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The Role of Auditors in Classification of Debt Securities: Evidence From Banks
No full textFirms that hold debt securities can exploit the discretion in security classification and classify securities as held-to-maturity when the classification provides a more favorable accounting treatment (hereby referred to as security classification shifting). In this study, I utilize the banking industry to examine whether auditors are associated with their clients��� security classification shifting strategies. I find a positive association between a bank-client���s security classification shifting and the classification shifting at other bank-clients audited by the same audit office. This finding is consistent with auditors influencing their clients��� security classification strategies. The effect of auditors is concentrated in banks engaging an audit office with a greater emphasis on bank-specific non-audit services and in smaller banks which suggests that auditors are more likely to influence their clients��� financial reporting strategies when the auditor has a greater proclivity to provide advice and when clients have a greater need for financial reporting expertise. Finally, I find evidence suggesting that industry-expert auditors limit security classification shifting in resource-constrained banks; however, non-expert auditors do not appear to have a similar effect
From Syntheses to Applications of Cyclized Conjugated Molecules and Macromolecules
No full textThis dissertation delves into conjugated molecules and macromolecules featuring cyclized constitutional structures, including conjugated ladder molecules, polymers, and macrocycles. These materials offer unique optical and electronic properties due to their extended ��delocalization and strong intermolecular coupling, stemming from their rigid structures. The dissertation explores how these structures can be integrated into conjugated molecules and polymers to address challenges such as instability and limited state delocalization, paving the way for practical applications.
The introduction provides an overview of conductive organic molecules and discusses conjugated macrocycles and ladder molecules, along with the processing of conjugated ladder polymers.
Chapter II presents the synthesis of conjugated ladder polymers with isotopic substitutions, such as deuterium and carbon-13 labels. Deuterium labeling enhances neutron scattering contrast, aiding structural analysis, while carbon-13 labeling assists in defect quantification. Two such polymers are synthesized.
Chapter III introduces the synthesis of a ladder-type structure in polyaniline-inspired polymers. A low-defect conjugated ladder polymer is synthesized, achieving high conductivity (7 mS cm^���1 ) through oxidation and acid doping. It demonstrates exceptional stability against acids and UV irradiation, surpassing commercial standards, and excels in electrochromic devices and supercapacitors.
Chapter IV describes a self-doping ladder-type cyclohexadiene-1,4-diiminium-based system, offering stability and homogeneity, with a conductivity of 1��10^���3 S cm^���1 , surpassing traditional p-type molecules.
Chapter V discusses the synthesis and iodine doping of conjugated macrocycles with different side chains, forming single-crystal structures when doped with iodine, with conductivity ranging from 2.6��10^���3 to 0.65 S cm^���1 . The chapter also explores crystal packing and doping mechanisms.
The dissertation concludes with an outlook on future research into conjugated ladder molecules and cyclic macrocycles, showcasing how cyclized structures in conjugated molecules and macromolecules address challenges in organic electronics, revealing their potential as next-generation electronic materials
A Novel ML-based Approach for the Prediction of the Oceanic Heat Flux in a Slab Ocean Model Coupled to a Physics-Based Model of the Atmosphere
No full textA slab-ocean model is a thermodynamic model of the ocean mixed layer. It provides a prognostic variable for the sea surface temperature (SST), and when coupled to a model of the atmospheric circulation, it allows for two-way ocean-atmosphere interactions at a low computational cost. The standard formulation of a slab ocean model accounts for the spatially varying thermal effects of the oceanic circulation by a prescribed two-dimensional static estimate of the oceanic heat flux field. A downside to using such a static estimate is that it cannot capture the effects of changes in the ocean circulation. This work presents a methodology to introduce a temporarily changing two-dimensional oceanic heat flux field in a slab ocean model. It also introduces a novel machine learning-based approach to dynamically evolve this field. The approach is tested on the low resolution atmospheric global circulation model SPEEDY, which has an optional slab ocean component. This component is modified to implement the proposed methodology. It is first demonstrated that the static estimate of the oceanic heat flux can be further improved by an iterative method. Then, it is shown that with the temporally varying estimate of the oceanic heat flux the model produces more realistic sea surface temperature variability than with the static estimate. Finally, it is demonstrated that the machine learning-based approach can be used to replace the prescribed estimates with a dynamically evolving field of the oceanic heat flux
Advancements in Cattle Nutrition and Health: From Antimicrobial Strategies to Environmental Sustainability and Innovative Pedagogy
No full textThree experiments were conducted to evaluate 1) the interrelationship between virginiamycin (VM) inclusion, ruminal pH dynamics, and hepatic blood metabolites to determine optimal supplementation phases; 2) the additive effects of condensed tannins (CT) and active dry yeast (ADY) on digestibility and fermentation dynamics; and 3) writing and visual models as a pedagogical strategy for creating individual learning paths in animal nutrition. In the first study, 120 growing steers (304 �� 27 kg) were fed for 150 d to evaluate the strategic administration of VM at 240 mg/d. We concluded that VM supplementation during the whole feeding phase tended to decrease the time spent under pH 5.8 (P = 0.081), thus improving rumen buffering capacity and reducing acidotic events. Additionally, VM inclusion lessened the acute phase protein response during the transition between the grower and finisher diet. In the second study, 23 ruminally cannulated steers (284.3 �� 4.1 kg) were utilized in a factorial design to evaluate the supplementation of ADY at 10 g/d, CT at 1 % DM of quebracho extract (0.78% total CT and 0.312% PPP on DM basis), and combined CT and ADY (CTY; 1% DM and 10 g/d, respectively). In vitro methane production was affected in a quadratic fashion (P = 0.001) as days progressed, with CTY being less relative to CON, CT and ADY (8.14 vs. 14.69 mM, respectively). The inclusion of ADY and CT did not affect ruminal variables (total VFA, protozoa, pH and redox; P ��� 0.05). However, apparent total tract DM digestibility (aDMD) and neutral detergent fiber digestibility (aNDFD) for CTY (60.08% and 51.78%, respectively) were intermediate of ADY and CT supplementation, aligning with our intended outcome of combining them. In the third study, students (n = 27) who participated in the honors contract of an upper-level animal nutrition course were asked to participate in a self-directed learning project. Likert scale surveys (88.8% response rate) and reflections reported that writing to learn gave them an authentic scientific writing experience that when paired with the creation of visual models improved their confidence and ability to interpret and integrate concepts from lecture and outside sources
Optimization-based Scheduling in Multi-service Appointment Systems with Application to College Counseling Centers
No full textAppointment scheduling is a crucial problem in various domains such as healthcare and logistics. In practice, several complicating factors make the decision-making process challenging. In this work, we study multi-service appointment scheduling systems having non-stationary arrival processes, with a special focus on college Counseling and Psychological Service (CAPS) centers. Given the increasing prevalence of mental health issues among college students and the resource constraints faced by CAPS centers in addressing the rise in demand, our goal is to propose data-driven solutions that improve students��� access to these vital services.
To achieve this, we adopt a two-step methodology. First, we develop a comprehensive discrete-event simulation (DES) model that accurately reflects the complexities of CAPS center operations. This model acts as a testing ground for evaluating the performances of different scheduling-related policies. Second, we construct optimization-based frameworks that leverage historical demand to identify data-driven schedules that lead to good-performing systems, while incorporating several realistic factors like multiple customer classes and their associated importance, time-varying demands, resource limitations, and implementability. To address the challenge of characterizing system performance for such complex stochastic systems, we develop stylized optimization models based on approximation schemes that capture the transient behavior of the original system. Further analysis leads to key structural properties, which we use to devise efficient globally convergent solution schemes for the stylized models. Our numerical experiments, based on data obtained from Texas A&M University���s CAPS center, demonstrate the benefits of the proposed scheduling methodologies, leading to policies that significantly enhance system performance compared to current scheduling practices
Quantifying Tradeoffs Among Water Use, Energy Use, Yield and Environmental Impact for Various Levels of Irrigation and Nitrogen Fertilization of Grain Sorghum
No full textCrop production systems are the most complex systems, which have many interlinkages among different sectors. Identifying and quantifying tradeoffs among those interlinkages is important to enhance the sustainability of crop production. This study aims to use water-energy-food (WEF) nexus approach to quantify tradeoffs among water use, energy use, food production, economic return and environmental impact to identify the optimum levels of irrigation and nitrogen (N) fertilization for grain sorghum production in the southeast region of Texas. The field experiment was conducted at the research farm of Prairie View A&M University in 2023. Four irrigation levels (rainfed and three levels of crop evapotranspiration including 75%, 100% and 125%) and four N fertilizer applications (recommended level, half recommended, double recommended and zero) were selected as treatments. Water use efficiency, yield, energy productivity, net income and carbon footprint were selected as indicators to represent interlinkages among different sectors and estimated for 16 different levels of irrigation and N fertilizer application combinations. WEF nexus index was developed using the above five selected indicators and the treatment with the highest WEF nexus index was selected as optimum combination. Among 16 treatments, in rainfed conditions and at 75% ET irrigation level, yield was low, and the cost of production was high with a negative net income. Highest yield, water use efficiency and carbon footprint were observed in the 100% ET with double recommended N fertilizer application while highest energy productivity and net income were observed at the 100% ET with half recommended N fertilizer application. Application of irrigation water at 100% of crop evapotranspiration and half recommended N fertilizer (90 kg of N/ha) resulted in the highest WEF nexus index value, which is 0.812 and was hence selected as optimum levels for grain sorghum to enhance the sustainable production. The findings of this study highlight the importance of quantifying tradeoffs among water-energy and food production and applying holistic tool such as WEF nexus index to make decisions on selecting appropriate crop management practices to ensure the sustainable use of water and energy in crop production while achieving optimum productivity
The Economic and Financial Potential of Vineyards in the Texas Hill Country
No full textThere has been a substantial increase in the population of the Texas Hill Country over the last
decade (Hill Country Alliance 2008). Currently, the population in the Texas Hill Country is 3.1
million and is projected to increase to 4.3 million by the year 2030 (Hill Country Alliance 2008).
With respect to agricultural production activities in the area, a major downside of the population influx occurring is that property values have increased at a rapid rate in association with the resulting high demand (American Society of Farm Managers and Rural Appraisers 2019, p. 54). With the rapid influx of people into this region of the state expected to continue, many rural property owners are looking for sources of income that could help offset the increase in property taxes associated with the steadily increasing land prices. In this regard, the potential that vineyards have in the Texas Hill Country, due to their proximity to wineries, presents an interesting question, ���Are vineyards economically and financially feasible for current and potential vineyard operators as well as investors?���
While the concept of growing wine grapes to offset the cost of land and associated property taxes is intriguing, there are several questions that present themselves. Potential producers, and investors, do not have all the necessary information needed to make an informed decision as to if growing grapes is a sound financial endeavor. This thesis is an investigation of a series of scenarios that consider the relative effects of several factors on the potential profitability of a hypothetical Texas Hill Country vineyard operation. Evaluation of these projections allows economic and financial evaluation of the potential of self-sustaining vineyards in the Texas Hill Country, providing information to producers and investors interested in growing grapes in the Texas Hill Country.
This thesis includes a detailed documentation of the assumptions and parameters for three
vineyards of varied sizes as well as the economic and financial results for each size for the
specified scenarios. High land prices contribute to substantial initial capital investment
requirements which places an immediate financial strain on the vineyard from day one. Based
on the established parameters for this thesis, the potential for vineyards in the Texas Hill Country to be economically and financially attractive to potential investors and producers is unlikely. The limitations of this thesis and suggestions for future research are identified, with intentions of identifying pathways for further evaluating the potential of vineyard investments and the value of vineyards in complementing winery operations
Single-Phase and Two-Phase Flow Visualization Experiments in Molten Salt Natural Circulation Loop
No full textA natural circulation loop facility was designed to mitigate major challenges in flow visualization experiments of molten salt. Single-phase and two-phase flow experiments were conducted for molten salt and compared to experiments with water as a benchmark study. Particle image velocimetry (PIV) measurements and continuous temperature measurements were obtained. In single-phase flow experiments, the full velocity field and near wall velocity field were captured and analyzed as a function of the Prandtl number. The friction factor and Nusselt number were determined and compared with correlations found in literature. System Analysis Module (SAM) code validation was performed using a one-dimensional fluid flow model of the experimental facility. Two model types were developed using the default friction factor in SAM and user input of the experimental friction factor. The accuracy of the model improved in predicting the velocity in the loop with input of the experimental friction factor. Successful validation was found for developed flow cases of water and molten salt. A cooling transient due to heater failure and subsequent salt solidification in the natural circulation loop facility was presented as a scaled-down accident scenario of a salt plug blockage during reactor shutdown. A main heater failure resulted in immediate cooling of temperatures around the loop, and available backup heaters were not able to compensate for the initial loss of power. The transient was analyzed in seven phases to describe the overall behavior in the loop as salt cooled to the freezing point. Two-phase flow visualization experiments were conducted for three argon bubble sizes injected into a co-current stream of molten salt in the natural circulation loop facility. Similar bubble sizes were injected in experiments with water to compare the bubble shape, trajectory, and wake flow behavior of the fluids. The bubble region of interest (ROI) was found to determine the equivalent diameter and terminal velocity as the bubble traveled through the test section. PIV analysis was performed and used with the bubble ROI to determine the slip ratio and slip velocity between the liquid phase and gaseous phase
Influence of Rock Types on Porosity-Permeability Relations in Clastic and Carbonate Reservoirs with Application to CO2 Storage Site Characterization
No full textAccurate site characterization is essential for evaluating geological carbon dioxide storage potential. Geoscientists can model and monitor the behavior of injected carbon dioxide and rock interactions with knowledge of spatial variation of porosity and permeability. This thesis aims to estimate and understand permeability in carbonate and clastic reservoirs with geological analysis and acoustic well log data.
Jennings and Lucia (2003) model is used to calculate rock fabric numbers (����) in a carbonate reservoir in the Michigan Basin. By integrating information about the cored sections, three distinct classes were identified from rock fabric numbers. With Sun model (2004), a shear-frame flexibility factor (������ ) is calculated from acoustic properties and is used to relate permeability to rock pore structures. The shear-frame flexibility factor (������ ) is related to rock fabric numbers (����) through a linear transformation. The relations between shear-frame flexibility factor and rock fabric numbers will be very useful to estimate permeability from acoustic log and 3D seismic data, which will help predict CO2 pathways in potential CO2 storage sites.
This research also indicates that with sonic logs, we can calculate volume of shale in clastic reservoirs and relate to permeability. Permeability is controlled more by clay content in higher porosity zones. Higher volume of shale values indicates lower permeability values and that mechanical strength and pore structure play a greater role when constraining permeability values. Volume of shale can be related to elastic properties with Sun model (2004). The shear-frame flexibility factor can help constrain ranges of permeability in clastic reservoirs more accurately when porosity is at least 20%.
In addition, a fluid substitution model can be produced with Gassmann���s equations (1951). The impact of different fluid saturation changes is caused by CO2 injection on elastic properties and can be detected from synthetic seismic modeling and related to post-stack inversion results.
The theoretical results of this thesis are valuable for site characterization and locating potential CO2 storage, especially with the use of these rock physics models. With these results, geoscientists can use these methods to better comprehend the behavior of injected CO2 and rock interactions in the reservoir
Three-Dimensional Simulations of Ductile Fracture Under Arbitrary Loadings
No full textFracture leads to billions of dollars of losses worldwide every year, leading to material waste in manufacturing or disrupting the safe operation of load bearing components. For structures capable of plastic deformation, the ever-increasing demands on performance under extreme environments, combined with the challenges of an-all-experiments based approach, require the development of reliable and predictive failure models under real-world situations. In addition, new design paradigms and the development of strong, lightweight materials for use in thin-walled structures test the limits of classical methods based on linear elastic fracture mechanics. After half a century of porous material yield function development, there is still no sound basis for predicting pore-mediated ductile failure under general loadings. Tremendous progress has been achieved for modeling failure assuming mesoscopically homogeneous deformation at appropriate length scales. The inherent limitations of available theories due to the neglect of what has recently been termed unhomogeneous yielding at such scales are numerous. For example, no existing theory can predict failure in a simple torsion specimen on a sound physical basis, let alone under more general shear-dominant loadings.
In this work, a data-driven approach is followed to develop a porous material plasticity yield function that accounts for porosity, void shape and orientation. High-throughput computational limit load analysis is used to this end. The same dataset is employed to calibrate evolution equations developed on the basis of Eshelby concentration tensors. A comprehensive constitutive theory, named HUNNY, is then formulated which is applicable under general loading conditions. The theory is akin to crystal plasticity but with dependence on the resolved normal stress. In the isotropic limit, dependence upon all stress invariants is rationalized. The predictive capabilities of the theory are assessed against a large set of micromechanical unit cell calculations under combined tension and shear loading. Several realizations of the theory are implemented as user-defined subroutines to enable three-dimensional structural simulations of crack initiation and growth. Illustrations are given to simulate ductile failure in a round notched bar and a top-hat shear specimen developed at the Sandia National Laboratories. Finally, the formulation is extended to deal with more complex hexagonal materials exhibiting plastic anisotropy, such as magnesium alloys