VictorJuiz/thesis huggingface dataset:
Electrochemical Studies of Molten Salt Corrosion

Corrosion mechanisms of Fe-Ni and Fe-22Cr-Ni model alloys with varying Ni contents and Ni-22Cr model alloy were investigated in molten chloride salts at 350-700 °C, simulating the heat transfer circuits of molten salt reactors and thermal solar plants.This study revealed that corrosion properties in molten Cl salts depends on homologous temperatures, metallic solid-solution alloying effects, critical alloy compositions, and impurities. Dealloying of electrochemically reactive element(s) (Fe and/or Fe+Cr) was the dominant form of corrosion; fundamentals and mechanisms of dealloying, and mechanistic connections with aqueous dealloying were determined. It was discovered that at certain conditions, dealloying in molten salts obeys the same rules as the aqueous dealloying. At 350 °C, the dealloying mechanism is mediated by surface diffusion of the more-noble element (Ni) at the alloy/molten salt interface. The microporous dealloying morphology resembled that seen in aqueous systems (but much coarser). The dealloyed layer was a three-dimensional structure with core-shell ligaments; a Ni-rich shell surrounding a core with minor Fe (Fe+Cr), similar to Ag-Au systems in acidic media. At 350 °C, the fundamental parting limit (55-60 at.% of the less-noble element in aqueous solutions) decreased to 44 at.% due to the high surface mobility of elemental Ni. At 350 °C, the parting limit further decreased to a value of approximately 32 at.% Fe when elemental Ni from alloy surface was close to equilibrium with Ni2+ ions that were added to the molten salts, similar to brass in aqueous solutions. Between 500 °C and 700 °C, the dealloying morphology is an interconnected pore/ligament network; however, transitional morphologies evolved, and grain boundary dealloying was common. At 600 °C, bulk diffusion resulted in one-dimensional tunnel-like corrosion morphology ahead of the dealloyed layer. The associated dealloying threshold decreased to values close to 32 at.% and 22 at.% as the temperature rose to 600 °C and 700 °C, respectively. At high homologous temperatures, there is a strong influence of lattice diffusion of alloying elements. However, dealloying of Ni-based alloys in molten salts at up to 700 °C is consistent with percolation dissolution theory; this study revealed that the parting limit remains mostly geometric in nature.

Keywords: Dealloying
Electrochemistry
Molten salt corrosion
Molten salts
Ni-based alloys
Parting limit
Advisor: Newman, Roger
Development and Evaluation of a Wearable Vibrotactile Biofeedback System and a Gait Event Detection Algorithm to Improve Gait Symmetry of Individuals with Lower-limb Amputation

BACKGROUND: Individuals with lower-limb amputation (LLA) often exhibit gait asymmetry. Biomechanical biofeedback (BFB) systems can improve gait symmetry and overall mobility. However, effective ways of providing vibrotactile feedback, including system functionality and usability have yet to be investigated. Further, effective GED algorithms with low-computational demands are needed to improve performance, wearability, and portability of BFB systems. OBJECTIVE(S): Objective 1 consisted of developing and assessing a wearable BFB system, including multiple vibrotactile feedback strategies, as a clinical tool for improving temporal gait symmetry of LLA. System usability, workload, learning and immediate post-test retention effects were also explored. Objective 2 consisted of developing and evaluating a GED algorithm to accurately detect foot-strike and foot-off events at different walking speeds. METHODS: For objective 1, a systematic literature review investigated BFB systems in gait rehabilitation of LLA. Secondly, a wearable vibrotactile BFB system was developed and evaluated, targeting prosthetic stance/swing time ratio as a percentage of the gait cycle (ST%). Three unique vibrotactile feedback strategies were investigated to induce stance time asymmetries (SR) and changes in walking speed in able-bodied participants. Further, effects on spatiotemporal and kinematics gait parameters were assessed under concurrent, corrective, discrete vibrotactile feedback, targeting stance time symmetry ratio (STSR) of LLA. System usability was assessed with the System Usability Scale and workload with the NASA Task Load Index questionnaire. For objective 2, a GED algorithm (foot-strike and foot-off detection) was developed and assessed via metrics of specificity, sensitivity, and timing error in able-bodied participants walking at slow, self-selected, fast, and random speed. FINDINGS: For objective 1, all participants modulated/improved their gait symmetry (ST%, SR, STSR) using BFB. Gait speed and cadence decreased, and symmetry of kinematic parameters improved with BFB. Learning and immediate post-test retention effects were observed in spatiotemporal and kinematics parameters after BFB was withdrawn. System usability and workload were acceptable. For objective 2, the GED algorithm detected foot-strike and foot-off at various speeds with high sensitivity (94.32%), specificity (94.70%), and low latency (6.52 ± 22.37ms). SIGNIFICANCE: This study provides new insights into the development of gait training BFB systems and low-computational GED algorithms to improve gait symmetry of LLA.

Keywords: Biofeedback
Gait Rehabilitation
Lower-limb Amputation
Prosthetics
Vibrotactile Feedback
Wearable Systems
Advisor: Andrysek, Jan
At the Frontier of the Impossible: Reimagining the Legacies of György Kepes and the Center for Advanced Visual Studies

This dissertation is concerned with a group of artists associated with the Center for Advanced Visual Studies (CAVS) at MIT from the late 1960s to the early 1990s. The Center's founder, György Kepes, envisioned CAVS as a hub for artists to meet and collaborate with the school’s faculty of scientists and engineers, in the hopes that they might develop artworks that would make the novel physical paradigms offered by fields like quantum mechanics, relativistic physics, and emergent systems more accessible to their lay viewer’s “inner world." Previous critics and historians have often dismissed Kepes’s Center (as well as the broader, art-technology fad with which it is often associated) as the product of an ill-conceived—and ultimately short-lived—desire to apply technocratic principles and techniques to the arts. I propose, instead, that the Center’s artists were united in their belief that previous scientific paradigms had engendered damaging social, political, and ecological consequences and in their conviction that these biases were not a product of technoscientific advancement in itself, but a direct reflection of the modern Western bias for sciences that relied upon the division of the world into so many discrete parts and offered a false sense of control. By drawing attention to the many ways the Center’s artists enabled viewers to engage with the kinds of relational and indeterminate phenomena that otherwise evaded their notice, I aim to show how Kepes and the extended CAVS community attempted to alleviate the sense of alienation that pervaded Cold War American culture by undermining the technocratic logic at its heart.

Advisor: Cheetham, Mark
Party Strategies and Voter Behavior in Multi-national States: Electoral Competition in a Multi-dimensional Issue Space

This dissertation is about electoral competition in countries where the center-periphery dimension is salient alongside the traditional left-right dimension. The focus is on the strategic choices of ethno-regional parties in response to greater support for decentralization by their state-wide rivals. It focuses on 3 questions. 1) How do ethno-regional parties respond to their state -rivals’ efforts to co-opt their primary issue of regional autonomy? 2) Under what conditions and how much weight do voters attach to ethno-regional parties’ position on non-center-periphery issues? 3) What factors do ethno-regional parties have to consider when deciding which positions take on non-center-periphery issues. The data cover Western European countries and Canada over a period of close to thirty years, from the early 1990s to 2019. The dissertation tests the effect of greater support for regional autonomy by state-wide parties on the strategic behavior of ethno-regional parties and the response of voters to greater party convergence on the issue of regional autonomy. It then focuses on the Scottish National Party and the Bloc Quebecois. Qualitative data, panel data, and evidence from election studies are used to show that positioning on left-right ideological issues is crucial to the electoral fortunes of these ethno-regional parties. Finally, it uses simulations based on hypothetical party positions and voter preferences to explain the strategic constraints ethno-regional parties and their statewide rivals face when deciding where to position in a multidimensional issue space. The project advances our understanding of political behavior in multi-national states, electoral competition in multi-dimensional issue spaces, and the research on niche parties.

Advisor: Nevitte, Neil
Investigating the Wellbeing of Teachers: A Self Study

Over the last decades, educational research has given considerable attention to teachers’ burnout. Owing to its negative personal, organizational, and social impacts (e.g., physical and mental ill health, decreased work performance, attrition, turnover), intervention and prevention efforts have consequently been employed to minimize the effects of this syndrome. As teaching-specific stressors are mainly related to the socio-emotional domain, interventions targeting social and emotional learning (SEL) for teachers have been seen to increase in recent years. Mindfulness-based interventions have proven to be successful in reducing teacher stress while improving teachers’ social-emotional competencies. The purpose of this self-study was two-fold. First, the researcher examined the contributing factors leading to her emotional exhaustion and eventual burnout. A typical burnout cycle was evidenced due to both external and internal factors, specifically, the researcher’s perfectionistic tendencies and underdeveloped emotional coping mechanisms. The second part of the research examined the impact of mindfulness practice on the researcher’s wellbeing, including her participation in a mindfulness-based intervention, Teachers on the RISE (TOTR). Findings showed that mindfulness-practices a) promote increased awareness (of self and others) b) improve one’s ability to respond c) improved compassion (for self and others) d) promote responsible decision-making e) improve esteem for the self f) improve self-care, wellbeing, and growth g) impact teacher performance h) impact students i) impact student-teacher relationships j) impact teacher practices k) build connections and community. Discussion included connections to the relevant literature, the researcher’s personal reflections as well as implications for future research.

Keywords: mindfulness
self-study
social-emotional competencies
teacher wellbeing
teacher wellness
Advisor: Kosnik, Clare
Putting “the Other Maine” on the Map: Language Variation, Local Affiliation, and Co-occurrence in Aroostook County English

This dissertation examines Aroostook County English, an understudied variety spoken at the border of Northern Maine (USA) and Western New Brunswick (Canada). The analysis is based on a socially stratified corpus of sociolinguistic interviews with 30 locals and word list data from the same individuals. The project has two goals: First, to establish how the variety of English in this area fits into the surrounding dialect regions, and second, to determine whether speakers who closely align themselves with local values share a similar sociolect. Examining eight phonological features that have traditionally been used to distinguish different varieties of English in the area (namely, rhoticity, the LOT-THOUGHT merger, the NORTH-FORCE merger, the MARY-MARRY-MERRY merger, broad-a in BATH, intrusive-r, fronted START, and fronted PALM, see Stanford, 2019), I find that Aroostook County English includes a mix of features from Eastern New England and Atlantic Canada, suggesting it is a transition zone (see Chambers & Trudgill, 1998). It also challenges previous accounts of linguistic homogeneity within Northern Maine (Kurath, 1939: 17), demonstrating that there is more linguistic variation within the state than previously assumed. Focusing on three morphosyntactic variables (was leveling, demonstrative them, and preterite come), this dissertation finds that speakers with high local affiliation tend to have more nonstandard variants in their repertoire. However, speakers with ties to the education system do not conform to this pattern and usage rates vary widely. This suggests that the combination of nonstandard was, them, and come indexes high local affiliation for some speakers, but their absence does not imply the opposite. I conclude that the combination of nonstandard variants has a different social meaning from their absence, similar to the way that variants of the same variable can have non-complementary connotations (Campbell-Kibler, 2011). Taken together, these findings highlight the usefulness of linguistic data from small, remote communities for understanding the development of the English language and the relevance of identity-based factors for understanding patterns of language variation and change (see Hazen 2002; Tagliamonte, 2006c, 2013, 2017).

Advisor: Tagliamonte, Sali A
Re-Drawing Perspectives on and of Contemporary Saudiyyat: Using Suwalif by and for the Saudi Women

In recent decades, Saudi Arabia has witnessed the implementation of various sociopolitical changes in terms of the direction and management of its society. In this dynamic environment, women in Saudi Arabia are being largely impacted by their navigation within the private and public spaces. This dissertation brings forth the lived experiences of ten, educated, middle-class women in Saudi Arabia to look at how they negotiate their subjectivities; the strategies they use to influence their subject positions within family and society; and how the women reconcile their subjectivities as in-between in an overall process of negotiation. Subjectivity creates a fluidity where there is continuous acting and shifting, and allows for insight into how these women are affected by their interactions. This work is informed by the interpretivist and poststructuralist theoretical frameworks and introduces a narrative methodology of suwalif as a social practice of speaking, retelling and uttering lived experiences of and through these ten saudiyyat. The methodology focuses on bringing their voices away from any overused biases and analyzes the data through narrative research using my expertise as an ‘insider’ to share their suwalif in a culturally sensitive manner. The women bring forth their subjectivities and lived experiences to provoke an uneasiness in conversations around gender that create a space for questioning normative discourses of power.

Keywords: Contemporary
Discourse
Narrative
Saudi Arabia
Saudi women
Subjectivity
Advisor: Sykes, Heather HS
Optimal Transport, Congested Transport, and Wasserstein Generative Adversarial Networks

Generative Adversarial Networks (GANs) are a method for producing a distribution $\mu$ that one can sample which approximates a distribution $\nu$ of real data. Wasserstein GANs with Gradient Penalty (WGAN-GP) [GAA+17] were designed to update $\mu$ by computing and then minimizing the Wasserstein 1 distance between $\mu$ and $\nu$. In the first part of this thesis we show that in fact, WGAN-GP do not compute this distance. Instead, they compute the minimum of a different optimal transport problem, the so-called congested transport [CJS08]. We then use this result to offer explanations of the observed performance of WGAN-GP. Our discovery also elucidates the role of the gradient penalty sampling strategy in WGAN-GP, and we show that by modifying this distribution one can ameliorate a transient form of mode collapse in the optimal mass flows. The second part of this thesis presents new algorithms for generative modelling based on insights from optimal transport theory. The basic idea is to transform one distribution into another via iterated descent with an adaptive step size on learned Kantorovich potentials computed with WGAN-GP. We provide an initial convergence theory for this technique, as well as guarantees of convergence for an extension of this procedure when the target distribution is supported on a submanifold of Euclidean space with codimension at least two. As a proof of concept, we demonstrate via experiments that this provides a flexible and effective approach for several generative modelling problems, including image generation, translation, and denoising. Further analysis of this algorithm reveals that it is connected to image restoration techniques via learned regularizers, which generalize the classical total variation denoising technique of Rudin-Osher-Fatemi (ROF) [ROF92]. We provide analogues of the results of [Mey01] on ROF to the learned regularizer setting. Leveraging this connection, we provide optimal transport versions of the iterated denoising [AXR+15] and multiscale image decompositions [TNV04] associated with ROF.

Keywords: Congested Transport
Optimal Transport
Variational Image Restoration
Wasserstein Generative Adversarial Networks
Advisor: Nachman, Adrian
Steps Toward Multichromatic Optogenetic Control with Cyanobacteriochromes

Optogenetic tools offer spatial and temporal control of biological processes. Photoswitchable proteins that change conformation upon exposure to light are the core components of optogenetic tools. Current tools rely mostly on photoswitchable proteins that respond to blue light, and some use red light. To enable orthogonal, multicolor control of multiple biological processes, tools must be developed that respond to other colors of light. Cyanobacteriochromes, photoswitchable proteins from cyanobacteria, respond to a wide range of wavelengths from the UV to the near infra-red. This thesis explores the applicability and utility of cyanobacteriochromes as new core components of optogenetic tools. New light inducible dimer pairs from these photoswitchable proteins are developed via directed evolution approaches, permitting orthogonal control of biological processes with red-, green-, and blue-light.

Advisor: Woolley, G. Andrew
Civic Participation and Democratic Experience: Civic Tech in Toronto

This thesis examines intersections of civic participation and technology development in Toronto, Canada. In particular, I examine processes that configure civic participation by focussing on the way that people enrol and are enrolled by technology oriented toward the pursuit of public goods, a practice known by those involved as ‘civic tech’. Using ethnographic and action research methods, I examine processes of design and participation at multiple sites, characterised by differing levels of state and civilian involvement. In the first article, I explore the 2018-2020 corporate-run engagementprocess case of the Sidewalk Toronto smart city development, arguing that while certainly robust in scope, the process marginalised participant contributions by maintaining boundaries around key normative dimensions of the proposed smart city, especially around the governance of space, data, and other infrastructures. In the second and third article, I shift focus to Civic Tech Toronto (CTTO), a volunteer-led community group that, since 2015, has gathered civilians and public servants together at weekly hacknights, where they listen to speakers and experiment with technology projects addressing civic issues. The second article examines the governance and production of CTTO, exploring the applicability of commons based peer production language to the community and arguing that its main role as a technology itself is to produce relationships and experiences of community, rather than technological artefacts. Finally, the third article explores how CTTOs activities act as a contact zone that brings civilians and the state closer together in informal relationships. By prioritising social and self-directed cooperation, CTTO moves beyond the typical transactional nature of civic engagement (i.e. one that configures people as ‘users’ of the state or sees them as providers of informational ‘feedback’), and equips both civilians and public servants with the skills they need to interact more productively. Collectively, this research advances our understanding of the value of civic tech not only in terms of the artefacts it produces, but in the infrastructuring work it does: civic tech maintains civic commons that cultivate democratic subjects and creates spaces that ultimately help build trusting relationships between publics and public servants.

Keywords: citizenship
civic technology
democratic participation
sidewalk toronto
systems thinking
Advisor: Becker, Christoph
The Book of the Judgements of Calatarama: A Case Study of a Medieval Spanish Geomancy

Manuscript MS 5-2-27 of the Biblioteca Colombina at the Cathedral of Seville, Spain, contains a single text, the Libro de los juysios de calatarama, the “Book of the judgements of calatarama.” Identified as a translation of a Hebrew translation of an Arabic original, the Libro de los juysios de calatarama is an instructional manual in the Castilian vernacular for a type of divination known as geomancy. Geomancy appears to have originated in the Islamic world and was later adopted in the medieval west via Latin and later vernacular translations. This study of the Libro de los juysios de calatarama contributes to research into this less well-known field of medieval divination through a close analysis of the geomantic practice the text describes. In addition, the incipit of this text identifies it as having been translated by a rabbi at the request of a bishop, and thus the Libro de los juysios de calatarama is not only a reflection of medieval geomancy but also contributes to the understanding of intercultural exchange amongst Muslims, Christians, and Jews in medieval Spain. The majority of the evidence for such intercultural exchange tends to come from the literate, scholarly milieu of medieval Spain. However, given that evidence would suggest that geomancy existed in some form at a popular level, the Libro de los juysios de calatarama provides insight into intercultural exchange at a popular level in medieval Spain. By placing the Libro de los juysios de calatarama within the historical context of both medieval geomancy and medieval Spain, this analysis of the text contributes to the research both on geomancy in particular, and divination in general, as well as to the discussion of multiculturalism in medieval Spain.

Keywords: Divination
Geomancy
Medieval Spain
Advisor: Everett, Nicholas