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Cfd Analysis Of A Full Heat Exchanger Between Ammonia And Supercritical Co2 In Aviation Application, Mairah Ahmed

Graduate Studies Theses and Dissertations 2026

The aviation industry’s transition toward lower-carbon propulsion systems has accelerated interest in alternative fuels, including ammonia–hydrogen fuel blends. In this work, a supercritical CO2 Brayton cycle is integrated with the exhaust stream of a turbofan engine to recover waste heat and utilize it for ammonia preheating and cracking. The recovered thermal energy raises the ammonia temperature to the level required for catalytic decomposition, enabling onboard hydrogen production. The proposed architecture combines ammonia cracking with a high-bypass, two-shaft turbofan engine representative of the propulsion system employed on the Boeing 737 MAX 8. This approach addresses the challenges associated with onboard hydrogen …

Pseudo-Boiling Of Supercritical Co2 In A Parallel-Flow Microchannel And A Micro-Jets Impingement Device And Single-Phase And Two-Phase Heat Transfer Of Subcritical Co2 Jets, Pranzal Ahmed

Graduate Studies Theses and Dissertations 2026

Carbon dioxide (CO2) is gaining attention as a low-toxicity, zero-ozone-depletion refrigerant with a global warming potential of 1, making it an attractive alternative to synthetic HFCs/HFOs. Near its critical point, CO2's thermophysical properties change sharply with small shifts in temperature and pressure — a behavior that can be exploited to enhance heat transfer in trans-critical power cycles and electronics cooling. This dissertation experimentally investigates heat transfer during the pseudo-boiling of supercritical CO2 in a parallel-flow microchannel and a micro-jet impingement device, alongside CO2 flow boiling and single-phase water heat transfer in micro-jet impingement. Using microfluidic devices instrumented with embedded resistance …

Charge Transport Modeling Of Multifunctional Molecular Transistors, Romena Akter

Graduate Studies Theses and Dissertations 2026

Distinguishing between the current–voltage characteristic curves associated with different transport mechanisms in a molecular electronic device and an artifact arising from device-level disorder is a central challenge in the study of molecular electronics. Characterizing these mechanisms and connecting them qualitatively to molecular-level orbital alignment, electrode coupling, voltage division, energetic disorder, and reorganization energy requires not only experimental data but also a rigorous theoretical framework for extracting physically meaningful parameters from measured transfer characteristics. This dissertation addresses this challenge in Chapters 2, 3, and 4 by developing and applying four complementary transport models —Simmons tunneling, single-level Landauer, Marcus hopping, and McConnell …

Learning Weibull Loss Severity Models From Truncated And Censored Data, Majed Alkhasha

Graduate Studies Theses and Dissertations 2026

In modern actuarial science and risk management, due to various loss control mechanisms, observed severity losses are typically left-truncated at the deductible, right-censored at the policy limit, and scaled by a pre-specified co-insurance factor. This results in two types of actuarial payment random variables: payment-per-payment (PPP) and payment-per-loss (PPL). To learn ground-up Weibull loss severity models from PPP and PPL sample data, we implement two estimation techniques: Maximum Likelihood Estimation (MLE) and the dynamic Method of Trimmed Moments (MTM). MLE is employed to obtain efficient estimates of the Weibull shape and scale parameters. However, MLE may assign unnecessarily large point …

Robust Deep Learning One-Class Classification, Shahd Alnofaie

Graduate Studies Theses and Dissertations 2026

One-Class Classification (OCC) focuses on learning the characteristics of normal data and identifying observations that deviate from this learned pattern as anomalies. It is commonly used in applications such as medical diagnosis, cybersecurity, industrial monitoring, and fraud detection, where abnormal examples are often rare or unavailable during training. Classical approaches such as SVDD and LS-SVDD describe normal data using a hypersphere. While effective in some settings, these methods rely on shallow representations and can be sensitive to noise and contaminated observations. To address these limitations, this dissertation introduces a Deep LS-SVDD framework that combines hypersphere-based data description with deep neural …

Making Unsafe Sequences Unexecutable: Formal Protocol Enforcement For Cyber-Physical Systems, Arthur Amorim

Graduate Studies Theses and Dissertations 2026

Cyber-physical systems execute physical actions in response to software commands, making their communication protocols a primary attack surface. A stealthy attack is a sequence of individually valid messages that violates a required ordering, driving the system into an unsafe state without malware or protocol violation. Existing defenses examine messages or physical state in isolation, not protocol level sequences, and cannot prevent them. Preventing them requires enforcement that makes unsafe sequences unexecutable at the communication boundary.

Formal methods offer a principled path to enforcement, but no tool spans specification to safe deployed hardware. Model checking automates proofs but has no certified …

Numerical Investigation Of Reacting Flow In Pmma-Fueled Solid Fuel Scramjet Combustors Under Experimental Test Conditions, Hunter Bassett

Graduate Studies Theses and Dissertations 2026

A simplified steady RANS-based numerical study of reacting flow in solid-fuel scramjet combustors is presented to evaluate the ability of commercial CFD frameworks to reproduce key features observed in experimental test sections. The work focuses on solid PMMA fuel in two supersonic combustor configurations: a cavity-assisted flameholding combustor and a variable-angle diverging combustor. The cavity combustor is analyzed as a baseline case and results are compared directly with experimental data. Three combustor geometry states corresponding to ignition, early-burning, and steady-burning conditions are investigated. Meshes are assessed through a systematic grid refinement method to establish grid independence. A novel variable-angle diverging …

Connecting The Existing Fiber Infrastructure To The Future With Antiresonant Hollow Core Fibers, Timothy Bate

Graduate Studies Theses and Dissertations 2026

Optical fiber systems based on solid-core silica waveguides underpin modern telecommunications, high-power laser delivery, precision sensing, and coherent optical systems. However, nonlinear effects, material absorption, and thermal limitations within silica increasingly constrain further scaling in both optical power and transmission performance. Antiresonant hollow-core fibers provide a promising alternative by guiding light predominantly in air, substantially reducing nonlinear interactions, latency, and optical damage while enabling transmission regimes inaccessible to conventional solid-core fibers. Despite rapid advances in antiresonant hollow-core fiber attenuation and power handling, one of the largest remaining barriers to widespread adoption is reliable integration with the existing solid-core fiber ecosystem. …

Sensory And Emotional Impacts On Modern Consumer Experiences, Winter E. Bland

Graduate Studies Theses and Dissertations 2026

This dissertation comprises two essays examining how environmental and psychological stimuli shape consumer experience, attitudes, and cognition. The first essay investigates the joint influence of scent temperature (warm versus cool) and scent arousal (stimulating versus relaxing) on experiential attitudes and cognitive performance in digitally mediated consumption environments. Across multiple lab experiments with biometric validation, findings reveal that these two scent dimensions interact to shape downstream outcomes. Warm, low-arousal scents (e.g., vanilla) enhance consumers' experiential evaluations of digital interactions but do not improve task performance, whereas cool, high-arousal scents (e.g., peppermint) boost cognitive efficiency and accuracy but do not elevate experiential …

An Examination Of The Impact Of School Context And Socioeconomic Status On Agency And Creative Productivity In Gifted High School Students, Elizabeth Bronson

Graduate Studies Theses and Dissertations 2026

This explanatory sequential mixed methods study investigated gifted high school students’ perception of the agency afforded them within school settings, and the relationship between these perceptions and their creative productivity. A sample of 140 students was drawn from a population of 966 identified gifted high school students. These students were contacted via their parents and asked to complete the Agentic Engagement Scale (AES) questionnaire which provided gifted high school students’ perceptions of the agency afforded at school. No significant differences in perceived agency were found across demographic variables, including socioeconomic status and school type. Of the respondents, 10 students were …

A Systematic Review And Characterization Of Privacy Noncompliance In Real-World Applications, Alexander E. Charkiewicz

Graduate Studies Theses and Dissertations 2026

Software applications increasingly rely on user data to provide their functionality, but improper handling of such data can lead to serious privacy noncompliance with applicable regulations and policies. A prominent example is the Facebook–Cambridge Analytica scandal, in which a third-party application collected the personal data of approximately 87 million Facebook users without users' consent. Despite growing attention to privacy compliance, two key challenges hinder the systematic understanding and analysis of privacy noncompliance. First, unlike security vulnerabilities, which have been systematically categorized through taxonomies such as the Common Weakness Enumeration (CWE), privacy noncompliance lacks a technical taxonomy describing how it manifests …

Design, Fabrication Modeling, And Optical Metrology Of Mwir Silicon Metalenses, Weiyu Chen

Graduate Studies Theses and Dissertations 2026

Mid-wave infrared (MWIR) optical systems require compact, broadband, manufacturable components whose performance can be predicted and measured reliably. Silicon metalenses are attractive because silicon combines high refractive index, MWIR transparency, and semiconductor-compatible fabrication. This dissertation develops a scale-bridging design–fabrication-modeling–metrology framework for MWIR silicon metalenses.

A shared full-aperture framework connects meta-atom libraries, physical layout generation, angular-spectrum propagation, point-spread-function calculation, and focal-plane energy metrics. Building on this foundation, the Dispersive Sweatt Model (DSM) incorporates meta-atom dispersion into conventional ray-tracing software, enabling broadband co-optimization of metasurfaces and refractive elements. A process-aware design framework then incorporates scanning electron microscopy (SEM)-measured height–radius relationships produced by …

An Empirical Comparison Of K-Nearest-Neighbors And Logistic Regression Classification Models, Jackson Cushing

Graduate Studies Theses and Dissertations 2026

This thesis presents an empirical comparison of two classification methods: Logistic Regression and K Nearest Neighbors (KNN). The primary objective of this research is to evaluate the strengths and limitations of each method when applied to real-world datasets. Several publicly available datasets on diabetes, breast cancer, heart attack risk, and cardiovascular disease, were analyzed. For each dataset, K Nearest Neighbors models were implemented in the same way logistic regression had already been applied. The results demonstrate that while logistic regression offers interpretable parameter estimates and performs well when the underlying predictor and outcome relationship is approximately linear, however KNN can …

Non-Gaussian Phenomena In Light Scattering And Applications, Shubham Atul Dawda

Graduate Studies Theses and Dissertations 2026

Physical reality is rarely deterministic; which, when probed by electromagnetic fields that also fluctuate, leads to observables that are most efficiently modelled as statistical processes. At equilibrium, this is usually achieved by invoking the Gaussian statistics of underlying physical processes, however, in practice, one often encounters out-of-equilibrium conditions where Gaussian descriptions may not suffice. Such situations are plentiful in nature– from biology to astronomy. This dissertation addresses several non-Gaussian phenomena associated with light scattering, and includes specific models’ derivations, experimental techniques developments, and demonstrations of potential applications. The systematic presentation will consider circumstances that infringe upon specific assumptions of the …

Exploring The Experiences Of Late Age-On-Arrival Multilingual Learners In Postsecondary Education, Robyn D. Ecklund

Graduate Studies Theses and Dissertations 2026

Multilingual learners (MLs) are the fastest growing population in the United States public school system (Biondi et al., 2024; Kanno & Cromley, 2013; Perez & Morrison, 2016; Varghese & Fuentes, 2020). Within this population of students, there is a subset of students that arrive in the United States during secondary school. These “late age-on-arrival” students face significant linguistic, cultural and social challenges in their pursuit of postsecondary success after high school (Kanno, 2021; Kanno & Cromley, 2013; Perez & Morrison, 2016). This interpretative phenomenological analysis sought to answer the research question: what are the lived experiences of late age-on-arrival MLs …

From Designation To Implementation: A Qualitative Study Of Support Structures For Latinx Students At A Hispanic-Serving Institution, Steven A. Freeman

Graduate Studies Theses and Dissertations 2026

This study addresses the persistent misalignment between the enrollment-based designation of Hispanic-Serving Institutions (HSIs) and the extent to which these institutions implement intentional practices that support Latinx student success. As HSIs continue to grow nationally, it is critical to examine whether institutional efforts move beyond symbolic designation toward meaningful “servingness,” particularly given the increasing reliance on these institutions to advance social mobility and educational attainment for Latinx students. The purpose of this qualitative study is to explore the support structures an HSI provides to promote Latinx student success and to examine Latinx students’ perceptions of the effectiveness of these supports. …

Investigating The Impact Of School Leaders’ Leadership Style And Teachers’ Intrinsic Motivation For Improved Science Instruction In Elementary Schools, Leila M. Greene

Graduate Studies Theses and Dissertations 2026

A report by the National Academies of Sciences, Engineering, and Medicine, determined that 69% of U.S. elementary teachers are not prepared to teach science, especially in the areas of earth/space and physical sciences. As a result, some elementary teachers avoid teaching science. School administrators play a key role in providing a supportive environment to inspire and motivate elementary science teachers. For this reason, the study utilized the Self-Determination Theory (SDT), to examine three types of school leadership styles (Transformational, Transactional, and Laissez-Faire) and how they impact the intrinsic motivation for elementary science teachers in three areas including autonomy, competency, and …

Deciphering Ultrafast Photoinduced And Photocatalytic Reaction Dynamics On Oxide Surfaces: Direct Detection Of Radical Intermediates, Fragment Trapping, And Carbon–Carbon, Carbon–Oxygen, And Carbon–Hydrogen Bond Formation Pathways, Aakash Gupta

Graduate Studies Theses and Dissertations 2026

Understanding photoinduced reactions at solid interfaces is essential for advancing heterogeneous photocatalysis, surface photochemistry, and energy conversion technologies. This dissertation investigates the ultrafast dynamics of reactive intermediates, fragment trapping, and radical-mediated bond formation on oxide surfaces using time-of-flight mass spectrometry in conjunction with femtosecond pump-probe spectroscopy. Various experimental findings are validated through collaborations via density functional theory (DFT). By combining temporal, mass, and energy-resolved measurements, this work provides molecular-level insight into the elementary processes governing light-driven surface reactions. The photodissociation dynamics of CH₃I adsorbed on TiO₂(110), TiO₂(100), and amorphous silicon oxide surfaces are examined …

Policy Into Practice: Exploring School Counselors' And School Psychologists' Knowledge And Sensemaking Towards The Application Of Alternative Gifted Identification Criteria For Lower Socioeconomic Students, Brittany E. Hague

Graduate Studies Theses and Dissertations 2026

Persistent underrepresentation of students from lower socioeconomic status (SES) backgrounds in Gifted education reflects long-standing structural inequities embedded in identification policies and practices. In response, many Florida school districts have adopted equity-oriented identification reforms, including universal screening, local norms, and multiple-measure approaches. However, policy equity does not automatically translate into equitable outcomes; rather, it is mediated through the interpretive work of school-based practitioners. Guided by Sensemaking Theory, this convergent mixed-methods study examines how school counselors and school psychologists construct meaning around alternative Gifted identification criteria and how their beliefs, professional judgment, and organizational contexts shape implementation. The study explores how …

Examining Teachers’ Data Usage Using The Teacher Data Use Survey, Natasha L. Hawkins

Graduate Studies Theses and Dissertations 2026

The United States spends approximately 2.7 billion dollars on classroom assessments and local exams for K-12 students (SIMBA, 2019).  However, despite this financial investment and the adoption of data-driven frameworks such as Multi-Tiered System of Support, the U.S. Department of Education found that only 55% of teachers used student data to make instructional decisions (U.S. Department of Education, 2007).  This study aims to explore the psychological and organizational factors that influence teachers’ data use when making instructional decisions.

This study used the Teacher Data Use Survey (TDUS) to investigate the extent that teachers’ use of data could be predicted by …

Integrated Optical Probes For Confocal Scanning Imaging And Adjustable Coherent-Gated Dynamic Sensing, Yonglin Huang

Graduate Studies Theses and Dissertations 2026

Optics and photonics have been one of the most important sciences and technologies that impact modern human life in a big way. For example, fiber-optics for communications and artificial intelligence. Optical probes are critical components for optical imaging and optical sensing technologies that have been actively researched and developed in the past decades. Advanced fiber-optic sensor probes with smaller size, better performance, lower noise, higher photon efficiency, rapid sensing time, and lower cost are needed in many applications, such as nanoscale material science, chemistry, and biomedical fields, etc.  In this project, new fiber-optic sensor probe technologies and integrated micro-optic devices …

Advances In Active And Passive Integrated Photonic Devices On Thin-Film Lithium Niobate, Pooja S. Kulkarni

Graduate Studies Theses and Dissertations 2026

Thin-film lithium niobate (TFLN) has emerged as a powerful platform for integrated photonics, combining the exceptional electro-optic, nonlinear, and optical properties of bulk lithium niobate with the scalability and compactness of planar nanophotonic technologies. Building on these principles, advanced device architectures such as adiabatic dichroic filters have demonstrated exceptional spectral performance spanning over two octaves of bandwidth on the TFLN platform. Beyond reciprocal devices, it also offers promising pathways toward integrated nonreciprocal components. By leveraging broadband filtering structures and advanced nonlinear photonic design strategies, compact and monolithic optical isolators can be envisioned without relying on traditional magneto-optic materials. In the …

Modeling And Mitigating Atmospheric Degradation In Computer Vision With Application In Renewable Energy Prediction, Sumit Laha

Graduate Studies Theses and Dissertations 2026

Weather-induced variability poses significant challenges to the reliability and performance of modern computational systems, particularly those relying on visual perception and environmental prediction. This dissertation focuses on enhancing computer vision and machine learning based predictive models that operate under varying atmospheric conditions. Two representative weather-impacted applications are investigated: image dehazing and solar photovoltaic (PV) power output forecasting. Image dehazing focuses on the restoration of clear, unobstructed visuals from hazy or foggy images, a task that is vital for various applications. On the other hand, photovoltaic (PV) power forecasting aims to predict future solar energy generation based on historical sky images …

Contextual Influences On Algebra 1 Achievement In Florida: A Multilevel Analysis Of Fsa Data And Policy Implications For B.E.S.T., Alberto Leiro Jr

Graduate Studies Theses and Dissertations 2026

This study examined how school-level and district-level contextual factors are associated with Algebra 1 achievement in Florida using a multilevel modeling framework. Drawing on statewide publicly available data from the Florida Standards Assessments (FSA), the analysis included schools nested within districts to account for the hierarchical structure of educational data. School-level predictors included absenteeism, economic disadvantage, English language learner status, student mobility, and the proportion of students with disabilities, while district-level variables included poverty and crime rates. Results from the null model indicated that a meaningful proportion of variance in Algebra 1 achievement was attributable to differences among districts, supporting …

The Perceptions Of Instructional Coaching On Teacher Efficacy And Retention In Elementary Schools, Stephanie Lucas

Graduate Studies Theses and Dissertations 2026

Administrators in a large school district in Central Florida encountered challenges regarding teacher retention and sustainability. Flite STEM coaching, a new instructional coaching model, was developed to support teachers in hopes of reducing those challenges. This model includes coaching cycles that encouraged collaboration and reflective thinking aligned with professional learning. This qualitative study focused on implementing the Flite STEM coaching model with teachers and instructional coaches. The coaching cycle consisted of the following: 1) a pre-observation conference, 2) video observation, 3) post-observation conference with feedback, and 4) a professional learning opportunity. It included DebriefScape Observation Dashboard resources to collect and …

Genuine And Meaningful Black Character Narratives In Video Games, Derek L. Manns

Graduate Studies Theses and Dissertations 2026

The lack of Black representation in video games reflects stereotypes and hollow narratives. Authentic and meaningful design of Black characters allows Black players a reflection of emotional attachments everyone wants when playing a game. Examining racial identities through avatars, critiquing the notion that customization equates to racial inclusivity, limited options and predominant, white-coded protagonists reinforce systemic biases in games (Dietrich, 2013). My Afrofuturistic content analysis framework explores Black culture with a future of speculative fiction. Reimagining the past, present, and future through Black narratives for alternate futures (Womack). Integrating these ideas enhance culture and aesthetics in this dissertation to highlight …

Multi-Scale Drivers Of Beetle Biodiversity In A Rapidly Urbanizing Region, Alessandra Pandolfi

Graduate Studies Theses and Dissertations 2026

As cities continue to expand, designing urban landscapes that balance ecological resilience with biodiversity conservation has emerged as a pressing challenge. This dissertation examines urban ecosystems as complex and dynamic environments shaping plant and animal communities, with a particular focus on ground-dwelling beetles as ecologically significant indicators of environmental change. Conducted across the Orlando metropolitan area, one of the fastest-growing regions in the United States, this dissertation integrates experimental and observational approaches. Specifically, it aims to (1) test sustainable landscaping practices, (2) compare the ecological outcomes of conventional and alternative residential landscape designs, and (3) assess how gradients of urbanization …

Discrete Element Modeling Of Granular Soils: Critical State Behavior Applied To Impact Pile Driving, Esteban Patino Marin

Graduate Studies Theses and Dissertations 2026

This thesis investigates the use of the Discrete Element Method (DEM) to study two complementary aspects of granular soil mechanics: critical state behavior of granular materials and dynamic response of driven piles in sand, both of which are governed by the same particle-scale mechanisms of dilation, contraction, and fabric evolution.

The first examines the critical state behavior and fabric anisotropy of granular soils through DEM simulations of direct shear, direct simple shear, and true triaxial tests. Sphere-cluster particles representative of a uniform sand are used in two assemblages of approximately twenty-five thousand and one hundred twenty-five thousand spheres to evaluate …

Securing The Energy Transition: Cyber-Physical Security And Resilience In Next-Generation Power Systems, Airin Rahman

Graduate Studies Theses and Dissertations 2026

Modern power systems are rapidly evolving into renewable-dominated and digitally interconnected cyber-physical infrastructures due to the increasing deployment of distributed energy resources (DERs), inverter-based technologies, and advanced control platforms. Maintaining reliability under high renewable penetration requires flexible resources capable of shifting energy across extended time horizons. Long-duration energy storage (LDES), particularly hydrogen-based energy systems, has therefore emerged as an important enabler of renewable integration, grid flexibility, and resilience. However, the growing dependence on communication, sensing, and distributed control also expands the cyber-physical attack surface of modern power systems, creating security and resilience challenges that conventional operational paradigms were not designed …

Advancing Cyber-Physical Security And Resilience Of Modern Power Systems: Intelligent Monitoring, Secure Operation, And Resilient Recovery, Md Moshiur Rahman

Graduate Studies Theses and Dissertations 2026

Modern power distribution systems are rapidly evolving into cyber-physical, DER-rich, and data-driven networks that rely on extensive sensing, communication, automation, grid-edge intelligence, and operator decision support. While this transformation improves flexibility, observability and controllability, it also expands the cyber-attack surface and increases the risk that cyber intrusions can propagate into physical disturbances, compromised DER operation, degraded situational awareness, and interrupted service continuity. This dissertation advances the cyber-physical security and resilience of modern distribution systems by developing a high-fidelity real-time cyber-physical hardware-in-the-loop testbed using OPAL-RT, EXata CPS, industrial relays, SCADA/RTAC, HMI, and grid-edge devices to emulate realistic DER-integrated distribution grid operation. …