VictorJuiz/thesis huggingface dataset:
Low Energy Helium Ion Implantation and Application of a High Energy Ion Implantation Tool to Comprehensively Investigate the High Helium Dose Effects

Ion beam implantations are widely performed to understand the effects of radiation damage such as He bubbles on nuclear structural materials. This work investigates near-surface changes caused by low energy ion implantations, as well as deep ion implantations leading to bulk-property changes./nThe near-surface interactions of low energy (25-60 keV) He ions with Ti and Cu targets were investigated by atomic force microscopy (AFM), nanoindentation, Transmission Electron Microscopy (TEM), and Positron Annihilation Spectroscopy (PAS). AFM showed a linear increase in swelling with respect to dose for all materials, and blistering onset doses of 5 × 1017 ions/cm2, 8 × 1017 ions/cm2, and 1 × 1018 ions/cm2 for Ti(0001), Ti(10¯10), and Cu(100), respectively. Cavities on the order of 287 nm diameter were observed in Cu, and surface blisters formed from the intersection of these large cavities. He bubbles observed in Ti were around 1 nm diameter, and surface blisters formed from inter-bubble fracture. PAS showed an increase in defect concentration with respect to depth and dose, agreeing well with AFM and TEM results. An additional PAS measurement determined that shock loading can lead to a decrease in vacancy concentration in a pre-implanted material./nTo fill the gap between widely available low energy ion implantations and difficult-to-achieve bulk implantations, this work aimed to establish the use of the 88-Inch Cyclotron for nuclear materials studies. Four HT-9 SS-J-geometry tensile specimens were irradiated with high energy (19-25 MeV) deuterons at the 88-Inch Cyclotron to doses of approximately 0.2 dpa prior to small scale tensile testing. The results from this study showed irradiation hardening characterized by black dot irradiation defects, and the tensile test results were in agreement with the available data. To support future deep ion implantation campaigns, a novel ion beam degrader capable of uniformly implanting bulk-scale materials with He ions was designed.

Advisor: Hosemann, Peter
The Transport of Cosmic Rays and Their Impact on the Thermal Evolution of Galaxy Halos and Clusters

Although negligible by number density, relativistic cosmic rays (CRs) are an energetically important component of the plasmas filling the inter-stellar media and halos of galaxies, and the cores of galaxy clusters. As a result, CRs can have a large impact on their host systems, for example by heating diffuse gas or by driving galactic winds. This "CR feedback" is a strong function of how CRs are transported across galactic environments. Despite elaborate efforts to constrain it, the transport of galactic CRs remains uncertain, which makes CR feedback one of the biggest unsolved puzzles in galaxy evolution. The goal of this thesis has been two-fold. A large portion of this work uses theoretically favoured models of CR transport to study how CRs affect the dilute gases in galactic halos and in the intra-cluster medium of galaxy clusters. It is shown that CRs can significantly affect wave propagation by driving rapidly growing fluid instabilities, which has significant implications for the thermal evolution of these systems. This work is complemented by a study that compares existing micro-physical theories of CR transport with detailed measurements of spectra of galactic CRs in the solar neighbourhood. It reveals that existing CR transport models are generally not in good agreement with the data and provides speculations on how this discrepancy could be remedied.

Advisor: Quataert, Eliot
Pre-training Agents for Design Optimization and Control

In recent years, we have seen tremendous benefits from pre-training neural networks to learn representations that are transferable to unseen downstream tasks in both vision and NLP. However, this paradigm of learning has not been much explored for decision making such as design optimization or control. In this thesis, we outline two problem settings that could benefit from pre-training in the context of decision making. First, we describe a setting for automated design optimization, in particular circuit design optimization, where prior domain-specific data can be used to effectively improve the sample efficiency of model-based optimization methods. This thesis presents novel ideas along with empirical and theoretical analysis on how to boost sample efficiency of model-based evolutionary algorithms as well as Bayesian optimization methods. In the second problem setting, we will discuss how we can leverage unsupervised pre-training from large task-agnostic datasets to extract behavioral representations and do few-shot imitation learning. We find that pre-training agents to extract skills is a practical direction for preparing them for few-shot imitation when example demonstrations from the new task are scarce.

Advisor: Stojanovic, Vladimir
Abbeel, Pieter
Adaptive Remapping for High-Order Particle-in-Cell Methods

We present an analytic framework for understanding the errors associated with deposition in particle-in-cell methods applied to kinetics problems in one configuration space dimension. We begin by considering a one-dimensional advection model problem. Results of the analysis includes a O(1) error, also referred to as a barrier error, that is dependent on the deformation gradient of the particle locations. The presence of this barrier is confirmed by numerical experiments. The techniques developed in the analysis of the one-dimensional advection model problem are used to analyze a deposition model problem in the context of kinetics. This analysis shows an error that is similar to the error that arose in the one-dimensional advection model problem but is dependent only on the configuration space deformation gradient of the particle locations. A set of ODEs are derived for the Vlasov-Poisson system that can be used to compute the configuration space deformation gradient without explicit knowledge of particle neighbors. This allows for computation of the O(1) error at each time-step. Remapping is then introduced to control this error. Numerical experiments confirm that remapping when the O(1) error is comparable to the other errors inherent in the simulation reduces the "particle noise” phenomena that plagues many PIC methods and maintains the high-order convergence. With a fourth-order kernel this leads to an overall reduction in the number of remaps compared to a forward semi-Lagrangian method that remaps every few time steps. We also implement adaptive-in-time-and-space (local) remapping where only a portion of the phase-space is remapped and the O(1) error along with the value of the distribution serve as an implicit boundary between the remapped and non-remapped regions. The adaptive-in-time and locally remapped PIC methods are then applied to the Dory-Guest-Harris instability which, unlike the other test problems considered, has two velocity space dimensions.

Advisor: Colella, Phillip
Prefrontal and Subcortical Dynamics of Value-Based Decision Making

The orbitofrontal cortex (OFC) is a region critical to value-based decision making. Previous work from our lab showed that the neural population in OFC flip-flops between representing the available options while animals are deliberating between them. While these value dynamics were predictive of subjects' choices, they did not build toward the chosen option preceding the choice. We hypothesised that a downstream region with connections to both OFC and motor regions, for example the anterior cingulate cortex (ACC) or head of the caudate nucleus (CdN), may be integrating over these OFC value dynamics, leading to the choice. We recorded large neural populations simultaneously from OFC and each of these regions while two monkeys used a bidrectional lever to select between pairs of pictures, each associated with a unique probabilistic reward. In the ACC, we indeed observed a motor preparation signal that was influenced by OFC value dynamics on individual trials. However, in the CdN we observed a rapid choice direction signal, locked to the start of the trial instead of the motor response, that was independent of OFC value dynamics. Overall, our results are consistent with parallel, rather than serial, processing underlying value-based decision making.

Advisor: Wallis, Joni D
Sustainable and Inclusive Design Thinking

Design thinking has become increasingly popular in academic, professional, and colloquial communities as a means to address complex problems. In an era where responses to global issues, such as the climate crisis, may have long lasting impressions on the human condition, it is important that the methods for solving these problems are setting solid foundations for future generations. This dissertation investigates sustainable and inclusive factors within the design thinking process based on the premise that these are foundational elements of complex problem solving. Holistically this dissertation studies how design thinking participants perceive success and satisfaction in a design thinking experience. Also, this work includes a particular focus on one of the more tangible stages of the design thinking process -- prototyping -- and uncovers opportunities to improve sustainable practices through drawing insights about the current vulnerabilities in the life cycles of prototyping and making. Key insights from this dissertation include significant struggles at the beginning of the design thinking experiences compared to the end of design thinking experiences (see Chapter 2 and Chapter 3) and suggests that demographic background plays a significant role in how design thinking participants perceive success (see Chapter 2). Notable takeaways about sustainable design thinking practices involve how the lack of transparency in the manufacturing and distribution of needed materials and equipment make it difficult for decision makers to prioritize sustainable, and even social, factors. Instead, cost, availability, and quality remain driving factors for decision making. In addition, the driving purpose for small scale fabrication spaces (such as community, project execution, or skill building) was revealed as an influential factor in sustainable behaviors throughout all stages of the life cycles of small scale fabrication spaces. Overall, future work that aims to reinforce sustainable and inclusive practices in design thinking would benefit from investigating how demographic context and motivation influence perceived value of, and observed behaviors within, design thinking processes.

Advisor: Agogino, Alice M
Goucher-Lambert, Kosa
The Dialectical Curmudgeon: Afterlives of Hegel in German Literature and Political Thought

The Dialectical Curmudgeon: Afterlives of Hegel in German Literature and Political Thought asks how Germany’s most ambivalent intellectual tradition can serve as a resource for antiracist and feminist thought and action today. My dissertation begins with the observation of a peculiar consonance between, on one hand, the rise of a right-wing populism in the West that was codified with the election of Donald Trump and continues to threaten women, people of color and queer communities today, and on the other hand, the undercurrent of cultural conservatism running through the tradition of German literature and philosophy that can trace its intellectual lineage back to G.W.F. Hegel, who rejected modern values of democracy and women’s rights as short-sighted and insisted that our attempts to create a more equal society are doomed to failure unless we can see the big picture./nThe paradox of Hegel’s influence on our world is that a philosopher with a firmly established reputation for conservatism should have inspired modern history’s most consequential revolutionary thinkers, including but by no means limited to Karl Marx. My dissertation explains why philosophers and literary figures in the tradition of Hegel and Marx are often reflexively skeptical of the moral claims and political action of marginalized groups, dismissing the political centering of race and gender oppression as a distraction, if not counterproductive, and sometimes even adopting framings that align with racist and sexist cultural values./nI also show how this tradition has served and can still serve as a resource for struggles for social justice today. For example, chapter 3 examines the political disagreements between the theorists of the Frankfurt School, contrasting Theodor Adorno and Max Horkheimer’s dismissal of anticolonial and progressive movements both in the West and in the global South with Herbert Marcuse’s mentorship of US activists in the Black radical tradition. Examining a broad swath of German literary, cultural, and political-critical work from the early 19th century to the present, I show how this German tradition of progressive thought has the potential to both offer key tools for seeing the big picture and trivialize the concerns of those on its margins. Understanding why a world-famous progressive tradition returns to its conservative roots is indispensable to safeguarding egalitarian values from the intolerance that pervades even those spaces once thought safe.

Advisor: Feldman, Karen
Developing Interfacial Solar Vapor Generation into a Sustainable Desalination Technology

Seawater desalination is one of the most resilient approaches for obtaining water. However, conventional desalination technologies are also some of the most energy-intensive water treatment processes. For this reason, seawater desalination is often viewed as a last resort, and is generally only an option for large urban centers—where the costs can be spread across densely populated districts. With limited access to reliable power grids, technical and managerial expertise, essential supply chains, and financial resources, smaller communities are often the most vulnerable to the impacts of climate change./nInterfacial solar vapor generation (ISVG) is a phenomenon observed in nano-enabled materials to efficiently vaporize water at extremely high efficiencies when exposed to sunlight. Traditionally, these are porous, light-absorbing materials that float at the air-water interface where evaporation normally takes place. When irradiated by sunlight, these materials absorb that light, convert that light into heat, transfer that heat to water in its pores, and accelerate the rate of evaporation. As a result, these 2D-ISVG materials can achieve an evaporative flux of 2.00 kg m-2 h-1, which is nearly 200% higher than natural rates. While impressive, this rate is still too low for many practical applications. To increase this rate, we have developed a 3D-ISVG material that utilizes capillary action to wick water onto additional surfaces for evaporation. This enhancement has allowed us to achieve an evaporative flux of 34.7 kg m-2 h-1. Given this higher productivity, we have begun evaluating the feasibility of developing 3D-ISVG into a sustainable desalination technology for small-island communities. Specifically, we have been working with Bungin Island in Indonesia to understand how contextual factors should inform the design and implementation of this technology as a means of providing sustainable water access in a climate-impacted future.

Advisor: Mi, Baoxia
Sustainable Displacement and the Rohingya Refugee Camps

There are currently more displaced people worldwide than ever before, with over 100 million displaced people globally. Rates of displacement continue to rise due to the pace, scale, and persistence of ethnic conflicts and environmental disaster due to climate change. These displacements increasingly become protracted ones, as in refugee camps that last for decades, with countries of the Global South bearing the brunt of “hosting” the displaced. This dissertation puts forth the case of the Rohingya refugees in Bangladesh, currently in the largest and most climate-vulnerable refugee camp in the world, to investigate what happens when the twin crises of climate change and refugee influx converge, and when “sustainability” is promoted as a desirable humanitarian response goal in refugee camps./nThis project traces the evolution of humanitarian relief projects in the Rohingya refugee camps in Bangladesh, from the start of the Rohingya refugee crisis in 2017 to the present, through four years of ethnographic fieldwork, including interviews with United Nations officials and humanitarian and development workers in the Rohingya refugee camps, climate scientists, Rohingya activists, and Bangladeshi policymakers and researchers, as well as archival analysis of United Nations historical records, and participant observation in international conferences and research workshops. Drawing on theoretical debates from the fields of humanitarianism, critical development, refugee and migration studies, political ecology, and climate adaptation, I argue that the international humanitarian response in the Rohingya refugee camps is increasingly defined by and through a “sustainable displacement” regime, in which focus on reducing settlements’ environmental impact can surpass bearing witness to the injustice inherent in their existence. My findings show how emerging climate adaptation technologies and practices in the Rohingya refugee camps, the first refugee setting with climate resilience goals, have sweeping implications for the human rights of people in protracted displacement situations globally. In doing so, this research acts as a critical intervention that highlights the stakes for planning for climate change in humanitarian settings while complicating the evaluative binary of success/failure in conditions of protracted displacement.

Advisor: Kammen, Daniel M
Xinxing’s Demon: The Three Levels Movement and a Crisis of Scriptural Authority in Sui-Tang Chinese Buddhism

This dissertation presents a study of the writings and thought of the controversial Chinese Buddhist teacher Xinxing (ca. 540–594 C.E.). It also charts the reception of Xinxing’s writings after his death and the development of his teachings by his followers, often called the Three Levels movement. Drawing on recently discovered manuscripts by Xinxing, I present a new interpretation of his intellectual aims. I argue that Xinxing’s primary concern was to achieve certainty in scriptural interpretation. To that end, he developed a unique conception of how and for whom Buddhist scripture was authoritative, suggesting that the interpretation of scripture must be governed by the explicit instructions of the Buddha as transmitted in scripture itself. In Xinxing’s view, one of the primary injunctions conveyed by scripture was that parts of scripture should only be read, used, and interpreted by the audience for whom the Buddha intended them. This conception led Xinxing to compile passages of scripture according to a complex set of interpretive criteria, yielding a set of mature writings meant to function as a reduced Buddhist canon for his followers. I argue that Xinxing’s attempt to modify and delimit the corpus of authoritative Buddhist scriptures was unique and controversial in the context of sixth- and seventh-century China. I show that, in many cases, the writings of Xinxing’s later followers center around attempts to defend Xinxing’s authority to make such a modification. I conclude by suggesting that the projects of Xinxing and his followers constituted important interventions in a broader debate over the nature and identity of authoritative scripture in sixth- and seventh-century China.

Advisor: Sharf, Robert
Students’ Judgments about Bullying Situations in Schools: Differences among Students with Bullying Experience, Victimization Experience, and No Experience

In the current study, I examined students’ judgments as well as assessed if there are differences in the judgments among three groups of middle and high school and college students ages 12-23 who reported having (a) engaged in bullying, (b) experienced bullying victimization, and (c) had no experience of bullying. I employed social domain theory as my theoretical framework and a mixed method approach that consisted of statistical analyses and a semi-structured interview with questions about hypothetical bullying situations. I conducted a combination of Fisher’s exact tests, McNemar’s test, and logistic regression to analyze participants' judgments. I found that students with bullying experience, just like their peers with victimization experience and no experience, disapproved of unprovoked bullying and aggression in general primarily due to concerns about injuries and harm. Similar to their peers, students with bullying experience also disapproved of bullying even in situations with mitigating factors, such as when the intention of the protagonist was to avoid becoming the target of bullying or when the protagonist was less physically strong than the target. The current study adds to the growing body of evidence that people with aggressive behaviors do engage in moral judgments and are just as concerned about the potential harm from bullying and aggression as their peers without bullying experience.

Advisor: Turiel, Elliot
Distribution of Class Groups

One goal of this thesis is to prove theorems that elucidate the Cohen-Lenstra-Martinet conjectures for the distributions of class groups of number fields, and further the understanding of their implications. We start by giving a simpler statement of the conjectures. We show that the probabilities that arise are inversely proportional to the number of automorphismsof structures slightly larger than the class groups. We find the moments of the Cohen-Lenstra-Martinet distributions and prove that the distributions are determined by their moments. In order to apply these conjectures to class groups of non-Galois fields, we prove a new theorem on the capitulation kernel (of ideal classes that become trivial in a larger field) to relate the class groups of non-Galois fields to the class groups of Galois fields. We then construct an integral model of the Hecke algebra of a finite group, show that it acts naturally on class groups of non-Galois fields, and prove that the Cohen-Lenstra-Martinet conjectures predict a distribution for class groups of non-Galois fields that involves the inverse of the number of automorphisms of the class group as a Hecke-module. The Cohen-Lenstra-Martinet Heuristics give a prediction for the distribution for the p-Sylow subgroups of the class groups of random Γ-number fields when p ∤ |Γ|. In this thesis, we prove several results on the distributions of the class groups for some p||Γ|, and show that the behaviour is qualitatively different than the predicted behaviour when p ∤ |Γ|. We do this by using genus theory and the invariant part of the class group to investigate the algebraic structure of the bad part of the class group. For general number fields, our result is conditional on a natural conjecture on field counting. For abelian or D4 fields, our result is unconditional.

Advisor: Wood, Melanie
Shin, Sug Woo