Physical Sciences and Mathematics Commons^™

Arbitrary High Order Finite Difference Methods With Applications To Wave Propagation Modeled By Maxwell's Equations, Min Chen

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation investigates two different mathematical models based on the time-domain Maxwell's equations: the Drude model for metamaterials and an equivalent Berenger's perfectly matched layer (PML) model. We develop both an explicit high order finite difference scheme and a compact implicit scheme to solve both models. We develop a systematic technique to prove stability and error estimate for both schemes. Extensive numerical results supporting our analysis are presented. To our best knowledge, our convergence theory and stability results are novel and provide the first error estimate for the high-order finite difference methods for Maxwell's equations.

On Improving Performance Of The Binary Logistic Regression Classifier, Michael Chang

UNLV Theses, Dissertations, Professional Papers, and Capstones

Logistic Regression, being both a predictive and an explanatory method, is one of the most commonly used statistical and machine learning method in almost all disciplines. There are many situations, however, when the accuracies of the fitted model are low for predicting either the success event or the failure event. Several statistical and machine learning approaches exist in the literature to handle these situations. This thesis presents several new approaches to improve the performance of the fitted model, and the proposed methods have been applied to real datasets.

Transformations of predictors is a common approach in fitting multiple linear and …

Evaluating Parents Sociodemographic Factors And Childhood Vaccine Decisions, Mehret Girmay

UNLV Theses, Dissertations, Professional Papers, and Capstones

Vaccination is considered one of the most successful public health achievements of the 20th century. However, with increasing vaccine skepticism emerging over the past decades, there is a threat to the ongoing sustainment of vaccine coverage within all US communities. This study evaluated and compared parents’ sociodemographic factors associated with childhood vaccine decisions. This study is a secondary analysis of 893 parents/guardians, age 18-55 years with child(ren) < 7 years living in the U.S.

Predictive analysis was conducted using multinomial logistic regression modeling was used to examine vaccine decisions (accept, hesitant, and refuse) in relation to parents’ sociodemographic factors. Overall, (66.6%) of parents accepted recommended vaccines, while …

Moisture Dynamics Of A Near-Surface Desert Soil, Yuan Luo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Desert soils cover about one third of the Earth’s land surface. Despite their large extent, however, our understanding of desert soil hydraulic processes and properties is still rather limited. In particularly with respect to the near-surface (top centimeters) of the soil profile, which play a critical role for infiltration, redistribution and evapotranspiration of rainwater, the limiting resource for life in desert environments, but also hosts most of the biologic activity and controls runoff, erosion as well as the emission of dust (Nannipieri et al.,2003; Bradford et al.,1987). Additionally, deserts are ideal locations for electricity generation with solar energy using large-scale …

Examination Of Maskelynite Through Static Recompression And Dynamic Compression, Justin James Reppart

UNLV Theses, Dissertations, Professional Papers, and Capstones

This is an experimental study that aims to clarify the possible formation mechanisms of maskelynite. Maskelynite is a diaplectic glass, that forms during shock compression of feldspar far below the melting point, and without fusion. Maskelynite also paramorphises precursor feldspar grains. Maskelynite is an important probe of shock-pressures at terrestrial impact sites and in many meteorites. Two mechanisms of formation of maskelynite are examined here: 1) maskelynite is result of a pressure-induced amorphization of feldspar compressed beyond its mechanical stability where the formation of thermodynamically stable phases is kinetically inhibited [1, 2]. 2) Feldspar transforms upon dynamic compression into a …

Carbon Management And Volatile Fatty Acid Production In Primary Clarifiers At A Wastewater Treatment Plant, Brittany Nicole Radke

UNLV Theses, Dissertations, Professional Papers, and Capstones

An increasing number of treatment plants are required to remove nutrients from domestic wastewater to lessen the impact of nutrient loading to water bodies. Enhanced Biological Phosphorus Removal (EBPR) is one of the processes commonly used to remove phosphorus from domestic wastewater. The presence of an adequate quantity of volatile fatty acids (VFA) in the wastewater influent to EBPR is important for process efficiency and stability. The objective of this research was to investigate the production of VFAs through fermentation of sludge in primary clarifiers as it related to improving nutrient removal, primarily targeting phosphorus.

The research tested, in full-scale, …

The Timing Of Dynamical Interactions Between Planets In Exoplanetary Systems, David Robert Rice

UNLV Theses, Dissertations, Professional Papers, and Capstones

During the late stage of planet formation, a system is often dynamically packed with protoplanets. These bodies collide together and are ejected from the system to form the final planets. The duration of stability before these dynamical interactions occur is dependent on the initial separation of the bodies in a system. Previous works have shown that the time before a planet-planet close encounter is exponential with the initial planet spacing measured in units of mutual Hill radius. We investigate the limitations of these previous studies. We find that systems that are initially similar can have larger differences in stability times …

Application Of Data-Driven And Process-Based Modeling Approaches For Water Quality Simulation In Lakes And Freshwater Reservoirs, Ali Saber Sichani

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lakes and freshwater reservoirs often serve as the primary drinking and irrigation water sources for surrounding communities. They provide recreational and tourism opportunities, thereby promoting the prosperity of neighboring communities. Reliable estimates of water quality in lakes and reservoirs can improve management practices to protect water resources.

Seasonal water temperature and solar shortwave radiation variations, and their subsequent interactions with water column aquatic life, combined with seasonal variations of mixing intensity throughout the water column, result in variations of water quality constituents with depth during the annual cycle. The complexity of these variations entails the use of advanced water quality …

Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

The intrinsic link between long-range order, coordination geometry, and the electronic properties of a system must be understood in order to tailor function-specific materials. Although material properties are typically tailored using chemical dopants, such methods can cause irreversible changes to the structure, limiting the range of functionality. The application of high pressure may provide an alternative “clean” method to tune the electronic properties of semiconducting materials by tailoring their defect density and structure.

We have explored a number of optoelectronic relevant materials with promising characteristics, specifically Sn-(O,N) compounds which have been predicted to undergo pressure-mediated opening of their optical band …

Mojave Desert Ecosystem Recovery: Potency Of Biotic And Abiotic Restoration Methods In Low Elevation Plant Communities, Mary Amanda Balogh

UNLV Theses, Dissertations, Professional Papers, and Capstones

The historic and current state of land in the Mojave Desert, including land managed by the National Park Service with fundamental goals of natural resource conservation and preservation, been severely degraded by a variety of anthropogenic disturbances. Due to increasingly sporadic and unpredictable precipitation patterns, land managers struggle to implement restoration projects with high success rates and are resource-limited for post-treatment monitoring. In this study, I examined success rates of biotic (outplanting, seeding) and abiotic (soil manipulation, vertical mulch) restoration treatments on various disturbance types in the creosote-bursage (Larrea tridentata-Ambrosia dumosa), blackbrush (Coleogyne ramosissima), and Joshua tree woodland (Yucca brevifolia) …

On Muddy Banks: An Ecoethnography Of A River Island Community, Nicholas Baxter

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this study, I examine the relationship between a river and a community. Specifically, I analyze the processes and patterns that organize the nature-society relationship and define the river town of Sabula, IA. To guide my historical and ethnographic analysis, I utilize a co constructionist posture (Rice 2013), which sees culture, community, economy, and physicality as much a product of bio-physical forces as social forces. My aim is to understand how Sabula is conjointly constructed and reveal the nuanced interconnections between human communities and nature through which social and environmental problems play out. My analysis clarifies patterns in residents’ identity …

Landscape Scale: Inter- And Intraspecific Variation In Plant Interactions Along A Stress Gradient In The Sheep Range Of Nevada, Jordan Dowell

UNLV Theses, Dissertations, Professional Papers, and Capstones

Impending threats to shrubland ecosystems, posed by climate change, necessitate niche modeling efforts to project vegetation range shifts. However, efforts often remain unguided by individual-scale interspecific plant interactions. The stress gradient hypothesis posits that facilitation should increase in areas of high abiotic stress, only if the individuals are able to ameliorate the surrounding area via functional traits. The Sheep Range of Nevada was used to assess the role of functional traits as predictors of plant association. Larrea tridentata, Coleogyne ramosissima, and Artemisia nova were selected as shrubs with variable life history strategies and ranges in order to identify general patterns …

Mojave Desert Plant Community Long-Term Response To Disturbance, Dominic M. Gentilcore

UNLV Theses, Dissertations, Professional Papers, and Capstones

All vegetation communities have been shaped by disturbances. This dissertation consists of three separate chapters: Blackbrush (Coleogyne ramosissima) natural regeneration in the Great Basin-Mojave Desert Transition Zone on two fires, Long-term Response to Fire in Eastern Mojave Desert semi-arid shrubland communities, and an Annotated Checklist of Gold Butte National Monument in the Mojave-Colorado Plateau Transition Zone. The section on blackbrush natural regeneration was a long-term dataset from two fires in Basin and Range National Monument that burned in 2008 with monitoring events in 2009, 2010, 2011, 2018 and 2019. The monitoring documented some of the strongest post-fire regeneration for the …

Utility Of Bench Scale Sand Tank Experiments At Assessing Permeable Reactive Barrier Design, Brandon Meier

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of this work was to evaluate the utility of bench scale sand tank experiments at assessing permeable reactive barrier (PRB) design. Our criteria for meeting this goal was that differences between PRB designs could be identified solely by measuring concentration in outflow from the sand tank models. For our PRB designs (funnel-and-gate, staggered wells, and parallel bars), numerical simulations clearly showed that PRB design had a quantifiable effect on outflow concentration, provided that the solute reacted with the PRB materials. Conversely, use of a conservative (non-reactive) solute did not allow us to discern between PRB design alternatives. Employing …

On The Human Factors Impact Of Polyglot Programming On Programmer Productivity, Phillip Merlin Uesbeck

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyglot programming is a common practice in modern software development. This practice is often considered useful to create software by allowing developers to use whichever language they consider most well suited for the different parts of their software. Despite this ubiquity of polyglot programming there is no empirical research into how this practice affects software developers and their productivity. In this dissertation, after reviewing the state of the art in programming language and linguistic research pertaining to the topic, this matter is investigated by way of two empirical studies with 109 and 171 participants solving programming tasks. Based on the …

Zirconium Tetrachloride, Fundamental Chemistry And Nuclear Fuel Cycle, Rosendo Borjas Nevarez

UNLV Theses, Dissertations, Professional Papers, and Capstones

Zirconium alloys are used in the United States as cladding materials in nuclear reactors. The purification of Zr is of relevance due to the large amount of spent nuclear fuel produced every year (2,000 metric tons per year and rising), of which 25% corresponds to radioactive zirconium cladding. Through the recovery and reuse of Zr, estimated savings of $40 million per year are estimated due to the high cost of hafnium-free nuclear grade zirconium, and also due to the minimization of nuclear waste disposal requirements.

Several chemical approaches have been proposed for the recovery and purification of Zr. Historically, a …

Characterizing Compact Game Trees, Andrew Dubose

UNLV Theses, Dissertations, Professional Papers, and Capstones

It is well-known that the body of a game tree of height less than or equal to ω is compact

if and only if the tree is finitely branching. In this thesis, we develop necessary and sufficient

conditions for the body of any game tree to be compact.

The Retrospective Analysis Of Radionuclides In Banded Coral From The Bikini Atoll, Athena Marie Gallardo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nuclear weapons testing conducted within the Bikini Atoll in the Marshall Islands resulted in local fallout contamination, including long lived isotopes of plutonium (Pu) and uranium (U), within the surrounding environment. The Bikini lagoon provides a continuous source of Pu (239+240Pu) and U (236U) to the Pacific Basin. The rate at which these isotopes are flushed from the lagoon to the ocean is balanced by inputs from remobilization of lagoon sediments. This research will provide a basis for predicting future change in the solubility and export potential of Pu and U in lagoon sediments. This is important to better understand …

Factors Associated With Eosinophilic Esophagitis In Nevada, Julia Lorraine Anderson

UNLV Theses, Dissertations, Professional Papers, and Capstones

Eosinophilic esophagitis (EoE) is a rare immune-mediated illness with symptoms that range from difficulty swallowing to food impaction of the esophagus. Most published studies have been documented among patients residing in cool regions with significant annual rainfall. No published studies to our knowledge have been performed examining the healthcare utilization trends of EoE in Nevada. Utilizing two unique databases, the factors associated with EoE healthcare utilization patterns in Nevada were examined. All analyses were performed in R version 3.5.1. This study included a demographic and regional analysis identifying risk factors associated with having an EoE healthcare visit in Nevada. Several …

Processj: The Jvmcsp Code Generator, Oswaldo Benjamin Cisneros Merino

UNLV Theses, Dissertations, Professional Papers, and Capstones

We as a society have achieved greatness because we work together. There is power in numbers. However, when it comes to programming we have not been able to achieve the same level of symbiosis. This is because concurrent programming has been stigmatized as an advance and ab- stract subject allegedly harder than sequential programming. Additionally, traditional approaches to solving concurrent problems using sequential programming become unnecessarily difficult be- cause most of what newcomers are taught when it comes to concurrent programming (e.g., message passing and threads), while being technically correct, is completely irrelevant to the problems at hand. Rather than …

Application Of Semi-Hydrophobic Layers To Decrease Bare Soil Evaporation, Jesse Lee Barnes

UNLV Theses, Dissertations, Professional Papers, and Capstones

Evaporative water loss from bare agricultural soils is a primary area of water conservation research. Mulching is the commonly utilized method to decrease evaporative water loss. The most commonly utilized mulch is nonbiodegradable polyethylene sheeting because it tends to decrease evaporative water loss and increase crop yields more than environmentally friendly mulches. This study aimed to test the utility of sand coated with polymerized soybean oil (i.e., hydrophobic sand) as a treatment to reduce bare soil evaporation and an alternative to current practices. Evaporation rates were measured in laboratory soil columns containing both treated and untreated soils. Treatment parameters were …

Applied Symmetry For Crystal Structure Prediction, Scott William Fredericks

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis presents an original open-source Python package called PyXtal (pronounced "pi-crystal") that generates random symmetric crystal structures for use in crystal structure prediction (CSP). The primary advantage of PyXtal over existing structure generation tools is its unique symmetrization method. For molecular structures, PyXtal uses an original algorithm to determine the compatibility of molecular point group symmetry with Wyckoff site symmetry. This allows the molecules in generated structures to occupy special Wyckoff positions without breaking the structure's symmetry. This is a new feature which increases the space of search-able structures and in turn improves CSP performance.

It is shown that …

Coarse-Grained, Fine-Grained, And Lock-Free Concurrency Approaches For Self-Balancing B-Tree, Edward R. Jorgensen Ii

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation examines the concurrency approaches for a standard, unmodified B-Tree which is one of the more complex data structures. This includes the coarse grained, fine-grained locking, and the lock-free approaches. The basic industry standard coarse-grained approach is used as a base-line for comparison to the more advanced fine-grained and lock-free approaches. The fine-grained approach is explored and algorithms are presented for the fine-grained B-Tree insertion and deletion. The lock-free approach is addressed and an algorithm for a lock-free B- Tree insertion is provided. The issues associated with a lock-free deletion are discussed. Comparison trade-offs are presented and discussed. As …

An Application Of Conformal Mapping To The Boundary Element Method For Unconfined Steady Seepage With A Phreatic Surface, Jorge Eduardo Reyes

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this thesis, numerical results using the Boundary Element Method (BEM) for groundwater flow in a domain with a boundary that contains numerous singularities with a phreatic surface are developed. The flow in the domain is modeled using Darcy’s law for a homogeneous isotropic porous medium. The boundary conditions are a combination of Dirichlet and Neumann with the phreatic surface having both boundary conditions. Exact solutions by Conformal Mapping for simplified domains with the same singularity as the original domain allow for modifications to the BEM resulting in an improvement to the numerical solution.

An iterative process is used to …

Static Malware Detection Using Deep Neural Networks On Portable Executables, Piyush Aniruddha Puranik

UNLV Theses, Dissertations, Professional Papers, and Capstones

There are two main components of malware analysis. One is static malware analysis and the other is dynamic malware analysis. Static malware analysis involves examining the basic structure of the malware executable without executing it, while dynamic malware analysis relies on examining malware behavior after executing it in a controlled environment. Static malware analysis is typically done by modern anti-malware software by using signature-based analysis or heuristic-based analysis.

This thesis proposes the use of deep neural networks to learn features from a malware’s portable executable (PE) to minimize the occurrences of false positives when recognizing new malware. We use the …

Managing Iot Data On Hyperledger Blockchain, Akhil David

UNLV Theses, Dissertations, Professional Papers, and Capstones

Blockchain is a rapidly evolving technology known for its security, immutability and decentralized nature. At its heart, it’s used for storing various kinds of data like transactions. But it is not limited to just the transactions or the cryptocurrency. It can also be used to store many other things like assets, IoT data or even multimedia data like songs, pictures, and videos.

The number of IoT devices being connected to the internet is increasing day by day. In fact, Garter (Analyst Firm) predicts there will be 20.4 Billion IoT devices by the end of 2020 [IOTb]. With the increase in …

Improving Ocr Post Processing With Machine Learning Tools, Jorge Ramon Fonseca Cacho

UNLV Theses, Dissertations, Professional Papers, and Capstones

Optical Character Recognition (OCR) Post Processing involves data cleaning steps for documents that were digitized, such as a book or a newspaper article. One step in this process is the identification and correction of spelling and grammar errors generated due to the flaws in the OCR system. This work is a report on our efforts to enhance the post processing for large repositories of documents.

The main contributions of this work are:

• Development of tools and methodologies to build both OCR and ground truth text correspondence for training and testing of proposed techniques in our experiments. In particular, we …

Performance Comparison Of Message Queue Methods, Sanika Raje

UNLV Theses, Dissertations, Professional Papers, and Capstones

Message queues are queues of messages that facilitate communication between applications. A queue is a line of messages or events waiting to be handled in a sequential manner. A message queue is a queue of messages sent between applications. It includes a sequence of work objects that are waiting to be processed. For a distributed system to work, it needs to pass information between various machines. No single machine is responsible for the entire system, but all information is interrelated. Hence a major concern of distributed systems is this transfer of data. Which also proves to be one of the …

Petrogenesis Of Unusual Occurrence Of Amphibole Asbestos In Mohave County, Arizona And Clark County, Nevada, Tomoyo Austin

UNLV Theses, Dissertations, Professional Papers, and Capstones

The term “asbestos” applies to six types of fibrous amphiboles or chrysotile with specific morphologies that are commercially mined and processed. Inhaling asbestos fibers is known to cause many negative health effects, including mesothelioma, several different cancers, various respiratory diseases and non-respiratory diseases, and fatalities. The recent years, several cases of non-occupational exposure to asbestos fibers raised an awareness of environmental exposure to naturally occurring asbestos (NOA) which refers to asbestiform minerals that fall out of the regulatory definition of asbestos.

There are two sources of NOA in the area, Wilson Ridge pluton, AZ, and Boulder City pluton, NV which …

Permutation Flow Shop Via Simulated Annealing And Neh, Pooja Bhatt

UNLV Theses, Dissertations, Professional Papers, and Capstones

Permutation Flow Shop Scheduling refers to the process of allocating operations of jobs to machines such that an operation starts to process on machine j only after the processing completes in j-1machine. At a time a machine can process only one operation and similarly a job can have only one operation processed at a time. Finding a schedule that minimizes the overall completion times for Permutation Flow Shop problems is NP-Hard if the number of machines is greater than 2. Sowe concentrates on approaches with approximate solutions that are good enough for the problems. Heuristics is one way to find …