Experiments conducted on the KITTI dataset show that UVEMAP significantly reduces identity switches and enhances tracking accuracy and robustness. The computational efficiency of the proposed method, stemming from its heuristic nature, makes it suitable for deployment on edge devices, including autonomous ground robots and vehicles.
This research makes a notable contribution to the field of multi-object tracking by presenting a comprehensive framework that integrates ego-motion awareness and uncertainty quantification, all from a monocular video stream, to achieve superior tracking performance.Graduat
Assessing the accuracy of georeferenced landcover data derived from oblique imagery using machine learning
No full textRepeat photography offers distinctive insights into ecological change, with ground-based oblique photographs often predating early aerial images by decades. However, the oblique angle of the photographs presents challenges for extracting and analyzing ecological information using traditional remote sensing approaches. Several innovative methods have been developed for analyzing repeat photographs, but none offer a comprehensive end-to-end workflow incorporating image classification and georeferencing to produce quantifiable landcover data. In this paper, we provide an overview of two new tools, an automated deep learning classifier and intuitive georeferencing tool, and describe how they are used to derive landcover data from 19 images associated with the Mountain Legacy Project, a research team that works with the world's largest collection of systematic high-resolution historic mountain photographs. We then combined these data to produce a contemporary landcover map for a study area in Jasper National Park, Canada. We assessed georeferencing accuracy by calculating the root-mean-square error and mean displacement for a subset of the images, which was 4.6 and 3.7 m, respectively. Overall classification accuracy of the landcover map produced from oblique images was 68%, which was comparable to landcover data produced from aerial imagery using a conventional classification method. The new workflow advances the use of repeat photographs for yielding quantitative landcover data. It has several advantages over existing methods including the ability to produce quick and consistent image classifications with little human input, and accurately georeference and combine these data to generate landcover maps for large areas.We thank Jasper National Park, fRI Research, Mitacs Accelerate, Lorene Kennedy Environmental Studies PhD Award, Lorene Kennedy Field Research Award, and SSHRC for supporting this research.FacultyReviewe
Teeter-tottering between worlds: Newcomer children’s voices & stories on identity in Canada
Full text linkIn recent years, a significant number of people across the globe have crossed borders in search of safer homes, better health care, education, and economic opportunities (International Organization for Migration, 2022; UNICEF, 2023). For the children who have experienced migration, they are more likely to face a discontinuity between their cultural heritage and the culture of their new society. In this study, the importance of listening to newcomer Latin American children’s experiences in Canada was addressed in relation to their sense of belonging and identity development in a new country. Framed by sociocultural theory, funds of knowledge, multimodality, and translanguaging, 4-year-old Latin American newcomer children’s experiences, (transnational) funds of knowledge, and identity development were examined across multiple contexts, such as their homes and daycare environments. Findings revealed that children combined and compared symbols, knowledge, experiences, and language from their home countries with those in Canada to develop their identities and sense of belonging in a new country. This study also provides additional insight on the significant role adult caregivers played in the children’s worlds and resettlement journeys. Findings highlighted the importance of parents and early childhood educators engaging in translanguaging practices to accommodate newcomer children’s needs and welcome their languages, knowledge, and identities in diverse environments. This study also offers recommendations for early childhood educators on potential ways to welcome and include newcomer children’s funds of knowledge, languages, culture, and identities in early learning contexts.Graduat
Excitation Emission Matrix (EEM) Spectroscopy and Computational Evaluation of Excited States of Carbazole – Bromobenzothiadiazole (CBB)
No full textWe examine the source of solvatochromism in a fluorescent organic dye using fluorescence Excitation Emission Matrix (EEM) spectroscopy, supported by ab initio calculations. The dye, carbazole–bromobenzothiadiazole (CBB), has a donor-, an acceptor-, and a bridging group connected by sigma bonds. The study of its fluorescence in liquid solutions shows a strong emission wavelength dependence on the solvent polarity but only a negligible dependence on solvent viscosity. In previous work, the polarity-induced solvatochromism was attributed to a twisted intermolecular charge transfer (TICT) state, where the excited state twists into a conformation in which a large dipole is generated between the carbazole (donor) group and the benzothiadiazole (acceptor) group. (1)
Density Functional Theory (DFT) calculations are performed to map the excited state potential energy surface and the associated dipole moment in different solvent environments using the corrected linear response (cLR) solvent model (2). The calculations agree well with the observed energy differences and the solvatochromic shifts.
To determine the configuration of the molecule in the excited state before emission, the dihedral angles between the three main groups of the molecule are investigated. Ab initio calculation indicates that the three dihedral angles between the donor-, bridging-, and acceptor-groups in the excited state change only by comparably small amounts between the Franck-Condon region and the potential minimum of the excited state, from which fluorescence is expected to occur. The molecular configuration in the excited state’s potential minimum is therefore close to the molecular structure in the Franck-Condon region, and not a “twisted” structure indicative of a TICT structure. Interestingly, we calculate a second local minimum on the excited state in the global excited state form when the third dihedral angle, θ_3 =90°. However, the energy in this twisted form is much higher than that of the first minimum configuration (θ_3= 0°). Since the second excited state minimum is not accessible upon excitation of the molecule emission is calculated to occur from the lowest excited state, which was, indeed, observed. Consequently, in this research, the solvatochromic shift is due to the charge separation around the acceptor domain, which is partially induced by the polarity of the environment.
This work raises questions about the presence of TICT state in other molecules. We argue that the observation of solvatochromatic shifts, and the presence of donor and acceptor moieties alone are not sufficient to positively identify a TICT state.
We found that TD-DFT calculation require a sophisticated solvent model to quantitatively model the solvatochromic shift. Also, we observed the natural transition orbitals are far more useful in identifying donor and acceptor moieties compared to the commonly used canonical orbitals. Excitation Emission Matrix (EEM) spectroscopy serves as a useful experimental tool to identify excitation and emission pathways.Graduat