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Full-Text Articles in Physics

Embedded-Atom-Method Modeling Of Alkali-Metal/Transition-Metal Interfaces, Jake D. Christensen Dec 2020

Embedded-Atom-Method Modeling Of Alkali-Metal/Transition-Metal Interfaces, Jake D. Christensen

All Graduate Theses and Dissertations

Understanding the thermal properties of materials is essential to using those materials for technological advancement which can benefit civilization. For example, it has been proposed that essential components of tokamaks, devices which perform fusion, be made out of tungsten with a thin layer of lithium on the surface. To that end, this thesis seeks to calculate the thermal properties of a layer of alkali atoms, like lithium and sodium, on tungsten and molybdenum substrates. We use an Embedded Atom Method (EAM) model to perform our calculations. This type of model has been widely used to describe the interaction between atoms ...


The Development And Use Of A Secondary Electron Yield Database For Spacecraft Charge Modeling, Phillip Lundgreen Dec 2020

The Development And Use Of A Secondary Electron Yield Database For Spacecraft Charge Modeling, Phillip Lundgreen

All Graduate Theses and Dissertations

Charge modeling of electron-solid interactions requires a detailed and accurate compilation of experimental data on which to base its physics and against which to test its predictions. Historically researchers used methods involving individual research or information taken from existing, vague, databases that were often found wanting. To streamline the charge modeling process, a collection of data has been assembled and categorized based upon surface morphology and contamination from various published sources and existing databases. The quality and quantity of the compilation vary widely with very little information offered with regards to surface conditions of various materials (contamination, morphology, etc. ...). Included ...


Spectral Properties Of Quaternionic Unit Gain Cycles, Nolan J. Coble Sep 2020

Spectral Properties Of Quaternionic Unit Gain Cycles, Nolan J. Coble

Senior Honors Theses

The quaternions are a non-commutative division ring that extends the complex numbers. A gain graph is a simple graph together with a gain function that assigns a value from an arbitrary group to each edge of the graph. We can define certain concepts on these graphs such as adjacency and Laplacian matrices, gains of paths, and more. If we restrict ourselves to the unit norm quaternions, we can define quaternionic unit gain graphs, or U(H)-gain graphs, as gain graphs where the domain of the gain function is the unit quaternions. Traditional methods from spectral graph theory are not ...


Wave Propagation In Random And Topological Media, Yuhao Kang Sep 2020

Wave Propagation In Random And Topological Media, Yuhao Kang

Dissertations, Theses, and Capstone Projects

This thesis discusses wave propagation in two kinds of systems, random media and topological insulators. In a disordered system, the wave is randomized by multiple scattering. The scattering matrix and associated delay times are powerful tools with which to describe wave transport. We discuss the relation among the Wigner time, the transmission time, and energy density in a lossless or lossy system. We propose the zeros of the transmission matrix and show how to manipulate the zero-transmission mode in a nonunitary system. In a photonic topological insulator, we realize an edge mode and discuss its robustness in the face of ...


Variability Of Active Galactic Nuclei From Differential Photometry, Nicholas Steven Yee Sep 2020

Variability Of Active Galactic Nuclei From Differential Photometry, Nicholas Steven Yee

Physics

The Seoul AGN Monitoring Project, or SAMP for short, is an international project (PI Jonghak Woo from Korea) with the goal of measuring the masses of black holes residing in the center of massive active galactic nuclei (AGNs). AGNs are some of the brightest objects in the universe. Their light is attributed to the accretion of material onto the black hole. However, these objects are too distant to spatially resolve the gravitational sphere of influence of the black hole directly. Instead, we use a technique called reverberation mapping which observes the variability of the AGN power-law continuum emission and the ...


Particle Dynamics In Anti-De Sitter Space By Eih Method, Jiusi Lei Sep 2020

Particle Dynamics In Anti-De Sitter Space By Eih Method, Jiusi Lei

Dissertations, Theses, and Capstone Projects

Following the work of Einstein, Infeld and Hoffmann, we show that particle dynamics in Anti-de Sitter spacetime can be built up by regarding singularities in spacetime manifold as the source of particles.

Since gauge fields play a foundational role in the action, the singularities are chosen to be point-like instantons. Their winding number, defined by an integration on the spheres surrounding those singularities, will turn out to be related to their masses. And their action, derived from the Chern-Simons forms, will be a co-adjoint orbit action, with group element g ∈ SO(4, 2) describing the collective coordinates of the particle ...


An Accurate Solution Of The Self-Similar Orbit-Averaged Fokker-Planck Equation For Core-Collapsing Isotropic Globular Clusters: Properties And Application, Yuta Ito Sep 2020

An Accurate Solution Of The Self-Similar Orbit-Averaged Fokker-Planck Equation For Core-Collapsing Isotropic Globular Clusters: Properties And Application, Yuta Ito

Dissertations, Theses, and Capstone Projects

Hundreds of dense star clusters exist in almost all galaxies. Each cluster is composed of approximately ten thousand through ten million stars. The stars orbit in the clusters due to the clusters' self-gravity. Standard stellar dynamics expects that the clusters behave like collisionless self-gravitating systems on short time scales (~ million years) and the stars travel in smooth continuous orbits. Such clusters temporally settle to dynamically stable states or quasi-stationary states (QSS). Two fundamental QSS models are the isothermal- and polytropic- spheres since they have similar structures to the actual core (central part) and halo (outskirt) of the clusters. The two ...


Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner Sep 2020

Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner

Dissertations, Theses, and Capstone Projects

One of the best tools we have for the edification of physics is the analogy. When we take our classical set of states and dynamical variables in phase space and treat them as vectors and Hermitian operators respectively in Hilbert space through the canonical quantization, we lose out on a lot of the intuition developed with the previous classical physics. With classical physics, through our own experiences and understanding of how systems should behave, we create easy-to-understand analogies: we compare the Bohr model of the atom to the motion of the planets, we compare electrical circuits to the flow of ...


Control Of Molecular Energetics And Transport Via Strong Light-Matter Interaction, Rong Wu Sep 2020

Control Of Molecular Energetics And Transport Via Strong Light-Matter Interaction, Rong Wu

Dissertations, Theses, and Capstone Projects

Strong light-matter coupling in excitonic systems results in the formation of half-light half-matter quasiparticles called exciton polaritons. These hybrid quasiparticles take on the best of both systems, namely, the long-range propagation and coherence arising from the photonic component and the nonlinear interaction from the excitonic component. We develop methods for making high quality factor cavities and investigate the potential applications of these strongly coupled states arising specifically in organic molecular systems.

In the first project we investigate the potential of organic dye molecules to undergo condensation in an optical cavity at room temperature. The second study involves the use of ...


Linear And Non-Linear Elastic Constants Of Crystalline Materials From First-Principles Calculations, David Cuffari Sep 2020

Linear And Non-Linear Elastic Constants Of Crystalline Materials From First-Principles Calculations, David Cuffari

Dissertations, Theses, and Capstone Projects

Novel methods based on the use of density functional theory (DFT) calculations are developed and applied to calculate linear and non-linear elastic constants of materials at zero and finite temperature. These methods rely on finite difference techniques and are designed to be general, numerically accurate, and suitable to investigate the thermoelastic properties of anharmonic materials. A first method was developed to compute the third-order elastic constants of crystalline materials at zero temperature, a task that is numerically challenging and is currently undertaken by using approaches typically applicable to cubic and hexagonal crystalline systems. This method relies on numerical differentiation of ...


Yield-Stress Fluids In Confined Geometries, Thalia Magyar Aug 2020

Yield-Stress Fluids In Confined Geometries, Thalia Magyar

Electronic Thesis and Dissertation Repository

A yield-stress fluid is a material that has properties of both solids and conventional liquids that only begins to flow when subject to a finite stress. The behaviour of yield-stress fluids is interesting and important in many applications. It is expected that the rheological properties of a yield-stress fluid will change when confined to a region with a length scale comparable to the characteristic scale of its microstructure. The particle size and polydispersity of two yield-stress fluids, Carbopol and poly(N-isopropylacrylamide), were determined using dynamic light scattering. A rheological characterization was performed on these two yield-stress fluids. Flow of ...


Understanding The Magnetic Properties Of Ii-Vi Semiconductor Nanocrystals, Alex Khammang Aug 2020

Understanding The Magnetic Properties Of Ii-Vi Semiconductor Nanocrystals, Alex Khammang

Electronic Theses and Dissertations

Semiconductor nanocrystals (NC) are well known for their unique size tunable optical properties making them suitable candidates for devices such as light emitting diodes (LEDs), solar cells, and cellular labels. II-VI semiconductors in the bulk form behave diamagnetically, but can inherit paramagnetic (PM) or ferromagnetic (FM) properties at the nanoscale. Reports suggest that the emergence of weak PM or FM behavior in undoped NCs are attributed to the increased surface to volume ratio compared for NCs. Traditionally, these NCs only obtain magnetic properties after doping with certain transition metals, such as Co, Mn, or Fe. Many mechanisms have been proposed ...


Effects Of Surfactants On The Generation Of Sea Spray During Tropical Cyclones, Breanna L. Vanderplow Aug 2020

Effects Of Surfactants On The Generation Of Sea Spray During Tropical Cyclones, Breanna L. Vanderplow

All HCAS Student Capstones, Theses, and Dissertations

Despite significant improvement in computational and observational capabilities, predicting intensity and intensification of major tropical cyclones remains a challenge. In 2017 Hurricane Maria intensified to a Category 5 storm within 24 hours, devastating Puerto Rico. In 2019 Hurricane Dorian, predicted to remain tropical storm, unexpectedly intensified into a Category 5 storm and destroyed the Bahamas. The official forecast and computer models were unable to predict rapid intensification of these storms. One possible reason for this is that key physics, including microscale processes at the air-sea interface, are poorly understood and parameterized in existing forecast models.

Under tropical cyclones, the air-sea ...


Investigation Of The Chemical Kinetics In An Atmospheric Cold Plasma Towards Co2 Conversion, Daniel Piatek Aug 2020

Investigation Of The Chemical Kinetics In An Atmospheric Cold Plasma Towards Co2 Conversion, Daniel Piatek

Seton Hall University Dissertations and Theses (ETDs)

Hydrogenation of carbon dioxide (CO2) to methanol (CH3OH) is a promising route for utilization of excess and residual CO2. The conversion of CO to methanol is a well-developed process but the ability to use CO2 as a feed gas still requires high pressures (30-300 atm) to attain conversion. In this work, the hydrogenation of CO2 is explored using H2O as well as H2 in an atmospheric pressure nonthermal (cold) plasma created with a dielectric barrier discharge (DBD) reactor. Different gas mixtures such as argon (Ar) and helium (He) are used to understand their interactions in the process of CO2 hydrogenation ...


Characterization Of A Novel Double Cooled Electrode Dbd Reactor For Ozone Generation, Gustavo Duarte Aug 2020

Characterization Of A Novel Double Cooled Electrode Dbd Reactor For Ozone Generation, Gustavo Duarte

Seton Hall University Dissertations and Theses (ETDs)

The Dielectric Barrier Discharge (DBD) is used to generate atmospheric or higher-pressure non-thermal plasmas and has found various commercial applications such as in industrial large-scale ozone generation. Ozone (O3 ) is a powerful chemical reactant that is used to kill bacteria, to deodorize and to perform water purification. The effectiveness of the DBD reactors depends on the electrode arrangements, gap lengths, dielectric materials, operating gases and feed gas quality to name a few. However, the production of O3 is heat sensitive. In order to prevent O3 destruction thermal cooling of the DBD is needed. The industry approach to ...


Cooking Systems Using Aluminum Foam, Ryan Tetsuo Mizukami Aug 2020

Cooking Systems Using Aluminum Foam, Ryan Tetsuo Mizukami

Physics

In developing countries, the use of wood burning fires for cooking is cause for illness and death. With this in mind, research was conducted to develop a solar cooking device capable of cooking of soup within 15 mins in order to reduce the negative impacts of cooking with wood. Current methods of solar-based cooking, such as solar concentrators and solar tube ovens, are impractical. A small solar panel is a cost-effective way to produce energy but will not produce enough power to cook within a reasonable amount of time. Even if it is assumed that all of the energy produced ...


Simulation And Development Of The Radial Time Projection Chamber For The Bonus12 Experiment In Clas12, Nathan M. Dzbenski Aug 2020

Simulation And Development Of The Radial Time Projection Chamber For The Bonus12 Experiment In Clas12, Nathan M. Dzbenski

Physics Theses & Dissertations

Knowledge of the structure of nucleons (i:e: protons and neutrons) is a central topic of interest to nuclear/particle physicists. Much more is known about the structure of the proton than the neutron due to the lack of high-density free neutron targets. The Barely Off-shell Nucleon Structure experiment (BONuS12) at Jefferson Lab (JLab) is a second generation experiment upgraded/optimized to advance our knowledge of the neutron's structure using the deep-inelastic scattering of electrons off deuterium. Typically, since deuterium is a nuclear target, corrections for off-shell and nuclear binding effects must be taken into account in order to ...


Storm-Time Equatorial Thermospheric Dynamics And Electrodynamics, Luis A. Navarro Dominguez Aug 2020

Storm-Time Equatorial Thermospheric Dynamics And Electrodynamics, Luis A. Navarro Dominguez

All Graduate Theses and Dissertations

We present the first complete study of the dynamics of the equatorial upper atmosphere (180-350 km) during periods of strong magnetic activity driven by the Sun, which are generally referred as geomagnetic storms. These storms have the potential to considerably affect satellite-based communications and navigation systems among other severe technological challenges. We used large databases of two of the most important parameters at these altitudes, which are the velocities of the neutral and ionized gas (plasma) referred to as neutral winds and plasma drifts. These measurements were acquired in the Peruvian equatorial region by the Jicamarca radar and by a ...


Massive Graviton Spectra In Supergravity, Kevin Dimmitt Aug 2020

Massive Graviton Spectra In Supergravity, Kevin Dimmitt

All Graduate Theses and Dissertations

Development of a unified theory of physics would pave the way for new research and technology development for many years to come. Unfortunately, the two best current theories explaining nature, the Standard Model of particle physics and general relativity, do not seem to be compatible, requiring the development of more complicated models which contains both of these at their respective limits. Supergravities are one set of theories which may, at least in part, provide hints as to how it may be possible to unify physics into a single model.

This research project follows from a line of investigation which the ...


Active Magnetic Radiation Shielding For Long-Duration Human Spaceflight, Kristine Ferrone Aug 2020

Active Magnetic Radiation Shielding For Long-Duration Human Spaceflight, Kristine Ferrone

The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences Dissertations and Theses (Open Access)

Exploration of interplanetary space presents dramatic hazards to human survival.

Space radiation hazards outside the protection of the Earth’s magnetosphere can

produce both acute and chronic health risks and thus become limiting factors for

NASA’s planned mission to Mars by the 2030s. Radiation exposure on a Mars mission

is delivered primarily by high energy ions from galactic cosmic rays and moderate

energy protons from solar particle events. The chronic radiation dose due to galactic

cosmic rays on a typical Mars mission is on the order of 1 Sv, and additional acute

radiation dose from solar flares can reach ...


Development And Demonstration Of A Pico-Watt Calorimeter For Optical Absorption Spectroscopy, Behshad Roshanzadeh Jul 2020

Development And Demonstration Of A Pico-Watt Calorimeter For Optical Absorption Spectroscopy, Behshad Roshanzadeh

Optical Science and Engineering ETDs

An optical calorimeter for sensitive absorption measurements of non-radiative samples at 4 K was designed, built, and demonstrated. It consists of a cryostat cooled by a commercial pulse tube (PTC) refrigerator, a measurement chamber housing the sample and thermometers, and various fiber-coupled light sources. By employing measures to damp mechanical noise from the environment and active temperature stabilization of critical components of the instrument temperature noise as low as 6 nK/√Hz at 50 mHz was achieved under 15 mW of optical excitation. An optical absorption induced temperature increase of the sample as small as 2.5 nK could be ...


Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani Jul 2020

Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani

Optical Science and Engineering ETDs

Intracavity Phase Interferometry (IPI) using two correlated, counter-propagating frequency combs (pulse trains) in mode-locked lasers has evolved into a powerful technique for high-precision metrology. In this method a physical parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. Inside a laser cavity, that phase shift becomes a frequency shift (phase shift/round-trip time) applied to the whole frequency comb created by this pulse as it exits the cavity at each round-trip. This frequency shift is measured by interfering this comb with a reference comb created by a reference pulse circulating in the same ...


Quantum Criticality In Strongly Correlated Electron Systems, Samuel Obadiah Kellar Jul 2020

Quantum Criticality In Strongly Correlated Electron Systems, Samuel Obadiah Kellar

LSU Doctoral Dissertations

The study of the Hubbard model in three dimensions contains a variety of phases dependent upon the chosen parameters. This thesis shows that there is the indication of a zero temperature phase transition at a finite doping. The Hubbard model has been used to identify a similar quantum critical point in two dimensions. The presented results continue these investigations. The system demonstrates a strange metal phase at finite temperature which cannot be described in term of the conventional Fermi liquid. While there have been extensive studies over the past three decades for such materials in two dimensions, there are few ...


Identifying Structure Transitions Using Machine Learning Methods, Nicholas Walker Jul 2020

Identifying Structure Transitions Using Machine Learning Methods, Nicholas Walker

LSU Doctoral Dissertations

Methodologies from data science and machine learning, both new and old, provide an exciting opportunity to investigate physical systems using extremely expressive statistical modeling techniques. Physical transitions are of particular interest, as they are accompanied by pattern changes in the configurations of the systems. Detecting and characterizing pattern changes in data happens to be a particular strength of statistical modeling in data science, especially with the highly expressive and flexible neural network models that have become increasingly computationally accessible in recent years through performance improvements in both hardware and algorithmic implementations. Conceptually, the machine learning approach can be regarded as ...


Topics In Gravitational Wave Physics, Aaron David Johnson Jul 2020

Topics In Gravitational Wave Physics, Aaron David Johnson

Theses and Dissertations

We begin with a brief introduction to gravitational waves. Next we look into the origin of the Chandrasekhar transformations between the different equations found by perturbing a Schwarzschild black hole. Some of the relationships turn out to be Darboux transformations. Then we turn to GW150914, the first detected black hole binary system, to see if the nonlinear memory might be detectable by current and future detectors. Finally, we develop an updated code for computing equatorial extreme mass ratio inspirals which will be open sourced as soon as it has been generalized for arbitrary inclinations.


Learning Assistant And Instructor Communication: Impacts On Perceived Efficacy, Jahangir Rassouli, Laura Ríos Jul 2020

Learning Assistant And Instructor Communication: Impacts On Perceived Efficacy, Jahangir Rassouli, Laura Ríos

Physics

The Learning Assistant (LA) Model was co-developed by Richard McCray and Valerie Otero at the University of Colorado Boulder in 2003. In this model, senior undergraduate students serve as facilitators for group discussion in lower-division courses, and employ evidenced-based practices for promoting inquiry and active learning [1]. Since its inception, the LA model has grown to various departments, disciplines, and universities.

At California Polytechnic State University San Luis Obispo (Cal Poly), the LA program in the physics department is still in its early stages. As such, it is an environment rich for exploration into the affordances, limitations, and benefits of ...


Radiation-Balanced Fiber Lasers And Amplifiers, Esmaeil Mobini Souchelmaei Mr Jul 2020

Radiation-Balanced Fiber Lasers And Amplifiers, Esmaeil Mobini Souchelmaei Mr

Optical Science and Engineering ETDs

Over the past decades, high-power fiber lasers and amplifiers have been extensively under research to achieve higher output powers. However, temperature rise in the core of fiber lasers and amplifiers has been a big issue in power-scaling. Radiation-balancing is a viable technique introduced for effective heat mitigation in lasers and amplifiers by S. Bowman in 1995. Radiation-balancing relies on solid-state laser cooling as a self-cooling mechanism to mitigate the generated heat in lasers and amplifiers. To implement the mentioned idea in fiber lasers and amplifiers, a set of issues should be scrutinized; (i) the amenability of silica glass (as the ...


Visualization Of Brown Fat Using X-Ray Dark Field Imaging, Troy D. Jacobs Jun 2020

Visualization Of Brown Fat Using X-Ray Dark Field Imaging, Troy D. Jacobs

LSU Master's Theses

Introduction: Obesity has become a major societal issue. Many researchers are looking for ways to combat this growing epidemic. Brown adipose tissue (BAT) might be a way to help individuals overcome the challenges associated with weight loss and maintenance of weight loss, but a better understanding of BAT and how to control and utilize it is needed. BAT differs from white adipose tissue (WAT) in that BAT is rich with mitochondria and therefore is metabolically active. BAT is a source of non-shivering thermogenesis and can be activated both by cold exposure and pharmacologically. Current methods of assessing BAT activity are ...


Van Der Waals Epitaxy Of Ultrathin Early Transition Metal (Ti & V) (Di)Selenides: Charge And Magnetic Order In The Ultrathin Limit, Manuel Bonilla Lopez Jun 2020

Van Der Waals Epitaxy Of Ultrathin Early Transition Metal (Ti & V) (Di)Selenides: Charge And Magnetic Order In The Ultrathin Limit, Manuel Bonilla Lopez

Graduate Theses and Dissertations

Since the isolation of graphene in 2004, two-dimensional (2D) layered materials, specially the transition metal dichalcogenides (TMDs), have attracted immense interest from theoreticians and experimentalist due to the diversity of properties presented in this family of materials. The main reason for the interest in such materials has been the observation of emergent properties as a consequence of the reduced dimensions, i.e. the monolayer regime. Initially the monolayer regime was obtained via the scotch-tape method. The implementation of exfoliation techniques was successful since layered 2D materials are composed of stacked layers held together by weak van der Walls forces that ...


Investigation Into Reduced Thermal Conductivity For Half-Heusler Alloys And Identification Of Novel Multinary Chalcogenides Possessing Intrinsically Low Thermal Conductivity, Dean Hobbis Jun 2020

Investigation Into Reduced Thermal Conductivity For Half-Heusler Alloys And Identification Of Novel Multinary Chalcogenides Possessing Intrinsically Low Thermal Conductivity, Dean Hobbis

Graduate Theses and Dissertations

The current climate makes the need for sustainable energy production a priority, leading to keen interest towards the advancement of “green” energy sources and technology. This necessity has led to a multidisciplinary scientific approach with collaborations across various fields that are looking to solve this extremely important problem. One such technology is thermoelectric devices, which are attractive due to the fact that they provide direct solid-state conversion of heat to electrical power, and vice versa. This in turn allows for both waste heat recovery and sustainable refrigeration. One key aspect that is preventing the wide scale commercial use of thermoelectric ...