Radio Instrument Design and Commissioning for 21 cm Cosmology and K-12 Education

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Description
The Hydrogen Epoch of Reionization Array is a radio interferometer targeting precision measurements of the 21 centimeter hydrogen line during the formation of the first stars in the Cosmic Dawn and the subsequent Epoch of Reionization (EoR) when the intergalactic

The Hydrogen Epoch of Reionization Array is a radio interferometer targeting precision measurements of the 21 centimeter hydrogen line during the formation of the first stars in the Cosmic Dawn and the subsequent Epoch of Reionization (EoR) when the intergalactic medium (IGM) was ionized. Studies of the distribution of neutral hydrogen during the EoR and Cosmic Dawn offer insight into how the structure in the universe formed and evolved. I present the as-built HERA design and discuss the commissioning of the array, as well as study the theoretical and lab performance of HERA's cross-talk mitigation system, which reduces the effect of signal chain leakage from neighboring antennas in the array.Additionally, I discuss three experiments targeted at educational or outreach uses in satellite or radio astronomy science. First, I present the design and commissioning of a new digital signal processing system for the Goldstone Apple Valley Radio Telescope (GAVRT), which operates a 34-m antenna as part of a K-12 initiative. Secondly, I describe the design of the telemetry decoder and subsequent analysis of received telemetry for the LightCube mission, which was a 1U CubeSat was designed to connect the public with space operations. Finally, I present the framework for a course lab that measures the rotation curve of the Milky Way with a low-cost radio telescope totaling under 200 dollars. The rotation curve of the Milky Way offers an exciting educational target for studies of spiral galaxy dynamics, and can be measured easily from the ground with simple instruments.
Date Created
2024
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Additive Manufacturing of Hydrocarbon-Based Elastomers and Composites

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Description
Additive manufacturing (AM) gathers increasing attention for its customization and sustainability benefits, including material efficiency, lightweighting, and energy conservation. This dissertation explores innovative strategies for 3D printing elastomers using vat photopolymerization (VP) and direct ink writing (DIW). The first study

Additive manufacturing (AM) gathers increasing attention for its customization and sustainability benefits, including material efficiency, lightweighting, and energy conservation. This dissertation explores innovative strategies for 3D printing elastomers using vat photopolymerization (VP) and direct ink writing (DIW). The first study introduces a strategy for incorporating high molecular weight isoprene rubber latexes into VP to address the challenges of processing elastomers. The addition of water-soluble monomers and crosslinkers to the latex aqueous phase yielded a photocurable, low-viscosity precursor suitable for VP. Photopolymerization in the aqueous phase created a hydrogel scaffold surrounding the polymeric particles, solidifying the latex into a green body. Post-processing removed water, driving the coalescence of isoprene rubber particles and resulting in a semi-interpenetrating polymepost-processing) with exceptional elongation at break up to 600%. Expanding on this, VP of sulfonated ethylene-propylene-diene monomer (sEPDM) latex demonstrated the 3D printing of olefinic elastomers. The sEPDM formed a physically crosslinked network due to ionic aggregation, leading to an interpenetrating polymer network (IPN) with tunable mechanical properties after sEPDM particles coalesced throughout the scaffold network during the post processing of printed green body. The introduction of polymerizable counterions for sulfonate groups at the sEPDM particle interfaces created a novel photocuring mechanism for latexes. The copolymerization of monomer added in the aqueous phase and 2-(Dimethylamino)ethyl methacrylate (DMAEMA) at the sEPDM particles generated a physically crosslinked hydrogel network through the ionic association on the latex particle interfaces. The absence of covalent crosslinked network highlighted the potential of 3D printing reprocessable materials. The last two projects utilized hybrid colloids composed of inorganic nanoparticles and styrene-butadiene rubber (SBR) particles for the 3D printing of polymer composites. The mixture of silica nanoparticle colloid and SBR latex demonstrated shear yield-stress behavior, enabling DIW. The modification of silica nanoparticle surface functionalities tuned the interaction between the silica and the polymer matrix, influencing the material mechanical properties. Electrically conductive fillers, single-wall carbon nanotubes (SWCNTs), were applied in SBR hybrid colloids to demonstrate VP of SWCNT-SBR composites. The results revealed enhanced electrical conductivity of the composites with increased SWCNT content, demonstrating the potential application of 3D printing elastomeric conductive materials.
Date Created
2024
Agent

On the Classification of Hyperbolic Triangle Groups and Non-Arithmetic Lattices of Hyperbolic Orbifolds

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Description
The study of hyperbolic manifolds, and more generally hyperbolic orbifolds, is inti-mately bound to the study of discrete subgroups of the isometry group of hyperbolic n-space. In the wake of certain rigidity theorems due to Mostow et al., a new program of

The study of hyperbolic manifolds, and more generally hyperbolic orbifolds, is inti-mately bound to the study of discrete subgroups of the isometry group of hyperbolic n-space. In the wake of certain rigidity theorems due to Mostow et al., a new program of study has developed in recent decades for the characterization of hyperbolic mani- folds by investigating certain invariants arising from the theory of numbers. Critical to the arithmetic study of hyperbolic manifolds are those discrete subgroups of the isometry group which have finite co-volume under the Haar metric, sometimes called lattices. These correlate to a particular tiling of hyperbolic space with a certain fun- damental domain. The simplest non-trivial example of these for hyperbolic orbifolds are triangle groups. These triangle groups, or more properly arithmetic Fuchsian tri- angle groups, were first classified by Takeuchi in 1983. In the proceeding manuscript, a concise introduction to the geometry of hyperbolic manifolds and orbifolds is put forth. The two primary invariants used in the study of the hyperbolic lattices, the invariant trace field and the invariant quaternion algebra, are then defined. There- after, a hyperbolic triangle group is constructed from the tessellation of the hyperbolic plane by hyperbolic triangles. A version of the classification theorem of arithmetic Fuchsian triangle groups is stated and proved. The paper concludes with a brief discussion regarding non-arithmetic lattices.
Date Created
2024
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Surface Activation of Polyethylene-Terephthalate (PET) to Enhance the Sustainability and Durability of Asphalt

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Description
Waste plastic is considered an environmental pollutant because it is not biodegradable. Therefore, there is increased interest in the use of recycled plastic in pavement construction. Polyethylene terephthalate (PET) is a thermoplastic polymer that is commonly used in the manufacturing

Waste plastic is considered an environmental pollutant because it is not biodegradable. Therefore, there is increased interest in the use of recycled plastic in pavement construction. Polyethylene terephthalate (PET) is a thermoplastic polymer that is commonly used in the manufacturing of containers and bottles. Waste PET is a durable material that has shown enhancement in performance when introduced into asphalt binder and asphalt mixtures. However, PET particles tend to separate from asphalt because of differences in density, molecular structure, molecular weight, and viscosity, leading to inadequate dispersion of PET particles in the asphalt. This incompatibility between PET and asphalt causes segregation, where storage stability becomes an issue. To solve this problem, applying a surface activation on the PET using another abundant urban waste (waste vegetable oil) was examined in this study, showing this method can be effective to enhance PET-asphalt interactions and consequently the storage stability of PET-modified asphalt. To ensure proper surface activation, it is important to thoroughly understand the chemo-mechanics of asphalt containing PET particles as well as the underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using computational modeling based on density functional theory along with laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface-activated PET and asphalt. To do so, the efficacy of bio-oil treatment was examined in terms of both the surface-activation capability and the durability of the resulting PET-modified asphalt. It was found that the grafted bio-oil on the PET particles can make a strong interaction with bituminous composites, leading to enhancing the durability and extending the service life of asphalt pavement by reducing the diffusion of free radicals and moisture into the bulk. The study was further extended to study the effect of coating the PET with biochar, showing the latter coating can improve the mechanical properties of the PET-modified asphalt and the adsorption behavior of the PET for volatile organic compounds. The performance of the waste PET was compared with another widely used modifier, crumb rubber.
Date Created
2024
Agent

Trust-Building Communication and Climate Risk Decision Making

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Description
A lack of public trust in governance institutions such as governments, federal agencies, and public health organizations limits national capacities to mitigate climate-related risks. Trustworthy sources of risk information are theorized to be more persuasive and more likely to motivate

A lack of public trust in governance institutions such as governments, federal agencies, and public health organizations limits national capacities to mitigate climate-related risks. Trustworthy sources of risk information are theorized to be more persuasive and more likely to motivate adaptive behaviors. Accordingly, this dissertation addresses relational and translational challenges of risk communication to support public health and safety by making climate science more accessible to communities at risk from extreme heat. This project developed and applied a theory-driven model of trust determination to understand how United States residents evaluate the trustworthiness of state governments and emergency management agencies. Using confirmatory factor analysis, a two-factor model of trustworthiness as self-reliability and source reliability was strongly empirically supported. This measurement model of trustworthiness was translated into experimental trustworthiness manipulations capable of creating statistically significant differences in perceptions of source reliability. The dissertation then tested the persuasive efficacy of trust-building risk messaging using randomized controlled trials, finding that when controlling for political ideology, message trust condition had a significant effect on attitudes toward extreme heat risk and preparedness as well as intentions to prepare for extreme heat events. Practical and theoretical implications are discussed.
Date Created
2024
Agent

Examining the Association of Family Environment and Parenting Practices on Sexual Minority Adolescent Physical and Mental Health Outcomes

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Description
Sexual minority youth experience significant health and mental health disparities compared to their heterosexual peers. Positive family relationships and effective parenting practices have been found to promote youth’s well-being broadly; however, there has been very little research conducted within the

Sexual minority youth experience significant health and mental health disparities compared to their heterosexual peers. Positive family relationships and effective parenting practices have been found to promote youth’s well-being broadly; however, there has been very little research conducted within the sexual and gender minority (SGM) populations. Furthermore, even though parental/familial acceptance of youth’s SGM identity has been consistently shown to be associated with better youth’s adjustment, very few studies have examined how the broader general parenting and familial processes intersect with SGM-acceptance. Hence, the aim of this study was to first examine the associations between (a) general parenting practices and family environment (i.e., positive parenting, negative parenting, mindful parenting, and family cohesion) and (b) SGM-specific practices (i.e., parental acceptance, parental microaggression and microaffirming behaviors) on SGM youth’s health (i.e., sleep disturbances & impairment, physical activity) and mental health (i.e., internalizing and externalizing symptoms) outcomes. The second aim of this study was to examine how SGM-specific practices may moderate the associations between general parenting and family environment variables and SGM youth health and mental health outcomes. The sample included 261 parents (Mage = 41.45, SD = 6.30, age range = 30 to 59) of sexual minority adolescents (Mage = 15.08, SD = 1.40, age range = 13 to 17) recruited nationwide in the U.S. via online recruitment. Results revealed that negative parenting was positively associated with child’s internalizing symptoms, externalizing symptoms, sleep disturbance, and sleep impairment. Meanwhile, mindful parenting was negatively associated with internalizing symptoms only. Parental acceptance, positive parenting, and family cohesion were not significantly associated with youth outcomes. No significant interaction emerged between parental acceptance and the four general parenting and family variables in predicting youth outcomes. Findings highlight the importance of examining how parenting practices and family processes were related to sexual minority adolescents physical and mental health outcomes.
Date Created
2024
Agent

Maladaptive Eating–Depression Symptom Networks Across Mexican American Children's Cultural Development

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Description
Research demonstrates that maladaptive eating (e.g., restriction, disinhibition) and persistent depressive symptoms often co-occur and may reinforce each other over time. However, little is known regarding the etiology of early maladaptive eating and depressive symptoms among Mexican American children and

Research demonstrates that maladaptive eating (e.g., restriction, disinhibition) and persistent depressive symptoms often co-occur and may reinforce each other over time. However, little is known regarding the etiology of early maladaptive eating and depressive symptoms among Mexican American children and how cultural orientation impacts co-occurrence. This study aimed to map the emerging structure of maladaptive eating–depression symptom networks, identify early dysfunctional mechanisms (i.e., symptoms) that maintain network structure, and explore how cultural orientation influences mechanisms. The sample included 263 low-income Mexican American children, assessed at 6-, 7.5-, and 9-years-old via maternal report. Mothers completed surveys on child eating, depressive symptoms, and cultural orientation. Data was analyzed using regularized partial correlation, Ising, and mixed graphical network models. Results showed that maladaptive eating networks were invariant over time. Central maladaptive eating symptoms were related to food responsiveness. Depressive symptom and combined networks were not stable enough for interpretation. Sadness and thoughts of worthlessness/inferiority emerged as central depressive symptoms at age 9. No bridge symptoms or moderated effects were large enough for interpretation. This study is the first of its kind to examine associations between eating and depressive symptoms among Mexican American children using network analysis. Results provide etiological information on the structure of co-occurring eating and depressive symptoms across late childhood and provide direction towards optimal prevention targets among this group.
Date Created
2024
Agent

Frameworks of Many into the Creation of One

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Description
Frameworks of Many into the Creation of One [FMOC] is a choreographic work that delves into the concept of identity: Who am I? Who are you? Who are we? What is the narrative that binds us? This piece offers an

Frameworks of Many into the Creation of One [FMOC] is a choreographic work that delves into the concept of identity: Who am I? Who are you? Who are we? What is the narrative that binds us? This piece offers an exploration of our interactions with the world around us as we navigate the ongoing process of self-discovery. FMCO illuminates the intersectionality of the individual within a community, examining the diverse ways in which we express ourselves in relation to our environment. IDENTITY: Individual Differences Expressed and Negotiated through Environmental Information. The work delves into the idea that identity is shaped by the transfer of information within one's environment. Through the mediums of storytelling, dance, and multimedia, FMCO offers the audience an immersive experience of frameworks and concepts that influence both their own identities and the identity of Alecea Housworth. The piece invites viewers to contemplate the dynamic interplay between individualism and the influences of one's surroundings. This paper delves into the intricate interplay between individuality and community, shedding light on the complexity inherent in the human experience. Exploring the frameworks being race, gender, religion, and gender, which impact experiences that shape the development of one's sense of self. Through the lens of dance, this study examines how individuals construct and embody their identities, offering a nuanced understanding of self-conception through communal engagement.
Date Created
2024
Agent

Towards More Accessible Human-AI Interactions in Sequential Decision-making Tasks

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Description
In today’s world, artificial intelligence (AI) is increasingly becoming a part of our daily lives. For this integration to be successful, it’s essential that AI systems can effectively interact with humans. This means making the AI system’s behavior more understandable

In today’s world, artificial intelligence (AI) is increasingly becoming a part of our daily lives. For this integration to be successful, it’s essential that AI systems can effectively interact with humans. This means making the AI system’s behavior more understandable to users and allowing users to customize the system’s behavior to match their preferences. However, there are significant challenges associated with achieving this goal. One major challenge is that modern AI systems, which have shown great success, often make decisions based on learned representations. These representations, often acquired through deep learning techniques, are typically inscrutable to the users inhibiting explainability and customizability of the system. Additionally, since each user may have unique preferences and expertise, the interaction process must be tailored to each individual. This thesis addresses these challenges that arise in human-AI interaction scenarios, especially in cases where the AI system is tasked with solving sequential decision-making problems. This is achieved by introducing a framework that uses a symbolic interface to facilitate communication between humans and AI agents. This shared vocabulary acts as a bridge, enabling the AI agent to provide explanations in terms that are easy for humans to understand and allowing users to express their preferences using this common language. To address the need for personalization, the framework provides mechanisms that allow users to expand this shared vocabulary, enabling them to express their unique preferences effectively. Moreover, the AI systems are designed to take into account the user’s background knowledge when generating explanations tailored to their specific needs.
Date Created
2024
Agent

An Evaluation Study of Object Interaction Framework Design for XR-Enabled Games

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Description
In game development, interaction frameworks provide generic functionality for users to engage with virtual worlds and are required to enable this on nonstandard hardware such as extended reality platforms. Currently, no publicly accessible frameworks exist that implement interactive world objects

In game development, interaction frameworks provide generic functionality for users to engage with virtual worlds and are required to enable this on nonstandard hardware such as extended reality platforms. Currently, no publicly accessible frameworks exist that implement interactive world objects in XR settings, prompting the question: if one were to be made, how and why would it be usable? This thesis explores the properties that make an XR-enabled object interaction framework usable by game developers and game designers. This thesis introduces the basic form of such a framework and the design of a set of user studies centered around this framework’s utilization in a game development workflow. User feedback is gathered for the study’s results, and is evaluated around user perception of framework expressiveness, extensibility, and ease of use. The results of the study found that users primarily judged usability through comparisons to real-world equivalents, utilization of conventional systems, object interactivity, clarity of framework components, usability of framework toolkits and these are discussed in relation to existing research on virtual object interaction.
Date Created
2024
Agent