VictorJuiz/thesis huggingface dataset:
Applications of Photonic Crystals to Photovoltaic Devices

Photonic crystals are structures that exhibit wavelength-scale spatial periodicity in their dielectric function. They are best known for their ability to exhibit complete photonic band gaps (PBGs) - spectral regions over which no light can propagate within the crystal. PBGs are specific instances of a more general phenomenon, in which the local photonic density of states can be enhanced or suppressed over different frequency ranges by tuning the properties of the crystal. This can be used to redirect, concentrate, or even trap light incident on the crystal. In this thesis, we investigate how photonic crystals can be used to enhance the efficiency of photovoltaic devices by trapping light. Due to the many different types of photovoltaic devices in existence (varying widely in materials used, modes of operation, and internal structure), there is no single light trapping architecture that can be applied to all photovoltaics. In this work we study a number of different devices: dye-sensitized solar cells, polymer solar cells, silicon-perovskite tandem cells, and single-junction silicon cells. We propose novel photonic crystal-based light trapping designs for each type of device, and evaluate these designs numerically to demonstrate their effectiveness. Full-field optical simulations of the cell are performed for each design, using either finite element method (FEM) or finite-difference time-domain (FDTD) techniques. Where appropriate, electrical modelling of the cell is also performed, through either the use of a simple one-diode model, or by obtaining full solutions to the semiconductor drift-diffusion equations within the cell. In all cases we find that the photonic crystal-based designs significantly outperform their non-nanostructured counterparts. In the case of dye-sensitized and polymer cells, enhancements in light absorption of 33% and 40% (respectively) are seen, relative to reference cells with planar geometries. In the case of silicon-perovskite tandem cells and silicon cells, projected power conversion efficiencies of over 30% are obtained, well beyond the current world record for silicon-based cells. We conclude the thesis with a discussion on the overall prospects for photonic crystal-based solar cells, with a focus on the factors that make solar cell technologies amenable to light trapping.

Keywords: light trapping
optics
photonic crystals
photovoltaics
solar cells
solar energy
Advisor: John, Sajeev
Evolutionary Alternatives on the Road to a New Specificity in a G Protein-Coupled Receptor

Cells sense change in their external environment and react appropriately through the action of signaling pathways. This process is initiated by receptor proteins with high degrees of specificity for a particular stimulus. G protein-coupled receptors form the largest family of membrane protein receptors and their ability to sense a broad variety of ligands is unparalleled despite their common ancestral origin. How GPCRs evolved their unique specificities is unknown, although ligand binding affinity is often given a central role. The goal of this thesis was to assess the possible contributions of secondary mechanisms of specificity, namely ligand efficacy and downstream signaling regulation, to changes in ligand recognition. Through directed evolution, we generated a yeast pheromone receptor with an altered specificity in two steps. First, promiscuous receptors were obtained through either improved binding affinity or weaker molecular interaction with a negative regulator of signaling. Second, a ligand-discriminating receptor was obtained from a promiscuous variant solely by reducing the efficacy of the native pheromone. These findings demonstrate the importance of assessing GPCRsâ pharmacological profiles in their native context, where signaling trumps binding affinity in significance.

Keywords: directed evolution
g protein-coupled receptor
ligand efficacy
network evolution
receptor specificity
Advisor: Chang, Belinda
Peisajovich, Sergio G
Child Welfare and the Imperial Management of Childhood in Settler Colonial Canada, 1880s-2000s

The Canadian child welfare system perpetuates deeply colonial relations. Indigenous children are being removed en masse, die at exceptionally high rates in the system, and the child welfare personnel is primarily drawn from the white settler society. This dissertation seeks to find answers to the question of how this present-day reality came to be and how Indigenous child removal can continue so vigorously. This dissertation is a genealogical inquiry into the beginnings and development of the Canadian child welfare system. Through extensive archival research, it traces how this institutional framework re-articulates relations of coloniality – relations through which Indigenous peoples are rendered subjects to be managed and white settlers are re-inscribed as dominant, superior, and – despite the enormous violence that underpins their subject positions – as ‘caring’. This dissertation advances the argument that the management of childhood is of central concern to the colonial/racial state. Child welfare emerged as an imperial project, for the purpose of white settler colonial nation-building. Animated by a colonial concern that the white race be preserved, early child-rescue initiatives focused on ‘saving’/managing the damaged but salvageable white settler child. These children were to be prevented from ‘sinking’ to the level of the Indian or racial Other, and molded into useful citizens for the white settler colony. At the turn of twentieth century, Indigenous children were rendered extraneous to the emerging field of child welfare. State interest in the Indigenous child was an annihilative and carceral interest, animated by the idea that Indigenous children had to be removed and contained in institutions (i.e. Indian Residential Schools). While Indian Residential Schools were eventually phased out, the colonizers’ focus on Indigenous child removal remained. Indigenous child removal emerged as a central modality of colonial power, the intent of which was to effect Indigenous erasure and dispossession for the proliferation of the settler colony. This modality of power continues through the child welfare system today, sustaining the settler society’s annihilative and accumulative impulse, continuing to dispossess Indigenous peoples of their lands and sovereignty.

Keywords: child welfare
Indigenous children
management of childhood
race and imperialism
settler colonialism
social work
Advisor: Razack, Sherene
Quantum-enhanced Phase Estimation in Optical Interferometry

Quantum-enhanced interferometers utilize non-classical states of light in order to surpass the limitations imposed by classical physics on phase measurement sensitivity and resolution. We review key scientific developments in this growing field of research and derive fundamental metrology concepts, namely the Cram\'{e}r-Rao bound and the Fisher information, which are used to analyze the metrological performance of quantum states of light. We propose a supersensitive quantum interferometry protocol that can be amplified to the macroscopic realm (i.e. the mean number of photons of the probe state can reach approximately 100,000 photons) using contemporary techniques of spontaneous parametric down conversion. The parity measurement on the output field asymptotically saturates the quantum Cram\'{e}r-Rao bound, which scales like the Heisenberg limit. We uncover the role of photon statistics on phase sensitivity and rule out the necessity of mode entanglement for quantum-enhanced interferometry. Based on these insights we outline a practical metrology technique (independent of mode entanglement) that measures a phase delay of a single-mode anti-squeezing operation. This scheme can also be scaled macroscopically using contemporary techniques and is shown to significantly surpass the shot-noise limit (SNL) in the presence of realistic losses. Finally, the physical resources that enable quantum-enhanced interferometry is studied by analyzing the quantum Fisher information (QFI) using the first quantization and the second quantization formalisms of quantum mechanics. It is shown that increasing the intra-mode correlations of an interferometer (as quantified by the second order Glauber coherence function) can be conducive to attaining a quantum advantage in phase estimation; whereas, introducing mode entanglement can reduce phase sensitivity. Using the first quantization description, we derive a formula for the QFI that shows explicitly how the Heisenberg scaling term depends on particle entanglement.

Keywords: Interferometry
Metrology
Quantum Optics
Advisor: James, Daniel F. V.
The Predictors and Consequences of Prejudice in Online Video Games

More than half of the people in North America play video games, and most play often. Despite their popularity, video games are controversial and have been heavily criticized for fostering toxic environments in which racism, sexism, and heterosexism occur frequently. In a series of four studies I explore several possible explanations for why prejudice is more common in video games than in other contexts and what effect prejudice in this environment has on gamers. In Study 1, I test if people perceive online gaming differently from face-to-face interactions. In Study 2, I develop a more nuanced understanding of peopleâ s perceptions of video games by testing whether different genres of games are perceived differently (e.g., puzzle games versus role-playing games). In Studies 1 and 2, I establish that people perceive video games as more prejudiced environments than face-to-face interactions, with action and role-playing games being seen particularly negatively. In Study 3, I explore what might account for why prejudiced behaviour seems to be common in video games. I explore the role of norms and of individual differences in a structural equation model predicting bigoted behaviour. Both norms (how often other gamers make bigoted comments) and individual differences (Right-Wing Authoritarianism, Social Dominance Orientation, Empathy and Internal Motivation to Respond without Prejudice) predict self-reported prejudiced behaviour. Study 3 emphasizes the importance of taking a multifaceted approach to understanding prejudiced behaviour. Finally, in my fourth study, I explore the consequences of prejudice in online gaming. Using a daily diary study I found that female gamers experience more bigoted comments than male gamers and are more strongly affected than are male gamers. These four studies provide an introduction to the online gaming environment and lay a foundation for future work to reduce prejudice in online gaming.

Keywords: Intergroup Relations
Prejudice
Stereotyping
Video Games
Advisor: Chasteen, Alison L.
What Fate Forbids: Reading Precarity in 21st-Century Texts

My dissertation engages with contemporary texts, cinema, and technology that emphasize the transformative and creative potential of the material world. These texts propose a world made not from a multiplicity of inert things, but through the changing and emergent quality of all matter. They not only call into question ontological separations between objects, people, and nature, but also emphasize their mutual constitution. When the world is conceived as a meshwork of juxtapositions, interactions, and encounters, events do not follow one another in the particular causal linearity upon which narrative and history are usually founded. For this project, I analyze Agustín Fernández Mallo’s Nocilla Dream (2006), David Mitchell’s Ghostwritten (1999), two collaborative projects headed by Anders Bojen and Kristoffer Ørum titled Radiant Copenhagen (2009) and Topographies of the Insignificant (2010), and Singapore filmmaker Tan Pin Pin’s documentary Invisible City (2007). Until now, these narratives have been largely considered representative of an increasingly globalized and urbanizing world where recurrent themes of postmodernism and of globalization discourses make an obligatory appearance. These approaches tend to examine global and cultural mobilities while still deploying the modernist territorial spatiality that understands nature as fundamentally stable. I contend that each of these varied texts constructs a vibrant materialism that unsettles binary assumptions about nature and culture and challenges the linear and determinist underpinnings upon which discourses of progress are founded. I argue that the dynamics present in these texts are best captured by “thinking conjuncturally” (Low and Barnett 7): that is, by shuttling back and forth among the different trajectories and temporalities through which events come together. This approach serves to apprehend the manner in which narrative is constructed as being crosscut by the multiple temporalities of all manner of actors.

Keywords: assemblage
nature/culture binary
new materialism
non-linearity
precarity
twenty-first century
Advisor: Davidson, Robert
Observational constraints on air quality and greenhouse gases in the Greater Toronto Area

Urban areas are highly complex environments that are large sources of a variety of atmospheric pollutants. To better understand the spatial and temporal variability of carbon dioxide (CO2) emissions in the GTA, we developed the Southern Ontario CO2 Emissions (SOCE) inventory, a fine resolution inventory based on emissions from seven source sectors for the year 2010. When the SOCE inventory was used in combination with a chemistry transport model, agreement with mixing ratios measured in southern Ontario was strong. We found that contributions from area sources (primarily natural gas combustion) played a dominant role overnight (contributing >80 %) while on-road sources played a significant role during the day (contributing >70 %). When a fine-resolution CO2 inventory is not available, stable carbon isotopes (δ13CO2) are often used as tools to source apportion CO2. We combined model output CO2 mixing ratios with GTA-specific δ13CO2 signatures of the dominant anthropogenic sources of CO2, determined as part of this work, to simulate hourly δ13CO2. When the simulated δ13CO2 was compared to measurements at the Downsview site, the agreement was generally good. To evaluate the use of Keeling and chemical mass balance (CMB) analyses, we estimated the δ13CO2 signature of the local enhancement from both model output and measurements and found that it was heavier (~3 per mil) than that calculated by the SOCE inventory. The emission of primary pollutants in urban areas (e.g. nitrogen oxides (NOx) and carbon monoxide (CO)) can also contribute to the production of secondary pollutants such as ozone (O3). Data from a governmental monitoring network in the GTA from 2000-2012 were used to explore the impact of O3 precursors on local O3 levels. Non-linear chemistry and influence of meteorology explained why reductions in precursor levels did not lead to improvements in O3, particularly for 2012.

Keywords: Carbon dioxide
Chemical transport modelling
Source apportionment
Stable carbon isotopes
Advisor: Murphy, Jennifer
Borderspaces in Text and Image: Representing Canada in Chinese Textual Culture (1868-1938)

This dissertation examines the concept of “borderspaces” as productive sites of investigation. Borders are understood as lived spaces—hence, “borderspaces”—inhabited by people and languages. These borderspaces point to intimate connections between the nations of Canada and China that multiply the ways the relationship between the two nations can be imagined beyond the figure of the diasporic immigrant. Most investigations in Sino-Canadian studies emphasize the immigrant community but overlook the lived and mediated experiences of other Chinese individuals who also visited and/or wrote about Canada for Chinese-reading audiences in China at this time. Using Chinese-language travel writings and fiction about Canada, this dissertation considers the discursive linkages between Canada and China produced by Chinese diplomats, officials, overseas students, and translators who represented Canada for audiences in China during the nineteenth and twentieth centuries when travel to Canada was becoming increasingly restrictive for ethnic Chinese. Examining these travel writings and fiction through the lens of minor transnationalism (Lionnet and Shih), which emphasizes the experiences of individuals who grappled with colonial, imperial, and global dominance and control, this dissertation draws attention to minor writings that critique hegemonic and homogenizing narratives of global history. As such, the notion of borderspaces highlights the uneven experiences of ethnic Chinese in North America while simultaneously showcasing the agency of Chinese writers and translators in dealing with issues of representation they confronted as Chinese individuals in the context of North American discrimination. This dissertation explores four different concepts of borderspaces that produce dissonance against major singular narratives of Chinese oppression in North America. It examines how discriminatory laws, imperial desires, mass migrations, and power imbalances affected Chinese travellers and writers as well as how their writings offer a complicated critique and commentary of China’s historical position in the world. This research thus provides a more nuanced picture of the relationship between Canada and China in the nineteenth and twentieth centuries by demonstrating that first, multiple vectors (both physical and intangible) connect two nations and that second, these spaces are significant to the project of critical global history.

Keywords: Chinese Canadian Studies
Chinese Exclusion Act
Chinese in Canada
Chinese Translated Fiction
Chinese Travel Writing
Critical World History
Advisor: Liu, Johanna C.
Rectangular Hollow Sections Subject to Blast Loading

As protective design engineering becomes more prevalent, cold-formed steel rectangular hollow sections (RHS) are often desired components for blast-resistant design. In addition to the energy-dissipating characteristics of steel, RHS have good torsional characteristics and square RHS have no weak axis in flexure, all ideal properties for response to blast loading. RHS have the added benefit of enabling the use of concrete-filling to create composite members which take advantage of the added mass and local stability provided by the concrete. Accordingly, the behaviour of unfilled RHS, concrete-filled RHS, and concrete-filled double-skin tubes (CFDSTs) subjected to air-blast loading is investigated. An important aspect of the response of RHS subject to air-blast loading is the material response of cold-formed steel under elevated strain-rates. Dynamic tensile tests have hence been performed on sub-size tensile coupons taken from the flats and corners of cold-formed RHS members. Dynamic yield stresses were obtained at strain rates from 0.1 to 18 s-1. The dynamic increase factor was calculated for each data point and synthesized with previous cold-formed RHS tests at even higher strain rates (100-1000 s-1). The data set was used to determine Cowper-Symonds and Johnson-Cook parameters. The resulting material models can be used to determine the strength increase of cold-formed RHS subject to a wide range of impulsive, elevated strain-rate loads. For the first time, the behaviour of unfilled RHS, concrete-filled RHS, and CFDSTs subject to air-blast loads has been investigated through large-scale testing. These arena trials illustrated the excellent performance and ductility of both the unfilled and composite cold-formed tubular steel members under extreme blast loads, without any fractures experienced in the cross-section. These instrumented tests provided much performance data that enabled the validation of subsequent models, using both single-degree-of-freedom and explicit finite element analysis. A parametric study was conducted with the validated finite element model to further characterize the response of RHS under air-blast loading. The influence of several key variables on the response of the various tubular members was determined and design guidance is provided.

Keywords: blast
cold-formed steel
explicit finite-element analysis
parametric study
rectangular hollow section
single-degree-of-freedom analysis
Advisor: Packer, Jeffrey A
Information Behavior and Knowledge Management in Project-Based Learning (PBL*) Engineering Teams: A Cultural-Historical Activity Theory Approach

This research studies how student engineering problem-based learning teams engage information challenges as they build sustained knowledge-based organizations. These challenges are framed by cultural-historical activity theory (CHAT), a framework that situates individual and collective activity in social and cultural foundations. CHAT notes points of contradiction that can influence a teamâ s progress towards its intended collective outcome, with different teams identifying and approaching contradictions in different ways. This research looks specifically at Formula SAE (FSAE) teams, an automotive racing project sponsored by the Society for Automotive Engineers. This research analyzed interview and survey data from 42 respondents in the North American context; 33 from currently competing teams, 9 from faculty advisors, judges and alumni. Results show a diverse range of responses to CHAT contradictions, including calibrating individual motivations to create a team with a diverse range of skills, integrating multiple sources of explicit and tacit knowledge in research and development, negotiating relationships with larger administrative powers, managing knowledge transfer and organizational renewal in a high turnover context, and negotiating when it is best to cooperate with versus compete against teams striving towards the same outcome. This research situates CHAT as an effective theoretical grounding for similar project- based learning team research, especially for teams operating as long-term knowing organizations. This research highlights best practices that could inform student team leaders in this and similar engineering problem-based learning team contexts. It is also hoped this research gives school administrators guidance on how to support such teams and integrate their core activities into curriculum. Future research directions include expanding to the international FSAE community and how the FSAE experience influences alumni career goals over an extended period of time.

Keywords: activity theory
design education
engineering education
Formula SAE
information behavior
project-based learning
Advisor: Choo, Chun Wei