Physical Sciences and Mathematics Commons^™

North Korean Cyber Attacks And Policy Responses: An Interdisciplinary Theoretical Framework, Jeeseon Hwang, Kyung-Shick Choi

International Journal of Cybersecurity Intelligence & Cybercrime

No abstract provided.

Fast Magnetic Resonance Image Reconstruction With Deep Learning Using An Efficientnet Encoder, Tahsin Rahman

Open Access Theses & Dissertations

This thesis aims to develop an efficient, deep network based method for Magnetic Resonance Imaging (MRI) acceleration through undersampled MR image reconstruction. Deep Neural Networks, particularly Deep Convolutional Networks, have been demonstrated to be highly effective in a wide variety of computer vision tasks, including MRI reconstruction. However, modern highly efficient encoder structures, such as the EfficientNet can potentially reduce reconstruction times further while improving reconstruction quality. To that end, we have developed a multi-channel U-Net MRI reconstruction network which uses an EfficientNet encoder and a custom asymmetric. The network was trained and tested using 5x undersampled multi-channel brain MR …

Towards Reinforcement Learning Driven Mesh Adaptivity For Second Order Elliptic Problems, Augustine Twumasi

Open Access Theses & Dissertations

Adaptive mesh refinement techniques have become an indispensable tool in achieving accurate and efficiently computed solutions to problems which require impractically fine uniform meshes to obtain an accurate approximation. The adaptive algorithm involves a recursive application of SOLVE-ESTIMATE-MARK-REFINE steps where in particular the step `ESTIMATE' involves computing a posteriori error estimator based on only the numerical solution and the data of the problem. Over the years, several a posteriori error estimators have been developed and successfully applied but often times, the choice of estimator is ill suited for the problem at hand. In this research, we present two estimators namely …

Magnesiothermic Combustion Synthesis Of Nanocrystalline Silicon And Oxidation Kinetics Of Magnesium Particles, Sergio Cordova

Open Access Theses & Dissertations

Magnesium (Mg) is a well-known reduction agent in metallurgy (more specifically, in metallothermy). Recently, magnesiothermic reduction of oxides has been used in self-propagating high-temperature synThesis (SHS) of advanced materials such as ultrahigh-temperature ceramics (UHTC). The magnesiothermic SHS has also been used for the conversion of silica (SiO2) to silicon-based materials for thermoelectric applications. However, since oxidation of Mg releases a lot of heat, the direct use of it as the reduction agent leads to excessively high temperatures and undesirable sintering of the products. We have proposed to use magnesium silicide (Mg2Si) instead of Mg in the SHS of nanostructured silicon. …

Articulating The Importance Of Broader Relevance In Cures: From Definition To Actualization, Nikki T. Donegan

Open Access Theses & Dissertations

Course-based undergraduate research experiences (CUREs) have emerged as a means to foster student' scientific reasoning, promote positive attitudes and motivations toward research, and increase persistence in the science, technology, engineering, and mathematics (STEM) fields. In contrast to prescriptive laboratories, students enrolled in CUREs employ techniques and skills to collaboratively and iteratively address novel questions of broad relevance to audiences beyond the scope of the course itself. While many of the core components of CUREs are perceived to be relatively straightforward, definitionally-speaking, this latter dimension of broader relevance has, in contrast, remained largely ill-defined. In the series of studies presented herein, …

Understanding The Chemical Weathering Rate And Element Mobility Of Soils: Using U-Series, Nd-Sr Isotopes Ree And Quantum Chemistry Computational Simulation, Jiye Guo

Open Access Theses & Dissertations

Soil played as the central role in the interaction of biosphere, hydrosphere, lithosphere and atmosphere and is the heart of earth's critical zone study. The weathering and element mobility of soils have drawn considerable attention in soil studies since the complexity of these processes and the critical influence towards the earth and humanity, e.g., the global carbon cycles and fertilization. However, the interaction between soils and various factors including precipitation, bedrock ages, altitude is not well understood. Basse-Terre Island at French Guadeloupe, a small volcanic tropical island that has steep environmental gradients of bedrock ages, topography and precipitation, can be …

Associations Between Exposure To Air Pollution After A Dust Event And Hospitalizations., Estrella De Jesus Herrera-Molina

Open Access Theses & Dissertations

The Southwestern region has been identified as one of the most persistent dust producing regions of North America. Exposure to inhalable particulate matter (PM10) originating from desertic landscape during dust events/dust exposures (DEs) can reach hazardous levels. El Paso, Texas’s ambient air has reached hazardous levels of PM10 above 4000 μg/m3 with near zero visibility due to these natural events. There are very few prior studies in the southwestern United States pertaining to the associations between exposure to atmospheric aerosol after DEs and hospitalizations, nor are there many epidemiological studies globally in dusty environments where most of the atmospheric aerosol …

Synthesis And Study Of F-Block Complexes Containing Metal-Arene Interactions, Jesse Murillo

Open Access Theses & Dissertations

The f-block elements are of great interest due to the under explored nature of their chemical bonding interactions and their unique magnetic and electronic properties. For the 5f-orbital elements, such as uranium, the f-orbitals are more readily available for bonding than the contracted, core like, 4f-orbitals of the lanthanides. This makes uranium complexes informative probes into the nature of f-(p/d/f) bonding interactions. Recently, it has been shown that a growing subset of complexes possessing supported uranium-arene interactions have the capability to stabilize unusually low valent U(II) molecular species and support novel catalytic activity. In our laboratory, we have begun to …

Computational Investigation Of Nanoparticle Immersion And Selfassembly, Tara Allison Tyler Nitka

Open Access Theses & Dissertations

Both neutral and charged nanoparticles with a variety of compositions, shapes, and sizes have beenpreviously prepared. These nanoparticles have been demonstrated to self-assemble into a variety of superlattices and binary superlattices both in bulk solution and at surfaces of solutions, and the structures formed by self-assembly have been shown to depend on nanoparticle chemistry and charge as well as on whether assembly takes place at a surface or in bulk. Furthermore, the prepared isolated and self-assembled nanoparticles have a number of biomedical, nanotechnology, and industrial applications. In this Dissertation, I present my research on three general topics. First, I will …

Statistical Analysis Of Genetic Sequence Variants In Whole Exome Sequencing Data From Patients With Prostate Cancer, Kelvin Ofori-Minta

Open Access Theses & Dissertations

A single variation in the genetic sequence within the DNA of an organism could easily lead to beneficial, detrimental or neutral effects. Most often than not, these effects are detrimental than beneficial. While many biomedical and bioinformatics studies have been conducted to determine the genetic cause of prostate cancer (PrCa) which is still the second leading cause of cancer related death among men in the United States. An appreciable effort in statistical bioinformatics researches has been directed towards this aim. Through statistical analyses of a set of whole exome sequencing data from patients with PrCa obtained via The Cancer Genome …

Transport, Photoluminescence & Photoconduction Characteristics Of Free Standing Two-Dimensional Γ-Alumina & Titanium Superlattice Doped Two-Dimensional Γ-Alumina Grown By Graphene-Assisted Atomic Layer Deposition, Elaheh Kheirandish

Theses and Dissertations

This study presents a facile high-yield bottom-up fabrication, morphology, crystallographic and optoelectronic characterization of free-standing quasi-2D γ-alumina, a non van der Waals 2D material. The synthesis comprises a multi-cycle atomic layer deposition (ALD) of amorphous alumina on a porous interconnected graphene foam as a growth scaffold and removed next by annealing and sintering the alumina/graphene/alumina sandwich at ~ 800 °C in air . The crystallographic and structural characteristics of the formed non-van der Waals quasi 2D γ-alumina were studied by X-ray diffraction (XRD), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). This analysis revealed the synthesized 2D …

Planetary Processes Active And Ancient: Hollowing On Mercury, Ancient Crust Formation On Mars, And Identifying Mars-Analog Habitats., Michael Steven Phillips

Doctoral Dissertations

This dissertation comprises a thermophysical model that shows elemental sulfur may be involved in the potentially active processes that form enigmatic features called hollows on the Mercurian surface, a suite of remote sensing techniques that unveil anorthositic rocks in ancient martian crust, and deep learning to discover the spatial resolutions necessary to identify astrobiology targets in images of Mars analog landscapes.

On Mercury, hollows are high-reflectance, flat-floored depressions observed nearly globally. Hollows are thought to form via sublimation, or a “sublimation-like” process, but the identity of the sublimating phase is poorly constrained. To better understand which phase might be responsible …

Birds And Bioenergy: A Modeling Framework For Managed Landscapes At Multiple Spatial Scales, Jasmine Asha Kreig

Doctoral Dissertations

This dissertation examines the design and management of bioenergy landscapes at multiple spatial scales given numerous objectives. Objectives include biodiversity outcomes, biomass feedstock yields, and economic value.

Our study examined biodiversity metrics for 25 avian species in Iowa, including subsets of these species related to ecosystem services. We used our species distribution model (SDM) framework to determine the importance of predictors related to switchgrass production on species richness. We found that distance to water, mean diurnal temperature range, and herbicide application rate were the three most important predictors of biodiversity overall. We found that 76% of species responded positively to …

Collector Probe Measurements Of Sol Impurity Accumulation And The Implications Of Sol Flows On The Accumulation Amount, Shawn Zamperini

Doctoral Dissertations

A collector probe in its simplest form is a rod inserted into a plasma so that impurities are deposited onto it. These probes are then removed and analyzed to determine the deposition profile both along the length of probe and across the width of it. This dissertation covers a series of collector probes experiments and accompanying interpretive modelling all with the main goal of providing evidence for long-hypothesized near scrape-off layer (SOL) accumulation of impurities that can lead to efficient core contamination. The structure of this dissertation is as follows. A brief outline of fusion energy and why we need …

Small Commercial And Industrial Electricity Consumption In Las Cruces, New Mexico, Andrew Taylor Yurachek

Open Access Theses & Dissertations

Research examining small commercial and industrial electricity usage patterns have historically received less attention than residential electricity consumption patterns. This study examines electricity as an input to commercial and industrial production in Las Cruces, New Mexico using annual frequency data from 1978 to 2018. Those data examined include labor, per capita personal income, price measures for electricity and natural gas, and weather variables. The long-run and short-run elasticities of the data are then estimated using an autoregressive distributed lag model (ARDL). In the long run, CIS customers in Las Cruces respond to natural gas a complimentary good, and the derived-demand …

Modeling The Spatiotemporal Dynamics Of Active Regions On The Sun Using Deep Neural Networks, Godwill Amankwa

Open Access Theses & Dissertations

Solar active regions are areas on the Sun's surface that have especially strong magnetic fields. Several phenomena that can have significant negative effects on technology and subsequently on human life, such as solar flares and coronal mass ejections (CMEs), are often associated with active regions.Since the physical phenomena underlying the evolution of active regions are still poorly understood, the accurate prediction of solar flares and coronal mass ejections remains an open problem.

Extracting insights from the available datasets of solar activity that can lead to a better understanding of solar active regions has been an important research goal at the …

Timescales Of Impact Melt Sheet Crystallization And The Precise Age Of The Morokweng Impact Structure, South Africa, Gavin G. Kenny, Claire O. Harrigan, Mark D. Schmitz, James L. Crowley, Corey J. Wall

Geosciences Faculty Publications and Presentations

Impact cratering was a fundamental geological process in the early Solar System and, thus, constraining the timescales over which large impact structures cool is critical to understanding the thermal evolution and habitability of early planetary crusts. Additionally, impacts can induce mass extinctions and establishing the precise timing of the largest impacts on Earth can shed light on their role in such events. Here we report a high-precision zircon U–Pb geochronology study of the Morokweng impact structure, South Africa, which appears to have a maximum present-day diameter of ∼80 km. Our work provides (i) constraints on the cooling of large impact …

Fragmentation Theory Reveals Processes Controlling Iceberg Size Distributions, Jan Åström, Sue Cook, Ellyn M. Enderlin, David A. Sutherland, Aleksandra Mazur, Neil Glasser

Geosciences Faculty Publications and Presentations

Iceberg calving strongly controls glacier mass loss, but the fracture processes leading to iceberg formation are poorly understood due to the stochastic nature of calving. The size distributions of icebergs produced during the calving process can yield information on the processes driving calving and also affect the timing, magnitude, and spatial distribution of ocean fresh water fluxes near glaciers and ice sheets. In this study, we apply fragmentation theory to describe key calving behaviours, based on observational and modelling data from Greenland and Antarctica. In both regions, iceberg calving is dominated by elastic-brittle fracture processes, where distributions contain both exponential …

Pervasive Changes In Stream Intermittency Across The United States, Kendra E. Kaiser

Geosciences Faculty Publications and Presentations

Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the …

Unoccupied Aircraft Systems (Uass) Reveal The Morphological Changes At Stromboli Volcano (Italy) Before, Between, And After The 3 July And 28 August 2019 Paroxysmal Eruptions, Jeffrey B. Johnson

Geosciences Faculty Publications and Presentations

In July and August 2019, two paroxysmal eruptions dramatically changed the morphology of the crater terrace that hosts the active vents of Stromboli volcano (Italy). Here, we document these morphological changes, by using 2259 UAS-derived photographs from eight surveys and Structure-from-Motion (SfM) photogrammetric techniques, resulting in 3D point clouds, orthomosaics, and digital surface models (DSMs) with resolution ranging from 8.1 to 12.4 cm/pixel. We focus on the morphological evolution of volcanic features and volume changes in the crater terrace and the upper part of the underlying slope (Sciara del Fuoco). We identify both crater terrace and lava field variations, with …

Performance Comparison Of Imputation Methods For Mixed Data Missing At Random With Small And Large Sample Data Set With Different Variability, Kyei Afari

Electronic Theses and Dissertations

One of the concerns in the field of statistics is the presence of missing data, which leads to bias in parameter estimation and inaccurate results. However, the multiple imputation procedure is a remedy for handling missing data. This study looked at the best multiple imputation methods used to handle mixed variable datasets with different sample sizes and variability along with different levels of missingness. The study employed the predictive mean matching, classification and regression trees, and the random forest imputation methods. For each dataset, the multiple regression parameter estimates for the complete datasets were compared to the multiple regression parameter …

Effects Of Tidal Flooding On Estuarine Biogeochemistry: Quantifying Flood-Driven Nitrogen Inputs In An Urban, Lower Chesapeake Bay Sub-Tributary, Alfonso Macías-Tapia, Margaret R. Mulholland, Corday R. Selden, Jon Derek Loftis, Peter W. Bernhardt

VIMS Articles

Sea level rise has increased the frequency of tidal flooding even without accompanying precipitation in many coastal areas worldwide. As the tide rises, inundates the landscape, and then recedes, it can transport organic and inorganic matter between terrestrial systems and adjacent aquatic environments. However, the chemical and biological effects of tidal flooding on urban estuarine systems remain poorly constrained. Here, we provide the first extensive quantification of floodwater nutrient concentrations during a tidal flooding event and estimate the nitrogen (N) loading to the Lafayette River, an urban tidal sub-tributary of the lower Chesapeake Bay (USA). To enable the scale of …

Toi-2076 And Toi-1807: Two Young, Comoving Planetary Systems Within 50 Pc Identified By Tess That Are Ideal Candidates For Further Follow Up, C. Hedges, A. Hughes, G. Zhou, T. J. David, J. Becker, S. Giacalone, A. Vanderburg, J. E. Rodriguez, A. Bieryla, C. Wirth, S. Atherton, T. Fetherolf, K. A. Collins, A. M. Price-Whelan, M. Bedell, S. N. Quinn, T. Gan, G. R. Ricker, D. W. Latham, R. K. Vanderspek, S. Seager, J. N. Winn, J. M. Jenkins, J. F. Kielkopf, R. P. Schwarz, C. D. Dressing, E. J. Gonzales, I. J. M. Crossfield, E. C. Matthews, Eric L.N. Jensen, E. Furlan, C. L. Gnilka, S. B. Howell, K. V. Lester, N. J. Scott, D. L. Feliz, M. B. Lund, R. J. Siverd, D. J. Stevens, N. Narita, A. Fukui, F. Murgas, E. Palle, P. J. Sutton, K. G. Stassun, L. G. Bouma, M. Vezie, J. N. Villaseñor, E. V. Quintana, J. C. Smith

Physics & Astronomy Faculty Works

We report the discovery of two planetary systems around comoving stars: TOI-2076 (TIC 27491137) and TOI-1807 (TIC 180695581). TOI-2076 is a nearby (41.9 pc) multiplanetary system orbiting a young (204 ± 50 Myr), bright (K = 7.115 in TIC v8.1) start. TOI-1807 hosts a single transiting planet and is similarly nearby (42.58 pc), similarly young (180 ± 40 Myr ), and bright. Both targets exhibit significant, periodic variability due to starspots, characteristic of their young ages. Using photometric data collected by TESS we identify three transiting planets around TOI-2076 with radii of R_b = 3.3 ± 0.04 R …

A Combinatorial Formula For Kazhdan-Lusztig Polynomials Of Sparse Paving Matroids, George Nasr

Department of Mathematics: Dissertations, Theses, and Student Research

We present a combinatorial formula using skew Young tableaux for the coefficients of Kazhdan-Lusztig polynomials for sparse paving matroids. These matroids are known to be logarithmically almost all matroids, but are conjectured to be almost all matroids. We also show the positivity of these coefficients using our formula. In special cases, such as for uniform matroids, our formula has a nice combinatorial interpretation.

Advisers: Kyungyong Lee and Jamie Radclie

Type And Interval Aware Array Constraint Solving For Symbolic Execution, Ziqi Shuai, Zhenbang Chen, Yufeng Zhang, Jun Sun, Ji Wang

Research Collection School Of Computing and Information Systems

Array constraints are prevalent in analyzing a program with symbolic execution. Solving array constraints is challenging due to the complexity of the precise encoding for arrays. In this work, we propose to synergize symbolic execution and array constraint solving. Our method addresses the difficulties in solving array constraints with novel ideas. First, we propose a lightweight method for pre-checking the unsatisfiability of array constraints based on integer linear programming. Second, observing that encoding arrays at the byte-level introduces many redundant axioms that reduce the effectiveness of constraint solving, we propose type and interval aware axiom generation. Note that the type …

Simulation Analysis Of The Snowball Chamber, Thomas Guile

Legacy Theses & Dissertations (2009 - 2024)

Dark matter is non-baryonic, weakly interacting matter that makes up nearly 85% of the mass ofour universe, as seen through many different phenomena such as gravitational lensing and flat galactic rotation curves [48]. There are many experiments across the globe that are working to find these dark matter particles, but despite increasing levels of detector sensitivity, dark matter has been difficult to detect. Because of this, it is possible that dark matter has a lower mass than originally predicted. A new detector, the Snowball Chamber, could be used to aid in this search. By using the light molecule of water, …

Factors Influencing Student Outcomes In A Large, Online Simulation-Based Introductory Statistics Course, Ella M. Burnham

Department of Statistics: Dissertations, Theses, and Student Work

The demand for statistical knowledge and skills is growing in many disciplines, so more students are enrolling in introductory statistics courses (Blair, Kirkman, & Maxwell, 2018). At the same time, institutions are seeking course delivery methods that allow for greater flexibility for students, especially following the onset of the COVID-19 pandemic; therefore, there is more interest in the development and delivery of online introductory statistics courses.

To address this, I collaboratively designed an online introductory statistics course which focuses on simulation-based inference for the University of Nebraska-Lincoln. The course design was informed by the Community of Inquiry framework (Garrison, Anderson, …

Molecular Dynamics Of Nucleic Acids, Proteins, And Their Complexes: From Atomistic And Coarse-Grained Descriptions To New Methodologies, Parth Chaturvedi

Open Access Theses & Dissertations

Computational modeling of biological macromolecules through molecular dynamics (MD) simulations is becoming increasingly useful to interpret the experimental results and guide the future experiments. Over the last decade, MD simulations have become much more powerful and accessible due to advancements in fields of structural biology, computer science and integrated chip design. In this Thesis, I utilize different MD simulation techniques to model interaction of and antiviral mechanisms. Within the framework of nucleic acid modelling, we describe first dynamics of small circular single stranded nucleic acids and highlight key dynamical differences of backbone behavior in solution between DNA and RNA and …

Mechanical Properties Of The High Cholesterol-Containing Membrane: An Afm Study, Nawal K. Khadka, Raju Timsina, Erica L. Rowe, Matthew O'Dell, Laxman Mainali

Physics Faculty Publications and Presentations

Cholesterol (Chol) content in most cellular membranes does not exceed 50 mol%, only in the eye lens’s fiber cell plasma membrane, its content surpasses 50 mol%. At this high concentration, Chol induces the formation of pure cholesterol bilayer domains (CBDs), which coexist with the surrounding phospholipid-cholesterol domain (PCD). Here, we applied atomic force microscopy to study the mechanical properties of Chol/phosphatidylcholine membranes where the Chol content was increased from 0 to 75 mol%, relevant to eye lens membranes. The surface roughness of the membrane decreases with an increase of Chol content until it reaches 60 mol%, and roughness increases with …

Innovative Computational Methods For Pharmaceutical Problem Solving A Review Part Ii: Serious Gaming, Heather R. Campbell, Robert A. Lodder

Pharmaceutical Sciences Faculty Publications

Serious gaming has begun to take a foothold in pharmaceutical problem-solving. Companies such as Akili's Interactive are seeing success in the form of positive clinical trial results and FDA approval of digital therapeutics. Academic researchers have begun exploring novel uses for serious gaming in the way of protein design and more with promising results. This paper provides a review of such topics in addition to topics of game repurposing- repurposing a game originally intended for entertainment into a serious game-such as Minecraft and America's Army. Reviewing these topics this paper shows the utility of serious gaming as a tool for …