VictorJuiz/thesis huggingface dataset:
Tailoring the Species Transport in Polymer Electrolyte Membrane Fuel Cells for Improved Performance
Keywords: Electrochemical system design
Polymer electrolyte membrane fuel cell
Species transport optimization
Sustainable energy
Synchrotron imaging

Understanding the species transport in polymer electrolyte membrane (PEM) fuel cells is critical for improving the cell performance. Poor performance stems from inefficient species transport. Particularly, excess accumulation of liquid water in the gas diffusion layer (GDL) substrate hinders transport of the reactant gases; the membrane dehydrates with increasing current density, leading to ohmic losses; the catalyst carbon support corrodes in the presence of water and high local potentials. In this thesis, these phenomena were investigated for improving the cell performance. In addition, imaging procedures for synchrotron radiography were improved to accurately visualize the water evolution in PEM fuel cells. The roles of undesired secondary scattering and harmonic photons on imaging accuracy were numerically determined. Both the secondary scattering and harmonic components increased with increasing water thickness, leading to a decrease in the calibrated attenuation coefficient and subsequent decrease in imaging accuracy. Next, the GDL substrate land and channel region contributions to oxygen transport resistance were resolved. Both the substrate oxygen transport resistance and the mass transport resistance of the fuel cell were more sensitive to the local saturation in the substrate channel region than that in the substrate land region. In a related study, membrane dehydration under high relative humidities (above 70%) caused significant membrane shrinkage. Via experimental visualization and performance testing techniques, the dehydration was attributed to increases in the local temperature. Lastly, a novel diagnostic method was developed to measure the electrode performance for the real-time detection of carbon corrosion in dead-ended anode operation. The accumulation of nitrogen in the corroded cathode led to sudden increases in cathode polarization resistance, and this performance characteristic was identified as a new indicator for a corroded cathode. The main findings in this thesis advance the understanding of species transport as a basis for developing next-generation high-performance PEM fuel cells.
An Investigation into Mathematics for Undergraduate Engineering Education to Improve Student Competence in Important Mathematics Skills
Keywords: Engineering Education
Improving Competence
Mathematics Education
Metacognition
Motivation
Pedagogy

Several convictions premise this work. First, that mathematics is a crucial part of the toolset required by engineers if they are to practice responsibly; how else can one predict consequences of innovative engineering actions and designs? Also, that faculty perceive that students often find mathematics neither helpful nor essential, but instead find it frustrating, painful and discouraging. This work shows that this perception of a gap is not only valid and widespread within engineering, and across the various departments, but is widespread for different backgrounds and across various mathematics subjects. Given that elucidating the importance of mathematics is crucial to engineering, is there an issue with student competence in mathematics? In seeking to answer this question, this endeavour is intended to be climactic, because it is not merely knowing that mathematics is essential, knowing if there is a struggle is imperative, which helps understand if a change is needed to teach mathematics to engineers and to open the doors for future discourse. This project uses a mixed-methods study, explicitly using a post-positivist, pragmatic research paradigm completed through an explanatory sequential framework. The 2017-2018 academic year was used to collect data. The findings suggest faculty agree that mathematics plays an important role in engineering, that students' need to be better at general and specific mathematics skills, and that revisiting how one teaches mathematics to engineering students is required. In an effort to provide students with a better learning environment, it is helpful to revisit the engineering mathematics curriculum. Engineering practice is dynamic, technologies change, even becoming obsolete. The same should be valid for how to impart the curriculum to students, which should encourage modernizing teaching methods to improve knowledge transfer for student success. Through the lenses of pedagogy, instructional design, and cognitive psychology offer opportunities to improve the existing curriculum as it relates to student achievement. Thus, one of the predominant outcomes of this project is to provide a study of best practices for mathematics education for engineering students, along with the perceptions of faculty about these same practices.
Fabrication of Thermal Management Devices using Thermal Spray Technology
Keywords: Analytical modelling
Heat transfer
Thermal management devices
Thermal spraying

Thermal spray coating processes have been employed to create a composite finned heat sink and a flat vapor chamber featuring structured porous coating wicks, for thermal management application. Three composite heat sinks in the shape of a disk, a cylinder, and a cylinder with vertically projecting fins were made by applying a thin (0.4 – 0.7 mm) zinc layer onto ABS polymer cores using wire-arc spraying. An analytical model of the heat conduction in an annular fin was developed, and the model was found to agree well with the temperature distribution along the disk-shaped heat sink measured using an infra-red camera. The calculated temperatures at the base of the heat sink also agreed with measured values as heater power was varied. The model was used to examine the effect of fin radius and coating thickness on fin efficiency. A flat copper vapor chamber was fabricated by depositing structured porous coatings on the evaporator using flame spraying. The porous copper coatings act as wicks of the vapor chamber for liquid transport due to the capillary effect. Channels to enhance liquid flow were made in the porous copper coatings. Coated samples were made with porosity varying from 2 to 44 %, and groove width ranging from 0.16 to 0.53 mm. The capillary performance of the coatings was evaluated experimentally by measuring the rate-of-rise of ethanol in the coatings. The capillary performance parameter ∆Pcap∙k increases with coating porosity and channel size. The rate of ethanol evaporation on the vertically placed coated samples was investigated. Increasing the effective porosity of the coating enhanced the maximum mass flow rate through it. The flat vapor chamber charged with water operated successfully, and in the heat spreader test it achieved an overall thermal resistance of 0.13 K/W at a maximum heating power of 162 W. The structured porous wicks demonstrated a greater capillary performance than sintered powder wicks, which extends the heat flux up to 140 W/cm2 without reaching the capillary limit. The effective radial conductivity ranges from 1200 to 7000 W/m∙K, depending on the applied power.
Leveraging Subtle Verbalization and Speech Patterns to Help Evaluators Identify Usability Problem Encounters in Concurrent Think-aloud Sessions
Keywords: human-computer interaction
machine learning
think aloud
usability problems
verbalization and speech features
visualization

Think-aloud protocols are a highly valued usability testing method for identifying usability problems. Despite the value of conducting think-aloud usability test sessions, analyzing think-aloud sessions is often arduous. Consequently, previous research has urged the community to develop methods to support fast-paced analysis. Inspired by the research that shows subtle patterns in how we interact with other people reveal our attitudes toward them, I study subtle patterns in users’ verbalizations and speech when they encounter problems in think-aloud sessions and further leverage these patterns to support the analysis of think-aloud sessions. In this dissertation, I first survey user experience (UX) practitioners around the world to understand their practices and challenges around using think-aloud protocols. I then design and conduct three studies, each addressing the limitations of the previous one, to identify and validate the subtle patterns in users’ verbalization and speech features that tend to occur when they encounter usability problems. Informed by the findings from the studies, I take the first step to designing computational methods that leverage these subtle patterns and the power of machine learning (ML) to detect the usability problem encounters. To help UX practitioners leverage ML-inferred usability problem encounters, I design and evaluate an intelligent visual analytics tool that present UX practitioners with a timeline visualization of ML-inferred problem encounters and ML’s input features among other functions. Experimental results demonstrate that ML-inferred problem encounters help UX practitioners consider problems that they might have overlooked and therefore identify more usability problems. Moreover, I offer insights into how UX practitioners leverage and perceive ML-inferred problem encounters and ML’s input features in their analysis and their session review strategies (i.e., how they play, pause, rewind the recorded sessions). Finally, I highlight the promising directions to further forge a better symbiosis relationship between UX practitioners and machine intelligence when analyzing recorded think-aloud sessions.
Annihilation of Cohomology over Gorenstein Rings
Keywords: cohomology annihilator
commutative algebra
maximal cohen-macaulay modules
representation theory
stable annihilator
tate cohomology

One of the fundamental links between geometry and homological algebra is that smooth affine schemes have coordinate rings of finite global dimension. The roots of this link goes back to Hilbert’s syzygy theorem and later to the work of Auslander and Buchsbaum and also of Serre and Zariski. Having finite global dimension can be characterized by Ext-modules. Namely, a ring R has finite global dimension if and only if there is a natural number n such that Extn R(M, N) = 0 for every pair M, N of R-modules. Hence, in the singular case, there are nonzero Ext-modules for arbitrarily large n. So, for a commutative Noetherian ring R, one is interested in the cohomology annihilator ideal which measures how far the ring is from having finite global dimension. The main theme of this thesis is to study the cohomology annihilator ideal over Gorenstein rings. Over Gorenstein rings, the cohomology annihilator ideal can be seen as the annihilator of the stable category of maximal Cohen-Macaulay modules. The first main result concerns the cohomology annihilator ideal of a complete local coordinate ring of a reduced algebraic plane curve singularity. We show that the cohomology annihilator ideal coincides with the conductor ideal in this case. We use this to investigate the relation between the Jacobian ideal and the cohomology annihilator ideal. The second main result shows that if the Krull dimension of R is at most 2, then the cohomology annihilator ideal is equal to the stable annihilator ideal of a non-singular R-order. We also give several generalizations of this which brings us to the second part and the closing section of this thesis. Namely, we study the dominant dimension of orders over Cohen-Macaulay rings. We provide examples and prove results on tilting modules for orders with positive dominant dimension
Assessing Changes in Visual Attention Secondary to Mild Hearing Loss in Aging through the Study of Response Time and Event-related Potentials
Keywords: Age-related hearing loss
Automatic Response Preparation
ERP
Foreperiod
Reaction Time
Strategic Response Preparation

This set of studies was designed to evaluate the association between hearing loss in aging and extra-auditory cognitive decline by assessing younger normal-hearing adults (YN), and older adults with either age-typical hearing (ONHA) or mild hearing loss (OHL). A visual reaction time (RT) paradigm involving four tasks with hierarchically-varied attentional demands was administered with EEG. There were three main objectives. The first objective (Study 1) was to assess the effect of hearing loss on: i) RT, ii) error commission and recovery, and iii) strategic versus automatic response preparation. The OHL group demonstrated general slowing on the simplest tasks, less efficient error recovery, and difficulties with automatic response preparation, compared to both other groups. The second objective (Study 2) was to study the YN group’s EEG results using the N1 to identify the influence of task context on early attention-sensory evaluation and the scalp distribution of the P3 as a marker of attention guiding (anterior) and stimulus categorization and response preparation (posterior). The latency and amplitude of the N1, the posterior-anterior P3 amplitude distribution, and neural activity modeling supported an increasing reliance on anterior attentional processes as tasks required either an enhancement or suppression of attention for stimulus discrimination. The third objective (Study 3) was to compare the EEG data between the ONHA and OHL groups using the metrics used in Study 2. The OHL group had a longer N1 latency that correlated with their speeded visual executive test scores, longer anterior P3 latencies, hemispheric symmetry of N1 amplitudes indicative of less efficient top-down control, and anterior P3 amplitudes that indexed over-processing of unnecessary information. Latency and amplitude of the posterior P3 were comparable between both older groups. In sum, cognitively-intact older adults with mild hearing loss demonstrated differences in: i) response time on the simplest tasks and automatic preparatory processes compared to younger adults and older adults with age-typical hearing; and ii) ERP indices of sensory-cognition integration and early attentional guiding compared to older adults with age-typical hearing. These findings may represent mechanisms involving either localized differences in subcortical regions of sensory-motor-cognitive integration and/or disruptions of functional networks.
The EPP across Languages
Keywords: comparative linguistics
EPP
subjects
syntax
typology

The Extended Projection Principle (EPP) formalizes the requirement for a subject in every clause. In this dissertation, I develop a typology of EPP effects based on a sample of typologically, geographically, and genetically diverse languages. I define the EPP as the obligatory movement of some element into the inflectional domain, and argue that the EPP can vary in three different dimensions: (i) whether an argument or a predicate is the goal of the EPP-probe, (ii) whether the goal is a head or a phrase, and (iii) whether a larger constituent is pied-piped. I demonstrate that these three dimensions interact to create a total of seven different attested EPP types across languages. I demonstrate that intra-linguistic alternations in EPP type are attested, which provide evidence that these types are functionally equivalent on some level. I also present the hypothesis that the EPP type of a language should be predictable based on other properties of the language. As such, I discuss several properties that co-occur with particular EPP types cross-linguistically. For example, predicate-EPP languages pattern together by having a high, defective T head, which results in a set of shared properties, including: (i) a lack of non-finite clauses, (ii) high or preverbal tense marking, (iii) a T merged with C, and (iv) defective definiteness marking. On the other hand, I show that the null subject type of a language does not correlate with EPP type. Finally, I also propose two different functional purposes for the EPP. First, I propose that the EPP has an anchoring function, linking the utterance to the world by raising an element marked with an index to a position of prominence. I present the hypothesis that all operations within the inflectional domain have an anchoring function. Second, I argue that the dichotomy between predicate and argument EPP languages can be explained if we understand the EPP as a high predication operation, which raises either the predicate or the argument to a position which c-commands the other. I then propose that all anchoring operations, including the EPP, have dual functions, thus incorporating the two functions of the EPP.
Writing the Young Diasporic Muslim Female: A Study in Creating Culturally Sustaining Narratives
Keywords: Autoethnography
Creative Analytic Practice
Critical Literacy
Culturally Sustaining Pedagogy
Decolonial Praxis of Narrative
Young Adult Literature

This doctoral dissertation begins with the central research question: How might the act of writing a creative literary text both capture the lived experience of an adolescent diasporic Muslim female and critique the social conditions that aggravate her marginalization? To answer it, I wrote THE LAST STORY, a young adult novel, with a female diasporic main character of Muslim origin living in a speculative and divided world. As I wrote, I kept thorough journal entries about the creative, critical choices being made. Accordingly, while the novel itself does not make up the dissertation, it is the main data source in what is, essentially, an autoethnographic (Ellis Bocher, 2000) project. Because I have composed a reflexive written piece about the process of writing and the context in which it happened, the result of this research project in the form of this thesis is what Richardson (2000) terms “a writing story.” My theoretical framework encompasses philosophies of narrative and utilizes Bricolage (Kincheloe, 2005) as a guiding principle. Creative Analytical Practices (CAP) (Richardson, 1999) autoethnography and Cooper and White’s (2012) five contexts of qualitative inquiry serve as conceptual framework to methodologically structure the thesis. Stimulus for the work is guided by the development of a social imagination within the creative writing field, attempting to do so by taking up what Greene (2000) describes as “the capacity to invent visions of what should be and what might be in our deficient society” (p. 5). It hopes to contribute to the discourse around the inclusion of culturally sustaining materials (Ladson-Billings, 2014; Paris, 2012) in the English language and literature classroom through the Decolonizing Praxis of Narrative (DPN) method, which I developed from the writing and inquiry process.
On Nonadiabatic Dynamical Simulations near Conical Intersections via Surface Hopping Methods
Keywords: conical intersection
diagonal Born-Oppenheimer corrections
geometric phase
surface hopping

Many chemical processes involve nuclear dynamics on multiple potential energy surfaces. These often involve conical intersections, which cause nonadiabatic couplings and diagonal Born-Oppenheimer corrections to diverge and thus a complete breakdown of the Born-Oppenheimer approximation. Furthermore, conical intersections make electronic and nuclear wavefunctions double-valued, requiring proper consideration of the boundary conditions of molecular wavefunctions. In this work we rationalize why the fewest switches surface hopping method, despite not involving nuclear wavefunctions nor any consideration for diagonal Born-Oppenheimer corrections, can approximate the exact quantum dynamics of conical intersection-induced interstate crossings. In addition, we identify regimes when it is beneficial to include diagonal Born-Oppenheimer corrections in surface hopping dynamics through the phase-space formalism. Lastly, we consider the use of neural networks within the surface hopping framework, to approximate the nonadiabatic dynamics of fewest switches surface hopping by emulating its hopping criterion. We show that a properly trained “neural network-induced surface hopping” algorithm can approximately simulate populations dynamics without the need to propagate electronic wavefunctions.
Advances in Incomplete Data Methods for Statistical Genetics
Keywords: Microbiome data
Missing data
Statistical genetics
Two-phase studies
X-chromosome

Handling incomplete or missing data is a common aspect of modern statistical methods. In this thesis, I focus on novel solutions for current problems pertaining to statistical genetics that can be framed in the context of incomplete data. In particular, three methods are proposed that are underpinned by the EM algorithm, arguably the most common yet powerful approach to make statistical inference in the presence of incomplete data. First, motivated by developments in metagenomic sequencing data and the apparent systematic exclusion of the X-chromosome in genetic studies, I propose a finite mixture regression model (FMM) that infers association between a genetic variant in the X-chromosome and an operational taxonomic unit. The proposed FMM accounts for complex biological mechanisms governing the X-chromosome, namely X-chromosome inactivation (XCI), escape of XCI, and skewed or non-random XCI by introducing an latent indicator variable. Second, I investigate two-phase sampling designs in post-genome-wide association studies (GWASs), which can be a cost-effective strategy to infer association between missing-by-design sequencing data and a trait of interest. In phase 1, given a GWAS-identified genetic region, a subsample is selected for which expensive targeted-sequence data are collected using outcome measures and auxiliary covariates to inform the sampling. Phase 2 consists of performing inference using combined phase 1 2 data. In particular, I develop semi-parametric maximum likelihood for analysis and examine heuristic allocations to select the phase 2 subsample. Lastly, derived from the second project, I propose two strategies that aim to optimally select subjects for sequencing when the subsample size is fixed due to budget constraints. These strategies aim to minimize features of the variance-covariance matrix based on predefined optimality criteria found in previous literature and common to experimental design. The proposed strategies implement such minimization via (1) Lagrange multipliers and (2) a genetic algorithm. In all cases, the proposed methods are evaluated through comprehensive simulation studies. In addition, I illustrate their usage in real genetic studies or realistic synthetic data in absence thereof. Overall, the methods perform satisfactorily, moreover, these findings can serve as the basis of further research.