title: Model Averaging: Methods and Applications

contributor:
Racine, Jeffrey S.
Economics

subject:
Econometrics
Machine Learning

abstract:
This thesis focuses on a leading approach for handling model uncertainty: model averaging. I examine the performance of model averaging compared to conventional econometric methods and to more recent machine learning algorithms, and demonstrate how model averaging can be applied to empirical problems in economics. It comprises of three chapters.
Chapter 1 evaluates the relative performance of frequentist model averaging (FMA) to individual models, model selection, and three popular machine learning algorithms – bagging, boosting, and the post-lasso – in terms of their mean squared error (MSE). I find that model averaging performs well compared to these other methods in Monte Carlo simulations in the presence of model uncertainty. Additionally, using the National Longitudinal Survey, I use each method to estimate returns to education to demonstrate how easily model averaging can be adopted by empirical economists, with a novel emphasis on the set of candidate models that are averaged. This chapter makes three contributions: focusing on FMA rather than the more popular Bayesian model averaging; examining FMA compared to machine learning algorithms; and providing an illustrative application of FMA to empirical labour economics.
Chapter 2 expands on Chapter 1 by investigating different approaches for constructing a set of candidate models to be used in model averaging – an important, yet often over- looked step. Ideally, the candidate model set should balance model complexity, breadth, and computational efficiency. Three promising approaches – model screening, recursive partitioning-based algorithms, and methods that average over nonparametric models – are discussed and their relative performance in terms of MSE is assessed via simulations. Additionally, certain heuristics necessary for empirical researchers to employ the recommended approach for constructing the candidate model set in their own work are described in detail. Chapter 3 applies the methods discussed in depth in earlier chapters to currently timely microdata. I use model selection, model averaging, and the lasso along with data from the Canadian Labour Force Survey to determine which method is best suited for assessing the impacts of the COVID-19 pandemic on the employment of parents with young children in Canada. I compare each model and method using classification metrics, including correct classification rates and receiver operating characteristic curves. I find that the models selected by model selection and model averaging and the lasso model perform better in terms of classification compared to the simpler parametric model specifications that have recently appeared in the literature, which suggests that empirical researchers should consider statistical methods for the choice of model rather than relying on ad hoc selection. Additionally, I estimate the marginal effect of sex on the probability of being employed and find that the results differ in magnitude across models in an economically important way, as these
results could affect policies for post-pandemic recovery.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: This thesis focuses on model averaging, a leading approach for handling model uncertainty, which is the likelihood that one’s econometric model is incorrectly specified. I examine the performance of model averaging compared to conventional econometric methods and to more recent machine learning algorithms in simulations and applied settings, and show how easily model averaging can be applied to empirical problems in economics. This thesis makes a number of contributions to the literature. First, I focus on frequentist model averaging instead of Bayesian model averaging, which has been studied more extensively. Second, I use model averaging in empirical problems, such as estimating the returns to education and using model averaging with COVID-19 data. Third, I compare model averaging to machine learning, which is becoming more widely used in economics. Finally, I focus attention on different approaches for constructing the set of candidate models for model averaging, an important yet often overlooked step.


title: The influence of reported physical activity and and biological sex on carotid arterial distensibility in Canadians with diabetes

contributor:
MacDonald, Maureen
Kinesiology

subject:
arterial distensibility
diabetes
aging
sex differences
physical activity

abstract: Aging is associated with increases in carotid arterial stiffness and this process appears to be accelerated in older adults with diabetes. It is known that older adults with higher levels of physical activity (PA) tend to have lower arterial stiffness values compared to their more sedentary counterparts. Women typically experience an increase in arterial stiffness and cardiovascular events after menopause compared to older men. It is currently unknown whether a greater degree of physical activity modulates vascular aging in individuals with diabetes, and whether sex differences exist. This study examined arterial stiffness estimated from carotid artery ultrasound images and blood pressure data available from the Canadian Longitudinal Study on Aging (CLSA) baseline data set in participants with non-Type 1 diabetes. Arterial stiffness was expressed as carotid artery distensibility, a measure of local arterial stiffness and calculated as the relative change in arterial diameter for a given change in pressure. PA was assessed via the Physical Activity Scale for the Elderly (PASE), a brief and easily scored 12-item survey used to assess usual PA in adults 65 years and older. This study evaluated the association between known cardiovascular disease risk factors/markers and carotid artery distensibility and examined the influence of PA on arterial stiffness.  The influence of age and sex, while controlling for known cardiovascular disease risk factors and markers was examined in individuals with non-Type 1 diabetes. There was no main effect of PASE score on arterial distensibility before (P = 0.143) and after (P = 0.998) adjusting for known cardiovascular risk factors and markers, and there were no interactions between PASE and sex, or PASE and age. There was a main effect of age on arterial distensibility in both models (P=<0.001) and there was a main effect of sex on arterial distensibility in the final adjusted model only (P=0.040). These findings suggest that PASE is not predictive of arterial distensibility in older adults with non-Type 1 diabetes, and these results do not differ by age or sex. Follow-up analysis, using longitudinal models is required to further assess the influence of PA on vascular aging.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: It is well-known that aging is associated with increases in arterial stiffness, which is the progressive impairment of the ability of the arteries to respond to changes in blood pressure and flow.  Increased arterial stiffness is associated with the development of cardiovascular disease and appears to be accelerated in females and individuals with diabetes. Physical activity has been highlighted as a potential moderator of age-induced arterial stiffening. Healthy and physically active older adults typically display reduced arterial stiffening compared to their more sedentary counterparts, but the extent to which physical activity attenuates vascular stiffening in older adults with diabetes is unclear. Our results, from a cohort of approximately 2000 older Canadians with non-Type 1 diabetes, show that self-report physical activity level does not appear to be associated with arterial stiffness in this population, and these results do not differ by sex. Follow-up analysis should be conducted to assess the impact of physical activity over time on arterial stiffness in this population.


title: Applying Automatic Speech to Text in Academic Settings for the Deaf and Hard of Hearing

contributor:
Stroinska, Magda
Pape, Daniel
Cognitive Science of Language

subject:
Deaf
Hard of Hearing
Speech
recognition
captions
note taking
analysis
error
rate
accessibility
computational
phonetics
acoustics
speech-to-text
Otter
Ava
speech signal
speech perception
linguistics
language
lecture
transcription
intelligibility
academia
accuracy

abstract: This project discusses the importance of accurate note-taking for D/deaf and hard of hearing students who have accomodation requirements and offers innovative opportunities to improve the student experience in order to encourage more D/deaf and hard of hearing individuals to persue academia. It also includes a linguistic analysis of speech singals that correspond to  transcription output errors produced by speech-to-text programs, which can be utilized to advance and improve speech recognition systems.

abstract:
In hopes to encourage more D/deaf and hard of hearing (DHH) students to pursue academia, speech-to-text has been suggested to address notetaking issues. This research examined several transcripts created by two untrained speech-to-text programs, Ava and Otter, using 11 different speakers in academic contexts. Observations regarding functionality and error analysis are detailed in this thesis. This project has several objectives, including: 1) to outline how the DHH students’ experience differs from other note-taking needs; 2) to use linguistic analysis to understand how transcript accuracy converts to real-world use and to investigate why errors occur; and 3) to describe what needs to be addressed before assigning DHH students with a captioning service.
Results from a focus group showed that current notetaking services are problematic, and that automatic captioning may solve some issues, but some errors are detrimental as it is particularly difficult for DHH students to identify and fix errors within transcripts.
Transcripts produced by the programs were difficult to read, as outputs lacked accurate utterance breaks and contained poor punctuation. The captioning of scripted speech was more accurate than that of spontaneous speech for native and most non-native English speakers. An analysis of errors showed that some errors are less severe than others; in response, we offer an alternative way to view errors: as insignificant, obvious, or critical errors. Errors are caused by either the program’s inability to identify various items, such as word breaks, abbreviations, and numbers, or a blend of various speaker factors including: assimilation, vowel approximation, epenthesis, phoneme reduction, and overall intelligibility. Both programs worked best with intelligible speech, as measured by human perception. Speech rate trends were surprising: Otter seemed to prefer fast speech from native English speakers and Ava preferred, as expected, slow speech, but results differed between scripted and spontaneous speech. Correlations of accuracy and fundamental frequencies showed conflicting results. Some reasons for errors could not be determined without knowing more about how the systems were programed.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
In hopes to encourage more D/deaf and hard of hearing (DHH) students to pursue academia, automatic captioning has been suggested to address notetaking issues. Captioning programs use speech recognition (SR) technology to caption lectures in real-time and produce a transcript afterwards. This research examined several transcripts created by two untrained speech-to-text programs, Ava and Otter, using 11 different speakers. Observations regarding functionality and error analysis are detailed in this thesis. The project has several objectives: 1) to outline how the DHH students’ experience differs from other note-taking needs; 2) to use linguistic analysis to understand how transcript accuracy converts to real-world use and to investigate why errors occur; and 3) to describe what needs to be addressed before assigning DHH students with a captioning service.
Results from a focus group showed that current notetaking services are problematic, and that automatic captioning may solve some issues, but some types of errors are detrimental as it is particularly difficult for DHH students to identify and fix errors within transcripts.
Transcripts produced by the programs were difficult to read, as outputs contain poor punctuation and lack breaks between thoughts. Captioning of scripted speech was more accurate than that of spontaneous speech for native and most non-native English speakers; and an analysis of errors showed that some errors are less severe than others. In response, we offer an alternative way to view errors: as insignificant, obvious, or critical errors. Errors are caused by either the program’s inability to identify various items, such as word breaks, abbreviations, and numbers, or a blend of various speaker factors. Both programs worked best with intelligible speech; One seemed to prefer fast speech from native English speakers and the other preferred slow speech; a preference of male or female voices showed conflicting results. Some reasons for errors could not be determined, as one would have to observe how the systems were programed.


title: A STUDY OF SUPPORTS IN THE REDUCTION OF ACCULTURATIVE STRESS ON FIRST YEAR INTERNATIONAL STUDENTS

contributor:
Newbold, Bruce
Geography and Earth Sciences

subject:
Acculturative Stress
Acculturation
Higher Education
International Students

abstract:
Acculturative stress has a significant impact on any individual that experiences it.  This type of stress is felt specifically within various immigrant populations brought on by the differences (culture, language, systems, supports, etc.) from host nation to country of origin. The effects of acculturative stress can manifest psychologically, physiologically or as some combination of the two.
This research used an online survey and individual interviews to review and examine the current supports at Conestoga College in order to assess their role in reducing the impacts of acculturative stress in first year, full-time, international students. The data from the online survey (n= 57) and in-person interviews (n=16) determined that the majority of participants felt varying levels of acculturative stress after arriving to Canada for their program of study.  The data displayed that although the majority of students were aware of and accessed many of the supports provided by Conestoga College, it did not reduce the experiences of acculturative stress.  Four emergent themes were also revealed through the data; navigation, emotional impacts, independence and belonging which further contribute to the understanding of acculturative stress and the field of acculturation more broadly.  These emergent themes are ones which can be applied to a multitude of immigrant groups and can help to unify the field of acculturation.

abstract: Thesis

abstract: Master of Arts (MA)


title: Development of an Optimization Tool for the Geometry of Integrated Power Module Pin Fin Arrays Employed in Electrified Vehicles

contributor:
Emadi, Ali
Narimani, Mehdi
Electrical and Computer Engineering

subject:
Thermal Management
Pin Fins
Heat Transfer
CFD
Power Electronics
Inverters
Power Losses
Traction
Electrified Vehicles
Optimization

abstract:
The mass-market adoption of electrification in the transportation sector mandates stringent and aggressive requirements in terms of cost, power rating, efficiency, power density, and specific density of power electronics. Modular packaging of power electronics is advantageous and thus ubiquitously used by the automotive industry. A trend of shrinking die sizes and increased integration is evident and will inevitably continue. The thermal management system has become ever more significant as it is one of the main obstacles to higher power densities. The cooling system must be cost-effective, simple, efficient, reliable, and compatible with system requirements.

Pin fins are a reliable and effective means of augmenting heat transfer. They rely on inducing turbulence, increasing the effective wetted surface, and accelerating fluid velocity. Unavoidably the pin fin array also produces an undesirable pressure drop that is commensurate to the pumping power required for the system. In this thesis, a tool is developed for the geometry optimization of pin fin arrays to dissipate the heat at a rate large enough to ensure junction temperatures do not exceed the maximum value possible at a minimal pressure drop. It is hoped that this tool would contribute to the multi-physics optimization and integration of power electronics for electrified vehicles. This optimization is confined to equalaterally spaced short pin fins, aspect ratios less than three. The tool employs empirical correlations since flow is too complex to solve analytically and numerical solutions or CFD-simulations are too time and computationally extensive.

The tool development is done in a comprehensive manner. Starting from the first principles of a two-level voltage source inverter's operation. Next, the inevitable power losses from the operation are explained and a method for their calculations is presented. Correlations in the literature related to both pressure drop and heat transfer are reviewed afterward. Then the methodology of the construction of the tool is explicated in detail. Employing a commercial power module to benchmark results; three scenarios with different flow rates and inlet temperatures are optimized for. Simulations in ANSYS Fluent are run to verify the accuracy of correlations used in the tool. Comparing the optimized geometry of pin fins to the original benchmarking geometry it is evident that employing this tool on a per-application basis provides superior performance.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Putting the Name to the Face: Improving Name–face Memory Associations Through Concepts of Bizarreness and Production

contributor:
Monteiro, Sandra
Psychology

subject:
Memory
Name–face mnemonics

abstract:
Memory for names and faces is especially unpredictable. We have all experienced the embarrassment of failing to remember an individual’s name despite meeting them only minutes before. Many theories have been suggested to explain these frustrating moments (Burton & Bruce, 1993; O’Mahony & Newell, 2012). However, despite value of these theories, many neglect to explain how to improve name–face memory. Mnemonic devices are powerful memory aids that improve encoding and subsequent memory recall (McCabe et al., 2013). Given the effectiveness of mnemonics, name–face memory recall may be improved with a novel mnemonic device.
Previous research by Patel (M.Sc.) at McMaster University investigated one such mnemonic device: the house bunny effect (HBE). The HBE combines elements of the bizarreness effect (Cox & Wollen, 1981) and the production effect (Quinlan & Taylor, 2013) and predicts that repeating an individual’s name in a bizarre voice at the time of encoding (i.e., when meeting a new individual) improves name–face recall. However, contrary to this prediction, bizarre name production did not improve name–face memory recall compared to a normal voice production control. More importantly, a non-statistically significant trend in the opposite direction was observed—bizarre name production at the time of encoding hindered name–face memory recall (Patel, 2020).
Given this finding, we present two studies: an online conceptual replication of the HBE and a study that further elucidates the mechanisms behind the HBE. The results of these two studies will help determine how name–face memory is influenced by bizarre name production at the time of encoding (i.e., the HBE mnemonic).

abstract: Thesis

abstract: Master of Science (MSc)


title: Testing and Thermal Management System Design of an Ultra-Fast Charging Battery Module for Electric Vehicles

title: Battery Module Thermal Management System Design

contributor:
Emadi, Ali
Mechanical Engineering

subject:
electric vehicles
battery module
ultra-fast charging
thermal management system
battery testing
FEA thermal modeling

abstract: This thesis consists of three main objectives: fundamental and literature review of EV batteries, experimental development, and validation of two liquid cooling battery modules, thermal modeling and comparison of the inter-cell cooling battery module.

abstract:
The traditional vehicles with internal combustion engine have resulted in severe environmental pollution, which motivates the development of electric vehicles and hybrid electric vehicles. Due to a low energy density and long refueling time of the battery pack, it is still hard for electric vehicles and hybrid electric vehicles to be widely accepted by the consumers. As the batteries with a better ultra-fast charging capability are massively produced, the range anxiety issue is somewhat alleviated.
During a charging with large current magnitude, the battery generally has a great amount of heat generation and evident temperature rise. Therefore, a thermal management system is necessary to effectively dissipate the battery loss and minimize the degradation mechanisms caused by extreme temperature. The motivation of this thesis is to study the discipline of the battery thermal management system as an application for electric vehicles. The design methodologies are presented in both experiment test and numerical simulation.
For the comparative study between active liquid cooling methods for a lithium-ion battery module using experimental techniques, two battery modules with three Kokam Nickel Manganese Cobalt battery cells connected in parallel are developed. One has liquid coolant flowing along the edge of the model, and another with liquid coolant flowing between the cells. Several characterization tests, including thermal resistance tests, fast charging tests up to 5C, and drive cycle tests are designed and performed on the battery module. The inter-cell cooling module has a lower peak temperature rise and faster thermal response compared to the edge cooling module, i.e., 4.1⁰C peak temperature rise under 5C charging for inter-cell cooling method and 14.2⁰C for edge cooling method.
The thermal models built in ANSYS represent the numerical simulation of the inter-cell cooling module as a comparison with the experiment. A cell loss model is developed to calculate the battery heat generation rate under ultra-fast charging tests and a road trip test, which are further adopted as the inputs to the thermal models. The simulation of the 5C ultra-fast charging test gives the peak temperature rise just 0.47⁰C lower than the experimental measurement, it indicates that the FEA thermal models can provide an accurate temperature prediction of the battery module.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: With a demanding market of electric vehicles, battery technologies have grown rapidly in recent years. Among all the battery research topics, the development of ultra-fast charging, that can fully charge the battery pack within 15 minutes, is the most promising direction to address the range anxiety and improve the social acceptance of electric vehicles. Nevertheless, the application of ultra-fast charging has many challenges. In particular, an efficient thermal management system is significant to guarantee the safety and prolong the service life of the battery pack. This thesis contributes to study the fundamentals of the battery field, and design liquid cooling systems to observe the thermal behavior of a battery prototype module under fast charging and general use. FEA thermal modeling of the battery module is developed to provide a guide for further test validation.


title: ADVANCED CHARACTERIZATION OF BATTERY CELL DYNAMICS

contributor:
Habibi, Saeid
Mechanical Engineering

subject:
Batteries
State Estimation
Electrochemical Impedance Spectroscopy
Adaptive Filtering
Battery Aging
Deep Neural Networks

abstract:
Battery Electric Vehicles (BEV) are gaining market share but still must overcome several engineering challenges related to the lithium-ion battery packs powering them. The batteries must be carefully managed to optimize safety and performance. The estimation of battery states, which cannot be measured directly, is an important part of battery management and remains an active area of research since small gains in estimation accuracy can help reduce cost and increase BEV range.
This thesis presents several improvements to battery state estimation using different methods. Electrochemical Impedance Spectroscopy (EIS) is receiving increased attention from researchers as a method for state estimation and diagnostics for real-time applications. Due to battery relaxation behaviour, long rest times are commonly used before performing the EIS measurement. In this work, methods were developed to significantly shorten the required rest times, and a State of Health (SoH) estimation strategy was proposed by taking advantage of the relaxation effect as measured by EIS. This method was demonstrated to have an estimation error of below 1%.
At low temperatures, the accuracy of the battery model becomes poor due to the non-linear battery response to current. By using an adaptive filter called the Interacting Multiple Model (IMM) filter, the next part of this work showed how to significantly improve low temperature State of Charge (SoC) estimation. Further reduction in estimation errors was achieved by pairing the IMM with the Smooth Variable Structure Filter (SVSF), for SoC estimation errors below 2%.
The work presented in this thesis also includes the application of Deep Neural Networks (DNN) for SoC estimation from EIS data. Finally, an extensive aging study was conducted and an
accelerated protocol was compared to a realistic drive cycle based protocol using EIS as a characterization tool.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Replacing conventional gasoline/diesel powered cars with battery powered vehicles is part of a solution to the climate crisis. However, the initial costs paired with range anxiety stops many from switching to electric cars. Both cost and range are related to the battery pack. To achieve the best possible range for the lowest possible cost, battery packs must be carefully controlled by sophisticated algorithms. Unfortunately, battery range or health cannot be measured directly, but must be inferred through measurable indicators. This thesis explores battery behavior under different operating conditions and develops improved methods which can be used to determine battery health and/or range. A powerful method usually used only in laboratory settings is studied and improved to make it more suitable for implementation in electric cars. In this work it is used for accurate battery health determination. Furthermore, a strategy for improving battery range determination at low temperatures is also proposed.


title: Barriers and Strategies to Timely Nursing Registration for Internationally Educated Nurses: A Scoping Review

contributor:
Baumann, Andrea
Nursing

subject:
Internationally educated nurses
Barriers
Strategies
Registration
Scoping review

abstract:
Background: Internationally educated nurses (IENs) have become a significant source of nursing supply as a result of nursing workforce shortages, the aging population and patient acuity. However, IENs face substantial delays and barriers obtaining licensure and employment equivalent to their skills and experience. When IENs are unable to practice their profession, they experience a considerable loss of professional identity, earning potential and financial stability. The purpose of this scoping review was to identify and map key themes in the existing literature on the barriers and strategies to timely nursing registration for IENs.
Methods: Arksey and O’Malley’s methodological framework was used for this study. Seven electronic databases were searched along with several grey literature sources in order to capture articles that discussed barriers and strategies to timely nursing registration for IENs. A numerical and thematic analysis was conducted to explore the scope of the literature and to present the findings.
Results: After full-text screening, 38 pieces of relevant literature were selected for inclusion in the review. The majority (53%) were studies and most (42%) were qualitative. Seven key themes emerged from the thematic analysis: timely information, credential assessment, obtaining documents, language requirements, nursing registration costs, bridging programs and the nursing registration exam.
Conclusion: While some IENs are able to successfully navigate the process for obtaining nursing licensure, it is clear that many IENs face obstacles at every step of the process and some never become registered as nurses. Further research is required about whether the various bridging programs and initiatives meet the needs of IENs and help them become registered as nurses. Findings from this scoping review have significant implications for nurse staffing and policies and practices to improve the strength, stability, and diversity of the nursing workforce.

abstract: Thesis

abstract: Master of Science in Nursing (MSN)

abstract: This study explores the literature on internationally educated nurses (IENs) and the difficulties they face, as well as the strategies they use to obtain nursing registration. Arksey and O’Malley’s framework was used to guide this scoping review. Seven databases were searched along with many grey literature sources in order to find articles on barriers and strategies to nursing registration for IENs. A numerical and thematic analysis was conducted to present the findings. Seven main themes emerged from the thematic analysis: timely information, credential assessment, obtaining documents, language requirements, nursing registration costs, bridging programs and the nursing registration exam. More research is required about whether the various bridging programs and initiatives meet the needs of IENs and help them become registered as nurses. Findings from this study are important for nurse staffing and policies and practices to improve the stability and diversity of the nursing workforce.


title: Investigating Patterns of Growth and Development in Subadults from the 10th-13th Century Cemetery of St. Étienne de Toulouse, France

contributor:
Brickley, Megan
Anthropology

abstract: Growth and growth disruption are highly influenced by environmental factors such as nutritional intake, disease, and activity level. The purpose of this thesis is to investigate growth disruption in a medieval French subadult collection using femoral growth data as well as to examine developmental changes in midshaft geometry and cortical porosity. The femora of 94 subadults (fetal-12.49 years of age) from the 10th-13th century cemetery of Toulouse, France, were analyzed using macroscopic, radiographic, and microscopic techniques. Individuals were examined for growth disruption using endochondral and appositional growth, body mass estimates, cortical thickness, cortical pore volume, and Harris line data. Additionally, femoral cross-sectional geometry was used to examine ontogenetic changes in midshaft shape. Significant growth deficits were observed in the youngest individuals of this sample, especially in children 2.0-3.99 years of age. The prevalence of disrupted growth in the youngest individuals of this sample suggests that many children were likely born to malnourished mothers and provided nutritionally inadequate complementary foods during early development. These growth deficits, however, were largely ameliorated in older children and adolescents, indicating an improvement in nutrition and disease load. Ontogenetic changes in femoral midshaft geometry follow that of previous research, with young children (<4 years of age) having a more mediolaterally reinforced midshaft shape, indicative of an immature waddling gait. Increased midshaft porosity was experienced almost exclusively by infants and young children 0.5-1.49 years of age and was observed to be largely the result of trabecularized bone at the endosteal surface. The increased porosity likely results from the reorganization of bone stimulated by the onset of weight-bearing activity and increased growth velocity. This thesis contributes to the bioarchaeological literature by providing insight into the growth and development of children from medieval Toulouse and evidence of transient periods of increased cortical porosity during infancy.

abstract: Thesis

abstract: Master of Arts (MA)


title: Exploring the Relationships Between Liver Fat, Gut Microbiota, Serotonin, and Brown Adipose Tissue in Humans

contributor:
Steinberg, Gregory
Biochemistry and Biomedical Sciences

subject: Brown Adipose Tissue, NAFLD, MRI, Serotonin, Gut microbiota

abstract: Obesity is a growing problem that impacts both adults and children. Obesity is linked to the development of unfavorable health outcomes like excess fat accumulation in the liver, a problem known as non-alcoholic fatty liver disease (NAFLD). Brown adipose tissue (BAT), a thermogenic body fat that can be turned on by cold, produces heat by consuming circulating lipids and glucose in a futile cycle.  Less active cold-stimulated BAT is linked to obesity and type 2 diabetes in adults but whether this relationship exists in children is unknown. In rodents, increases in BAT activity are associated with reductions in NAFLD, effects that may be mediated through changes in the gut microbiome and reductions in peripheral serotonin. Whether the gut microbiome and serotonin play a role in regulating BAT activity in adults and children is not known. In this thesis, we have utilized magnetic resonance imaging (MRI) proton density fat fraction (PDFF) to assess BAT in the supraclavicular (SCV) region after three hours and one hour of whole-body cold exposure in adults and children, respectively. In 60 adults (aged 18-57 years), we examined whether there is a relationship between cold-stimulated BAT activity and liver fat (assessed via MRI) and whether gut microbiota plays a role in connecting these two tissues. In children, we investigated, BAT activity after whole-body cold exposure in 26 boys (aged 8-10 years). We also explored if BAT activity was different between boys with and without overweight/obesity. Finally, in young boys, we measured the levels of serotonin in platelet-poor plasma and its metabolic end product 5-hydroxyindole acetic acid (5-HIAA) in the urine. We explored if these measures of circulating serotonin were related to cold-stimulated BAT activity and if they were different between boys with and without overweight/obesity. The findings from this research indicate that higher cold-stimulated BAT activity is associated with lower liver fat in adults, but that this relationship is unlikely mediated through changes in the gut microbiota. Additionally, boys with overweight/obesity have lower cold-stimulated BAT activity and lower 5-HIAA in their urine compared to those with normal weight. Moreover, circulatory serotonin is negatively related to total adiposity. However, circulating serotonin is not related to cold-stimulated BAT activity in this cohort. These findings are important as they indicate for the first time that increasing BAT activity in adults and children could potentially be a new avenue for the treatment of NAFLD and obesity.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Obesity is a risk factor for the accumulation of extra liver fat, a problem known as non-alcoholic fatty liver disease (NAFLD). Brown adipose tissue (BAT) is a kind of body fat that rather than storing calories like white fat burns calories when switched on by cold.  Studies in adults have shown that people with obesity and type 2 diabetes have less active BAT suggesting switching it on may be helpful to promote weight loss and lower glucose. However, whether this relationship exists in children is not known. In rodents, increased BAT activity has also been linked to reductions in NAFLD, effects that might involve a hormone called serotonin, or changes in the gut microbiome but whether this is important in children and adults is also not understood.  In this thesis, we utilized magnetic resonance imaging (MRI) to examine BAT activity after whole-body cold exposure in adults (3 hours) and children (1 hour). In 60 adults (aged 18-57 years), we report that higher cold-stimulated BAT activity is linked to NAFLD, but gut microbiota does not seem to play a role in this relationship. In 26 boys (aged 8-10 years), BAT is less responsive to cold in boys with overweight/obesity compared to boys with normal weight. Additionally, serotonin is lower in boys with overweight/obesity compared to boys with normal weight. These findings suggest that increasing BAT activity in adults and children could potentially be a new avenue for the treatment of NAFLD and obesity.


title: Reliability Improvement of Regenerative Cascaded H-bridge (CHB) Medium-Voltage Drive

contributor:
Narimani, Mehdi
Electrical and Computer Engineering

subject:
Medium Voltage Motor Drives
Cascaded H-Bridge Multilevel Inverters
Reliability
Regeneration

abstract:
High power converters are widely used in many industries. At power levels in the
range of Mega Watt (MW), power conversion at medium voltage (MV) is preferred
due to better efficiency and lower cost. For medium voltages applications,
multilevel converters are widely adopted due to the features they offer with respect
to two-level converters. Cascaded H-bridge topology is a widely adopted multilevel
topology because of its modularity, scalability, and reliability. The conventional
cascaded H-bridge topology allows two-quadrant operation. In order to allow fourquadrant
operation, an active front end version of the cascaded H-bridge topology
has been proposed in literature and recently commercialized.
In the field, power converters operates under harsh loading and
environmental conditions. The resulting stresses imposed on converter components
cause their gradual degradation. In cascaded H-bridge converters, typically power
cell components such as power modules, DC-bus capacitors, and control PCBs are
v
highly stressed. Under these stresses power cell components degrade and require
replacement in the field, otherwise unexpected failures may occur.
The thesis aim is to address power cell components reliability through
proposing novel regenerative cascaded H-bridge converter control schemes to reduce
components stresses and failure probability without increasing size, cost, or
complexity. First, a novel PWM active front end control scheme has been proposed
to reduce the inherent ripple current stresses on the DC-bus capacitors. Second,
the thesis proposes a novel grid or near grid switching frequency front end control
scheme to reduce stresses on power modules and the power cell cooling
requirements. Third, novel cascaded H-bridge front end control schemes are
proposed to reduce the sensor count, thereby decreasing failure rate and cutting
down cost. The proposed work has been thoroughly validated through detailed 9-
cell regenerative cascaded H-bridge system simulation and experimentation.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Enhancing urban centre resilience under climate-induced disasters using data analytics and machine learning techniques

contributor:
El-Dakhakhni, Wael
Hassini, Elkafi
Civil Engineering

subject:
Urban Centre
Climate-Induced Dusasters
Resilience
Data Analytics
Machine Learning
Data-Driven Modelling

abstract: According to the Centre for Research on the Epidemiology of Disasters, the global average number of CID has tripled in less than four decades (from approximately 1,300 Climate-Induced Disasters (CID) between 1975 and 1984 to around 3,900 between 2005 and 2014). In addition, around 1 million deaths and $1.7 trillion damage costs were attributed to CID since 2000, with around $210 billion incurred only in 2020. Consequently, the World Economic Forum identified extreme weather as the top ranked global risk in terms of likelihood and among the top five risks in terms of impact in the last 4 years. These risks are not expected to diminish as: i) the number of CID is anticipated to double during the next 13 years; ii) the annual fatalities due to CID are expected to increase by 250,000 deaths in the next decade; and iii) the annual CID damage costs are expected to increase by around 20% in 2040 compared to those realized in 2020. Given the anticipated increase in CID frequency, the intensification of CID impacts, the rapid growth in the world’s population, and the fact that two thirds of such population will be officially living in urban areas by 2050, it has recently become extremely crucial to enhance both community and city resilience under CID. Resilience, in that context, refers to the ability of a system to bounce back, recover or adapt in the face of adverse events. This is considered a very farfetched goal given both the extreme unpredictability of the frequency and impacts of CID and the complex behavior of cities that stems from the interconnectivity of their comprising infrastructure systems. With the emergence of data-driven machine learning which assumes that models can be trained using historical data and accordingly, can efficiently learn to predict different complex features, developing robust models that can predict the frequency and impacts of CID became more conceivable. Through employing data analytics and machine learning techniques, this work aims at enhancing city resilience by predicting both the occurrence and expected impacts of climate-induced disasters on urban areas. The first part of this dissertation presents a critical review of the research work pertaining to resilience of critical infrastructure systems. Meta-research is employed through topic modelling, to quantitatively uncover related latent topics in the field. The second part aims at predicting the occurrence of CID by developing a framework that links different climate change indices to historical disaster records. In the third part of this work, a framework is developed for predicting the performance of critical infrastructure systems under CID. Finally, the aim of the fourth part of this dissertation is to develop a systematic data-driven framework for the prediction of CID property damages. This work is expected to aid stakeholders in developing spatio-temporal preparedness plans under CID, which can facilitate mitigating the adverse impacts of CID on infrastructure systems and improve their resilience.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Cosmic Proportion: The Shared Conceptual Framework of Greek Medicine, Ethics, and Politics

contributor:
Sean, Corner
Classics

subject:
Greek
Intellectual history
Philosophy
Greek medicine
Hesiod
Plato
Hippocrates
Alcmaeon

abstract: In my first chapter, I investigate how, according to Hesiod in his Works and Days, one achieves prosperity and well-being, namely by not provoking Zeus who “punishes those whose actions harm justice.” I suggest that the moral and practical elements of Hesiod’s teachings may be conceived of in similar terms of maintaining a disposition whereby one is content to possess resources proportionate to one’s level of activity and needs. In the second chapter, I examine how the conceptions of limit and proportion elucidated in my first chapter feature in medical texts. I investigate Alcmaeon’s description of health and disease in terms of a political distribution of power. A body, according to Alcmaeon, is healthy when its qualities are equally proportioned (isonomia) and one does not dominate (monarchia) the whole mixture (krasis). Alcmaeon describes health as the proportionate blending of qualities which formulates the definition of health as the equality of shares of powers and anticipates Hippocratic humorism. Hippocratic humorism, like the traditional, magicoreligious model of health, conceives of health similarly to Alcmaeon, in terms of a proper proportion and balance. In my third chapter, I investigate Plato’s conception of the soul and of justice. I explicate Plato’s conception of the soul as discussed in his Republic, Phaedrus, and Laws, and suggest that a similar view of the soul and of justice, as a proper proportion of internal constituents, persists. I then apply this view of justice as the proper proportion of parts to the polis and argue that disproportion within a polis leads to stasis – a disease of a political body. In conclusion, I argue that Greek medical, ethical, and political thought share a conceptual framework and are predicated on notions of balance, proportion, and equilibrium. Prosperity, bodily health, justice of the soul, and justice of the city are conceived of in similar terms of a proper proportion.

abstract: Thesis

abstract: Master of Arts (MA)

abstract: Greek medical authors are obviously interested in the nature of health and disease, but the repeated mention of health and disease in epic poetry, philosophy, and political thought is more surprising. Hesiod writes that Zeus punishes the entire city of an unjust man with plague because he harms Justice. Plato refers to injustice as a disease of the soul, and justice as a soul in good health. Euripides, in his Herakles, writes that Thebes itself was sick with stasis. These authors indicate that the Greek conception of health was conceived of in broad terms which were applied to other spheres, such as ethics and politics. But what are these terms? What is the basic conceptual framework that underlies Greek medical, ethical, and political thought that allowed authors to apply similar metaphors of health and disease to these different spheres? In this thesis, I suggest that underlying Greek medical, ethical, and political thought is the same conceptual framework of proportion, balance, and equilibrium.


title: Mitigation of Electric Vehicle Charging Effects on Distribution Grids Through Smart-Charging and On-board Solar Charging

contributor:
BAUMAN, JENNIFER
Electrical and Computer Engineering

subject:
Electric Vehicle
Smart Charging
Solar Energy
MPPT
GMPPT
Optimization
Solar-charged Electric Vehicle

abstract:
Electric vehicles (EV) have become very popular in recent years because they are a more sustainable, efficient, and environmentally friendly transportation option than traditional fossil-fuel vehicles. Increased EV charging can cause overheating, accelerated aging, and eventual early failure of the distribution transformers, as the distribution networks have not been established foreseeing a large number of EVs as loads. This thesis makes contributions in two main areas to help reduce the accelerated aging of distribution transformers as the number of EVs on the road continues to rise.
Firstly, vehicle smart charging is investigated to spread out the EV charging loads and hence decrease transformer heating and aging. Most EV smart charging algorithms require the use of extensive and costly infrastructure, including sensors, communication networks, controllable chargers, and central smart agents. This thesis proposes a new vehicle-directed smart charging strategy, called Random-In-Window (RIW) which allows individual vehicles to spread out their charging without any costly additional infrastructure. Detailed simulation results prove the advantages of this proposed algorithm.
Secondly, to further reduce EV charging loads on the grid, a large-scale solar-charged electric vehicle (SEV) is proposed. While RIW smart charging has only grid benefits, SEVs can contribute to grid benefit, driver benefit, and environmental benefit, as shown through detailed simulation results, making it a viable solution to transformer aging mitigation. To turn the SEV concept into reality, this research also proposes a fast maximum power point tracking algorithm for partially shaded conditions, and an algorithm which optimizes photovoltaic (PV) cell size and arrangement along with the power electronic converter design for on-board solar charging. Thus, the proposed solutions in this research can help reduce distribution transformer aging as EV penetrations continue to rise and increase the environmental benefits of EVs through optimized solar charging.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Overheating, accelerated aging, and eventual early failure of the distribution transformers caused by EV charging stress is a pressing concern that needs to be addressed. This thesis proposes two new vehicle-directed smart charging strategies and a concept of solar-charged electric vehicle (SEV) to help reduce the accelerated aging of distribution transformers. System level analysis of the mitigation of transformer aging using these two approaches with added driver and environmental benefits warrants the manufacturing and design challenges of the SEVs. Thus, this thesis proposes a fast and novel global maximum power point tracking algorithm well suited to fast moving vehicles for maximum solar power extraction at all times, especially during partial shading conditions, and an optimization process of the on-board PV cell dimension and number of such cells in series and parallel in the array based on power electronic converter for higher efficiency, lower cost, and lower mass.


title: Assessing potability of drinking-water sources and quality of surface water  on the Reserve of the Six Nations of the Grand River, Ontario (Canada)

contributor:
Chow-Fraser, Patricia
Biology

subject:
Six Nations reserve
Grand River
indigenous communities
E. coli
water quality
McKenzie Creek Watershed

abstract: Although water covers 70% of the earth's surface, less than 1% of it is freshwater that can be used for drinking. Even in Canada, where there is an abundance of freshwater in groundwater and in rivers and lakes, there are many indigenous communities that lack a sustainable source of drinking water. Such is the case for the Six Nations of the Grand River, the largest indigenous Reserve in Canada, located within an hour drive from major urban centers in southern Ontario and where less than 9% of the residents have access to safe, treated potable water. The major tributaries that drain the Six Nations reserve are part of the McKenzie Creek Watershed, which has been characterized as having the highest loading of sediments and nutrients to the lower Grand River, which eventually drains into the eastern basin of Lake Erie. This research project was initiated by the Six Nations community, who wanted an update on the prevalence of fecal contamination in their drinking water sources (wells, cisterns). Secondly, the community wanted to know the ecosystem health status of tributaries flowing through the Six Nations Reserve (McKenzie and Boston Creeks), and to determine if land uses in the watershed were negatively affecting the health of these streams. A study conducted in the summer of 2018 confirmed that 29% of the tap water tested in 75 households were contaminated with E. coli; 40% of the wells and 15% of the cisterns were contaminated and these were distributed throughout the Reserve with no apparent pattern. A study conducted in the summer of 2019 found that the McKenzie Creek was highly polluted with total phosphorus (P), total suspended solids, turbidity and total-ammonia nitrogen (N), while Boston Creek was highly polluted with soluble reactive P and E. coli as well as total-nitrate N. Nitrogen concentrations at 14 stations were highly and significantly related to percentage of agricultural land in catchments. Elevated levels of pollutants have been observed in the two creeks for three decades, indicating that conditions will not improve without remedial actions.

abstract: Thesis

abstract: Master of Science (MSc)


title: Understanding the effect of colorectal cancer on the ability to perform usual activities

contributor:
Bosch, Jackie
Rehabilitation Science

subject:
Colorectal cancer
Functional outcome
Fatigue
Outcome measurements
Inflammatory bowel disease
Gastrointestinal cancer

abstract:
Introduction: Colorectal cancer (CRC) survivors may experience functional deficits due to cancer-associated impairments. However, we do not understand their type and extent of functional deficits and how we could measure the associated cause of functional deficits, such as fatigue. As the survival of CRC survivors improves, the burden of living with functional deficits can be high.
Purpose: My research program aims to understand (1) the functional changes and deficits that CRC survivors experience and (2) how to best measure fatigue in this population.
Methods: To address the first aim, we used the data from the International Study of the Risk Factors for Gastrointestinal Bleeding and Cardiovascular Events after Gastrointestinal Bleeding to examine individuals’ functional abilities within 1 year of gastrointestinal cancer diagnosis (CRC being the most prevalent type).
For the second aim, we conducted a systematic review on fatigue measures in adults with inflammatory bowel disease (IBD) because the causes, severity, and impact of IBD and CRC- related fatigue might be similar. We identified fatigue measures in the IBD population, appraised their psychometric properties, and recommended the most psychometrically robust and feasible measures for clinical and research use, indicating the optimal measures for CRC survivors. Results: After gastrointestinal cancer diagnosis, the majority (~70%) performed fewer functional tasks, mostly in the instrumental activities of daily living; and about 44% had more difficulty walking. Our review identified 16 measures, reviewed the content and psychometric properties, and recommended the Functional Assessment of Cancer Therapy Instrument-Fatigue and the IBD- Fatigue scale for research and clinical use in IBD and CRC populations.
Conclusion: We provided a novel understanding of the functional deficits that CRC survivors experience and recommended the optimal measures for assessing CRC-related fatigue. As CRC survivors commonly experience fatigue, fatigue should be measured to understand its role in the functional abilities of CRC survivors.

abstract: Thesis

abstract: Master of Science Rehabilitation Science (MSc)

abstract: More people are living with colorectal cancer (CRC), but may have problems performing their daily activities (i.e. functional problems) due to cancer-associated impairments. However, we do not understand the extent of these impairments and functional problems. We used a sample of people with newly-diagnosed gastrointestinal cancer (CRC being the most common type) to understand their type and extent of functional problems. People were found to participate less in functional activities and particularly have more difficulty walking after a cancer diagnosis. Fatigue is common among those with CRC and may primarily cause functional problems. However, it is not commonly measured, and it is unclear how to best measure fatigue among them. Therefore, we reviewed key qualities of 16 fatigue measures in a similar population (inflammatory bowel disease, IBD) and recommended the Functional Assessment of Cancer Therapy Instrument-Fatigue and the IBD-Fatigue scale (English) as the most promising measures for those with CRC.


title: Camera Based Deep Learning Algorithms with Transfer Learning in Object Perception

contributor:
Habibi, Saeid
Ahmed, Ryan
Mechanical Engineering

subject:
deep learning
transfer learning
object detection
license plate recognition
lane detection
camera
perception
autonomous vehicle

abstract: The perception system is the key for autonomous vehicles to sense and understand the surrounding environment. As the cheapest and most mature sensor, monocular cameras create a rich and accurate visual representation of the world. The objective of this thesis is to investigate if camera-based deep learning models with transfer learning technique can achieve 2D object detection, License Plate Detection and Recognition (LPDR), and highway lane detection in real time. The You Only Look Once version 3 (YOLOv3) algorithm with and without transfer learning is applied on the Karlsruhe Institute of Technology and Toyota Technological Institute (KITTI) dataset for cars, cyclists, and pedestrians detection. This application shows that objects could be detected in real time and the transfer learning boosts the detection performance. The Convolutional Recurrent Neural Network (CRNN) algorithm with a pre-trained model is applied on multiple License Plate (LP) datasets for real-time LP recognition. The optimized model is then used to recognize Ontario LPs and achieves high accuracy. The Efficient Residual Factorized ConvNet (ERFNet) algorithm with transfer learning and a cubic spline model are modified and implemented on the TuSimple dataset for lane segmentation and interpolation. The detection performance and speed are comparable with other state-of-the-art algorithms.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Electrical Discharge Texturing for Vibration Control

contributor:
Koshy, Philip
Mechanical Engineering

subject:
Chatter Control
Electrical Discharge Machining

abstract: Self-excited vibration, known as chatter, limits material removal rate, surface finish and accuracy in machining, and may even cause structural damage to components of the machining system. Machining stability may be enhanced by a variety of methods, from moving machining parameters to stable regions, or using actively actuated tools specially designed to obstruct self-excitation, or even by passively enhancing the stiffness or damping of the system as to soften the critical mode of vibration. Although there are many approaches to reduce chatter, not all of them are always effective in every situation. Moving machining parameters is restricted by workpiece machinability. Active damping mechanisms require large contraptions to function and have limited effectiveness when dealing with high frequency chatter. Passive damping approaches have essentially entailed tuned mass dampers which require delicate finetuning and drastic alterations to the tool structure in order mount the vibration absorber system. This research presents an elegant and innovative application involving electrical discharge texturing for chatter suppression that takes advantage of frictional forces to passively damp self-excited vibrations. This technique proved effective in a frequency range from 100 to 4000 Hz achieving damping enhancements of more than 400% without the need of any tuning and showing repeatable damping values after subsequent assembly and disassembly cycles. When applied to a grooving operation the technique proved effective in increasing the limiting width of cut by more than 120%.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Exploring the Role of Temporal Variation in the Detection and Subjective Annoyance of Auditory Alarm Signals

contributor:
Schutz, Michael
Psychology

subject:
auditory cognition
auditory perception
auditory alarms
music cognition

abstract: This thesis is composed of two independent manuscripts for publication. The first (Chapter 2) “More Detectable, Less Annoying. The Role of Temporal Variation in Envelope and Spectral Content on Detection and Annoyance” will be submitted to Psychological Science. This manuscript explores how detection and annoyance of sound are affected by temporal variation in two acoustic parameters; amplitude envelope and spectral content. The second (Chapter 3) “Improving Detectability of Auditory Interfaces Through Temporal Variation in Envelope” will be submitted to Human Factors. Here I build off of the previous manuscript by investigating tone detection in a split attention task more pertinent to the normative use of auditory interfaces. The author of this thesis is the primary author of both papers.

abstract: Thesis

abstract: Master of Science (MSc)


title: Are Dominant Routes the Least Stressful Routes in a Bike Share System? An Investigation of Hamilton Bike Share using Weighted Level of Traffic Stress

contributor:
Scott, Darren M.
Geography

subject: Active travel; Bike Share; Cycling; Dominant Route; Level of Traffic Stress; Route Choice

abstract: Level of Traffic Stress (LTS) is a four-level system that classifies the stress experienced by cyclists on road segments and at intersections. While LTS has been used in past studies to assess cycling connectivity, accessibility, and safety, very little is known concerning its influence on cycling preferences. This study investigates this topic using a dataset containing 323,163 unique GPS trajectories of Hamilton Bike Share (HBS) users collected over a 12-month period (January 1st to December 31st, 2019). A GIS-based map-matching algorithm is used to generate users’ routes from these trajectories along with attributes such as route length, number of intersections, and number of turns. Unique routes and their use frequencies are then extracted from all routes. The most popular routes between bike share hub (station) pairs are then identified as dominant routes while shortest distance routes are derived by minimizing distance traveled. Weighted level of traffic stress (WLTS), a novel measure of impedance (travel cost) developed for this study, is used to derive the least stressful routes between hub pairs. The three types of routes are compared statistically. The comparison finds that HBS users tend to choose longer routes with bicycle infrastructure in an effort to reduce their traffic stress. However, they do not choose to minimize traffic stress in its entirety by choosing the lowest WLTS routes. In other words, dominant routes are not the least stressful routes in a bike share system. Likewise, minimizing distance is not the sole consideration of HBS users. The findings suggest that other factors also influence route choice. This study not only enhances our understanding of cyclist route preferences with respect to LTS, it also presents a novel measure of impedance – WLTS – that could be used when planning new cycling infrastructure or as an alternative means to route cyclists between origins and destinations.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Essential Work of Double-Duty Carers during the COVID-19 Pandemic

contributor:
Williams, Allison
Global Health

subject: caregiver, health, covid-19, pandemic, policy, mixed-methods, healthcare, ontario

abstract:
Background: In the healthcare sector, many workers are believed to be “double duty carers” (DDCs) - individuals providing care both at work and home. DDCs often work in paid care work while providing unpaid care to family/friends outside of work. The COVID-19 pandemic places additional stressors on these vulnerable carers. Caring is an emerging global health issue involving the straining of roles due to the pandemic. Informal or unpaid caring is globally known to be a women's health issue given the gendered nature of caring, resulting in women shouldering greater physical, social, and emotional costs.
Purpose: The aim of this study was to understand the impact of COVID-19 on DDCs through the perspective of employers and DDCs. The knowledge generated illuminates how the paid and unpaid caring has been affected by the pandemic, what supports, or coping strategies are being utilized by DDCs.
Methods: This mixed-methods study comprises two phases; a quantitative survey for employers and qualitative interview for DDCs. The survey investigates how workplace supports have been impacted by the pandemic, while the interview investigates DDCs’ experiences/coping strategies during the pandemic. Finally, triangulation of the data from the two phases will be used to create evidence-based policy recommendations to enhance DDC supports.
Results: Healthcare employers were observed to be cognizant of DDCs’ diminishing wellness during the COVID-19 pandemic; yet, less than half supported their carer-employees. DDCs had increased care demands both at work and at home and experienced a lack of access to their usual support system and support services. The data from both phases helped elucidate recommendations and areas of concern for DDC support that can serve as important implications for carer-friendly workplace policies (CFWP).
Conclusion: By exploring the intersection of perspectives from employers and DDCs, this study will contribute to evidence-informed guidelines for CFWP during a pandemic.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: The term ‘double duty carer’ (DDC) refers to individuals, often women, that are provide care both at home and at work. DDCs are an important workforce that are vulnerable to negative physical and mental health consequences which are exacerbated during the COVID-19 pandemic. The purpose of this study is to examine the impact of the pandemic on DDCs’ caring responsibilities and supports from the perspectives of healthcare employers and DDCs. Findings showed that the COVID-19 pandemic made paid and unpaid caring much more demanding, inflicted poor health consequences upon DDCs and made supports difficult to access. DDCs are experiencing increased role strain and having to invest more hours in paid and unpaid care. The findings of this study can be used to improve DDC support and strengthen the collaborative relationships among healthcare employers and DDCs.


title: Improving the penetration resistance of textiles using novel hot and cold processing lamination techniques

contributor:
Selvaganapathy, Ravi
Chan, Ching
Mechanical Engineering

subject: Ultra-high molecular weight polyethylene (UHMWPE)

subject: Ballistic impact

subject: Body armor

subject: Pressure-sensitive adhesive

subject: Hot film

subject: Pattern

abstract:
In this study, novel lamination techniques are introduced for the coating of fabrics in order to enhance their ballistic/needle penetration resistance properties. Pressure sensitive adhesive (PSA) was used to create flexible ballistic composite panels with ultra-high molecular weight polyethylene (UHMWPE) fabric. An increase in processing pressure from 0.1 to 8 MPa significantly improved the ballistic performance against 9 mm FMJ ammunition of UHMWPE composite. The number of layers required to stop the bullet were reduced from 45 to 22 layers after lamination without a significant increase in stiffness. The backface signature (BFS) was reduced from 19.2 mm for the 45 layer neat samples to 11.7 mm for the 25 layer laminated samples pressed at 8 MPa.
The second lamination technique used patterned thermoplastic hot film to create flexible UHMWPE composite laminates. Hexagonal patterns were cut through a heat transfer vinyl carrier sheet using a vinyl cutter and was used as a mask between the UHMWPE fabric and hot film during heat treatment in order to have the fabric coated only on those regions. The patterns had a nominal diameter of 27.9 mm with a 1 mm gap between each region. A significant improvement in the ballistic performance of UHMWPE fabric is observed after coating each individual layer with patterned hot film and 25 layers of laminated fabric were sufficient to stop a .357 magnum FMJ ammunition compared to unlaminated neat fabric which required 45 layers to stop the bullet. Patterning of the hot film did not negatively affect the ballistic performance of the composite laminates whilst increasing their flexibility in relation to using plain hot film with no patterning involved. It resulted in a 21% increase in bending angle of the 25 layer samples
v
and 9.5% reduction in bending length of the single plies which both relate to greater flexibility because a higher bending angle and lower bending length correlates to more flexibility.
The same technique of patterning of hot film is used in the lamination of woven cotton fabric to enhance needle penetration resistance properties whilst maintaining the flexibility. Patterns used in this study were either hexagonal or a combination of hexagons and triangles and the nominal diameter ranged from 2.6-13.5 mm. The lamination significantly improved the 25G hypodermic needle penetration resistance of the fabric. By increasing the number of laminated fabric plies from 1 to 2, the needle resistance force increased by up to 150%. However, in comparison to just one layer, the flexibility decreased by about 12% to 26% for two and three layers, respectively. It was observed that reducing the sizes of the patterns improved the flexibility of the samples by up to 30% without compromising the needle penetration resistance.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: BIG DATA ANALYTICS FOR BATTERY ELECTRIC BUS ENERGY MODELLING AND PREDICTION

contributor:
Mohamed, Moataz
Civil Engineering

subject:
Complex Network Theory
Battery-Electric Buses
Energy Consumption
Data-Driven Models
Machine Learning
Sensitivity Analysis

abstract:
Battery electric buses (BEBs) bring several advantages to public transportation systems. With fixed routes and scheduled trips, the implementation of BEBs in the transit context is considered a seamless transition towards a zero greenhouse gases transit system. However, energy consumption uncertainty is a significant deterrent for mainstream implementation of BEBs. Demonstration and trial projects are often conducted to better understand the uncertainty in energy consumption (EC). However, the BEB's energy consumption varies due to uncertainty in operational, topological, and environmental attributes.
This thesis aims at developing simulation, data-driven, and low-resolution models using big data to quantify the EC of BEBs, with the overarching goal of developing a comprehensive planning framework for BEB implementation in bus transit networks. This aim is achieved through four interwind objectives.
1)	Quantify the operational and topological characteristics of bus transit networks using complex network theory. This objective provides a fundamental base to understanding the behaviour of bus transit networks under disruptive events.
2)	Investigate the impacts of the vehicular, operational, topological, and external parameters on the EC of BEBs.
3)	Develop and evaluate the feasibility of big-data analytics and data-driven models to numerically estimate BEB's EC.
4)	Create an open-source low-resolution data-based framework to estimate the EC of BEBs. This framework integrates the modelling efforts in objectives 1-3 and offers practical knowledge for transit providers.
Overall, the thesis provides genuine contributions to BEB research and offers a practical framework for addressing the EC uncertainty associated with BEB operation in the transit context. Further, the results offer transit planners the means to set up the optimum transit operations profile that improves BEB energy utilization, and in turn, reduces transit-related greenhouse gases.

abstract: Thesis

abstract: Doctor of Engineering (DEng)


title: INVESTIGATION ON BURR CONTROL DURING THE DRILLING OF DUCTILE MATERIALS

contributor:
Veldhuis, Stephen
Mechanical Engineering

subject:
Exit burr formation
Burr control
ductile materials
Aluminum
Step drill
Pressurized materials
Drilling

abstract:
Burrs are rough protrusions that form along the edge of a component during processing and are commonly produced during machining. Generally, the presence and severity of a burr directly impacts the final part quality. Thus, burrs need to be removed in subsequent processes to avoid injury when handling a part and/or negatively impacting the part's functionality. The size, shape, and nature of the attachment of the burr to the cutting edge are highly dependent on the material, tooling, and process parameters used during machining.
This research aimed to develop two new approaches to minimize and/or eliminate burr formation during the drilling of ductile materials. The first new method outlined in this thesis relates to injecting materials in different forms at high pressures under the workpiece on the side from which the drilling tool exits to support the drilling thrust force and thereby minimize exit burr formation. The second method introduced a novel technique for designing and testing highly effective step drills based on the workpiece material and cutting parameters, using commercial drills. Testing the two approaches showed promising results for producing comparatively smaller exit burrs.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Predicting survival status of lung cancer patients using machine learning

contributor:
Jeremic, Aleksandar
Electrical and Computer Engineering

subject: Lung cancer, machine learning

abstract:
5-year survival rate of patients with metastasized non-small cell lung cancer
(NSCLC) who received chemotherapy was less than 5% (Kathryn C. Arbour,
2019). Our ability to provide survival status of a patient i.e. Alive or death at
any time in future is important from at least two standpoints: a) from clinical
standpoint it enables clinicians to provide optimal delivery of healthcare and b)
from personal standpoint by providing patient’s family with opportunities to
plan their life ahead and potentially cope with emotional aspect of loss of life.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: EXPERIMENTAL INVESTIGATION OF THE THERMAL PERFORMANCE OF VERTICAL AND ELBOW THERMOSYPHONS

contributor:
Chan, Ching
Mechanical Engineering

subject:
Elbow thermosyphon
Performance hysteresis;
Evaporator performance
Thermosyphons
Vertical Evaporator
Condenser
Flow pattern
Instabilities

abstract:
The thermal performance of two thermosyphons with different geometries was experimentally investigated in this study. The first thermosyphon utilized a 310 mm long vertical evaporator and a 385 mm long condenser section that was inclined at 5 degrees from the vertical. The second was an elbow configuration with a 140 mm long vertical evaporator and a 190 mm long condenser oriented 8 degrees from the horizontal. Both thermosyphons were made of internally grooved copper tubing with an outer diameter of 15.87 mm, wall thickness of 0.5 mm and a nominal groove height of 0.3 mm. Tests were performed over a range of input heat fluxes where the condenser was cooled by flowing water around the condenser with inlet temperature of 10°C, 20°C, and 35°C. The effects of incrementally increasing and decreasing heat flux was investigated for the elbow thermosyphon. Temperature measurements along the thermosyphon were taken when incrementally changing the heat flux from 0.5 to 11 W/m2 for the first thermosyphon and 0.3 to 6 W/m2 for the second thermosyphon.
Internal flow regimes were characterized using temperature transient profiles and compared to existing flow regime maps for closed thermosyphons suggested by Smith et al. (2018: Part a and Part b) and Terdoon et al. (1997). The temperature transients along the evaporator for the first thermosyphon settled to a more uniform profile as heat flux was increased. For the second thermosyphon the temperature profiles suggested a change to a more dynamic flow in the evaporator at heat flux of approximately 6 W/m2. The elbow thermosyphon showed evidence of a significant hysteresis in the evaporator performance at moderate heat fluxes between 2 and 8 W/cm2. Comparisons were made between the two thermosyphons to study the effects of inclination angle and the feasibility of angle corrections to the Nusselt film condensation model from Guichet and Jouhara (2020). A modification to the Rohsenow condensation model from Guichet and Jouhara (2020) was recommended for the first thermosyphon showing good representation of the condenser performance. The evaporator performance results were compared to existing models from the literature.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: INVESTIGATING THE NEUROPROTECTIVE MECHANISMS OF CANNABINOIDS THROUGH ENDOPLASMIC RETICULUM STRESS MODULATION

contributor:
Mishra, Ram
Neuroscience

subject:
Neuroprotection
ER Stress
Cannabinoids

abstract: The aggregation of misfolded proteins in the endoplasmic reticulum (ER) is a pathological trait shared by many neurodegenerative disorders. This aggregation leads to the persistent activation of the unfolded protein response (UPR) and ultimately apoptosis due to ER stress. Cannabinoids, such as tetrahydrocannabinol (THC) and cannabidiol (CBD), have been reported to be neuroprotective in in vitro and in vivo models of neurodegeneration through their antioxidant and anti-inflammatory properties. However, little is known about the role of these cannabinoids in the context of ER stress. STHdhQ7/Q7 cells were treated with the ER stress inducer thapsigargin (TG) and cannabinoids in three different experimental paradigms to investigate the effect of 2.5 µM THC and 1 µM CBD monotreatment and cotreatment on ER stress-induced cell death. The mouse striatal neurons survived significantly more when THC or CBD was given before TG exposure. To further investigate this experimental paradigm, the gene and protein expression of UPR proteins was measured to determine the effect of cannabinoid pre-treatment on cell survival through ER stress modulation. A significant increase in the gene expression of the ER chaperone GRP78 and the ER-resident neurotrophic factor MANF in pre-treated samples suggest that with THC or CBD pre-treatment, the protein folding capacity of the cell is improved. Additionally, a decrease in the ER-mediated apoptotic markers such as BIM and caspase 12 with THC or CBD pre-treatment provides further evidence that cannabinoid pre-treatments are neuroprotective through ER stress modulation. These data suggest that prior cannabinoid monotherapy prepares the cell for future insults to the ER. Understanding the role of ER stress in the neuroprotective properties of THC and CBD provides insight into the therapeutic potential of cannabinoids and the role of ER dysfunction in various neurodegenerative disorders.

abstract: Thesis

abstract: Master of Health Sciences (MSc)

abstract: With the worldwide ageing population increasing, finding new treatments for illnesses that affect the elderly is crucial. Disorders such as Parkinson’s and Alzheimer’s disease mainly affect older individuals and are caused when brain cells stop working or when brain cells die. These disorders share some common causes. One is the inability to fold proteins properly. The cellular process that is responsible for protein folding and the changes that occur within that process are studied in this project. Also, the impact of the cannabinoids THC and CBD, a major component of cannabis, on the protein folding process is studied. This project found that using cannabinoids before the protein folding system is disrupted helps brain cells survive. This study is a step in understanding how THC and CBD are helpful in brain cell survival in patients suffering from diseases that damage brain cells.


title: Biophysics of Blood Membranes

contributor:
Rheinstädter, Maikel
Physics and Astronomy

subject:
Blood
Membrane
Biophysics
Bending Modulus
Red Blood Cell Membrane
Covid 19
Functionalized Membranes
Hybrid Membranes

abstract:
Red blood cells (RBCs) are the predominant cell type in blood and have a two-layered outer shell which is composed of a cytoskeleton network tethered to a cytoplasmic membrane.
In this thesis, I study the structure and mechanical properties of the RBC’s cytoplasmic membrane (RBCcm) on the nanoscale and utilize this knowledge to functionalize this biological structure on a molecular level. In a first case study, I measure the membrane’s bending rigidity from thermal fluctuations observed in X-ray diffuse scattering (XDS) and Neutron Spin Echo (NSE) experiments, as well as Molecular Dynamics (MD) simulations. I provide evidence of the RBCcm's highly deformable nature with a bending rigidity that is substantially softer as compared to synthetic membranes. The methods are applied to RBCs that were stored for up to 5 weeks. I demonstrate that storage of RBCs leads to an increased fraction of liquid ordered membrane domains and an increased bending rigidity.

RBCs are ideal for pharmaceutical applications as they provide access to numerous targets in the body, however lack specificity. Functionalizing the cytoplasmic membrane is thus a prerequisite to use these cells in biotechnology. I develop protocols throughout two studies to tune the membrane's lipid and protein composition. I investigate the impact of synthetic lipid molecules on the membrane's structure and demonstrate that small molecules can be encapsulated into liposomes that are formed from these hybrid membranes.
Further, I provide direct evidence that the SARS-CoV 2 spike protein can be anchored into the RBCcm through a detergent mediated insertion protocol. These virus-like particles are observed to trigger seroconversion in mouse models, which demonstrates the potential of functionalized RBC in biotechnology.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Learning abstract words: Role of valence in linguistic context

contributor:
Kuperman, Victor
Cognitive Science of Language

subject:
word learning
embodied cognition
concreteness
valence

abstract: This study investigates the role of emotional linguistic input in learning novel words with abstract and concrete denotations. It is widely accepted that concrete concepts are processed more easily than abstract ones. Several theories of vocabulary acquisition additionally propose that learning of concrete concepts puts greater weight on sensorimotor information while abstract concepts put greater weight on emotional information. In this study, proficient adult speakers of English read novel words denoting concrete and abstract concepts (e.g., boat vs religion) embedded in informative passages with different emotional valence (positive, neutral and negative). After five exposures to each novel word in an emotionally consistent context, participants were tested on orthographic and semantic vocabulary learning and provided valence judgments of these novel words. Readers successfully learned orthographic form and meaning of novel words, with a concreteness advantage seen in both tasks measuring semantic learning. Critically, valence of linguistic contexts was more influential for novel words with concrete denotations. In line with previous reports, the transfer of context emotionality to novel words (i.e., semantic prosody) took place in concrete stimuli and not abstract stimuli, even though they were both embedded in emotional contexts. An equal advantage was seen for semantic learning of novel words with both concrete and abstract denotations seen in positive contexts. These findings provide counter-evidence to theories advocating greater reliance of abstract concept learning on emotional information.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: “The girl walked her plurk down the street.” Did you think of a dog? Adults are constantly learning new words by inferring the meaning through context. By making small changes to word and sentence stimuli we can study how semantic properties such as emotion (positive, neutral, or negative) and concreteness (e.g., "lamp" is a physical object that can be touched, making it high in concreteness, while "hope" cannot be touched and is therefore low in concreteness, or abstract) interact.  In the current study, we manipulate contexts to vary in emotionality and words to vary in concreteness. Participants read short passages containing new words and were given a surprise test after that measured how well they learned the emotionality, forms, and meanings of the new words. This study presents new insight for theories of how new words are learned and stored in the brain and have implications for language learning materials.


title: Changes in Maternal Psychophysiology Occurring in Response to Peer-Delivered Cognitive Behavioral Therapy for Postpartum Depression

contributor:
Van Lieshout, Ryan
Neuroscience

subject: Postpartum depression, cognitive behavioural therapy, physiology, frontal alpha asymmetry, heart rate variability

abstract:
Background: Postpartum Depression (PPD) affects up to one in five mothers. While
psychotherapy can effectively reduce symptoms of PPD, it is unclear how PPD treatment affects maternal psychophysiology. Determining physiological changes in response to cognitive
behavioural therapy (CBT) could provide insights into the mechanisms underlying effective
treatment and/or help predict treatment outcomes. This study examined if treating PPD with CBT led to changes in frontal cortical activity and heart rate variability, two markers of maternal emotion regulatory capacity.
Methods: Community-dwelling mothers with PPD (Edinburgh Postnatal Depression Scores
≥10) were randomized to receive nine weeks of group CBT delivered by recovered peers (i.e.,
those who had previously recovered from PPD) (n=26) or be put on a waitlist to receive the
intervention nine weeks later (n=24). Electroencephalographic (frontal alpha asymmetry),
electrocardiographic (heart rate variability), and clinical (depression, anxiety) data were collected at baseline and nine weeks later.
Results: Participants in both the immediate treatment and waitlist control groups reported
moderate levels of depression and anxiety at baseline. After treatment, mothers in the treatment group showed greater improvements in depression (p<0.01, Cohen d=1.22), and anxiety (p<0.005, Cohen d = 1.48), and high-frequency heart rate variability (p<0.05, Cohen d=0.70), but not frontal alpha asymmetry, compared to the waitlist control group.
Conclusion: Group CBT for PPD can improve symptoms of depression and anxiety and
parasympathetic nervous system function. Future research should attempt to replicate and extend these findings using larger samples, additional biomarkers, and longer periods of follow up. Examining how evidence-based treatments for PPD affect maternal psychophysiology can
improve our understanding and potentially predict treatment effects.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
Postpartum depression affects up to one in five mothers in the first year after delivery. When
treated promptly with talking therapies (i.e., psychotherapy) such as cognitive behavioural
therapy (CBT), many experience significant improvements in their symptoms. However, the
changes occurring in the brain and the remainder of the nervous system occurring in response to psychotherapy is not well known. It is important that this is understood so that we can develop more effective treatments and better predict who will respond to different types of treatments. In particular, the role of the frontal lobe of the brain, and the body’s parasympathetic system is poorly understood in the context of PPD. This thesis aimed to examine the impact of CBT on women’s frontal lobe functioning using a measure called frontal alpha asymmetry (FAA) measured via electroencephalography (EEG), and parasympathetic nervous system-based heart rate variability (HRV) using electrocardiography (ECG). In this study, we compared mothers with PPD treated with CBT to those who did not receive this treatment. We found that HRV responded in mothers who received CBT compared to women who were in the control group. No significant changes were found for FAA after treatment. These results suggest that HRV may be explored further as a valid treatment outcome for CBT when provided to women with PPD.


title: Analytical Frameworks in Colorectal Cancer Guidelines: Development of Methods for Systematic Reviews and their Application

type: Thesis Other

contributor:
Holger, Schünemann
Health Research Methodology

subject:
Analytical framework
Colorectal cancer
guideline
clinical practice guideline
Methods
systematic review

abstract: Background: Analytical frameworks (AF) are graphical representation of the key questions answered by a systematic review and can support the development of guideline recommendations. Our objectives are to a) conduct a systematic review to identify, describe and compare all AFs published as part of a systematic and guideline development process related to colorectal cancer (CRC); and b) to use this case study to develop guidance on how to conduct systematic reviews of AFs. Methods: We conducted a systematic review and searched Medline and Embase from 1996 until December 2020. We also manually searched guideline databases and websites. We identified all guidelines in CRC that utilized an AFs and all systematic reviews in primary prevention, screening, and diagnosis of CRC that used AFs. We assessed quality of the guidelines using the Appraisal of Guidelines for Research and Evaluation II tool. The systematic review was registered in PROSPERO, registration CRD42020172117. Results: We screened 34,505 records and identified 1166 guidelines on CRC and 3127 systematic reviews, of which 5 met our inclusion criteria identifying a total of 4 AFs in colorectal cancer. We describe our search strategy and methods for conducting systematic reviews for AFs. Conclusion: Few guidelines and systematic reviews are utilizing AFs in the development of recommendations. We developed methods for conducting a systematic review on AF

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Analytical frameworks are graphical diagrams that represent key questions with flow of resining from population to outcome. We conducted a systematic review to identify all analytical frameworks in colorectal cancer and in the process we developed guidance on how to conduct a systematic review for analytical frameworks. We identified four analytical frameworks, one in primary prevention, and three in screening of colorectal cancer. We found only a few clinical practice guidelines that utilized analytical frameworks in the development of the recommendations. We developed methods for conducting a systematic review of analytical frameworks.


title: Selective Area Growth Techniques Using Metal Organic Chemical Vapour Deposition for III-V Semiconductor Quantum Well Laser Devices

contributor:
Kleiman, Rafael
Engineering Physics

abstract: Selective area growth (SAG) is a technique used for semiconductor manufacturing to alter the epitaxial growth formation on the surface of a substrate. Surface feature modifications allow for local area semiconductor growth manipulation, increasing flux in the vicinity of non-growth mask edges. GaAs (100) wafers were processed with photolithographic direct laser pattern writing to create a series of silica rectangular prism masks on the surface of the substrate. The non-growth centers possess a very low sticking coefficient when placed within a metal-organic chemical vapour deposition (MOCVD) chamber with respect to the semiconductor materials deployed. In this work the establishment of a robust MOCVD process flow leading up to InGaAs compounds is defined at McMaster University’s Centre of Emerging Device Technologies. Quantum-well laser devices were fabricated in surface cavities to highlight the capabilities of SAG with MOCVD. A micro-photoluminescence device was manufactured with spatial resolution to test quantum-well emission spectra. The growth mechanics and photoluminescence of the quantum-well lasers were examined and characterized to improve the parametric control of the MOCVD process flow.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: A MULTI-YEAR STREAM TEMPERATURE ANALYSIS IN THE WOLF CREEK RESEARCH BASIN, YUKON TERRITORY

contributor:
Carey, Sean
Earth and Environmental Sciences

subject:
Hydrology
Water Temperature
Cold Region Hydrology
Wolf Creek Research Basin

abstract: MSc thesis focusing on stream temperature research in a subarctic catchment.

abstract: Water temperature is an important stream characteristic that has a significant impact on the biological and chemical processes within an aquatic ecosystem, and it is sensitive to changes in climate and hydrologic regimes. Stream temperature dynamics are driven by heat exchange processes with the atmosphere and the interaction between surface water and groundwater, and it is uncertain how thermal regimes in northern environments will change under a warming climate. The objective of this thesis is to evaluate summer stream temperature variability in the Wolf Creek Research Basin (WCRB), and investigate relationships between stream temperature and hydrometeorological variables. Long-term stream temperature data for the WCRB in Yukon Territory, Canada was collected from 2002 to 2019 at both the outlet of Wolf Creek (WC), and for one of its high-elevation tributaries, Granger Creek (GC). Linear regression models were developed to explore relationships between stream temperature and various predictor variables at monthly and seasonal scales. The incorporation of an autoregressive term into regression models determined the importance of accounting for the autocorrelation structure of daily measurements, when considering annual regression coefficients. Model selection identified air temperature as the primary predictor variable for daily stream temperature, with streamflow and precipitation having variable inter-annual influences. Monthly stream temperatures at Granger Creek were related to air temperature, date of snow disappearance and antecedent stream temperature, whereas Wolf Creek monthly stream temperatures were most strongly related to antecedent stream temperature. These results suggest that the timing of snowmelt, streamflow, catchment thermal memory (as represented by antecedent stream temperature), and seasonal meteorology interact to influence interannual variability in summer stream temperature at the Wolf Creek Research Basin.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Water temperature plays an important role in determining the quality of an aquatic environment. There are many factors that control stream temperature, and it is uncertain how temperatures in northern environments will respond in the future. The objective of this thesis is to evaluate influences on summer stream temperature in the Wolf Creek Research Basin (WCRB). Stream temperature data was collected for the WCRB in Yukon Territory, from 2002 to 2019 for both Wolf Creek (WC) and Granger Creek (GC). Air temperature had the strongest relationship with daily stream temperature; streamflow and rain had inconsistent relationships through time. Monthly stream temperatures at Granger Creek were related to air temperature, date of snow disappearance and prior month’s stream temperature. Wolf Creek monthly stream temperatures were most strongly related to prior month’s stream temperature. These results highlight underlying influences on stream temperature, which may not be captured by a stream temperature models.


title: Development of Self-Adaptive PVD Coatings for Machining TI6Al4V Alloy

subject: Rough turning, finish turning, Ti6Al4V alloy, PVD coating, built up edge (BUE), flank wear, crater wear, tribo-films.

abstract:
The usage of titanium alloys in many industries has increased significantly over the years due to their superior properties. However, they are extremely difficult to machine because of their distinctive characteristics such as their high temperature strength, low thermal conductivity, and high chemical affinity for tool materials. Hence, despite their increased usage, they are still expensive to machine when compared to other metals.
The current research aims to address the machinability issues of titanium alloys by developing novel compositions of a new generation of self-adaptive Physical Vapor Deposition (PVD) coatings that function by forming beneficial tribo-films through their interaction with the environment. These tribo-films form during cutting and provide enhanced lubricity, hardness, strength, and thermal barrier characteristics to the cutting tool. It was found that during Ti6Al4V machining, significant BUE and crater wear formation occurs; however, one is dominant over the other depending on the cutting conditions. Therefore, the coatings investigated were designed by taking into consideration the dominant tool wear mechanisms and the complex tribological phenomena that occur in the cutting zone.
The current research investigated monolayer TiB2 and CrN self-adaptive PVD coatings for the rough (cutting speed - 45 m/min, feed -0.15 mm/rev, and depth of cut – 2 mm) and finish (cutting speed - 150 m/min, feed -0.1225 mm/rev, and depth of cut – 0.25 mm) turning of Ti6Al4V alloy. Detailed experimental studies were performed to study the effectiveness of the coatings during machining. Micro-mechanical characteristics of the coatings were also studied to understand how coating properties affect the coatings performance in machining and tribo-film formation. The results obtained show that both the TiB2 and CrN coatings significantly improve tool performance during the rough turning of Ti6Al4V alloy compared to the current industrial standard, which is due to certain micro-mechanical coating properties and the beneficial tribo-films formed. A coating of CrN coating was found to increase tool life during finish turning. It was also established that for machining applications where intensive adhesive interaction occurs at the tool-chip interface, coatings with lower hardness values perform significantly better than harder ones.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Titanium alloys are increasingly becoming the material of choice for many industrial applications due to their superior properties. However, they are very difficult to machine since they have high chemical affinity towards tool materials, low thermal conductivity, and high temperature strength. These properties cause rapid failure of the tool. The objective of the current research is to address machinability issues during Ti6Al4V machining and improve tool performance. One effective strategy to minimize tool wear is to apply self-adaptive PVD tool coatings that can form beneficial tribo-films through their interaction with the environment and provide enhanced lubricity, hardness, strength, and thermal barrier characteristics to the cutting tool. In the current research, two self-adaptive PVD coatings were developed that offset the dominant tool wear mechanisms prevalent during the rough and finish turning of Ti6Al4V alloy and reduced the tool wear rate by more than 60% compared to the current industrial standard.