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Assessment of Corrosion Prevention and Mitigation Techniques for Concrete Bridge Decks in Texas
No full textCorrosion in reinforced concrete is a self-accelerating process. Once rust forms on steel due to cracks and environment factors, it expands in size, causing larger cracks. The corrosion in reinforced concrete bridge decks has resulted in significant economic losses. To repair and maintain the durability of bridges, the Texas Department of Transportation spends millions of dollars every year. This study provides a comprehensive study of corrosion mitigation methods, such as high-performance concrete (HPC), calcium nitrite corrosion inhibitor (CNI), linseed oil, silane, and epoxy-coated rebar, for concrete bridge decks throughout Texas. To assess the performance of the mitigation methods, 61 concrete bridges across Texas were selected for both field evaluation and laboratory experiments using concrete cores extracted from the bridges. The field evaluation included visual inspection and non-destructive evaluation, such as infrared thermography, ground penetrating radar, ultrasonic tomography, half-cell potential, and corrosion rate mapping. In the laboratory, experiments included surface resistivity, bulk resistivity, ultrasonic pulse velocity, water absorption, chloride content measurement, carbonation depth measurement, coating adhesion testing, and electrochemical impedance spectroscopy. Using the results from both field and laboratory evaluations, a decision-making tool for selecting corrosion mitigation methods in reinforced concrete, based on different environment conditions of Texas, was developed. The tool seeks to contribute to the formulation of a comprehensive strategy to control corrosion and reduce corrosion-related financial losses as much as possible. This research aims to provide various approaches for evaluating the performance of different mitigation methods applied to concrete bridge decks, as well as to determine the durability and effectiveness of the mitigation methods that have been in use on real bridges for an extended period
The White Atlantic: Finding South Africa in the American South, 1954-1966
No full textThe Citizens��� Council of America advanced what some historians call a ���segregationist foreign policy.��� ���Massive resistance��� to domestic desegregation during the 1950s and '60s pushed the Council to concern itself with foreign affairs, particularly the United Nations' criticism of South African apartheid. Council publications and television broadcasts show that the Council opportunistically reframed its rhetoric to match South Africa���s defense of apartheid as a system dedicated to local self-determination and combating communism. The Citizens��� Council mirrored this strategy, promoting segregation to stave off communist inroads and reinforce states��� rights, meaning self-determination
Evaluation of Multiple Approaches for Solidification Modeling of Advanced Nuclear Reactor Coolants
No full textThis dissertation focuses on developing and validating numerical tools for modeling solidification phenomena in advanced nuclear reactor coolants. The primary objective is to offer cost-effective alternatives to experimental studies and enable rapid simulation of multiphysics reactor transients. To achieve this, a hierarchical structured framework is established. High-fidelity models or experiments inform intermediate-fidelity data, which, in turn, provide training data for multidimensional coarse-mesh models capable of running on a single core and delivering fast results. The first phase of this research focuses on developing a solidification model using the Lattice Boltzmann Method (LBM) for 3D internal transient solidification modeling of Generation-IV nuclear reactor coolants. This model, based on the Total Enthalpy Model coupled with the Partially Saturated Method, addresses both high and low Prandtl numbers under laminar forced conditions. Key findings include the utility of the LBM total enthalpy Partially Saturated Method for solidification modeling, faster computational times compared to conventional Finite Volume Computational Fluid Dynamics (FV-CFD) methods for low Prandtl numbers, and the identification of stability limitations for high Peclet numbers.
In the second phase, we develop an intermediate-fidelity model based on a FV-CFD RANS enthalpy-porosity method, addressing high and low Prandtl numbers. We validate it against experimental data for high Prandtl numbers and against a high-fidelity LBM-LES model for low Prandtl numbers. Incorporating interface turbulence viscosity damping addresses RANS models��� tendency to overestimate heat transfer, enhancing their practical utility despite slightly reduced predictive accuracy compared to LES models.
In the third phase, we introduce a fine-to-coarse mesh upscaling technique enhanced by physics-based closure terms. Employing a data-driven strategy, we fine-tune the model���s closure coefficients utilizing the FV-CFD RANS intermediate-fidelity model on fine meshes. The calibrated coarse-mesh model reliably predicts essential performance metrics, including pressure drop, velocity profile, outlet temperature, and solid thickness distribution. This multidimensional approach marks a notable progression from conventional 1D methods, offering substantial time savings compared to fine-mesh models.
The highlights of this dissertation include (i) an innovative solidification model coupled with turbulence modeling based on LBM (ii) the validation and enhancement of an intermediate-fidelity RANS solidification model by incorporating a turbulence viscosity-damping source, preventing turbulence overproduction at the interface (iii) the development of a fine-to-coarse mesh upscaling solidification model, incorporating physics-based closure terms calibrated through a data-driven approach
Deciphering Cell Systems: Machine Learning Perspectives and Approaches for the Analysis of Single-Cell Data
No full textThis doctoral dissertation delves into the application of machine learning techniques in molecular biology, exploring gene expression regulation at the single-cell level and navigating the intricacies of cellular biology. The study specifically focuses on the utilization of modern neural networks to address cell-cell communications, gene function inference, and decipher protein expression. These applications aim to elucidate the complex interactions governing cellular behavior, as evidenced by the analysis of single-cell RNA sequencing (scRNA-seq) data.
In pursuit of these goals, I have developed and implemented advanced computational methodologies that combine systems biology and modern neural networks techniques. These methods are specifically crafted to manage the high-dimensionality and complexity of single-cell data, facilitating a more nuanced comprehension of genotype-phenotype relationships.
This research makes a significant contribution to the field of computational biology by proposing the use of neural networks to tackle the longstanding optimization problem in manifold learning. Furthermore, the study investigates generative models for learning gene regulatory networks and simulates gene knockout at the single-cell resolution. Lastly, the research delves into enhancing the interpretability of black box neural network models, applying them to multimodality data.
This research also contributes to the cell biology field by first providing an in-depth analysis of cell-cell interactions, highlighting how these interactions shape cellular behavior and influence disease progression. In addition, this research investigates gene function prediction, focusing on how gene knockouts can affect cellular phenotypes and their potential therapeutic implications. Lastly, this research looks into how gene expression patterns translate into protein expression and how accurately and interpretably this translation process can be predicted. This aspect of this research yields important insights into the functional implications of gene expression, which may be applied to the understanding of disease mechanisms and drug responses.
This research serves as a valuable resource because, in addition to the three introduced tools, it provides a comprehensive overview of state-of-the-art methodologies and their respective applications in the analysis of single-cell data within the recent years.
In conclusion, this doctoral dissertation represents a significant contribution to the field of computational biology and cellular biology by providing novel methods and insights into the genotype-phenotype relationships at the single cell level. These methods and discoveries not only improve our understanding of cellular behavior, but also pave the way for the creation of novel therapeutic strategies, thereby potentially enhancing our ability to combat a wide range of diseases
Optimizing Infectious Disease Control: Strategies for Social Separation and Vaccine Allocation with Equity Consideration
No full textAs global threats from infectious diseases intensify, as highlighted by the COVID-19 pandemic, the urgency to enhance control measures becomes evident. Strategies such as social separation and vaccine allocation are pivotal in disease management. However, despite extensive research, many models still fall short. They rely on oversimplified assumptions such as population homogeneity and a single-wave pattern of infection spread. Current research still lacks comprehensive approaches in addressing the effective and equitable implementation of these strategies in more complex, realistic scenarios.
To address these gaps, we explore various models for social separation and vaccine distribution, considering individual-specific factors and the multi-wave nature of pandemics observed in reality. Focusing on efficiency and equity in disease mitigation, we uncover key components of an optimal infectious disease control strategy. These insights help us to formulate effective algorithms, understanding the trade-offs between efficacy, costs, and fairness. Our work also leads to the development of an efficient, fair clustering algorithm that not only performs well in our disease mitigation context but also excels across various datasets.
Case studies underscore the advantages of strategies tailored to specific individual information and dynamic behavior. Such approaches are more effective, cost-efficient, and equitable than traditional disease control measures. The fair clustering algorithm we developed further demonstrates its advantages over benchmark algorithms
International Trade Impact on Milk Product Market in the U.S. and LCA with Economic Analysis on Converting Lignin Waste to Sustainable Products
No full textThis dissertation investigates some economic issues regarding international trade and the production of byproducts in lignocellulosic ethanol production. This work is reported in three essays.
The first essay addresses how recent expansions in international trade affect Class I spatial milk price differentials in the U.S. Five international trading scenarios were simulated using a milk sector movement and processing model. The results reveal notable regional differences in the spatial characteristics of farm-level raw milk prices. We find the greatest effects are in the Eastern U.S. where we see significantly higher prices. We also see domestic milk price disparities, in areas like Idaho and New Mexico. Furthermore, the influence of international trade is clearly seen in prices of U.S. milk products that are exported or imported, especially for the products like Cheddar Cheese and Butter. The study emphasizes the need for a possible update in spatial milk price differentials considering the growing impacts of a globally interconnected market.
The second essay examines the net greenhouse gas emissions and market penetration implications of using the lignin byproduct from a lignocellulosic biorefinery to make carbon fiber. The results show that using lignin as a precursor for producing carbon fiber leads to a reduction in CO2 emissions compared to the conventional process of producing carbon fiber. We also analyzed the price and size of the market if the lignin-based carbon fiber was entered into existing carbon fiber markets under various elasticities. Here we found large scale production would lead to substantial carbon fiber price declines.
The third essay examines alternative choices for lignin utilization across a set of alternative downstream products. Namely, lignin can be used to make carbon fiber, asphalt binder modifier, PHA, and biodiesel lipids, when this is done our analysis finds a number of substantial economic and environmental benefits, most notably in reducing CO2 emissions. Market analysis under various scenarios, including the consideration of carbon emission prices, indicates that the optimal market entry of these products depends on production costs and carbon pricing. The findings suggest a strategic approach to lignin utilization, where prioritizing lignin-based carbon fiber production and adjusting outputs based on carbon emission costs can lead to maximum profitability while contributing positively to environmental sustainability
Phylogeography and Systematics of the Sand Shiner, Notropis stramineus (Cope, 1865)
No full textNotropis Rafinesque, 1818 is a species-rich genus of North American minnows that has been demonstrated to harbor ���cryptic��� diversity. The Sand Shiner, Notropis stramineus, is one of the most widespread North American minnows. Various subspecific classifications have been proposed for the Sand Shiner, the most widely accepted of these comprising two subspecies, N. s. stramineus and N. s. missuriensis, based largely on minor differences in scale-row counts between individuals inhabiting tributaries to the Great Lakes, upper Mississippi River and Texas Gulf Coast river systems (N. s. stramineus) and those inhabiting the Missouri and Arkansas River systems (N. s. missuriensis). Analysis of three loci revealed that the Sand Shiner, N. stramineus comprises five clades, and further, other members of Notropis were recovered between clades of N. stramineus, though gene tree discordance created difficulties for determining species boundaries. Ultra-conserved elements (UCEs), enriched from each clade of N. stramineus, related species, and several outgroup taxa, were then analyzed. All least-inclusive clades recovered were identical across analyses and corresponded to clades recovered in Chapter II, however, relationships between the clades differed. In contrast to Chapter II, most clades comprising N. stramineus were monophyletic, and are here termed the N. stramineus species complex. As in Chapter II, a separate clade of N. stramineus was recovered outside of the clade containing the N. stramineus species complex as the sister taxon to a species of Notropis not previously considered to be closely related (N. chihuahua). These results demonstrate that N. stramineus is likely comprised of five distinct evolutionary lineages, which are diagnosed and described (clades B1, B2 and D) or redescribed (clades A and C) in the final chapter, with species diagnosed using characters derived from aspects of pigmentation, body and head shape, tuberculation, and osteology
Second-hand Illegality: Bureaucratic Exclusion and Resource Inequality in College Financial Aid for U.S.-born Latina/o Children of Undocumented Parents
No full textThis study presents a systematic analysis of the bureaucratic obstacles confronted by U.S.-born Latina/o children of undocumented parents when seeking financial aid for college. It delves into the unique challenges these students face during the financial aid application process, where parental information is a pivotal factor. Methods: Employing a semi-structured interview approach, I engaged with 15 participants who shared their experiences with bureaucratic barriers when parental information was requested. The study unveils the concept of "Second-hand illegality," where participants found their own access to resources for education obstructed due to their parents' undocumented status. This phenomenon became most pronounced at three key junctures within the Free Application for Federal Student Aid (FAFSA) form: (1) when the application necessitated parental social security numbers, (2) when it required parent income details, and (3) when it demanded parent signatures for submission. Consulting these points compelled participants to employ innovative strategies to surmount the obstacles. This research underscores a fundamental structural issue within the higher education system, focusing on a demographic often overlooked in immigration literature. The strategies devised to overcome the bureaucratic hurdles posed by the FAFSA lead to outcomes mirroring those experienced by their undocumented parents, including rejection, denial, or limitations on access to crucial resources, services, and benefits. In a broader context, this study highlights the need for systemic changes and policy reform to ensure equitable access to higher education for all U.S. students, regardless of their parental immigration status
Learning from Successful Qatari Women in Corporate Management: Stories of Career Development and Lived Experiences
No full textThe purpose of this study was to explore Qatari women���s career development journey to management within the context of Qatar���s unique culture, honoring ancient traditions while ambitiously entering modernity. For Qatari women to be equally represented in corporate management they must be motivated and aspire to compete for influential positions in gender-mixed environments. This study used a qualitative, life history approach to examine their life experiences that have influenced their career development, in gender-mixed work environments. A two-part data analysis approach was conducted consisting of (a) the construction of a case story that reflected the biographical, life history of each participant as it related to her career development, and (b) inductive, cross-case thematic analysis. The major themes that emerged from this process concerned the critical career development stages that contributed to the personal and professional growth of participants and had a direct impact on their career progression. The four major themes identified were: (a) early beginnings; (b) quest for higher education; (c) establishing and managing career; and (d) strategies for sustained career success.
The participants��� early beginnings centered around their family and were heavily influenced by their father���s support. The love and care shown by their families enabled them to adapt to strong guardianship by showing respect, honor, and obedience to their families. During their quest for higher education, participants were guided by their families��� expectations for educational attainment. They developed resilience in the face of challenges, which altered their original plans for university and caused them to pivot and reconstruct their vision for a university experience. Upon finishing university and entering the workforce, participants��� greatest challenge was assimilating into a gender-mixed work environment. In this new environment the women faced gender bias, ageism, and had to confront societal judgement, which had a strong presence in their work environments. The women worked hard to prove their professional credibility by developing their interpersonal skills and finding their professional voice. Predominant enablers of their success were having a high-risk, growth mindset, managing positive relationships with their supervisors and mentors, and finding a meaningful purpose to drive their ambition and success
Exploring the Impact of Catalyst Supports on Hydrogenolysis of Polyolefins over Cobalt-Based Catalyst
No full textThe persistent utilization of plastics and inadequate disposal methods post-consumption are responsible for causing numerous ecological challenges on a global scale. In recent years, hydrogenolysis has been studied as a promising route to chemically repurpose polypropylene and polyethylene, which are some of the most widely used plastics. In this study, polyethylene is subjected to hydrogenolysis, utilizing cobalt-based catalysts on three supports: Zinc Zirconium Oxide (ZnZrO), Cerium Oxide (CeO2), and Titania (TiO2). The reaction is conducted under batch conditions at 275��C and 30 bar H2 pressure, with reactions performed for periods ranging from 30 minutes to 32 hours. Our findings reveal that cobalt supported on ZnZrO exhibits a high yield of liquid phase alkanes (C5-C30) up to 67%. The evolution of products over time also aids us in understanding the influence of the support material on catalyst performance, we propose likely reaction routes followed for hydrogenolysis carried out in the case of Co/ZnZrO and Co/TiO2. A loading study is also carried out to assess the impact of active metal density on reaction product yield and selectivity. Further, the efficacy of Co/ZnZrO is examined by using it to carry out hydrogenolysis of a post-consumer LDPE bottle, yielding results largely consistent with those obtained from the model PE substrate employed in our investigation. These outcomes underscore the pivotal role of support materials in the hydrogenolysis reaction and contribute to the mitigation of challenges stemming from inefficient plastic disposal, providing a more feasible way of upcycling plastics