Theses, Dissertations, and other Required Graduate Degree Essays

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This collection contains digitized SFU theses except for those theses submitted within the last 12 months. If you cannot find the thesis you are looking for please search Recently Submitted Theses as it may be a recently submitted thesis and thus not yet available in Summit.

Stochastic thermodynamics of Gaussian information engines

Date created: 
2021-08-06
Abstract: 

Stochastic thermodynamics is an emerging field of research that has received considerable attention in the past two decades. Among its most visible applications is to understand the connections between information and thermodynamics. Recent theoretical advances in this field have established that the second law of thermodynamics, suitably modified to account for information, sets the limits of information-to-energy conversion; however, these limits are generally derived for systems that are ideal and assume that all of the system’s energy can be extracted. Real systems on the other hand face constraints that may prevent them, both in principle as well as in practice, from achieving the predicted theoretical limits. Prompted by recent advances in experimental capabilities which allow for a high degree of control of mesoscopic systems, we explore the limits of information-to-work conversion in a simple “textbook example” colloid-based information engine that is implementable in the lab. We use this engine to explore the limits of information-to-work conversion when the engine is restricted to operate in a mode where long-term energy storage is prioritized. We find that restricting the engine to this mode of operation severely limits its ability to convert information to work compared to when the engine is optimized for raw energy extraction, without regards for whether the energy is stored or not. Nevertheless, in certain cases, it is possible to design the feedback control to have a work input which guarantees the engine stores energy at the highest achievable rate. We therefore find that information engines sometimes convert information to work most effectively when there is a mixture of external work input and information processing. Additionally, real engines face the conundrum of measurement noise. This complicates the feedback control and introduces biases in the estimates of the relevant thermodynamic quantities. To eliminate this bias, we use either a filter or we introduce feedback delays. Both strategies successfully eliminate the bias in the estimates; however, we find that using the filter has an additional benefit in that it allows us to compute a trajectory-level estimate of the information-processing costs. These results inform our theoretical understanding of the limits of real systems that convert information to work and provides the first measure of the information-processing costs for continuous variables.

Document type: 
Thesis
File(s): 
Supervisor(s): 
David Sivak
Department: 
Science: Department of Physics
Thesis type: 
(Thesis) M.Sc.

How can avalanche bulletins be more useful for recreationists? Exploring three opportunities for improving communication of avalanche hazard information

Author: 
Date created: 
2021-08-17
Abstract: 

Avalanche warning services release public avalanche bulletins to help backcountry recreationists develop risk management approaches for winter backcountry trips. To safely recreate in the backcountry, recreationists must be able to understand and apply the avalanche hazard information presented in the avalanche bulletin. The goal of this research was to test how key elements of the avalanche bulletin affect users’ interpretation of the hazard information within the avalanche bulletin, and to determine if modifications to the bulletin could increase its’ useability among recreationists. We conducted a survey with multiple sections to test if presentation of graphic information and interactive exercises can help recreationists apply spatial hazard information, as well has how users perceive the travel and terrain advice section of the bulletin. The results of these studies can be used by avalanche warning services to improve avalanche hazard messaging in their public avalanche bulletins.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Pascal Haegeli
Department: 
Environment: School of Resource and Environmental Management
Thesis type: 
(Thesis) M.R.M.

Investigating metabolic dysfunction and arrhythmogenesis in an early-onset atrial fibrillation patient cohort

Author: 
Date created: 
2021-04-23
Abstract: 

Despite the prevalence of atrial fibrillation (AF) and the burden it places on health care systems, there remains much that is unknown regarding heritable factors influencing its development and progression. In this study, I investigated whole-exome sequencing (WES) data from a cohort of patients presenting with early-onset AF to explore the role that metabolic dysfunction might play in contributing to disease onset. I curated a metabolism-related gene panel and, following in silico prediction of variant pathogenicity, performed gene-level burden testing using reference data from the Genome Aggregation Database (gnomAD) and the human mitochondrial genome database MITOMAP. I further explored genes associating with AF in the UK Biobank data set, and discovered associations with several AF comorbidities including diabetes, hypertension, and stroke.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Glen Tibbits
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Unveiling 21st century representations of Muslim women in French cinema

Date created: 
2021-04-12
Abstract: 

This thesis examines how recent French films (2015-2017) represent veiled female characters. The three films of this corpus (Fatima, Faucon 2015; Le Ciel Attendra, Mention-Schaar 2016; Cherchez la Femme, Abadi 2017) are selected for they not only highlight the limited representations that conform to the dominant views of the Muslim female ‘other’ in contemporary French society, but they also present the three archetypes common to representations of veiled characters: the submissive Maghrebi mother; the veiled woman as a subaltern; the radicalised Muslim girl. Since the early 2000s (Tarr, 2015), Maghrebi-French actresses are increasingly present in film, marking a growing visibility of 2nd-generation Maghrebi-French in contemporary France. Cinema is particularly powerful in its capacity to challenge or perpetuate the prejudices that contribute to societal discrimination toward minority groups. Despite their aim at challenging stereotypical views of veiled Muslim characters, these films also reinforce hegemonic views and social prejudices.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Gaëlle Planchenault
Department: 
Arts & Social Sciences: Department of French
Thesis type: 
(Thesis) M.A.

Why implement plug-in electric policies? Comparing policy discourse in newspapers across three Canadian provinces (2008-2018)

Author: 
Date created: 
2021-03-17
Abstract: 

Governments can implement a wide range of policies to increase the uptake of plug-in electric vehicles (PEVs). For example, regions differ in their focus on demand-focused policies that encourage consumers to purchase a PEV, versus supply-focused policies that encourage the industry to develop or sell PEVs. I explore how policy discourse, or how language is used to create meaning around policy issues, can shed light on policy implementation in the Canadian provinces of British Columbia, Ontario, and Québec during the decade 2008-2018. In Canada, Québec became the first to use supplyfocused policy, while British Columbia and Ontario relied on demand-focused policies. Using a selection of 984 newspaper articles, I adopt a mixed-method approach to analyze statements from governments and other actors. First, I conduct (quantitative) content analysis and analyze the frequencies of frames (selected aspects of reality) around PEVs and policies. Second, I conduct (qualitative) discourse analysis by investigating how frames unite to create meaning in simplified stories, storylines. Similar frames occurred in all three case studies: governments framed PEV policy to meet climate goals while emphasizing PEVs’ private benefits to consumers. Policy discourses differed by regions: Québec’s emphasized PEVs as part of economic independence;Ontario’s demonstrated more policy controversy; and British Columbia’s remained silent over supply-focused policies during the time period. In British Columbia and Québec, the automobile industry favored a demand-focused policy approach. While this study remains exploratory, analyzing and comparing policy discourses can shed light on why policymakers in different regions may gravitate towards different policy approaches over time.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Jonn Axsen
Department: 
Environment: School of Resource and Environmental Management
Thesis type: 
(Thesis) M.R.M.

Investigations into the value of labeled and unlabeled data in biomedical entity recognition and word sense disambiguation

Date created: 
2021-03-31
Abstract: 

Human annotations, especially in highly technical domains, are expensive and time consuming togather, and can also be erroneous. As a result, we never have sufficiently accurate data to train andevaluate supervised methods. In this thesis, we address this problem by taking a semi-supervised approach to biomedical namedentity recognition (NER), and by proposing an inventory-independent evaluation framework for supervised and unsupervised word sense disambiguation. Our contributions are as follows: We introduce a novel graph-based semi-supervised approach to named entity recognition(NER) and exploit pre-trained contextualized word embeddings in several biomedical NER tasks. We propose a new evaluation framework for word sense disambiguation that permits a fair comparison between supervised methods trained on different sense inventories as well as unsupervised methods without a fixed sense inventory.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Anoop Sarkar
Department: 
Applied Sciences: School of Computing Science
Thesis type: 
(Thesis) Ph.D.

Analyzing the effect that non-uniform receptor distribution and secretion of chemo attractants has on cell chemotaxis

Author: 
Date created: 
2021-12-10
Abstract: 

Cell-cell signaling is a fundamental process of organisms during development, throughout their lifetime and in the course of cancer growth. In mammary tumors, tumor cells interact with macrophages via short-ranged signaling (paracrine) involving the growth factors EGF and CSF-1. This paracrine signaling enhances tumor cell invasion into surrounding tissues and blood vessels. Here I examined the roles that asymmetric receptor distribution, ligand secretion and gradient detection at the cellular level play in cancer cell invasion. Although there are already mathematical cell models that simulate cell movements in multicellular systems, none have included asymmetric distribution at the cell level. We incorporated non-uniform receptor density, ligand secretion and gradient detection in a 3-D individual cell-based model, that had been used to simulate the EGF/CSF-1 paracrine signaling in a tumor environment Our model can be used for any multicellular systems, where cells secrete and chemotax towards ligand gradients. Our model was optimized to reduce the computational cost of including non-uniform distributions at the sub-cellular level, when simulating thousands of interacting cells.I demonstrated that even when simulating thousands of cells, at scales much larger than the cell, non-uniformities at the single cell scale can significantly change the results. My simulations showed that non-uniform gradient detection dramatically enhanced the invasion of both tumor cells and macrophages and that non-uniform secretion significantly altered the invasion patterns of those cells. With no-flux boundary condition at the bottom, non-uniform secretion at either the front or back of the cell delayed the tumor cell invasion. However, secretion at the front enhanced macrophage invasion, while secretion at the back delayed it. Ultimately, fewer tumor cells invaded when secretion was at the front compared to uniform secretion and secretion at the back. These simulations helped us understand how the boundary conditions can potentially have a large impact on invasion profiles. They suggest that in vitro experiments with artificial boundary conditions may behave quite differently than the in vivo experiments that do not have no-flux boundary conditions. Overall, my simulations provide insight into how non-uniform receptor density, ligand secretion and gradient detection modify cell migration patterns. These simulations also suggest that it is very important to incorporate non-uniformities at the cell level when modelling chemically interacting multicellular systems.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Eirikur Palsson
Department: 
Science: Department of Physics
Thesis type: 
(Thesis) M.Sc.

Boussinesq dynamics at a cloud edge: Theory and simulation

Author: 
Date created: 
2021-12-15
Abstract: 

A consequence of air becoming increasingly less dense with altitude is that the vertical displacement of air against gravity results in up and down oscillatory motion -- much like the restoring force of a spring trying to maintain its equilibrium. This gravity-driven buoyancy effect is what sustains the vertical atmospheric motions known as gravity waves. Just as density decreases with height, the atmosphere is also stratified in its other thermodynamic properties. It becomes lower in pressure and generally cooler with height. When air is displaced vertically, with respect to this stratification, it alters the local thermodynamic state. Additionally, when moisture is included it can exist in either its vapour phase or as suspended liquid water droplets, the latter of which defines the presence of cloud. Altering the moist thermodynamic state can lead to the condensation and evaporation of water. In this way, gravity waves can impact the formation and dynamics of cloud. In this thesis, a simplified model is developed extending the classical Boussinesq approximation for gravity waves to include the effects of vapour-liquid phase change. The result is a mathematical framework that couples the fluid dynamics of gravity waves to the thermodynamics of moisture giving a theory that describes the geometrical evolution of cloud. From this model a particular wave-cloud interaction is identified which has a gravity wave trapped in the clear region below a cloud layer. This is commonly known as a waveguide or wave duct. In this setting, vertical motions of the wave lead to the phase change of water at the cloud-edge boundary resulting in a newly identified mechanism for wave propagation on the edge of cloud. This dynamical solution is constructed within the full physics numerical model ``cm1.'' This represents a first analytically derived moist dynamical solution realized within a numerical weather model. A quantitative comparison of the cm1 computed and approximate Boussinesq solutions show a high degree of agreement in the dynamics. This validates that the moist physics of cm1 are true to the Boussinesq dynamical analysis and illustrates that the cloud-trapped wave-duct solution is achievable in idealized atmospheric conditions.

Document type: 
Thesis
File(s): 
Supervisor(s): 
David Muraki
Department: 
Science: Department of Mathematics
Thesis type: 
(Thesis) Ph.D.

Filtering in non-Intrusive load monitoring

Date created: 
2021-12-09
Abstract: 

Being able to track appliances energy usage without the need of sensors can help occupants reduce their energy consumption. Non-intrusive load monitoring (NILM) is one name for this topic. One of the hardest problems NILM faces is the ability to run unsupervised – discovering appliances without prior knowledge – and to run independent of the differences in appliance mixes and operational characteristics found in various countries and regions. This thesis showcases two filters that are used to denoise power signals, which results in better clustering accuracy for NILM event based methods. Both filters show to outperform a state-of-the-art denoising filter, in terms of run-time. A fully unsupervised NILM solution is presented, the algorithm is based on a hybrid knapsack problem with a Gaussian mixture model. Finally, a novel metric is developed to measure NILM disaggregation performance. The metric shows to be robust under a set of fundamental test cases.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Stephen Makonin
Rodney Vaughan
Department: 
Applied Sciences: School of Engineering Science
Thesis type: 
(Thesis) M.A.Sc.

Our Eyes Will Adjust

Author: 
Date created: 
2021-09-20
Abstract: 

Our Eyes Will Adjust is an experiential immersive performance and installation. With an attention to perception and embodied seeing, this work explores the multidimensionality of our energetic and material interconnections to the visibly hidden.  The work moves from the perception of the individual self at the center of experience to the Universal Self – woven into the web of Universal matrix which is cyclically governed rather than centrally focused. Influenced by ancestry, nature and new technology, the work is presented in three different settings: live in-person performance, live streamed performance and dance on film.  OEWA is a dance of the in-between dualities of light and darkness, energy and matter, form and formless meet, converse, and entangle.

Document type: 
Graduating extended essay / Research project
File(s): 
Supervisor(s): 
Robert Kitsos
Department: 
Communication, Art & Technology: School for the Contemporary Arts
Thesis type: 
(Project) M.F.A.