Digital Commons Network^™

Development Of A First-Generation Prototype Laboratory System For Rail Neutral Temperature Measurements, Ellie Yi-Hsien Chao

Theses and Dissertations

Modern railway tracks worldwide standardize the use of Continuous Welded Rail (CWR) due to its ability to prevent disadvantages associated with rail joints in a track. CWR is laid when the rail is free of thermal stresses, also known as Rail Neutral Temperature (RNT). RNT is controlled in the CWR installation procedure; however, over time, the temperatures deviate from the RNT. The deviation causes significant thermal stresses introduced in the longitudinal direction of the rail, leading to potential failures such as pull-apart and buckling, causing track integrity and safety of train operation. The most significant potential failure is track buckling …

Planning And Teaching For Student Learning In Mathematics: How Graduate Student Instructors Develop And Implement Instruction, Jennifer S. Crooks-Monastra

Theses and Dissertations

The purpose of this study was to explore undergraduate mathematics teaching from the perspective of a graduate student serving as a first-time precalculus instructor of record. A multiple case study was designed to follow three mathematics graduate student instructors (MGSIs) through one semester of teaching to understand their goals for student learning, efforts to achieve these goals, influences on planning, and to identify challenges they encountered. For each MGSI, data collection included four interviews, three observations of teaching, weekly journal entries, and written assignments from a pedagogy course. A focus group, field notes from the pedagogy course, audio from mentor …

Combined Effects Of Welding Residual Stress And Thermal Expansion In Cwr, Brennan Gedney

Theses and Dissertations

Continuously welded rail with flash-butt welded joints has become standard practice for railway construction around the world. Through the process of welding, a residual stress field develops in the joint which typically remains in the rail through its service life. Consequently, the total stress is altered locally in the presence of operation induced stresses. One such stress develops due to thermal expansion of the rail during the daily and seasonal solar radiation heating cycle. This paper seeks to ascertain the combined effects of welding residual stress with thermal expansion through computer simulations. This is aimed at two objectives: determining whether …

Student’S Perspectives Of Chronic Absenteeism In A Suburban High School, Herbert Allen Gray

Theses and Dissertations

For many students, school attendance is a critical issue. There have been several studies conducted concerning attendance numbers. These studies have shown that poor attendance often affects grades, graduation rates, and socioeconomic status post-high school. The purpose of this study was to first investigate the reasons behind absences and attitudes towards school and classes because of missed days. The second purpose was to determine if a weekly mentoring meeting had any noticeable effect on attendance. The targeted pool of students consisted of those who had been identified as chronically absent the previous semester. An initial set of open-ended questions and …

Impact Of Student-Led Discussions On Student Engagement And Involvement, Samantha Hefel

Theses and Dissertations

The purpose of this action research was to investigate the relationship between student engagement and student-led discussions for middle school students, focusing specifically on seventh graders. There was increased student engagement for the students that participated in the discussions. The study was based on both cognitive and social constructivism, where students are developing their critical thinking as well as socializing with their peers. This research explored three questions related to the impact of student-led discussions. The first question looked at how discussions impacted student engagement and involvement. The second question centered on students’ willingness to voice their ideas. Finally, the …

Evaluation Of A Trigonometric Grey Model For Estimating And Predicting Pavement Condition, Amara Kouyate

Theses and Dissertations

States, counties, and municipalities rely on pavement performance curves to forecast future pavement conditions in their jurisdictions. Accurate prediction is essential for budget planning and the identification of candidates for rehabilitation. This study investigates the use of a grey model (GM) to estimate and predict pavement conditions. An advantage of the GMs is that they do not require a large sample size for model estimation. This aspect is important since smaller towns and municipalities often cannot afford to collect pavement condition data frequently due to cost. There are other situations where sample size may be limited, such as using project-level …

Bayesian Calibration Of The Icrp Zirconium Biokinetic Model And Use Of Canned Priors For The Evaluation Of Bioassay, Thomas Raymond Labone

Theses and Dissertations

The International Commission on Radiological Protection (ICRP) publishes biokinetic models that relate measurements of radioactive material in the body and excreta (bioassay) to the amount of the material taken into the body (intake). Given the intake and the biokinetic model, radiation dose to organs and tissues can be calculated. The ICRP approximates the biokinetics of radioactive materials in the body with compartmental models expressed mathematically as a system of ordinary differential equations, for which they provide point estimates of the rate constants. Inaccurate estimates of intake and radiation dose can result in cases where the biokinetics of an individual differ …

Satellite Observations And Spatiotemporal Assessment Of Salt Marsh /Dieback Along Coastal South Carolina (1990-2019), Huixuan Li

Theses and Dissertations

Coastal wetland mapping is often difficult because of the heterogeneous vegetation compositions and associated tidal effects. Past studies in the Gulf/Atlantic coast states have reported acute marsh dieback events in which marsh rapidly browned and thinned, leaving stubble of dead stems or mudflad with damaged ecosystem services. Reported marsh dieback in South Carolina (SC), USA, however, have been limited. Previous studies have suggested a suite of possibly abiotic and biotic attributes responsible for salt marsh dieback. However, there are no consensus answers in current literature explaining what led to marsh dieback in past decades, especially from the spatiotemporal perspective. In …

Advancing Research Methodology And Educational Policy: An Application Of Mixture Modeling Using School Climate, Kathleen V. Mcgrath

Theses and Dissertations

School climate is a well-studied issue in educational research. However, surveys of school climate tend to be analyzed using item-centered as opposed to person-centered methods. The current study evaluated the 2018 South Carolina School Climate Survey using advanced applications of mixture modeling in an attempt to identify latent profiles at the student and school levels. The relatively new manual BCH 3-Step approach was applied given its usefulness in analyzing multilevel data with covariates and distal outcomes. However, its application to multilevel mixture models leaves room for advancement and prompted the adoption of an alternative analysis plan that included separate analyses …

Individualized E-Book Experiences: Personalized Reading Plans’ Impact On First-Grade Students’ Reading Motivation And Engagement, Hannah Brunson Miles

Theses and Dissertations

The purpose of this action research was to address the issue of first-grade students being unengaged and unmotivated to read independently for the recommended 20-minute block of time in class. Students were also not electing to read independently during any free time they had in class. This research was designed to investigate how implementing a personalized e-book reading plan (PRP) affected students’ reading motivation and engagement during independent reading. The research questions that guided this study were: (a) How and to what extent do the personalized e-book reading plans impact students’ motivation to read? (b) How and to what extent …

Investigations On The Surface Chemistry Of Colloidal Quantum Dots Towards Fluorescent Biological Probes, John Hardin Dunlap

Theses and Dissertations

Colloidal semiconductor quantum dots (QDs) have garnered significant interest as promising materials for biological applications due to their improved photostability and narrow, tunable photoluminescence properties compared to organic fluorophores. To facilitate their utility as fluorescent bioimaging probes, QDs must undergo post-synthetic modifications to exchange their native hydrophobic ligands from synthesis with hydrophilic ones that enable colloidal dispersions in aqueous environments. Many examples exist that demonstrate surface modifications for water-soluble QDs and their efficacy in biological systems, however, there is a need to develop a more thorough understanding of how hydrophilic ligands coordinate to QD surfaces in order to develop more …

Development Of A Rapid Compression And Expansion Machine To Characterize The Ignition Propensity Of Multi-Component Liquid Fuels, Jonathan Joseph Morreale

Theses and Dissertations

Combustion has been the primary source for energy production, whether it be from coal, oil, or natural gas, for a very long time. With increasing population and therefore an increased demand for energy, efficiency is becoming a concern. In order to increase efficiency, engines have been downsized and compression ratios have been increased. In doing so, problems have arisen such as knock and low speed pre-ignition. To better understand these problems, an investigation into how fuels ignite at higher pressures is necessary. Real fuels are comprised of multiple components that exhibit significant variations in their own physical and chemical characteristics. …

Correcting For Measurement Error In The Outcome When Estimating The Distribution Of Time To Pregnancy With The Current Duration Approach, Nicole Nasrallah

Theses and Dissertations

The current duration approach to modeling time-to-pregnancy (TTP) models the length of pregnancy attempt for women that are currently attempting pregnancy. There is a scarcity of studies, let alone TTP studies, that account for measurement error in the outcome. Previously, the benefits of a piecewise constant model with regards to bias in estimates of the survival function with measurement error and the parametric modelling of TTP was shown. In this thesis, correcting for measurement error in the outcome with the current duration approach is explored through piecewise constant models with log-normal measurement error. Five different methods are compared to determine …

Teaching An Old Dog New Tricks: Synthesis And Applications Of Novel Polybenzimidazole (Pbi) Membranes, Laura Ann Murdock

Theses and Dissertations

Polybenzimidazoles (PBIs) represent a class of performance polymers that display exceptional thermal and oxidative stability. For almost thirty years, PBI membranes have been investigated as promising candidates for next-generation alternative energy devices, including high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) and vanadium redox flow batteries (VRBs). Issues with the production of PBI membranes arise from their inherent low solubility in organic solvents. Thus, conventional approaches typically yield membranes that have limited molecular weight and generate significant waste in preparation, due to the large quantity of solvent required to dissolve PBIs for membrane casting.

Presented herein is the development of …

Sampling And Robustness In Multi-Robot Visibility-Based Pursuit-Evasion, Trevor Vincent Olsen

Theses and Dissertations

Given a two-dimensional polygonal space, the multi-robot visibility-based pursuit-evasion problem tasks several pursuer robots with the goal of establishing visibility with an arbitrarily fast evader. The best-known complete algorithm for this problem takes time doubly exponential in the number of robots. However, sampling-based techniques have shown promise in generating feasible solutions in these scenarios.

Existing sampling-based algorithms have long execution times and high failure rates for complex environments. We first address that limitation by proposing a new algorithm that takes an environment as its input and returns a joint motion strategy which ensures that the evader is captured by one …

Evaluating Fit Indices In A Multilevel Latent Growth Model With Unbalanced Design: A Monte Carlo Study, Fan Pan

Theses and Dissertations

This dissertation informed researchers about the performance of different levelspecific and target-specific model fit indices in Multilevel Latent Growth Model (MLGM) using unbalanced design and different trajectories. As the use of MLGMs is a relatively new field, this study helped further the field by informing researchers interested in using various specific model fit indices.

We evaluated the descriptive information of the various model fit indices under various simulation conditions and the extent to which the fit indices could be influenced by different design factors, based on simulated data with different conditions derived from a correctly specified MLGM. Our simulation design …

A Conductor’S Guide To J. N. Hummel’S Forgotten Oratorio: Der Durchzug Durchs Rote Meer, Rebecca J. Ostermann

Theses and Dissertations

Johann Nepomuk Hummel’s only oratorio, Der Durchzug durchs rote Meer, was lost to the musical world until around 2004. Hummel (1778–1837) was greatly esteemed during his life as a concert pianist and as a composer, and several of his choral works were among those highly regarded by his contemporaries. Interest in his works, along with Hummel scholarship, has increased in the twentieth and twenty-first centuries.

Hummel’s oratorio is for Classical orchestra plus guitar, harp, and bass drum, four to ten vocal soli, and chorus. Its thirteen numbers run about 51 minutes, recounting the biblical story of Moses and Pharaoh, the …

Using Concurrent Functional Regression To Reconstruct River Stage Data During Flood Events And Identify Influential Functional Measurements, Ryan Pittman

Theses and Dissertations

On October 4, 2015, the Cedar Creek gage at Congaree National Park stopped reporting stages, and the readings did not resume until approximately two weeks later because of record-breaking rainfall that led to some of the worst flooding in South Carolina history. Our goal is to reconstruct the Cedar Creek stage during this missing two-week window. The Congaree River gage in Congaree National Park remained functioning throughout the October 2015 flood, when the stage reached its maximum recorded crest. The stages from the two gages are directly related during floods as water travels through the local spillways and flood planes …

Against All Odds: Understanding African American Males’ Perspectives On The Path To Graduation At An Alternative School, Devin Randolph

Theses and Dissertations

The researcher completed a critical, descriptive, single case study about African American male students' experiences on the path to graduation at an alternative school in the southeast. Informed by scholarship on majoritarian narratives and counter narratives from Critical Race Theory (CRT), the researcher coded and analyzed data from individual interviews, a focus group, and an art-based project to answer three research questions: 1. How do African American males describe their perspectives on their placement at an alternative school? 2. How do African American male students describe their paths to graduation, including defining moments? 3. What and who do African American …

Correct Web Service Transactions In The Presence Of Malicious And Misbehaving Transactions, John Thomas Ravan Iii

Theses and Dissertations

Concurrent database transactions within a web service environment can cause a variety of problems without the proper concurrency control mechanisms in place. A few of these problems involve data integrity issues, deadlock, and efficiency issues. Even with today’s industry standard solutions to these problems, they have taken a reactive approach rather than proactively preventing these problems from happening. We deliver a solution, based on prediction-based scheduling to ensure consistency while keeping execution time the same or faster than current industry solutions. The first part of this solution involves prototyping and formally proving a prediction-based scheduler.

The prediction-based scheduler leverages a …

An Investigation Of The Ignition Propensities Of Fuels Perturbed By Nitrogen Monoxide, Ackmer Robinson Iii

Theses and Dissertations

Quantitative structure property relationship (QSPR) regression models were developed based on the chemical functional group distribution of toluene reference fuels (TRF, mixtures of n-heptane, iso-octane, and toluene) for RON, MON, and DCN. The QSPR regression models were developed using DCN measurements from this study as well as RON/MON data available in literature. The correlations between RON/MON and DCN were analyzed. The ignition propensity of TRFs perturbed by NO addition was also investigated in this study. The interactions between the chemical functional groups and NO were investigated using an ignition quality tester (IQT). It was found that the increase in the …

Supporting The African American Prekindergarten Student Through Standard Academic English Instruction, Trent Gibson Rogerson

Theses and Dissertations

The objective for this research was to determine if prekindergarten African American students would show gains on English language assessments after receiving targeted Standard Academic English instruction. The research question asks, “How can a specialized English language intervention be utilized to identify the strengths and areas of improvement for African American preschool students?” The hypothesis was the students who received targeted instruction in Standard Academic English would perform better on the post-test than on the pre-test given before the instruction period. For this study, eight prekindergarten students were allowed to participate in the research. The students were administered an English …

Catalytic And Non-Catalytic Methods For Hydrocarbon Upgrading, Valorization, And Pollutant Control, Michael Morgan Royko

Theses and Dissertations

This work investigates catalytic and non-catalytic oxidative chemical upgrading and pollutant remediation techniques to responsibly utilize hydrocarbon feedstocks with existing infrastructure as the transition to more renewable and cleaner feedstocks for energy generation are developed. These technologies include oxidative dehydrogenation of ethane, development of magnetically separable catalysts to reduce carbon monoxide emissions during biomass upgrading as well as the subsequent use of the upgraded biomass for partial coal replacement, and electrochemical treatment of a washcoat free wire mesh supported catalyst to reduce carbon monoxide emissions in combustion exhaust.

First, doping of secondary metals in M1/M2 catalysts for oxidative dehydrogenation of …

Insights Into Rational Catalysts Synthesis, Abolfazl Shakouri

Theses and Dissertations

Atomically distributed metal centers with maximized atom utilization efficiency called single-atom catalysts (SACs) have attracted significant attention in catalysis. SACs with the advantages of both homogeneous and heterogeneous catalysts have been rising as a new frontier in the field of catalysis. New catalytic technologies are ever-growing, considering 90% of all chemical processes employ catalysts, securing modern society’s sustainable future. A classical field in catalysis has been dedicated to catalysis by supported metals. Recently, a vast effort has been devoted to smaller catalyst particles where size is restricted to a single atom on a surface. Single atoms supported or embedded on …

The Spatial Variability Of Crime: A Review Of Methodological Choice, Proposed Models, And Methods For Illustrating The Phenomenon, Matthew D. Spencer

Theses and Dissertations

The spatial analysis of crime has occurred for nearly two centuries. Within criminology, research interests that have developed from the use of spatial methodologies seek to identify the spatial variability and concentration of crime. The first focus utilizes spatial statistics and mapping to describe and illustrate spatial variability. The second focus uses statistical techniques to describe levels of concentration such as the percentage of crime attributed to a unit. Due to the larger breadth of work and multiple analytical components the former will be the focus of this research.

This multi-study dissertation explores the methods currently used to study the …

It Takes One To Know One: Authentic Learning And Multiple Literacies In A 100 Level, Technical Writing Classroom, Matthew Sterner-Neely

Theses and Dissertations

At Ciudad Community College (pseudonym) and across the Colorado Community College System, the course competencies for Technical Writing I (ENG 131) have more than tripled to accommodate ENG 131 as a guaranteed transfer course equivalent to ENG 121: English Composition I. Unfortunately, this has had the effect of increasing the workload for students, and the increase in competencies plus the struggle that students already had in meeting course competencies demanded the need for an intervention. The purpose of this convergent, mixed methods, action research study was to examine the effects of authentic learning on the competency levels of technical writing …

Preparation, Characterization And Evaluation Of Rationally Designed Catalysts By Electroless Deposition, Wen Xiong

Theses and Dissertations

In heterogeneous catalysis, it is a proven factor that the surface-specific activity and the catalyst selectivity strongly depends on the active sites which are determined by the composition, size, and shape of the particle. For structure-sensitive reactions favored by specific surface sites, such as corners, steps, or edges, TOF and selectivity can be greatly changed by the size of catalyst particles since the active site distribution will change with the size of the catalysts. Usually, metal particles are synthesized by two methods in industry, namely precipitation and impregnation, which often exhibit a broad size distribution. The grand challenge of colloidal …

Multi-Fidelity Surrogate And Reduced-Order Model-Based Microfluidic Concentration Gradient Generator Design, Haizhou Yang

Theses and Dissertations

The microfluidic concentration gradient generator (μCGG) is an important device to generate and maintain concentration gradients (CGs) of biomolecules for understanding and controlling biological processes. However, determining the optimal operating parameters of μCGG is still a significant challenge, especially for complex CGs in cascaded networks. To tackle such a challenge, this study presents multi-fidelity surrogate and reduced-order model-based optimization methodologies for accurate and computationally efficient design of μCGGs.

The surrogate-based optimization (SBO) method is first proposed for the design optimization of μCGGs based on an efficient physics-based component model (PBCM). Various combinations of regression and correlation functions in Kriging and …

Quantifying And Elucidating The Effect Of Co2 On Aemfcs, Yiwei Zheng

Theses and Dissertations

Anion exchange membrane fuel cells (AEMFCs) have recently received significant attention as a future high efficiency, environmentally friendly energy conversion device. This attention is due to the potential advantages that AEMFCs can offer compared the much more common, and commercialized, proton exchange membrane fuel cells (PEMFCs) – most notably lower cost. However, there are several remaining roadblocks for the AEMFC technology to be widely adopted, such as: i) the stability of the anion exchange membranes (AEMs) and anion exchange ionomer (AEIs); ii) the development of highly active catalysts with either low platinum group metal (PGM) loading or catalysts that are …

Towards More Trustworthy Deep Learning: Accurate, Resilient, And Explainable Countermeasures Against Adversarial Examples, Fei Zuo

Theses and Dissertations

Despite the great achievements made by neural networks on tasks such as image classification, they are brittle and vulnerable to adversarial example (AE) attacks, which are crafted by adding human-imperceptible perturbations to inputs in order that a neural-network-based classifier incorrectly labels them. Along with the prevalence of deep learning techniques, the threat of AEs attracts increasingly attentions since it may lead to serious consequences in some vital applications such as disease diagnosis.

To defeat attacks based on AEs, both detection and defensive techniques attract the research community’s attention. Given an input image, the detection system outputs whether it is an …