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In this dissertation, we explore two applications of discrete tempered stable (DTS) distributions, a flexible class of distributions well-suited for modeling heavy-tailed and overdispersed data. DTS distributions are derived by tempering the tail of discrete stable distributions.
The first application addresses challenges in simulating positive tempered stable (PTS) distributions. Except for a few cases, there is no known simulation method for these distributions. We propose a novel simulation method using DTS distributions to approximate PTS simulations and establish a convergence rate for our estimation.
The second application focuses on modeling high-frequency financial data, or tick data, characterized by discrete price changes dictated by tick size. We compare the performance of DTS distributions against standard discrete models, specifically Poisson and negative binomial distributions, in modeling price changes. Additionally, we employ Monte Carlo methods to approximate the future distribution of portfolio values, utilizing these insights for risk assessment.
Preconception care is designed to ensure that women begin pregnancy at optimal health by having received proper chronic and sexual transmitted infection screenings, provider counseling about necessary health improvements, and treatment for conditions or illnesses that may impact the likelihood of a healthy pregnancy or childbirth. This type of care is especially important for Black women who continue to face disproportionate risk of pregnancy-related death in the United States. Due to the higher maternal mortality rates among Black women, a more targeted investigation and implementation of consistent care prior to pregnancy is needed.
My dissertation thematically examines the trends, knowledge, and experiences of preconception care among Black women who reside in the United States. I investigated the offer, reception, and administration of preconception care services using a mixed methodology approach. First, I analyzed preconception care reception among Black women using 2016-2021 PRAMS (Pregnancy Risk Assessment Monitoring System) data. This secondary analysis concluded that hypertensive Black women had 21% decreased odds of receiving preconception care, compared to their non-hypertensive counterparts despite their diagnosis of hypertension. Second, I developed and preliminarily validated the Preconception Care Health Knowledge Scale, which was designed to assess a woman’s knowledge level of the preconception care services needed for a healthy pregnancy. By community validation, psychometric validation, and content validation, I established that the instrument, once revised, will be suitable for assessing the knowledge of preconception care among Black women in the US. Third, I conducted a qualitative study that analyzed the healthcare experiences of Black women who began pregnancy with hypertension. Through semi-structured interviews, the participants identified Health Literacy and Knowledge, Provider Counseling, Provider Interaction, and Provider Race/Ethnicity as the most impactful themes related to their overall healthcare. The participants were knowledgeable about their hypertensive condition and expected their healthcare providers to inform them about the risks associated with beginning pregnancy with hypertension. However, several participants reported not being properly diagnosed with hypertension prior to pregnancy, which resulted in delayed treatment and increased the potential for adverse outcomes stemming from pregnancy-related hypertensive disorders.
My findings address critical gaps in the literature on the use of preconception care as a method to prevent maternal morbidity and mortality among Black women. I found Black women’s preconception care treatment to be inconsistent, especially among women who were hypertensive. These findings inform the development of frameworks, interventions, and policy to reduce the disproportionate and unnecessary maternal morbidity and mortality among Black women in the United States.
Social-emotional learning (SEL) programs have gained attention in K-12 education for their role in supporting students’ social development, emotional well-being, behavioral development, and academic success. While SEL programs have been widely studied in elementary schools, there is a gap in research regarding their implementation and effectiveness in middle schools. This descriptive qualitative multiple-case study explored middle school teachers’ perceptions of implementing the CharacterStrong SEL program. It focused on the program’s perceived benefits, challenges, and impact on middle school students’ academic, behavioral, and social-emotional outcomes. Guided by the CASEL framework for SEL and Self-Determination Theory, data were collected through four focus groups and 12 middle school teachers from a rural district in North Carolina who have implemented the CharacterStrong program for at least three years.
Findings indicated that SEL is valuable for fostering students’ emotional regulation, resilience, and interpersonal skills. Participants reported improvements in student behavior and classroom climate and identified challenges related to teacher training and time constraints. Teachers also emphasized the importance of aligning SEL instruction with content curriculum and the need for ongoing professional development to enhance program fidelity. This study offers valuable insight for school leaders, policymakers, educators, curriculum developers, school counselors, and mental health professionals by providing strategies for improving SEL implementation, enhancing professional development, and shaping future studies on social-emotional learning in middle schools.
With the modernization of power grids, high penetration of distributed energy resources (DERs), and modern state-of-the-art loads are increasing to the grid, optimal power flow (OPF) analysis is one of the essential tools for reliable power system planning, operation, and control. This research proposes novel OPF power distribution and transmission network models using non-linear programming (NLP). The advantages of NLP-based OPF models are that they are accurate and give optimal global solutions for both transmission and distribution networks. To confirm solution accuracy, the necessary conditions for the formulations of power flow models are addressed in this research work for the proposed OPF models. In this dissertation, a centralized and distributed model based on NLP is proposed for OPF analysis in power distribution networks, solved with the Sequential Quadratic Programming (SQP) algorithm. This work proposes the method and illustrates the necessary conditions for the global optimality of the solution. The main advantages of the methods are obtaining global optimal solutions in less than a minute (for more than 2000 nodes with high penetration of DERs) without approximations and relaxations in power flow equations and improving scalability by reducing the number of iterations significantly for both centralized and distributed OPF. This research also proposes an SQP-based centralized and distributed optimal power flow (D-OPF) method for bulk power transmission grids with a modified equal network approximation framework (MENA). Moreover, a method is proposed for integrated transmission-distribution (T&D) OPF, and the efficiency of the integrated (T&D) is shown. This article also proposed a novel volt-var-optimization (VVO)-based centralized closed-loop voltage management co-simulation methodology that uses an NLP-based optimization (OPF) model and a real-time Opal-RT simulator. This research developed a real-time model of an integrated T\&D network with fully detailed and dynamic models of energy sources such as synchronous generators and inverter-based resources (IBRs) to fully understand the voltage profile of both the transmission and distribution system, with penetration of IBRs on both sides, and a volt/var optimization framework is developed to control the distribution side voltage. The models are validated using different IEEE test cases consisting of both transmission and distribution networks. The simulated results prove the accuracy and efficiency of the models.
A new era of proliferated telework was ushered in by the Covid-19 pandemic and powered by rapid technological advancements in connectivity and network availability. Previous telework research has established significant relationships with employee attitudinal outcomes to include job satisfaction, turnover intention, and organizational commitment. However, most prior studies have examined direct or mediated relationships that overlook the additional complexity and explanatory power of moderating variables. Drawing from social exchange theory and with secondary support from public service motivation theory, this dissertation examines telework from the employee perspective by exploring the moderating role that perceived supervisory support and perceived fairness play on job satisfaction, turnover intention, and organizational commitment. A large sample of U.S. federal agency employees (N=557,778) collected from the 2022 Office of Personnel Management’s Federal Employee Viewpoint Survey provides strong insight into these interactions through a series of regression analyses. Empirical evidence found that perceived supervisory support strengthened the relationship between telework participation and all three dependent variables, while perceived fairness strengthened the relationship between telework participation and turnover intention but weakened the relationship between telework participation and both job satisfaction and organizational commitment. These results provide important theoretical and practical implications for U.S. federal agencies in the post-Covid 19 era.
PATIENCE BROOKS. Understanding How Racial Identity Development Leads White Teachers Towards Antiracist Pedagogies: A Case Study From A Rural Professional Learning Community.
(Under the direction of DR. TINA HEAFNER)
The U.S. education system lacks a comprehensive effort to help white educators examine their racial identities, hindering their ability to address systemic racism in schools. Without significant curriculum and instructional reforms, systemic biases persist, harming students of color (Lewis et al., 2012). This study examines how white, rural teachers navigate their racial identities while engaging with literature that challenges their perspectives on systemic racism and antiracist teaching, all within an ongoing professional learning community (PLC). The research questions are: 1. How do white teachers’ racial identities develop when engaging in an antiracism-focused professional learning community? and 2. After participating in a year-long antiracist PLC, how do white teachers integrate antiracist curriculum and instruction? The first question is framed by white racial identity development, drawing on the white racial identity framework, second-wave white teacher identity studies, and critical whiteness studies. The second question is grounded in antiracist pedagogies, incorporating critical race theory, antiracist teaching, culturally responsive teaching, multicultural education, critical literacy, and critical service-learning.
This case study examines the racial identity development of seven teacher participants over the course of a year as they engage with an antiracist curriculum within a PLC. It subsequently investigates the curricular and instructional changes implemented in their classrooms as a result of their developing antiracist teaching knowledge.
The results indicated the antiracist curriculum facilitated transformative growth in participants’ racial identities as participants critically examined their own biases, assumptions, and roles within systems of privilege and oppression. Furthermore, there were clear connections between participants’ engagement with the PLC and their ability to integrate antiracist practices into their teaching, reflecting their evolving understanding of racial identity and social justice. Discussions, implications, and future research is also presented.
Keywords: white racial identity development, antiracist pedagogies, critical race theory, antiracist teaching, culturally responsive teaching, multicultural education, critical literacy, critical service-learning.
Public school facilities have been underfunded and experienced deferred maintenance, creating deteriorating and aging facilities. This study sought to fill a scholarly research gap and inform school leaders of conditions impacting the willingness of local communities to address school facility needs. Using semi-structured interviews, this qualitative, multiple-case study explored the experiences and perceptions of current and former school superintendents and current and former school board members from two low-wealth, rural school districts in North Carolina on conditions that affected the willingness of local communities to address school facility needs. Findings indicated that community trust positively impacted the willingness to address facility needs. At the same time, resistance to increased taxes to support school bonds and contentment with their current schools due to tradition and family history hindered efforts to improve facilities. Implications suggest the importance of building trust between the school district and its community through frequent communication. Additionally, creative funding strategies that do not raise taxes are essential to maintain community support. Finally, this study also suggests that the state’s reliance on local governments for most facility funding burdens low-wealth counties, exacerbating their facility challenges.
Modern microbialites are benthic organosedimentary structures that provide an analog to Earth's ancient ecosystems. Despite their importance, microbialites and microbial mats are often understudied, especially when trying to understand their formation process, known as lithification. Microbial-viral-mineral interactions may provide catalysts for lithification. This dissertation provided methods that apply to modern microbialites and microbial ecosystems generally. Chapter 2 detailed methods to enumerate viruses and microbes directly via epifluorescence microscopy (EFM) and flow cytometry (FCM). Chapter 3 provides a robust database, NFixDB, for nitrogen fixation enzymes which is critical to all life on Earth. Finally, chapter 4 resolved metabolites and lipids within modern microbialites across the globe. The methodology in Chapter 2 allowed for the direct measurements of viruses (as viral-like particles) within the Great Salt Lake (GSL), which equated to a mass of all the viruses in the GSL to be roughly 2.2 kg or the weight of a standard red brick. From Chapter 4, I resolved the conundrum of nitrogenase related databases by creating the first whole-genome resolved a comprehensive collection of nitrogenases, alternative nitrogenases, pseudo-nitrogenases, and ribosomal subunits found within nitrogen-fixers (i.e., diazotrophs). Finally, a metabolomic and lipidomic study of seven microbialites across the globe were analyzed. Findings revealed carbohydrates, fatty acids, polar lipids, and glycerolipids are the main contributing factors when distinguishing between freshwater and hypersaline environments. Distinct nutrient patterns, organism niches, and stress responses were identified, providing more insight into the microbial interactions that produce microbialites. Altogether, these findings demonstrate the importance of understanding microbialite lithification, especially when identifying factors that may affect larger climates and the entirety of Earth's ecosystems.
This qualitative study examined the experiences and perceptions of four Black male public school elementary teachers working in a large urban school district in North Carolina and focused on the factors motivating them to remain in the profession. The researcher explored elementary school teachers because more males teach in middle and high schools. Over the past decade, investigators have documented many recruitment efforts to increase the presence of Black male teachers working in our schools. Yet, retention for this group, especially at the elementary level, continues to be a pressing issue. Before the pandemic, Black male teacher representation was two percent nationwide. Since then, Black male teacher representation was 1.3 percent and is expected to decrease further. The likelihood of a male teacher of color leaving the teaching profession was 50% higher than a female teacher of color (Bristol, 2020a). For this case study, the data source included a semi-structured, one-on-one virtual interview with four Black male elementary school teachers in North Carolina. Results from this study indicated that the participants perceived support from colleagues, administrators, state leaders, and their families would contribute to their decision to remain in the teaching profession. They also indicated that professional development can foster individuality and growth. Principals who strategically created spaces for Black males to contribute meaningfully to the school decision-making process and network with other professionals in and outside the school building influenced their decisions to stay. Participants were concerned for the future regarding retaining this group of teachers. They emphasized that teacher pay and leaders putting them into the role of disciplinarians, instead of valuing their skills as instructional leaders, continued to be a deterrent for them.
U.S. graduates must be critical thinkers, have strong interpersonal skills, understand diverse cultures, and speak more than one language to compete in a global workplace (Tucker, 2021). Dual language immersion (DL/I) is a successful instructional model that prepares students for the global economy (Thomas & Collier, 2017). Staffing DL/I programs is challenging because of the national shortage of teachers in the United States, particularly bilingual teachers (Hernández et al., 2022). The lack of bilingual teachers in the United States forced some schools to hire international teachers (Hernández & Alfaro, 2020).
The purpose of this phenomenological study was to understand the acculturation experiences of international Latinx teachers, specifically focused on their onboarding support. Using LatCrit and Human Capital Theories, this phenomenological study analyzed the semi-structured interviews to explore the first-year experiences of seven international Latinx teachers. The results of the study indicate that intentional sociocultural support must be provided to improve acculturation and retain bilingual teachers. School support must include a culturally welcoming school community, the strategic assignment of mentors, professional development focused on the use of technology and assessments, and sociocultural support in navigating financial challenges related to housing and transportation. Implications of this study call for school districts and principals to develop culturally-informed onboarding systems to increase international teachers’ sense of belonging and reduce the stress they encounter adjusting to a new community. Additionally, North Carolina’s Department of Public Instruction’s commitment to DL/I expansion should include financial support for the relocation of bilingual teachers.
