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Microstructural characterization and structural and electrical property determination of oxide/oxide ceramic matrix composites upon thermal plasma exposure.
No full textDuring hypersonic flight, vehicle components are exposed to very high temperatures and chemically active plasma over a wide range of air pressures, which are dependent upon altitude. Ground-based testing and post-test evaluations are necessary to understand material performance in these challenging environments. In this dissertation, two variations of alumina-based Oxide/Oxide Ceramic Matrix Composites (CMCs) were tested in thermal plasma, mimicking the harsh thermal and chemical environments expected in hypersonic flight. While both CMC systems contained NextelTM 720 fibers, they differed in their matrix compositions with one containing only alumina and the other both alumina and mullite. The tests were performed in near-vacuum and full atmospheric pressure conditions over a range of heat fluxes. After testing, the samples were evaluated for physical, structural, microstructural and dielectric property changes. Additionally, in situ dielectric property measurements were taken at temperatures up to 1000°C in an isothermal furnace environment. The material response was evaluated in three main areas of focus: first, the effect of increasing heat flux, second, the effect of matrix composition, and third, the effect of the surrounding atmosphere. In addition, the effect of harsh thermal plasma environment on material performance was evaluated through structural and dielectric tests.
The samples tested in near-vacuum environments showed exceptional resilience with minimal erosion and mass and thickness loss. Microscopy and X-Ray Diffraction showed no evidence of melting. In alumina-mullite matrix samples, fusion between fibers and matrix was observed but was confined to regions near the impingement surface, so structural properties were not significantly affected. Similarly, the dielectric properties of both material variants in near-vacuum conditions were within the acceptable range for all exposure conditions tested. In contrast, the material response in atmospheric pressure conditions was significantly more aggressive. In addition to melting, fiber and matrix fusion were observed throughout the full thickness of the laminates at heat fluxes above 80 W/cm2. Significant physical deformation prevented dielectric and structural testing of these samples. Overall, the Oxide/Oxide CMCs showed great promise for use in hypersonic vehicles, especially for high altitude flight, maintaining both its structural and dielectric properties
The faculty learning lens : a single case study of diversity, equity, and inclusion programming at a Texas independent school.
No full textSince the social unrest during the summer of 2020, educational institutions across the nation have evolved their Diversity, Equity, and Inclusion (DEI) programming to address fundamental concerns about the lack of inclusive practices in their learning environments (Craig & Loehwing, 2021; Wang et al., 2023). DEI training and faculty professional development are key drivers to addressing inequities in educational institutions, and often part of a school’s larger strategic plan (Emerick, 2023; Wang et al., 2023). In Texas, the mandate for public universities to eliminate DEI programming conflicts with the National Association of Independent Schools (NAIS) principles of good practice, which require DEI programming for accreditation (Mohamed & Mcgee, 2024; NAIS - Equity and Justice, n.d.). Therefore, the rollback of DEI support in Texas threatens progress in independent schools, where initiatives address race, gender identity, sexual orientation, socioeconomic status, ability, religion, and other identities.
The purpose of this qualitative single case study was to explore faculty learning experiences with DEI programming within a group setting at one K–12 independent school in Texas. Guided by Etienne Wenger-Trayner’s (1998) community of practice theory, I examined how faculty described the community, domain, and practice aspects of their professional learning. I collected data through an open-ended questionnaire, one-on-one interviews, and a focus group session. Participants included four full-time faculty members who engaged with DEI programming on campus as members of division-specific DEI Task Forces and through various volunteer opportunities aimed at developing DEI-related skills and knowledge.
The study found that while faculty faced numerous barriers in advancing DEI initiatives, their engagement in DEI-focused learning groups helped them build connections with the wider school community. The participants emphasized the importance of creating inclusive spaces where students feel a sense of belonging. Faculty also identified structured professional development as essential to their growth, noting that ongoing training and dialogue supported their evolving understanding and application of DEI practices. These findings can guide NAIS-affiliated school leaders in Texas as they navigate DEI programming in a divided political climate
Exploring the workplace stressors and coping skills of Black women in medical leadership : a qualitative single case study.
No full textThis qualitative single case study explored how Black women in medical leadership positions described the workplace stressors they encountered and the coping strategies they used to manage those stressors. The study was guided by the theory of transformative coping (TTC; Corry et al., 2014) and addressed two research questions concerning the nature of stressors and the coping approaches used by participants. The participants were Black women who held leadership roles in diverse medical settings, whose intersecting racial, gender, and professional identities posed distinctive challenges. By centering their narratives, the study illuminated underexamined experiences of marginalization and resilience in clinical leadership roles.
I employed criterion sampling to select four participants who completed an open-ended questionnaire, engaged in a photo-elicitation activity, and participated in a semi-structured interview. Data analysis followed Creswell and Poth’s (2018) data analysis spiral, utilizing descriptive coding to organize codes into a priori categories from the theoretical framework (e.g., stressors, appraisals, strategies, resources, transformation). The thematic analysis yielded five key themes related to identity-driven stressors, appraisals, adaptive and maladaptive coping, spirituality and creativity, and transformation via self-reflection and self-evaluation.
The findings aligned with prior research on persistent gendered racial barriers, personal struggles, and time-related challenges eroded leadership legitimacy and well-being, prompting social-support and withdrawal strategies. The participants noted that spiritual practices and creative outlets functioned as vital coping resources due to ongoing stress and sustaining emotional well-being. Participants experienced transformation as they redefined their professional identities, moving from performance-based validation to legacy work, mission-driven priorities, and community impact.
The implications emphasize the need for healthcare organizations to create identity affirming, psychologically safe systems that center on emotional regulation, reflection, spiritual well-being, and creativity as leadership strengths. The practices enhance retention, equity, and resilience for Black women in medical leadership. Recommendations include revising institutional policies on productivity and staffing, implementing peer-to-peer debrief protocols that normalize culturally attuned support, and offering trauma-informed training for support staff. Additionally, research is needed to understand how Black women in medical leadership develop and use coping strategies throughout their careers
Exploring teachers’ perceptions about how the elements of the positive behavioral interventions and supports (PBIS) model work together to influence positive student behavior : a qualitative single case study.
No full textThe prevalence of inappropriate student behavior in America’s public schools has reached alarming levels, significantly disrupting academic achievement and the overall learning environment. The problem at the heart of this study is that students’ inappropriate behavior continues to increase in school spaces, jeopardizing the learning opportunity for themselves and other students who attend classes with them. Recent statistics also indicate that many public schools reported negative impacts on students' social-emotional and behavioral development, exacerbated by the challenges posed by the COVID-19 pandemic. Within this context, the Positive Behavioral Interventions and Supports (PBIS) framework has been adopted by numerous schools. However, many schools struggle with effective implementation, leading to increased teacher turnover and a negative school climate. This study focused on Johnson Elementary School to explore how the five interrelated elements of the PBIS model enhance positive student behavior on one elementary school campus. I also sought to uncover teachers’ perceived challenges to its implementation.
This single case study utilized a constructivist qualitative research design and three data collection phases: an open-ended questionnaire, individual interviews, and a focus group discussion. The participants, all experienced teachers at Johnson Elementary School, provided their perceptions of the effectiveness of PBIS and the challenges encountered during its implementation. Data analysis involved a priori coding aligned with the PBIS elements and open coding to identify emerging themes.
The findings revealed four primary themes: the significance of positive reinforcement, the necessity of a deep understanding of PBIS, the importance of maintaining implementation fidelity, and the impact of staff attrition on the program's success. These four themes relate to teachers’ perceptions regarding how the five interrelated elements play a role in implementing PBIS and the challenges that arise during implementation. The implications of this study underscore the need for ongoing professional development, collaborative environments, and robust support systems to enhance the effectiveness of PBIS in elementary schools. The research highlighted that a cohesive approach to implementing PBIS can foster a positive school climate and improve student behavior. Recommendations were provided for educators, administrators, and district leaders to address the identified challenges and promote successful PBIS practices
Learning unleashed : a qualitative multiple case study illuminating supported employment professional development perspectives through the staged self-directed learning model.
No full textSupported employment services play a critical role in promoting competitive, integrated employment for individuals with disabilities. Despite this essential role, research shows that professionals working for supported employment organizations often receive insufficient professional development in the amount and scope of competencies needed to effectively and consistently deliver services (Hall et al., 2018). Additionally, there is limited research examining how professional development influences the learning of professionals in supported employment organizations.
This qualitative multiple case study explored how supported employment professionals perceived and experienced professional development. Using Grow’s (1991) staged self-directed learning (SSDL) model, I sought to understand how professionals’ perspectives and experiences in professional development influenced self-directed learning across the framework’s stages of learner readiness and facilitator behavior. I collected data from a purposive and criterion sample of four supported employment professionals in the United States through questionnaires and semi-structured interviews. I conducted a thematic analysis to identify cross-case themes, with a focus on how participants described their experiences in alignment with the SSDL model. I enhanced trustworthiness through triangulation of data sources, member checking, and rich description.
The findings of this study provided a window into the professional development experiences of participants from onboarding with their organizations and throughout their respective learning journeys. The findings revealed five themes related to mandated training, knowledge acquisition and application in the field, perceptions of facilitator support and self-direction, facilitator trust and promotion of autonomy, and external training and certifications. The implications and impact of this study suggest potential insight for four groups of key decision makers to promote change and additional research for the supported employment field. The implications and recommendations affirm the need for additional research on how supported employment professionals progress through the learner stages of the SSDL model from their first day of employment, as well as research on how professional development facilitators in supported employment organizations engage in the teacher stages of the SSDL model as they scaffold learning
Tenured and departing : a single case study exploring the perceptions of tenured faculty about their departure from a community college in central Oklahoma.
No full textCommunity colleges face a critical challenge in retaining tenured faculty, evidenced by a 6.4% decline in their numbers from 25,313 in 2013 to 22,015 in 2023 (AAUP, 2024; Daigle, 2022). Faculty attrition imposes significant direct costs, such as recruitment expenses, and severe indirect impacts, including decreased graduation rates, lower student retention and learning outcomes, and reduced faculty morale (Ambrose et al., 2005; Johnsrud & Rosser, 2002; Ramasamy & Abdullah, 2017; Rosser & Townsend, 2006; Zhang et al., 2022). Understanding why experienced tenured faculty members depart is crucial for community college leaders in their efforts to develop effective strategies to mitigate faculty attrition and its detrimental effects.
Tenured faculty members leave their roles in higher education for a variety of reasons. These often include more attractive job options, personal or family matters, a lack of organizational support, or dissatisfaction with salary (Hoyos & Serna, 2021; Minnotte & Pedersen, 2021; Osburn & Gocial, 2020; West, 2024; White-Lewis et al., 2023; Zhang et al., 2022). While research on faculty departure often focuses on universities (White-Lewis et al., 2023), studies specifically examining community colleges highlight compensation, job security, and career advancement opportunities as key influences (Sivells et al., 2025).
In this qualitative case study, I explored the internal and external factors (Zhou and Volkwein, 2004) influencing tenured faculty members’ decisions to leave their positions at one community college in the state of Oklahoma. Focusing on the experiences of four former tenured faculty from Ridgecrest Community College (RCC, pseudonym), I utilized an open-ended questionnaire, semi-structured interviews, and a focus group to gather rich qualitative insights. Findings revealed that decisions to depart stemmed from a convergence of six key factors. Internally, a decline in collegiality, trust, and support, coupled with heavy workloads, unrealistic responsibilities, erosion of administrative trust, and feelings of being undervalued, actively drove departures. Externally, diverse job opportunities with better pay and manageable duties, alongside evolving family and personal needs, served as strong pull factors. These results provide a nuanced understanding of faculty attrition, offering essential insights for administrators, department chairs, and faculty to foster a more supportive academic environment and enhance retention
Understanding antiracist transformation and praxis : a multiple case study of White practitioners’ lived experiences, learning processes, and sustaining supports.
No full textThis multiple case qualitative study extends the literature on White allyship and antiracism. The powerful 2025 social and legislative success of the anti-work, anti-DEI, anti-CRT coalition complicated and slowed racial justice efforts across sectors. Antiracism movement leaders urge the public and scholars to apply a structural analysis of racism, antiracist principles and frameworks from the movement to strengthen racial justice efforts amid the conservative. The scholarly literature suggests that White allies play a crucial role in the coalition working to dismantle racism in the U.S. However, many White supporters of racial justice struggle to be effective in their solidarity according to movement and academic literature.
The purpose of this study is to better understand White antiracist practitioners’ transformation and praxis, including their lived experiences, learning processes, and sustaining supports amid powerful socio-political barriers. This study used Mezirow’s (2000) transformation theory as a theoretical framework to explore how individual White adults transform their beliefs and actions around race and racism. Participants reported experiencing an antiracist transformation and being actively committed to antiracist praxis for more than five years. Qualitative data sources included a questionnaire, individual interviews, and journal submission.
This study offers implications and recommendations for White allies and potential antiracist practitioners, racial justice or DEI educators and facilitators, organizational leaders committed to racial justice, and scholars exploring race and racism. The findings underscore the importance of learning a structural analysis of racism and interrogating internalized racial oppression. For allies, educators, leaders, and scholars engaging in supportive multiracial antiracist networks and committing to ongoing critical reflection is key. Participants all highlighted the invisibility of their own Whiteness growing up. The disorienting dilemma early in their antiracist transformation was coming to understand history and their own socialization into White supremacy. Participants also stressed the hope and positive impact of practicing antiracism on their lives and relationships. The study calls on scholars to explore the principles, analysis, and frameworks of the modern grassroots antiracism movement and to interrogate effective White antiracist allyship and solidarity
A qualitative holistic single-case study approach to explore newly certified Texas K–5 public school teachers’ self-efficacy regarding behavior management.
No full textDirectly aligned with this study’s findings, research suggests that teachers have described feeling that their educator preparation programs (EPPs) equipped them with universal, Tier 1 behavior management techniques. However, programs often fail to prepare teachers adequately for Tier 2 and Tier 3 interventions, which are necessary when students exhibit challenging behaviors. Research highlights evidence-based behavioral interventions that teachers report not having learned in their EPPs, pointing to a critical and concerning gap.
The purpose of this study was to explore how newly certified Texas K–5 public school teachers who complete an EPP and have less than five years of classroom experience described their self-efficacy regarding behavior management. The goal of this study was achieved through a qualitative holistic single-case study approach. The data collection tools were a semi-structured Qualtrics questionnaire and semi-structured individual interviews. These tools align with the four components of Bandura’s (1977) self-efficacy theory: performance accomplishments, emotional arousal, vicarious experience, and verbal persuasion, which are foundational principles for this study. I used social media recruitment, flyer distribution, and a criterion sampling approach to identify six participants across two regions in Texas who volunteered for this study.
Through data analysis, I discovered that participants described feeling that their EPPs prepared them well for Tier 1 behavior management, including relationship building, parent communication, rules and procedures, classroom setup, and positive reinforcement. However, they felt that their EPPs inadequately prepared them to manage Tier 2 and Tier 3 challenging behaviors. Participants described that their self-efficacy and self-perceived performance improved over time, both through experience and by observing and learning from colleagues during and after their EPP experiences. Participants’ successes in behavior management stemmed from their consistent implementation of behavior management strategies, and participants built positive relationships with their students during and after their EPPs, leading to improved self-efficacy. Lastly, participants reported that receiving high-quality feedback delivered in a supportive manner after the observation experiences led to an improvement in their self-efficacy. The findings underscore how EPP faculty and K–12 campus administrators can more effectively equip educators with behavior management strategies
Structure-informed synthesis of rare-earth intermetallics : geometric descriptors, structure-property relationships and emergent magnetism.
Full text linkThe discovery and design of rare-earth intermetallic compounds have a direct impact and serve as the driving force behind technological advancements in energy applications, cryogenic refrigeration, and quantum networks, among others. In this dissertation, systematic approaches for synthesizing and characterizing quantum materials are emphasized, with a focus on predictive tools and their validation through single-crystal growth and measurements of physical properties.
Here, we target fundamental aspects of materials by design: What dictates the stability of crystal structures of interest, and what role do distinct structural motifs play in key physical properties such as magnetism?
A geometric descriptor (tolerance factor) was developed to predict the stability of the intermetallic pseudo-perovskites, Remeika phases, relying only on the radii of the constituent elements and their arrangement in the unit cell. This systematic approach successfully guided the synthesis of the predicted Yb5Ru6Sn18 and guided the study of Ln5Ru6Sn18 (Ln = Gd, Tb), highlighting the role of geometric frustration and structural disorder in suppressing long-range order and enabling exotic magnetic behavior.
The homologous series Lnn+1MnX3n+1 (Ln = lanthanides, M = transition metals, X = tetrels), a seemingly complex system, was investigated to establish structure–property relationships. By mapping unit cell volume versus valence electron count, an electronic landscape was constructed to delineate regions dominated by RKKY and Kondo effects in the Ce-based BaNiSn3 and CeNiSi2 analogues. Furthermore, by considering the intrinsic compression and expansion of the BaNiSn3 and CeNiSi2-like subunits in the homologous series, we can rationalize the emergence of antiferromagnetism. The work presented in this dissertation demonstrates how simple systematic approaches using quantitative descriptors, electronic landscape maps can lead to design principles of seemingly complex intermetallic systems and therefore achieving platforms for discovering new quantum materials
Simulation and testing of low velocity impact damage and compression after impact for polymer matrix composite laminates.
No full textBarely visible impact damage (BVID) from low-energy impacts may result in severe degradation of strength and stiffness of a polymer matrix composite laminate, yet the mechanisms of damage initiation and propagation are not fully understood. In this research, we propose a three-dimensional finite element (FE) modeling approach to investigate damage mechanisms during a low-velocity impact in laminated carbon fiber reinforced polymer (CFRP) composites. The models incorporate continuum damage mechanics (CDM) with Hashin 3D failure criteria and cohesive zone modeling (CZM). A novel feature introduced includes a Distal Intralaminar Cohesive Zone (DICZ) using finite-thickness cohesive elements to simulate experimentally observed distal intralaminar cracking. Drop-weight impact tests are performed on multidirectional CFRPs and damage was characterized using high-resolution ultrasonic testing (UT) with a novel layer-by-layer quantification algorithm. Our modeling strategy is shown to accurately predict the intralaminar and interlaminar damage, producing shapes, sizes, and depths of damage that are validated with UT results.
Our second study explores several finite element-based approaches to predict the residual strength of post-impact CFRP laminates, aiding structural reliability assessments. Compression-after-impact (CAI) testing with 3D Digital Image Correlation (DIC) was used to validate the numerical models. Additionally, two simplified parametric models, with circular delaminations and through-holes, were also developed. We found that the parametric models offered reasonably accurate predictions, making them suitable for quick, safety-focused assessments.
Recognizing that real-world impacts are often multi-site, like runway debris, hails, etc., the final part of this study investigates the effects of multiple low velocity impacts in both sequential and concurrent modes with impact sites close enough to interact and modify the delamination damage zones. Sequential impact models were experimentally validated, while concurrent impacts were explored parametrically. The influence of resin properties on damage growth was also examined.
The modeling strategies developed in this research, providing a through-thickness visualization of damage during a low velocity impact along with predictions of residual strength post-impact will enhance the understanding of BVID in a CFRP composite laminate and will be a valuable tool for improving structural safety and performance predictions in aerospace and automotive applications