Digital Commons Network^™

On Spectral Density-Based Goodness-Of-Fit Tests For Time Series Models, Biao Zhang

Doctoral Dissertations

The goodness-of-fit tests for time series models have been discussed for years. Most of the current goodness-of-fit tests require the calculation of residuals from the fitted model. Such calculations can be tedious, and in some cases, the tests are even unreliable. Furthermore, most of their results require assumptions that rule out long memory processes, whose autocorrelation decays at a hyperbolic rate as the lag increases and has become popular in time series modeling. In this thesis, a new goodness-of-fit test for time series data is proposed. The test statistic is based on the ratio between the periodogram and the parametric …

Ultralight Axion Dark Matter With Self-Interactions, Noah James Glennon

Doctoral Dissertations

Our Universe is filled with an invisible substance, called dark matter, which dominates the ways in which structures like galaxies form. Ultralight axion (ULA) dark matter is a possible alternative to more common cold dark matter models. Self-interactions in ULA models are often discarded because they are constrained to be very small. However, in my research, I have found that including self-interactions in these models can have a significant impact on what we observe, even when the self-interaction is small. I simulate ULA dark matter with self-interactions and quantify how different phenomena, including isolated soliton oscillations, binary soliton collisions, tidal …

Seismic Soil-Structure Interaction And Foundation Rocking In Unsaturated Ground, Matthew Michael Turner

Doctoral Dissertations

Strong earthquake motions often cause severe damage to buildings and foundation systems, during which the interaction between the soil, foundation, and structure may dominate the seismic response. Most shallow foundations are located on, or embedded in, unsaturated and partially saturated soil deposits. Unsaturated soil layers are particularly common in zones above the water table where water can rise through different mechanisms like capillary action. Additionally, the degree of saturation throughout a soil deposit can vary both seasonally and yearly due to groundwater table fluctuation related to infiltration and evaporation. Properties of soil layers below foundations impact the seismic response of …

Influences Of Students’ Use Of Calculus 1 Signs/Symbols On Students’ Assessment Scores, Phuong Wilk

Doctoral Dissertations

Mathematical notations not only contribute to but also confound the development of the understanding of mathematical concepts (Leinhardt, Zaslavsky & Stein,1990). Inaccurate use of calculus notations is likely to have a significant influence on student conceptual understanding and student assessment scores in the Calculus 1 course. This dissertation study aimed to examine whether or not the relationship between student’s ability to correctly write signs/symbols, interpret signs/symbols and interpret concepts using signs/symbols (students’ use of signs/symbols) and student assessment scores is statistically significant. The relationship between students’ use of sign/symbol and students’ grade performance was also examined under the effects of …

Deep Learning Based Predictive Models For Performance Enhancement In Bio Medical Applications, Sajila Dimagi Wickramaratne

Doctoral Dissertations

The medical field produces large quantities of multidimensional, complex, and often unstructured data. The timely interpretation of medical data is crucial for medical diagnostics. Machine learning applications are increasingly becoming popular with the ever-increasing computational ability and data availability. Machine learning methods can potentially find complicated relationships that may not be apparent in traditional clinical decision rule systems used in medical applications. Models deployed in medical applications need to be reliable, time efficient, and easy to interpret, thus making working with biosignals challenging in some cases.

The first part of the dissertation focuses on building predictive systems using existing data …

Type 3 Adenylyl Cyclase, Neuronal Primary Cilia, And Hippocampus-Dependent Memory Formation, Yuxin Zhou

Doctoral Dissertations

Primary cilia are microtubule-based cellular antennae present in most vertebrate cells including neurons. Neuronal primary cilia have abundant expression of G-protein coupled receptors (GPCRs) and downstream cAMP signaling components such as type 3 adenylyl cyclase (AC3). The deflects of neuronal cilia is associated with many memory-related disorders, such as intellectual disability. Thus far, little is known about how neuronal primary cilia regulate neuronal activity and affect hippocampal memory formation. Episodic memory is thought to be encoded by sparsely distributed memory-eligible neurons in the hippocampus and neocortex. However, it is not clear how memory-eligible neurons interact with one another to form …

Electrodeposition Of Epitaxial Wide Bandgap P-Type Semiconductors And Copper Metal For Energy Conversion And Flexible Electronics, Bin Luo

Doctoral Dissertations

"Epitaxial electrodeposition is a simple, low-cost technology to produce highly ordered materials on single-crystal surfaces. This research focuses on the epitaxial electrodeposition of wide bandgap p-type semiconductors and epitaxial Cu thin films via a self-assembled monolayer for energy conversion and flexible electronics. Paper I introduces the epitaxial electrodeposition of hole conducting CuSCN nanorods onto Au (111) surface, and lift-off to produce flexible and transparent foils. Highly ordered CuSCN could serve as an inorganic transport layer in various opto-electronic devices such as perovskite solar cells, LEDs, and transistors. An ordered and transparent CuSCN foil was also produced by epitaxial lift-off following …

Investigation And Enhancement Of Students’ Conceptions Of Ph Buffers, Mary Alice Woodland Sheppard

Doctoral Dissertations

Understanding how students construct knowledge of pH buffer concepts is essential to developing effective instructional strategies to support student learning. A resource theoretical framework and the phenomenographic method were used to explore 12 general chemistry students’ conceptions of pH buffers using three buffer questions ranging from algorithmic to conceptual. Open coding of student responses revealed a diverse array of resources that varied in productivity and connectedness. A layered resource graph was introduced to visually compare resource activations across question contexts, highlighting some resources as important for all sensemaking about pH buffers, while others were specific to particular topics. The phenomenographic …

Trend Stationary Time Series: Simultaneous Estimation Of Trend And Autocorrelated Errors, Jakub Michel

Doctoral Dissertations

The world of time series analysis is predominantly focused on nonstationary time series, which exhibit various patterns and behaviors that researchers across different industries aim to analyze. Decomposing nonstationary time series into a trend component and a stationary process is a common approach, with trend and stationary process estimation achieved through parametric and nonparametric methods.

Polynomial regression and nonparametric methods, such as Kernels and B-Splines, are employed to estimate the trend. Once the trend is estimated, the residuals are obtained by subtracting the estimated trend from the data, allowing for the fitting of an ARMA stationary process. However, the estimation …

Applied Geochemistry, Geochronology And Biostratigraphy: Case Studies From The 38th Parallel Structures In Missouri And Orange Basin, Offshore Western South Africa, Marissa Kay Spencer

Doctoral Dissertations

"The unique alignment of the Decaturville, Crooked Creek, and Weaubleau geological structures in central Missouri, three of nine known such structures along the 38th parallel in Illinois, Missouri, and Kansas, has puzzled geoscientists for decades. Research using palynology (palynomorphs and particulate organic matter) and radiometric dating of impact spherules were used to constrain age and a relationship between these enigmatic structures and infer their paleoenvironmental conditions. Novel melting damages, unique to impact, were documented in the palynomorphs in all the three structures. Early Ordovician acritarchs with melted processes correlate with ⁴⁰Ar-³⁹Ar stepwise heating age of impact spherules …

A Qualitative Study Of Ableism On The Postsecondary Campus, George Stuart Fuller

Doctoral Dissertations

This study aimed to learn about the experiences and challenges of disabled students on college campuses. The qualitative research gave voice to the nine disabled students so we can hear, in their own words, their lives, successes, failures, most enjoyable aspects of campus life, and the least pleasant parts of the campus environment. Zoom interviews took place with nine undergraduate disabled students, eight with non-visible disabilities and one with visible disabilities, located on four different campuses within the United States. During the nVivo data analysis, three themes emerged. The three themes identified were: the disabled students' connections with the campus, …

Meta-Analysis Of The Effectiveness Of Project-Based Learning Approach On Academic Achievement In Higher Education Worldwide, Ziyu Meng

Doctoral Dissertations

This research study conducted a meta-analysis to integrate the studies that investigated the effectiveness of project-based learning on academic achievement based on a worldwide higher-education population. The researcher explored the variables that previous meta-analysis studies used to evaluate academic achievements, such as student grade point average (GPA), course grades, and test scores, to explore the use of these variables in project-based learning. There were 17 studies in total included in the meta-analysis evaluating the effect size of academic achievement, which was influenced in moderator variable by subject-matter areas, school location, hours of instruction, technology support, and group size. The researcher …

We Are Still Playing: A Meta-Analysis Of Game-Based Learning In Mathematics Education, Thomas Conmy

Doctoral Dissertations

The purpose of this meta-analysis was to investigate the effectiveness of the use of games as part of mathematics instruction on academic achievement in grades Kindergarten to 12 in the United States. There were 17 studies selected for investigation published from 2010 to 2023 that focused on game-based learning and mathematics. This meta-analysis fills the gap in the knowledge by examining classes that are using game based learning across three platforms of instruction: nondigital games, digital on computers, and mobile devices. The findings from this meta-analysis suggest that the usage of game-based learning in a classroom has a positive effect …

Efficient High Order Ensemble For Fluid Flow, John Carter

Doctoral Dissertations

"This thesis proposes efficient ensemble-based algorithms for solving the full and reduced Magnetohydrodynamics (MHD) equations. The proposed ensemble methods require solving only one linear system with multiple right-hand sides for different realizations, reducing computational cost and simulation time. Four algorithms utilize a Generalized Positive Auxiliary Variable (GPAV) approach and are demonstrated to be second-order accurate and unconditionally stable with respect to the system energy through comprehensive stability analyses and error tests. Two algorithms make use of Artificial Compressibility (AC) to update pressure and a solenoidal constraint for the magnetic field. Numerical simulations are provided to illustrate theoretical results and demonstrate …

Advances In Differentially Methylated Region Detection And Cure Survival Models, Daniel Ahmed Alhassan

Doctoral Dissertations

"This dissertation focuses on two areas of statistics: DNA methylation and survival analysis. The first part of the dissertation pertains to the detection of differentially methylated regions in the human genome. The varying distribution of gaps between succeeding genomic locations, which are represented on the microarray used to quantify methylation, makes it challenging to identify regions that have differential methylation. This emphasizes the need to properly account for the correlation in methylation shared by nearby locations within a specific genomic distance. In this work, a normalized kernel-weighted statistic is proposed to obtain an optimal amount of "information" from neighboring locations …

Data Analytics Of Wettability Alteration With Surfactants In Carbonate Reservoirs, Ya Yao

Doctoral Dissertations

"Wettability alteration with surfactants has been widely applied to improve oil recovery in carbonate reservoirs. An effective surfactant huff-puff application design requires comprehensive guidelines about where, how, and when this method could be applied. Besides, traditional methods to design an effective application and optimize surfactant performance are dependent on extensive experiments and are time-consuming. This study is to assist in the design of surfactant huff-puff via statistical methods and machine learning techniques.

In this study, a dataset including 402 effective surfactant imbibition tests is established by collecting information from nearly 50 publications. The dataset provides a foundation for further data …

Design, Modeling And Analysis Of An Ac-Ac Dual Active Bridge Converter, Kartikeya Jayadurga Prasad Veeramraju

Doctoral Dissertations

"The Solid-State Transformer (SST) is gaining attention as an alternative to conventional iron-core transformers in the power electronic community. The power industry's increasing demands for smaller size, higher efficiency, and greater energy density have made the SST an attractive option. Among various power electronic converter topologies, the Dual Active Bridge (DAB) has become popular for its bidirectional power flow capability and galvanic isolation, primarily in the DC application space. Advancements in semiconductor technologies have introduced new bidirectional switches, opening avenues for novel SST topologies. This research investigates the application of the DAB as a single-stage SST and focuses on advancements …

Introduction Of A Variable Inductance Transformer For The Design Of Resonant Power Converters, Angshuman Sharma

Doctoral Dissertations

"Magnetic integration is a hot topic in power electronics that concerns the use of a transformer's leakage and magnetizing inductances purposefully in isolated power electronic converters, thereby giving the opportunity to save the cost and footprint of any additional inductor. This is of prime interest, especially in CLLLC resonant converters which require up to three inductors. For a complete integration of these inductances, the concept of a variable inductance transformer (VIT) is introduced in this thesis. A VIT is an adaptive magnetic structure that facilitates an easy adjustment of both magnetizing and leakage inductances to meet their desired values. However, …

Near-Ir Spectroscopic Analysis Of The Primary Volatile Composition Of Long And Short-Period Comets, Younas Khan

Doctoral Dissertations

"Comets are among the most well-preserved objects that formed in the protosolar nebula ∼4.5 Gyr ago. Hence, they are important for understanding various aspects of the formation, evolution, and habitability of the solar system. Multiple primary volatiles (molecules directly sublimating into the coma from the nucleus) emit via rovibrational transitions in the near-IR, providing opportunities to calculate their abundances. To date, only ∼50 comets have been characterized for their primary volatiles, with the short-period Jupiter-family comets (JFCs) being significantly underrepresented. In contrast, hundreds of comets have been sampled at optical/UV wavelengths, primarily for the composition of daughter species, leading to …

Promoting Enhanced Decision-Making And Proactive Management For Modularization In The Construction Industry Using Risk-Based Approach, Analytical Hierarchy Process, And Graph Theory, Mohamad Abdul Nabi

Doctoral Dissertations

"Modularization is an approach that can potentially mitigate many of the current construction industry’s challenges. Despite the documented advantages of modularization, the industry is still not able to capitalize on its full potential and benefits. The latter is due to the outdated decision-making models that may not reflect the multiple factors involved in modular construction, the unique source of risks associated with modular construction methods, need for continuous improvement, and complex contractual requirements and disputes. As such, the goal is to promote the use of modularization in the construction industry by enhancing decision-making and proactive risk management. The associated objectives …

Essays On Conditional Heteroscedastic Time Series Models With Asymmetry, Long Memory, And Structural Changes, K C M R Anjana Bandara Yatawara

Doctoral Dissertations

"The volatility of asset returns is usually time-varying, necessitating the introduction of models with a conditional heteroskedastic variance structure. In this dissertation, several existing formulations, motivated by the Generalized Autoregressive Conditional Heteroskedastic (GARCH) type models, are further generalized to accommodate more dynamic features of asset returns such as asymmetry, long memory, and structural breaks. First, we introduce a hybrid structure that combines short-memory asymmetric Glosten, Jagannathan, and Runkle (GJR) formulation and the long-memory fractionally integrated GARCH (FIGARCH) process for modeling financial volatility. This formulation not only can model volatility clusters and capture asymmetry but also considers the characteristic of long …

Fluorination Of Rubisco-Mimetic Co2 Capture Systems. Theoretical And Experimental Studies Of Ammonium Ion Acidity Depression And Carbamylation, Brian Michael Jameson

Doctoral Dissertations

"RuBisCO-inspired CO₂ capture and release (CCR) systems featuring amines have been developed for the purpose of reversable CO₂ capture from air. The enzyme active site consists of the tetrapeptide sequence Lys-Asp-Asp-Glu. The Lys sidechain amine undergoes carbamylation and an Mg²⁺ cation stabilizes the resulting carbamate. The N^a-acyl-lysinyl-aspratyl-aspartyl-glutamide (Lys-Asp-Asp-Glu, KDDE) peptide featured maximum capture at pH ≈ 10; a pH region too high for Mg²⁺ ions to remain in solution. This work aims to achieve pKa depression by introducing fluorine in the proximity of the lysine’s sidechain amine. A comparative analysis was made of butylamine, …

Recurrent Event Data Analysis With Mismeasured Covariates, Ravinath Alahakoon Mudiyanselage

Doctoral Dissertations

"Consider a study with n units wherein every unit is monitored for the occurrence of an event that can recur with random end of monitoring. At each recurrence, p concomitant variables associated to the event recurrence are recorded with q (q ≤ p) collected with errors. Of interest in this dissertation is the estimation of the regression parameters of event time regression models accounting for the covariates. To circumvent the problem of bias and consistency associated with model's parameter estimation in the presence of measurement errors, we propose inference for corrected estimating functions with well-behaved roots under additive measurement errors …

Novel Quantum Materials For Spintronic And Opto-Electronic Applications, Ali Sarikhani

Doctoral Dissertations

"Multi-functional quantum materials play a crucial role in the development of spintronics and opto-electronics, as their properties can greatly influence device performance. For instance, in spintronics, materials such as ferromagnetic half-metals, Giant Magnetoresistants (GMR), and magnetic semiconductors have been extensively studied due to their ability to manipulate the spin of electrons for applications in magnetic storage. In opto-electronics, materials such as Diluted Magnetic Semiconductors (DMS) and non-oxide Transparent Conductors (TC) offer advantages such as tunable bandgap and high absorption coefficients, which enable improved device performance.

For this purpose, we have experimentally investigated the compounds that have shown theoretically interesting physical …

Application Of Modeling Methodologies To Improve An Emergency Departments Workflow, Prachita Humane

Doctoral Dissertations

"The healthcare system in the United States is complex and challenging to understand, and the emergency department (ED) serves as a bridge between outpatient and inpatient care. According to the Centers for Disease Control and Prevention, over 130 million people visited emergency rooms in the United States in 2018. The ED is composed of multiple subunits and components that make it difficult to comprehend fully. In this study, a combination of engineering analysis methods was used to identify and understand the issues in the ED.

The first contribution of this research involved collecting data through job shadowing of human entities …

Cfd Analysis For Beyond Bubbly Gas-Liquid Two-Phase Flows In A Large Diameter Pipe, Sungje Hong

Doctoral Dissertations

"Due to the complexity of multiphase flow phenomena, numerical analysis for multiphase turbulent flow is not as reliable as single-phase computational fluid dynamics (CFD). A literature review has revealed that the current efforts on multiphase flow simulation have focused on small diameter channels under very restricted flow conditions and have been conducted without identifying some important procedures. To expand CFD applications to a wide range of two-phase flow conditions in large diameter channels, this study aims to validate the current CFD models for vertical concurrent air-water two-phase flow simulations beyond bubbly flows. First, a numerical model developed to describe dynamical …

Sustainable Development: A Data Analysis Investigation For A New Conceptual Model, Case Study Comparison And Validation Techniques, Tiffanie Marie Toles

Doctoral Dissertations

"The three pillars model for sustainability, often represented with three intersecting circles described as economic, environmental, and social factors with sustainability being at the center is a complex and philosophically open model [1]. As society promotes efforts to reduce carbon impacts, there becomes a need to critically review the models employed for understanding. This research presents a validated methodology, an updated conceptual configuration of sustainability for overall use, as well as a sustainable development performance measurement system. Using the 2020 Sustainable Development Goals Index Data, 232 indicators from 193 countries were used to evaluate the efficacy of using more than …

An Exploration Of Higher Educational Experiences For Mixed Blood American Indian Males In The Santa Clara Valley, Edward Salcedo

Doctoral Dissertations

This dissertation investigates the availability of higher educational opportunities in the Santa Clara Valley for mixed blood American Indian males in the Santa Clara Valley from lower middle class and middle-class backgrounds born between the early 1980’s and early 1990’s who enrolled in community college courses but did not graduate. The study uses Critical Race Theory as the guiding theoretical framework but focuses on Tribal Critical Race Theory pioneered by Brayboy (2005) to understand the educational and societal experiences of American Indian people from their unique ethnic prism. The dissertation uses Red People’s Oral Tradition as the methodology, drawing from …

Longitudinal Measurement Invariance Of Communication Apprehension Scores Among First-Year Undergraduates, Tonya Calloway

Doctoral Dissertations

Testing measurement invariance (MI) is the most practical question to address in any analysis that involves multiple time points and/or groups. MI is a prerequisite to evaluate if an observed true change over time has occurred after an intervention. Communication Apprehension is one of the most widely studied constructs in the field of communication but has not been analyzed for MI. Leaders governing higher education institutions have implemented Quality Enhancement Plans (QEP) that strategically address workforce needs such intervention programs to improve student communication competency. Despite intervention efforts, industry still indicates a high demand for a workforce with communication competency. …

Dynamics Of A Charge Carrier Driven By Oscillating Fields In Materials With Impurities, Dileon Saint-Jean

Doctoral Dissertations

In conductive materials and semiconductors, a charge carrier under the effects of an electric field will suffer collisions due to thermal fluctuations and impurities in the lattice, altering their trajectory. The electronic properties of these materials depend on the nature and frequency of these collisions; thus, they must be accounted for in any model dealing with electrical conduction. Tracking all collisions individually, while it may be possible within certain limits, forces the model to a large degree of approximation. This work introduces a Monte Carlo-based methodology to electrical transport in Ohmic materials that consists of two parts, the utilization of …