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A Numerical Study on the Multiline Ring Anchor in Sand
No full textThe Multiline Ring Anchor is an anchor solution designed to meet the growing demands of the offshore renewable energy sector in the country. It has been presented as an alternative to conventional anchor systems with its enhanced engineering efficiency and financial sustainability. The present doctoral work offers an assessment of the geotechnical performance of the anchor, to aid its transition from theory to practice.
A numerical study was undertaken to achieve a comprehensive understanding of the behavior of the anchor as a support system for arrays of offshore floating wind turbines. Its response under monotonic load conditions from different mooring systems is simulated using finite element analysis. The study was primarily divided into two phases ��� the first focused on the purely vertical capacity of the MRA in drained sand, with an emphasis on its end bearing behavior; and the second studied the response of the MRA when subjected to an inclined tensile pull while exploring the effects of the combination of loading conditions on it. Additionally, as a preliminary step in the analysis of the anchor under partial drainage conditions, a hypoplastic constitutive law is explored as an alternative to the Mohr Coulomb model.
The study finally presents a simple empirical model to estimate the vertical and the inclined ultimate capacities of the MRA in drained sands, along with a means to determine the optimum loading conditions, as functions of the padeye location and load inclination angle
Spatial Patterns, Drivers, and Impacts of the Urban Land Expansion in Nigeria from 1985 to 2015
No full textUrbanization is reshaping landscapes worldwide, posing considerable challenges to ecosystems, climate patterns, and resource utilization. This dissertation studies the spatio-temporal patterns of urban land change, its drivers, and its implications for biodiversity and flood exposure in Nigeria from 1985 to 2015. A pivotal aspect of the methodology is the evaluation of global urban land cover products to facilitate the understanding of urban land expansion in a context where specific national data on land cover is scarce or not available. This evaluation revealed each product's ability and limitations in accurately reflecting the reality of Nigeria's urban development. The specific findings of this research also reveal significant environmental implications, such as the loss and fragmentation of natural habitats and the exposure of urban land to flooding. Thus, the dissertation provides valuable insights that can inform urban management, policy formulation, and conservation strategies in developing urban landscapes, that are particularly tailored to Nigeria, but also indicative of other rapidly urbanizing countries across Sub-Saharan Africa
Free-Form Dithering
No full textIn this paper, we will present free-form dithering, a function-based dithering parallel dithering framework. The free-form dithering framework is appropriate to use in real-time applications it is straightforward to implement its parallel algorithms with GPU-based shader languages. This framework is implicit based on the sense that we construct hatching curves by altering the shapes of hatching curves using isocurves that are defined by type distance functions. Using distance functions allows us to precisely control the frequency of isocurves
A New Galerkin Quadrature Method Without the Requirement of Matrix Inverse
No full textA new method of forming the scattering source of the Boltzmann neutron transport equation for anisotropic scattering is proposed through the use of Grahm-Schmidt orthogonalization. This new method builds upon two previous methods but differentiates itself by lowering the computational burden of the calculation and potentially admitting more general types of quadratures. It is hoped that this method will gain greater traction in codes solving the Boltzmann neutron transport because of its lower cost and wider applicability. The Galerkin Quadrature method is required for highly anisotropic scattering, which characterizes charged particle transport, and was originally developed for this purpose. This thesis presents the sum of research into the new Galerkin Quadrature method in the form of a paper submitted to the Journal of Nuclear Science and Engineering, 2024. The derivation of all 3 Galerkin Quadrature methods are defined, the test problems are stated with their results, and conclusions drawn. An additional summary section details the conclusions of the overall work
Centering Cemeteries in Environmental Justice: Observing Community Connectivity in Historic Texas Black Cemeteries
No full textThis research seeks to create new knowledge on Black cemeteries by employing methodologies that are innovative within the field of urban planning. Drawing from concepts borrowed from Black Geographies and Anthropology, particularly Participatory Geographic Information Systems (PGIS) methods, this study aims to delve into the intricate dynamics and significance of Black cemeteries within their respective communities. The significance of Black cemeteries transcends their role as mere burial sites; they serve as crucial spaces for memorialization, historic preservation, and community cohesion. Over generations, these cemeteries have acted as repositories of collective memory, fostering a sense of continuity, and belonging among community members. Moreover, they function as dynamic hubs of activity, where rituals, events, and ongoing preservation efforts contribute to the creation of a shared sense of space and identity. Furthermore, the interconnectedness of Black cemeteries unveils a broader network of stewards and community members dedicated to place-making and heritage preservation. These networks facilitate land-use planning and address environmental justice issues by promoting resource sharing and skill exchange among communities. This research highlights the relevance of local histories and the engagement of local stewards in the preservation and management of Black cemeteries. However, the primary contribution lies in the incorporation of local knowledge into urban planning practices related to cemetery management. It emphasizes the importance of recognizing and valuing the intrinsic significance of these cemeteries within the context of environmental justice movements. In conclusion, safeguarding and advocating for the preservation of Black cemeteries is not merely an act of historical conservation but a fundamental aspect of social and environmental justice efforts. The utilization of geo-humanities as a tool in this research allows for a nuanced understanding of memorialization, place-making, visibility, accessibility, and vulnerability at the granular level, as evidenced through two case studies
A Characterization of the Vertical Structure and Mixing of the Eastern Mediterranean Sea
No full textObservational data collected by THEMO (The Texas A&M - University of Haifa Eastern Mediterranean Observatory) is used to characterize the seasonal variability of the water-column to understand the vertical structure and vertical mixing of the Levantine Basin in the Eastern Mediterranean Sea. Previous studies have shown the marginal Eastern Mediterranean Sea is characterized by hypersaline waters, strong water-column stratification, and regular seasonal atmospheric patterns. THEMO is composed of two surface buoys located off the coast of Haifa, Israel: one shallow buoy (water depth of 125 m; 10 km from shore) in the coastal zone of the Levantine Basin, one deep buoy (water depth of 1430 m; 60 km from shore), and one StandAlone McLane Moored Profiler (MMP), which is deployed close to the deep buoy. These instruments and buoys provide in-situ near real-time subsurface physical oceanographic observations and atmospheric observations of the Eastern Mediterranean Sea. The objectives of this research are: 1) to characterize and identify the processes that force the seasonality of the surface mixed layer depth, 2) to quantify the mechanisms that drive the hydrographic variability of the upper (surface to 1400 m depth) water-column, and 3) to categorize the stability processes of the Eastern Mediterranean Sea upper water-column using Turner Angle (Tu). Results show that the mixed layer depth varies seasonality from 250 m in Winter to less than 85 m in non-Winter months and is correlated with relatively stronger winter wind speeds (average of 7.12 m/s (Winter) to 4 m/s (non-Winter)). The upper 100 m of the water-column also experiences warming of 2 degrees C during Winter due to enhanced downward mixing of warm surface water with cooler subsurface water. Statistical analysis using empirical orthogonal functional (EOF) analysis shows that outside Winter months, variance in the principal component time-series is most correlated with the geostrophic current direction and accounts for about 50% of the total variance of water-column temperature and salinity. Characterization of water-column stability shows stable waters (-45 degrees < Tu < 45 degrees), i.e., no overturning, are most likely to occur in the upper 200 m of the water-column, and double diffusive mixing through salt fingering occur in waters below the mixed layer depth. The depth of salt fingering and stability are similar to other areas of the deep Eastern Mediterranean Sea and mid-latitude marginal seas of the world ocean
Shaping Human Capital and Socioeconomic Outcomes: The Impacts of Grade Retention, Lead Exposure, and Social Media Rhetoric
No full textMy dissertation consists of three essays on the topics of grade retention, lead exposure, and social media rhetoric. In the first chapter, I provide the first causal evidence of the effects of grade retention on the labor market outcomes using Texas��� policy of retaining third graders who fail a reading test. The fuzzy regression discontinuity design estimates show that third-grade retention significantly reduces adult earnings. Although the policy aims to improve academic achievement, the results demonstrate that third-grade retention lowers high school graduation rates without improving college outcomes and aggravates absenteeism and violent behavior.
In the second chapter, coauthored with Andy Cao and Jason Lindo, we investigate whether Donald Trump���s "Chinese Virus" tweets contributed to the rise of anti-Asian incidents. We find that the number of incidents spiked following Trump���s initial ���Chinese Virus��� tweets and the subsequent dramatic rise in internet search activity for the phrase. Difference-in-differences and event-study analyses leveraging spatial variation indicate that this spike in anti-Asian incidents was significantly more pronounced in counties that supported Donald Trump in the 2016 presidential election relative to those that supported Hillary Clinton. We estimate that anti-Asian incidents spiked by 4000 percent in Trump-supporting counties, over and above the spike observed in Clinton-supporting counties.
In the third chapter, coauthored with Thao Duong, we analyze the long-term effects of low-level lead exposure during early childhood from Kindergarten through grade three on educational achievement and earnings. Utilizing the unexpected decline in lead emissions following the reduced operation of piston-engine aircraft after the 9/11 attacks as a natural experiment, combined with detailed individual-level administrative data from Texas ERC, we employ both difference-in-differences and instrumental variable techniques to identify the causal impact of lead exposure on various student outcomes. Our findings reveal that even minimal increases in lead exposure, measured in micrograms per cubic meter, are associated with significantly decreased probabilities of high school graduation and post-secondary enrollment in public universities or community colleges. Moreover, we observe that lead exposure adversely affects children by diminishing their future earnings in the labor market
Structural Composite Electrode for Space Applications
No full textStructural batteries offer a solution for more range-efficient vehicles with its multifunctional ability to hold mechanical load and store energy. The earth���s atmosphere and space environment require vehicles and satellites to have structures which are sturdy against potential environmental debris collisions and able to withstand low temperature. This thesis focuses on the material processing and electrochemical performance of a multifunctional structural composite electrode which consists of carbon fibers for structural reinforcement and a structural biphasic bicontinuous electrolyte (SBBE) for the composite matrix. The SBBE-coated carbon fiber versus lithium half-cell is studied in coin cell configuration. The solid biphasic bicontinuous electrolyte is made from lithium bis(trifluoromethanesulfonyl)imide salt, diglyme, and fluoroethylene carbonate for the liquid electrolyte ionic-conducting phase and resin for high modulus phase.
The effect of the pre-cured volume of SBBE (i.e., volume of SBBE pipetted on top of carbon fiber fabric prior to curing) on the electrochemical performance of the carbon fiber versus lithium foil half-cell in coin cell configuration was studied. After the solid biphasic electrolyte is cured as a layer on the carbon fiber fabric composite electrode, electrochemical characterizations were performed on structural composite electrode half cells with pre-cured SBBE volumes ranging from 25 to 100 ��������. Results indicated that the optimal structural battery volume is 50 �������� because it has the highest electrochemical charge and discharge capacity for the structural composite electrode versus lithium metal foil half-cell at 180 mAh/g for the first cycle, the lowest charge transfer resistance from the electrochemical impedance spectra, and relatively the highest anodic peak when comparing 5th cycle cyclic voltammograms of structural composite electrode with pre-cured SBBE volumes ranging from 25 to 100 ��������. Future work includes testing samples with biphasic electrolyte coated on desized carbon fiber tows on an in-situ electrochemo-mechanical coupling machine
A Climate Smart Agricultural Productivity Assessment of Smallholder Women Farmers in Farming Associations in Nigeria: A Mixed Methods Study
No full textThe world is plagued with multiple planetary threats of rising food insecurity, COVID-19 pandemic, aggravated conflicts, shrinking natural resources and worsening climate crisis. Smallholder women farmers (SWFs) fare even worse in Africa than their male counterparts due to limiting opportunity structures stemming from gender biases and discriminating societal norms. This mixed methods research assessed the interaction of climate smart agricultural practices (CSAPs) and agricultural productivity among SWFs in Nigeria using the climate smart sustainable livelihoods framework.
My findings provide evidence on the levels of use of CSA among SWFs and their agricultural productivity demonstrated by their state of empowerment. The study employed a convergent mixed-method design, collecting data from SWFs through structured interviews (n=196) and focus group discussions (six groups), which informed the quantitative and qualitative strands of the study respectively. Participants were mutually exclusive of the two strands of study. Data was analyzed using descriptive and inferential statistics, rich thick description, thematic analysis, patterns, themes, and representative quotes. Findings from the quantitative strand converged with the qualitative strand in a joint display of data.
The study revealed the most preferred CSAP used by SWFs is mixed cropping while the least used in crop insurance. Participants livelihood dynamics were described, and significant associations are observed between Educational Level and Use of CSA, as well as between Empowerment Level and Use of CSA. Additionally, a significant amount of variance was explained in the Empowerment Level based on the Use of CSA and Educational Level (R�� = 0.288, F = 39.00, p = <.001). Furthermore, six overarching themes emerged from farmers livelihood context, dynamics, and outcomes. The themes reinforced the existential threat of climate change and vulnerability of SWFs which is exacerbated by a complex interplay of factors.
The results were triangulated with the sustainable livelihoods framework which used Amartya Sen���s capabilities theory on the robust concept of agricultural productivity, not only in terms of yield or income but in the real doings and capabilities of what a farmer is able to do and has done with their capabilities. I found that although participants demonstrated adequate intrinsic, instrumental, and collective agency, they face obstacles such as poor infrastructure, unfulfilled government promises, and limited access to assets and tools which underscores systemic and institutional challenges that counterproductively affect agricultural productivity and empowerment.
Overall, I found SWFs are moderate and high users of CSA, but their livelihood outcomes are exacerbated by the negative effects of climate change and institutional failures. This underscores the need for targeted interventions, including improved infrastructure, access to resources, and supportive policies to enhance the resilience and empowerment of these farmers in the face of ongoing challenges
De-Equivariantization in Fusion Categories from Quantum Groups at Roots of Unity
No full textThe representations of quantum groups at roots of unity lead to an important class of premodular tensor categories. We will discuss the construction and important properties of these categories. Then we will consider the categories of this kind associated to type D Lie Algebras and present explicit computations to demonstrate the fusion rules, grading and pointed subcategory. We will also discuss and provide examples of de-equivariantization. This process involves creating a new category by taking the category of modules over an algebra object, in some sense taking a ���quotient��� based on the tensor product with this object. More specifically, we identify a subcategory equivalent to Rep(G) for some finite group G and take the algebra object of functions on G in this subcategory. Then we take the modules over this algebra object in the centralizer of Rep(G), which ensures that the resulting category of modules retains the structure of a braided fusion category. Examples of de-equivariantization in the literature primarily consist of performing de-equivariantization with a cyclic group G. We provide an example of de-equivariantization by a non-cyclic group Z2 �� Z2 and discuss strategies to approach de-equivariantization by non-cyclic groups. Specifically, we show that the boson condensation of C(so(8), 10, q) by the full pointed subcategory Rep(Z2��Z2) is isomorphic to four copies of the integral subcategory of C(su(2), 5, q)