title: Ethnocultural Identity Clarity and the Associations with Psychological Distress and Stigma of Depression

contributor:
Stuart, Heather
Public Health Sciences

subject:
Mental health
Culture
Epidemiology
Stigma of mental illness
University

abstract:
Background: Canadian universities are becoming more multicultural in the past decades. Students also report high level of depressive and anxiety symptoms, as well as their related stigma. Past studies that explored the associations between cultural variables and psychological well-being often categorized a participant as coming from a single ethnocultural group, disregarding the individual cultural processes that a multicultural individual experiences. We explored two ethnocultural variables: 1) ethnocultural groups (the cultural group that a person identifies with), and 2) cultural identity clarity (how much a multicultural person is clear on who they are culturally), and how they were associated with psychological distress and the level of public stigma of depression.

Methods: After literature search, related questionnaires were identified, and additional questions were compiled into a single survey package. A total of 4,215 Queen’s University students were invited to participate in the study. We first evaluated the performance of the Cultural Identity Clarity Scale. We then explored the association between cultural identity clarity and psychological distress using the modified Poisson regression. The relationship between ethnocultural group and stigma of depression was explored using ordinal logistic regression. All models were adjusted for demographic variables that were relevant to the post-secondary environment.

Results: Our final sample size was 750 students. The Cultural Identity Clarity Scale performed well among our sample, with good reliability and convergent validity. Multicultural students who were clearer on who they were culturally experienced a lower risk of being psychologically distressed compared to those who were less clear on who they were. We also found that the levels of stigma of depression were different depending on the identified ethnocultural group among multicultural international students.

Conclusion: Our findings suggested that ethnocultural factors may be implicated in psychological well-being and stigma of mental illness in post-secondary settings. We propose future research to focus on the individual multicultural process alongside the exploration of ethnocultural groups when conducting research around the multicultural population. We also recommended a mental health service approach that is culturally inclusive and specific, as well as an anti-stigma program that is more targeted to address the cultural components of stigma.

abstract: PhD


title: On the flexible nature of the relationship between attention and active memory representations

contributor:
Wilson, Daryl
Psychology

rights: Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada

rights: ProQuest PhD and Master's Theses International Dissemination Agreement

rights: Intellectual Property Guidelines at Queen's University

rights: This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.

subject:
Attention
Memory
Working Memory
Task demands

abstract: Despite being two of the most commonly studied constructs in cognitive psychology, our understanding of how active memory representations interact with attention remains highly contentious. One of the primary reasons for this continued debate has been a reliance on artificially dichotomizing the roles these systems play and ignoring the role of task demands which include differences in factors such as context, task goals, or stimulus and response modalities. This restricted view has far-reaching consequences across many topics central to cognitive psychology such as (1) attention’s role in governing the information that enters working memory (WM), (2) WM’s role in governing perceptual attention, and (3) whether WM representations rely on the same sensory neural architecture used for perception. In the first set of experiments (Chapter 2), I demonstrated a role for task demands (the expectation to report an attended attribute) in reducing the strength of the resulting representation in WM, as opposed to wiping it out completely. In the second set of experiments (Chapter 3), I showed that the modality of studied information (pictures in Experiment 2 or words in Experiment 3) increased the extent to which attention was captured by content presented in the same modality. Specifically, encoding pictures into episodic LTM led to visually but not semantically similar content capturing attention, whereas the opposite was true when encoding words. Finally, in the third set of experiments (Chapter 4), I demonstrated how different encoding task demands influenced the spatial specificity with which WM interfered with a visually attended target during a modified WM Stroop task. Specifically, in Experiment 1 (remember identity only) and 2 (remember identity and location), perceptual and WM distractors displayed distinct patterns of interference: spatially specific for perceptual and spatially global for WM distractors. In contrast, in Experiment 3 (remember identity and location of two items) I found that perceptual and WM distractors both produced spatially specific patterns of Stroop interference. Across these three diverse sets of experiments, I have demonstrated the importance of task demand manipulations in developing a more comprehensive understanding of the relationship between attention and active memory representations.

abstract: PhD


title: Exploring How Policy, Practice and Regional Perspectives of Caregiving Combine to Mitigate Unpaid Caregiver Distress: A Case Study of the Former South West Local Health Integration Network of Ontario

contributor:
Finlayson, Marcia
Norman, Kathleen E.
Aging and Health

subject:
Unpaid caregivers
Older adults
Community care
Moral distress
Case study

abstract:
The impact of unpaid caregiving is significant and potentially detrimental to the overall health of caregivers themselves.  The consequences of caregiving can contribute to unsustainable care circumstances for the care recipients in the community, leading to hospitalization or early mortality for both parties.  Distress among caregivers can be high in rural and remote areas where access to appropriate services, particularly personal support work and respite care can be challenging to reliably deliver.  Unexpectedly, the former South West Local Health Integration Network (SW LHIN) in Ontario, with a large rural population, consistently documented the lowest rates of caregiver distress across the province for a near decade.
The aim of the dissertation was to explore how the policies, practices and geographic culture of the former SW LHIN interconnected in a manner that enabled caregivers to mitigate distress.  Using a constructionist case study methodology, this qualitative study adopted a single case design with multiple units of analysis.  The case was bound by time and place:  the geographical boundaries of the SW LHIN as of 2019, when the study began. The individual caregiver interviews, (n=13) the focus group and interviews with community service providers (n=24) and an analysis of 92 documents were the data sources for the case. Braun and Clarke’s strategy for thematic analysis was used to analyze the data.
Three manuscripts were generated from the data, with themes from manuscripts one and two shared several overlapping meanings, particularly around service support assumptions, community connections, partnerships, and care expectations.  Manuscript three provides a discussion on the moral distress experience that arises, in part, from the tensions of being both a member of a community and professional serving the community. Taken together, the case study findings suggested that two overarching meso-level elements combined to minimize caregiver distress in the region:  the presence of a regional identity and the perception of social support at the community and organizational level.  The spotlight on caregiving today suggests that there has never been a better time for research or interventions to look beyond individualistic interventions and towards the wider social landscape to mitigate caregiver distress.

abstract: PhD


title: Retracing Eternity: Freemasonry, Theosophy and the Occult Revival, 1875-1925

contributor:
Akenson, Donald
Collins, Jeffrey
History

rights: Attribution-NonCommercial-NoDerivs 3.0 United States

subject:
Freemasonry
occult
comparative religion
Helena Blavatsky
Theosophy
Golden Dawn
Ordo Templi Orientis
Aleister Crowley

abstract:
In 1875, in a small apartment in New York City, a handful of freemasons and spiritualists gathered to create a new occult society. What emerged, after hours of debating, drinking and smoking, was the Theosophical Society. Its chief representatives were the spiritualist, Helena Petrovna Blavatsky, and her masonic associate, Henry Steel Olcott. Together, these two mystical individuals helped inspire a trans-continental occult revival, and fundamentally transformed the religious margins of Western society.
	The occult revival that followed was a vast and complicated phenomenon. In an explosion of esoteric zeal, occultists sought to reform everything from art and agriculture, to education and epistemology. While there were countless books, journals and minor figures devoted to the occult movement, four societies and their founders stand out. Helena Blavatsky’s Theosophical Society; William Wynn Westcott’s, and S. L. Mathers’ Hermetic Order of the Golden Dawn; Aleister Crowley’s Ordo Templi Orientis, and Rudolf Steiner’s Anthroposophical Society. These were the most famous and significant occult movements, and in many ways, they remain culturally relevant today.
	However, discussions of these societies seldom, if ever, examine all four together. This is a mistake. Not only were these societies integrally connected, but when analyzed holistically, certain patterns reveal themselves. These patterns go a long way in explaining the centripetal forces of the occult revival, and point to an associational and ideational root from the early 18th century. This root is Freemasonry. Surprisingly, the profound role of Freemasonry within the ideational world of Western esotericism and the occult remains largely unfinished. What is revealed once this connection is excavated, is a centuries-long tradition of freemasonic scholarship on ancient and comparative religion. Elements of Freemasonry, it appears, underwent a religious transformation in the 18th century, and some members reinterpreted the fraternity as a meta-religion associated with the Philosophia Perennis. This association continually developed as the Western world came into contact with ever increasing numbers of foreign religions. What emerged was a highly speculative narrative of global religious development, centered on the institution of Freemasonry—and it is within this distinctly masonic narrative that each of the leading occult societies developed.

abstract: PhD


title: Modelling of a Heat Recovery Ventilator Incorporating Thermoelectric Modules

contributor:
Harrison, Stephen
Mesquita, Lucio
Mechanical and Materials Engineering

subject:
Thermoelectric
Heat Pump
HRV

abstract: Heat recovery ventilation (HRV) involves the recovery of heat from exhaust air exiting the home. HRV works to both save energy and provide indoor air quality and comfort [1]. Focus has also been placed on alternatives to vapour-compression devices traditionally used as heat pumps, due to the harmfulness of refrigerants contained in these systems [2]. Thermoelectric modules (TEMs) are solid-state devices that can be used for converting electrical energy into thermal energy, effectively creating a heat pump. A thermoelectric module-based heat pump heat exchanger was modelled to determine performance when integrated into a heat recovery ventilation system. The model was developed as a node-based numerical system allowing the performance at various locations in the system to be analyzed. The model was developed further to evaluate HRV performance with and without thermoelectric modules included. Characteristics of the model geometry and configuration were based on a prototype developed by Natural Resources Canada, which includes a TEM-based crossflow heat transfer core in series with a LifeBreath model RNC5-ES HRV. The numerical model was implemented in Fortran90 and an open source compiler. A subsequent parametric evaluation of the heat sink selected by NRCan was completed and indicated that modifications to the current geometry would result in increased effectiveness and performance. Performance metrics were modified and evaluated for their suitability for producing meaningful results, including the development of the Heat Transfer Enhancement Factor (HTEF) metric. Based on the evaluation of different TEM models, the TEC127-14 thermoelectric module showed the greatest HTE for the hot-side heat transfer and is recommended for implementation. An analysis of flow configurations for integrating the TEM-HX into a conventional HRV indicated that a counterflow configuration with the exhaust inlet (from the house) directed through the TEM-based heat exchanger prior to entering the non-TEM heat exchanger core was the most effective configuration.

abstract: M.A.Sc.


title: Using genomics to quantify population structure and genetic diversity of the Arctic char (Salvelinus alpinus) in the Lower Northwest Passage, Nunavut, Canada

contributor:
Lougheed, Stephen C.
Biology

subject:
Population genomics
Arctic char
Salmon fishery
DNA sequencing
RNA sequencing
Population genetics
Fishery management
GTseq

abstract:
The contemporary genetic diversity and population structure of a species reflect past and present demographic changes, and the combined effects of microevolutionary forces on its populations. Understanding the factors that shape geographical distributions and intraspecific genetic diversity is an important first step in the formulation of conservation and management plans. Because of their ecological, evolutionary, cultural, and economic significance, many efforts have been dedicated to genetic studies of wild populations of salmonid species like the Arctic char (Salvelinus alpinus). Despite this, patterns of genetic diversity remain uncharacterized in the King William Island (KWI) region of the Lower Northwest Passage (LNWP), Nunavut. Given rapid climate warming in the Arctic, food insecurity issues among Indigenous populations, and the success of a char fishery in Cambridge Bay, the Gjoa Haven community in KWI is eager to establish its own science-based, ecologically-sound, and sustainable char fishery. Key to this aspiration is the delineation of distinct char populations (stocks) to guide fisheries management.
This thesis centres on quantifying and understanding the patterns of genetic diversity in char in the LNWP using two genome-wide panels of Single Nucleotide Polymorphism markers (SNPs) obtained from DNA and RNA sequencing (DNAseq and RNAseq). Using DNAseq data comprising 3,074 SNPs for 413 individuals and a series of population genetics approaches, I found deep genetic differentiation between char populations in the KWI and those on the mainland around Chantrey Inlet, ~200km to the south. I also found 22 SNPs with possible signatures of selection, and associations between genetic distance, geographic distance, and environmental variables. I then focused on the two clusters to infer their demographic histories, and found support for an isolation-with-migration demographic scenario over a strict-isolation model. The RNAseq datasets agreed on an overarching genetic division between KWI and Chantrey Inlet, and the presence of a mixed-stock site in Murchison River, but overall lower genetic differentiation (lower FST) compared to DNAseq data. Finally, I developed a new genetic tool for accurate and fast stock composition identification. Collectively, this work adds to salmonid population genetic studies, and brings new insights for the establishment of a char commercial fishery in the LNWP.

abstract: PhD


title: Examining the Relationship Between Home Care Rehabilitation Therapy Services and Healthcare Utilization Among Those with Multimorbidity in Ontario, Canada

contributor:
Donnelly, Catherine
Rehabilitation Science

subject:
Rehabilitation therapy
Home care
Occupational therapy
Physiotherapy
Healthcare utilization

abstract:
Individuals that experience multimorbidity are higher healthcare users and at an increased risk for poor health outcomes and functional decline. Rehabilitation therapists (occupational and physical therapists) can help these individuals with complex health challenges to address their functional needs and negotiate successful transitions in health care. Research was needed to determine the association between home care rehabilitation therapy and healthcare utilization outcomes.
The overarching aim of this dissertation was to explore the association of home care rehabilitation therapy on unplanned acute health care utilization outcomes (i.e., hospitalizations and emergency department visits) for individuals with multimorbidity that were recently discharged from the hospital. This dissertation addresses this aim through three studies: a rapid review and two retrospective cohort studies. The rapid review synthesized the existing literature about home care rehabilitation therapy services for individuals with multimorbidity. The key findings from this review were that existing literature focused primarily on physical therapy interventions addressing functional impairment, and that system-level impact of therapeutic interventions was poorly addressed due to an emphasis in the literature on those with multimorbid musculoskeletal conditions.
Studies two and three were retrospective cohort studies using health administrative data from ICES. In the first cohort study, we explored the association of home care rehabilitation therapy on healthcare utilization outcomes for individuals with multimorbidity that were recently discharged from an acute care hospital. In the second cohort study, this population was considered within the context of a discharge from an inpatient rehabilitation unit setting. The results of these two studies demonstrate that home care rehabilitation therapists are seeing clients that are medically complex (4+ chronic conditions), and require more help across areas of activities of daily living, cognition, and pain. Overall, there is a significant reduction in hospital readmission and emergency department use among those receiving rehabilitation therapy compared to those receiving other home care services, irrespective of discharge location. These findings suggest that rehabilitation therapists are instrumental in successful discharges to a home environment that benefit both the client and the healthcare system. These findings provide the foundation to explore the role of rehabilitation beyond single condition clinical guidelines.

abstract: PhD


title: Deep Learning for Touchless Human-Computer Interaction using 3D Hand Pose Estimation

contributor:
Etemad, Ali
Marshall, Joshua
Electrical and Computer Engineering

subject:
Hand gesture recognition
Deep learning
Hand pose estimation

abstract:
This thesis focuses on hand pose estimation (HPE) as a crucial component for human-computer interaction, for example in gesture-based control for physical or virtual/augmented reality devices.
We start by introducing an inexpensive and robust proof-of-concept mechanism for a practical gesture-based control system,
which has been implemented and tested on a robotic wheel loader. To explore the feasibility and practicality of such a system, we resort to off-the-shelf equipment and models. Using an RGB camera and laptop, the system processes hand gestures in real-time to control a loader in construction zones. After designing four different hand gestures for controlling the loader, we collected 26000 images and trained a neural network to recognize the hand gestures. With the proposed hand gesture recognition system, we successfully controlled a loader to excavate a rock pile. Next, we present several open problems in the area of HPE. Despite the significant progress in HPE in recent years, the accuracy and robustness of these methods still suffer from self-occlusion, as well as sensitivity to variations in camera viewpoints and environments.
We thus focus on multi-view and video-based 3D HPE for developing a more robust system. Given the scarcity of multi-view and video-based datasets, we created a large synthetic multi-view video-based dataset of 3D hand poses. These videos were simultaneously captured from six different angles with complex backgrounds and varying levels of dynamic lighting. Next, we implemented a neural pipeline consisting of image encoders for obtaining visual embeddings of the hand, recurrent learners for learning jointly from multi-view information over time, and graph networks with U-Net architectures for estimating the final 3D poses. The results of our studies demonstrate the added value of each component of our method as well as the benefits of including both temporal and sequential contextual information in the dataset. Finally we focus on the aggregate of contextual information across time and camera views, and use self-attention transformers for learning sequential contexts for 3D HPE. Throughout our experiments, this method performed well for both temporal and angular sequence varieties. The method also achieved state-of-the-art results on our proposed dataset and a publicly available sequential dataset.

abstract: M.Sc.


title: Surficial exploration methods for detecting low sulfide high precious metal and Ni-Cu-PGE mineralization in glaciated terrain

contributor: Geological Sciences and Geological Engineering

rights: Attribution-NonCommercial 3.0 United States

subject: till geochemistry

subject: indicator minerals

subject: mineral exploration in glaciated terrain

abstract: The increasing difficulty of finding near-surface mineral deposits in glaciated terrain requires modification of conventional exploration techniques (drift prospecting) that can assist in exploring for deposits buried under glacial sediment cover of variable thickness. To address this challenge, a humus and soil (developed in till; “C-horizon till”) sampling study was conducted in the Drury and Denison townships in the South Range of the Sudbury Igneous Complex (SIC) to develop surficial mineral exploration techniques that are suitable for low sulfide, high precious metal (LSHPM) and massive sulfide Ni-Cu-PGE mineralization. The objectives of this project were to assess the suitability of humus and till for delineating geochemical anomalies in an established mining camp (the Sudbury Mining Camp) and characterize the chemistry of chalcopyrite, pentlandite and sperrylite grains in till derived from LSHPM (the Vermilion Cu-Ni-PGE-Au deposit) and Ni-Cu-PGE (the Crean Hill deposit) mineralization. Results of this study suggest that the natural geochemical signature of humus in the Sudbury Mining Camp is strongly overprinted by anthropogenic contamination such that the geogenic signal is only apparent in humus samples collected in the vicinity of known Ni-Cu-PGE mineralization. Glacial dispersal from Ni-Cu-PGE mineralization is apparent in C-horizon till and compared to the background (up-ice) concentrations, the C-horizon till samples collected immediately down-ice of the Vermilion deposit are enriched over 20 times in Pt, Au, and Cu, and over 30 times in Ni. Pathfinder elements that show a strong, positive correlation with Ni, Cu, Au, and PGEs (Pt, Pd, Ru, Rh, and Ir), that are also derived from LSHPM and Ni-Cu-PGE mineralization are As, Bi, Co, Cr, Pb, Sb, and Te. Ore minerals that survive glacial transport and post-glacial weathering and are the best indicators of Ni-Cu-PGE-Au mineralization are chalcopyrite, sperrylite, and gold grains. Glacial modification of ore minerals is limited to physical comminution and does not affect their chemical composition. Precious metals are detected in ore minerals derived from LSHPM mineralization. These consist of Ag, Au, Ir, and Pt in chalcopyrite, Ag, Au, Pt, Pd, Rh, and Ru in pentlandite and Ag, Au, Ir, Pd, Rh, and Ru in sperrylite.

abstract: PhD


title: Methods for Low Footprint Intrusion Detection Using Ensemble Learning

contributor:
Zulkernine, Mohammad
Computing

subject:
Intrusion Detection
Ensemble Learning
Machine Learning
Anomaly Detection
Low Footprint Intrusion

abstract:
Machine learning has rapidly become the state-of-the-art solution to problems in many areas of computing such as vision and natural language processing. In the intrusion detection domain, machine learning-based techniques have also been used in academia and industry in order to detect anomalies in network traffic. There are practical limitations, however, in using machine learning techniques in real-world intrusion detection systems as opposed to some other domains.

In this thesis, we present methods for low footprint intrusion detection using ensemble learning. We identify the cloud attributes that can be exploited in order to exacerbate intrusions on the cloud. We define low footprint intrusions as specific attacks that do not transfer volumetric data to or from a target machine and may be exacerbated by the cloud. By being stealthier than volumetric attacks, low footprint intrusions can go under the radar of traditional intrusion detection systems.

This research analyzes different methods of ensemble learning and presents ensemble models that achieve very high accuracy and very low error rates in detecting low footprint intrusions. We show that these models combine base machine learning classifiers that individually do not perform on par with the ensemble learners. However, by bringing more diversity, the base learners enable the ensemble model to gain high-performance results.

This research shows that among hundreds of ensemble models from a number of base learners only a few multi-layer stacking ensemble models  satisfy strict classification performance criteria. This is achieved by carefully crafting the ensemble models by considering different weights, choice of base and meta learners, hyperparameters, placement of learners, combination methods, and architectures.

We simulate and launch low footprint intrusions from virtual machines on Amazon Web Services (AWS). We show that low footprint intrusions can be easily launched from public clouds against targets outside of the cloud. We have implemented our data processing, machine learning models, and evaluation techniques using open-source machine learning libraries in Java (Weka) and Python (scikit-learn).

abstract: PhD


title: Combined Purification and Crystal Growth of CsPbBr3 by Modified Zone Refining

contributor:
Wang, Peng
Chemistry

subject:
Ionizing radiation detection
Halide perovskites
Photoresponse
Semiconductor detectors
Zone refining
CsPbBr3
Crystal growth

abstract:
Semiconductor-based ionizing radiation detectors at room temperature have been widely applied in national security, medical imaging, and scientific research. Current commercially available detector materials such as cadmium zinc telluride (CdZnTe) and thallium bromide (TlBr) still suffer from some drawbacks, including structural defects and chemical instability. Therefore, researchers have continuously explored alternative high-performance and low-cost radiation detection materials. The all-inorganic semiconducting perovskite cesium lead bromide, CsPbBr3, exhibits promising properties for ionizing radiation detection applications and has attracted extensive research attention in recent decades.

To achieve the high purity required for semiconducting detector operations, conventional growth procedures for CsPbBr3 single crystals typically involved the separate purification of precursor materials. Purified PbBr2 and CsBr were subsequently combined in a new reaction vessel for synthesis and crystal growth. The novelty of this work is the development of a set of reliable protocols that can combine the purification and the crystal growth into a continuous process in a single reaction vessel via modified zone refining to achieve higher production efficiency. In this work, a series of CsPbBr3 samples with different growth histories were obtained through this protocol. Polycrystalline CsPbBr3 was first synthesized from the melt of binary compounds CsBr and PbBr2. Moisture and oxides in the synthesized CsPbBr3 compounds were removed by a reduction process under a flowing hydrogen stream. The CsPbBr3 materials were then purified and grown into high-quality single crystals via the modified zone refining process.

Obtained crystals were subjected to several characterizations such as powder X-ray diffraction analysis, trace impurity level determination and elemental composition identification. Moreover, photo-electrical properties of CsPbBr3 samples were evaluated through characteristic current-voltage (I-V) tests and photoresponse measurements. Obtained single crystals exhibited an electrical resistivity within a range of 10^8~10^9 Ω·cm, meeting the requirement of high resistivity for detector materials. Different samples displayed different photoresponse performances, which can be used to guide future crystal preparation to produce single crystals with a high signal-to-noise ratio (SNR) under the illumination of a light source.

abstract: M.Sc.


title: Training Deep Neural Networks and Solving Differential Equations using Neuromorphic Photonics

contributor: Physics, Engineering Physics and Astronomy

subject:
Neuromorphic Photonics
Machine Learning
Silicon Photonics

abstract: In recent years, the use of integrated photonic systems for information processing has gathered significant interest as an alternative to conventional electronic computer architectures. The emerging field of neuromorphic photonics proposes to implement high-performance neural networks and related machine learning algorithms using electro-optic circuits, as these applications require high bandwidth, low latency, and low energy consumption. In this thesis, we present a novel photonic architecture for training neural networks on-chip using the direct feedback alignment algorithm. The architecture can operate at speeds of trillions of multiply-accumulate (MAC) operations per second while consuming less than one picojoule per MAC operation. We also introduce and simulate a photonic architecture for solving ordinary and partial differential equations using recurrent neural networks. Finally, we introduce a new computational method for self-consistent electrodynamics simulations of Lorentz oscillators and moving point charges, which can be integrated with neuromorphic photonics to harness potential improvements in speed and power when solving the simulation's governing differential equations. The high energy efficiency and operation speed of neuromorphic photonics could enable the development of innovative neural network applications that would be impossible to operate on current generation hardware.

abstract: M.A.Sc.


title: Numerical and Experimental Investigation of Punching Shear of Slab-Column Connections Retrofitted with Ultra High Performance Fibre Reinforced Concrete (UHPFRC)

contributor:
Genikomsou, Aikaterini
Civil Engineering

subject:
Punching shear
Slab-column connections
UHPFRC
Retrofit applications
Composite sections

abstract:
Punching shear is described as a brittle failure mode that can occur in reinforced concrete buildings at the slab-column connection area. Many times, such a failure mode can initiate a potential progressive collapse of the building. An in-depth investigation was performed to examine possible structural failures of flat slab construction, as well as research punching shear both experimentally and numerically. This included validated Finite Element Analysis (FEA) models and a planned proposed retrofit method to strengthen the slab, promoting improved serviceability and resilience.
A proposed retrofit method of using Ultra High Performance Fibre Reinforced Concrete (UHPFRC) as a tensile overlay was suggested for a square slab with side lengths of 1.8m and a thickness of 120mm, having extended square column stubs with side lengths of 200mm. Two slabs were constructed, including a control specimen (un-retrofitted) and a 30mm full tensile overlay retrofitted specimen with UHPFRC. Two more slabs are planned to be constructed, with all four being tested in future research. These additional two slabs will have full overlay thicknesses of 15mm and 20mm.
FEA models were established and analyzed for all proposed slabs. All FEA were conducted in ABAQUS software using the concrete damaged plasticity model. Another FEA software was also considered (ATENA), but the obtained results were not in good agreement with test results. ABAQUS results showed that an increase of thickness provided greater punching shear strength. The control specimen was compared to code provisions to validate accuracy. It was found that ACI-318-19 proved to be most accurate, whereas CSA A23.3-19 was one of the least accurate.
To model the constitutive behaviour of UHPFRC, emphasis was given to the tensile properties using the inverse analysis equations proposed in the recent Canadian codes (CSA A23.1-19 and CSA S6-19). A series of parametric studies were performed, varying model parameters using stress-strain or stress-crack width properties and the inclusion of damage. It was concluded that the stress-crack width provided better results for the post-peak softening along with the damage parameters compared to prism test results; however, the peak load was found to be greatly overestimated.

abstract: M.A.Sc.


title: “A Ruin, More or Less, or a Place of Dark Nostalgia”:  Prison Tourism and the Mobilization of Dark Heritage at Kingston Penitentiary

contributor:
Brison, Jeffrey
Jessup, Lynda
Cultural Studies

subject:
Dark tourism
Prison tourism
Penal heritage
Creative economy
Kingston Penitentiary
Exhibitions
Cultural diplomacy
Meta-soft power
Contact zones
Cultural Studies
Place-branding
Brian Jungen
Geoffrey James

abstract: Through case studies of the St. Lawrence Parks Commission’s Kingston Pen Tours and other prison-themed heritage and art exhibitions, this research project examines the phenomenon of “dark tourism,” defined as the act of travel to places associated with death and suffering. This project analyzes the ways that Kingston’s penitentiary history exists at the intersection of dark heritage tourism, place branding, and cultural diplomacy and how Kingston’s penitentiary heritage has been utilized through tourism and exhibitions to enhance, rather than undermine, the region’s image and attractiveness through the accumulation of “meta-soft power.” By considering which (and whose) stories are privileged in local prison heritage curation and promotion and why, this research questions how the City of Kingston and its local stakeholders have managed and controlled the region’s dark heritage as “Canada’s Penitentiary Capital” and mobilized it to promote local tourism and serve political agendas. This project also examines the ways that “unofficial” or counter-hegemonic representations of penal heritage in contemporary art exhibitions create opportunities for greater honesty, nuance, and critique in the narratives that are disseminated. These narratives challenge how the public thinks about incarceration and those who are incarcerated and possess the potential to spark social and institutional change. Finally, this research calls for greater inclusion, consultation, and collaboration with incarcerated communities and other groups affected by the justice system at penal heritage sites, such as the Kingston Pen Tours. In so doing, these sites would better realize their potential as “contact zones,” spaces of collaboration, consultation, and contestation between and amongst different cultures. Ultimately, this project recommends the adoption of an agonistic curatorial approach in the Kingston Pen Tours and other penal heritage sites.

abstract: PhD


title: A flexible framework for semi-automatic inverse planning of abdominal organ tumor ablation

subject: Image guided therapy

abstract:
Globally, the fourth most common cause of cancer related death is hepatocellular carcinoma (HCC). The first line treatments for HCC are surgical, including the gold standard treatments, liver transplantation and surgical lobectomy. However, both treatments are invasive and require long recovery times. Access to liver transplantation is further restricted by the limited availability of transplantable organs, and roughly 80% of patients are ineligible for either surgical treatment due to reduced liver function or other comorbidities. For this large group of patients, the best remaining options are locoregional therapies, most commonly radiofrequency or microwave ablation.

Procedure planning for ablations of small tumors can be accomplished using the standard tools included with many DICOM viewers. However, to treat larger tumors multi-needle treatment plans are becoming more common. Planning for multi-needle procedures is difficult due to challenges visualizing thermal dose regions while simultaneously considering anatomical restrictions on needle placement. Therefore, planning for these procedures is subject to inter- clinician variability and is dependent on the treating clinician’s experience with the procedure.

This work develops a library called ABPlan (the Ablation Planner) to support clinicians in the planning of ablative treatments. The library is designed to support semi-automatic inverse needle planning, where the clinician defines the treatment region, and the software provides assistance in selecting trajectories to treat this region. ABPlan is focused is on being efficient, and flexible enough to support a variety of planning scenarios and future improvements. This document presents the architecture of ABPlan, followed by an example integration of the library into the 3D Slicer platform for medical image computing.

abstract: M.Sc.


title: Automated Mineralogical Analysis of <250 µm Heavy Minerals in Till: Method Development and Case Study

subject:
Geology
Mineral exploration
Applied geochemistry
Drift exploration
Indicator minerals
Heavy mineral concentrates
Automated mineralogy

abstract:
Exploration under glacial sediment cover is a necessary part of modern mineral exploration in Canada. Traditional indicator methods use visual examination to identify mineral grains in the 250 to 2000 µm fraction of till heavy-mineral concentrates (HMC). This study tests automated mineralogical methods using scanning electron microscopy to identify indicator minerals in the fine (<250 µm) HMC fraction of till. Automated mineralogy of polished grains from the fine HMC enables rapid data collection (10,000–300,000 grains/sample). Samples collected near three deposits were used to test this method: 4 from the upper amphibolite Izok Lake volcanogenic massive sulfide deposit, Nunavut, 5 from the Sisson granite-hosted W-Mo deposit, New Brunswick, and 4 from the Triple B kimberlite, Ontario.
The less than 250 µm HMC fraction of till samples collected down-ice of each deposit contain ore and alteration minerals typical of their deposit type. Sulfide minerals occur mainly as inclusions in oxidation-resistant minerals, including minerals previously identified in the metamorphic alteration halo of each deposit, and are found to occur farther down-ice than the grains identified visually in the greater than 250 µm HMC fraction. Minerals that are traditionally difficult to identify using visual identification are easily discriminated by composition. The classic suite of kimberlite indicator suite is fully identified, and energy dispersive X-ray spectroscopy enables discrimination of compositional sub-populations without the use of more expensive/time consuming targeted chemical analysis techniques. This project developed a workflow for analyzing <250 µm HMC with automated mineralogy that is reproducible and relatable both within and between studies. The method described expands the detectable footprint for certain indicator minerals, identifies new indicator minerals, and enhances the information on the mineralogical composition of till samples that can be collected from till samples.

abstract: PhD


title: Numerical Investigation of Hyporheic Flows Induced by Gravel Bars and Sand Dunes

subject:
Hyporheic Flows
Gravel Bars
Sand Dunes
Empirical equations
Nonlinear Multiregression Analysis

abstract:
Existence of gravel bars and sand dunes in river streams results in exchange of flow across the interface of stream flow and porous medium known as hyporheic flow. This type of flow conveys solutes and nutrients to the riprapian organisms living in the hyporheic zone, and in case of river contamination they can be the main mechanism of contaminating the habitat of aquatic organisms. Therefore, it is critical to understand the mechanics of hyporheic flows induced by bed forms, and develop methods and tools for estimating their characteristics. This thesis is intended as a contribution to these ends.

In this study, the main effort has been made to develop a 3-D fully coupled numerical model capable of simulating the hyporheic flows both in turbulent and laminar flow regimes, while treating the interface between streamflow and porous medium as a permeable wall. The work involves an extensive series of numerical simulations conducted for different ranges of bed form geometry, permeability of porous materials and depth of alluvium, which are the key parameters controlling the characteristics of hyporheic flows. Predictive equations are developed for estimating the discharge, average velocity and average residence time in the hyporheic zones induced by a single gravel bar, a sequence of bars, and a sequence of dunes.

It is found that by applying a combination of Wall and Cyclic boundary conditions on the interface between streamflow and porous medium, the effects of the permeable wall on both surface and hyporheic flow fields is simulated very well. Comparison between the simulated data and their predicted counterparts by the empirical equations for the hyporheic flows induced by a single gravel bar revealed that in more than 80% of the cases, the error is within 10% error range. Due to the more complex nature of the hyporheic flows induced by a sequence of gravel bars and sand dunes the accuracy of the developed predictive equations is less than the ones developed for hyporheic flows induced by a single gravel bar. However, the equations are still very good in estimating the characteristics of hyporheic flows.

abstract: PhD


title: Self-witnessing Coherent Imaging for Automatic Noise Filtering and Artifact Removal in Laser Process Monitoring

subject:
Laser Keyhole Welding
In Operando Monitoring
High-Speed Depth Measurement
Inline Coherent Imaging (ICI)
Optical Coherence Tomography (OCT)

abstract: High-power lasers are rapidly becoming standard tools in advanced manufacturing, mainly in the form of laser welding, laser cutting, and laser additive manufacturing. Of these applications, laser welding in the electric mobility sector—particularly in the manufacturing of battery packs—presents unique challenges. Weld depth needs to be precisely controlled to ensure joint strength and to ensure the weld does not puncture into the lithium ion cell. These processes often involve highly reflective metals (such as copper), which have material properties that lead to unstable welds; this requires an unprecedented level of control to ensure weld quality and depth. To ensure weld quality, we need in-line monitoring during the process. Inline Coherent Imaging (ICI) is a process monitoring technique that has been demonstrated to measure keyhole depth (down to 15 µm axial resolution) at high camera rates ( 200 kHz), with unparalleled sensitivity and dynamic range. Unfortunately, it suffers from sources of noise such as speckle and imaging artifacts that can pose a significant challenge to quality assurance and closed-loop control. To mitigate these problems, I have integrated a second, automatically synchronized, imaging channel into a standard ICI system, by exploiting a previously unused part of the imaging window. This “witness” image makes it possible to identify real signal based on correlation and filter out the uncorrelated noise. This has allowed feature-identification intensity threshold values to be lowered from 12 dB to 8 dB. Using this system, we have demonstrated the complete removal of autocorrelation artifacts with no loss of imaging rate or spatial resolution compared to standard ICI. Between the first and second design for this technique, stability in the system increased by a factor of 12. When applied to imaging laser keyhole welding, I see improvements in the effective imaging rate of up to 79% relative to standard ICI for spot welds performed over 30 ms on 1000 series aluminum at 1100 W.

abstract: M.A.Sc.


title: Design Optimization of Aircraft Landing System Rolling Stock and Bogie

contributor:
Kim, Il Yong
Mechanical and Materials Engineering

subject: Gaussian Process Regression

abstract:
With the rapid development in the aircraft designs of the aerospace industry, the traditional select and pick design routine needs to be developed and improved and a new design methodology with fewer iterations must be proposed to meet all design metrics. This research aims to develop a method that designs the landing gear rolling stock and bogie configuration for the preliminary design stage, which integrates a high-fidelity multidisciplinary design optimization and Gaussian Process Regression techniques focusing on weight minimization, structure and configuration optimization. The overall design optimization process is wrapped in NASA OpenMDAO open source framework and contains four analysis subsystems: tire selection analysis, flotation analysis, brakes and wheels analysis, and structural linking beams analysis.
In the tire selection analysis, the radial tire is represented by using four continuous design variables and Gaussian Process Regression is used to do the metamodeling based on the known tire data. In the flotation analysis, the unpaved airfield compatibility analysis is conducted to make sure the aircraft can operate on the required runway. In the brakes and wheels analysis, the required brake size is calculated based on the kinetic energy of the landing or rejected takeoff and the mass of brake assembly and wheel are estimated based on the empirical equations. In the structural linking beams analysis, the dimensions of each tube are computed based on the loading case and safety margins are defined by the user. The mass of each tube is added up to be the total structural mass. The overall mass of the landing gear consists of tire mass, brakes assembly mass, wheels mass, and structural mass. It should be noted that the safety margins refer to the safety factors minus 1 in this study.
Finally, by implementing the case studies on A320-200 landing gear, the capability and feasibility of the proposed methodology have been demonstrated with several optimized solutions under different constraint conditions. If the same constraint conditions as the original design are considered as re-design 4, the total weight can be reduced by 10%. If loose constraint conditions are considered, the weight can be reduced up to 28.7%, 10.9%, and 10.7%, respectively as re-design 1, re-design 2, and re-design 3.

abstract: M.Sc.


title: Perceptions of School Administrators and Early Career Teachers Regarding Questions Used to Prompt Reflection on Practice

contributor:
Kutsyuruba, Benjamin
Education

subject:
Education
Coaching
Mentorship
Reflective practice

abstract: Traditional professional development (PD) for teachers has often been offered in a sitand- get format (Toll, 2018). Unfortunately, this model has removed educators from their classrooms while providing teachers with short, non contextualized information delivered through a workshop or class (Russo, 2004). To respond to this issue, the coaching model for PD has become a frequently adopted method in today’s modern classrooms (York-Barr, 2006). In fact, this form of job-embedded PD has often been used to help activate reflective practice among teachers through guiding (reflective) open-ended questions posed by the coach to the coachee. It is still unclear how this coaching model and its reflective questions are perceived by key stakeholders in educational settings. School administrators often assume the role of coach in elementary and secondary school settings (Toll, 2018), especially when coaching early career teachers (ECTs). In this multiple case study, the researcher explored the integration of guiding questions used by school administrators in their coaching strategies while focusing on the perceptions of Ontario’s school administrators and ECTs regarding the use of reflective questions in principal-to-teacher coaching methods. The researcher explored what school administrators and ECTs identify as the benefits to the coaching model of PD, as well as the barriers associated with this coaching model. For this study, a school administrator and ECTs in two schools were interviewed to better understand their perceptions of the model in a comprehensive manner. Data from the interviews were transcribed and analyzed using an inductive coding approach, which revealed common themes. These themes then converged, leading to a clear view of the perspectives of ECTs and school administrators with regards to the coaching model for PD, specifically while using reflective questioning. This research is important to the world of education, as it provides insight into the reflective coaching model for PD that has been adopted by some school administrators in Canada.

abstract: M.Ed.


title: Toll-Like Receptor 2 and the Early Chronic Inflammatory and Fibrotic Macrophage Response to Adsorbed Damage Associated Molecular Patterns

contributor:
Fitzpatrick, Lindsay
Chemical Engineering

subject: Macrophages

subject: Fibroblasts

subject: Damage associated molecular patterns (DAMPs)

subject: Toll-like receptor 2 (TLR2)

subject: Foreign body reaction

subject: Biomaterial host response

abstract:
The foreign body reaction (FBR) is an aberrant wound healing process that occurs in response to an implanted biomaterial, which can lead to the implant failing prematurely. Recently, damage-associated-molecular-patterns (DAMPs) were identified as potential contributing factors to the onset and progression of the FBR. DAMPs, released as a result of tissue damage, can stimulate an inflammatory response via interaction with pattern recognition receptors, such as Toll-like receptors (TLRs), on the surface of immune cells. Recently, our research group demonstrated that macrophages stimulated by DAMP-adsorbed biomaterials have increased NF-κB/AP-1 activity and cytokine expression at 20 hours, with TLR2 inhibition reducing these effects. This thesis examined the effects of adsorbed DAMP-induced TLR2 signaling on pro-inflammatory and profibrotic signaling in macrophages and its downstream effects on fibroblasts to better understand the early chronic inflammatory response associated with biomaterials. After 72 hours, macrophages cultured on DAMP-adsorbed TeflonTM AF surfaces had increased NF-κB/AP-1 activity and pro-inflammatory and profibrotic cytokine expression compared to serum-adsorbed TeflonTM AF, which was reduced in the presence of a TLR2 neutralizing antibody. After 120 hours, NF-κB/AP-1 activity and profibrotic cytokine expression remained elevated for macrophages cultured on DAMP-adsorbed TeflonTM AF relative to the negative control, and again TLR2 inhibition reduced these effects. In addition, fibroblasts cultured in conditioned medium from macrophages cultured on DAMP-adsorbed TeflonTM AF surfaces for 72 or 120 hours had increased gene and protein expression of α smooth muscle actin (αSMA) compared to fibroblasts in conditioned medium from serum-adsorbed TeflonTM AF surfaces. This αSMA expression was reduced for the conditioned medium of DAMP-stimulated macrophages treated with a TLR2 neutralizing antibody.
These results suggest that macrophages are still significantly activated by surface-adsorbed DAMPs at 72 and 120 hours and conditioned media from these cells could induce myofibroblast differentiation in fibroblasts. In addition, a single treatment with a TLR2 inhibitor for macrophages was sufficient to decrease the effects of adsorbed DAMPs at both 72 and 120 hours. However, the effects of both the adsorbed DAMPs and TLR2 inhibitor decreased over time in the macrophages, potentially due to paracrine signaling within the cultures overpowering the effects of the DAMP-signaling.

abstract: M.A.Sc.


title: Clustering Mass Spectrometry Data Using Variational Autoencoders

contributor:
Ellis, Randy
Computing

subject:
Machine Learning
Deep Learning
Mass Spectrometry

abstract:
Mass spectrometry is an analysis technique used to investigate the molecular profile of both biological and non-biological samples. Mass spectrometry imaging (MSI) allows for the spatial mapping of these molecules directly from a physical sample. Clinical applications of MSI are limited, in part because of the difficulty of analyzing the high-dimensional data that is produced. MSI images are commonly analyzed by reducing the dimensionality of the data and performing unsupervised analysis.

In this work, we analyzed MSI data by using a deep neural network composed of a variational autoencoder and a Gaussian mixture model. The model was trained to jointly optimize the latent space representation of the MSI data and the cluster
assignments within the latent space. We also used a path-based gradient-analysis method to determine the contribution of each analyzed molecule to its corresponding cluster. Our study demonstrated the robustness of the proposed method when compared to conventional MSI data-analysis methods. Our gradient-analysis method was able to discover patterns of molecules that had distribution throughout the samples which matched their corresponding cluster assignments.

abstract: M.Sc.


title: A Case for Utopian Dreaming: Feminisms within Canadian Artist-Run Centres

contributor:
Lord, Susan
Taunton, Carla
Art History

rights: Attribution-NonCommercial-ShareAlike 3.0 United States

subject:
Artist-run centres
Artist-run centre
Canadian feminist history
Institutional history
Canadian art history

abstract:
This dissertation is motivated by a set of questions elaborated from a central query: What is a flourishing future? When applied to the state of artist-run centre culture, and specifically feminist identified artist-run centres, in Canada, questions that follow include, who gets to represent futurity? Whose futures count? How are artist-run centres and art communities transformed by the inclusions of Indigenous and Black futures and futurism? How and by whom is feminism defined in these spaces? How does white feminism get out of the way of a flourishing future, or how doesn’t it? Throughout, I return to the concept of utopia as method, as proposed by Ruth Levitas. At its core, Levitas’s method comprises three simple steps: state the problem, attempt an archaeological dig of the past to shed insight into how we reached the problem, and then—and this is the key part—we are asked to educate our desires.
This grounding in utopian methodology leads me to specifically ask: how can artist-run centres benefit most from incorporating intersectional feminism and anti-oppression work into their daily operations? To think through this question, I consider a selection of historically feminist artist-run centres, active during the second wave of feminism to the present, to understand how they advanced specific feminist agendas, and to evaluate what kind of impact state policy and state funding priorities had on these artist-run centres. These include Mentoring Artists for Women’s Art (MAWA) in Winnipeg, Manitoba; Women in Focus Collective (WIF) in Vancouver, British Columbia; The Women’s Art Resource Centre (WARC) and the Feminist Art Gallery (FAG) in Toronto, Ontario; Womanspirit in London, Ontario; and La Centrale and articule in Montréal, Québec.

abstract: PhD


title: Bioavailability and Toxicity of Oil Trapped in River Sediments by Hyporheic Flows

contributor:
Hodson, Peter V
Brown, R Stephen
Environmental Studies

subject: Oil spills

subject: Toxic effects

subject: Hazard/risk assessment

subject: Dilbit

subject: Fluorescence spectroscopy

subject: Chemically enhanced water accommodated fraction

subject: EROD

subject: Embryotoxicity

subject: PAC

subject: Oiled substrate

subject: Diluted bitumen

subject: Droplets

subject: Hyporheic flows

subject: Oil

subject: Bioavailability

abstract:
Transportation of large volumes of oil in Canada increases the likelihood of inland oil spills and river contamination. In oil spills to rivers, turbulence may disperse floating oil into the water column and hyporheic flows may carry oil droplets through the bed sediments, including sediments utilized by fish for reproduction. Research is needed to measure the toxicity of oil stranded on and trapped within sediments to fish, including assessment of diluted bitumen (dilbit) products that are frequently transported across Canada. The objectives of this thesis were to measure the toxicity of dilbits to rainbow trout with commonly used laboratory toxicity test methods; to develop laboratory methods to model oil droplet entrainment in hyporheic flows; and to measure oil droplet trapping in gravel by hyporheic flows, dissolution of oil into water, and bioavailability to rainbow trout.

Research to address these objectives found that: Chemically dispersed dilbit and water flowing through gravel coated with dried films (dried oil films: DOF) of dilbit were chronically embryotoxic to rainbow trout alevins. Existing DOF methods were modified to assess oil droplet trapping in river gravels by hyporheic flows (trapped oil droplets: TOD). Increased oil mass loaded to or trapped in gravel (more trapping of higher viscosity oils) and increased oil surface area resulted in higher hydrocarbon concentrations in effluent. In DOF and TOD experiments, the concentration of hydrocarbons in water decreased over time, but the hydrocarbons were highly bioavailable to juvenile trout and were sustained at maximal levels over weeks of water flow.

These findings contribute to the understanding of the fate of oil in rivers and the exposure of organisms that inhabit the hyporheic zone. Embryo-larval fish chronically exposed to oil trapped in river sediments could cause lethal or sublethal effects that reduce the number of fish that survive to adult stages and successfully reproduce. Population reductions in subsequent years could threaten the sustainability of fisheries. It is recommended that the potential fate of oil in the hyporheic zone be included in risk assessments and oil spill response to prevent and mitigate oil contamination of river sediments.

abstract: PhD


title: Investigation of the Physical Mechanisms Behind the Deposition and Mobilization of Iron Oxide Particles on PVC Drinking Water Pipes

contributor:
Filion, Yves
Civil Engineering

subject:
Discolouration
Iron Oxide Particles
Particle Deposition
Drinking Water Pipes
Physical Mechanism

abstract: Material deposits, including metals and biofilms, are known to progressively accumulate inside drinking water distribution systems. Such accumulation increases the risk of drinking water contamination. Research suggests that iron oxide particles are the major component of material accumulation that are usually sourced by the corrosion of iron components in a distribution network and carried from the flow to other parts of the network. Despite the significant advances in identifying sediments and mitigating large discolouration events, the physical mechanisms of particle deposition and mobilization are still poorly understood, especially considering PVC pipe material. In this thesis, a series of controlled experiments using a full-scale drinking water distribution laboratory with PVC pipes are proposed to investigate the attachment and mobilization of iron oxide particles on PVC pipe walls of the system. Through the experiments, new monitoring techniques were designed to assess the fate of iron oxide particles within the pipes, including a method for direct quantification of iron oxide particles on the surface of undisturbed pipe wall samples using automated brightfield microscopy and image analysis. Experimental results produced new insights about: 1) the mechanisms behind the attachment of iron oxide particles to PVC pipe walls, which was dominant at the invert position of pipes and affected by the particles size, fluid velocity, and pipe wall roughness; 2) the origins of the shear strength of inorganic particle accumulation, that depends on the settling of particles in roughness “valleys” of the pipe wall roughness assisted by particle weight, and 3) particle mobilization dynamics during discolouration events, where the flow acceleration stage during flushing was observed to produce the dominant detachment of particulate materials. The research results have contributed to improving the understanding of early stages of particulate sediment accumulation on PVC drinking water pipes – a finding that might be key to developing proactive strategies to control the long-term buildup of sediment materials in operational networks and improve drinking water safety.

abstract: PhD


title: Quantification of Reynolds-averaged-Navier-Stokes Model Structural Hypothesis Uncertainty in Transitional Boundary Layer and Airfoil Flows

contributor:
Wu, Xiaohua
Rival, David E.
Mechanical and Materials Engineering

subject:
Marker function
Model structural hypothesis uncertainty
Software tool development in OpenFOAM
Transitional airfoil flow

abstract:
The Boussinesq turbulent-viscosity hypothesis is intrinsic to many Reynolds-averaged-Navier-Stokes (RANS)-based turbulence models and transition models. Although its drawback has been well acknowledged, the uncertainty it induces on RANS predictions of transitional flows has been ignored so far due to the conceptual complexity involved in the associated uncertainty quantification. This type of uncertainty is called the model structural hypothesis uncertainty.

In this thesis, a systematic uncertainty quantification study was carried out to estimate the RANS model structural uncertainties in predicting transitional flat-plate boundary layer and transitional airfoil flows. An existing uncertainty quantification framework for turbulent flow predictions is extended to the transitional flow regime in conjunction with a widely adopted RANS transitional model. This framework is physics-based without external high-fidelity data as input, and it decomposes the Reynolds stress tensor and inject perturbations to the amplitude, shape (eigenvalue) and orientation  (eigenvector) of the Reynolds stress tensor.

Given that neither the open-source OpenFOAM code nor commercial software packages contain uncertainty quantification modules, a tremendous amount of efforts in this research was spent on software tool development and successfully integrated the uncertainty quantification framework into OpenFOAM. Our software module can be used by the computational fluid dynamics communities worldwide to access the model structural hypothesis uncertainties.

This thesis reports the first contribution to the eigenvalue perturbations on a transitional boundary layer over a flat plate at three percent freestream turbulence intensity (T3A Case), and a transitional flow with separation bubble over the SD7003 airfoil at eight-degree of angle of attack. Eigenvalue perturbation was carried out through the barycentric map. For the T3A flow, most of the model structural hypothesis uncertainty was concentrated in the laminar-turbulent transition region. For the SD7003 flow, the reattachment point was well encompassed within the uncertainty bound.

The thesis also concerns with the amplitude perturbation, and we developed a novel marker function to identify the doubtful regions where uncertainties should be assessed. The uncertainty bounds for the skin friction coefficient, wall pressure coefficient, mean velocity field and Reynolds shear stress distribution have been successfully identified. These bounds offer crucially important information for design engineers and these data were not available prior to this study.

abstract: PhD


title: ReViSe: An End-to-End Framework for Remote Measurement of Vital Signs

contributor:
Zulkernine, Farhana
Computing

subject:
Vital signs measurement
Computer vision
Remote photoplethysmography
Deep learning

abstract: Photoplethysmography (PPG) is a fast, inexpensive and convenient method of collecting biometric data from fingertip videos. Remote Photoplethysmography (rPPG) is a contactless method to remotely calculate vital signs from facial videos. Post COVID-19 pandemic there has been a surge in online medical advising that requires monitoring of vitals at the remote location of the patient. This can be facilitated with the PPG and rPPG techniques which involves processing video frames to obtain skin pixels, extracting the cardiac data from it and applying signal processing filters to extract the Blood Volume Pulse (BVP) signal. Different algorithms are applied to the BVP signal to estimate the various vital signs. We implemented an end-to-end framework to measure a person's Heart Rate (HR), Heart Rate Variability (HRV), Oxygen Saturation (SpO2), Respiration Rate (RR), Blood Pressure (BP), and stress level from the face video using rPPG. The accuracy and robustness of the framework was validated with the help of volunteers whose vitals were also measured with medical devices. To protect user's privacy a face masking technique was employed. The rPPG technique is highly sensitive to illumination and motion variation which can lead to inaccurate results due to these factors. We analyzed the various factors that affect the results such as physical displacement of the person, facial movements, non-uniform illumination of the face regions, changes in light, and low light conditions. By displaying necessary messages to guide the user to reduce the noise and thereby the anomalies, a robust framework has been built which yields a cleaner BVP signal. We enhanced the existing PPG and rPPG models with an additional deep learning based BP estimation model. Due to the unavailability of a public dataset with videos and BP readings, this model was first trained on a public PPG dataset and then on self-created FingerVideo-BP and FaceVideo-BP datasets. On the FingerVideo-BP dataset the model gave a MAE of 10.3 mmHg and 8.2 mmHg, and on the FaceVideo-BP dataset a MAE of 7.9 mmHg and 5.8 mmHg for Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) respectively.

abstract: M.Sc.


title: Advancing Equity-Centered Research in Global Health: Exploring the Legacies of Colonialism in Global Health Research

contributor:
Bisung, Elijah
Kinesiology and Health Studies

subject: Global health

subject: Global health research

subject: Advancing equity centered research in global health

subject: Public health

subject: Health promotion

subject: Decolonizing global health research

subject: Decolonizing global health

subject: Legacies of colonialism in global health

subject: Colonial legacies in global health

subject: Equity-centered research

subject: Equity

subject: Tropical medicine

subject: Colonial medicine

subject: International health

subject: History of global health

abstract: Global health, as a field of research and practice, prioritizes some of the most pressing social and environmental challenges of our time including the health effects of climate change, response to emerging and re-emerging infectious diseases, and health inequities across the world. However, Western-dominated construction of health and disease diagnosis, as well as colonial ideologies within the field continues to reverberate in many circles. This research aims to explore the legacies of colonialism in global health research and investigate the methods and strategies used by researchers to address these legacies and advance equity. In-depth semi-structured interviews were conducted with participants (n=13) who self-identified as global health researchers from major Canadian and low-and-middle-income country (LMIC) universities (Afghanistan, Zambia, Kenya, Bangladesh, Ghana, and Indonesia). Factors such as gender, role, expertise, discipline, and geographic location were considered to ensure maximum variation in data collection. Six (6) LMIC participants and 7 Canadian participants were successfully recruited. Participants gave verbal consent to use a cloud-based video communications app, Zoom, to conduct interviews. Findings show that funding mechanisms, hierarchies, power imbalances, privilege and power, and local manifestations are some major legacies of colonialism in global health research. These legacies influence current research priorities, methodologies, and knowledge production mechanisms, as well as partnerships and collaborations in global health research. The methods and strategies used by researchers to address these colonial legacies comprise using community-based participatory action research (CBPAR), integrated knowledge-translation approach (IKT), capacity building, the Canadian Coalition of Global Health Research (CCGHR) Principles of Global Health Research framework, and other arts-based methods. In conclusion, it is important for researchers to become responsive to local realities while thinking critically about historical narratives to understand the political, social, and economic contexts in which global health research, programs, and partnerships occur. Decolonizing global health is difficult because the legacies of colonialism are deeply embedded with systems of knowledge production, global governance structures, and economic relationships between nations. However, we can address these issues at the institutional and individual levels by adopting and adapting the CCGHR Principles of Global Health Research, capacity building, and promoting South-South collaborations. This will ultimately lead to more equitable partnerships and collaborations and move towards decolonizing global health research.

abstract: M.A.


title: Life under an oil slick: response of a freshwater food web to simulated spills of diluted bitumen in mesocosms

contributor:
Orihel, Diane
Biology

subject:
oil spill
diluted bitumen
aquatic ecosystems
freshwater
phytoplankton
microbial

abstract: Heavy crude oil transportation over land is increasing, yet the ecological impacts of spills, particularly of diluted bitumen, in freshwater environments remain poorly understood. We simulated spills of diluted bitumen in 1400-L land-based mesocosms containing water and sediments from a boreal, oligotrophic lake and monitored the response of natural planktonic communities over 11 days. Most species of phytoplankton (chrysophytes and dinoflagellates) and zooplankton (copepods and cladocerans) were sensitive to oil, exhibiting >70% overall abundance reductions in response to the spills. Declines in nano- and micro-phytoplankton were short-lived and began to recover after the oil sank, whereas picophytoplankton and zooplankton populations remained depressed at the end of the experiment. In contrast, oil spills stimulated bacteria known to degrade hydrocarbons, especially Alphaproteobacteria, whereas Gammaprotobacteria—a common marine oil spill bacterial class—increased less. This is the first experiment to examine the effects of diluted bitumen in a multi-trophic level freshwater food web.

abstract: M.Sc.


title: Relationship to the Land (Use Planning Provisions): Mapping the Limitations of the Settler Imagination in an Arctic Anthropocene

contributor:
Hird, Myra
Environmental Studies

subject:
arctic
waste studies
settler colonial studies
critical GIS
research-creation
Nunavut
Nunavut land claims agreement

abstract: While legal scholars have applauded the Nunavut Land Claims Agreement (NLCA), which was the largest Indigenous land claim in Canadian history, as a watershed moment in Indigenous self-determination, the central role that resource extraction played in the negotiation and the final agreement is underexplored within the broader context of the colonization of Inuit in Canada. This thesis analyzes the central role non-renewable resources have played in the colonization of Inuit, from the surveys of the Geological Survey of Canada to the negotiation of the NLCA and how the entire frame for the NLCA had been predetermined by the settler colonial government of Canada, defined by settler ontologies of land that are legally supported by the Doctrine of Discovery. The three content chapters explore the tension between critical posthumanism and Indigenous ontologies, research-creation as a novel research method for exploring the contours of map making within a colonial context, and inhumanism as a theory for understanding colonial expansion using surveys, arguing throughout that understanding settler knowledges and ontologies of land is critical to understanding colonization and extraction in Nunavut. As such, this thesis interrogates settler-colonial conceptions of land through maps, the histories of settler territorial expansion in the Eastern Arctic through geological surveys, and how Inuit and settler ontologies of land and nonhuman matter diverge to argue that we cannot understand waste issues in Canada’s Arctic without understanding the foundational role of settler expropriation of land through geology.

abstract: M.E.S.


title: Time to Treatment of Esophageal Cancer in Ontario: A Population-Based Study

contributor:
Groome, Patti
Chung, Wiley
Public Health Sciences

subject:
Esophagus
Cancer
Time Intervals
Health Services Research
ICES

abstract:
Background: A patient’s journey from esophageal cancer diagnosis to treatment (treatment interval) is complex. They require numerous investigations and specialist visits before treatment can begin. Surgery is the cornerstone of treatment for resectable disease. Streamlining this pathway may shorten the treatment interval length, but this has not yet been studied in a contemporary Canadian cohort of patients with esophageal cancer. We aim to describe the length and geographical variation of the treatment interval (TI) by Local Health Integrated Networks (LHINs) and time to surgery (TTS) by Thoracic Cancer Surgery Centres (TCSCs) in Ontario, and identify factors associated with longer wait times.
Methods: We conducted a population-level study using health administrative databases in Ontario, Canada. We identified patients diagnosed with esophageal cancer between January 2013 and December 2018 who underwent treatment and had at least one staging investigation or specialist visit. TI length was defined as the number of days from the date of a biopsy to the first treatment. TTS length was measured in a subgroup of patients undergoing neoadjuvant chemoradiotherapy then surgery and was defined as the number of days from the date of a biopsy to the surgery date.  Univariate quantile regression was used to measure lengths at the median and 90th percentile, and multivariable quantile regression was used to identify associated factors.
Results: Of the 5,759 patients identified, median and 90th percentile TI length was 36 and 77 days, respectively. The difference between the LHIN with the longest and shortest TI at the 50th and 90th percentile was 18 and 25 days, respectively. Older age, higher comorbidity, higher material deprivation, rurality, and treatment group were associated with a longer TI. Of the 733 subgroup patients, median and 90th percentile TTS length was 140 and 171 days, respectively. The difference between the TCSC with the longest and shortest TTS at the 50th and 90th percentile was 31 and 22 days, respectively. Older age was associated with a longer TTS.
Conclusion: There is significant geographical variation in wait times to esophageal cancer treatment across the province. We have identified vulnerable patient populations at risk for protracted wait times.

abstract: M.Sc.


title: Examining the Neural Correlates of Peer Victimization and Peer Defending Using Functional Magnetic Resonance Imaging

contributor:
Craig, Wendy
Booij, Linda
Neuroscience Studies

subject:
Peer Victimization
Peer Defending
fMRI
Functional Connectivity

abstract:
Peer victimization is associated with psychosocial difficulties and mental health challenges. The neurobiological mechanisms underlying this association have yet to be fully understood. This dissertation is composed of three manuscripts that examine the relationship between peer victimization exposure, associated socioemotional factors, and the neural response to social exclusion.
The research described in the first manuscript (Chapter 2) used functional magnetic resonance imaging to compare the neural response to simulated social exclusion between first-year undergraduate students with a history of being peer victimized, those with a history of defending victimized peers, and those without prior exposure to peer victimization. Peer victimized students exhibited an increased neural response to simulated social exclusion compared to those without prior victimization exposure. This heightened response was observed in several brain regions that are involved in socioemotional processing, including the amygdala, inferior frontal operculum, parahippocampal gyrus, and fusiform gyrus.
To further investigate the interaction between peer victimization, depressive symptoms, and neural response to social exclusion, the research described in the second manuscript (Chapter 3) examined functional connectivity between the amygdala and medial prefrontal cortex while being socially excluded. Prior research has suggested that effective emotion regulation is facilitated by a negative functional connectivity between the amygdala and prefrontal cortex. The results described in Chapter 3 suggest that continuous functional connectivity between the amygdala and medial prefrontal cortex, across social inclusion and exclusion, moderates the relationship between peer victimization and depressive symptoms.
Finally, the research in the third manuscript (Chapter 4) focuses on the interaction between empathy, peer defending, and functional connectivity of brain regions involved in empathy-related processing. The results described in Chapter 4 show that functional connectivity while witnessing social exclusion of an unfamiliar peer moderates the association between empathy and peer defending. This finding suggests that the relationship between empathy and peer defending is associated with a coordinated response in brain regions involved in affective empathy and the facilitation of compassion via emotion-regulation (the amygdala and the orbitofrontal cortex, respectively). Taken together, the three manuscripts included in this dissertation advance our understanding of the neural correlates of peer victimization and peer defending.

abstract: PhD


title: Predicting the Influence of Hydrogen on Zirconium

contributor:
Daymond, Mark
Mechanical and Materials Engineering

subject:
Zirconium alloys
Zirconium hydride
Finite Element Modelling
Stress concentration
Hydrogen diffusion
Hysteresis
Precipitation models
CANDU Pressure Tube

abstract:
The corrosion process that ensues when the alloys of zirconium used as structural components and fuel claddings in nuclear reactors react with the heavy water used as coolant in the CANDU® reactors results in the production of hydrogen or deuterium. Some of this hydrogen enters the alloy and causes a gradual increase in the total hydrogen concentration from the initial average hydrogen concentration during fabrication. In addition to the gradients in temperature and concentration, the presence of stress raisers, such as cracks and blunt flaws influences the distribution of hydrogen as the concentration of mobile hydrogen in solution are preferentially increased at regions of localised high tensile stress. Hydride precipitates at these flaws when the solubility limit of hydrogen in the alloy is exceeded. A change of phase accompanies the precipitation of the brittle hydrides resulting in change in the mechanical properties of the alloy as well as additional strain due to volumetric expansion.
With the aid of Finite Element Analysis, this thesis describes models of the diffusion of hydrogen in response to gradients in stress, temperature, and concentration; the nucleation of hydride; and the growth of hydride. The commercial finite element code, ABAQUS® combined with subroutine codes written in FORTRAN are developed to fully couple the diffusion – displacement analysis. The fully – coupled hydride precipitation model which is not readily available in any commercial finite element package is robust, reliable, and readily parallelisable allowing for large models to be run while incorporating other complexities such as eigen strain, thermal strain, and creep.

abstract: PhD


title: UNDERSTANDING THE LEGISLATIVE PROCESS OF STRUCTURED INTERVENTION UNITS – CAN STRUCTURED INTERVENTION UNITS SUCESSFULLY TRANSFER FROM LAW INTO PRACTICE?

contributor:
Myers, Nicole
Sociology

subject:
Solitary Confinement
Administrative Segregation
Structured Intervention Units
Federal prisons
Canada
Bill C-83

abstract: Research indicates through perceptual and sensory deprivation as well as social isolation, including restrictions on a prisoner’s freedom of association, assembly and movement, solitary confinement leads to the creation, maintenance, and aggravation of mental and physical harms. Several legal challenges have been launched challenging the constitutionality of using solitary confinement, with two major court decisions in Ontario and British Columbia rendering solitary confinement unconstitutional. The Canadian government responded by introducing Structured Intervention Units (SIUs) through Bill C-83, eliminating solitary confinement in federal prisons. This thesis seeks to determine if SIUs can successfully transfer from policy into practice through analyzing the legislative process of SIUs. By performing a qualitative content analysis of various publicly available documents such as judicial decisions, House of Commons Debates, Senate Debates, their respective committees and stakeholder submissions three themes emerge. Meaningful contact, length of placement and oversight mechanisms are the themes which have been utilized to demonstrate the difficulty of successfully implementing SIUs at the institutional level. This work will set the stage for future research to examine the long-term impacts this policy change will have on those most affected. To determine if this is the best we can do or if more needs to be done to ensure offenders and frontline staff are provided with the proper tools and resources to successfully benefit from this new practice. Furthermore, this research is both important and timely to ensure the same harms evident with administrative segregation are not replicated under the new regime of SIUs.

abstract: M.A.


title: The Role of Affect and Trait Sexual Desire in Sexual Response among Women with and without Symptoms of Sexual Interest and Arousal Disorder

contributor:
Chivers, Meredith
Psychology

rights: Attribution-ShareAlike 3.0 United States

subject:
sexual psychophysiology
trait sexual desire
affect
Sexual Interest and Arousal Disorder
SIAD
women's sexuality

abstract: According to the Incentive Motivation Model, sexual cue processing is influenced by both responses to the content of sexual cues, and by individual psychological factors, both of which may result in differences in sexual response. Affect to sexual cues has been shown to affect sexual response in women with sexual dysfunctions, who have greater negative affect to sexual cues. The aim of the current study was (1) to examine the moderating role of trait sexual desire on the relationship between affect and sexual response, and (2) examine the differences between SIAD and unaffected women’s relationship between affect and sexual response. The current sample included 113 women, 31 of whom met SIAD criteria, and was comprised of data from two studies. In both studies, we measured self-reported sexual arousal (both continuous and discrete), self-reported state sexual desire, and self-reported affect. However, Study One used vaginal photoplethysmography to measure genital arousal, while Study Two used thermography. Thus, Study One and Study Two genital data was meta-analyzed. Contrary to hypotheses, there was no relationship between affect and genital arousal. There were, however, positive relationships between greater levels of positive affect and self-reported sexual arousal, as well as state sexual desire. There was no significant moderation of the relationship between affect and sexual response (either genital arousal or self-reported sexual response) by trait sexual desire. When presence of SIAD symptoms was included as a moderator, differences emerged between SIAD and unaffected women’s relationships between affect and sexual response. Namely, SIAD women did not have a significant relationship between affect and sexual response (self-reported arousal and state sexual desire), while unaffected women did. Overall, this thesis provides evidence for the importance in positive affect to sexual cues in SIAD women, which has treatment implications.

abstract: M.Sc.


title: Pink Triangles, Blue Feelings: Depression in Queer Contemporary Art

contributor:
Morehead, Allison
Silver, Erin
Cultural Studies

subject:
queer
trans
transgender
art
contemporary art
depression
mental health

abstract: In this dissertation, I explore how depression is represented, communicated, and/or articulated within queer contemporary art—that is, art created by Two-Spirit, Indig(e/i)queer, queer, and/or trans-identified artists or art that possesses a queer sensibility. Understanding depression simultaneously as a category of psychiatric diagnosis, a historically contingent discourse, and a short form for “bad feelings,” I consider how depression’s histories and contemporary iterations intersect with theories of queer and trans identity formation, the queer abject, gay shame, camp, queercrip temporalities, queercrip phenomenology, dominant popular and academic discourses of LGBT suicide, and various forms of social isolation during the COVID-19 pandemic. Anchoring these considerations in analyses of performances, video, paintings, drawings, sculptures, installations, photography, poetry, and agitprop produced primarily within the lands now called Canada and the United States, I seek to identify in these works what Gregg Bordowitz calls “queer structures of feeling”—that is, the cultural strategies that queer people have invented in order to survive, which leave their traces on subsequent generations of queer cultural production.

abstract: PhD


title: The Role of Financial Intelligence Units in Shaping and Effective International Anti-Money Laundering Law and Policy

contributor:
Cockfield, Arthur
Leuprecht, Christian
Robinson, Darryl
Law

subject: Financial intelligence units, anti-money laundering law, financial crimes, comparative study of selected national models of FIUs

abstract:
This thesis, by taking a comparative approach to study national models of Financial Intelligence Units (FIUs) from ten, selected, Western (Canada, Denmark, Netherlands, Luxembourg, United States) and Eastern (post-Soviet) countries (Estonia, Latvia, Lithuania, Poland, Ukraine), offers a critical assessment of the international, Anti Money Laundering (AML) law approach to fight money laundering.
Since the 1990’s, an international AML regime was set up, within which a crucial role was assigned to national FIUs, which is to gather, analyze, and disseminate financial intelligence. However, the AML regime does not seem to be working effectively, considering the numerous examples of banking scandals, including the recent, $200 billion Danske Bank case. Is this failure related to FIU function?
In this thesis, I propose the theory that the problem stems from a lack of appreciation, by the international and the EU AML frameworks, that tackling financial crime is a heavily endogenous and idiosyncratic endeavour. To be specific, it is possible that national and local non-legal factors shape the nature and efficacy of FIUs. Hence, the diverse structures and modus operandi of national FIUs may impact on their domestic functioning and cross-border cooperation, and this may impede the international efforts in tackling money laundering.  In addition, I speculate that there may be differences in FIU structure and function that are related to national, historical, social, and economic factors that define differences between Western and Eastern (post-Soviet) European countries.
The findings of my research are that FIUs are, indeed, substantially less homogenous than we could have expected because of the harmonization attempts. Part of their diversity can be characterized as ranging from a primarily administrative structure to a primarily law-enforcement one. Moreover, as suggested, FIUs do tend to cluster (with one telling exception) along an East-West dimension.  The characterization offered here is not an evaluation of FIU efficacy per se, but simply a clarification of their structures and modus operandi, which may lead to a better understanding of their efficacy in future studies. To make FIUs work effectively, identification of their idiosyncratic problems is needed first, because issuing new global AML standards is not a solution.

abstract: PhD


title: Chemical Analysis by Sessile Droplet Microfluidic Devices and Surface Sampling Probe Mass Spectrometry

contributor:
Oleschuk, Richard
Chemistry

subject:
Mass Spectrometry
Analytical Chemistry
Microfluidics
Electrospray Ionization
Mass Spectrometry Imaging
Spectrometer
Surgery
Perioperative
Automation

abstract: Is this tissue section cancerous or benign? Is this water safe to drink? Is the concentration of red blood cells in this sample sufficient? Those are just a few of many questions that the instrumentation, devices and methods developed within this thesis attempt to answer. Numerous quantitative and qualitative analytical chemistry techniques are utilized in billions of tests daily to answer a wide range of questions. Some methods require highly experienced personnel and advanced infrastructure, while others are cost-effective, portable, and easy to perform. With the COVID-19 pandemic, people worldwide became familiar with different types of tests to determine whether an individual is infected. Rapid antigen tests are examples of fast, portable, and easy to use microfluidic devices but provide limited sensitivity and accuracy. First microfluidic devices that also allow for fast and easy-to-use “point-of-care” (PoC) analysis are described, such as a sessile droplet microfluidic device to analyze cadmium in drinking water. The concept is extended with a microfluidic chip using fluid motion based on Young-Laplace-forces for viscosity measurements. Some analyses lend themselves to simple devices. However, more complex determinations and enhanced instrumentation can improve accuracy and sensitivities but require advanced laboratory equipment. An approach to reduce the costs of such tests while maintaining their accuracy and sensitivity is by increasing sample throughput and reducing the required personnel by automation of sample preparation and analysis. A self-built sampling stage for automated profiling of surfaces and its utility by chemically profiling cancerous kidney and liver tissue samples in conjunction with a surface sampling probe coupled to a mass spectrometer is presented. Lastly, the rapid surface wetting and droplet deposition devices are combined with the automated sampling stage. A microfluidic approach is employed that uses discontinuous dewetting to accurately deposit and position droplets of defined volume on a calibration slide. The calibration slide can be prepared in seconds, eliminating the need to pipette and prepare many calibration solutions.

abstract: PhD


title: Atomistic Simulation of Radiation-induced Defects in Ni-based Systems

contributor:
Béland, Laurent Karim
Yao, Zhongwen
Mechanical and Materials Engineering

subject:
Atomistic simulations
Ni-based alloys

abstract:
Nickel (Ni)-based alloys show outstanding mechanical and physical properties at high temperatures and in corrosive environments. Therefore, Ni with measured additions of appropriate alloying elements would be a good structural material candidate for the next generation of nuclear reactors. One such example of particular interest in Canada deuterium uranium (CANDU) reactors is X-750 Ni-based spacer material, which is a modified 600 series alloy, strengthened by the addition of aluminum (Al) and titanium (Ti). However, such Ni and Ni-based alloys, when exposed to radiation under working conditions, form defects which ultimately degrade their mechanical properties. This dissertation addresses several questions with regards to point defect evolution in Ni and Ni-based alloys by employing atomistic scale modelling in order to understand and predict alloy performance in irradiated environments.

Presented in this manuscript format, the dissertation can be outlined as follows: all utilized atomistic techniques in this thesis are explained in Chapter 2. Chapter 3 identifies the role of self interstitial atoms (SIAs) in the re-ordering of disordered Ni3Al, and moreover an applicable model for mean-field rate-theories is also presented. Chapter 4 indicates the complexity of energy landscape on point defect diffusion and localized traps in Ni(x)Fe(1−x) (0 ≤ x ≤ 1) using an in-home AkMC code. A modified version of this code is used to study point defect transport properties in Ni-Fe-Cr ternary alloy systems (appendix A). Helium (He) bubble evolution in pure Ni system as a model for Ni-based alloys is studied and the role of different objects on bubble growth are discussed in Chapter 5. In the final chapter, the primary conclusions of these studies and future steps are explored.

abstract: PhD


title: Steady-State Modelling for Natural Gas Transport Network Optimization

contributor:
Li, Xiang
Chemical Engineering

subject:
Global Optimization
Mathematical Modelling
Energy Networks
Neural Networks
Mixed-Integer Linear Programming
Surrogate Modelling

abstract:
Natural gas is an essential global energy resource. Large volumes of gas are transported using transmission
pipelines and energized using compressors. Several operational optimization opportunities
arise due to the immense volume of transported gas. Hence minor improvements in the operating
conditions can have drastic economic effects. One such operating optimization problem, which is
the primary focus of this thesis, is the fuel cost minimization problem (FCMP). The FCMP seeks
to minimize the fuel consumption of compressors in a network while satisfying flow demand and
supply constraints. Current approaches to the FCMP emphasize the tractability of the pipeline and
compressor models but compromise their validity. As a result, the suggestions from such methods
are not actionable as they are either inaccurate or infeasible. This thesis addresses the issues in the
FCMP literature in two significant areas. First in the pipeline, and second in the compressor.

abstract: M.A.Sc.


title: Applications of CO2 in CO2-responsive foams and pyrochlore froth flotation

contributor:
Stubenrauch, Cosima Prof. Dr.
Jessop, Philip Prof. Dr.
Gibson, Charlotte, Prof. Dr.
Chemistry

subject:
Green Chemistry
Foams
Responsive foams
Pyrochlore flotation
CO2
Froth flotation

abstract:
Reduction of auxiliary substances which reduces waste is a main principle of green chemistry that this thesis deals with in two projects by using CO2: (1) CO2-switchable additives for controlled foam dissipation, and (2) the use of CO2 as a pH modifier in pyrochlore flotation.

The first project is a study of foams generated with the conventional surfactant tetradecyltrimethylammonium bromide C14TAB in the presence of the CO2-switchable additive N,N,-dimethylethanolamine (DMEA) or N,N,N’,N’-tetramethyl-1,4-butanediamine (TMBDA). The properties of foams generated with N2 and different additive-to-surfactant molar ratios were only influenced at a high additive-to-surfactant ratio of 10:1 for the additive TMBDA. Foams generated with CO2 are inherently less stable due to the higher solubility of CO2 and therefore faster coarsening, but even more so when the protonated additive was present. To determine if it is possible to induce a controlled foam decay through CO2, foams generated with N2 were subjected to CO2 after foam generation. Introducing CO2 from the top led to a fast foam decay even with a small additive-to-surfactant ratio of 1:1, compared to when no additive was present. The additive TMBDA contains two amine groups that can be protonated through the addition of CO2 and therefore disturbed the close packing of the surfactant which led to film rupture.

The second project compares the effect of CO2 used as an acid instead of HCl or oxalic acid in pyrochlore mineral flotation. In micro-flotation testing it was found that at a pH of 4, the use of CO2 led to recoveries of pyrochlore and the gangue minerals quartz and microcline that are comparable with the recovery achieved when oxalic acid or HCl are used. The promising outcome of the micro-flotation tests were replicated in a batch flotation setup with real ore. Results of the first rougher stage at a pH of 5.9 revealed that CO2 and HCl led to comparable concentrate compositions and recovery yields, whereas oxalic acid led to a higher pyrochlore grade in the concentrate. The use of CO2 in pyrochlore flotation was therefore possible, but the gangue mineral depressing effect of oxalic acid was not achieved with CO2.

abstract: M.Sc.