VictorJuiz/thesis huggingface dataset:
Molten Salt Electrodeposition of Silicon in Cu-Si
Keywords: Electrowinning
Molten salt
Solar grade silicon
Solvent refining

Widespread use of solar energy has not been realized to date because its cost is not competitive with conventional energy sources. The high price of solar grade silicon has been one of the barriers against photovoltaic industry achieving its much anticipated growth. Therefore, developing a method, which is energy efficient and will deliver inexpensive silicon feedstock material is essential. The electrodeposition of Si from a cryolite-based melt was investigated in the present work as a possible solution. This study proposed electrowinning of Si in molten Cu-Si alloy, to decrease the working temperature and increase the efficiency. Solvent refining can be used to recover Si from Cu-Si and also as a second purification method. The physicochemical properties of the potential electrolyte, cryolite-SiO2 melts, were studied in the first step of this work. The deposition potential of Si on a graphite cathode was measured to determine the working potential and the effect of SiO2 concentration on it. In the next step, the deposition potential of Si from cryolite-SiO2 melt on Cu and Cu-Si cathodes was determined using cyclic voltammetry. Next, the cathodic and the anodic current inefficiencies of the process were measured. Continuous analysis of the evolved gas enabled the instantaneous measurement of the current efficiency and the kinetics of the deposition. Finally, the effectiveness of the process in delivering high purity Si was investigated. Si dendrites were precipitated out of the Cu-Si cathode and recovered to determine the purity of the final product as the final step of this study. The produced Si was separated from the alloy matrix by crushing and acid leaching and the purity was reported. The findings of this research show that the proposed method has the potential to produce high purity silicon with low B content. Further development is required to remove some metallic impurities that are remained in Si.
Problems in Service Operations with Heterogeneous Customers
Keywords: Call center
Facility location
Heterogeneous Customers
Marketing-Operations Interface
Service Operations

We study three problems in service operations with heterogeneous customers. In Chapter 2, we consider the problem of locating facilities of two types at nodes of a tree network, where each facility incurs a fixed cost. Customers may need just one type of service, or both types. It is required to minimize the sum of the total transportation and fixed costs. For the problem with a single facility of each type, we present an O(n) exact algorithm, and for the problem with multiple facilities of each type, we present an O(n^5) algorithm.In Chapter 3, we study the problem of maximizing profits for an inbound call center with abandonment by controlling customer acquisition, retention, and service quality via promotions, priorities, and staffing. This chapter makes four contributions. First, we develop a novel marketing-operations model of a call center that captures the evolution of the customer base as a function of past demand and queueing-related service quality. Second, we characterize the optimal controls analytically based on a deterministic fluid approximation and show via simulation that these prescriptions yield near-optimal performance for the underlying stochastic model. Third, we derive three metrics which play a key role in call center decisions and link customer and financial parameters with operational service quality, reflecting the system load and the priority policy. Fourth, we generate novel guidelines on managing a call center based on these metrics, the cost of promotions, and the capacity cost per call.In Chapter 4, we extend our call center model by considering a firm that follows a periodic advertising policy and receives time-varying demand response. The objective function is to maximize profit by controlling the advertisement policy and service levels for new and base customers. We show that the optimal service level allocation to new and base customers takes the form of a bang-bang policy. That is, at each moment during the advertisement period, the call center should serve all or none of the calls from each type of customers, and the policy transitions between these two extremes at most once during the advertisement period.
Representations of Gender and Embodiment in Children's Picture Books
Keywords: Children
Embodiment
Gender
Media
Picture Books
Stereotypes

This study examined representations of embodiment among male and female characters in a sample of children's picture books. The data was comprised of four book samples: best-selling books featuring female protagonists, best-selling books featuring male protagonists, multicultural books featuring female protagonists, and multicultural books featuring male protagonists. A total of 112 books were qualitatively analyzed via conventional content analysis and multimodal discourse analysis to investigate how the book narratives and illustrations depicted embodied experiences for male and female characters. Two core-categories emerged. The first identified Observed Norms and Ideals of Gender throughout the analyzed books, specifically within the domains of Behaviour, Appearance, and Ability. The second core-category delineated discourses that pertained to Family Relational Processes. Quantitative content analysis was then used to assess for significant differences in thematic occurrences across the four samples. Overall, quantitative results demonstrated that appearance-based norms occurred most frequently in best-selling books featuring females, that stereotypes related to socioeconomic status were most prevalent in multicultural picture books featuring males, and that the role of the family was highlighted more often in multicultural books than it was in best-selling books. This research expanded on other assessments of gender depictions in children's literature by delineating the complex range of embodied experiences that are depicted for male and female picture book characters.
Micro- and Nano-scale Optoelectronic Devices Using Vanadium Dioxide
Keywords: phase transition material
Vanadium dioxide

Miniaturization has the potential to reduce the size, cost, and power requirements of active optical devices. However, implementing (sub)wavelength-scale electro-optic switches with high efficiency, low insertion loss, and high extinction ratios remains challenging due to their small active volumes. Here, we use the insulator-metal phase transition of vanadium dioxide (VO2), which exhibits a large and reversible change in the refractive index across the phase transition to demonstrate compact, broadband, and efficient switches and photodetectors with record-setting characteristics. We begin by analyzing the electrical and optical properties of VO2 thin films across the phase transition and discuss the fabrication processes that yield micron- and nano-scale VO2 devices. We then demonstrate a surface plasmon thermo-optic switch, which achieves an extinction ratio of 10 dB in a 5 um long device, a record for plasmonic devices. The switch operates over a 100 nm optical bandwidth, and exhibits a thermally limited switching time of 40 us. We investigate the current and voltage induced switching of VO2 in nano-gap junctions and show optical switching times as short as 20 ns. The two terminal VO2 junctions are incorporated in a silicon photonics platform to yield silicon-VO2 hybrid waveguide devices with a record extinction ratio of 12 dB in a 1 um long device. In photodetector mode, the devices exhibit a nonlinear responsivity greater than 12 A/W for optical powers less than 1 uW. This device is the smallest electrically controlled and integrated switch and photodetector capable of achieving extinction ratios > 10 dB/um. We finally investigate the ultra-fast thermal heating in gold nano-apertures and demonstrate that electron heating can change the gold lattice temperature by 300 K in tens of picoseconds. These nano-apertures can be hybridized with VO2 to demonstrate high extinction and ultrafast optical switches.
Bee Foraging in Space and Time: Linking Individual Behaviour to Pollination
Keywords: Bombus
bumble bee
flower
foraging behaviour
pollination
spatial scale

In plant communities, flowers are patchy in space and time over many scales. Flower-feeding animals make complex foraging decisions in this setting, but they may respond in characteristic ways to variation in floral distribution and the presence of different plant species. For plant species that rely on animals to disperse their pollen for sexual reproduction, pollination will reflect these animal foraging decisions. Because many pollinators are highly mobile and return to foraging areas over time, they may affect plant pollination over scales broader than typically considered (a few metres and within foraging bouts). My dissertation explores how individual pollinators respond to floral resource variation, and the implications for plant pollination success. I do so over relatively broad spatial and temporal scales, by studying the interactions between bumble bees (Bombus spp.) and three plant species (Delphinium barbeyi, Gentianopsis detonsa, and Gentiana parryi) in Rocky Mountain subalpine meadows. As an assemblage, bumble bees concentrated their visits in resource rich areas over tens to hundreds of metres. This caused one plant species to act as a bumble bee magnet in an area, which increased the pollination of another plant up to 30 m away. In addition, many individual bees returned repeatedly to small areas, which also caused positive pollination interactions between plants. When a preferred flower declined, bees stayed faithful to their site and not their preferred species. Consequently, a newly-blooming plant quickly inherited a set of returning bees. I also showed that as a result of its late-flowering time, Gentiana receives visits by both female and male bumble bees. Intriguingly, the males were abundant and effective pollinators, despite not being considered by researchers as such. Overall, my work shows that pollinators can respond to flowers over broad spatial and temporal scales that can affect plant pollination success in unrecognized ways.
Nonlinear Periodic Structures: From Classical to Quantum Devices
Keywords: entanglement
frequency conversion
Nonlinear optic
optical signal processing
Quantum

In this thesis, nonlinear periodic structures and their applications in both classical and quantum regime are investigated. New theoretical models are developed, and novel applications of nonlinear periodic structures are proposed and demonstrated. The theoretical studies, both design and simulation, are based on but not limited to InGaAsP material. A new method, namely the time-domain transfer-matrix (TDTM), is presented to simulate optical pulse propagation in layered media with resonant nonlinearity. As there were no satisfactory methods in the literature to model this problem, in order to validate and compare with the TDTM method, the standard FDTD method is generalized to include the rate equation in the analysis of semi-conductors. Also in this work, optical manipulation of absorption in periodic structures is studied for the first time. Thanks to the large accessible nonlinearity that results from the absorption saturation and frequency selectivity of periodic structures, a sensitive and compact optical limiter is designed. The novel design and modeling work developed in this thesis has provided new insights and tools to the utilization of resonant nonlinearities in compact all-optical devices.The experimental studies are based on quasi-phase matched AlGaAs superlattice waveguides. These devices have been previously designed and used for classical optical wavelength conversion such as second harmonic generation and difference frequency generation. In this work, these devices are exploited for spontaneous down conversion, which is a quantum effect, for the first time, through this process, entangled photon pairs are generated. Unprecedented performance, in terms of brightness and purity, of III-V semiconductor-based entangled photon sources has been demonstrated here. Moreover, the quantum properties of these entangled photons are characterized. The experimental studies presented in this thesis open up new application areas for III-V nonlinear optical devices as quantum sources and convincingly demonstrate the promising role of such devices will play in future quantum technologies.
The Ecological Context of Pollination: Variation in an Apparent Mutualism
Keywords: Native bees
Plant-insect interactions
Pollination

What makes a good pollinator? As pollinators perform the function of pollination, exporting and delivering grains between conspecific plant species, the floral visitor's foraging interests and the messy process of pollination interfere; many pollen grains are removed but not delivered. "Conditionally parasitic" floral visitors "waste" so much pollen (from a plant perspective) that they sometimes reduce total pollen delivery, the total number of pollen grains transferred to conspecific plant stigmas. Most pollinators visit plants with a diverse assemblage of other floral visitors; as pollinators remove, transport, and deposit pollen, they interact indirectly with one another through the supply of available pollen. These interactions can result in conditional parasitism because they affect the number of pollen grains that are successfully transported to stigmas. In this thesis, I explore how pollinator wastefulness and variation in pollinator assemblages may affect pollen export and delivery. I document a particular ecological situation in which a pollen-specialist ("oligolectic") bee and a nectar-collecting fly visit concurrently. In this system, pollen removal by the oligolectic bee results in substantial and rapid pollen depletion, which suggests that pollen wastefulness may be costly. The assemblage of pollinators varies widely throughout the geographic range of the plant; citizen scientists and I documented a consistent geographic pattern. These geographic differences correspond with variation in floral traits that are linked to pollen transfer by bees and flies. Finally, I use a simulation model to explore what ecological contexts will cause a floral visitor to increase or decrease overall pollen delivery. As a whole, these data provide substantial evidence that conditional parasitism may occur, and help elucidate aspects of plants, pollinators, and mechanisms of pollen transfer that may make it more likely. Moreover, I document plant traits that may be a result of selection mediated by conditionally parasitic floral visitors.
Affinity-based Growth Factor Delivery from Injectable Hydrogels for Tissue Engineering
Keywords: affinity release
bioconjugation
controlled release
drug delivery
mathematical modelling
protein release

Due to the complexities of tissue repair or regeneration processes, effective clinical strategies have been impaired by both poor delivery of therapeutic agents to the site of injury and a lack of sustained release that is required for long-term efficacy. In this thesis, a strategy for delivering protein therapeutics in a localized and sustained fashion is presented within the context of these regenerative medicine challenges. An affinity-based system was developed whereby transient interactions between complementary binding partners were used to slow the diffusional release of a therapeutic from a polymeric delivery matrix. The Src homology 3 (SH3) domain, which binds a library of SH3-binding peptides, with varying affinity (10
Two Random Multiplicative Processes: Multiplicative Cascades and Eigenvectors of the Random Schrodinger Operator
Keywords: Point Processes
Probability
Random Measures
Random Schrodinger Operators
Stochastic Process

In this thesis we focus on two distinct random processes constructed using a sequence of independent identically distributed random variables along with a product structure on the underlying space. The first, a collection of random variables attached to vertices of the rooted binary tree, uses the multiplicative structure of paths along the tree while the second, a collection of two by two random matrices, uses the usual multiplication of matrices.In the first chapter we construct a continuous time version of the multiplicative cascade. The multiplicative cascade can be thought of as a randomization of an initial measure on the boundary of a tree, constructed from an independent, identically distributed collection of random variables attached to the tree vertices. The new random measure is constructed from the old by weighting the measure of any vertex in the the tree by the product of the random variables along the path from the root to the vertex. Given an initial measure with certain regularity properties, we construct a continuous time, measure-valued process whose value at each time is a cascade of the initial one. We do this by replacing the random variables on the vertices with independent increment processes satisfying certain moment assumptions. This process has a Markov property: at any given time it is a cascade of the process at any earlier time by random variables that are independent of the past. It is also a martingale and, under certain extra conditions, it is also continuous. For Gaussian independent increments processes we develop the infinite-dimensional stochastic calculus that describes the evolution of the measure process, and use it to compute the optimal Holder exponent in the Wasserstein distance on measures.In the second chapter, we focus on the eigenvectors of the one-dimensional discrete random Schrodinger operator. This is the Hamiltonian operator on the lattice of integers given by the discrete Laplacian plus an independent, identically distributed delta potential at each point. We restrict this operator to a finite box, pick an eigenvector uniformly at random and characterize the scaling limit as we take the size of the box to infinity. We show that the envelope of this random eigenvector converges weakly to an exponential Brownian martingale. Our analysis uses the well known transfer matrix formulation of the spectral problem; the spectral information is encapsulated in a process of products of independent, identically distributed two by two random matrices. The limiting diffusion for this product process was developed in (Kritchevski, Valko, Virag - 2011) to study the local eigenvalue point process. Our work makes heavy use of that framework.
The Removal Property for Linear Configurations in Compact Abelian Groups
Keywords: compact abelian groups
homomorphisms of finite abelian groups
integer linear systems
regularity lemma
removal lemma

The combinatorial removal lemma states that, if a (hyper)graph K has not many copies of the fixed (hyper)graph H , then K can be made free of copies of H by removing a small set of (hyper)edges from K. In this thesis we show results for homomorphisms in finite abelian groups, and for integer linear systems over compact abelian groups that are analogous to the combinatorial removal lemma. The results state that, given some subsets Xi of the group, if there are not many solutions to the system Ax = 0, where the variables xi take values inXi, then there exist small subsets Xi' inside Xi such that there is no solution to the system Ax = 0 with xi in Xi \ Xi'. These results are shown by constructing an appropriate (hyper)graph that allows us to retrieve information on the elements to be removed from Xi using the set of (hyper)edges. These arithmetic removal lemmas extend the first removal lemma for groups proved by Green in 2005. They also present a comprehensive approach to results involving finding non-trivial linear configurations in dense sets. Examples of these types of results are SzemerĂŠdi's Theorem, which ensures the existence of arbitrarily long arithmetic progressions in sets of the integers with positive upper density, or its multidimensional version. The latter was first shown by Furstenberg and Katznelson in 1978 using ergodic theory and proves the existence of k-simplices in subsets containing a positive proportion of the integer lattice or rank k.
Aboriginal Education for Non-Aboriginal Learners: Engaging Teacher Candidates in an Immersive Cultural Experience
Keywords: Aboriginal education
Canadian identity
cultural immersion
experiential
Indigenous Knowledge
land-based

It is the expectation of this thesis that Aboriginal Education ought to be considered education for all learners, that is initiated, developed, facilitated and evaluated by Aboriginal people. In order to demonstrate this, this dissertation describes a weekend-long land-based Immersive Cultural Experience facilitated by two Anishinaabe Elders, involving six non-Aboriginal Teacher Candidates from the Ontario Institute for Studies in Education's Bachelor of Education program. The research was proposed and carried out respecting Indigenous Knowledge and the standards set out in the Ontario Federation of Indigenous Friendship Centres' Utility, Self-Voicing, Access, Inter-Relationality Research Framework. Experience was the principal method through which an expanded approach to Aboriginal Education was validated, however the main form of data collection for the Immersive Cultural Experience was twelve participant interviews. The analytical approach was interpretive and inductive, asking questions that related to experience, focusing on the improvement of professional teaching practice and ultimately how the participants perceived their experiences. The data outlined in this dissertation reflects the comments and reflections of the Teacher Candidates, drawn from a pre-experience interview, sharing circle that closed the Immersive Cultural Experience, debrief session in Toronto, post-experience interview, as well as correspondence. The interviews were structured to gather a range of information from reflection on Canadian identity, personal responsibility, spirituality, new styles of teaching and learning, and the utility of cultural immersion and experiential education. This dissertation contributes to theory development for Allyship and provides a best practices framework for intercultural engagement and experiential learning, outlining: a) knowing one's history; b) seeking local Knowledge Holders; c) understanding Aboriginal ethics protocols; d) collaborative planning; e) preparing participants; f) community-driven facilitation; g) debriefing the experience; and h) maintaining relationships. In following this framework, the participants were challenged to reflect on what they believed to be true about Aboriginal people, knowledges and cultures, and create a new understanding based on respect, engagement and relationship. The changes observed in the Teacher Candidates proved that the experience of being on the land, and learning directly from Aboriginal Elders has a significant impact on teachers' thinking about how to approach Aboriginal Education.
Functional Projections and Non-local Relations in Tongan Nominal Phrases
Keywords: Nominal Projection
Noun Phrase
Syntax
Tongan Language

Functional Projections and Non-Local Relations in Tongan Nominal PhrasesThis dissertation explores several phenomena within Tongan nominal expressions - interactions amongst determiners, demonstratives, and definiteness; the morphosyntax of pronouns and possessive constructions; and the interactions of nominal aspect with numerals, number, and classification. Several motifs emerge, particularly the distributed nature of classification and quantification within nominal expressions, and the underlying locality of superficially long-distance syntactic relations.Although Tongan has pre-nominal articles often called definite and indefinite, I show that these encode specificity and non-specificity. Definiteness is marked via an anaphoric demonstrative clitic, the Definite Accent (DA), in the right periphery. A diachronic connection between the DA and spatial demonstratives has previously been shown, yet they do not instantiate the same syntactic category. The DA is now a marker of anaphoric deixis, interpreted as definiteness. It is merged above D