Graduate Theses & Dissertations


Adoption of a Finite Element Model of Material Deformation Relevant to Studying Corneal Biomechanics
The human cornea is required to exhibit specific material properties to maintain its regular shape under typical intraocular pressures which then allow for its correct optical functionality. In this thesis, the basis of continuum solid mechanics and the finite element method are introduced. We use finite element modelling to simulate the extension of an effective-1d, linear-elastic bar, a cornea-like body governed by Poisson’s equation, and the deformation of a loaded, linear-elastic, cube. Preliminary results for the deformation of a simulated, linear-elastic, cornea have also been achieved using the finite element approach. Author Keywords: continuum solid mechanics, corneal biomechanics, finite element method, intraocular pressure
Long-term Financial Sustainability of China's Urban Basic Pension System
Population aging has become a worldwide concern since the nineteenth century. The decrease in birth rate and the increase in life expectancy will make China’s population age rapidly. If the growth rate of the number of workers is less than that of the number of retirees, in the long run, there will be fewer workers per retiree. This will apply great pressure to China’s public pension system in the next several decades. This is a global problem known as the “pension crisis”. In this thesis, a long-term vision for China’s urban pension system is presented. Based on the mathematical models and the projections for demographic variables, economic variables and pension scheme variables, we test how the changes in key variables affect the balances of the pension fund in the next 27 years. This thesis applies methods of deterministic and stochastic modeling as well as sensitivity analysis to the problem. Using sensitivity analysis, we find that the pension fund balance is highly sensitive to the changes in retirement age compared with other key variables. Monte Carlo simulations are also used to find the possible distributions of the pension fund balance by the end of the projection period. Finally, according to my analysis, several changes in retirement age are recommended in order to maintain the sustainability of China’s urban basic pension scheme. Author Keywords: China, demographic changes, Monte Carlo simulation, pension fund, sensitivity tests, sustainability
Family Experiences in Nature
Children may be spending less time outdoors in nature than in previous generations, with one potential reason being parents in their role as ‘gatekeepers’ to the outdoors. This study investigated how families are spending their time during the COVID-19 pandemic, and how parents may influence children’s outdoor nature experiences. Parents (N = 121) from across Canada completed measures related to their family’s activities as well as their own connection with nature, attitudes about nature, and childhood nature contact. Results suggest that having easy access to nature, a greater connection with nature, believing in the importance of outdoor experiences, and doing outdoor activities in childhood may be associated with more current family time outside in nature. By understanding the reasons behind parental decisions regarding where and how families spend time outside, strategies can be developed to help parents increase their children’s nature time in the future. Author Keywords: children, family, nature, nature-relatedness, outdoors, parents
Modelling Depressive Symptoms in Emerging Adulthood
Depression during the transition into adulthood is a growing mental health concern, with overwhelming evidence linking the developmental risk for depressive symptoms with maternal depression. In addition, there is a lack of research on the protective role of socioemotional competencies in this context. This study examines independent and joint effects of maternal depression and trait emotional intelligence (TEI) on the longitudinal trajectory of depressive symptoms during emerging adulthood. A series of latent growth models was applied to three biennial cycles of data from a nationally representative sample (N=933) from the Canadian National Longitudinal Survey of Children and Youth. We assessed the trajectory of self-reported depressive symptoms from age 20 to 24 years, as well as whether it was moderated by maternal depression at age 10 to 11 and TEI at age 20, separately by gender. The results indicated that mean levels of depression declined during the emerging adulthood in females, but remained relatively stable in males. Maternal depressive symptoms significantly positively predicted depressive symptoms across the entire emerging adulthood in females, but only at age 20-21 for males. In addition, likelihood of developing depressive symptoms was attenuated by higher global TEI in both females and males, and additionally by higher interpersonal skills in males. Our findings suggest that interventions for depressive symptoms in emerging adulthood should consider development of socioemotional competencies. Author Keywords: Depression, Depressive Symptoms, Emerging Adulthood, Intergenerational Risk, Longitudinal, Trait Emotional Intelligence
Influence of Canopy Water Partitioning on the Isotopic Signature of Plant Water in a Mixed Northern Forest
This study seeks to clarify the way in which the differing canopy characteristics among tree species influence the partitioning of precipitation, and therefore the source of water available for plant water uptake, in the Plastic Lake catchment near Dorset, ON. Three dominant tree species were compared: red oak (Quercus rubra), eastern white pine (Pinus strobus), and eastern hemlock (Tsuga canadensis). Above-canopy precipitation, throughfall, stemflow, and soil water content were monitored weekly from June 2016 until October 2016 and the 18O and 2H isotopic signatures of each were analyzed. Plant water and bulk soil water samples were also collected from five trees of each species at five stages of the growing season to compare the isotopic signature of xylem water to that of their surrounding soils. Both plant water and bulk soil water displayed evidence of isotopic fractionation; however, plant water was more depleted in δ2H and δ18O than bulk soil water. Water interacting with the tree canopies as throughfall and stemflow did not display significant evidence of isotopic fractionation. This suggests that the vegetation could have accessed an isotopically distinct source of water stored within the soil or that an unknown isotopic fractionation process occurred throughout this study. Author Keywords:
Why not give up? A study on the role of resourcefulness in goal pursuit
Past research suggests that taking a process oriented approach, setting clear and concrete goals, and using both conscious planning and proactive coping are the best methods to be successful with goal pursuit. Also the literature has found that individuals scoring higher in general resourcefulness tend to be more successful at achieving goals than their less resourceful counterparts. My thesis looked at these goal pursuit behaviours under the lens of resourcefulness using a mixed methods approach. After completing Rosenbaum’s self-control scale (1980) assessing general resourcefulness, participants took part in a semi-structured interview asking them about a recent goal they had set and how they dealt with interfering obstacles. The hope was hearing differences about how highly and less resourceful people discuss their goals and setbacks would give a deeper understanding about the characteristics of success. The themes emerging from the interviews were: blame and excuses versus understanding and growth, internal versus external factors, living in the moment versus conscious planning and magical versus realistic thinking. In contrast to low-scoring participants, highly resourceful individuals grew from their setbacks, were internally driven, consciously planned, and thought realistically about their goals. Less resourceful individual, on the other hand blamed outside factors and made excuses, were only motivated externally, didn’t plan out their goals and believed their goals would just magically materialize over time. My discussion focuses on the ability to train lower resourceful individuals over longer interventions, and the applications of understanding and using resourcefulness as a lens in future studies. Author Keywords: Goal, Habits, Quitting, Resourcefulness, Self-Control, Success
Analysis and reactions of aqueous selenide and other reduced inorganic selenium compounds under anoxic conditions
Selenide is cited as a geochemically important selenium (Se) species, but it is unknown whether selenide is a stable aqueous ion in natural waters. The feasibility of using anoxic anion exchange chromatography (AEC) coupled to dynamic reaction cell-inductively coupled plasma-mass spectrometry to separate aqueous selenide was investigated with the goal of quantifying this anion to determine its importance in reducing waters. It was possible to qualitatively identify selenide using AEC, but much of the aqueous selenide oxidises to Se0 faster than the separation procedure could be completed. AEC analyses of solutions containing polyselenides produced peaks for unidentified Se compounds, which have been assigned tentative structures Se2O22-, Se2O32-, and Se2O62- based on close matches in retention time to stable S compounds. The results of this work show that aqueous selenide can be qualitatively observed in synthetic solutions using AEC, but it is unknown whether these conditions are relevant to natural waters. Author Keywords: anoxic speciation, polyselenides, selenide, selenium geochemistry, selenium speciation, selenoselenate
Assessing habitat suitability and connectivity for an endangered salamander complex
Habitat loss and fragmentation have significantly contributed to amphibian population declines, globally. Evaluating the state of remaining habitat patches can prove to be beneficial in identifying areas to prioritize in conservation efforts. Pelee Island, Ontario is home to a complex of salamanders including small-mouthed salamanders (Ambystoma texanum), blue-spotted salamanders (A. laterale) and unisexual Ambystoma (small-mouthed salamander dependent population). These populations have declined from intense landscape changes since the late 1800s, particularly from the historical drainage of wetlands. In this thesis, I evaluated the suitability and connectivity of habitat patches occupied by these salamanders to assess the size of, and dispersal capabilities between, remaining habitat patches. I found that there was a low amount of suitable terrestrial habitat available for this complex of salamanders, and existing habitat patches were small and isolated. Forested areas and non-breeding wetlands were considered to be suitable habitat when adjacent to existing breeding locations, suggesting that these habitats should be a focus for conservation efforts. Notably, intervention may be necessary to maintain this amphibian complex as many assemblages are isolated from one another and potential corridors currently consist of primarily unsuitable habitat. Given that much of the salamander complex is reliant on one species for reproduction, the long-term viability of this population of Ambystoma salamanders may rely on the enhancement of suitable habitat near current breeding sites by conservation organizations and local stakeholders. Ultimately, the approach used in this thesis emphasizes the value of evaluating habitat within a fragmented landscape to focus conservation efforts on imperilled species. Author Keywords: amphibians, connectivity, habitat suitability, landscape fragmentation, landscape resistance, unisexual
Application of Data Science to Paramedic Data
Paramedic data has significant potential for research. Paramedics see many patients every year and collect a wide variety of crucial data at each encounter. This data is rarely used for good reason: it’s messy and hard to work with. But like theunderdog character in a classic movie, with a little bit of work and a lot of understanding, paramedic data has significant potential to change the world of medical research. Paramedics throughout the world are involved in research every day, but most of this research uses purpose-built data structures and never takes advantage of the existing data that paramedics create as part of their everyday work. Through a project-based approach grounded in developing a better understanding of the opioid crisis, this thesis will examine the quantity and structure of the existing paramedic data, the complexities of its current design, the steps necessary to access it, and the processes necessary to clean existing data to a point where it can be easily modelled. Once we have our dataset, we will explore the challenges of choosing key metrics by examining the effectiveness of metrics currently employed to monitor the opioid crisis and the influences public health programs and changing policies have had on these metrics. Next, we will explore the temporal distributions of opioid and other intoxicant use with an eye to providing data to support public health in their harm reduction efforts. And lastly, we will look at the effect of fixed- and floating-point temporal influences on intoxicant-related calls with an eye to how these temporal points can affect call volumes. By using this exploration of the opioid crisis, this thesis will show that with a more thorough understanding of what paramedic data is, what data points are available, and the processes needed to transform it, paramedic data has the potential to greatly expand the limits of health care data science into a more precise and more all-encompassing discipline. Author Keywords: Ambulance, Data Science, Opioid, Overdose, Paramedic, Pre-hospital
Cognitive Inefficiencies in Adolescents with Eating Disorders
Eating Disorders (ED) are notoriously difficult to treat due, in part, to commonly observed inefficiencies in cognitive flexibility and central coherence, which are believed to maintain disordered cognitions and behaviours and negatively impact prognosis. Cognitive remediation therapy (CRT) has recently been used effectively with adults with ED; however, evidence among adolescents is limited. The present study explored change in flexibility and central coherence in a group of 23 adolescent ED inpatients (M = 16 years, SD = 0.95). All participants received a comparable dose of ED treatment. Participants were split into two groups for comparison: the CRT group (n = 15) received CRT in addition to TAU; and a TAU group for control (TAU; n = 8). Improvements in flexibility and central coherence were superior in the CRT group, suggesting that CRT is a potentially useful treatment for adolescents with AN as part of an overall psychosocial rehabilitation program. Author Keywords: anorexia nervosa, central coherence, cognitive flexibility, cognitive remediation, eating disorders, set shifting
Augmented Reality Sandbox (Aeolian Box)
The AeolianBox is an educational and presentation tool extended in this thesis to represent the atmospheric boundary layer (ABL) flow over a deformable surface in the sandbox. It is a hybrid hardware cum mathematical model which helps users to visually, interactively and spatially fathom the natural laws governing ABL airflow. The AeolianBox uses a Kinect V1 camera and a short focal length projector to capture the Digital Elevation Model (DEM) of the topography within the sandbox. The captured DEM is used to generate a Computational Fluid Dynamics (CFD) model and project the ABL flow back onto the surface topography within the sandbox. AeolianBox is designed to be used in a classroom setting. This requires a low time cost for the ABL flow simulation to keep the students engaged in the classroom. Thus, the process of DEM capture and CFD modelling were investigated to lower the time cost while maintaining key features of the ABL flow structure. A mesh-time sensitivity analysis was also conducted to investigate the tradeoff between the number of cells inside the mesh and time cost for both meshing process and CFD modelling. This allows the user to make an informed decision regarding the level of detail desired in the ABL flow structure by changing the number of cells in the mesh. There are infinite possible surface topographies which can be created by molding sand inside the sandbox. Therefore, in addition to keeping the time cost low while maintaining key features of the ABL flow structure, the meshing process and CFD modelling are required to be robust to variety of different surface topographies. To achieve these research objectives, in this thesis, parametrization is done for meshing process and CFD modelling. The accuracy of the CFD model for ABL flow used in the AeolianBox was qualitatively validated with airflow profiles captured in the Trent Environmental Wind Tunnel (TEWT) at Trent University using the Laser Doppler Anemometer (LDA). Three simple geometries namely a hemisphere, cube and a ridge were selected since they are well studied in academia. The CFD model was scaled to the dimensions of the grid where the airflow was captured in TEWT. The boundary conditions were also kept the same as the model used in the AeolianBox. The ABL flow is simulated by using software like OpenFoam and Paraview to build and visualize a CFD model. The AeolianBox is interactive and capable of detecting hands using the Kinect camera which allows a user to interact and change the topography of the sandbox in real time. The AeolianBox’s software built for this thesis uses only opensource tools and is accessible to anyone with an existing hardware model of its predecessors. Author Keywords: Augmented Reality, Computational Fluid Dynamics, Kinect Projector Calibration, OpenFoam, Paraview
Changes in Forms of Uranium in Anoxic Lake Sediments and Porewaters Near an Abandoned Uranium Mine, Bancroft, Ontario
Soluble uranium (U) has been observed continuously in the porewaters of Bentley Lake, a lake with semi-permanent anoxic sediments, despite the fact that reduced U(IV) is known to be insoluble. To be able to predict the fate and mobility of U that has been deposited in lake sediments, it is very important to understand the factors that determine soluble uranium in anoxic environments. Understanding soluble U species is crucial for predicting its behavior in natural systems as well as for the development of U remediation schemes. To explore the factors affecting soluble U in natural environments, anoxic lake sediments and porewaters were tested using two analytic methods, ICP-MS and ESI-HR-MS. Reduced uranium (U(IV)) can be precipitated as U(IV)-NdF3. Using this method revealed that most of the uranium in porewater is not able to be co-precipitated with NdF3. In addition, UO2+ was found using ESI-HR-MS, showing uranyl ions exist in reduced porewater. However, the UO2+ might be attached to some organic groups rather than present as free ions. Seasonal variation and air exposure experiments on the mobility of U between sediments and porewater were observed to test for changes of the redox state of U as a function of sample collection and storage. The results of this study will contribute to better remediation strategies for U tailings and will help U mining operations in the future. Author Keywords:


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