Physical Sciences and Mathematics Commons^™

Luminescence And Structural Properties Of Silicon-Germanium Quantum Structures Fabricated By Ion Implantation, Matheus Coelho Adam

Electronic Thesis and Dissertation Repository

The advancement of semiconductor materials has played a crucial role in driving positive technological breakthroughs that impact humanity in numerous ways. The presence of defects significantly alters the physical properties of semiconductors, making their analysis essential in the fabrication of semiconductor devices. I presented a new method to quantify surface and near-surface defects in single crystal semiconductors. Epitaxially-grown silicon was measured by low energy electron diffraction (LEED) to obtain the surface Debye temperature (θ_D). The results showed the surface θ_D of bulk Si (001), 1.0 μm, and 0.6 μm Si on sapphire of 333 K, 299 K, …

Attribution Robustness Of Neural Networks, Sunanda Gamage

Electronic Thesis and Dissertation Repository

While deep neural networks have demonstrated excellent learning capabilities, explainability of model predictions remains a challenge due to their black box nature. Attributions or feature significance methods are tools for explaining model predictions, facilitating model debugging, human-machine collaborative decision making, and establishing trust and compliance in critical applications. Recent work has shown that attributions of neural networks can be distorted by imperceptible adversarial input perturbations, which makes attributions unreliable as an explainability method. This thesis addresses the research problem of attribution robustness of neural networks and introduces novel techniques that enable robust training at scale.

Firstly, a novel generic framework …

Modeling Thermosyphon And Heat Pipe Performance For Mold Cooling Applications, Dwaipayan Sarkar

Electronic Thesis and Dissertation Repository

Thermosyphons are enhanced heat transfer devices that can continuously transfer very large amounts of heat rapidly over long distances with small temperature differences. The high heat transfer rate is achieved through simultaneous boiling and condensation of the working fluid and the continuous heat transfer is achieved through recirculation of the working fluid in its liquid and vapor phase. A potentially important application of the thermosyphons has been towards reducing the cycle times of the mold cooling processes which would provide economic incentives to the automotive industry.

Different operational and geometrical parameters such as the input heating power, fill ratio (FR), …

Controls On Plastic Debris Capture In Urban Stormwater Drains Of London, Canada: A Study Within The Great Lakes Watershed, Nina Kozikowski

Electronic Thesis and Dissertation Repository

Land-based sources are the greatest contributors of plastic pollution in aquatic environments. Prior to this investigation, there were no available studies concerning the number and types of plastic debris items between 1 mm and 5 mm captured in urban stormwater drains. The present study examined macroplastic (>5 mm) and large microplastic (1-5 mm) debris that accumulated in LittaTrap^TM devices at six drain sites over four seasonal periods in London, Ontario, Canada. Macroplastics (MaPs) and microplastics (MPs) were found in all 36 samples, and the totals ranged from 5-158 MaPs and 18-359 MPs per trap. Out of the 118 …

A Target-Based And A Targetless Extrinsic Calibration Methods For Thermal Camera And 3d Lidar, Farhad Dalirani

Electronic Thesis and Dissertation Repository

This thesis introduces two novel methods for the extrinsic calibration of a thermal camera and a 3D LiDAR sensor, which are crucial for seamless data integration. The first method employs a distinctive calibration target, leveraging lines and plane equations correspondence in both modalities for a single pose, and incorporating more poses by matching the target's edges. It achieves reliable results, even with just one pose yielding 10.82% translation and 0.51-degree rotation errors. This outperforms alternative methods, which require eight pairs for similar results. The second method eliminates the need for a dedicated target. Instead, by collecting data during the sensor …

Luminescent Group 11 Metal (I) Chalcogen Clusters With A Conjugated Diphosphine Ligand, Kai Yu Jeffrey Li

Electronic Thesis and Dissertation Repository

Polynuclear Au (I) complexes exhibit rich photochemical properties and have the potential to find applications as molecular sensors, switches, or energy storage devices. Although dinuclear Au (I) complexes with bridging diphosphines have been extensively examined, most of those reported do not contain rigid-diphosphine ligands.

This thesis examines how the rigid diphosphine, 4,6-bis(diphenylphosphino)dibenzofuran (DBFDP) can be incorporated for the controlled assembly of photoluminescent gold (I) metal – chalcogenolate (chalcogenolate = RS^-, RSe^-; R = organic moiety) and gold (I) chalcogenide (chalcogenide = S^2-, Se^2-) bimetallic complexes. In these studies, the chalcogen …

Exploring The Reactivity Of Metal-Ligand Cooperative Complexes With Dioxazolones, Terminal Alkynes, And 2-Ethynylbenzyl Alcohol, Megan A. Hoffer Miss

Electronic Thesis and Dissertation Repository

N-Acyl ketenimines were attempted to be synthesized catalytically by [Ru(Cp)(P^Ph₂N^Ph₂)(NCMe)]PF₆ with phenylacetylene and 3-phenethynyl-1,2,4-dioxazol-5-one. Trapping agents were employed to identify the major product of the reaction, as many products were formed. [Ru(Cp)(P^Ph₂N^Ph₂)(NCMe)]PF₆ reacts with 3-phenethynyl-1,2,4-dioxazol-5-one generating an isocyanate via the Curtius rearrangement, confirmed by a forced Curtius rearrangement with 3-phenethynyl-1,2,4-dioxazol-5-one and 1,2,4-triazole. Rates of vinylidene formation using [Ru(Cp)(P^Ph₂N^Ph₂)(NCMe)]PF₆ and various terminal alkynes of different sterics and electronics were evaluated using a Hammett analysis for and simple rate comparisons. …

Enhancing Urban Life: A Policy-Based Autonomic Smart City Management System For Efficient, Sustainable, And Self-Adaptive Urban Environments, Elham Okhovat

Electronic Thesis and Dissertation Repository

This thesis proposes the concept of the Policy-based Autonomic Smart City Management System, an innovative framework designed to comprehensively manage diverse aspects of urban environments, ranging from environmental conditions such as temperature and air quality to the infrastructure which comprises multiple layers of infrastructure, from sensors and devices to advanced IoT platforms and applications. Efficient management requires continuous monitoring of devices and infrastructure, data analysis, and real-time resource assessment to ensure seamless city operations and improve residents' quality of life. Automating data monitoring is essential due to the vast array of hardware and data exchanges, and round-the-clock monitoring is critical. …

Adaptation Reshapes The Distribution Of Fitness Effects, Diego Tenoch Morales Lopez

Electronic Thesis and Dissertation Repository

The process of adaptation has been of interest since the XIX century, when Darwin first proposed the idea of natural selection. Since then, there has been a myriad of theoretical and empirical works that have expanded the field. From the many evolutionary insights these works have produced, a foundational idea is that spontaneous mutations in the genome of organisms can produce changes to their reproductive success that might confer an advantage for the mutant organisms with respect to their peers. Therefore, mutations drive adaptive evolution by virtue of their heritable effects on fitness. Empirical measures of the distribution of these …

Population Dynamics And Bifurcations In Predator-Prey Systems With Allee Effect, Yanni Zeng

Electronic Thesis and Dissertation Repository

This thesis investigates a series of nonlinear predator-prey systems incorporating the Allee effect using differential equations. The main goal is to determine how the Allee effect affects population dynamics. The stability and bifurcations of the systems are studied with a hierarchical parametric analysis, providing insights into the behavioral changes of the population within the systems. In particular, we focus on the study of the number and distribution of limit cycles (oscillating solutions) and the existence of multiple stable states, which cause complex dynamical behaviors. Moreover, including the prey refuge, we examine how our method benefits the low-density animals and affects …

Learning Mortality Risk For Covid-19 Using Machine Learning And Statistical Methods, Shaoshi Zhang

Electronic Thesis and Dissertation Repository

This research investigates the mortality risk of COVID-19 patients across different variant waves, using the data from Centers for Disease Control and Prevention (CDC) websites. By analyzing the available data, including patient medical records, vaccination rates, and hospital capacities, we aim to discern patterns and factors associated with COVID-19-related deaths.

To explore features linked to COVID-19 mortality, we employ different techniques such as Filter, Wrapper, and Embedded methods for feature selection. Furthermore, we apply various machine learning methods, including support vector machines, decision trees, random forests, logistic regression, K-nearest neighbours, na¨ıve Bayes methods, and artificial neural networks, to uncover underlying …

High-Performance Computing In Covariant Loop Quantum Gravity, Pietropaolo Frisoni

Electronic Thesis and Dissertation Repository

This Ph.D. thesis presents a compilation of the scientific papers I published over the last three years during my Ph.D. in loop quantum gravity (LQG). First, we comprehensively introduce spinfoam calculations with a practical pedagogical paper. We highlight LQG's unique features and mathematical formalism and emphasize the computational complexities associated with its calculations. The subsequent articles delve into specific aspects of employing high-performance computing (HPC) in LQG research. We discuss the results obtained by applying numerical methods to studying spinfoams' infrared divergences, or ``bubbles''. This research direction is crucial to define the continuum limit of LQG properly. We investigate the …

Hydrogen Bond Activation Of Donor Acceptor Cyclopropanes, Matthew H.J. Pamenter

Electronic Thesis and Dissertation Repository

Donor acceptor cyclopropanes (DACs) are versatile organic building blocks used in the synthesis of many pharmaceutically relevant heterocycles. The combination of a high ring strain cyclopropane core and vicinal donor and acceptor substituents cause DACs to behave like 1,3-zwitterions. Recently, DACs have been activated by a hydrogen bond donor solvent in place of a Lewis acid catalyst, allowing the elimination of heavy metals commonly used in these transformations. Hexafluoroisopropanol (HFIP) as a hydrogen bond donor cosolvent was found to cause a downfield shift of the DACs electrophilic carbon in the 13C NMR spectrum. This indicates increased electrophilicity at this position …

Patterned Heating Induced Propulsion, Saajid A. Aman

Electronic Thesis and Dissertation Repository

This study explores propulsion effects generated by patterned heating acting on smooth and corrugated surfaces. The model problem assumes that the upper plate moves freely, and the lower plate is stationary, equipped with grooves, and exposed to spatially distributed heating. Our findings identify two distinct propulsion effects: thermal streaming and thermal drift. Thermal streaming occurs when given sufficient heating intensity with net flow in the left or right direction characterized by a pitchfork bifurcation. The efficiency of this technique can be controlled using the wavelength of heating. Thermal drift represents a pattern interaction effect. Its strength depends on the relative …

Series Expansions Of Lambert W And Related Functions, Jacob Imre

Electronic Thesis and Dissertation Repository

In the realm of multivalued functions, certain specimens run the risk of being elementary or complex

to a fault. The Lambert $W$ function serves as a middle ground in a way, being non-representable by elementary

functions yet admitting several properties which have allowed for copious research. $W$ utilizes the

inverse of the elementary function $xe^x$, resulting in a multivalued function with non-elementary

connections between its branches. $W_k(z)$, the solution to the equation $z=W_k(z)e^{W_k(z)}$

for a "branch number" $k \in \Z$, has both asymptotic and Taylor series for its various branches.

In recent years, significant effort has been dedicated to exploring …

Revealing The Core Dynamics Of Vesta: Insights From Experimental Investigations Of Electrical Resistivity And Thermal Conductivity, Oluwasanmi A. Orole Mr

Electronic Thesis and Dissertation Repository

Insights from high pressure and temperature experiments involving in-situ measurements of the electrical resistivity of Fe-5wt%Ni at temperatures of up to 2000 K, under pressures of 2-5 GPa in a 1000-ton cubic-anvil press have been used to reveal Vesta’s core dynamics. The Wiedemann–Franz law was used to calculate the thermal conductivity from the measured electrical resistivity data. Comparing the findings of this study with prior investigations on both pure Fe and Fe-10wt%Ni indicates that an increase in Ni ranging from 0-10wt% has negligible effect on the electrical resistivity of Fe alloys. By comparing the range of estimated heat flux through …

Multi-Arm Randomized Control Trials In Inflammatory Bowel Disease: A Literature Review And An Illustration Of Methods For Analysis, Sahiba Saini

Electronic Thesis and Dissertation Repository

This thesis aimed to review the literature on multiple-arm randomized control trials in inflammatory bowel disease (IBD) and to illustrate how to analyze these trials, focusing on appropriately controlling the type 1 error rates. The literature review found 247 trials published from the inception of each database to April 2014, of which 122 (49%) trials were multiple-arm trials and of those, 59 (48%) trials were on ulcerative colitis and 63 (52%) on Crohn’s disease. A published assessment tool was adopted to assess whether controlling of Type I error rates was needed. Despite the common use of this trial design and …

Empirical Nonlinear Site Response Applicable To Greater Vancouver, British Columbia, Natalia Gomez Jaramillo

Electronic Thesis and Dissertation Repository

In Greater Vancouver, strong earthquake shaking has not been recorded to quantify expected nonlinear soil response. Earthquake horizontal to vertical spectral ratios (eHVSR) are evaluated at seismic stations located at the edges or deeper center of sedimentary basins in Mexico City, the Kanto basin and Anchorage with available weak-to-strong motion recordings that have similar linear site response to Greater Vancouver to constrain the expected nonlinear soil response for future large earthquakes affecting Greater Vancouver. The empirical results confirm that the very low fundamental frequency (f₀ < 0.6 Hz) at deep Fraser River delta sites will be less affected by strong shakings and suggest that for Fraser River delta edge sites the amplification at the predominant frequency (f₁) could increase up to 1.77 times with a strong event. This thesis’ …

Experimental And Simulation Study Of Reactive Silver Ink Droplet Evaporation, Weipeng Zhang

Electronic Thesis and Dissertation Repository

The evaporation of particle-free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and films. In this thesis, COMSOL Multiphysics simulations of the solvent (water-ethylene glycol mixture) droplet evaporation process are used to explain the microflows, mass transfers, and heat distribution responsible for the experimental observations. The reactive ink incorporates fluoro-surfactant FS-31 and poly (acrylamide) (PAM) to suppress the coffee-ring effect that negatively impacts the electrical conductivity. Experiments show that the droplet evaporation process results in varied silver particle morphology, depending on the locations within the droplet, leading to uneven surfaces. Large particles (3 …

Deformation And Evolution Of Achondrite Parent Bodies, Yaozhu Li

Electronic Thesis and Dissertation Repository

Minerals in planetary bodies record accumulated strain from deformation events such as hypervelocity impacts but potentially also parent body processes such as gravitational compaction. This work investigates olivine microstructural features that may distinguish between different impact levels versus parent body plastic deformation regimes. Achondritic meteorites from the ureilite parent body, the Moon, Mars as well as terrestrial basalt and mantle xenolith have been investigated using micro-XRD, EBSD, micro-XRF and other methods to study their parent body deformation history. A Matlab® method, unit segment length (USL), is herein developed to visualize the crystal boundary geometry and quantify the apparent subboundary density …

Local Model Agnostic Xai Methodologies Applied To Breast Cancer Malignancy Predictions, Heather Hartley

Electronic Thesis and Dissertation Repository

This thesis examines current state-of-the-art Explainable Artificial Intelligence (XAI) methodologies applicable to breast cancer diagnostics, as well as local model-agnostic XAI methodologies more broadly. It is well known that AI is underutilized in healthcare due to the fact that black box AI methods are largely uninterpretable. The potential for AI to positively affect health care outcomes is massive, and AI adoption by medical practitioners and the community at large will translate to more desirable patient outcomes. The development of XAI is crucial to furthering the integration of AI within healthcare, as it will allow medical practitioners and regulatory bodies to …

Study Of Behaviour Change And Impact On Infectious Disease Dynamics By Mathematical Models, Tianyu Cheng

Electronic Thesis and Dissertation Repository

This thesis uses mathematical models to study human behaviour changes' effects on infectious disease transmission dynamics. It centers on two main topics. The first concerns how behaviour response evolves during epidemics and the effects of adaptive precaution behaviour on epidemics. The second topic is how to build general framework models incorporating human behaviour response in epidemiological modelling.

In the first project, based on the fact that a fraction of the epidemiologically susceptible population is actually susceptible due to precautions, we present a novel perspective on understanding the infection force, incorporating human protection behaviours. This view explains many existing infection force …

Short-Term Versus Long-Term Effects Of Nitrogen Addition And Warming On Ecosystem N Dynamics In A Grass-Dominated Temperate Old Field, Benjamin F. A. Souriol

Electronic Thesis and Dissertation Repository

Increased atmospheric nitrogen (N) deposition and climate warming are both anticipated to influence the ecosystem N dynamics of northern temperate ecosystems substantially over the next century. Nevertheless, in field experiments with N addition and warming treatments, temporal scale can play an important role in determining the extent of treatment effects on N dynamics, and it is unclear to what extent the results of short-term studies can be extrapolated to responses over longer time scales. I compared the short-term versus long-term effects of N addition and warming on net N mineralization, N leaching, and N retention in a grass-dominated old field. …

Observation And Modelling Of Meter-Class Earth Impacting Asteroids, David L. Clark

Electronic Thesis and Dissertation Repository

Earth is constantly bombarded by solar system objects of a wide variety of sizes, from micron-sized meteoroid stream and sporadic meteor dust, to meter-sized and larger meteoroids observed as fireballs. Fireball event characteristics directly point to the properties and structure of the parent body from which the meteoroid originated. In-atmosphere fireball data paired with in-space observations bring much context to both observations. This thesis centres on three published papers that grew out of my Masters project to identify precovery in-space images of meteoroids first observed as fireballs.

The first article describes the first successful identification of an in-space image of …

Parameter Estimation For Normally Distributed Grouped Data And Clustering Single-Cell Rna Sequencing Data Via The Expectation-Maximization Algorithm, Zahra Aghahosseinalishirazi

Electronic Thesis and Dissertation Repository

The Expectation-Maximization (EM) algorithm is an iterative algorithm for finding the maximum likelihood estimates in problems involving missing data or latent variables. The EM algorithm can be applied to problems consisting of evidently incomplete data or missingness situations, such as truncated distributions, censored or grouped observations, and also to problems in which the missingness of the data is not natural or evident, such as mixed-effects models, mixture models, log-linear models, and latent variables. In Chapter 2 of this thesis, we apply the EM algorithm to grouped data, a problem in which incomplete data are evident. Nowadays, data confidentiality is of …

Thermal And Fluid Evolution Of The Clearwater West Impact-Generated Hydrothermal System, Quebec, And Associated Astrobiological Implications, Daliah R. Bibas

Electronic Thesis and Dissertation Repository

Impact-generated hydrothermal systems result from interactions between a permeable substrate, an impact-generated heat source, and fluids (e.g., H₂O). A comprehensive understanding of the evolution of these terrestrial features has significant implications in the search for habitable environments on Mars, a focus in the emerging field of astrobiology. This thesis presents a detailed case study of the impact-generated hydrothermal alteration of impactites at the Clearwater West impact structure, Quebec, focusing on hydrothermally precipitated quartz vugs in crater-fill impact melt rocks. Sample analysis included optical microscopy, electron microprobe analysis, mass spectrometry, and fluid inclusion microthermometry. Results show 3 main quartz …

Nonparametric Methods For Analysis And Sizing Of Cluster Randomization Trials With Baseline Measurements, Chengchun Yu

Electronic Thesis and Dissertation Repository

Cluster randomization trials are popular in situations where the intervention needs to be implemented at the cluster level, or logistical, financial and/or ethical reason dictates the choice for randomization at the cluster level, or minimization of contamination is needed. It is very common for cluster trials to take measurements before randomization and again at follow-up, resulting in a clustered pretest-posttest design. For continuous outcomes, the cluster-adjusted analysis of covariance approach can be used to adjust for accidental bias and improve efficiency. However, a direct application of this method is nonsensical if the measures are incompatible with an interval scale, yet …

Protein Stability In Solution And In The Gas Phase., Yousef Haidar

Electronic Thesis and Dissertation Repository

Electrospray Ionization mass spectrometry (ESI-MS) is widely used for probing proteins, yet many aspects of this technique remain elusive. Using MS, ion mobility spectrometry (IMS), and circular dichroism (CD) spectroscopy, this thesis sheds light on the stability differences of proteins in the gas phase and solution. After a general introduction (Chapter 1), Chapter 2 scrutinizes some aspects of native ESI. Our data highlight the significance of cone voltage in maintaining a native-like fold and show the advantage of using NH₄Ac in protein experiments. Chapter 3 focuses on hydrogen/deuterium exchange (HDX)-MS. Several studies have reported that D₂O …

Interplay Of Forces In Impinging Jet Flow And Circular Hydraulic Jump, Abdelkader Baayoun

Electronic Thesis and Dissertation Repository

The circular liquid jet impingement with subsequent hydraulic jump formation is studied theoretically using boundary-layer and thin-film approaches. Three different scenarios are tackled, namely, an accelerated Newtonian jet impinging on a stationary disk, a steady Newtonian jet impinging on a rotating disk, and a steady viscoelastic liquid jet impinging on a stationary disk. Accordingly, the effects of jet acceleration, gravity, centrifugal forces, and fluid elasticity on the flow behaviour and the jump are examined. The results are validated against numerical simulation and existing measurements. The findings show that the thickness of the boundary layer developing near impingement diminishes with jet …

Feasibility Of Functional Mri On Point-Of-Care Mr Platforms, Arjama Halder

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a clinically valuable tool that can produce anatomical and functional images with improved soft tissue contrast compared to other imaging modalities. There has recently been a surge in low- and mid-field scanners due to hardware developments and innovative acquisition techniques. These compact scanners are accessible, offer reduced siting requirements and can be made operational at a reduced cost.

This thesis aims to implement blood-oxygen-level-dependent (BOLD) resting-state functional MRI (fMRI) at such a mid-field point-of-care scanner. The availability of this technique can be beneficial to get neurological information in cases of traumatic brain …