UT Electronic Theses and Dissertations
Permanent URI for this collectionhttps://hdl.handle.net/2152/11
This collection contains University of Texas at Austin electronic theses and dissertations (ETDs). The collection includes ETDs primarily from 2001 to the present. Some pre-2001 theses and dissertations have been digitized and added to this collection, but those are uncommon. The library catalog is the most comprehensive list of UT Austin theses and dissertations.
Since 2010, the Office of Graduate Studies at UT Austin has required all theses and dissertations to be made publicly available in Texas ScholarWorks; however, authors are able to request an embargo of up to seven years. Embargoed ETDs will not show up in this collection. Most of the ETDs in this collection are freely accessible to all users, but some pre-2010 works require a current UT EID at point of use. Please see the FAQs for more information. If you have a question about the availability of a specific ETD, please contact tsw@utlists.utexas.edu.
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Item Structural and dynamical properties of H₂O and D₂O under confinement(2023-08) Liang, Chenxing; Aluru, Narayana RaoWater (H₂O) is of great societal importance and there has been a significant amount of research on its fundamental properties and related physical phenomena. Deuterium dioxide (D₂O), known as heavy water, also draws much interest as an important medium for medical imaging, nuclear reactors, etc. Although many experimental studies on the fundamental properties of H₂O and D₂O have been conducted, they have been primarily limited to understanding the differences between H₂O and D₂O in the bulk state. In this report, using path integral molecular dynamics simulations, the structural and dynamical properties of H₂O and D₂O in bulk and under nanoscale confinement in a (14,0) carbon nanotube are studied. We find that in bulk, the dipole moment of D₂O tends to be 4% higher than that of H₂O and the hydrogen bonding of D₂O is also stronger than H₂O. Under nanoscale confinement in a (14,0) carbon nanotube, H₂O and D₂O exhibit a smaller bond length and bond angle. The hydrogen bond number decreases, which demonstrates weakened hydrogen bond interaction. Moreover, confinement results in a lower libration frequency, and higher OH(OD) bond stretching frequency with an almost unchanged HOH(DOD) bending frequency. The D₂O-filled (14,0) carbon nanotube is found to have a smaller radial breathing mode than the H₂O-filled (14,0) carbon nanotube.Item Characterizing the onset and offset of motor imagery during passive arm movements to control an upper-body exoskeleton(2023-08) Mitra, Kanishka; Millán, José del R., 1962-; Deshpande, Ashish D.In recent decades, two distinct technological advances have been made to understand and improve motor rehabilitation: human-robot interaction and brain-machine interfaces (BMIs). While the introduction of robots has been shown to increase the dosage and intensity of therapy, robot-mediated rehabilitation has failed to achieve clinically relevant levels of improvement over conventional therapy due to its limited influence on neural recovery. On the other hand, BMI-driven therapies have been able to engage neural activity, but the amount and extent of proprioceptive feedback elicited by passive movements were not sufficiently rich to boost activity-dependent plasticity. Harnessing their combined efforts could open up unprecedented opportunities for connecting neural commands to motor output, which may be the missing link to achieving clinically relevant recovery. However, a significant challenge is whether motor intentions from the user can be accurately detected using non-invasive BMIs in the presence of instrumental noise and passive movements induced by the rehabilitation exoskeleton. Therefore, this study aims to characterize the onset and offset of motor imagery during passive arm movements induced by an upper-body exoskeleton to allow for the natural control (initiation and termination) of functional movements. Ten participants were recruited to perform kinesthetic motor imagery (MI) of the right arm while attached to the robot, simultaneously cued with LEDs indicating the initiation and termination of a goal-oriented reaching task. Using electroencephalogram (EEG) signals, we built a decoder to detect the transition between i) rest and beginning MI and ii) maintaining and ending MI. Offline decoder evaluation achieved group average onset accuracy of 60.7% and 66.6% for offset accuracy, revealing that the start and stop of MI could be identified while attached to the robot. Furthermore, pseudo-online evaluation could replicate this performance, simulating reliable online exoskeleton control. Finally, results from a pilot study indicate the feasibility of the onset and offset of MI to control passive arm movements induced by an upper-body exoskeleton using a novel real-time streaming hierarchical machine-learning approach. Our method showed that participants could produce strong and reliable sensorimotor rhythms regardless of noise or passive arm movements induced by wearing the exoskeleton, which opens new possibilities for BMI control of assistive devices and could have further implications for novel neurorehabilitation strategies.Item US walking distances and pedestrian safety outcomes + integrating autonomous vehicles into Texas’ Statewide Analysis Model(2023-08) Vellimana, Maithreyi; Kockelman, KaraThis thesis consists of two, very distinct parts. The first part focuses on pedestrian safety, while the second investigates Texas travel impacts of autonomous cars and trucks. Part 1 examines walk distances across the United States by time of day and year, using data from the National Household Travel Survey 2016/2017, with the aim to understand factors contributing to higher pedestrian deaths at night across various states. Using hurdle regression to predict daily walk-miles traveled (WMT) and nighttime WMT across the US, the study finds that the decision to walk and distances walked on each survey day and night vary significantly with demographic attributes (like race, income, worker status and education), time of year, latitude, state of residence, and other factors. Longer daylight hours and more nighttime walking do not appear to be the reasons for some states’ much higher pedestrian fatality rates. Additionally, there is no evidence from traffic fatality rates due to alcohol consumption or overall alcohol consumption per capita to support this result. Differences in built environments, law enforcement, and aggressive driving may be key factors for much higher pedestrian death rates in southern settings. Part 2 focuses on predicting travel patterns for the year 2040 by integrating mode options for autonomous vehicles (AVs), shared autonomous vehicles (SAVs), and automated trucks (ATrucks) into the Texas Statewide Analysis Model (SAM). Initial results suggest that for long-distance passenger trips, human-driven vehicles (HVs) are estimated to remain more popular than AVs and SAVs, with roughly 10% increases (for both business and non-business trips) for the shared ride 3+ (SR3+) mode option on trips below 400 miles (drawing primarily from air and intercity-rail trips). The airline mode remains preferred choice for trips over 400 miles (80% of all >400 mile person-trips and 18% of total PMT, which is 11.6% of all person-trips). Introduction of ATrucks had its biggest impacts on freight movements for the oil, gas, and mining sectors. Major roadways for freight-truck movement (under both the before and after-AVs scenarios) are US 60, US 99, I-40, I-35, US 87, US 287 and US 57. While the model applications provide some valuable insights, SAM model limitations (such as exclusion of bus as a mode in long-distance passenger model, and fixed mode splits for most passenger trips) highlight the need for future research and improvements. Another limitation in this study is that only the mode choice step of a model has been updated to account for introduction of these new modes. So this model will predict the effect on mode splits (and trip distribution when feedback loops are included), but it cannot reflect the change in trips due introduction of these new modes. Future wok will focus on updating trip generation to reflect effect on trip production. Addressing these limitations and calibrating the model mode choice parameters will enhance the study and the scope of the SAM model, enabling a more comprehensive analysis of the impacts of AVs across the nation and Texas.Item Synthesis and Raman spectroscopy characterization of long Carbon Nanotubes(2023-08) Cantu, Rodolfo, Jr.; Shi, Li, Ph. D.Carbon Nanotubes (CNTs) are promising nanomaterials with outstanding thermal, electrical, and mechanical properties. Composed of carbon atoms arranged in thin cylindrical walls, these nanostructures have promising applications in nanoelectronics, ultra-strong fibers, and thermal management solutions. Chemical Vapor Deposition (CVD) has been used to grow CNTs from catalytical nanoparticles at low pressure and high temperatures. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization of the structures of CNTs can potentially induce defects due to the high electron beam energy. This thesis reports an effort to establish Raman spectroscopy mapping as a relatively non-invasive technique for locating individual suspended and long single-walled carbon nanotubes (SWCNTs) grown by catalytic CVD before they are transferred for subsequent measurements of their thermal transport and other properties. The g-band and radial breathing mode in the Raman spectrum is used to identify SWCNTs and determine their diameters.Item The development of a low-cost welding simulator based on augmented reality(2023-08) Salazar, Carlos D.; Chinchali, Sandeep; Longoria, Raul G.The current study presents an innovative approach to welding simulation by leveraging augmented reality (AR) technology, aiming to replicate the welding experience. The development of this simulator involves the fabrication of physical models, including a welding coupon and a welding torch, both embedded with images. These images are then tracked by Unity software to create an augmented reality environment. This unique combination of physical elements and software tracking enables real-time calculation and visualization of crucial welding parameters, such as work angle, travel angle, contact tip to working distance (CTWD or stick out), and travel speed. This simulator not only provides users with immersive visual feedback during the welding process but also records their welding parameters, offering a valuable dataset for subsequent analysis and comparison with real-world welding data. This is facilitated by a custom-developed welding sensor unit (WSU) attached to the actual welding torch. Furthermore, the simulator offers an environment to replicate the movements made by the welder in a real welding environment. These functionalities together endorse the simulator’s potential applications, from training novice welders to generating synthetic data for various research and industrial purposes.Item Towards telementoring for needle insertion(2023-08) White, Lourdes Romy; Fey, Ann MajewiczThis thesis presents a telementoring haptic system that aims to achieve online, bidirectional interaction between a medical mentor and a medical trainee during needle insertion training. The system can be seen as the integration of two modes of haptic feedback: (i) kinetic feedback which informs the mentor of the trainee's insertion forces and (ii) tactile feedback which guides a trainee along an insertion path according to the mentor's recommended motions. In our first experiment, addressing (i), we evaluated five forms of feedback with respect to trainee-force classification determined by the mentor. Our system adopts haptic plus visual feedback as it yielded the highest median accuracy (100\%). In the second experiment, addressing (ii), we tested the efficacy of a tactile guidance sleeve in comparison to traditional verbal guidance. The current design of the sleeve was shown to be less intuitive than verbal guidance. We formed educated hypotheses about possible improvements to the sleeve and discuss lessons learned about tactile feedback applied to guidance in medical tasks.Item Design and characterization of a coating device to enable multilayer structures in microscale selective laser sintering(2023-08) Liao, Aaron; Cullinan, MichaelThe microscale selective laser sintering process (µ-SLS) is an additive manufacturing technique that enables the creation of metal features with sub-5 µm in-plane resolution. In this process, a layer of metal nanoparticle ink is deposited onto a substrate and positioned beneath an optical subsystem with a nanopositioning stage. Using a digital micromirror device, a laser is spatially modulated to selectively heat particles in desired regions to cause sintering. The substrate is then moved to a coating station where the sintered features are recoated by a meniscus-guided coating process. The slot-die coating process was originally proposed and adopted as the recoating method for this critical step. Due to challenges with depositing consistent ink thickness across the recoated part and limitations with the volumetric resolution, a new meniscus-guided approach inspired by blade coating has been implemented and is able to recoat parts with layer thicknesses of less than 1 µm. Additionally, the multilayer performance of µ-SLS has improved significantly, now able to produce fully sintered layers up to a depth of 50 microns of material.Item The theoretical development and generalization of some alternating current test methods(1935) Reed, Myril B. (Myril Baird); Not availableItem Relation of potential differences to bud inhibition in Phaseolus multiflorus(1935) Rehm, Warren S., 1907-1994; Lund, E. J. (Elmer Julius), 1884-1969Item Synthesis of hydantoins with hypnotic properties(1935) Rigler, Neil Edward; Henze, Henry R., 1896-1974Item The mood of the unreal condition in modern English(1935) Snellings, Dorus Alvin; Callaway, Morgan, 1862-1936Item Financing extra curricular activities(1934) Shepherd, Everett M.; Not availableItem The multiple-list textbook law and its relation to the needs of local school communities as exemplified in the state of Texas(1934) McDonald, Leslie Carlisle; Not availableItem Some aspects of the monetary use of silver(1934) Gonzalez, Richard Joseph; Not availableItem Doctoral thesis recital (opera directing [lecture])(2020-03-12) Jumonville, Margaret; Unable to determine"Pretty young woman": Exploring physicality and gender performance through a queer Cherubino -- "Non so più cosa son" from Le nozze di Figaro (1786)Item History of federal relations with the Five Civilized Tribes of Indians since 1865(1935) Davis, Edward, Ph. D.; Not availableItem Doctoral thesis recital (collaborative piano)(2024-04-22) Lin, Xiaoyi; Unable to determine,Violin sonata no. 3 in D minor op. 108 / Johannes Brahms -- Unremembered wings / Andrea Clearfield -- Sonatina for flute and piano / Pierre Sancan.Item A history of Baptist educational efforts in Texas, 1829-1900(1934) Wilson, Carl Bassett, 1901-1938; Eby, Frederick, 1874-1968Item The determinants and trading consequences of automated information acquisition(2023-12) Kettell, Laura; McInnis, John M.; Bauguess, Scott; Chen, Shuping; Koonce, Lisa; Zhao, WuyangI examine the determinants and trading consequences of automated acquisition of financial reports. Prior literature predominately studies human-based information acquisition, yet capital market participants are increasingly relying on automation to acquire financial reports. Using a novel approach to identify automated downloads of 10-Ks, I find strong evidence that automated and human downloads are positively correlated, suggesting that humans’ own interests influence how machines are programmed. I also find that machines selectively download the 10-Ks for firms with higher expected information frictions and/or misvaluation (e.g., smaller, value firms with complex filings). Using staggered XBRL adoption as an instrument for automated downloads, I find that automated downloads increase trading volume, particularly for firms with information frictions. However, I do not find evidence that automated downloads impact price movements or price efficiency. Taken together, the evidence suggests that automated acquisition of 10-Ks leads to differential interpretations, resulting in more trading but not necessarily more informed trading.Item A rambling woman : confused and certain(2023-08) Constantine, Gabrielle; Lucas, Kristin, 1968-This paper is a self-review of work produced by Gabrielle Constantine from 2021 to 2023 at the University of Texas at Austin.