Physical Sciences and Mathematics Commons^™

Flooding: Risk Assessment And Its Interaction With Population & Environmental Health, Shivendra Srivastava

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Flood events have significant implications for both population and environmental health. This dissertation aims to explore flood risk and its interaction with humans and the environment. The key questions addressed in this dissertation include improving the existing flood risk framework to better assess population vulnerability and associated risk. Additionally, it explores how interactions among risk components vary across spatial scales and regions, and how these variations influence overall flood risk. The dissertation also investigates how to design a vulnerability component specific to flooding within flood risk estimation. Finally, it answers whether flood-specific vulnerability differs for a population compared to vulnerability …

Ferroelectricity And Multiferroicity In Ultrathin Films Of Unconventional Transition Metal Oxide, Xin Li

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

Ferroic orders of transition metal oxides, such as ferroelectricity and ferromagnetism, are determined by the intercoupling between spin, charge, lattice. Consequently, ferroic epitaxial thin films have attracted wide interest due to the profuse novel phenomena and the great application potentials for modern electronics. However, the mainstream of the study for transition metal oxides has focused on perovskite structure, limiting the understanding and discovery of novel phenomena associate with ferroic orders. In this thesis, the epitaxial films of hexagonal rare-earth ferrites (h-RFeO₃) and fluorite-structure hafnia oxide (HfO₂) are studied comprehensively, providing new experimental and theoretic …

The Scintillator Surface Detector Of The Pierre Auger Observatory, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, B. Fick, K. Nguyen, D. Nitz, Et Al.

Michigan Tech Publications

Data collected so far by the Pierre Auger Observatory have enabled major advances in ultrahigh energy cosmic ray physics and demonstrated that improved determination of masses of primary cosmic-ray particles, preferably on an event-by-event basis, is necessary for understanding their origin and nature. Improvement in primary mass measurements was the main motivation for the upgrade of the Pierre Auger Observatory, called AugerPrime. As part of this upgrade, scintillator detectors are added to the existing water-Cherenkov surface detector stations. By making use of the differences in detector response to the electromagnetic particles and muons between scintillator and water-Cherenkov detectors, the electromagnetic …

Coastal Transition Zone Development Effects On Salt Marsh Ecology, Amanda Mei Pysher

Electronic Theses and Dissertations

The coastal transition zone (CTZ) is a regional gradient linking terrestrial and marine systems, comprising of the terrestrial upland, the marsh-upland ecotone, and estuarine salt marshes. Along all US coastlines, including the South Carolina (SC) coast from Little River to Georgetown, increases in anthropogenic development of terrestrial uplands have altered the historically established vegetation, and various physical, chemical, biological, and geological gradients. Despite the CTZ's ecological importance, the trickle-down effects of terrestrial upland development on associated high marsh habitats remain understudied. Data were collected from developed (DEV) and undeveloped (UND) shorelines across three SC estuarine inlets. Multilevel modeling (MLM) was …

Migratory Patterns Of Juvenile Shortfin Makos (Isurus Oxyrinchus): Evidence Of A Nursery In The Western North Atlantic, Julia A. Crews

Electronic Theses and Dissertations

Shortfin Makos, Isurus oxyrinchus Rafinesque, 1810, are lamnids that have a global distribution in temperate and tropical oceans. Locations of critical early life history events including birthing and nursery areas are unknown or unconfirmed for most populations. The objective of this study was to identify if a nursery area for Shortfin Makos in the northern waters of the Mid-Atlantic Bight using the criteria articulated by Heupel et al. (2007). Satellite tags were used to track the movement of juveniles (<200 cm TL, n=7) up to 5 months. Tag detections (n=882) confirmed that young makos stay in continental shelf waters of the northern Mid-Atlantic Bight off Long Island through the meteorological summer (June–August) and early meteorological fall (September–October) when sea surface temperatures are 18–23°C. There was clear migratory movement from juveniles once sea surface temperatures fell below 15°C. During late fall, some young sharks moved south towards Cape Hatteras, North Carolina, while one shark moved east up to 1,800 km into the open north Atlantic Ocean into meteorological winter. These movement data of juvenile Shortfin Makos combined with multi-year catches and sightings (2018–2024) provide strong evidence for a nursery area in the northern Mid-Atlantic Bight. By identifying a nursery area for Shortfin Makos, knowledge gaps that currently exist for this vulnerable species and support effective management can be closed.

Comparison Of Nutrient Concentrations And Primary Production Indicators Across Plume Fronts, Taylor Dishon

Electronic Theses and Dissertations

Coastal buoyant plumes carry low-salinity waters containing particulate and dissolved terrestrial materials with an abundance of nutrients into the coastal ocean, including inorganic nitrogen and phosphorous. Plume fronts act as transport barriers created from the convergence of a fresher plume with an older, saltier plume or with ambient waters, leading to potential accumulation of phytoplankton and nutrients. This accumulation creates an optimal environment for primary production. The primary goals of this study were: to investigate the distribution of and potential relationships between nutrient concentrations and chlorophyll a across plume fronts of the Winyah Bay River Plume, and examine potential relationships …

Unfolding Particle Detector Effects And Solving Qcd Inverse Problem With Generative Ai, Tareq Saeed Alghamdi

Computer Science Theses & Dissertations

Advancements in artificial intelligence (AI) have revolutionized high-energy physics by enabling generative models to address key detector-related Challenges. This work explores the generative model to mitigate smearing, acceptance, and inefficiency in particle detectors, enhancing experimental precision.

We present a generative model-based framework to model and correct detector distortions. Using the Jefferson Lab CLAS g11 experiment as a case study, our approach successfully unfolds detector effects in multi-particle final states while preserving multidimensional correlations despite complex reaction mechanisms. A key focus is addressing the acceptance problem—accurately modeling detector acceptance without computationally expensive simulations. By training generative model-based framework on simulated detector …

A Multi-Isotope Investigation Of Mammoth Diet, Habitat, And Movement Patterns In The Central Great Plains, U.S.A., Jacob Mccloskey

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

During the Last Glacial Maximum (LGM), the Great Plains in Nebraska consisted of wooded parklands and grasslands, whereas spruce (Picea) forests, parklands, and steppe grasslands dominated east of the Missouri River. I analyzed bulk carbon (δ¹³C), oxygen (δ¹⁸O), and strontium (⁸⁷Sr/⁸⁶Sr) isotopes from tooth enamel in isolated mammoth (Mammuthus) molars to compare diet and movement patterns in two late Pleistocene assemblages: one in Nebraska (n = 24), and one in western Iowa and Missouri (n = 17). Furthermore, I identified a morphometric subset of molars as …

Low-Level Polarimetric Signatures Of Supercells During Ef3+ Tornado Production, Anthony Noah Began

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Most EF3+ tornadoes are produced by supercells. Understanding of microscale features surrounding intense tornado production remains limited. This research aims to determine commonalities in low-level microphysical processes during intense tornado production via polarimetric radar signature assessment with a Python-based algorithm. Polarimetric variables hypothesized to reflect low-level wind profiles such as the differential reflectivity (Z_DR) arc and the Z_DR–K_DP (specific differential phase) separation vector will be investigated. Supercells which produced EF3+ tornadoes will be examined since these tornadoes pose the highest threat. From 2010 to 2024, the United States recorded approximately 19,100 tornadoes which resulted in …

Study Of Ai Applications In Biomedical Data Acquisition, Communication, And Analysis: Cest Mri Acceleration And Ecg Transmissions, Adarsha Bhattarai

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This dissertation investigates the application of artificial intelligence in biomedical data acquisition, communication, and analysis to advance neurological research and to enable the early detection of cardiovascular conditions. Despite significant advances in imaging and physiological modalities, challenges persist. Imaging modalities, such as the chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) technique are challenged by a prolonged data acquisition time and high operational costs. In addition, physiological modalities such as electrocardiogram (ECG) sensors face constraints in providing uninterrupted signal monitoring which is crucial for the timely detection of premature cardiac abnormalities. The primary goal of this work is to …

Evaluation Of Performance Characteristics And Groundwater Contamination Risks Associated With On-Farm Swine Carcass Disposal Via Composting And Shallow Burial With Carbon, Gustavo Castro Garcia

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This dissertation evaluates the performance of three on-farm swine carcass disposal methods: whole carcass composting (WCC), ground carcass composting (GCC), and shallow burial with carbon (SBC), focusing on biosecurity factors and groundwater contamination risks. Foreign animal diseases (FADs), such as African swine fever and classical swine fever, pose severe economic and animal well-being risks if introduced to the United States. With confirmation of an FAD, swine movement will be halted, creating an urgent need for practical, biosecure, and environmentally responsible on-farm disposal strategies for swine carcasses. Nebraska, as a leading swine-producing state, exemplifies the vulnerability of high-density livestock regions to …

Online Prediction Of Streaming Data, Aleena Chanda

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

We present two new approaches for point prediction with streaming data based on a) the Count-Min sketch and b) Gaussian Process Priors with random bias. The methods are intended for the most general case where no true model can be usefully formulated for the data stream. In statistical contexts, this is often called the M open problem class. For the Count Min Sketch method we show that the predicted distribution function ^F converges to F under the assumption that the data consists of i.i.d samples from a fixed distribution function F. To implement the Gaussian Process Prior methods, we used …

Mass Effects On Energy Transfer Paths In Nonlinear Vibrating Systems, Manal Mustafa

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This dissertation examines the role of mass in nonlinear systems, uncovering its role in enabling passive energy redistribution and robust vibration control in both idealized and real-world structures. Focusing on a strongly nonlinear two-degree-of-freedom system, it investigates how changes in mass ratio influence the dynamics of energy transfer, nonlinear normal modes (NNMs), and dissipation behavior.

A number of significant contributions are introduced in this work beginning with the introduction of the frequency-energy-peaks (FE-pks) plot, a novel tool that visualizes how energy flows through the system, revealing transient resonance orbits, internal resonance effects, and effectively capturing the different nonlinear phenomena with …

Reductive And Nucleophilic Cleavage Of Peroxides And Synthesis Of Tocotrienols As Radioprotective Targets, Amber Marie Schuster

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

I. SET CLEAVAGE OF PEROXIDES: INFLUENCE OF REDUCTANT AND PEROXIDE ON THE RATE AND MODE OF ALKOXY RADICAL FORMATION

The reductive cleavage of organic peroxides to generate alkoxy radicals is frequently accomplished via single-electron transfer (SET) from a reductant. Previous reports employ either symmetrical peroxides or peroxides with predictable cleavage behavior, such as peresters. We were interested in how the structure of the peroxide and the nature of the reducing system combine to impact the rate of reaction and the selectivity for alkoxy radical formation during cleavage of unsymmetric peroxides. In this dissertation, one will find the reactions of a …

How Developers Use Type-System Related Programming Language Features, Samuel W. Flint

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Optional type annotations are a popular feature of programming languages that allow developers to omit explicit type information in code while, in some cases, retaining many of the benefits of static typing, such as in-code documentation, improved detection of type errors, or enforcement of code properties. However, how developers use and understand optional type annotations is not clear. The focus of this dissertation is to understand the use and comprehension of optional type annotations.

Optional type annotations are examined through four lenses: first, by examining the evolution of usage in a statically typed programming language (Kotlin, the default language for …

Resilience Of Interdependent Transportation And Healthcare Systems: A Simulation-Driven Framework Incorporating Social Equity And Facility Optimization, S. Yasaman Ahmadi

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

The overarching goal of this dissertation is to develop an integrated, simulation-driven framework to assess and enhance the resilience of interdependent transportation and healthcare systems before, during, and after natural hazards. By examining how spatial disruptions, social vulnerability, operational constraints, and infrastructure interdependencies affect access to and functionality of hospitals, this research offers a multifaceted evaluation of system performance under stress. This dissertation examines the impact of natural hazards, particularly floods, on the interdependent transportation and healthcare systems. The proposed approach combines and advances GIS-based network analysis, graph-theoretical modeling, and discrete-event simulation to evaluate system performance under different scenarios. The …

Analysis Of Graph-Based Decoders For Quantum Low Density Parity Check Codes, Kirsten Morris

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Quantum computing has the potential for radically increased computational ability. However, the physical realization of quantum states are fragile and susceptible to noise and decoherence. For this reason, robust quantum error correction is imperative to achieve quantum computation at scale.

Of particular interest in realizing effective quantum error correction are quantum low density parity check (QLDPC) codes. Classical LDPC codes were invented by Robert Gallager in the 1960s and came in to prominence in the 1990s. Due to Daniel Gottesman’s stabilizer formalism and the invention of Calderbank-Shor-Steane (CSS) codes, we can apply LDPC codes to the quantum setting.

As in …

Multiscale Drivers Of Water Level Fluctuations And Nutrient Availability In Small Intermittent Reservoirs In The Us Midwest, Uchechukwu Vitus Chinatu Ogbenna

School of Natural Resources: Dissertations, Theses, and Student Research

Reservoir dynamics are often captured by fluctuations in water surface elevation, which reflect a complex interplay of hydrologic inputs, climatic conditions, land use influences, and management operations. While water level fluctuations (WLFs) in large regulated systems have been widely studied, the drivers and implications of WLFs in small reservoirs, particularly those fed by intermittent streams, remain poorly understood. Here, we examined the temporal dynamics of WLFs and their relationship with nutrient availability in nine small reservoirs in the U.S. Midwest using daily records from 1985 to 2022. We used water level classification from modified Zscore and transition matrices to assess …

Environmental Controls Of Hail In Quasi-Linear Convective Systems, Cameron A. Barker

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

A study of hail occurrence in quasi-linear convective systems (QLCS), as well as severe weather parameters contributing to the likelihood and intensity of hail, is presented. Rapid Refresh (RAP) proximity soundings for 218 QLCS events from 2012 to 2022 are selected to sample QLCS environments near peak intensity. Study objectives are to assess common environmental parameter spaces that favor hail in QLCSs while connecting these findings to results for supercells. Hail occurrence is also examined in terms of synoptic regime.

Six synoptic regimes were identified to support QLCSs with hail, from high shear, low cape (HSLC) to low shear, high …

Surveys And Modeling: Using An Existing Survey To Describe And Compare Populations To Better Inform On Groundwater Model Inputs, M. Austin Wise

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The Mississippi River Valley “Alluvial Aquifer” is among the most agriculturally significant aquifers in the United States. However, parts of the aquifer are exceeding sustainable yield as development of the water source continues. Survey research in other aquifers, such as the High Plains (Ogallala) Aquifer, has helped to understand the perceptions and attitudes of irrigators withdrawing from their aquifers. This led to numerous questions: What are the attitudes of irrigators in the Alluvial Aquifer region? How do they compare to irrigators in other regions of the country? Can their intentions be used to generate more accurate inputs when modeling adoption …

Exploring The Application Of Repeated Microgravity Surveys To Monitor Groundwater Level Variations In Nebraska, Kaitlin M. Steinauer

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Groundwater is an important resource in the state of Nebraska for supporting industries and ecosystems. Monitoring this vast resource ensures its continued availability for generations to come. However, monitoring utilizes well data, and if a well is not present in a desired location, geophysical methods can be explored. This project tests the capability of repeated gravity surveys over Nebraska’s aquifers to monitor groundwater levels throughout 2024.

Two study areas were selected in Eastern Nebraska. The first is in Oakland, Nebraska, over a confined aquifer system. The second is in Plymouth, Nebraska, and exhibits unconfined conditions. Four sites were chosen to …

Aptamer Selection And Development Of Electrochemical Aptamer-Based Sensors For Neuropeptide Y, Evelyn Adela Carreto Guevara

Department of Chemistry: Dissertations, Theses, and Student Research

In this thesis, we report the results of four aptamers obtained from an aptamer selection process called the systematic evolution of ligands by exponential enrichment (SELEX) with affinity to Neuropeptide Y (NPY). NPY is a highly abundant peptide transmitter with widespread distribution throughout the body which affects various physiological functions. These functions include energy homeostasis, appetite regulation, stress response, and anxiety regulation. Dynamic monitoring of NPY levels is crucial for better understanding behaviors in individuals with neurological disorders associated with NPY. Aptamers are synthetic oligonucleotides obtained through SELEX which have a binding affinity to a target of interest when in …

Not All Political Ties Are The Same: Firms' Ties To The Government And Pollution, Wen Helena Li, Ilya R. P. Cuypers, Gokhan Ertug, Hari Bapuji, Wei Liu

Research Collection Lee Kong Chian School Of Business

Complementing research on the implications of political ties for firms’ strategic decisions and financial performance, recent studies are increasingly focusing on the environmental consequences of firms’ political connections. We contribute to this stream of work by integrating insights from the literature on political ties and the multifaceted nature of governments to explore how the level of government influences the pollution implications of firms’ political ties. Specifically, we theorize and demonstrate that, in China, firms' achieved political ties with high levels of the government reduce pollution, while such ties with low levels of the government increase it. Furthermore, we examine how …

Strain Induced Quantum Emitters In Monolayer Wse₂: Fabrication And Characterization Of Dimple Dot Devices, Garrett Maxwell Kitterman

Graduate Theses and Dissertations

Strain induced defects in monolayer tungsten diselenide (WSe₂) give rise to localized exciton funnels, offering a promising approach for the development of tunable quantum emitters. The quantum devices fabricated for this thesis used a modified dimple dot geometry, in which nano indentation creates a strain profile on the monolayer WSe₂. This allows for the funneling of excitons to a confined region. These strain induced funnels enable localized emission from single excitons in WSe₂. Device fabrication was carried out through mechanical exfoliation, dry transfer, and electron beam lithography of Cr/Au gates on a SiO₂ substrate. These devices were then characterized using …

Rethinking Iterative Proportional Fitting: Scalable And Hybrid Approaches To Joint Distribution Fitting, William Ofosu Agyapong

Open Access Theses & Dissertations

The Iterative Proportional Fitting (IPF) algorithm is widely used in contingency table estimation, survey weighting, and synthetic population generation due to its simplicity and strong theoretical foundation for matching observed marginal distributions. However, in high-dimensional settings, IPF faces substantial computational and memory demands, as well as statistical instability caused by sparse contingency tables. Moreover, IPF is less useful in modern population synthesis tasks that require both scalability and realism because, despite its superiority in matching known marginal distributions, it cannot produce realistic out-of-sample data points. To address these limitations, we first propose a blockwise IPF framework, in which the feature …

Decoding Anisotropic Porous Medium: A Synergy Of Lattice Boltzmann Modelling And Operator Learning To Predict Permeability As A Function Of Orientation, Soumya Shouvik Bhattacharjee

Open Access Theses & Dissertations

Understanding the directional properties of porous media is essential for accurately predicting flow behavior, reactive transport, and fluid-solid interactions in systems ranging from geothermal reservoirs to energy storage devices and biological tissues. Directional variations in permeability - reflecting a medium's response to flow at different angular orientations - are particularly important for complex, inherently anisotropic geometries. In this study, we employ a Lattice Boltzmann (LBM) model to calculate directional permeabilities from porous media images subjected to varying flow inlet angles. Three classes of porous media were investigated: (1) synthetic media with circular grains, serving as isotropic baselines; (2) synthetic media …

Analyzing The Impact Of Approximate Arithmetic On Deep Neural Network Predictions, Johnatan Garcia

Open Access Theses & Dissertations

In recent times, we have seen the use of artificial intelligence in our daily lives. It helps us solve complicated problems. Some of these problems can be large and complex, requiring large models. As models grow in complexity, they require more computations and energy to be trained and tested. The execution of these models relies on floating-point arithmetic, which imposes constraints due to its finite precision. Due to these limitations, many of these computations are not exact. When this happens, computers are forced to round or approximate. We can use several number formats to circumvent this issue. For example, in …

Terrane Accretion In The Trollheimen And Dovrefjell Regions Of The Scandinavian Caledonides, Norway, Stephanie Georgevich

Open Access Theses & Dissertations

Following closure of the Iapetus Ocean, the paleocontinents of Laurentia and Baltica collided to form the Caledonian Orogeny. During this closure and subsequent collision, island arc terranes and microcontinents were accreted and subducted underneath the Norwegian continental margin. These terranes are preserved in central Norway, specifically in the Dovrefjell and Trollheimen mountain ranges. The order in which these terranes accreted to the continent and when this occurred is not well understood. To determine this stacking order, I will be using P-T path modeling, U-Pb zircon dating, and structural position. Knowing the degree, progression, and geologic age of metamorphism, and tectonostratigraphic …

A Multi-Modal Method For Synthetic Data Generation In Social Network Analysis, Hortencia Josefina Hernandez

Open Access Theses & Dissertations

Social network analysis (SNA) research is often rife with data collection pitfalls, frequently leading to incomplete and missing data. With the growing use of SNA-based research, researchers must address the challenge of missing data and synthetic data generation in these settings. Missing data occurs due to longitudinal non-response or lack of response to sensitive or difficult-to-answer questions. Synthetic data generation in SNA settings addresses the lack of representation that is often present in large-scale SNA studies. This dissertation investigates synthetic data generation methods to address these challenges and develops a novel algorithm that leverages information from multi-modal data, e.g., databases …

High-Frequency Seismic Noise In Desert Environments, Alexis Hernandez

Open Access Theses & Dissertations

This study investigates the generation and modulation of ambient seismic noise in arid environments, with a focus on aeolian processes such as saltation, wind shear, and precipitation events. Using a dense array of three-component seismic nodes co-located with meteorological sensors and a novel particle transport instrument (SANTRI), high-frequency seismic signatures were examined within the Jornada Experimental Range in southern New Mexico. Time-frequency analysis reveals that wind-driven saltation events produce measurable seismic energy enhancements, particularly within the 100-300 Hz band, with clear spectral distinctions between wind-only forcing and particle-laden transport. Additionally, rainfall events were identified by elevated seismic amplitudes in the …