Dissertation Defense Announcements

Candidate Name: Christy L Foster
Title: An Analysis of the Small Business Administration's Impact on Job Creation
 March 22, 2024  9:00 AM
Location: Zoom https://charlotte-edu.zoom.us/j/95549796791?pwd=U0J1V01RYkJ2RTU1My9GSGtDenpLQT09

This research investigates the potential endogenous relationship between small business financing provided through the Small Business Administration (SBA) and state-level economic growth, specifically job creation and retention, as causality may be bidirectional. The hypothesized causal relationship was assessed by including an instrumental variable, Certified Development Corporations (CDC), suggesting the influence of the CDC on employment can only occur through SBA approval. Annual governmental data for all US states, including D.C., for the years 2020 – 2022 were used in the analysis. The results fail to show a statistically significant relationship between the SBA loan volume and job creation, which may be attributed to the utilization of limited data, particularly from anomalous years due to COVID. The inclusion of data from an atypical period likely introduced confounding factors that influenced overall findings. However, 2022 results did reach statistical significance at the 0.10 level and the CDC variable consistently returned statistically significant results. These findings serve as an empirical foundation for further research and provide practical relevance and value to the existing body of knowledge used by policymakers for insight into the dynamics of SBA program initiatives.

Candidate Name: Iris McMillan
Title: Project TDV x 3 - An Integrative Data Analysis
 March 20, 2024  10:00 AM
Location: https://zoom.us/j/95367329955?pwd=MFdSUnd0a1d6andOTG5tK2xicUFZUT09

Teen dating violence (TDV) affects an alarming number of adolescents in romantic or dating relationships (Niolon et al., 2015), with sexual minority youth (SMY) at the greatest risk for TDV (Petit et al., 2021). Yet, most available measures of TDV and related risk factors (e.g., attitudes about violence) have been developed for and validated with heterosexual youth only. Similarly, frequently used theories identifying youth at risk for TDV perpetration (e.g., intergenerational transmission of violence framework) have not been tested for SMY. This three-article dissertation addresses these gaps by examining the equivalence of theories and measures foundational for TDV prevention programming leveraging advanced quantitative methods related to psychometric modeling and data aggregation. Article one examined the measurement equivalence of the Conflict in Adolescent Dating Relationships Inventory (CADRI; Wolfe et al., 2001) across heterosexual and SMY. Article two investigated differential item functioning of acceptance of dating violence items across heterosexual and SMY. Article three examined the relationship between exposure to family violence and TDV perpetration, and the extent to which relational violence accepting attitudes mediate this association across studies and among heterosexual and SMY. Findings draw attention to and challenge heteronormativity in dating violence research via the use of novel advanced quantitative methods and implications for future research and practice are discussed within a social-justice oriented framework for quantitative research.

Candidate Name: Kerrie Williams
 March 05, 2024  10:00 AM
Location: https://charlotte-edu.zoom.us/j/94917183600?pwd=aXRabkFPanFXcExSK0h5MEZJaGVodz09

The primary objective of this study is to evaluate the influence of multi-dimensional legitimacy on consumer adoption of autonomous vehicles. This study used a survey to evaluate the results. These findings reflected that legitimacy positively and negatively influences the relationships between UTAUT2 determinants and intention to use. These effects are noted in this study showing the influence of legitimacy on consumer intention to use AV. Legitimacy warrants further investigation.

Candidate Name: Andrea Lashae Kirk
 March 15, 2024  2:00 PM
Location: CIPHER 408

Coral reef ecosystems are supported by diverse mutualisms formed between cnidarians such as corals, sea anemones, and jellyfish and dinoflagellate algae in the family Symbiodiniaceae. These dynamic symbiotic relationships rely on the successful establishment of algal endosymbionts, often from the surrounding seawater, within cnidarian host tissues. Due to the current limitations in cellular and molecular tools in the field of cnidarian-Symbiodiniaceae symbiosis, the mechanisms of symbiosis establishment including infection, proliferation, and maintenance are poorly understood. The aim of this thesis is to uncover the cellular processes essential to cnidarian-algal symbiosis by developing in vitro and in hospite assays across Symbiodiniaceae and cnidarian species. In chapter two, the trophic flexibility of Symbiodiniaceae was explored. Symbiodiniaceae Breviolum minutum grown in vitro with organic nutrients showed stable growth and photosynthetic function when compared to limited nutrient conditions; this suggests that the oligotrophic waters of coral reef ecosystems may drive free-living Symbiodiniaceae into symbiosis with cnidarians. Next in chapter three, a new protocol for single-cell dissociation of cnidarian hosts is introduced and used to determine the localization of the first Symbiodiniaceae photosynthesis mutant ora1. Here, ora1 was found to retain its ability to form symbiosis in cnidarians, indicating that photosynthesis is not required for symbiosis establishment. Finally, the newly generated Symbiodiniaceae green mutant, gr02, is introduced and co-inoculated with the brown wild type B. minutum in the sea anemone Aiptasia to uncover the cellular events contributing to symbiont proliferation. For the first time, two algal genotypes (gr02 and wild type B. minutum) were observed co-localized in a single host cell via dissociation and microscopy but were rare in frequency. These results suggest that algal cell division and primary infections drive the proliferation of symbionts in hospite. Furthermore, the co-inoculation of gr02 with other species of Symbiodiniaceae in three cnidarian hosts (coral, sea anemone, and jellyfish) reveals intracellular localization and possible interaction between symbionts in host tissues. Together, this work lays the foundation for future cellular biological research using Symbiodiniaceae mutants to answer pressing questions surrounding cnidarian-Symbiodiniaceae symbiosis.

Candidate Name: Elmohanad Elsayad
Title: Does Virtuality Matter? A Moderated Model of Project Risks & Performance by Degree of Virtual Communication
 March 01, 2024  10:00 AM
Location: https://charlotte-edu.zoom.us/j/93857253330

ELMOHANAD ELSAYAD. Does Virtuality Matter? A Moderated Model of Project Risks and Performance by Degree of Virtual Communication

(Under the direction of DR. FRANZ KELLERMANNS)

As remote work gains popularity due to the rise of virtual communication tools post the COVID 19 pandemic, understanding its impact on project management is crucial. This dissertation investigates the moderating effect of virtual communication on the relationship between project risks and performance. The study presents robust evidence that virtuality significantly and negatively moderates the influence of organizational risks on performance. These findings offer valuable insights into the complexities of virtual project environments, underscoring the need for strategic virtual engagement in managing project risks to avoid performance detriments. The research contributes to project management literature by delineating when and how virtual tools should be employed to optimize project outcomes

Candidate Name: Farjana Sultana
Title: Densification and Enhancement of Thermomechanical Properties of 3D SiC Using Silica Nanowire Growth Modeling & In-Situ Mineralization Technique
 February 26, 2024  10:00 AM
Location: Duke 324

Silicon carbide (SiC) has excellent thermomechanical properties, and it is one of the most promising candidates for many demanding high temperature applications in military, aerospace, space mirrors, nuclear energy stations, filtering, and furnace. Manufacturing of SiC product is difficult due to its thermochemical and mechanical stabilities. The additive manufacturing (AM) of SiC has drawn a lot of attention in recent years due to these excellent materials properties and diverse applications. Previous studies from our lab have shown that the creation of a silica gel layer on the surface of SiC using NaOH solution activated the surface and allowed 3D printing of SiC using water based binder in a powder bed binder jet printer. The dried silica gel layer binds adjacent SiC particles upon hydration during 3D printing at room temperature. The 3D printed green parts require a secondary surface activation by impregnating in NaOH solution and thermal treatment to enhance density and strength. The secondary surface activation technique creates an additional silica layer on the surface of SiC at room temperature which can lead to the growth of silica nanowire inside the pore of 3D printed SiC parts upon heat treatment. The hypotheses underlying this approach are twofold: (i) maximum growth of the silica nanowires will facilitate densification and mechanical properties, and (ii) The silica gel layer can mediate a strong bond between SiC and silicate minerals such as mullite. This thesis has three main objectives. First to understand the effect of processing parameters including concentration of NaOH, thermal treatment temperature and dwelling time on silica nanowires growth and subsequent density and mechanical properties, second, to develop and validate a mathematical model for silica nanowires’ growth and ceramic strengthening, and the third objective is to examine the role of the silica gel layer and thermal treatment parameters on in situ mineralization of mullite bonding agent for SiC composite. This thesis is structured into two parts: (i) experimentally optimizing the processing parameters for silica (SiO2) nanowire growth inside the pore of 3D printed SiC discs based on quantitative SEM analysis and development of a mathematical growth model for silica nanowire growth, and (ii) creating in situ synthesized liquid mullite as a secondary binder phase for the densification and strengthening of 3D SiC manufactured using powder metallurgy technique.

We found that the silica nanowire growth rate and number density depend on the processing parameters such as NaOH concentration, sintering temperature, and time. Therefore, the goal of the first part of this dissertation is to investigate the effect of the processing parameters on nanowire growth and number density. Utilizing quantitative SEM image analysis and a silica nanowire growth model, the focus is on optimizing processing parameters to achieve maximum nanowire growth and density, ultimately enhancing the densification and mechanical properties of 3D printed SiC components. The silica nanowire was grown inside the pore of 3D printed SiC disc through the vapor solid (VS) noncatalytic mechanism. In this process silica (SiO2) vapor condensed directly onto the SiC particle surface, leading to the nucleation and growth of one-dimensional silica nanostructures. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis were performed on SiC disc prepared via the powder metallurgy technique using NaOH solutions at varying concentrations (5%, 10%, and 20%). The thermal analysis helped us determine the nucleation temperature of silica droplets at 525 °C and crystallization temperature at 800 °C. The effect of NaOH concentrations analysis showed that the nanowire number density (mm-2) as well as the width and length of the nanowires increased according to the concentration of the NaOH used to pretreat 3D printed SiC in the order 20% > 10% > 5%. The optimal combination of NaOH concentration and heat treatment parameters identified for the highest nanowire number density and nanowire growth involved impregnating with 10% NaOH and heat treating at 550 °C for 6 hours and 1100 °C for 4 hours. The resulting sample exhibited a nanowire number density of 55431 ± 9232 mm-2, majority of the nanowires were in the width range of 0.3 µm – 0.6 µm, and length of 25.6 ± 3.3 µm as determined through quantitative SEM image analysis. The compressive strength, density and porosity were found to be 9.86 ± 1.4 MPa, 2.27 gcm-3, and 38.32%, respectively. Subsequently, a mathematical nanowire growth model was developed in order to investigate the growth mechanism and understand the effect of reaction kinetics on the nanowire growth. The model accounted for the reaction kinetics controlling the formation of silica molecule and its subsequent deposition on nanowire top surface contributing to the growth of the nanowire. The change in nanowire length relation with respect to different processing parameters obtained from the model showed a good agreement with the experimental data.

The silica gel layer on the surface activated SiC particles transforms into cristobalite (SiO2) upon heat treatment which serves as a binding agent that holds the SiC particles together. However, cristobalite has relatively poor mechanical strength and thermal properties compared to SiC. Therefore, in the second part of this dissertation, an in-situ mullite binding agent was formed which has superior thermomechanical properties compared to SiO2. Additionally, it has thermomechanical and chemical properties comparable to those of SiC. We have reported on using coal fly ash as a source of alumina (Al2O3) that reacts in situ with the silica (SiO2), oxidation product of SiC. The instantaneous mullite formation on the surface of SiC facilitated due to presence of minor concentrations of metal oxides in coal fly ash, resulted in a strong bonding zone between the two phases at relatively low temperature. In this work, SiC was mixed with coal fly ash at weight ratios of 90SiC/10ash, 85SiC/15ash, 80SiC/20ash, and 75SiC/25ash and sintered at 1400 °C. Measurements of mechanical properties showed that the 85SiC/15ash composition had the highest mechanical strength among samples. XRD analysis showed the phase composition of thermally treated 85SiC/15ash to be 81.8 wt% SiC, 11.4 wt% mullite, and 6.8 wt% cristobalite. SEM-EDX revealed a concentration gradient of Al in the cristobalite which enhanced formation of functionally graded bonding zones between phases and resulted in SiC-mullite composite with high thermomechanical properties. The compressive strength, nanoindentation elastic modulus, and Vickers hardness were 434 ± 20 MPa, 370.9 ± 22.6 GPa, and 11.5 ± 1.2 GPa respectively. The thermal shock resistance test showed high dimensional and mechanical stabilities after quenching in liquid nitrogen (−196 °C) from 1400 °C. The SiC-mullite composite showed low thermal expansion co-efficient from 3.17 x 10-7 /K to 5.615 x 10-6 /K when the sample was heated from 182 K to 354 K. The specific heat capacity, thermal diffusivity, and thermal conductivity were 7.83 ± 0.0014 J/g.K, 1.04 ± 0.013 mm2/s, and 17 W/m.K at 100 °C, respectively. The SiC-mullite composite exhibited moderate electrical conductivity of 3.48 x 10-2 S/m at 1000 °C. The resulting SiC-mullite composite is suitable for high temperature applications such as diesel motor parts, gas turbines, industrial heat exchangers, fusion reactor parts, high-temperature energy exchanger systems, and hot gas filters due to its high mechanical strength and thermal shock-resistance. This work demonstrated the potential of utilizing an in-situ mullite bonding agent instead of silica layer in additive manufacturing of SiC in the powder bed binder jet process for achieving a dense SiC parts with high thermomechanical properties.

Candidate Name: Lanny S. Inabnit
Title: Rural Versus Urban Differences in Hospital Readmissions, Inpatient Mortality, and Cost Among COPD Patients
 March 12, 2024  11:00 AM
Location: Zoom. Please email linabnit@uncc.edu for link

The overall aims of this dissertation were to identify factors that impacted 30-day COPD readmissions, inpatient mortality, and overall cost of care. Differences in area of residence were also assessed for all three outcomes. Finally, comorbidities were analyzed to determine their effects on 30-day readmission rates, inpatient mortality, and total cost of care. This dissertation employed quantitative research and used data from the 2016 Nationwide Readmission Database dataset (NRD) and the 2016 National (Nationwide) Inpatient Sample Database dataset from the Health Care Cost and Utilization Project (HCUP). Descriptive statistics were used to report mean (standard deviation, SD) for continuous variables. Binary logistic regression and multiple logistic regression were used for categorical variables. Chi-square testing was used to determine significance of the association between independent and dependent variables related to mortality. A generalized linear model (GLM) with family gamma, long link and margins command was used in the cost analysis. Findings from these studies outlined several variables that led to increased readmission, increased odds of mortality, and increased overall cost of care. When looking at differences depending on residence; insurance type, hospital location, age, median household income, and certain comorbidities had effects on readmission rates, odds of mortality, and overall costs.

Candidate Name: Chandra Sekhar Goli
Title: Investigation of a Doubly Salient Special Machine with Permanent Magnets in Stator for Electrical Vehicle Traction Applications
 February 13, 2024  2:00 PM
Location: EPIC 2344 (Conference Room)

An in-depth analysis of a distinctive electric machine topology characterized by a doubly salient structure and integrated permanent magnets within the stator is presented in this dissertation. The machine demonstrates high power density (up to 50 kW/L) with capabilities such as a rated torque of 95 Nm at 12,500 rpm and a maximum speed of 37,500 rpm. An analytical model using lumped parameter magnetic equivalent circuits (LPMEC) is developed, examining spatial harmonics and validating results through finite element analysis. A high-fidelity model-based motor drive system employs a field-oriented control approach and introduces a complex vector current (CVC) regulation strategy, enhancing stability compared to classical methods. Comparative analyses highlight the robustness of CVC regulation. Experimental tests have been conducted to validate the analytical outcomes and proposed control methodologies employing an open frame laboratory prototype (OFLP) of the proposed machine and SiC based traction inverter.

Candidate Name: Elenora Haag
Title: Leadership and Context for Comprehensive Internationalization: Senior International Officer Perspectives
 February 21, 2024  1:00 PM
Location: COED 110

In higher education institutions, the Senior International Officer (SIO), described as an
administrator who manages overall internationalization activities, has been identified as the most
important catalyst for campus internationalization. Institutional context, including structural,
cultural, and environmental aspects, can be highly influential in determining the extent to which
internationalization, led and facilitated by the SIO, is realized. This basic qualitative study
examines the intersection of leadership and institutional context as mediators of the
internationalization process, a perspective which is lacking in the current literature on the SIO
To better understand the perspectives of SIOs on how organizational context and culture
shape their roles as implementers of comprehensive internationalization, semi-structured
interviews were conducted with 11 participants currently working in an SIO role at a university
receiving a national award for internationalization. Strategic planning documents serve as a
secondary data source. A qualitative thematic analysis of the interview and documentary data
was performed using an inductive coding process. Findings suggest that the roles of strategist,
networker, and advocate are key to the SIO’s successful navigation of institutional context.
Furthermore, the specifics of each institution’s distinctive context may be more influential for the
SIO’s role than any commonalities between institutions of the same type, as defined by size,
funding model, or Carnegie classification. Implications for professional practice include a
renewed focus for SIOs on the strategic alignment of internationalization with the institutional
mission, the development of sustainable cross-campus networks to raise visibility and manage
perceptions, and a willingness to experiment as a way of demonstrating value to the wider
campus community.

Candidate Name: Syeda Fatema Mazumder
Title: Investigating Novice Programmers' Mental Models
 February 28, 2024  12:30 PM
Location: Woodward Hall 338

Novice programmers are known for holding incomplete and inconsistent mental models. A mental model stores knowledge that reflects a person's belief system, helps determine actions, and facilitates learning. Mental model correctness and consistency are two criteria that make a mental model useful. Though the literature on mental models is rich with more than two decades of research, novice programmers' mental model is understudied in the CS education research community. Guided by the mental model theories from psychology and cognitive science, I investigated novice programmers' mental models of arrays before and after CS1 course instruction. Furthermore, I explored the gap that might exist between students with varying levels of prior programming experience. To that end, by following the theories of mental models, I defined the mental models for Java arrays, including assertions of the array's parts and state changes. I further decomposed the array's parts and state changes into four sub-components each (parts: name, index, type, elements}; state changes: declaration, instantiation, assigning literals, assignment). To elicit the mental model assertions of novice programmers from large CS1 classrooms, I adopted a multiple choice-based questionnaire approach (the Mental Model Test) covering each array's component. I collected responses from novice programmers as they entered a CS1 course and transitioned into a CS2 course. I analyzed participants' mental model assertions based on their correctness and consistency.

The results show that participants' mental model correctness and consistency improved after formal classroom instruction. Moreover, even though improved, I found evidence that the mental model components of the array's state changes were less accurate and consistent than the parts. In addition, participants with prior programming experience had significantly lower mental model correctness and consistency than those with prior programming experience before classroom instruction on arrays. The mental model test highlighted several novice programmers' misconceptions. Over half of our participants held at least one misconception before and after learning arrays in classrooms. Novice programmers mostly held misconceptions about the arrays’ declarations (state change) as incoming CS1 students and when transitioning into CS2. After classroom instruction, the number of students holding misconceptions about the parts components decreased. However, for the state changes components, in most cases, the number of students holding misconceptions remained almost the same even after classroom instruction. I close my dissertation by summarizing the overall findings while investigating novice programmers' mental models in their different learning trajectories. Lastly, I discuss the implications of my research in designing instructional materials for CS educators on possible solutions to mitigate the mental model gap of novice programmers.