Digital Commons Network^™

Design And Construction Of A Longitudinally Polarized Solid Nuclear Target For Clas12, Victoria Lagerquist

Physics Theses & Dissertations

A new polarized nuclear target has been developed, constructed, and deployed at Jefferson Laboratory in Newport News, VA for use with the upgraded 12 GeV CEBAF (Continuous Electron Beam Accelerator Facility) accelerator and the Hall B CLAS12 (12 GeV CEBAF Large Acceptance Spectrometer) detector array. This ‘APOLLO’ (Ammonia POLarized LOngitudinally) target is a longitudinally polarized, solid ammonia, nuclear target which employs DNP (Dynamic Nuclear Polarization) to induce a net polarization in samples of protons (NH3) and deuterons (ND3) cooled to 1K via helium evaporation, held in a 5T polarizing field supplied by the CLAS12 spectrometer, and irradiated with 140 GHz …

Measurements Of Magnetic Field Penetration Of Materials For Superconducting Radiofrequency Cavities, Iresha Harshani Senevirathne

Physics Theses & Dissertations

Superconducting Radio Frequency (SRF) cavities used in particle accelerators are typically formed from or coated with superconducting materials. Currently high purity niobium is the material of choice for SRF cavities which have been optimized to operate near their theoretical field limits. This brings about the need for significant R&D efforts to develop next generation superconducting materials which could outperform Nb and keep up with the demands of new accelerator facilities. To achieve high quality factors and accelerating gradients, the cavity material should be able to remain in the superconducting Meissner state under high RF magnetic field without penetration of quantized …

Nb3Sn Coating Of Twin Axis Cavity And Other Complex Srf Cavity Structures, Jayendrika Kumari Tiskumara

Physics Theses & Dissertations

In the field of Accelerator Science, for the low cost and increased quality factor, thin films coated niobium cavities are used in the modern SRF research. Within the potential substances, Nb₃Sn has shown higher critical temperature than niobium. Here the tin vapor diffusion method is used as the preferred technique to coat niobium cavities. So far, only elliptical cavities have been coated with Nb₃Sn and this technique has not yet been applied to cavities with complex geometries, which are also helpful in the accelerator science field. The Half-wave resonator could provide us data across frequencies of …

The Safe And Effective Clinical Deployment Of Artificial Intelligence To Ols, Kelly Nealon

Dissertations and Theses (Open Access)

18 million new cancer cases are diagnosed each year. Roughly half of these patients will be treated with radiation therapy, a complex technique that requires an interdisciplinary team of clinical staff and expensive equipment to be delivered safely. Cancer centers in Low- and Middle-Income Countries (LMIC) have an especially difficult time meeting the demands of radiation therapy as the complexity of treatment techniques increase, with only 37% of patients in these regions having access to the care they need. Artificial Intelligence (AI) based tools are being developed to simplify the treatment planning and quality assurance processes to increase the number …

Treatment Planning Automation For Rectal Cancer Radiotherapy, Kai Huang

Dissertations and Theses (Open Access)

Background

Rectal cancer is a common type of cancer. There is an acute health disparity across the globe where a significant population of the world lack adequate access to radiotherapy treatments which is a part of the standard of care for rectal cancers. Safe radiotherapy treatments require specialized planning expertise and are time-consuming and labor-intensive to produce.

Purpose:

To alleviate the health disparity and promote the safe and quality use of radiotherapy in treating rectal cancers, the entire treatment planning process needs to be automated. The purpose of this project is to develop automated solutions for the treatment planning process …

Development Of Multi-Configuration Methods On Density Functional Theory Orbitals And Application On The Study Of Dimers, Jose Gustavo Bravo Flores

Open Access Theses & Dissertations

The configuration interaction (CI) methods is an exact method to solve the non relativistic Schrodinger equation, describing the wave function as a linear combination of Slater determinants. Because the computation time grows factorially as the number of electrons, CI is mostly used for relatively small systems. Density functional theory (DFT) rose as one of the most used methods for computational quantum chemistry in the last 30 years. DFT can describe a system's properties with the electron density, which only depends of of three coordinates. Due to its low computational costs it allows one to study bigger systems than CI, however …

Understanding And Tuning Magnetism In Van Der Waals Magnetic Compounds, Rabindra Basnet

Graduate Theses and Dissertations

The recently discovered two-dimensional (2D) magnetism has attracted intensive attention due to possible magnetic phenomenon arising from 2D magnetism and their promising potential for spintronics applications. The advances in 2D magnetism have motivated the study of layered magnetic materials, and further enhanced our ability to tune their magnetic properties. Among various layered magnets, tunable magnetism has been widely investigated in metal thiophosphates MPX3. It is a class of magnetic van der Waals (vdW) materials with antiferromagnetic ordering persisting down to atomically thin limit. Their magnetism originates from the localized moments due to 3d electrons in transition metal ions. So, their …

Simulating Radial Ring Structure With An Ambipolar Elsasser (Am) Bump In Non-Ideal Magnetohydrodynamics Of Protoplanetary Disks, Aleksey S. Mohov

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rings are one of the most ubiquitous substructures observed in protoplanetary disks. They are known to be a robust site for planetesimal formation; thus we look for mechanisms that can originate stable rings. From chemical modelling of snow lines, we expect a bump in the Ambipolar Diffusion (AD) Elssaser number (Am) in the radial direction. We use the Athena++ code to model the non-ideal Magentohydrodynamics (MHD) behavior of an Am bump. We explore a parameter space of Gaussian bumps with Am = 5, 1, 0.5 peak strength and σ = 0.25, 1, 5. The Gaussian profile is inserted into the …

Studies Of The Ionosphere-Thermosphere Responses To Multi-Scale Energy Deposition Processes, Haonan Wu

All Dissertations

The Ionosphere-Thermosphere (I-T) system is greatly affected by the magnetospheric energy deposition from above and subjected to forcing from the lower atmosphere simultaneously. A central problem in studying the coupled I-T system is to analyze the multi-scale processes naturally embedded in both ways. Magnetospheric energy input such as auroral precipitation and electric field demonstrates multi-scale structures during magnetic storms, resulting in multi-scale I-T responses when deposited into the I-T system. To better quantify the multi-scale aurora and electric field, we developed a new data assimilation model based on a multi-resolution Gaussian process model to synthesize empirical models and observational data …

Designing Noncentrosymmetric Multifunctional Materials, Ebube Oyeka

All Dissertations

Noncentrosymmetric (NCS) materials with crystal lattices lacking spatial inversion symmetry display a wide range of exciting functionalities. This dissertation covers two classes of functional NCS materials: magnetic skyrmion-host compounds and multifunctional materials. Magnetic skyrmion and multifunctional materials combining optical and magnetic responses are providing avenues for developing and optimizing the performance of electronic devices that can have uses in memory storage, laser technology, medicine, sensors, etc. The formation of skyrmions is driven by asymmetric Dzyaloshinskii–Moriya (DM) interaction facilitated by broken spatial inversion symmetry and large spin-orbit coupling (SOC), while multiple functionalities arise when spin carriers and optical chromophores are optimally …

The Search For Heavily Obscured Active Galactic Nuclei In The Local Universe, Ross Silver

All Dissertations

Active galactic nuclei (AGN) are supermassive black holes (SMBHs) in the center of galaxies that accrete surrounding gas and emit across the entire electromagnetic spectrum. They are the most energetic persistent emitters in the Universe, capable of outshining their host galaxies despite their emission originating from a region smaller than our Solar System. AGN were some of the first sources discovered that helped teach us that there were galaxies outside of our own, and they proved the existence of black holes. Moreover, AGN can give us valuable insights into other branches of astrophysics. For example, they can be used to …

Machine Learning-Based Data And Model Driven Bayesian Uncertanity Quantification Of Inverse Problems For Suspended Non-Structural System, Zhiyuan Qin

All Dissertations

Inverse problems involve extracting the internal structure of a physical system from noisy measurement data. In many fields, the Bayesian inference is used to address the ill-conditioned nature of the inverse problem by incorporating prior information through an initial distribution. In the nonparametric Bayesian framework, surrogate models such as Gaussian Processes or Deep Neural Networks are used as flexible and effective probabilistic modeling tools to overcome the high-dimensional curse and reduce computational costs. In practical systems and computer models, uncertainties can be addressed through parameter calibration, sensitivity analysis, and uncertainty quantification, leading to improved reliability and robustness of decision and …

Applying Instrumental Neutron Activation Analysis To Assess Air Pollution With Spanish Moss As A Bioindicator In The Low Country Of The Savannah River Basin, Christina Jiang

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Savanah River Basin is an area of 9,850 square miles that stretches from the border between South Carolina and Georgia, which empties into the Atlantic Ocean near Savannah, Ga. This area is home to surrounding cities, industrial sites, and the Savanah River Site. It is well documented that traffic, industrial operations, and agriculture contribute to worsening air pollution that needs to be monitored. While Tillandsia usneoides (Spanish moss) has been used in previous studies that prove it to be an effective biomonitor for air pollution and an accumulator of heavy metals, there have been no biomonitoring studies in the …

Stoichiometric Determination Of Hydride Materials At Extreme Conditions, Gregory Alexander Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogen was predicted to be a high-temperature superconductor at near-megabar conditions in 1968,[1] but only recently was been experimentally observed.[2] This is due to the extraneous metrological constraint of requiring 5 megabars of pressure to stabilize. A more practical approach for synthesis of high-temperature superconductors has been pro-posed through the use of hydride compounds. Recently, a surge of rare earth hydrides have achieved critical superconducting transition temperatures (T_C ) close to room temperature.[3, 4, 5, 6] However, due to limitations of the necessary instrumentation to achieve megabar pressures, many techniques traditionally used to measure stoichiometry are unavailable.Three works presented in …

Analysis And Application Of Finite Element And High-Order Finite Difference Methods For Maxwell’S Equations In Complex Media, Li Zhu

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Perfectly Matched Layer (PML) technique is an effective tool introduced by B´erenger [13] to reduce the unbounded wave propagation problem to a bounded domain problem. This dissertation focuses on two different PML models and their applications to wave propagation problems with Maxwell’s equation in complex media. We investigate these models using two popular numerical methods: the Finite Difference Method (FDM) in Chapters 2 and 3, and the Finite Element Method (FEM) in Chapters 4 and 5.In Chapter 2, we focus on analyzing the stability of a PML developed by B’ecache et al. [10] for simulating wave propagation in the …

Methods For Preparing And Characterizing Granular Materials For Electron Yield Measurements, Tom Keaton

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

This work presents a systematic study on sample preparation methods and accuracy of electron yield (EY) measurements of highly insulating, granular materials. EY measurements of highly insulating materials, especially those with high EY, are challenging due to the effects of sample charging even for very low fluence electron probe beams. EY measurements of particulates are complicated by: (i) roughness effects from particulate size, shape, coverage, and compactness; (ii) particle adhesion; (iii) substrate contributions; and (iv) electrostatic repulsion and potential barriers from charged particles and substrates. Numerous methods were explored to rigidly affix particles on conducting substrates at varying coverages for …

Assessment Of Bridge Pier Response To Fire, Vehicle Impact, And Air Blast, Chen Fang, Qusai Alomari, Daniel G. Linzell

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Highway bridges exposed to intentional or unintentional fire followed by combined vehicle impact and air blast are at risk of significant damage and, possibly, collapse. Limited studies examining the complex effects of these extreme demands on bridge support elements and parametrizing their response and damage are found in the open literature. Research that is presented is part of an ongoing numerical investigation examining round, multi-column, reinforced concrete (RC), bridge pier behavior subject to multi-hazard scenarios involving fire, vehicle impact, and air blast. Detailed nonlinear finite element analysis models of single columns and multi-column piers supported by a pile foundation system …

Response Of The Isothermal Mode Grüneisen Tensor Across Phase Boundaries, Jasmine K. Hinton

UNLV Theses, Dissertations, Professional Papers, and Capstones

The assumptions for the 1912 Grüneisen parameter are reviewed, particularly in the cases of anisotropy, high temperatures, and across phase boundaries. Two main case studies are shown: β-Sn, and Cd. The main techniques of this work involve resistively heated diamond anvil cells with both optical Raman spectroscopy and x-ray diffraction. It is found in Sn that the isothermal mode Grüneisen tensor along increasing isotherms diverges from the single-valued temperature aggregate at the onset of melt, and this is proposed to use as a method of exploring melt phase boundaries in other systems. This method is examined once again on another …

Exploration Of H2o Ice At Extreme Conditions, Zachary M. Grande

UNLV Theses, Dissertations, Professional Papers, and Capstones

Static compression experiments on water ice are needed for precise characterization and discovery of new ice phases near room temperature. Here I present my efforts and the developments that have been made to reduce detrimental effects found in high-pressure experiments in order to acquire precise measurements on ice approaching 3 Mbar. Several key observations are made, relating to the phase transition of ice-VII to X, an intermediate phase I have named ice-VIIt and evidence of a post ice X phase. Some of these experiments have been replicated using D2O ice as well, in order to gain insight into nuclear quantum …

Modeling, Simulation And Control Of Microrobots For The Microfactory., Zhong Yang

Electronic Theses and Dissertations

Future assembly technologies will involve higher levels of automation in order to satisfy increased microscale or nanoscale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to the microelectronics and MEMS industries, but less so in nanotechnology. With the boom of nanotechnology since the 1990s, newly designed products with new materials, coatings, and nanoparticles are gradually entering everyone’s lives, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than top-down robotic assembly. This is due to considerations of volume handling of large …

An Investigation On The Effect Of Conserved Hinge Histidine On Influenza Hemagglutinin(Ha2) Protein Conformation Using Md Simulations, Nada Tolba

Chemistry & Biochemistry Undergraduate Honors Theses

Hemagglutinin is a protein on the surface of Human Influenza Viruses.¹ It is composed of two glycopolypeptide domains, the HA1 and HA2 domains. Previous studies have found that across different strains of Influenza viruses, HIS435 residues remain conserved.⁴ In studies where mutations occurred in hinge-site histadine residues, the Influenza virus was inactive.⁴ These investigations indicated a significant role of HIS435 (hinge-site histadines) in virulence. Four systems were created using Molecular dynamics (MD) simulations. Each system was composed of an Isolated HA2 trimer solvated in a 150 mM NaCl rectangular water box at 310 K under isobaric and …

First-Principal Investigations Of The Electronic, Magnetic, And Thermoelectric Properties Of Crtirhal Quaternary Heusler Alloy, Shuruq Alsayegh

Graduate Theses and Dissertations

Density functional theory calculations are performed to investigate the electrical electronic, magnetic, and thermoelectric properties of CrTiRhAl quaternary Heusler alloy (QHA). The type-I atomic configuration is found to be the most stable structure of this alloy. The CrTiRhAl QHA exhibits a half-metallic ferromagnetic structure with a narrow band gap at one spin channel (semiconductor), and a metallic behavior at the other spin channel. This corresponds to a 100% spin-polarization, making it ideal for potential spintronic applications. Applying the semi-classical Boltzmann theory, the Seebeck coefficient, electrical conductivity, and electronic thermal conductivity of CrTiRhAl alloy were calculated. The predicted figure of merit …

Asymptotic Properties And Separation Rates For Navier-Stokes Flows, Patrick Michael Phelps

Graduate Theses and Dissertations

In this dissertation, we investigate asymptotic properties of local energy solutions to the Navier-Stokes equations and develop an application which controls the separation of non-unique solutions in this class. Specifically, we quantify the rate at which two, possibly unique solutions evolving from the same data may separate pointwise away from a singularity. This is motivated by recent results on non-uniqueness for forced and unforced Navier-Stokes and analytical and numerical evidence suggesting non-uniqueness in the Leray class. Our investigation begins with discretely self-similar solutions known to exist globally in time and to be regular outside a space-time paraboloid. We prove decay …

Exploring The Dependence Of Bulges In Spiral Galaxies On Their Environment, William Jackson Clark

Physics Theses & Dissertations

Recent research has shown a relationship between spiral galaxy satellite populations and the size of spiral bulges. The modern cosmological model of our universe (ΛCDM), does not predict this. Instead, ΛCMD predicts that only the total dynamical mass of a host galaxy should be correlated with satellite populations. We investigate this relationship in regimes other than satellites. In this study we compare the bulge to total mass ratios of spiral galaxies to the number of nearby galaxies within “n” Mpc. We use four papers from literature that calculate bulge to total mass ratios of 189 spiral galaxies using …

The Quantum Computational Utility Of Symmetry-Protected Topological Order: From Near-Term Advantages To Universal Measurement-Based Quantum Computing, Austin Kevin Daniel

Physics & Astronomy ETDs

Quantum computers offer new avenues to approach difficult problems by taking advantage of the strange and often nonintuitive phenomena present in quantum physics. Though many quantum algorithms are believed or known to outperform the best known classical algorithms, the fundamental mechanism granting them their power remains elusive. In measurement-based quantum computation (MBQC), two key resources have been show to enable universal and provably nonclassical quantum computations, respectively. These are symmetry-protected topological order (SPTO), a notion describing a class of quantum magnets with hidden long-range correlations in their entanglement structure, and quantum contextuality, the fact that a quantum measurement outcome inherently …

Another Shipment Of Six Short-Period Giant Planets From Tess, Joseph E. Rodriguez, Samuel N. Quinn, Andrew Vanderburg, George Zhou, Jason D. Eastman, Erica Thygesen, Bryson Cale, David R. Ciardi, Phillip A. Reed, Ryan J. Oelkers

Physics & Astronomy Faculty Publications

We present the discovery and characterization of six short-period, transiting giant planets from NASA’s Transiting Exoplanet Survey Satellite (TESS) -- TOI-1811 (TIC 376524552), TOI-2025 (TIC 394050135), TOI-2145 (TIC 88992642), TOI-2152 (TIC 395393265), TOI-2154 (TIC 428787891), and TOI-2497 (TIC 97568467). All six planets orbit bright host stars (8.9 <G < 11.8, 7.7 <K < 10.1). Using a combination of time-series photometric and spectroscopic follow-up observations from the TESS Follow-up Observing Program Working Group, we have determined that the planets are Jovian-sized (R_P = 0.99--1.45 R_J), have masses ranging from 0.92 to 5.26 M_J, and orbit F, G, and K stars (4766 ≤ T_eff ≤ 7360 K). We detect a significant orbital …

Analysis Of The Electrostatic Characteristics Of The Zika Virus Capsid Using Computational Methods, Cassandra Guadalupe Del Rio De Avila

Open Access Theses & Dissertations

Zika virus (ZIKV) is a flavivirus that is usually transmitted through the bite of infected mosquitoes. This virus can cause a variety of neurological disorders, the most common being Guillain-Barré syndrome in adults. Moreover, it is of great concern in pregnant women, since can cause deformities in the brain and other organs of newborns.Studying the structural characteristics of the virus during its mature and infectious phase can provide crucial information on the mechanisms by which it enters and replicates within host cells, as well as its evolution, transmission, and interaction with other living organisms. The symmetric pattern present in the …

Simulating Mass Extinctions In An Agent-Based Evolutionary Model, Emily Vastola, Will Hayes, Joe Milliano, Tyler Hanke, Ian Heye, Dawn M. King, Sonya Bahar

Undergraduate Research Symposium

In an agent-based model of evolutionary dynamics which has been shown to undergo a nonequilibrium phase transition from extinction to survival, we apply coalescent theory to investigate the responses of population lineages to simulated mass extinctions. In the model, organisms reproduce via assortative mating on a neutral fitness landscape; parameters including the mutability (distance offspring may be distributed away from their parents in the fitness landscape) and the death parameter (percentage of organisms randomly removed during each generation) control the phase transition. Lineage structure can be characterized using the time to most recent common ancestor (TMRCA). We examine how this …

Mathematical Modeling Of Egain Droplets Sliding Down An Inclined Plane, Shawn Koohy, Kathryn Massey, Luis Schneegans, Megan Vezzetti, Keith Hillaire, Souradip Chattopadhyay, Jessie Chen, Carmen Lee, Karen Daniels

Undergraduate Research Symposium

Eutectic Gallium-Indium (EGaIn) is a room-temperature liquid metal alloy that dramatically changes its surface tension and dynamics under an applied electric field. EGaIn has been used heavily in soft electronics engineering due to its high conductivity, malleability, and safety. However, the absence of mathematical modeling in the current literature makes its behavior difficult to understand and predict. In this study, we present a one-dimensional lubrication model for the dynamics of an EGaIn droplet moving along an inclined plane. Our model incorporates essential physical effects and parameters including oxidation, capillary action, diffusion, gravity, and Marangoni effects. In particular, we incorporate effects …

Going All-In With Vector Representations Of Electric And Magnetic Fields In Introductory Calculus-Based Physics, Craig Looney

Physics Faculty Publications

While most introductory calculus-based textbooks introduce a fully-vectorized expression for the electric field due to a point charge, they rarely – if ever – introduce a fully-vectorized expression for the magnetic field due to an infinitely long current, and corresponding field superposition problems are normally solved by the method of components (find magnitudes, break magnitudes into components, sum the respective components). In this poster I will explain why I teach a fully-vectorized approach – starting with the fully-vectorized field expressions and summing the fields vector-algebraically – alongside the more traditional method of components in my introductory calculus-based physics course, and …