title: Perceptual difficulty effects on memory: The benefit of incongruency for subsequent retention

contributor:
Milliken, Robert Bruce
Psychology

subject: attention memory

abstract: This thesis examined the intersection between processing difficulties at encoding and subsequent retention. A number of reported effects describe the finding of better memory performance for items that were difficult to process in an earlier study phase compared to items that were easy to process—a finding broadly captured by the desirable difficulty principle (Bjork, 1994; Bjork & Bjork, 2011). The Introduction provides an overview of several of these effects, as well as an evaluation of theoretical frameworks that may help us understand the cognitive processes that may be shared across them. The empirical work focuses specifically on one memory effect—better recognition for targets formerly presented on incongruent as opposed to congruent trials in a selective attention task. The effects reviewed in the Introduction, including the one studied in the three empirical chapters, all involve difficulty in processing target information in a relatively simple perceptual identification task. The work covered in this thesis demonstrates that manipulations of perceptual features reliably benefit subsequent memory when the difficulty directs additional processing toward higher-order features. Furthermore, the memory test must appropriately tap into these conceptual feature representations at retrieval. The implications of these findings is discussed in the context of the desirable difficulty literature, as well as the attention and memory literatures more broadly.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)

abstract: The way we pay attention to information influences how well we remember it later. Although this link seems intuitive, research on this topic has led to a complex literature with mixed results and several different theoretical perspectives. Specifically, several memory effects have been reported that describe better memory performance for items that were difficult to process during learning compared to items that were easy to process. The theoretical goals of this thesis were to review several of these memory effects and to offer a more unified conceptual understanding of their underlying cognitive processes. The empirical goal of this thesis was to examine one such memory effect and place the findings in the context of the conceptual frameworks discussed.


title: Developing and validating an adhesive-based cell culture technique for airway epithelial cells with applications in cell patterning and microfluidic studies

contributor:
Hirota, Jeremy
Medical Sciences

abstract: Airway epithelial cell culture is largely performed under static conditions in conventional cell culture dishes, plates or flasks. These models are easily accessible and user-friendly, widely being used in diverse discovery research and drug development applications. However, static culture models do not incorporate dynamic forces of airflow or interstitial fluid flow that are experienced in vivo by airway epithelial cells. Recent advances in airway epithelial cell culture are beginning to incorporate dynamic forces. However, these models are often proprietary, require access to specialized equipment, trained personnel and facilities, all factors that restrict such methods from being widely adapted by biomedical researchers. To address this application requirement and technology gap, we have developed and tested the use of adhesives in airway epithelial cell culture that enables us to create micropatterns, apply the technique to a cell migration study and develop an accessible microfluidic chip for perfusion that involves minimal equipment. Our results display data that supports using adhesives for advanced airway epithelial cell culture models that provide an easily accessible system for cell micropatterning and introduction of dynamic forces.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: This work describes a versatile and cost-effective cell culture method for micropatterning adherent cells on a porous membrane using pressure-sensitive double-sided adhesives. This technique allows growing cells using conventional methods, and it enables an easy transfer of the cultured cells on the membrane to a microfluidic chip. The adhesives can also be used to form different patterns of cultured cells, which can be used to create a separation between groups of cells to study cell migration. In this thesis, we evaluate the toxicity effect of four different adhesives on two airway epithelial cell lines. We show that the bonding between the wet adhesive and the microchannel device is strong enough to allow perfusion. The ease of use and cost-effective model has the potential to assist biomedical researchers with research questions that may be presently difficult to assess in standard cell culture systems.


title: Six-Phase Voltage Source Inverter Efficiency Optimization Using Advanced Switching Techniques

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

abstract:
Since the late 1990s, lots of attention has been given to the development of multi-phase motor drives due to the momentous interest in developing greener methods of transportation and the increased benefits when compared to their three-phase counterparts. These benefits include improved fault-tolerant control, reduced torque ripple, improved motor power density, and reduced DC-link capacitance which has resulted in an amplified interest in multi-phase machines for electric ship propulsion, electric aircraft, and traction electric motors (electric and hybrid road vehicles). When looking specifically into multi-phase machines that are made up of six-phases, different topologies have been researched that include altering the phase shift between the different windings or winding sets as well as the number of neutral points within the machine. Out of all possible combinations, there are three common six-phase machine topologies studied in the literature. First is the six-phase machine with a 60 degree phase shift between each of the machine windings – referred to as an asymmetrical six-phase machine. The second and third topologies are a six-phase machine with two sets of three-phase windings where one winding set has a phase shift from the other winding set (typically 30 degrees. When the two winding sets have a shared neutral point, the machine is referred to as an asymmetrical six-phase machine. Alternatively, when the two winding sets have isolated neutral points, the machine is referred to as a dual three-phase machine.

From the recent surge in the literature regarding the added benefits of the dual three-phase machine compared to the other six-phase topologies, this thesis will mainly focus on the control and switching techniques specifically for the dual three-phase machine. With an in-depth analysis, the effect of different switching techniques will be observed on the overall efficiency of the six-phase voltage source inverter (VSI). Furthermore, using the Matlab/Simulink and PLECS environment with a dual three-phase drive system vector space decomposition (VSD) based model, an accurate drive model that incorporates the machine's dynamic behaviour and calculates the total losses of the VSI is also proposed. The VSI is connected to a 100 kW dual three-phase interior permanent magnet synchronous machine (IPMSM) and different switching techniques are applied to the inverter to properly control the six-phase drive system.

Similar to their three-phase counterparts, dual three-phase machines can be controlled using sinusoidal carrier-based pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM). This thesis explores the VSI efficiency when using different switching techniques proposed in the literature and proposes new techniques to improve the efficiency of the VSI. Additionally, a detailed plan for an experimental setup and testing procedure is provided for the switching techniques that are simulated throughout this thesis. This proposed testing procedure assumes a prototype six-phase VSI composed of six Infineon FF600R12IE4 IGBT modules that are connected to a dual three-phase 100 kW IPMSM. As the future work of this thesis includes experimental verification, the Matlab/Simulink drive model proposed in this thesis is designed with this particular setup in mind.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Big-Data Driven Optimization Methods with Applications to LTL Freight Routing

contributor:
Hassini, Elkafi
Computational Engineering and Science

subject:
Big-data driven optimization methods
Less-than-truckload freight routing

abstract:
We propose solution strategies for hard Mixed Integer Programming (MIP) problems,
with a focus on distributed parallel MIP optimization. Although our proposals are
inspired by the Less-than-truckload (LTL) freight routing problem, they are more
generally applicable to hard MIPs from other domains. We start by developing an Integer
Programming model for the Less-than-truckload (LTL) freight routing problem,
and present a novel heuristic for solving the model in a reasonable amount of time
on large LTL networks. Next, we identify some adaptations to MIP branching strategies
that are useful for achieving improved scaling upon distribution when the LTL
routing problem (or other hard MIPs) are solved using parallel MIP optimization.

Recognizing that our model represents a pseudo-Boolean optimization problem
(PBO), we leverage solution techniques used by PBO solvers to develop a CPLEX
based look-ahead solver for LTL routing and other PBO problems. Our focus once
again is on achieving improved scaling upon distribution. We also analyze a technique
for implementing subtree parallelism during distributed MIP optimization. We
believe that our proposals represent a significant step towards solving big-data driven
optimization problems (such as the LTL routing problem) in a more efficient manner.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
Less-than-truckload (LTL) freight transportation is a vital part of Canada's economy,
with revenues running into billions of dollars and a cascading impact on many
other industries. LTL operators often have to deal with large volumes of shipments,
unexpected changes in traffic conditions, and uncertainty in demand patterns. In an
industry that already has low profit margins, it is therefore vitally important to make
good routing decisions without expending a lot of time.

The optimization of such LTL freight networks often results in complex big-data
driven optimization problems. In addition to the challenge of finding optimal solutions
for these problems, analysts often have to deal with the complexities of big-data driven
inputs. In this thesis we develop several solution strategies for solving the LTL freight
routing problem including an exact model, novel heuristics, and techniques for solving
the problem efficiently on a cluster of computers.

Although the techniques we develop are inspired by LTL routing, they are more
generally applicable for solving big-data driven optimization problems from other
domains. Experiments conducted over the years in consultation with industry experts
indicate that our proposals can significantly improve solution quality and reduce
time to solution. Furthermore, our proposals open up interesting avenues for future
research.


title: Evaluating shrub expansion in a subarctic mountain basin using multi-temporal LiDAR data

contributor:
Carey, Sean
Earth and Environmental Sciences

subject:
LiDAR
Vegetation
Remote Sensing
GIS
Shrub Expansion

abstract: High-latitude ecosystems have experienced substantial warming over the past 40 years, which is expected to continue into the foreseeable future. Consequently, an increase in vegetation growth has occurred throughout the circumpolar North as documented through remote sensing and plot-level studies. A major component of this change is shrub expansion (shrubbing) in arctic and subarctic ecotones. However, these changes are highly variable depending on plant species, topographic position, hydrology, soils and other ecosystem properties. Changes in shrub and other vegetation properties are critical to document due to their first-order control on water, energy and carbon balances. This study uses a combination of multi-temporal LiDAR (Light Detection and Ranging) and field surveys to measure temporal changes in shrub vegetation cover over the Wolf Creek Research Basin (WCRB), a 180 km2 long-term watershed research facility located ~15 km south of Whitehorse, Yukon Territory. This work focuses on the smaller Granger Basin, a 7.6 km2 subarctic headwater catchment that straddles WCRB’s subalpine and alpine tundra ecozones with a wide range of elevation, landscape topography, and vegetation. Airborne LiDAR surveys of WCRB were conducted in August 2007 and 2018, providing an ideal opportunity to explore vegetation changes between survey years. Vegetation surveys were conducted throughout Granger Basin in summer 2019 to evaluate shrub properties for comparisons to the LiDAR. Machine learning classification algorithms were used to predict shrub presence/absence in 2018 based on rasterized LiDAR metrics with up to 97% overall independent accuracy compared to field validation points, with the best-performing model applied to the 2007 LiDAR to create binary shrub cover layers to compare between survey years. Results show a 63.3% total increase in detectable shrub cover > 0.45 m in height throughout Granger Basin between 2007 and 2018, with an average yearly expansion of 5.8%. These changes in detectable shrub cover were compared across terrain derivatives created using the LiDAR to quantify the influence of topography on shrub expansion. The terrain comparison results show that shrubs in the study area are located in and are preferentially expanding into lower and flatter areas near stream networks, at lower slope positions and with a higher potential for topographic wetness. The greatest differences in terrain derivative value distributions across the shrub and non-shrub change categories were found in terms of stream distance, elevation, and relative slope position. This expansion of shrubs into higher-resource areas is consistent with previous studies and is supported by established physical processes. As vegetation responses to warming have far-reaching influences on surface energy exchange, nutrient cycling, and the overall water balance, this increase in detectable shrub cover has a wide range of impacts on the future of northern watersheds. Overall, the findings from this research reinforce the documented increase in pan-Arctic shrub vegetation in recent years, quantify the variation in shrub expansion over terrain derivatives at the landscape scale, and demonstrate the feasibility of using LiDAR to compare changes in shrub properties over time.

abstract: Thesis

abstract: Master of Science (MSc)


title: Patient-Important Outcomes of Cardiac and Non-Cardiac Surgery: Describing the Landscape and Exploring Etiologies and Interventions

contributor:
Devereaux, PJ
Health Research Methodology

subject:
Perioperative Medicine
Non-cardiac surgery
Outcomes
Cardiac surgery

abstract:
The patient-important outcomes of cardiac and non-cardiac surgery are well-recognized but poorly understood. The causes of major morbidity and mortality in patients undergoing non-cardiac are not known. This is not the case in cardiac surgery, which is provided to a homogenous patient population that has been well-described through clinical registries. Recent improvements to the care of cardiac surgical patients have led to dramatic decreases in major morbidity and mortality. However, neurocognitive and functional impairments after cardiac surgery remain the most feared by patients and least understood by clinicians. This thesis comprises 6 chapters that inform these knowledge gaps and establish the basis upon which future research will be based.
Chapter 1 is an introduction providing the rationale for conducting each of the included studies.
Chapter 2 reports the VISION Mortality study, which explores the relationship between major complications and death within 30-days of undergoing inpatient, noncardiac surgery.
Chapter 3 reports a study validating the use of the Standardized Assessment of Global activities in the Elderly (SAGE) scale in patients undergoing cardiac surgery.
Chapter 4 presents a pilot observational study that establishes the feasibility of conducting a large, prospective cohort study to determine the relationship between decreases in cerebral saturation during cardiac surgery and postoperative functional decline.
Chapter 5 presents a pilot study conducted to inform the feasibility of a large, randomized cluster crossover trial examining whether an institutional policy of restricted benzodiazepine administration during cardiac surgery (compared to liberal administration) would reduce delirium after cardiac surgery.
Chapter 6 discusses the conclusions, limitations, and implications of the research presented in this PhD thesis.

abstract: Thesis

abstract: Candidate in Philosophy


title: ANALYSIS AND DESIGN OF NONLINEAR FIBER OPTIC COMMUNICATION SYSTEMS

contributor:
Kumar, Shiva
Electrical and Computer Engineering

subject:
Nonlinear optics
Fiber optic communication systems
Nonlinear Fourier transform
Optical back propagation

abstract:
Fiber-optic systems represent the backbone of the communication networks, carrying most of the world’s data traffic. The main bottleneck in today’s fiber-optic communication systems has roots in the inherent nonlinearity of the fiber. Hence, developing new transmission schemes that are compatible with the nonlinear behavior of the optical fiber has become necessary.

To utilize the full transmission capacity of an optical fiber, this thesis investigates two different techniques---compensation-based method and nonlinear Fourier transform (NFT).

For the purpose of suppressing the nonlinear distortion in real time, an optical back propagation (OBP) technique using Raman pumped dispersion compensating fibers (DCF). OBP, as an all-optical signal processing technique, can compensate for both intra- and inter-channel nonlinear impairments in real time in point-to-point systems as well as in optical networks. The proposed inline OBP module consists of an optical phase conjugator (OPC), amplifiers and a Raman pumped DCF. In order to suppress the nonlinear effects of the transmission fiber, the power in the OBP fiber should increase exponentially with distance. This can be approximately achieved by using Raman pumping of the backpropagation fiber. Simulation results show that this technique provides 7.7 dB  performance improvement in Q-factor over conventional systems.

The second part of this thesis is dedicated to the NFT as a promising framework to exploit the inherent nonlinearity of optical fiber rather than treating it as an undesirable effect and using perturbation and approximation-based methods to mitigate it.
A novel multistage perturbation technique to realize the NFT as a cascade of linear discrete Fourier transforms is developed. The linear Fourier transform can be easily implemented in the optical domain using a time lens or discrete photonic components, which can be implemented in silicon photonics. The proposed technique provides a promising way to implement NFT in the optical domain, which will fully utilize the potential of NFT for wavelength-division multiplexed fiber-optic systems in the optical domain.

Moreover, a nonlinear frequency-division multiplexed (NFDM) transmission scheme with midpoint OPC is investigated. The proposed mid-OPC NFDM system offers a degree of freedom to have a flexible power normalization factor, P_n to minimize the signal-noise mixing in NFT processing for a specific launch power, resulting in significant system performance improvement up to 5.6 dB in Q-factor over conventional NFDM systems. Another advantage of the proposed scheme is that the mid-OPC NFDM system extends the transmission reach without having to increase the guard interval, which leads to higher spectral efficiency.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Optimization Models and Algorithms for Pricing in e-Commerce

subject:
Pricing
Reference pricing
Mixed-integer nonlinear programming
Generalized Benders' decomposition
Customer rating
e-commerce
Quadratic programming
Personalized price discounts
Nonlinear programming

abstract:
With the rise of online retailer giants like Amazon, and enhancements in internet and mobile technologies, online shopping is becoming increasingly popular. This has lead to new opportunities in online price optimization. The overarching motivation and theme of this thesis is to review these opportunities and provide methods and models in the context of retailers' online pricing decisions.
In Chapter 2 a multi-period revenue maximization and pricing optimization problem in the presence of reference prices is formulated as a mixed integer nonlinear program. Two algorithms are developed to solve the optimization problem: a generalized Benders' decomposition algorithm and a myopic heuristic. This is followed by numerical computations to illustrate the effciency of the solution approaches as well as some managerial pricing insights.
In Chapter 3 a data-driven quadratic programming optimization model for online pricing in the presence of customer ratings is proposed. A new demand function is developed for a multi-product,  nite horizon, online retail environment. To solve the optimization problem, a myopic pricing heuristic as well as exact solution approaches are introduced. Using customer reviews ratings data from Amazon.com, a new customer rating forecasting model is validated. This is followed by several analytical and numerical insights.
In Chapter 4 a multinomial choice model is used for customer purchase decision to  find optimal personalized price discounts for an online retailer that incorporates customer locations and feedback from their reviews. Closed form solutions are derived for two special cases of this problem. To gain some analytical insights extensive numerical experiments are carried followed by several analytical and numerical insights.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: The increase in online retail and the improvements in mobile technologies has lead to advantages and opportunities for both customers and retailers. One of these advantages is the ability to keep and efficiently access records of historical orders for both customers and retailers. In addition, online retailing has dramatically decreased the cost of price adjustments and discounts compared to the brick and mortar environment. At the same time, with the increase in online retailing we are witnessing proliferations of online reviews in e-commerce platforms. Given this availability of data and the new capabilities in an online retail environment, there is a need to develop pricing optimization models that integrate all these new features. The overarching motivation and theme of this thesis is to review these opportunities and provide methods and models in the context of retailers' online pricing decisions.


title: Bad Avatar: Mad/Crip Digital Identity Play

contributor:
Brophy, Sarah
English and Cultural Studies

subject: disability studies; Mad studies; digital media; automedia; life writing; social media; video games; queer theory; feminism; digital humanities

abstract:
This thesis examines the fissures and intersections between feminist digital media, queer theory, and Mad and disability studies. Moving across social media platforms, hashtag data, and digital gaming, this project argues for the subversive and creative potential within Mad/crip/queer digital identity performances. My theorizing of the avatar as an automedial figure in this project is attentive to the politics of the face as a site of encounter, to digital bodies and movement, to identification and community-building, and to embodiment and affects that move between on- and off-screen lives.

This thesis follows the “bad avatar,” a collection of Mad digital identity practices that interrupt, disrupt, and transgress normalizing and normative digital spaces of North American settler capitalist culture. Claiming the bad avatar as a deliberate identity position is an act of claiming the label of “bad,” which here has multiple meanings: Mad queer bodies—physical and digital—are bad citizens because we break the heteronormative patriarchal rules. We’re troublemakers—we make trouble for power systems and those who embody power. We can be bad workers, unproductive and fatigued. We can be bad for capitalism and bad for nationalist morale. We also experience feelings that become pathologized and policed. As despair, panic, melancholy, and angst stick to our bodies our bodies themselves become framed as bad: sick, broken, wrong, a problem in need of fixing or eradication. Reclaiming “bad” is both a celebration of the willful subject (Ahmed 2014) and a challenge to the binary of “good/bad” that is used to oppress Mad and disabled bodies.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: This thesis theorizes the digital avatar as an automedial figure, a mode of virtual embodiment and a site of encounter. I use “avatar” to draw a connecting line between widely varied digital identity acts that occur across social media platforms and video games. This thesis examines the “bad avatar,” a collection of Mad/crip/disabled faces, bodies, and identity practices that interrupt, disrupt, and transgress the normalizing and normative digital spaces of North American settler capitalist culture. Mad/crip digital identity play offers avenues for enacting modes of resistance through the politics of representation and the processes of identity performance and community-building.


title: The Effects of Acute Psychosocial Stress on Inhibitory Control and Relationships with Treatment Outcome in Binge Eating Disorder

contributor:
Balodis, Iris M.
Neuroscience

subject:
binge eating disorder
stress
negative urgency
inhibitory control
stop-signal task
response inhibition

abstract: Background: Individuals with binge eating disorder (BED) experience a loss of control (i.e., poor inhibitory control) during binge eating, where stress is a common antecedent for binge episodes. However, few studies examine acute stress in BED and, to date, psychosocial stress relationships with inhibitory control are unexamined. Purpose: The current study investigated acute psychosocial stress effects on inhibitory control in BED. Additionally, inhibitory control relationships with BED treatment outcome were explored. Methods: Thirty-three individuals with BED were randomized to a stress (n = 17) or no stress condition (n = 16). All completed self-report measures including the Profile of Mood States and the Binge Urge Scale. Following the stressor, individuals completed the Stop-Signal Task (SST), a well-validated measure of inhibitory control. Relationships between post-stress anxiety with inhibitory control and eating pathology were explored. Furthermore, treatment outcome relationships with levels of inhibitory control, and negative urgency (an impulsive personality trait) were explored. Results: In the stress condition, individuals reported increased state anxiety immediately following stress, but experienced a decrease back to baseline levels of anxiety by the end of the SST. Stress resulted in impaired inhibitory control performance on the SST. Binge urges increased across both conditions over time. Measures of inhibitory control and negative urgency did not relate to treatment outcome. Conclusion: This study is novel in directly examining psychosocial stress effects on inhibitory control, which has not been studied in BED. These results show subjective stress effects in BED are short-lived; however, behaviourally, stress has a lingering effect on inhibitory control. Increasing binge urges across the experimental session in the no stress condition suggests a role for generalized anxiety on this impulse. These findings have clinical implications for binge urges as a therapeutic target, and for informing individuals with BED about the implications of stress on their binge eating.

abstract: Thesis

abstract: Master of Science (MSc)


title: On the Complexity of Several Mal'tsev Condition Satisfaction Problems

contributor:
Valeriote, Matthew
Mathematics and Statistics

subject: Universal Algebra

subject: General Algebra

subject: Mal'tsev Conditions

subject: MCSP

subject: Complexity

subject: Algebra

subject: Constraint Satisfaction

subject: CSP

abstract: In this thesis we derive novel results on the complexity of idempotent Mal'tsev condition satisfaction problems. For a Mal'tsev condition M, the idempotent M- satisfaction problem is the decision problem defined via: INPUT: A finite idempotent algebra A. QUESTION: Does A satisfy M? In particular we are able to prove that this decision problem is in the complexity class NP whenever M satisfi es one of the following conditions: 1. M is a strong Mal'tsev condition which implies the existence of a near unanimity term. 2. M is a strong Mal'tsev condition of height < 1 (see Definition 5.1.1). As a porism of these two results, we are able to derive the stronger result that the complexity of the idempotent M-satisfaction problem is in NP whenever M is a strong Mal'tsev condition which implies the existence of an edge term. On top of this we also outline a polynomial-time algorithm for the idempotent M-satisfaction problem when M is a linear strong Mal'tsev condition which implies the existence of a near unanimity term. We also examine the related search problem in which the goal is to produce operation tables of term operations of the algebra A which witness that A satisfies the Mal'tsev condition M whenever such terms exist (and otherwise correctly decide that such terms do not exist). We outline polynomial-time algorithms for this search problem for various strong Mal'tsev conditions. We close the thesis with a short list of open problems as suggested directions for further research.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Sexual conflict and plasticity in the fruit fly

contributor:
Dukas, Reuven
Psychology

subject:
sexual conflict
phenotypic plasticity
drosophila melanogaster
evolution
behaviour
genetics
sexual selection
mate choice

abstract:
Animals display considerable phenotypic variation in their mating traits, and this
variation can have important consequences for the evolution of dimorphic traits
between the males and females within a species. In chapter 1, I outline the current
state of our understanding of plasticity in reproductive phenotypes, and argue that
more work needs to be done to connect the gap between plasticity in mating traits
and the outcomes of sexual conflict. Across my four data chapters, I used the fruit
fly as a model organism in series of experiments that attempt to better understand
how plasticity in mating traits influences the fitness outcomes of both males and
females. In chapter 2, I experimentally manipulated the outcome of a fighting
experience, and found that males who win a previous fight have higher precopulatory
reproductive success, but losers perform better in post-copulatory
areas. In chapter 3, I manipulated the amount of competition that a male
experiences and found that females mated to males who experience competition
produce more early-life offspring but live shorter lives compared to females
mated to males that experience no competition. In chapter 4, I manipulated the
intensity of sexual conflict that a female experiences and found that males mated
to females who experience high conflict have lower pre- and post-copulatory
reproductive success compared to males mated to females who experience low
conflict. In chapter 5. I manipulated the degree of sexual aggression that a female
experiences, and found that females that experience harassment and mating from
a male that displays high sexual aggression is subsequently less choosy compared
to females that experience a less aggressive male. Finally, in chapter 6, I discuss
the significance of my results as they relate to the evolution of reproductive traits
in males and females.

abstract: Dissertation

abstract: Doctor of Science  (PhD)

abstract:
Considerable phenotypic variation exists both within and across species. Within
species, one source of this variation is phenotypic plasticity, the ability for an
individual to alter its phenotype based on environmental influences. When it
comes to sex, both males and females in many species exhibit striking variation in
their reproductive behaviour as a result of plasticity. However, the causes and
consequences of this variation are not well understood. Throughout my doctoral
dissertation, I used the fruit fly as a model to explore how various social
experiences such as fighting, competition, sexual harassment, and mating shape
the subsequent reproductive behaviour of males and females, and quantified the
evolutionary consequences of this variation. The results of my studies have
important implications for understanding the evolution of various behavioural
strategies such as aggression and mate choice.


title: Strategies for Fall Risk Assessment and Prevention in People With COPD

contributor:
Beauchamp, Marla K
Rehabilitation Science

subject:
COPD
Rehabilitation
Balance
Fall prevention

abstract: Chronic obstructive pulmonary disease (COPD) is a progressive lung disease comprising of respiratory-related and systemic effects, including impairments in balance. Balance impairments are especially problematic as they increase the risk of falling, potentially leading to negative outcomes such as hospitalization, disability, and death. The main objectives of this thesis were to 1. determine underlying balance impairments that distinguish between individuals with COPD with and without a history of falls and 2. explore facilitators and barriers of a home-based fall prevention program for people with COPD. The first study of this thesis was a secondary analysis of cross-sectional data that showed that the stability limits/verticality and postural responses subcomponents of the Balance Evaluation Systems Test (BESTest) distinguished between those with and without a fall history among 72 patients with moderate to severe COPD. The stability limits/verticality subcomponent also showed acceptable accuracy in identifying individuals with COPD at high risk of falls (cut-off score of 73.8%). In the second study, a qualitative analysis of interviews with 15 patients who completed a home-based fall prevention program, participants indicated that programs that are personalized and focus on providing support for older adults with COPD may help to improve adherence and reduce participants’ risk of falling. The findings from the two studies included in this thesis provide new knowledge for informing fall risk assessment and prevention for people with COPD.

abstract: Thesis

abstract: Master of Science (MSc)


title: MULTI-DOMAIN SELECTION OF APTAMERS FOR BACTERIAL PROTEINS: TARGETING FUSOBACTERIUM NUCLEATUM DNAK

contributor:
Li, Yingfu
Biochemistry and Biomedical Sciences

subject:
Aptamer
Selection
Fusobacterium nucleatum
DnaK
Functional DNA
Sensor
Colorectal Cancer

abstract: Aptamers are nucleic acid ligands that bind to a specific target molecule. They are discovered by in-vitro selection, whereby binding sequences are selected from a large library of random sequences through iterative affinity steps. Aptamers are used as molecular recognition elements in aptamer-based, as such, creating aptamers with high affinity and specificity to their targets is important to the field. Ligands with two binding sites have been reported to have enhanced binding affinity than ligands with one binding site. To improve the quality of aptamers for downstream applications, multidomain selection is proposed as a new method for selecting aptamers compatible with dimerization. Here, we applied the multidomain selection approach to Fusobacterium nucleatum DnaK and produced aptamers that target the N-terminal domain (NTD) and the C-terminal domain (CTD) of DnaK. The top aptamer for DnaK-NTD had a Kd of 59.7 nM, and for DnaK-CTD had a Kd of 202.0 nM. However, the aptamers did not bind to the full-length DnaK and could not be dimerized. Multiple-site binding offers greater flexibility in the design of detection systems, which could provide higher selectivity and sensitivity than aptamers found through standard approaches. Validation of a method to discover aptamers compatible with dimerization would result in the development of a targeted approach to discover high-quality aptamers for bacterial proteins that can be used in bacteria-detection techniques.

abstract: Thesis

abstract: Master of Science (MSc)


title: Effects of attentional focus and mental fatigue on performance and perceived exertion during exercise

contributor:
Bray, Steven
Kinesiology

subject:
Attentional Focus
Mental Fatigue
Perceived Exertion
Exercise

abstract: Mental fatigue impairs performance of physically-demanding tasks and increases rating of perceived exertion (RPE) while performing. However, there may be ways of overcoming such performance decrements. One possible method includes the use of attentionally focused instructions. Motor learning research has shown that externally focused instructions can lead to improved performance in comparison to internally focused instructions. The purpose of the present study was to investigate the moderating effect of attentional focus on the mental fatigue – endurance performance relationship as well as the mental fatigue – perceived exertion relationship. Undergraduate students (N = 78) completed two wall sit tasks to volitional failure, one before and one after the completion of a cognitive task. Half the participants were randomly assigned to complete a high cognitive demand task to induce mental fatigue (incongruent Stroop; HMF), while the other half performed a low cognitive demand task (documentary viewing; LMF) before the second wall sit. Immediately prior to the second wall sit, half the participants in each cognitive task group also received instructions to focus their attention either internally (INT) or externally (EXT) during the second wall sit. The main effect of mental fatigue (p < .001, d = .873) during the cognitive task and the main effect of attentional focus (p < .001, d = .883) during the wall sit task were significant, indicating effective manipulations. Results found no moderating effect of attentional focus on wall sit performance (p >.500) or RPE (p = .724). However, between-group analyses were conducted to probe the differences in performance between each group. Results indicated the HMF/INT group performed significantly worse than the LMF/EXT (p = .032) and trended towards performing worse than the HMF/EXT and LMF/INT groups (ps < .090). Significant differences in RPE were also seen between trials for the HMF/INT group (p = .009, d = .592) alone, suggesting detrimental effects of both mental fatigue and internal focus combined. Overall, the data indicate a potential moderating effect of internal attentional focus that may exacerbate the detrimental effects of mental fatigue on performance and RPE.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Origins and Heterogeneity of Shyness: A Developmental, Biological Perspective

contributor:
Schmidt, Louis A.
Psychology

subject: Temperament Shyness Children Biology Development

abstract: Temperamental shyness is a trait characterized by fear and avoidance in response to situations of social novelty and/or perceived social-evaluation. Although there has been an abundance of research examining the psychosocial correlates of childhood shyness, we know considerably less about the developmental and biological origins of shyness and its subtypes. Chapters 2 to 5 of this dissertation include empirical studies that examine the developmental and biological foundations of temperamental shyness in general, and Chapter 6 examines subtypes of shyness in particular. In Chapter 2, I found that individuals who were born extremely premature and also exposed to exogenous corticosteroids prenatally displayed a stable trajectory of high shyness from childhood to adulthood, possibly due to the programming of threat sensitivity. In Chapter 3, I found that children who had greater relative right frontal brain activity at rest (a neural correlate of fear and avoidance) demonstrated increases in shyness across the early school age years. In Chapters 4 and 5, I examined patterns of autonomic physiology among shy children during two types of social threat processing. I demonstrated that shy children show stability in autonomic arousal while viewing socio-affective threat from age 6 to 7.5 years (Chapter 4), and that shy children show arousal and excessive regulation on autonomic and affective levels during the anticipation of socio-evaluative threat (Chapter 5). Finally, Chapter 6 reports that the developmental onset of shyness is associated with distinct behavioral and biological correlates in shy children. Children with early-developing shyness showed greater relative right frontal brain activity at rest, while children with later-developing shyness showed greater salivary cortisol production to a socio-evaluative task. Collectively, the studies and findings from this dissertation highlight that shyness is related to distinct developmental and biological processes associated with avoidance and threat processing, which may underlie fear in novel social contexts.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)

abstract: Shyness is a trait that is characterized by fear and nervousness during new social situations or in situations of perceived social evaluation. Although there has been an abundance of research examining the psychosocial correlates of childhood shyness, we know considerably less about the developmental and biological origins of shyness. In this dissertation, I examined individual differences in the biology, developmental onset, and developmental trajectory of shyness. This work illustrated that shyness is a heterogenous phenomenon, with individual differences in the developmental onset and developmental course. As well, this work provided evidence that shy children tend to be more sensitive to perceiving threat in social situations, and their brain and body may be “primed” to overreact when they are faced with this perceived social threat. Shy children may have a biological profile associated with avoidance and threat processing, which may be one factor underling their fear in new social contexts.


title: Contributions to Mean-Cluster Modeling of Structured Materials - Applications to Lithium-Ion Batteries

contributor:
Protas, Bartosz
Computational Engineering and Science

subject:
Li-ion Battery
Inverse Modeling
Cluster Approximation Modeling
Moment Closure Approximation

abstract:
One of the questions arising as regards to structured materials is how one can compute
their cluster concentrations. Specifically, we are interested in deriving the concentrations of the micro-structures in the NMC (Nickel-Manganese-Cobalt) layer of the cathodes of Li-ion batteries. A simulated annealing approach has been used lately for detecting the structure of the whole lattice which is computationally heavy. Here we propose
a mathematical model, called cluster approximation model, in the form of a dynamical
system for describing the concentrations of different clusters inside the lattice. However, the dynamical system is hierarchical which requires to be truncated. Truncation
of the hierarchical system is performed by the nearest-neighbor closure scheme. Also,
a novel framework is proposed for an optimal closure of the dynamical system in order
to enhance the accuracy of the model. The parameters of the model are reconstructed
by the least square approach as a constrained optimization problem by minimizing the
mismatch between the experimental data and the model outputs. The model is validated
based on the experimental data on a known Li-ion battery cathode and different approximation schemes are compared. The results clearly show that the proposed approach
significantly outperforms the conventional method.

abstract: Thesis

abstract: Master of Science (MSc)


title: EXERCISE ADHERENCE POST TOTAL KNEE ARTHROPLASTY

contributor:
Macedo, Luciana
Rehabilitation Science

subject:
Total knee arthroplasty
Exercise adherence

abstract:
Total knee arthroplasty (TKA) places a large burden on the Canadian Health care system with over 700 million dollars spent on this procedure annually. Exercise has been shown to be effective in improving pain, physical function, mobility and quality of life post-operatively. There is very limited research on adherence to rehabilitation and exercise after TKA. The aim of this thesis was to increase understanding of exercise adherence in this population.
The first manuscript in this thesis was a scoping review that evaluated exercise adherence and the quality of reporting of exercise interventions within post-operative TKA rehabilitation trials. A systematic search of scientific databases was conducted for randomized controlled trials (RCT) with an exercise intervention for post-operative TKA. In total, 112 articles were included in this review. This study found that the vast majority of articles (85%) were of poor quality having either high/unclear risk of bias. The majority of RCTs (63%, N=71) on post-operative TKA rehabilitation did not adequately report exercise adherence (e.g., definition, outcome measure used and results), while only 23% (N=15) provided a definition of adherence in the context of their study. Overall reporting of the exercise intervention was poor, with 15 items (of 19) of the Consensus on Exercise Reporting Template (CERT) reported less than 60% of the time. Inadequate reporting of exercise interventions and adherence to exercises leads to decreased reproducibility and translation into clinical practice. Proper reporting of rehabilitation exercises after TKA will ensure standardization for future studies and clinical replication.
The second manuscript in this thesis was a qualitative study that aimed to understand the patient- related barriers and facilitators to exercise adherence in patients immediately after undergoing TKA. Using an interpretive description approach, semi-structured qualitative interviews were conducted. Seven participants were interviewed at 8-weeks post-operatively in order to better capture physical, psychological, social and contextual factors linked to exercise adherence. Interview questions explored participants’ experience with physical activity and exercise, motivation to perform physical activity, beliefs that exercise will reduce pain, the factors that limit their ability to engage in exercise, and the importance of using self-regulation to improve exercise adherence. Emergent themes were mapped onto the domains of the WHO adherence framework. This study identified 4 themes that fit within the WHO adherence framework: patient-related factors, condition-related factors, health care system, and social support. In particular, self-regulation, previous knowledge of exercise, post-operative complications, comorbidities, social support, and lack of guidance from health care providers were identified as personal and environmental characteristics that affect exercise adherence. The overall findings of this study suggest exercise adherence is a multifaceted construct with interconnected concepts.

abstract: Thesis

abstract: Master of Health Sciences (MSc)

abstract:
Total knee replacement (TKR) surgery costs the Canadian Health care system millions of dollars per year. Exercise is an effective method for improving function and decreasing pain after surgery. However, it is unclear how much patients perform exercise as recommended by health care providers. The purpose of this study was to understand exercise behaviour after knee surgery.
The first study was a scoping review that looked at exercise adherence and the characteristics of exercise treatments delivered after knee surgery in previously published clinical trials. The study found that most studies did not report enough information for replication of exercise treatment protocols (e.g. description of provided exercises/progression, who implemented the intervention, etc.). Similarly, exercise adherence was also poorly reported (e.g., definition, how adherence was measured). Poor reporting of exercise treatment methods, and how well participants complete exercises decreases the ability of researchers and therapists to apply the results of these trials.
In the second study, patients were interviewed after knee surgery to understand why patients do or do not exercise after surgery. There were several factors, both positive and negative, that patients identified that affected their ability to exercise (e.g. self-regulation (referring to the ability to control thoughts, emotions and behaviour to pursue long-term goals), prior knowledge of exercise, having social support from family and friends, as well as lack of support from health care providers). The overall findings suggest that how well participants exercise after surgery is a complex issue. In order to improve exercise adherence, we need to have a better understanding of the individual factors that may influence adherence.


title: A Subsidy Policy to Ensuring Risk-Equity in Railroad Hazmat Transportation Network: A Risk Mitigation Strategy

contributor:
Verma, Manish
Computational Engineering and Science

subject:
railroad hazmat transportation
risk mitigation
bi-level programming

abstract:
Railroad is one of the primary modes for transporting hazardous materials (hazmat).
Given the dangerous nature of the hazmat, risk mitigation in the railroad transportation is the need of the hour. Hence, we explore the idea of equitable distribution
of risk in the railroad network. We propose the subsidy policy to be considered by
government to induce favourable routings of the hazmat shipments. The government's objective is to achieve risk equity in the network, whereas, the carrier's cost
effective approach leads to increased risk in low-cost service-legs. To model this, we
formulate the problem as a bi-level mixed integer program. We derive the single level
mixed integer linear program (MILP) and test it on the rail infrastructure in midwest
United States using state-of-the-art solver CPLEX 12.8.0. The instances with upto
25 shipments on the network are solved efficiently on a local machine. We use high
performance computing resource available at Graham cluster of Compute Canada
facility to solve the large instances with 50 shipments on the network. We show the
effectiveness of the subsidy policy as a risk mitigation tool for the railroad hazmat
transportation, and review the efficiency of the solution methodology to solve the
MILP for the network. Moreover, the results demonstrate the economic feasibility for
the government to allocate the budget for the subsidy.

abstract: Thesis

abstract: Master of Science (MSc)


title: High-Speed Dry Milling of IN718 with Advanced Ceramic Tools: A Machinability Study

contributor:
Veldhuis, Stephen
Mechanical Engineering

abstract: Inconel 718 (IN718) is a widely-used nickel-based superalloy in the aerospace industry, which is known for its superior mechanical properties and microstructural reliability at elevated temperatures. However, the poor machinability of this heat resistant alloy has always been a challenge for the manufacturing industry. The high shear strength, low thermal conductivity and intensive work hardening properties of IN718 induce high thermo-mechanical stresses on the tool’s cutting edge which leads to rapid tool wear even at extremely low cutting speeds. Hence, limited scientific data is available around high-speed machining of IN718, especially on more demanding applications such as interrupted cutting during milling. This research is focused on IN718 machinability studies at extreme conditions, using a dry high-speed face milling process with exotic tool materials like advanced SiAlON ceramics. Comprehensive material characterization techniques and machinability studies have been performed using tool wear studies, micro and nanomechanical indentations, optical 3D imaging, SEM/EDS studies and finite element modelling to identify the dominant tool wear mechanisms over a wide range of cutting parameters. Also, further investigations have been done on the mechanisms of chip formation, shear deformation at extreme conditions and tribological aspects of tool-chip-workpiece interactions such as the formation of built-up layers and tribofilms. Results suggest that there is a narrow operational window (around 1000 m/min cutting speed) in which high-speed machining of IN718 superalloy can be performed using a carefully selected ceramic tool material. Experimental results under this cutting speed show a drastic transformation in the machinability of inconel 718 when surpassing a high level of temperature and strain rate. Following further surface integrity studies on the machined workpiece, it can be concluded that such a process is suitable for rough or semi-finishing of IN718 parts at a four times higher material removal rate as compared with conventional practices currently used in industry.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Recent studies on the machining of advanced industrial components show that improving the process productivity by increasing the material removal rate has the most significant contribution to reducing the cost of manufacturing. Hence, high-speed machining has been an important topic for researchers in academia and industry for the past few decades. Recent advancements in the mechanical properties of exotic tool materials like structural ceramics have remarkably contributed to the successful implementation of high-speed machining concepts for difficult-to-cut alloys. The present research attempts to investigate and understand the prevailing phenomena governing the machinability of inconel 718 in a high-performance dry milling process using advanced SiAlON ceramic tools.


title: Measurement properties of generic preference-based measures in individuals with chronic obstructive pulmonary disease

contributor:
Kuspinar, Ayse
Rehabilitation Science

abstract: Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Luckily, many interventions are available for patients with COPD to improve their symptoms and exercise tolerance, and reduce exacerbation events. Generic preference-based measures are measures of health-related quality of life that can be used for cost-utility analysis. However, before these measures can be used to make healthcare decisions, their psychometric properties (i.e., reliability, validity, responsiveness) have to be assessed. The aim of this thesis was to evaluate the psychometric properties of generic preference-based measures in people with COPD. First, a systematic review was conducted to evaluate the existing evidence on the psychometric properties of these measures in people with COPD. Then, a content validation study was conducted to examine whether these measures accurately reflect the areas of life important to people with COPD. Findings from these two studies showed that generic preference-based measures were not sensitive or fully reflective of patients’ health concerns. Findings highlighted the need for properly designed studies (e.g., using correct methodology) when evaluating the psychometric properties of generic preference-based measures in COPD. In addition, our results suggest the need for development of a COPD-specific preference-based measure to improve the sensitivity of cost-utility analyses in this population. This in turn would enable the health-related quality of life of individuals with COPD to be accurately captured when making healthcare decisions.

abstract: Thesis

abstract: Master of Science Rehabilitation Science (MSc)

abstract: Chronic obstructive pulmonary disease is a disabling lung disease that affects many Canadians, and policymakers require tools to help them decide how to best use limited healthcare resources to help patients. Such tools are called generic preference-based measures and they help tell us how effective a treatment is based on quality of life and cost. However, before these tools can be used to make healthcare decisions, they have to be valid in the target population. Therefore, we conducted a review of studies evaluating the reliability and validity of these measures in people with chronic obstructive pulmonary disease. We also checked whether these tools accurately reflected the areas of life important to this population. Our findings showed that generic preference-based measures were not sensitive to the quality of life of patients with chronic obstructive pulmonary disease, and that there is a need for the development of condition-specific tools.


title: Post-Secondary Reading Development and Print Exposure in L1 and L2 Speakers of English

subject:
literacy
reading
year of study
bilingualism
print exposure
education
psychometrics
psycholinguistics
linguistics
psychology

abstract: In this thesis, two studies are presented which examine reading development and proficiency in post-secondary education. The first study examines the utility of a common method for determining print exposure, the Author Recognition Test (ART), in populations less frequently examined—namely, college students (as opposed to university students), and individuals whose first language is not English. Item Response Theory analysis shows that ART is not informative for these populations, which suggests that the development of a novel test of print exposure for comparing different populations is necessary. The second study quantifies the impact of each year of post-secondary study on reading development, and the differential effects between native (L1) and non-native (L2) speakers of English. Findings show that each year of study itself is not a significant predictor of change, but rather improvement is explained by advancement in component skills of reading which develop over the course of the degree.  Additionally, contrary to previous studies indicative of the Matthew Effect in college literacy development—which suggest that students improve by the end of their degree as a function of their ability at the beginning—this study demonstrates that L2 students generally benefit more from post-secondary education when compared to L1 peers, who start with a significant advantage.  In this way, L2 students with sufficient mastery of component skills of reading emerge from post-secondary education with skills comparable to those of native English-speaking colleagues.

abstract: Thesis

abstract: Master of Science (MSc)


title: Deep Neural Networks for Improved Terminal Voltage and State-of-Charge Estimation of Lithium-Ion Batteries for Traction Applications

contributor:
Emadi, Ali
Mechanical Engineering

subject:
Deep neural networks
Artificial Intelligence
Li-ion
State-of-Charge estimation
Electric Vehicles
Battery Management Systems
Recurrent Neural Networks
Battery Model

abstract:
The growing interest in more electrified vehicles has been pushing the industry and academia to pursue new and more accurate ways to estimate the xEV batteries State-of-Charge (SOC). The battery system still represents one of the many technical barriers that need to be eliminated or reduced to enable the proliferation of more xEV in the market, which in turn can help reduce CO2 emissions. Battery modelling and SOC estimation of Lithium-ion batteries (Li-ion) at a wide temperature range, including negative temperatures, has been a challenge for many engineers.
	For SOC estimation, several models configurations and approaches were developed and tested as results of this work, including different non-recurrent neural networks, such as Feedforward deep neural networks (FNN) and recurrent neural networks based on long short-term memory recurrent neural networks (LSTM-RNN). The approaches have considerably improved the accuracy presented in the previous state-of-the-art. They have expanded the application throughout five different Li-ion at a wide temperature range, achieving error as low as 0.66% Root Mean Square Error at -10⁰C using an FNN approach and 0.90% using LSTM-RNN. Therefore, the use of deep neural networks developed in this work can increase the potential for xEV application, especially where accuracy at negative temperatures is essential.
	For Li-ion modelling, a cell model using LSTM-RNN (LSTM-VM) was developed for the first time to estimate the battery cell terminal voltage and is compared against a gated recurrent unit (GRU-VM) approach and a Third-order Equivalent Circuit Model based on Thevenin theorem (ECM). The models were extensively compared for different Li-ion at a wide range of temperature conditions. The LSTM-VM has shown to be more accurate than the two other benchmarks, where could achieve 43 (mV) Root Mean Square Error at -20⁰C, a third when compared to the same situation using ECM. Although the difference between LSTM-VM and GRU-VM is not that steep.
	Finally, throughout the work, several methods to improve robustness, accuracy and training time have been introduced, including Transfer Learning applied to the development of SOC estimation models, showing great potential to reduce the amount of data necessary to train LSTM-RNN  as well as improve its accuracy.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
For electric vehicle State-of-Charge estimation, several models configurations and approaches were developed and tested as results of this work, including different non-recurrent neural networks, such as Feedforward deep neural networks (FNN) and recurrent neural networks based on long short-term memory recurrent neural networks (LSTM-RNN). The approaches have considerably improved the accuracy presented in the previous state-of-the-art. They have expanded the application throughout five different Li-ion at a wide temperature range, achieving error as low as 0.66% Root Mean Square Error at -10⁰C using an FNN approach and 0.90% using LSTM-RNN. Therefore, the use of deep neural networks developed in this work can increase the potential for xEV application, especially where accuracy at negative temperatures is essential.
	For Li-ion modelling, a cell model using LSTM-RNN (LSTM-VM) was developed for the first time to estimate the battery cell terminal voltage and is compared against a gated recurrent unit (GRU-VM) approach and a Third-order Equivalent Circuit Model based on Thevenin theorem (ECM). The models were extensively compared for different Li-ion at a wide range of temperature conditions. The LSTM-VM has shown to be more accurate than the two other benchmarks, where could achieve 43 (mV) Root Mean Square Error at -20⁰C, a third when compared to the same situation using ECM. Although the difference between LSTM-VM and GRU-VM is not that steep.


title: Direct force measurement of microscopic droplets pulled along soft surfaces

contributor:
Dalnoki-Veress, Kari
Physics and Astronomy

subject:
Soft Matter
Polymers
Fluid Dynamics

abstract: When a droplet is placed on a soft material, surface tension forces from the droplet are able to deform the substrate. This thesis explores the effect of substrate stiffness on energy dissipation as a droplet is slid along a soft material. We find behaviour is characterised by two regimes separated by the lengthscale of the deformation in the substrate. For films approximately the lengthscale of the deformation, dissipation increases with thickness. As the thickness becomes much larger than the size of deformation, there is a plateau in dissipation. This result agrees with the model we use to understand energy dissipation in these systems.

abstract: Thesis

abstract: Master of Science (MSc)


title: Social Policy at the Edge of Knowable: Towards a Unified View of Evolutionary Change in Policy Systems

subject:
policy change
evolutionary policy
complexity policy
complex systems
TRIZ
social policy

abstract:
In the world of growing diversity, interdependence, and rapid change, making sense of
policy evolution, especially in analytical settings, is increasingly challenging, not the
least due to the flaws of conventional assumptions or the limits to the availability of
evidence. As we consider an alternative worldview embracing the complex and adaptive
nature of social reality, we recognize there are further boundaries to what can be known
and done about the outcomes in social systems. Yet, this foundation also promises to
broaden our horizons with new tools for understanding, comparing, and developing
public policy. Inspired by innovation research, this work makes the case for bringing a set
of such tools into public policy studies and situates them in an essential theoretical
context. Further, through an analysis of social and labour market policy development
across two jurisdictions—while reaching to flexicurity as a model and reference—it
demonstrates the application of the new approach to the study of welfare state
modernization and to policy scholarship more generally.

abstract: Dissertation

abstract: Candidate in Philosophy


title: Harnessing evidence and values in health policy implementation

abstract: The importance of harnessing research evidence (hereafter evidence) and public values (hereafter values) in health policy implementation (hereafter policy implementation) is widely recognized. Evidence helps policy implementers to find answers to implementation-related questions (e.g., How to address barriers to implementation that may exist at citizen, provider and system levels? What are the most cost-effective interventions?). A culturally sensitive implementation approach that considers values can minimize resistance from the public to policy implementation and contribute to achieving implementation goals. Hence, there is a global push to harness evidence and values in policy implementation. Despite the importance of harnessing evidence and values, little work has been undertaken to understand how the concepts of evidence and values are perceived in the context of policy implementation and how different factors affect the harnessing of evidence and values. This thesis addresses these knowledge gaps through three manuscripts that use a range of methods and approaches to 1) clarify the concepts of harnessing evidence and values in the context of policy implementation; 2) develop a framework that explains how different factors affect policy implementers’ decision to harness evidence and values; 3) apply the framework in the context of public health policy implementation and adjust as needed; and 4) elicit public health leaders’ perspectives about key strategies that can support harnessing evidence and values. These chapters together make substantive, theoretical and methodological contributions to the field of health policy implementation research, and in particular, to the efforts to strengthen support for harnessing evidence and values in health policy implementation.

abstract: Thesis

abstract: Candidate in Philosophy


title: Nurse-Family Partnership Supervisor Roles and Responsibilities for Implementation of an Intimate Partner Violence Intervention:  An Interpretive Description Study

contributor:
Jack, Susan
Nursing

subject:
Supervision
Home Visitation
Nurse-Family Partnership
Implementation
Intimate Partner Violence
Intervention

abstract: The Nurse-Family Partnership (NFP) is an evidence-based public health initiative targeted to young, pregnant, first-time mothers impacted by social and economic disadvantage.  This study is part of an embedded qualitative process evaluation from a larger cluster RCT trial.  The purpose of this study was to understand NFP supervisor roles, responsibilities, and experiences associated with the uptake of a new IPV intervention by nurse home visitor into existing NFP practice.

abstract: The Nurse-Family Partnership® (NFP) is a home visitation program for young pregnant and first-time mothers affected by social and economic disadvantage.  In response to intimate partner violence (IPV) experienced by women and children involved in the program, a nursing intervention was developed to support nurse home visitors identify and respond to IPV.  Within each participating NFP team, supervisors were accountable for facilitating the implementation process of the IPV intervention for uptake into nurse home visitor practice.  To understand the functions of NFP supervisors involved with the facilitation of the implementation process for the IPV intervention, an interpretive description approach was utilized involving primary data collection from interviews with 11 supervisors and 2 managers, and triangulated with secondary data from 7 focus groups (n=35 nurses).  From this analysis, an NFP supervision framework was developed that included 4 domains, 7 roles, 3 sub-roles and multiple responsibilities.  Supervision was found to involve roles and sub-roles functioning in oversight of implementation and others that functioned in the direct implementation of the IPV intervention, forming levels of supervision, and creating a hierarchy.  A comprehensive appreciation of NFP supervisor domains, roles, sub-roles and responsibilities enacted during the implementation process is important to help identify the best alignment of human resources, recognize how the NFP can best support supervisors, and to champion achievement of current and future innovation implementation goals.  Recommendations of support for supervisors include facilitating educational opportunities, creating transparency of the implementation process, developing a quality improvement strategy, providing supervisor mentorship, improving standardization, and recognizing the competing NFP priorities for supervisors and nurse home visitors.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: The Nurse-Family Partnership® (NFP) is a home visitation program targeted to young mothers, pregnant with their first child.  To support nurse home visitors identify and respond to intimate partner violence (IPV) experienced by NFP mothers and children, an IPV intervention was developed.  Within the NFP implementing agencies, supervisors were instrumental in ensuring the IPV intervention was delivered as intended, forming what is known as the implementation process.  This qualitative interpretive descriptive study involved interviews with 11 supervisors and 2 managers, as well as a secondary analysis of 7 focus groups (n=35 nurses) to understand and describe the roles and responsibilities supervisors had within this process.  From the analysis of these data, an NFP supervision framework was developed that included articulation of 4 domains, 7 roles, 7 sub-roles and multiple responsibilities affiliated with this position.  This framework offers a new language for supervision which may become a first step to better understanding, communicating, and developing supervision in home visitation, and in particular, articulating the functions supervisors are required to lead when faced with the responsibility for implementing a new innovation within their program.  It is important to understand NFP supervisor functions of the implementation process to enable NFP strategies that will best support supervisors, ensure responsibilities belong to the right person, and meet implementation goals when adopting evidence into NFP nurse home visiting practice.


title: Hydrogen & Deuterium Detection in Zr-2.5%Nb by Laser Induced Breakdown Spectroscopy

contributor:
Novog, David
Preston, John
Engineering Physics

subject:
LIBS
Spectroscopy
Laser
Hydrogen detection
Laser Induced Breakdown Spectroscopy

abstract:
The detection of trace amounts of H and D present in Zr-2.5%Nb in the form of ZrH and ZrD, respectively, by LIBS was explored. The intended use case for this experimentation was CANada Deuterium Uranium (CANDU) nuclear reactor pressure

tube inspections where hydride buildup can lessen the mechanical strength of these
components. As these tubes carry coolant and house the fuel bundles, their integrity
is paramount. A LIBS inspection method is of interest in the nuclear industry due
to the operational flexibility it would introduce and its ability to reduce the cost,
time, and radiation dose associated with inspection campaigns of pressure tubes in CANDU nuclear reactors.
Using LIBS, simultaneous detection of H and D was achieved in a low-pressure air environment using a microjoule, picosecond pulsed laser and emission being captured by a high-resolution spectrometer. The emission lines of the two species were blended, however, two peaks can be seen. Experiments using a milijoule, nanosecond pulsed laser in a LIBS setup were also conducted at atmospheric pressures. These experiments failed to show D emission, however.

In addition to detecting emission from H and D, a Monte Carlo algorithm was developed for estimating the error associated with a LIBS inspection of a pressure tube segment. ZrH and ZrD form heterogeneous structures in the bulk of the Zr-2.5%Nb pressure tube material, meaning that a single measurement would not be indicative of the entire tube. Using metallographs of artificially hydrided pressure tube samples, the error within a given confidence interval was found as a function of number of measurement sites and ablation diameter.
Furthermore, the impacts to Zr-2.5%Nb based on intense laser-matter interactions
was investigated by optical microscopy and interferometry, allowing for 3-dimensional
reconstructions of ablation craters. The morphology of millijoule, nanosecond pulsed laser-matter interaction and microjoule, picosecond pulsed laser-matter interaction were the subjects of this investigation. The salient difference between the two interactions is the evidence of substantial melting and subsequent re-deposition of material in the case of nanosecond interactions, whereas picosecond ablation yielded little melting.
These results support the further development of a LIBS-based inspection method
for determining the concentration of H and D in Zr-2.5%Nb. It was found that a
vacuum environment allows for the simultaneous detection of H and D emission.
Further experimentation should explore using low-pressure buffer gas environments
as a method to further distinguish emission between the two species.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Examining and Contextualizing Approaches to Establish Policy Support Organizations

contributor:
Wilson, Michael G
Health Policy

subject:
Policy support organization
Knowledge translation
Evidence-informed policymaking

abstract:
There have been an increasing number of calls emphasizing the need to use the best-available research evidence to inform health system policies and, in response, efforts have been made in many countries to develop and implement policy-support organizations (PSOs) to enhance the use of research in policymaking. However, there is a paucity of evidence regarding both the best approaches for the successful establishment of such organizations. Moreover, there are very few attempts to consider how approaches can be applied in particular contexts, and operationalized by policymakers and stakeholders in their efforts to support EIPM through the establishment of PSOs.
This dissertation incorporates a mix of methodological approaches to address this gap. First, in chapter two, a critical interpretive synthesis was used to develop a conceptual framework that can guide the process of establishing a PSO or similar entities.  The framework outlines the stages in the process of establishing a policy support organization and the contextual factors at the political-, research- and health-system level that influence this process. Second, in chapter three, the framework from the CIS was used to inform the design of a survey tool and interview guide used in a sequential mixed methods study to enrich the framework  by soliciting insights from those with practical experience with  developing and operationalizing PSOs in real-world contexts. Specifically, this study provides insights into the approaches and strategies for each stage in the establishment process for a PSO. Lastly, in chapter four, the findings from chapter two and three were used -- along with in-depth one-on-one semi-structured interviews with policymakers, researchers and stakeholders who are familiar with the Omani system -- to develop a model for an Omani knowledge translation department, which can be used in a future co-design process for activating the department.
The dissertation chapters build on each other and make substantive, methodological, and theoretical contributions. Substantively this dissertation clarifies and defines key concepts that are essential to enable a rich understanding of the process of establishing a PSO. It highlights that the process of establishing such an organization is iterative and can be influenced by multiple contextual factors that affect the individual approach that has been used to support evidence-informed policymaking. Methodologically, this dissertation is the first study of PSOs that uses a mix of conceptual framework generation, insights from a wide range of fields such as organizational development, and empirical approaches that adopt mixed methods to derive fulsome answers to specific questions about establishing PSOs. Theoretically, this dissertation provides a conceptual framework that can be used to inform the process of establishing a PSO in different contexts. The theoretical constructs of this framework were verified and strengthened through direct application in subsequent studies in the dissertation.
This dissertation has many implications for policy and research. Most importantly, for those interested in establishing a PSO, my findings provide a road map for identifying the most appropriate starting point and the factors that might influence the establishment process. In addition, leaders of existing PSOs can use my findings to expand or refine their scope of work. Given that this framework focuses only on PSOs in the health sector, an important next step for research will be to include other sectors and identify any additional insight that can enhance the framework I have developed.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Health system policymaking is a challenging task because many factors need to be balanced in policy decisions (e.g., efficiency, equity, and politics). There have been an increasing number of calls emphasizing the need to use the best-available research evidence to inform health system policies and, in response, efforts have been made in many countries to develop and implement approaches to enhance the use of research in the policymaking process. In some instances, organizations have been given sole responsibility for supporting evidence-informed policy, but evidence is limited to inform the process of establishing these organizations. This dissertation addresses this gap in the literature by: I) developing a new conceptual framework for the process of establishing organizations that can support evidence-informed policymaking; ii) identifying approaches that can be used in this process; and iii) developing a model for a proposed Omani knowledge translation department using this framework.


title: INVERSE MODELING BASED ON MRI MEASUREMENTS TO COMPARE CAHN-HILLIARD MODELS USING MULTIPHASE POROUS ELECTRODE THEORY

title: INVERSE MODELING OF LI TRANSPORT IN MULTIPHASE ELECTRODES

subject:
Inverse Modeling
Li-ion Battery
Thermodynamics
Fluid Mechanics
Electricity & Magnetism
Physics
Applied Mathematics
Computation
Cahn-Hilliard
Phase-Separation

abstract: In this study, a computational approach to the solution of an inverse modeling problem is developed to reconstruct unknown material properties of a Li-ion battery.  In-situ MRI measurements performed on a layered graphite electrode during charging are used in comparison with Stefan-Maxwell concentrated electrolyte theory, Butler-Volmer reaction kinetics, and multiphase porous electrode theory to explore the overall accuracy of models for Li transport processes in the active material.  In particular, the main research goal here is to determine if the original Cahn-Hilliard formulation for phase-separation can be improved upon through extension to a periodic bilayer model (two-layer Cahn-Hilliard).  The original model contains a pair of two stable phases at low and high concentrations that produces the ``shrinking core'' behavior for lithiated graphite.  The comparative advantage of the periodic bilayer model stems from the capturing of a third stable phase of intermediate concentration as the average between one concentrated layer and one dilute layer.  Calibration is done simultaneously on concentration and cell voltage profiles through multi-objective optimization where the accuracy of a model is assessed based on the quantification of agreement with experimental data.  The periodic bilayer model is found to improve upon the least-squares error for fitting of concentration profiles by roughly 20%, while the voltage fittings are too similar to be conclusive.

abstract: Thesis

abstract: Master of Science (MSc)


title: An experimental and modeling study of carbon nanomaterial membranes, bacterial growth, and their interactions towards Pb(II) removal from wastewater

contributor:
de Lannoy, Charles
Kim, Younggy
Chemical Engineering

subject: Lead, Carbon Nanotubes, Carbon Nanofibers, Membranes, Bioreduction, Bacteria, Fouling, Thin Film Composites

abstract:
Pb(II) removal is imperative due to its inherent toxicity at low levels and its tendency to accumulate in ecosystems. Conductive carbonaceous nanomaterials (CCNs), such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs), have recently gained the interest of researchers due to their superior properties and ease of functionalization. The aim of this study is to utilize CCNs for Pb(II) removal within membrane technology and bioremediation strategies.
Membranes have shown promise in their treatment abilities, producing excellent effluent quality while reducing plant footprints. The integration of CNTs within membrane technology provides an opportunity to couple its removal capacity with Pb(II) removal that exhibits regeneration capabilities. However, membrane fouling can be problematic for membrane longevity and regeneration. CNTs have also shown to be capable of mitigating fouling via electrostatic repulsion and pollutant degradation. However, little work has been conducted on its fabrication. In this work, CNTs were incorporated with poly(vinyl) alcohol (PVA) in thin film composites, where the effects of PVA chain length and degree of crosslinking were investigated. It was found that a pseudo-optimal coating can be obtained using 31-50kDa PVA with 10% crosslinking. This combination lead to a highly permeable, hydrophilic surface with good electrical conductivity that exhibited a molecular weight cut off of 2000kDa.
Biosorption has shown promise in Pb(II) removal in the lab scale but its large-scale use is hindered from rapid saturation of binding sites and low regeneration abilities. Exoelectrogens were proposed as reactive biosorbents to couple biosorption with bioreduction in an attached growth configuration. CCNs were investigated as bacterial scaffolds, where their efficacy and Pb(II) dosage concentration was studied. It was found that CNFs were superior in removing Pb(II), exhibiting Pb(II) concentrations ≤0.10 ppm where removal increased when Pb(II) dosage increased from 0.5 to 5ppm. SEM-EDX analysis provided evidence that bioreduction dominated Pb(II) removal. A long-term study was further conducted using CNFs, revealing its robustness in long term removal over suspended growth reactors with a sustained removal of ≈ 80%. A numerical model was further proposed which exhibited a goodness of fit with an R-squared of 0.92. This model confirmed that bioreduction dominated Pb(II) removal and revealed biofilm thickness and Monod kinetics to be the main influential parameters on Pb(II) removal.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: The Application of Focused Ion Beam Technology to the Modification and Fabrication of Photonic and Semiconductor Elements

contributor:
Knights, Andrew
Bassim, Nabil
Engineering Physics

subject:
Focused Ion Beam
Photonics
Semiconductor Fabrication
Radiative Heat Transfer

abstract:
Focused Ion Beam (FIB) technology is a versatile tool that can be applied in many fields to great effect, including semiconductor device prototyping, Transmission Electron Microscopy (TEM) sample preparation, and nanoscale tomography. Developments in FIB technology, including the availability of alternative ion sources and improvements in automation capacity, make FIB an increasingly attractive option for many tasks. In this thesis, FIB systems are applied to photonic device fabrication and modification, semiconductor reverse engineering, and the production of structures for the study of nanoscale radiative heat transfer.
Optical facets on silicon nitride waveguides were produced with plasma FIB (PFIB) and showed an improvement of 3 ± 0.9 dB over reactive ion etched (RIE) facets. This process was then automated and is capable of producing a facet every 30 seconds with minimal oversight. PFIB was then employed to develop a method for achieving local backside circuit access for circuit editing, creating local trenches with flat bases of 200 x 200 μm. Gas assisted etching using xenon difluoride was then used in order to accelerate the etch process. Finally, several varieties of nanogap structure were fabricated on devices capable of sustaining temperature gradients, achieving a minimum gap size with PFIB of 60 nm.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Sex determination in frogs offer insights into how important things evolve

title: Evolution of sex determination in Pipid frogs

contributor:
Evans, Ben
Biology

abstract: Developmental system drift refers to situations where, in different species, similar traits are controlled by diverged genetic systems. For example, sexual differentiation is crucial for reproduction and survival of species, but is controlled by rapidly evolving genes and genetic interactions. In my PhD thesis, I studied the evolution of triggers for sex determination in order to better understand how developmental systems drift occurs. The second chapter examines the diversity of sex determining systems in the frog family Pipidae (which includes the genus Xenopus). My work provides evidence for seven distinct sex determination systems in this group of frogs. This work also shows that a known trigger for sex determination (dm-w) has not always been efficient in driving female development of frogs that carry this gene. I propose that the inefficiency of a trigger for sex determination might play a major role in the fate of sex chromosomes. In the third chapter, I explore potential mechanisms by which dm-w and the supergene that contains dm-w evolved, and possible effects in its efficiency in driving female sexual differentiation. This work shows that the acquisition and evolution of the last exon of this gene might be associated with the onset of female-specificity. While the specific function of two other female-specific genes in X. laevis (scan-w, ccdc69-w) remains unclear, their origin seems to coincide with the empowerment of dm-w. We also found that an important domain in the function of dmrt1, another transcription factor that is related by gene duplication to dm-w, is often incapacitated by early stop codons. Taken together, this thesis documents dynamic functional evolution of individual components (dm-w, dmrt1, scan-w, ccdc69-w), entire genetic networks (sex chromosomes), and genomic contexts (recombination suppression) that govern an important phenotype (sex determination) in a diverse group of widely studied vertebrates (pipid frogs).

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: The Koch Snowflake RF Surface Coil: Exploring the Role of Fractal Geometries in 23Na-MRI

contributor:
Noseworthy, Michael
Biomedical Engineering

subject:
medical imaging
MRI
radiofrequency
coils
fractals
sodium

abstract:
Intra-cellular sodium (23Na) concentration is directly related to cellular health.  Thus, sodium magnetic resonance imaging (MRI) can provide metabolic information on tissue health that a routine clinical (proton) MRI cannot. 23Na-MRI could be a valuable tool to assist physicians in the diagnosis, prognosis, and monitoring of a variety of pathologies. However, due to factors that include quantum mechanical limitations and biological restrictions, the signal-to-noise ratio (SNR) of a sodium scan is much lower than that of a standard proton scan, which limits the practicality of 23Na-MRI in a clinical setting. This project looks to improve the viability of 23Na-MRI and focuses on an often overlooked facet of MRI development, the radio frequency (RF) coil.

Fractal antennas have been used in telecommunication systems for years, and are generally exploited for their compact nature, allowing for the same performance of a larger antenna, in a smaller space. They have also been shown to be capable of a wider transmission bandwidth (BW) than a standard antenna and with MRI applications they have been shown to provide a small SNR increase in proton imaging. It is hypothesized that a surface coil with a Koch snowflake fractal geometry can provide increased SNR for a sodium MRI scan, compared to that of a standard circular geometry coil, by producing a more homogeneous magnetic field in both space and frequency.

To test the hypothesis two coils, one circular and the other a Koch snowflake fractal, were simulated. The simulated magnetic fields were compared on their homogeneity and magnitude before the two coils were constructed and implemented with a variety of sodium MRI scans. B1+ maps were acquired to measure RF field homogeneity, and SNR was determined for both coil geometries. The coils were also tested for their homogeneity over varied transmit BWs by comparing images with various field of view (FOV) sizes. Finally the coils were compared for clinical viability in a test of healthy human knee imaging.

The circular coil had a more homogeneous B1+ field than the fractal at depths between 10-40mm, and had a higher SNR in its produced images. The circular coil acquired more signal in vivo which provided a higher detail image, but the fractal coil's SNR was higher due to reduced noise. The fractal coil performed better over a wider BW which indicates that further research should be conducted into the applications of fractal coils in multi-nuclear MRI scans.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Arterial Stiffness and Central Hemodynamic Response and Recovery in Individuals Post-Stroke

contributor:
Tang, Ada
Rehabilitation Science

subject:
Stroke
Arterial Stiffness
Hemodynamics
Exercise

abstract:
Background. Stroke affects over 80 million individuals worldwide. Elevated arterial stiffness has emerged as a novel independent risk marker for stroke. While arterial stiffness is improved after chronic aerobic training, a single bout of aerobic exercise leads to transient increases that typically resolve within 5 minutes of recovery. Elevated arterial stiffness may persist for up to 30 minutes following exercise in populations with cardiovascular disease. However, no study has examined the effect of acute aerobic exercise on arterial stiffness and central hemodynamics in individuals with stroke. Moreover, no study has explored the clinical significance of these responses.
Objectives. The primary objective of this thesis was to characterize the response and recovery of arterial stiffness and central hemodynamics to peak aerobic exercise in individuals ≥ 6 months post-stroke. The secondary objective was to explore the relationships between the exercise response and recovery of arterial stiffness and central hemodynamics, with cardiorespiratory fitness and walking ability.
Results. This cross-sectional study recruited 10 adults with stroke (mean ± SD age=56.9 ± 11.8; median [IQR]= 2.9 [1.9] years post-stroke; n=4 females). After peak aerobic exercise, cfPWV increased from rest and remained elevated for 20 minutes (p<0.05). Heart rate increased and remained elevated for 10 minutes post-exercise (p<0.05), while systolic blood pressure decreased and remained reduced for 15 minutes (p<0.05). Positive associations were found between cardiorespiratory fitness and heart rate reserve (r=0.74, p=0.02), and with each phase of heart rate recovery (HR60s r=0.80, p=0.005, HR120s r=0.79, p=0.006; HR300s r=0.72, p=0.02; and HR600s r=0.75, p=0.01). There were no relationships between response and recovery of hemodynamic variables with walking ability.
Conclusion. Individuals with chronic stroke may have impaired arterial stiffness and heart rate recovery following peak aerobic exercise. Moreover, heart rate reserve and all phases of heart rate recovery were related to cardiorespiratory fitness, but not walking ability.

abstract: Thesis

abstract: Master of Science Rehabilitation Science (MSc)

abstract: Arterial stiffness has been recently identified as an important risk marker for stroke. Aerobic exercise reduces the risk of stroke by lowering arterial stiffness. But during exercise, there is an increase in arterial stiffness that usually subsides by 5 minutes. Lengthy exposure to arterial stiffness can cause damage to organs like the kidneys and liver. The purpose of this thesis was to measure the arterial stiffness and cardiovascular response to exercise in people with stroke. We also studied the relationship between the responses, fitness and walking ability. Ten people with stroke participated in this study. After aerobic exercise, arterial stiffness stayed high above resting levels and did not recover after 20 minutes. Also, heart rate recovery was related to fitness but not walking ability. This study tells us that people with stroke have an weakened ability to recover from aerobic exercise and that higher fitness levels can improve exercise recovery.


title: Criteria for Numerical Stability of Explicit Time-Stepping Elastic-Viscoplasticity

contributor:
Stolle, D.F.E.
Civil Engineering

subject:
numerical stability
time-stepping
elastic-viscoplasticity

abstract:
A simple yet effective technique is used to obtain a numerical stability criteria for explicit time-marching algorithms in elastic-viscoplasticity. The resulting stability criteria are capable of accounting for non-associative and work hardening viscoplasticity for a wide variety of constitutive laws of the Perzyna-type. Conservative estimates for maximum permissible time step are obtained.
This thesis investigates the level of conservativeness by considering different problems exhibiting various levels of constraint. Using the proposed stability criterion, assuming a linear flow function, non-hardening and uniform material properties, it is shown that the initial strain algorithm for plasticity and the initial strain viscoplastic algorithms are numerically the same. The intuitive approach used to obtain an estimate of maximum permissible time step was also used to develop an unconditionally stable implicit time marching scheme which avoids expensive matrix inversions.

abstract: Thesis

abstract: Master of Engineering (ME)


title: The Effect of Fins on Vortex Shedding

contributor:
Ziada, Samir
Weaver, David
Engineering

subject:
fins
vortex shedding

abstract: An experimental study in air has been performed to determine what effect fins have on the flow over circular cylinders. The tubes under investigation included one bare tube and three segmented-finned tubes of different fin densities with the same root diameter as the bare tube. The tests were performed at two Reynolds numbers (2.61 x 104 and 4.98 x 104) and two downstream distances (2.5 & 5 diameters) and involved the use of hotwire anemometry. Measurements of mean and fluctuating velocities were taken across the wake as well as two-point fluctuating velocity correlations. It was discovered that the use of fins can result in significant differences. Fins cause larger mean velocity deficits in the wake profiles and significant shape differences in the total turbulence intensity profiles. Fins also increase the strength of vortex shedding, contrary to what would be expected, and increase the number of harmonic frequency peaks in the frequency spectra as three harmonic peaks were observed for the bare tube, while as many as ten were seen for the densest finned tube. Correlation length measurements, and thus radiated sound intensity, proved to be inconclusive. It was discovered that correlation length changed with angular rotation suggesting that this phenomenon needs to be investigated further before making any comparisons. Based on the differences seen with increased fin density, it is thought that there may be a critical fin density which causes fundamental changes in the cylinder wake. Also, during the course of this investigation, it was concluded that while the use of an effective diameter, De, proved adequate in collapsing the finned tube data, this approximation could be improved.

abstract: Thesis

abstract: Master of Applied Science (MASc)