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John Bickham field notebook: AK22001-AK22500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK22501-AK23000 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
Customer Visitation Pattern: A Robust Heterogenous Network Model of Human Mobility
No full textStudying human mobility across time and space has significant implications for urban planning, business management, and disaster studies. However, previous research in this area has identified several gaps, including a lack of detailed understanding of the connection between location characteristics and visit frequencies, a lack of suitable spatial-temporal network models, and limitations in applying existing models to various scenarios. To address these gaps, this doctoral dissertation research aims to provide a general framework from a network perspective to model customer visit patterns, particularly before and after natural disasters. This research will develop a Geospatial Artificial Intelligence (GeoAI) based framework to derive the visitation pattern from heterogeneous data sources, such as mobile phone trajectories, online reviews, and official census data. The proposed research will address the following research questions: How to quantitatively delineate customer visitation patterns based on mobility data and deep learning? What is the typical visitation pattern, and how does it change after a natural disaster? What would the visitation pattern be if the business changed some strategies? The proposed research will model heterogenous data in a network and use deep learning methods to validate and derive knowledge from it. This knowledge can guide business management and support spatial decision-making. Overall, this research will contribute to the development of a network perspective framework for modeling customer visit patterns, which can be applied to various scenarios and guide urban planning and business management decisions
Contact Mechanics and Tribology of Thermal and Electrostatic Friction Modulation for Surface Haptics
No full textHaptics, an integral part of human-machine interaction, offers a crucial sense of touch for immersive user experiences in many applications, such as virtual and augmented reality. While audio-visual interfaces have been significantly developed, seamlessly integrating touch sensation into these interfaces encounters hurdles due to mechanical and neurophysical complexities of the interaction of human skin with the physical world.
Surface haptics presents a promise for integrating touch into the audio and video interfaces, particularly with the widespread use of touchscreens. Various forms of haptic feedback have been explored in the surface haptics field. Among them, friction modulation-based haptic feedback has been demonstrated as an effective way to offer users a sense of virtual shapes and textures on surfaces. This method, however, has challenges such as variability in frictional performance. This variability hampers consistent user feedback and impedes device commercialization. To address the variability issue, this research aims to elucidate the impact of humidity on friction under electroadhesion based on the electrowetting effect and provides insight into the device design for more consistent haptic feedback. Understanding the intricate surface topography of the human fingerpad, which significantly influences contact mechanics, is another critical aspect. We examine the surface topography of the fingerpad in detail across scales and investigate its impact on contact mechanics studies. Moreover, the surface temperature is another factor that causes the variability of the frictional performances in the surface haptic devices. This work aims to understand the underlying mechanism of the surface temperature effect on friction to provide insight into device design for more consistent haptic feedback and propose a new method to modulate localized friction at lower operating voltages.
Additionally, the development of the 'Touchbot,' a wearable intermediary device, aims to overcome limitations in current surface haptics by providing localized tactile feedback in both lateral and normal directions across the contact patch, thus enhancing the realism of 3D rendering of virtual features. This study will focus on the building block of the Touchbot, an electroadhesive (EA) puck with high EA shear stress and high durability. We look into a more in-depth electromechanical point of view of EA devices, which offers a foundation for EA devices beyond this project
Influence of Microstructural Components on Hydrogen Embrittlement in Alloy 718: Insights from Friction Stir Processing and Additive Manufacturing
No full textHydrogen can cause severe embrittlement of high-strength metal alloys. Nickel alloy 718, a high-strength and corrosion-resistant alloy widely used in the aerospace and oil & gas industries, is highly susceptible to hydrogen embrittlement (HE). The premise of this work is to explore thermomechanical processing to obtain unique fine-grained microstructures in alloy 718. By employing electrochemical hydrogen charging, it aims to advance the understanding of the role secondary phases and grain boundaries (GBs) play in HE behavior. The overarching goal is to identify and propose strategies for the design of HE-resistant alloys.
Firstly, the effect of grain size and precipitates on HE susceptibility is investigated. Under tensile loading, the friction-stir processed and aged (FSP-A) condition with refined grains and precipitates showed substantially reduced HE susceptibility with 12.6% loss of ductility due to hydrogen as measured by reduction in area compared to the coarse grained peak-aged (PA) condition, which lost 29.9%. However, the FSP (with fine grains) and solution-treated (ST, with coarse grains) conditions prior to being aged display similar susceptibility to HE, despite higher hydrogen uptake in the former. The finding that microstructures with refined grains absorb more hydrogen yet have similar or reduced HE susceptibility, demonstrates their HE resistant character.
Secondly, the role of GB character distribution on HE susceptibility in fine-grained alloy 718 was evaluated. Three FSP cases, processed at rotational speeds of 200, 250, and 300 rpm, respectively, with a constant feed rate of 50 mm/min, produced 57%, 65%, and 53% high angle GBs (HAGBs), respectively. Tensile test results show that a high fraction of HAGBs in the microstructure can be correlated to higher HE susceptibility.
Finally, microstructures and properties of alloy 718 produced by selective laser melting (SLM) and subjected to heat treatments (HTs) were investigated. The as-printed material contained 4.7��0.8% volume fraction of the Laves phase, which is reduced to 0.2��0.1% after HT at 1150��C for 2 h. Tailored produced mechanical properties meeting API A6CRA requirements. HE behavior of SLM alloy 718 was similar to wrought alloy 718, with as-printed and aged conditions exhibiting higher HE susceptibility than solutionized conditions, likely by similar HE mechanisms
Exploration of New Passive and Active Attacks and Defense Methods for the KLJN and the VMG-KLJN Secure Key Exchangers
No full textThe Kirchhoff-Law-Johnson-Noise (KLJN) scheme is an unconditionally secure (information-theoretic) key exchanger based on the laws of classical statistical physics. The unconditional security of the KLJN scheme is provided by the Second Law of Thermodynamics, which requires thermal equilibrium (homogeneous temperature) for the system with zero flow. The KLJN scheme's foundational security principle was challenged by Vadai, Mingesz, and Gingl (VMG) through their VMG-KLJN system, which operates under inhomogeneous temperature and nonzero power flow conditions, while claiming equivalent security. Through our research, by applying various passive and active attacks against both schemes, we prove ideal KLJN scheme offers superior security over the VMG-KLJN scheme and reaffirm that thermal equilibrium remains the foundation of security. However, the VMG-KLJN method can, with appropriate countermeasures, be sufficiently secure for practical situations.
Our first study reveals that under practical conditions with nonzero cable capacitance and inductance, the VMG-KLJN scheme is vulnerable to certain passive attacks (crossover frequency attack and noise temperature attack), while the original KLJN scheme remains resistant against such attacks. In other words, the VMG-KLJN system is less secure than the original KLJN system. We also show that some of these vulnerabilities can be fixed by yet another new protocol that we introduce here. However at least one of these vulnerabilities will always remain. Thus, the information leak is never mathematically zero.
In our second study, the vulnerability of the VMG-KLJN key exchanger against two active attacks (current injection and voltage insertion attacks) is exposed. The security vulnerability arises from the fact that the effective driving impedances are different between the HL and LH cases for the VMG-KLJN scheme, whereas for the ideal KLJN scheme, they are the same. Two defense schemes are demonstrated, each effective against only one type of attack, but not against the two attacks simultaneously. The theoretical results are confirmed by computer simulations.
In the latter part of the dissertation, we demonstrate the security vulnerability of the ideal KLJN key exchanger and the VMG-KLJN key exchanger, respectively, against transient attacks. Transients start when Alice and Bob (two communicating parties) connect the wire to their chosen resistor at the beginning of each clock cycle. A transient attack occurs during a short duration of time, before the transients reflected from the ends of Alice and Bob mix together. The information leak arises from the fact that Eve (eavesdropper) monitors the cable and analyzes the transients during this time period. We demonstrate such a transient attack, and, then we introduce a defense protocol to protect against the attack. Computer simulations demonstrate that after applying the defense method the information leak becomes negligible
Wind Tunnel Data Quality Assessment and Improvement Through Integration of Uncertainty Analysis in Test Design
No full textThe practical application of uncertainty quantification in wind tunnel testing is not consistently or proactively applied. Although there is a solid methodology to quantify uncertainty, the resources required to implement this methodology at the pace of testing while adapting to the unique designs for each test are rarely available. This research combines the use of Monte Carlo simulations for uncertainty quantification with a decision-based integration of uncertainty estimates into the test design process and test execution. This implementation reduces the resources required to routinely quantify uncertainty to a practicable level and aims to proactively affect data quality by incorporating uncertainty estimates into early test design decisions. This methodology is used in the design, execution, and data analysis of a wind tunnel test at the Oran W. Nicks Low-Speed Wind Tunnel (LSWT) at Texas A&M University. The test analyzes the uncertainty in the aerodynamic coefficients and performance parameters of an aircraft test model. After quantifying the uncertainty of the aerodynamic coefficients, this research investigates a potential elemental error source in the measurement of static aerodynamic coefficients due to oscillating nonlinear aerodynamic loads. Notable results from this research include the demonstration of integrating uncertainty analysis with test design in a practical way, reduction of uncertainty intervals in aircraft performance parameters measured in the LSWT by an average of more than 90% through this integration, and experimental evidence of an elemental error source from oscillating nonlinear aerodynamic loads in the measurement of static aerodynamic coefficients
First-Year and First-Gen: Assessing the Information Literacy Skills of First-Year, First-Generation College Students
Get PDFAs higher education continues to focus its attention on first-generation college students, academic libraries are increasingly interested in designing outreach and instruction programs to support these students, especially during their first year of college. This study informs these efforts by implementing a standardized test to assess the information literacy skills of first-year-first-generation college students. Study results reveal that first-year, first-generation college students demonstrate substantial information literacy skills. However, gaps remain in comparison with first-year, continuing-generation students, particularly in understanding the research process and scholarly communication
Economic Indicators of the College Station - Bryan MSA, January 2025
No full textThe Business-Cycle Index decreased 0.2% from October 2024 to November 2024.1 The local unemployment rate increased to 3.3% in November 2024 compared to 3.2% in October. Local nonfarm employment increased by 0.04% from October 2024 to November 2024. Inflation-adjusted taxable sales decreased by 1% from October 2024 to November 2024. For 2023, the newly released Real Gross Domestic Product (GDP) for the College Station-Bryan MSA grew at an annualized rate of 3.9%, more than both the state of Texas (at 3.8%) and the entire U.S.(at 2.3%) over the same period
Impact of Library Collections on Faculty Teaching, Research, and Retention: A Mixed-Methods Study
Get PDFIn recent decades, college and university libraries have been called to demonstrate their impact on their institutions��� teaching and research missions. One way that libraries can demonstrate their impact is by evaluating how library collections can influence faculty recruitment and retention decisions. This study builds upon an existing study aimed at evaluating this impact. The authors apply a mixed-methods approach to an existing data set in order to identify differences in impact based upon faculty discipline and rank. The authors found that tenured faculty as well as faculty in the Arts and Humanities were significantly more likely to include the library as part of their recruitment and retention decision making
Essays on Social Preferences
No full textThis dissertation includes three essays in the field of behavioral economics, with a special focus on social preferences using laboratory experiments. The first essay investigates the influence of patient autonomy on doctors��� performance. Using a theory-driven laboratory experiment, I find that when the patient is not able to assess the doctor���s diagnostic precision, for those patients who are not fully compliant with doctors��� advice, doctors will reduce their investment of effort in the diagnosis. This reduction is the largest among those doctors who prioritize patients��� well-being. The experiment also investigates two institutional changes, communication and reputation, which both effectively improve patients��� well-being. This study contributes to experimental health economics by uncovering the potential detrimental effect of patient autonomy on a doctor���s performance and the patient���s health status.
The second essay explores the effectiveness of two punishment strategies for addressing the free-rider problem in public goods production. By varying the timing of punishment in a public good game, we differentiate between the Post-Punishment rule, expected to induce emotional arousal, and the Pre-Punishment rule, aimed at strategic considerations with minimal emotional impact. Pupil dilation data from eye trackers support our hypotheses, revealing that the Post-Punishment rule���s success relies on negative emotions, while the Pre-Punishment rule does not. This study sheds light on the role of negative emotions in punishment efficacy and introduces a novel punishment rule that operates independently of negative emotional responses within a group.
The third essay examines the trade-offs individuals make between money, honesty, and altruism through a sender-receiver game that allows truth-telling, selfish lies, and altruistic lies. We propose a theoretical model identifying five unique types of senders. Experimental findings show prevalent yet diverse patterns of trade-offs among these three domains of concern. This research adds to the literature on lying behavior by revealing varied preferences across moral domains and a widespread
propensity for costly altruistic lies