Dissertation Defense Announcements

Candidate Name: Fatemeh HadavandMirzaee
Title: Controlling exciton emission direction through Optical spin-orbit interaction with metallic nanogrooves
 April 01, 2024  1:30 PM
Location: Online Please contact fhadavan@charlotte.edu for link.
Abstract:

The recently introduced class of two-dimensional materials, monolayer Transition Metal Dichalcogenides (TMDs), are emerging as highly promising candidates to enhance data transfer capacity in the field of Valleytronics. Strong “atomic spin-orbit interaction” in monolayer TMDs locks spin of electrons to degenerate valleys with different momenta. These locked valley-spin pairs respond differently to different circular polarizations of light. However, this feature vanishes at room temperature. To address this issue, the coupling between the exciton emissions and photonic modes are under extensive investigation.
This dissertation explores the control over TMD valley-polarized emission by coupling the exciton emission to the plasmonic mode. Specifically, we take advantage of the strong coupling between monolayer WS2 and metallic nanogrooves to enhance information routing, thereby achieving higher data capacity.
The first part of this study is focused on analyzing the interdependence between the nanogroove parameters and the coupling condition. In the second part, we will demonstrate the k-space separation of valley excitons in monolayer TMDs through the "optical spin-orbit interaction." This separation implies that the helicity of photons determines a preferred emission direction.
This research can serve as a guideline for designing structures and pave the way to transport and read out the spin and valley degrees of freedom in two-dimensional materials. By addressing current challenges in the field of Valleytronics, it offers guidance for future advancements in this area.



Candidate Name: Sayantan Datta
Title: Prioritized Robotic Exploration with Dynamic Deadlines
 March 29, 2024  2:00 PM
Location: WOODW 335
Abstract:

Autonomous exploration using mobile robots, commonly referred to as robotic exploration, entails simultaneously performing robot perception, localization, and motion planning to explore an unknown environment. Most prior indoor robotic exploration algorithms focus on exploring the entire environment. We consider exploration under deadlines dynamically imposed either by the robot’s battery or by the environment. Such time-sensitive robotic exploration is critical in dangerous environments as it provides vital initial information about the geometric structure and layout of the environment for subsequent operations. For instance, firefighters can utilize an initial map generated by this deadline constrained robotic exploration to rapidly navigate a building on fire. In the presence of deadlines, the robots should identify the semantically significant regions of the environment (e.g., corridors) and prioritize those that enable them to determine the environment's geometric structure and return to the starting position before the deadline.
This dissertation addresses the problem of autonomous exploration in indoor environments with dynamic deadlines. The problem is NP-hard and requires exponential time to solve optimally. Therefore, we present a short-horizon exploration algorithm, the priority-based greedy exploration algorithm, and several long-horizon exploration algorithms; these include adaptations of the orienteering problem and the profitable tour problem for single-robot and multi-robot exploration of unknown environments with dynamic deadlines. Furthermore, we present a test suite of environments and exploration metrics to benchmark the real-world efficiency of exploration algorithms in office-like environments. Our single-robot experiments reveal that the priority-based greedy exploration algorithm, which focuses on exploring semantic regions with higher connectivity, consistently outperforms the baseline cost-based greedy exploration algorithm in terms of environment layout identification and exploration efficiency. Moreover, the priority-based greedy algorithm was found to be on par with the computationally expensive long-horizon exploration algorithms in terms of percent of the area explored within the deadline. Long-horizon exploration algorithms on the other hand exhibit consistent performance with low variance over repeated experiments. Moreover, the multi-robot priority-based greedy exploration algorithm demonstrated better performance compared to the multi-robot baseline exploration algorithm and performed on par with the multi-robot long-horizon based exploration algorithm while being computationally faster.



Candidate Name: Tashika Hamilton
Title: HAMMER TO THE GLASS CEILING: THE EFFECTS OF TELECOMMUTING ON OPPORTUNITIES FOR CAREER ATTAINMENT
 March 26, 2024  3:00 PM
Location: https://charlotte-edu.zoom.us/j/92395051042?pwd=Yk5kMGNqeXJRYUc0WUFKMVJxUXRDdz09
Abstract:

Human Capital Theory has been widely used in academic research to explain the factors that affect career attainment and job promotion potential. According to this theory, investing in human capital can improve career prospects. While previous studies have focused on human and social capital to explain leadership growth within organizations, this research takes a new approach by analyzing telecommuting and how psychosocial support, human capital, and social capital influence employees’ perception of career advancement. In this study, psychosocial support refers to trust, emotional support, and building strong social networks. Education and skills represent human capital, while network ties foster a diverse social level of sponsorship for social capital. All three variables played a role in moderating the relationships between gender, work type, and race as a catalyst for career attainment.

The survey results predicted that women who work from home receive more human capital, which strengthens their career advancement opportunities. Additionally, the results imply that people of color face barriers in achieving career advancement, indicating the presence of a glass ceiling. Career-related support, race, and work type significantly predicted career attainment. These effects provide insights into the dynamics of reaching top management positions within the finance industry.



Candidate Name: Yi Wang
Title: ADVANCING COMMUNITY COLLEGE STUDENT ENGAGEMENT AND SUCCESS: VALIDATION STUDY OF COMMUNITY COLLEGE SURVEY OF STUDENT ENGAGEMENT (CCSSE)
 April 09, 2024  9:30 AM
Location: https://charlotte-edu.zoom.us/j/92443646830?pwd=bWFoaHVPSTVkb3p1bDkrVFlROFhWZz09
Abstract:

This three-article format dissertation presents a comprehensive examination of the 2017 Community College Survey of Student Engagement (CCSSE), focusing on its measurement properties across diverse community college student populations. Study 1 centered on the validity of the internal structure of CCSSE. Exploratory and confirmatory factor analyses showed evidence to support an eight-factor model of student engagement. This model encompasses dimensions such as personal development, interactions with faculty and peers, and institutional support. This study marks a methodological and theoretical shift, advocating for a multidimensional perspective on student engagement in community college. Study 2 employed multi-group confirmatory factor analysis to examine the measurement invariance of the CCSSE across gender, age, race/ethnicity, and enrollment intensity. The results affirmed the CCSSE’s capacity to consistently measure engagement at configural, metric, scalar, and strict levels measurement invariance. This verification underlined the survey’s reliability in capturing authentic group differences. This study also uncovered lower engagement scores among men and part-time students. Study 3 explored the concurrent and predictive evidence of validity of the CCSSE, investigating how engagement indicators correlate with and predict key student success outcomes. It offered new insights into the complex effects of factors such as interaction with faculty and peers and advising services on academic outcomes.



Candidate Name: Wai-Lun Lam
Title: New version of optimal stopping problem
 April 09, 2024  12:30 PM
Location: Fretwell 315
Abstract:

This dissertation contains several new results concerning Moser-type optimal stopping problems. In the simplest case we consider sequence of independent uniformly distributed points X1, X2, · · · , Xn on the compact Riemannian manifold M and give algorithm for the calculation of Sn = maxτ≤nE[G(Xτ )]where G is a smooth function on M and τ is a random optimal stopping time. Description of the optimal τ depends on the structure of G near points of maximum. For different assumptions on this structure we calculate asymptotics of Sn.



Candidate Name: Marcus Leake
Title: AN EXPLORATION OF TEACHER AND STUDENT PERCEPTIONS ABOUT STANDARD UNIFORM POLICIES IN AMERICAN PUBLIC MIDDLE SCHOOLS
 April 01, 2024  10:30 AM
Location: https://charlotte-edu.zoom.us/j/96306146680?pwd=WlRiNEJZS2FBWjI3a0ZXREcvWTJUdz09
Abstract:

This study explored teacher and student perspectives on mandated school uniforms. Debate exists over the appropriateness of uniforms, with some stakeholders suggesting positive outcomes while others bemoan limits on student expression. This study sought to fill a gap in research specific to middle school uniform use by exploring teachers' and students' perceptions. This research also considered the intersection of gender and diversity issues with uniform policies because these topics are becoming more prominent in the discussion. Four focus groups were conducted, two at a suburban school and two at an inner-city school. Findings suggested that teachers and students at the suburban middle school experienced uniforms more positively than their counterparts in the inner city. Additionally, findings indicated that female students had more negative experiences with uniform policies and their enforcement. From a social identity perspective, this study suggests that the group experience of the same uniform could have a positive or negative impact. When people feel the need for a positive group self, they demonstrate ingroup bias, which could help or hamper the implementation of school uniforms. This research helps bridge the gap in empirical literature within the context of social groups and critical theory to offer recommendations for administrators and policymakers regarding school uniforms in public middle schools. Results can direct further research while raising awareness of issues administrators should address when considering the implementation of a school uniform policy.



Candidate Name: Nicole Godlock
Title: FACTORS IMPACTING THE ACTUAL USE OF DIGITAL HEALTH TECHNOLOGIES TO IMPROVE HEALTH OUTCOMES: INTEGRATION OF UTAUT AND THE HEALTH BELIEF MODEL
 April 08, 2024  3:00 PM
Location: https://charlotte-edu.zoom.us/j/99717961443?pwd=OXB4dUNJZm1Xc3FlQlVqTVcrU2NLdz09
Abstract:

In the healthcare domain, the development of digital health technologies, including mobile applications, telehealth, wearables, and portals, have created new avenues to deliver patient care, track chronic illnesses, and distribute health information. Digital health technologies allow physicians and patients to interact outside of the traditional care settings; therefore, increasing access to care for disparate populations. Understanding the factors that impact a patient’s decision to adopt digital health technologies is essential to maximizing the Actual Use of digital health technologies and addressing health disparities. This research integrates the Health Belief Model (HBM) and Unified Theory of Acceptance and Use of Technology (UTAUT) to examine technology use behaviors specifically in the context of healthcare. This study evaluates three independent variables – intention to use, Perceived Health Benefit, and Social Influence to determine their impact on Actual Use of technology. This study also investigates how Trust in Technology and eHealth Literacy moderate the relationship between Actual Use of technology and its antecedents. Data from a sample of adults in the United States (N= 293) provides insights into the relationships of the proposed research model.



Candidate Name: Ahmed Almhawes
Title: Academic Acceleration in Saudi Arabia
 April 09, 2024  2:30 PM
Location: SPCD Conference Room 344
Abstract:

Acceleration is one of the best-supported interventions available to gifted education practitioners internationally. However, the acceleration program in Saudi Arabia is still inchoate and could benefit from additional revision. The purpose of this research was to explore Saudi stakeholders’ perceptions regarding their lived experiences with the acceleration program implemented by the Saudi Ministry of Education beginning in 2014. To investigate, I used a qualitative research design and a phenomenological approach. Using semi-structured interviews, 18 Saudi stakeholders were interviewed within six clusters (i.e., three clusters comprising an accelerated gifted student, their parent, and their teacher, plus another three similar clusters with non-accelerated students). Following a thematic analysis method to categorize and synthesize these stakeholders’ perceptions, this approach revealed that Saudi stakeholders believed acceleration as a program was effective for Saudi gifted students. They perceived it as a convenient option, well aligned with gifted students’ characteristics, and as an appropriate recognition of these students’ superiority and dedication. The program was seen as the best available gifted program option in the Saudi context. Participants commended the acceleration intervention for positively affecting gifted students' academic performance. They believed that it provided challenging learning materials, fulfilled academic needs, and led to high grades, intelligence quotient (IQ) scores, and national standardized test scores. They also highlighted the importance of gaining advanced skills after completion. However, stakeholders also criticized the regulations and nomination procedures for the Saudi acceleration program, stating that the procedures were vague, not transparent, and unfair in geographical and other ways. All stakeholders also described a lack of awareness and preparation among teachers, parents, and students. Differences of opinion regarding the impact of this acceleration intervention on the social and emotional status of program participants also reveals contradictions. While some positive aspects included successful adaptation, balancing old and new friendships, maturity, and improved gifted characteristics, other responses mentioned potential negative impacts like anxiety and the pressure of high expectations from the students’ community. In general, Saudi stakeholders believed that the acceleration program positively impacts gifted students' future lives by enabling them to finish school earlier and more efficiently. Successful acceleration also led to scholarships, participation in national programs, and scientific trips, benefiting both society and these gifted students. Furthermore, the discussion revealed implications for practices and policies to improve the acceleration program’s regulation and implementation. Based on these findings, several future research directions are suggested.



Candidate Name: Sabeeh Irfan Ahmad
Title: Experimental study of femtosecond laser ablation of two-dimensional materials
 April 08, 2024  11:00 AM
Location: Grigg Hall Room 131
Abstract:

The engine of modern society is fueled by information, and the desire to obtain, process and relay it ever more quickly is motivation for scientists to dig deeper into pathways that enable this endgame. The implementation of ever-quicker computer processors, optical fiber-based communications, and Light Radar (LiDar) for climate studies are a small subset that illustrate how ubiquitous the applications of optics are. In this context, the study of 2D materials (2DMs) is important due to the fascinating properties they exhibit that could lead to a plethora of future opto-electronic applications that extend beyond what silicon alone can provide. The story began with graphene due to its high conductivity and tensile strength, but due to the difficulty of switching its conductivity, applications in transistors is limited, and other materials such as the transition metal dichalcogenides (TMDs) MoS2 and WS2, which exhibit a bandgap transition from indirect to direct when going from bulk to monolayer, are being explored. The wide bandgap semiconductor hexagonal boron nitride (hBN) has also been piquing interest. The presence of room-temperature stable excitons detected via various spectroscopies suggests applicability in mainstream field-effect transistors, and current industry direction towards so-called ‘nanosheet’ and ‘nano-wire’ channel transistors serve as prime examples of the relevant applicability of such 2D materials. Quantum computing and valley-tronic applications have also been reported [5], making this class of material exciting to study.
When material dimensions are reduced to the single atomic layer (‘monolayer’) limit, fast carrier dynamics become important that can only be investigated by even faster phenomena i.e., femtosecond ‘ultrafast’ laser pulses. When exposed to intense electric fields, several processes can occur; multiphoton absorption (MPA) which utilizes multiple photons to promote a single charge carrier to the conduction band (CB), tunneling ionization (TI) in which the laser field modifies the inter-atomic potential and allows CB access via tunneling, and avalanche ionization (AI) where inter-carrier impact causes ionization. Together, these strong-field ionization (SFI) processes are subject to significant research effort. If SFI-induced excited carrier populations exceed a threshold, damage occurs via a non-thermal ‘ablation’ process typically used for cutting and patterning.
The objective of this work was to explore the ultrafast optical dielectric breakdown (ODB) behavior of 2DMs such as MoS2, WS2, and hBN. The work involves an investigation of the etalon interference effect that causes differences in the ablation threshold fluence for the same material when placed on different substrates, differences in threshold fluence between different 2DMs, as well as an exploration of laser-induced defects added when multiple ultrafast pulses are incident on the material. ODB for the wide bandgap insulator hBN is also demonstrated and characterized using various imaging modalities and spectroscopies for the first time. Through the findings presented in this work, we begin to unravel some aspects of the nature of ablation, particularly the dominance of avalanche ionization as the key carrier generation mechanism in the ODB process in 2D materials. We also establish femtosecond laser direct writing as a useful tool for the nanopatterning of such 2DMs.



Candidate Name: Deondra S. Gladney-Campbell
Title: A Meta-Analysis of Culturally Sustaining Instructional Effects on African American Students’ Academic and Behavioral Outcomes
 April 08, 2024  9:00 AM
Location: Zoom https://charlotte-edu.zoom.us/j/91450796881
Abstract:

Researchers have identified that inequitable learning experiences for African American students have negatively impacted their educational outcomes in the United States, and culturally sustaining practices offer great promises in supporting African American students. This meta-analysis investigated the effectiveness of culturally sustaining practices on African American students’ academic and behavioral outcomes. This study built on prior attempts to synthesize multiple definitions of culturally sustaining practices with recommendations from the literature aimed directly at African American students. In this dissertation, I first used the existing synthesis to establish a theoretical framework with an operational definition of culturally sustaining practices for African American students (CSPAAS). I then conducted a systematic review to identify group design studies aligned with the components of the CSPAAS framework. Effect sizes were extracted from each individual study and a random effects model was employed to determine the overall effectiveness of CSPAAS interventions. Additionally, I evaluated the included studies for methodological rigor using the Council for Exceptional Children (CEC, 2014, 2023) quality indicators to determine the extent to which CSPAAS interventions could be identified as evidence-based practices. Results revealed CSPAAS academic interventions were highly effective (n = 17; g = 1.01) and CSPAAS behavioral interventions were moderately effective (n = 5; g = 0.5). The CSPAAS practices for both academic and behavioral interventions also met CEC (2014, 2023) criteria to be categorized as evidence-based practices. Implications for future research are discussed.




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