Physical Sciences and Mathematics Commons^™

A Density Functional Theory Study Of Palladium Nanoparticles And Their Redox Properties On Graphene, Billie A. Radcliffe

Theses and Dissertations

Nanoparticles exhibit characteristics that are different from bulk materials as well as from atoms resulting in their application in numerous fields of applied material science. In particular, small palladium nanoparticles supported on graphene have been found to be outstanding catalysts for the Suzuki cross-coupling reaction. One explanation as to why these supported nanoparticles are such outstanding catalysts is because they may act as both electron donors and acceptors. Charge donating ligands are known to lower the ionization energy of clusters, making the clusters better donors. In this project, it is hypothesized that graphene supports may also act like charge donating …

Mechanistic Study Of C-H Activation By Iridium Complexes, Rozalie S G Corea

Theses and Dissertations

C-H activation is considered the “holy grail” of chemistry. Remote, selective C-H activation has many applications such as modifying precursors, adding complexity to molecules, and modifying pre- existing structures in a reduced number of steps. Previous work by Swift and Gronert identified an iridium(III) phenanthroline complex that can activate C-H bonds of cyclohexane. The objective of this dissertation is to study the mechanism and regioselectivity of this complex in common precursors, namely 1-butanol, 1-methoxybutane and butyl acetate.

The studies were carried out in the gas phase on a modified mass spectrometer. Selectively deuterated alcohol, ether and ester were used to …

Phenotype Extraction: Estimation And Biometrical Genetic Analysis Of Individual Dynamics, Kevin L. Mckee

Theses and Dissertations

Within-person data can exhibit a virtually limitless variety of statistical patterns, but it can be difficult to distinguish meaningful features from statistical artifacts. Studies of complex traits have previously used genetic signals like twin-based heritability to distinguish between the two. This dissertation is a collection of studies applying state-space modeling to conceptualize and estimate novel phenotypic constructs for use in psychiatric research and further biometrical genetic analysis. The aims are to: (1) relate control theoretic concepts to health-related phenotypes; (2) design statistical models that formally define those phenotypes; (3) estimate individual phenotypic values from time series data; (4) consider hierarchical …

Modeling The Evolution Of Barrier Islands, Greg Robson

Theses and Dissertations

Barrier islands form off the shore of many coastal areas and serve as the first line of defense, protecting littoral communities against storms. To study the effects that climate change has on barrier islands, we use a cellular model of wind erosion, surface dynamics, beach dynamics, marsh dynamics, and vegetation development. We will show the inhibition of movement when vegetation is present.

Invariance And Invertibility In Deep Neural Networks, Han Zhang

Theses and Dissertations

Machine learning is concerned with computer systems that learn from data instead of being explicitly programmed to solve a particular task. One of the main approaches behind recent advances in machine learning involves neural networks with a large number of layers, often referred to as deep learning. In this dissertation, we study how to equip deep neural networks with two useful properties: invariance and invertibility. The first part of our work is focused on constructing neural networks that are invariant to certain transformations in the input, that is, some outputs of the network stay the same even if the input …

Utilizing Design Structure For Improving Design Selection And Analysis, Ahlam Ali Alzharani

Theses and Dissertations

Recent work has shown that the structure for design plays a role in the simplicity or complexity of data analysis. To increase the knowledge of research in these areas, this dissertation aims to utilize design structure for improving design selection and analysis. In this regard, minimal dependent sets and block diagonal structure are both important concepts that are relevant to the orthogonality of the columns of a design. We are interested in finding ways to improve the data analysis especially for active effect detection by utilizing minimal dependent sets and block diagonal structure for design.

We introduce a new classification …

Electric Field Control Of Fixed Magnetic Skyrmions For Energy Efficient Nanomagnetic Memory, Dhritiman Bhattacharya

Theses and Dissertations

To meet the ever-growing demand of faster and smaller computers, increasing number of transistors are needed in the same chip area. Unfortunately, Silicon based transistors have almost reached their miniaturization limits mainly due to excessive heat generation. Nanomagnetic devices are one of the most promising alternatives of CMOS. In nanomagnetic devices, electron spin, instead of charge, is the information carrier. Hence, these devices are non-volatile: information can be stored in these devices without needing any external power which could enable computing architectures beyond traditional von-Neumann computing. Additionally, these devices are also expected to be more energy efficient than CMOS devices …

Regional Drivers Of Organic Carbon Age In Lotic Systems Of The Conterminous United States, Kaycee Faunce

Theses and Dissertations

Rivers play a critical role in global carbon (C) budgets despite their comparatively small surface area. A significant portion of the terrestrial C that they receive is transformed, re-mineralized, or stored during transit to the ocean. Radiocarbon (∆¹⁴C) data show that a fraction of riverine organic C (OC) has been pre-aged in the terrestrial environment. Lateral export of carbon from these aged pools may contribute to atmospheric carbon dioxide emissions through microbial and photochemical oxidation. However, little is known about the regional climatic, anthropogenic, and landscape factors that promote the mobilization of aged OC to rivers. This study …

Enhancing Cybersecurity By Generating User-Specific Security Policy Through The Formal Modeling Of User Behavior, Arwa Alqadheeb

Theses and Dissertations

Despite the ongoing efforts to develop cutting-edge security solutions, the question always remains whether these technologies can overcome system vulnerabilities that often result from poor security practices made by end-users. Recently, some research devoted to study the human role in cybersecurity, especially the psychological aspect. Researchers found that the users’ responses to security-related situations correlate with various elusive factors such as demographics, personality traits, decision-making styles, and risk-taking preferences. That explains why some users neglect to act according to common security tips and advice. The goal of this research is to make cybersecurity maintain a high-level of quality and reliability; …

Factors That Influence The Perception Of Higher Education Leaders In The Adoption Process Of Instructional Technology And Distance Education, Diego Tibaquirá

Theses and Dissertations

The problem addressed by this study was that many administrators at institutions of higher learning are faced with the task of finding ways to provide the latest technologies while being extremely constricted by budgets and the rising cost of education. The purpose of this study was to determine the factors that influence the perceptions of higher education leaders in the adoption process of Instructional Technology and Distance Education. This included an examination of the decision-making process and what determined if Instructional Technology and Distance Education were either implemented or upgraded at various higher learning institutions.

The researcher implemented a mixed-methods …

The Effects Of A Computer Based Program On Student Mathematics Achievement Within An Urban Middle School In Georgia, Sheree Barnes

Theses and Dissertations

The purpose of this quantitative study was to investigate the effects of adaptive computer-assisted instruction (CAI) on student mathematics achievement. The researcher sought to describe factors that may influence academic achievement for eight-grade students. The instruments used to gather data were post curriculum-based mathematics benchmark assessment data administered during fall, winter, and spring semesters, the spring mathematic assessment for the Georgia Milestones, and open and close-ended questionnaires. A purposeful sampling of 63 students were chosen to complete questionnaires. Data analyzed from the 2018 Mathematics scores from SchoolCity and the Georgia Milestones revealed that the SuccessMaker® online adaptive software tool positively …

Interaction, Collaboration And Content Creation In Informal Online Learning Environments: Multidimensional Analyses Of Longitudinal Data From The Scratch Coding Community, Seung B. Lee

Theses and Dissertations

Despite rising levels of participation by children and adolescents in large, informal online learning communities, there has been limited research examining the role that social dynamics play on the online behavior of young users. In this context, this mixed-methods longitudinal study aimed to investigate the relationship between interaction, collaboration and content creation through the analysis of user-generated comments and log-data from the Scratch platform. The research focused on more than 45,000 comments associated with the online activity of 200 randomly selected participants over a period of three months in early 2012. A combination of methodological techniques was applied in the …