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Comprehensive Validation of Semi-Submersible Floater Dynamics: A Coupled CFD-FEM Approach with Iterative Wave Adjustment
No full textThis dissertation presents the development and application of a numerical wave tank based on an in-house Computational Fluid Dynamics (CFD) program, Fintie-Analytic Navier-Stokes (FANS). The CFD solver, featuring overset (Chimera) grid capability and dynamic memory allocation, enables efficient computation of multiple structured grid blocks with a large capacity for data interpolation between overset grids.
An analytic Directional Wave Simulation (DWS) program is coupled with the Navier-Stokes solver at the wave maker location. Numerical wave parameters, including wave elevation and velocity are transmitted from the DWS block to the CFD domain via overlapping grids. To achieve a calibrated numerical wave spectrum at target location, an iterative wave adjustment method is developed, utilizing a 4-wave decomposition scheme based on harmonics separation theory.
The free surface in the CFD domain is captured with the level set method. 5th-order Weighted Essentially Non-Oscillatory (WENO) and 2nd-order Alternative Direction Implicit (ADI) schemes are employed for spatial and time discretization of level set governing equations. To mitigate wave reflection at domain boundaries, a forcing zone method using damping source terms in the governing equations is introduced.
A nonlinear Finite Element Method (FEM) mooring model named MOORING3D is developed to investigate hydrodynamic responses of mooring systems. Coupled with the FANS program, this model explores the global performance of moored floating structures under various environmental conditions. A six-degrees-of-freedom (6-DOF) motion solver is integrated into the FANS program to update the motion of the floater.
A robust verification procedure based on the least-squares Richardson extrapolation method is introduced to estimate the discretization uncertainties of the numerical simulations. The convergence study in this research focuses on spatial and temporal discretization uncertainties.
Data from a comparative study at 2020 ISOPE conference is utilized to assess the wave generation and iterative wave adjustment method. Model tests from this comparative study investigate the nonlinear interactions of steep focused waves with a fixed cylinder. Wave elevations at target locations and wave slamming loads on the cylinder are compared with the experimental measurement and other numerical solutions for validation. The results highlight the positive effect of the iterative adjustment method on highly nonlinear numerical wave generation.
Verification and Validation (V&V) studies are conducted on the coupled CFD-FEM program using a Floating Offshore Wind Turbine (FOWT) platform model. Convergence studies include pitch free decay and regular wave tests, which are parts of the OC5 project (Offshore Code Comparison Collaboration, Continued, with Correlation project). The numerical wave profile and 3-DOF responses of the platform are validated against model test measurement and other numerical solutions. The agreement between the coupled numerical solution and the experiment validates the method.
The coupled numerical solution is employed to investigate hydrodynamic responses of the plat-form under highly nonlinear irregular wave conditions, addressing the importance of calibrating the wave to the target spectrum. Short-duration extreme wave cases and a long-duration 3-hour irregular wave case are conducted to comprehensively evaluate the integrated solver���s performanc
Cryo-Em Structures of Single-Strand RNA Pepeviruses and the Interaction with Their Host Receptor, Type IV Pilus
No full textPositive-sense single-stranded RNA bacteriophages (ssRNA phages) have recently been reclassified because of the increase in the number of genomes discovered in metagenomes and metatranscriptomes. ssRNA phages infect gram-negative bacteria and are known to be structurally and genetically simple RNA viruses. Their infectivity is dependent on host retractile pili. Despite the discovery of ssRNA phages since 1960, only the structures of mature virions for F-pilus-specific E. coli phage (coliphage) MS2 and Q�� were solved by cryo-electron microscopy (cryo-EM). Mature virions of coliphages are composed of a single copy of maturation protein (Mat) and a capsid containing a single strand of genomic RNA (gRNA). Mat is an essential protein required for phage adsorption onto pili. However, ssRNA phages are diverse, as they infect several gram-negative bacteria and target different types of pili. Pseudomonas aeruginosa pepeviruses, PP7 and LeviOr01, infect their hosts through type IV pili (T4P). Here, we present the cryo-EM structures of pepevirus PP7 and LeviOr01, which are distinct from those of coliphages. These T4P targeting phages unexpectedly contain two Mat proteins in mature virions. One of the Mat proteins is internalized (MatIN) inside the virion, whereas the other is exposed (MatEX) for T4P binding. LeviOr01 exhibits plasticity in its assembly through Mat, in which particles with defined gRNA containing only a single MatIN and no Mat proteins are observed. Although mature PP7 virions always consist of two Mat proteins, a region of PP7-gRNA surprisingly displays high plasticity by adopting several conformations. This discovery underlines the importance of structural studies in mature virions and suggests that the structural simplicity of ssRNA phages might require reconsideration. We also solved the complex structure of PP7 bound to purified T4P from PAO1 to better understand host recognition and the entry mechanism. These findings provide insights into the exploitation of pepeviruses for phage therapy and biotechnological applications
Using Antibiotic Alternative Feed Additives to Improve Overall Duck Growth Performance and Welfare
No full textGrowing ducks with optimal efficiency, health, and welfare has become of paramount importance. While numerous antibiotic alternatives (AA) have been investigated in other poultry species to reach these goals, there has been limited research on Pekin ducks. Several experiments were conducted to determine the effects including (i) organic acids (OA), (ii) oregano oils (OO), and (iii) direct fed microbials (DFM) in ducks. Experiment 1 evaluated duck growth, health, and welfare with water supplementation of OA and OO. The OA and OO improved feed conversion ratio (FCR) and body weight (BW) (P 0.05). Experiment 2 evaluated optimum inclusion rates of a commercially available (DFM) feed additive. Duck growth, stress, fear response, welfare, and litter conditions were evaluated. Results conveyed CON had higher (P 0.05) compared to CON. Experiment 3 evaluated the use of the same treatments as Experiment 2 except for the addition of a prolonged heat stress period added during the grow out. Results indicated BW and FCR compared to CON (P > 0.05) was higher than all other treatments. Total white blood cell counts were lower than CON (P < 0.05) compared to all other treatments in the DFM heat stress trial. Heterophil counts, H/L ratio, and total plasma corticosterone levels were also lower than CON (P < 0.05) compared to all other treatments reviewed whether through water supplementation or dietary supplementation. Lymphocytes counts were higher than CON (P < 0.05) compared to all other treatments. Villus height presented differences (P < 0.05) in all other treatments compared to CON. In conclusion, these experiments indicate that Organic Acid, Oregano Oils, and Direct fed microbials can be used to improve duck growth, feed efficiency, stress susceptibility, and bird welfare
An Augmented Machine Learning Approach for Real-Time Terramechanics Modeling
No full textThe purpose of this research was to develop a novel method based on Gaussian process models that can be combined with information from detailed models and field data, such that the model is capable of carrying out real-time simulation of the tire-terrain interaction. The aim of this approach is to be able to provide feedback on tire sinkage, slip, traction, and side forces to a virtual simulator for autonomous off-road vehicles. Such simulators are essential for training autonomous vehicles without the need for extensive field tests. The use of a simulator reduces the cost of autonomous vehicle training and allows for easy modification to the training/testing environment. The present approach is based using precomputed look-up tables, typically based on a Bekker terramechanics model, or a simple Coulomb friction model to determine tractive capabilities. While these provide quick information to be used in vehicle dynamics calculations, they lack the quality and quantity of information required for dynamic off-road conditions under widely different terrain conditions. Furthermore, the model is capable of accommodating disparate data sources with different ranges of validity and also take into account the uncertainties in the predictions.
In this thesis, the efficacy of the hybrid approach is demonstrated by combining a modified Bekker terramechanics model with finite element analysis (FEA) simulations using a Gaussian process regression (GPR) model that is capable of predicting tire forces and sinkage in off-road conditions. The Bekker-style model is valuable due to its simplicity, but it lacks dynamic loading information. While the FEA model provides valuable information about the full tire-terrain interaction it is computationally very expensive and unsuitable for real-time simulations. Therefore, a GPR model is trained to predict the difference between the steady-state information provided by the Bekker-style model and the full response provided by the FEA. Then the Bekker-style model and trained GPR model can be deployed in tandem to predict full response (forces) in a real-time applications such as off-road autonomous driving
Assessing Primate Eye Morphology
No full textEye morphology varies widely across primates with species exhibiting a range of eye colors and shapes, but we do not yet have a full understanding of what drives this diversity. We tested whether primate eye morphology is correlated with social factors, ecological factors, or both. We did so by examining the eye coloration and shape of 68 primate species (spanning great apes, lesser apes, prosimians, and African, Asian, and South American monkeys). We used modern methods of analyzing animal coloration that account for the specific visual system of each species. We found that primate eye coloration is correlated with both social and ecological factors. Primates with more discriminable gaze have larger social group sizes and canine size dimorphism. Primate eyes that have greater red chromaticity are associated with more open habitats. And, primates with more elongated eyes had larger body mass, lived in more open habitats, had larger group sizes, and lived closer to the equator. Our ancestral trait reconstruction suggested that the ancestral primate had moderately elongated eyes with brown irises and sclera. Our results suggest that both social and environmental factors have impacted the evolution of primate eye morphology
Nature of Science in Science Education: Establishing Common Ground
No full textA deep and robust understanding of the nature of science (NOS) has been increasingly recognized as a core component of any form of meaningful scientific literacy. However, little progress has been made with NOS teaching and learning over the past century. This has become an increasingly problematic situation as citizens have struggled with numerous high-profile socioscientific issues over the past several decades (e.g., climate change). Unfortunately, scholars��� discordant approaches to NOS in science education have created an acrimonious environment that has likely impeded efforts to promote attention to NOS teaching and learning. This problematic state of affairs is exacerbated by a lack of clarity regarding the specific ways that NOS understanding affects SSI decision-making, and a dearth of quantitative instruments that can provide valid and reliable inferences about respondents��� understanding of NOS constructs. This dissertation research contributes to the improvement of NOS teaching, learning, and research by: (1) Identifying the major themes that exist within the NOS approach literature, along with the areas of agreement and disagreement related to each theme; (2) Determining the NOS constructs related to climate change beliefs and attitudes; and (3) Creating a novel, high-resolution, quantitative NOS instrument that targets a specific NOS construct (i.e., methodological pluralism). The thematic analysis of NOS approach literature yielded seven central themes that contained numerous areas of agreement and disagreement that can help to provide order to future scholarly discussions. The examination of NOS connections to climate change beliefs and attitudes within the literature identified 15 relevant NOS constructs that provide an important focal point for science educators, communicators, and researchers. Instrument development efforts resulted in a tool that can provide high-resolution, valid, and reliable inferences about students��� views regarding methodological pluralism. While further refinement of the instrument is needed, this work represents a significant advance in quantitative NOS assessment. Collectively, the research related to this dissertation has addressed several important gaps in the field of NOS education, and establishes an important future line of research
Essays on Belief Updating and Decision-Making
No full textMy dissertation consists of three chapters on belief updating and decision-making.
The first chapter, coauthored with Marco Castillo, aims to understand how to mitigate negative economic consequences that can arise when individuals have biased beliefs about their surroundings. Specifically, we design two task assignment rules in teams based on a theoretical framework of Heidhues et al. (2018), and investigate their causal impact on task allocative efficiency. Using a series of laboratory experiments, we find that equally biased beliefs about team members��� productivities can lead to different efficiency outcomes depending on task assignment rules. The study highlights the importance of institutional designs that ensure economically desirable outcomes even in the presence of biased beliefs.
The second chapter, coauthored with Andy Cao, Marco Castillo, and Ragan Petrie, examines how non-pecuniary costs incurred during college impact college major choices. We conduct a randomized controlled trial to provide truthful information on major-specific teaching quality and inclusive climate to college freshmen and sophomores at Texas A&M University. We find significant effects of teaching and climate information, especially for choosing among business and economics majors. We also find that information has affected the college major choices of women more than it has for men. Our study shows that non-pecuniary aspects of human capital accumulation experienced during college can have an impact on the allocation of talent across fields.
The third chapter, co-authored with Hyundam Je, presents novel evidence that the timing of informativeness affects the level of motivated reasoning. Building upon the primacy effect, our framework predicts that receiving a signal before learning about its informativeness can exacerbate the extent of motivated reasoning compared to receiving it afterward. Our online experiment finds supporting evidence for this prediction. When participants learn about informativeness after receiving a signal, there is a stronger tendency for them to interpret the signal in a way that reinforces their preferred beliefs. These findings suggest the practical importance of structuring information as a strategy to mitigate motivated reasoning in information transmission
Analytic and Semi-Analytic Calculations for Color Glass in the Weak Field Limit
No full textThe classical field approximation for color glass condensate can be solved using numerical methods and recursive analytic series solutions. The recursive analytic solution is known to have a resummation in Fourier space in the so called weak field limit. Based in this limit, the proper spacetime dependence of quantities related to the gluon two point function are derived. Namely, the gluon energy momentum tensor and corresponding angular momentum tensor, the initial motion of the nuclei after the collision, and the isotropic momentum broadening coefficient are computed.
The McLerran-Venugopalan model is one realization of color glass condensate to which our calculations can be applied. In many cases it can be used to obtain closed analytic expressions, however they are susceptible to UV and IR divergences. An alternative model which maintains UV regularity and softens the IR divergence is thus proposed. The UV region in this new model is regulated by accounting for local charge correlations in the transverse plane. The leading IR divergence is cured by enforcing global color neutrality. Analytic expressions are obtainable in this new model in the form of infinite series.
Novel insights from this work include an analytic understanding of the full time evolution of important physical quantities like energy density, pressure, and momentum broadening, including their late-time behavior; a scheme to systematically include non-constant color charge densities needed to compute realistic nuclei; a numerical understanding of the deceleration of nuclei in collisions, and (for the first time) a calculation of the transverse motion of nuclei
mRNA-Encoded Anti-VapA Monoclonal IgG1 for Passive Immunization of Foals Against Rhodococcus equi
No full textPneumonia caused by Rhodococcus equi is an important cause of disease and death in newborn foals. Neonatal foals are most susceptible to infection because their na��ve, immature immune responses fail to protect against inhaled R. equi, which is ubiquitous in their environment. Virulent R. equi strains express the virulence-associated protein A (VapA) that is necessary to cause disease in foals. Passive immunization with transfusion of hyperimmune plasma (REHIP) protects foals against R. equi pneumonia; potency is assessed by anti-VapA titers. REHIP transfusion, however, is expensive and risky for foals; REHIP products also vary markedly in anti-VapA activity. Monoclonal antibodies (mAbs) provide superior specificity and consistency, but costs and complexity limit feasibility. In vitro transcribed (IVT) mRNA encoding mAbs (mRNA-mAbs) enables safe, ondemand mAb production within the patient, including in the lungs following nebulized delivery of mRNA-mAbs. Thus, our objective was to generate IVT mRNA encoding an equine mAb of the IgG1 sub-isotype against VapA for intrapulmonary passive immunization of neonatal foals. The first chapter provides a literature review summarizing current knowledge of mRNA-mAb for passive immunization and its promise against rhodococcal pneumonia. The following chapters describe studies conducted to demonstrate proof-of-principle for aerosolized IVT mRNA expression in foals. First, we conducted a pilot study demonstrating safe expression of aerosolized IVT mRNA encoding a reporter protein in the guttural pouches and lungs of foals. Next, we investigated intrapulmonary expression of a functional mRNA-mAb. VapA-specific memory Bcells were isolated from a hyperimmunized adult horse and single-cell sequenced to identify an IgG1 mAb sequence. Expression of IVT mRNA encoding the mAb in equine lung cultures produced a mAb specific for virulent R. equi. A mRNA-mAb was then formulated in a polymer-based carrier and nebulized to 12 neonatal foals, resulting in safe, consistent mAb expression for up to 12 days. Expressed mAb within the lungs specifically recognized both VapA and virulent R. equi. This project represents the first mRNA-mAb developed for equine passive immunization and the first mRNA-mAb delivered to neonatal lungs in any species. This platform holds great translational potential for veterinary and human medical applications, especially for delivering near-immediate protection to neonatal airways via neutralizing antibodies
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