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Texas ScholarWorks was established to provide open, online access to the products of the University's research and scholarship, to preserve these works for future generations, to promote new models of scholarly communication, and to help deepen community understanding of the value of higher education.
UT Tower and campus image credit: Earl McGehee, CC-BY, https://www.flickr.com/photos/ejmc/7452145850
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Recent Submissions
Investigating the effects of two virtual reality types on individual self-perception and user experience in adults : realistic humanoid vs fantastical animated avatars
(2023-12) Tang, Junjie; Zhang, Yan (Ph. D. in information and library science); Bailey, Jakki O.
Avatars, in the virtual world, have transformed our ways of interaction and experience. This study investigated the impact of avatar types in VR technologies on adults’ perception, focusing on realistic humanoid and fantastical animated entities. We explored how embodying these two avatars in a basic virtual room affect participants’ emotions, self-perception, and behaviors while taking into account their tendency to anthropomorphize non-human entities. Participants engaged in movement activities and a tiny human-like game using head-mounted displays (HMD) in a simulated environment. From 14 interviews, we identified trends in avatar type and anthropomorphism’s effects on perception shifts, emotional responses, and behavior changes related to avatar embodiment. Our findings offer valuable insights for future avatar design and research, with potential enhancements in healthcare, education, and collaborative technologies, contributing to a deeper understanding of VR embodiment and user engagement.
Groundwater nitrogen concentrations and composition across an arctic subterranean estuary
(2023-12) Sanders, Aquanette; McClelland, James W.; Erdner, Deana L.
Groundwater is considered an important source of dissolved organic matter (DOM) and inorganic nutrients to coastal ecosystems. However, little is known about contemporary groundwater inputs to Arctic coastal waters or how they may change with global warming. Research at Beaufort Lagoon Ecosystems Long Term Ecological Research (BLE LTER) field sites focusing on supra-permafrost groundwater flowing into Simpson Lagoon, Alaska are broadening our understanding of groundwater inputs in this under-studied and rapidly changing region. Field trips to Simpson Lagoon during 2021 and 2022 aimed to quantify patterns in organic matter and inorganic nutrients across the tundra-lagoon interface and get an idea of the diagenetic processing of DOM. Concentrations of inorganic nutrients (nitrogen, phosphorus, and silica) were collected across salinity to consider microbial processing of nutrients. Total hydrolyzable amino acid (THAA) composition was used as an indicator of DOM sources and lability across the salinity gradient. Salinities of groundwater/porewater collected across this interface spanned 0 to 69. Departures from conservative mixing across this salinity gradient were used to assess transformations within the fresh-marine groundwater mixing zone. We found that fresh groundwater along the Beaufort Sea coast has significantly more DOM and THAA than river surface waters. Mixing models suggest that along the subterranean estuary, the influence of fresh groundwater, marine groundwater, and lagoon surface water on inorganic and organic nitrogen varies seasonally. Additionally, principal component analysis (PCA) results relating amino acid composition to environmental variables suggest that groundwater DOM is more degraded than the lagoon DOM. Quantifying DOM and inorganic nutrients and understanding the composition and lability of DOM is imperative to interpreting how groundwater inputs affect lagoon ecosystems.
Water solubility in evolved lunar melts with implications for lunar degassing history
(2023-12) Moeller, Caitlin; Sun, Chenguang
Constraint of lunar water budgets is vital to understanding the evolution of the rocky body. A wide variety of water abundances have been measured in lunar samples, leading to a large range of initial water budget estimates. This study targets evolved late-stage Lunar Magma Ocean (LMO) melts trapped at the base of the crust, which are enriched in volatiles. Synthesized samples are saturated, experimentally placed at relevant P-T conditions, and quenched into glass. The measured water contents represent the water capacity of this composition as a function of pressure. Comparing measurements against six previous models, I evaluate their ability to reproduce the observed data and suggest a best fit model for this unique composition. Furthermore, at reduced conditions H₂ becomes a more dominant fluid species, reducing the partial pressure and consequently the solubility of H₂O. Previous models do not include the effects of oxygen fugacity or H-volatile speciation. I provide a thermodynamic framework to calculate H₂O/H₂ speciation as a function of oxygen fugacity. With the best fit model and thermodynamic framework, the last 1% of LMO liquid (urKREEP) is found to have a maximum capacity of 0.43 wt.% water at IW-2 and a crustal thickness of 40 km. Using previous bulk LMO water contents, it is concluded that urKREEEP could exceed the saturation limit in many scenarios. Excess water was therefore likely degassed through the lunar crust, effectively reducing the observable water budget of the lunar mantle.
InGaAs/InP chip-based mid-infrared optical phased arrays for communications and sensing
(2023-12) Midkiff, Jason C.; Chen, Ray T.; Hall, Neal; Fan, Donglei; Pan, David Z; Incorvia, Jean A
The mid-infrared atmospheric transmission windows (wavelengths ~ 3–5 and 8–14 µm) provide a unique opportunity for low-loss transmission in areas such as thermal imaging, lidar, infrared homing, and line-of-sight communications. Additionally, in comparison to traditional operation in the near-infrared, the lower background solar irradiation of the mid-infrared permits higher signal-to-noise detection. In spite of these inherent benefits, the advance of applications in the mid-infrared has lagged their near-infrared counterparts, due to the lack of maturity in material properties, light sources, and detectors specific to the region. This research seeks to advance the state of the art in on-chip photonics operating in the mid-infrared transmission windows. In particular, in this work I build and demonstrate operation of optical phased arrays (OPAs) operating at a wavelength of 4.6 µm. On-chip OPAs provide non-mechanical beam formation and steering in a compact form factor—an enabling technology for the next generation of miniaturized mid-infrared systems that will be incorporated into, e.g., unmanned aerial vehicles. The work is carried out in an InP-based platform in consideration of the fact that InP-based quantum cascade lasers are now the preeminent mid-infrared light source, therefore conceiving the potential for a fully monolithic integrated OPA solution. In the first phase of this research, I developed and demonstrated a 1D periodic OPA, that is to say, a 1D periodic array of emitting elements, permitting beam steering in one dimension. The thermo-optic effect was employed for phase tuning and surface gratings were used for emitting elements. An unambiguous steering field-of-view (FOV) of 23° with 38 resolvable points was achieved. In the second phase of this research, the OPA was revamped to improve performance. First, heat-isolation trenches were incorporated to improve phase tuning efficiency. Second, the emitting elements were changed to total-internal-reflection mirrors, whose small area permitted distribution in a 2D array. Third, the array was made aperiodic—the emitter positions being optimized to maximize the number of resolvable points. Within an observed 23°-diameter-FOV >500 resolvable points were achieved, with an estimate of >1000 resolvable points within the full device FOV.
Three essays on the state, public opinion, and environmental politics in Latin America
(2023-12) Calacino, Anthony; Gerring, John, 1962-; Nielson, Daniel; Weyland, Kurt G; Abers, Rebecca
This dissertation explores how Brazil and Mexico respond to environmental challenges, and how these responses can influence the political behavior of citizens. Three essays delve into specific aspects of this relationship. The first essay investigates the shifts in support for state-led environmental protection in the Brazilian Amazon. While Brazil historically succeeded in building such capacity, recent environmental state retrenchment remains inadequately explained. Drawing on data from Brazil's national congress, 300,000 fines for environmental infractions at the district level, and interviews with over 60 public officials and experts, I argue that partisan dynamics and electoral vulnerability jointly shape state-led environmental protection levels. Left-wing politicians consolidate capacity with low electoral vulnerability, whereas conservative counterparts erode it. Vulnerable centrist and right-wing governments tend to maintain capacity, while vulnerable left-wing governments lead to low support due to business elites' counter-mobilization. My findings highlight the role subnational politicians play in eroding capacity from the bottom-up, as well as how business elite behavior is not strictly-rational. Partisan-motivated reasoning helps explain puzzling patterns of mobilization against the Left and subsequently lower support for the state to achieve environmental protections. The second essay proposes and tests a theory on how extreme weather events and subnational government responses affect public trust in politics and democracy. My argument states that local government responses to extreme weather tend to exacerbate inequalities. The effects lead to disaffection toward the electoral system rather than individual politicians. Analyzing weather events and surveys of public opinion in Brazil and Mexico from 2006 to 2019, I find that drought lowers trust in elections. I validate the role of politicized resource distribution in explaining this relationship using a novel measure of demand for water at the municipal level. Moreover, in areas with high levels of clientelism, the individualistic exchange of goods and services for political support, trust in municipal governments becomes polarized when extreme drought occurs. These findings underscore the importance of fairness perceptions in disaster response, influencing political trust and aspects of democracy. My findings contribute to our understanding of how local governments manage environmental and societal interactions, and suggest how climate change may exacerbate declining support for democracy. The third essay explores foreign influence on Brazilian citizens' opinions regarding environmental protection through a pre-registered survey experiment (n = 1003). This research seeks to understand how influence from abroad affects public opinion of climate policies, which in turn helps explain why state capacity on the environment may change over time. I find limited overall effects of prompts about foreign aid and shame for environmental issues, except shame significantly decreases support for a carbon tax. Aid generally increases support among environmentally conscious citizens, but against expectations, it decreases support for climate policies among those who don't prioritize the environment while shame sometimes increases support. Overall, foreign pressures land differently for distinct citizens based on their environmental priorities. Foreign actors face the risk of polarizing support for greater policy commitments to the climate and environment.