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Articles 61 - 90 of 378
Full-Text Articles in Astrophysics and Astronomy
Simulations Of Electron Trajectories In An Intense Laser Focus For Photon Scattering Experiments, Grayson J. Tarbox
Simulations Of Electron Trajectories In An Intense Laser Focus For Photon Scattering Experiments, Grayson J. Tarbox
Theses and Dissertations
An experiment currently underway at BYU is designed to test whether the size of a free electron wave packet affects the character of scattered radiation. Using a semi-classical argument wherein the wave packet is treated as a diffuse charge distribution, one would expect strong suppression of radiation in the direction perpendicular to the propagating field as the wave packet grows in size to be comparable to the wavelength of the driving field. If one disallows the interaction of the wave packet with itself, as is the case when calculating the rate of emission using QED, then regardless of size, the …
Radio Emission Toward Regions Of Massive Star Formation In The Large Magellanic Cloud, Adam Johanson
Radio Emission Toward Regions Of Massive Star Formation In The Large Magellanic Cloud, Adam Johanson
Theses and Dissertations
Four regions of massive star formation in the Large Magellanic Cloud (LMC) were observed for water and methanol maser emission and radio continuum emission. A total of 42 radio detections were made including 27 new radio sources, four water masers, and eight compact HII regions. The lobes of a radio galaxy were resolved for the first time, and the host galaxy identified. Seven sources were associated with known massive young stellar objects (YSOs). A multi-wavelength analysis using both the infrared and radio spectrum was used to characterize the sources. Mid-infrared color-magnitude selection criteria for ultracompact HII (UCHII) regions in the …
Instrument For Precision Long-Term Ss-Decay Rate Measurements, M. J. Ware, Scott D. Bergeson, J. E. Ellsworth, M. Groesbeck, J. E. Hansen, D. Pace, J. Peatross
Instrument For Precision Long-Term Ss-Decay Rate Measurements, M. J. Ware, Scott D. Bergeson, J. E. Ellsworth, M. Groesbeck, J. E. Hansen, D. Pace, J. Peatross
Faculty Publications
We describe an experimental setup for making precision measurements of relative ß-decay rates of 22Na, 36Cl, 54Mn, 60Co, 90Sr, 133Ba, 137Cs, 152Eu, and 154Eu. The radioactive samples are mounted in two automated sample changers that sequentially position the samples with high spatial precision in front of sets of detectors. The set of detectors for one sample changer consists of four Geiger-Müller (GM) tubes and the other set of detectors consists of two NaI scintillators. The statistical uncertainty in the count rate is few times 0.01% per day for the GM …
Algebraic Semi-Classical Model For Reaction Dynamics, Tim Glenn Wendler
Algebraic Semi-Classical Model For Reaction Dynamics, Tim Glenn Wendler
Theses and Dissertations
We use an algebraic method to model the molecular collision dynamics of a collinear triatomic system. Beginning with a forced oscillator, we develop a mathematical framework upon which inelastic and reactive collisions are modeled. The model is considered algebraic because it takes advantage of the properties of a Lie algebra in the derivation of a time-evolution operator. The time-evolution operator is shown to generate both phase-space and quantum dynamics of a forced oscillator simultaneously. The model is considered semi-classical because only the molecule's internal degrees-of-freedom are quantized. The relative translation between the colliding atom and molecule in an exchange reaction …
Towards Stronger Coulomb Coupling In An Ultracold Neutral Plasma, Mary Elizabeth Lyon
Towards Stronger Coulomb Coupling In An Ultracold Neutral Plasma, Mary Elizabeth Lyon
Theses and Dissertations
Ultracold neutral plasmas are created by photoionizing laser-cooled atoms in a magneto-optical trap (MOT). Due to their large electrical potential energies and comparatively small kinetic energies, ultracold plasmas fall into a regime of plasma systems which are called “strongly coupled.” A priority in the field of ultracold plasmas is to generate plasmas with higher values of the strong coupling parameter Γ, which is given as the ratio of the nearest-neighbor Coulomb potential energy to the average kinetic energy. The equilibrium strong coupling in ultracold plasmas is limited by the ultrafast relaxation of the ions due to spatial disorder in the …
Investigation Of A New Method Of Estimating Acoustic Intensity And Its Application To Rocket Noise, Benjamin Young Christensen
Investigation Of A New Method Of Estimating Acoustic Intensity And Its Application To Rocket Noise, Benjamin Young Christensen
Theses and Dissertations
An alternative pressure-sensor based method for estimating the acoustic intensity, the phase and amplitude gradient estimation (PAGE) method, is presented. This method is similar to the finite-difference p-p (FD) method, in which the intensity is estimated from pressure measurements made using an array of closely spaced microphones. The PAGE method uses the same hardware as the FD method, but does not suffer from the frequency-dependent bias inherent to the FD method. Detailed derivations of the new method and the traditional FD method are presented. Both methods are then compared using two acoustic fields: a plane wave and a three monopole …
Introduction To The Development Of A Radio Astronomy System At Brigham Young University, Daniel Robert Blakley
Introduction To The Development Of A Radio Astronomy System At Brigham Young University, Daniel Robert Blakley
Theses and Dissertations
The intent of this project was founded upon the need to train students in the techniques of radio astronomy with the purpose of establishing a radio telescope in order to teach the principles and practice of radio astronomy.This document describes the theory, research, to establish the 1st generation radio telescope system within the Department of Physics and Astronomy at Brigham Young University. Included are introductions to: (1) The nature of star forming regions in the spiral arm structure of the galaxy, H I (the hydrogen spin-flip transition) and OH MASERS, (2) The of terminology used with the system components and …
Application Of An Isogeometric Boundary Element Method To The Calculation Of Acoustic Radiation Modes And Their Efficiencies, Candice Marie Humpherys
Application Of An Isogeometric Boundary Element Method To The Calculation Of Acoustic Radiation Modes And Their Efficiencies, Candice Marie Humpherys
Theses and Dissertations
In contrast to the structural modes, which describe the physical motion of vibrating structures, acoustic radiation modes describe the radiated sound power. Radiation modes are beneficial in active noise control because reducing an efficiently radiating radiation mode guarantees the reduction of radiated sound power. Much work has been done to calculate the radiation modes for simple geometries, where analytic solutions are available. In this work, isogeometric analysis (IGA) is used to provide a tool capable of analyzing the radiation modes of arbitrarily complex geometries. IGA offers increased accuracy and efficiency by using basis functions generated from Non-Uniform Rational B-Splines (NURBS) …
Psychoacoustic Effects Of High-Resolution Directivity Measurements On Room Modeling Auralizations, Nathan Eyring, Dr. Timothy Leishman
Psychoacoustic Effects Of High-Resolution Directivity Measurements On Room Modeling Auralizations, Nathan Eyring, Dr. Timothy Leishman
Journal of Undergraduate Research
Over the past years research has been conducted to understand how sound radiates from musical instruments. This has been done by recording a sphere of 2664 data points around a player through the process of many repetitions. This sphere is called the instrument’s directivity This data can be input into room modeling software to predict how an instrument will sound in any given location even before it is built. However there is the legitimate question of whether or not there this new data will change how room model sounds, and if someone listening would care. This research was an attempt …
Phase-Correlation And Propagation Analysis Of Near-Field Military Jet Noise, Jazz Myres, Dr. Kent Gee
Phase-Correlation And Propagation Analysis Of Near-Field Military Jet Noise, Jazz Myres, Dr. Kent Gee
Journal of Undergraduate Research
According to the Office of Naval Research (ONR), the United States Department of Veteran Affairs spent over $1 billion dollars on military hearing loss compensation in 2010 alone1. A major cause of hearing loss is exposure to high Sound Pressure Levels, which are caused by military aircraft. These severe levels and high risks are what motivate the overarching goal of all jet noise research: to attenuate the sound impact and reduce the risk of hearing loss. My research project helps this overall purpose by characterizing jet noise and innovating more complete methods of jet noise study. The purpose of this …
Development Of A Data Reduction Pipeline For The Rovor Observatory, Thayne Mccombs, Dr. Joseph Ward Moody
Development Of A Data Reduction Pipeline For The Rovor Observatory, Thayne Mccombs, Dr. Joseph Ward Moody
Journal of Undergraduate Research
The ROVOR observatory is a robotic, remotely controlled telescope in Delta, Utah. Since it is remotely controlled and semi-automated, it produces a very large amount of raw data. Unfortunately it took much longer to process and analyze the data than to acquire it, and, therefore, we had a backlog of over two years of data that was waiting to be processed. This delay in analyzing data was detrimental to monitoring projects because without the analysis of recent data it is difficult to determine the most interesting targets to observe.
Magnetic Symmetry-Mode Analysis Of La0.5 Ca0.5 Mno3, Eric Gibbs, Dr. Branton Campell
Magnetic Symmetry-Mode Analysis Of La0.5 Ca0.5 Mno3, Eric Gibbs, Dr. Branton Campell
Journal of Undergraduate Research
This project focuses on solving magnetic crystal structures using symmetry-mode analysis (SMA). A crystal is an arrangement of atoms in a repeating spatial pattern with the smallest repeating unit being known as the unit cell. A magnetic crystal contains atoms with a non-zero magnetic moment. A magnetic crystal’s unit cell repeats both the atomic and magnetic structure of the crystal. Neutron diffraction is a common method for studying magnetic crystals as the diffraction pattern can be used to determine the arrangement of atoms and magnetic moments within the unit cell.
Developing Microwave-Generated Hydrogen Atoms As A Reducing Agent For Tungsten Atomic Layer Deposition, Jason Kyle Anderson, Dr. David Allred
Developing Microwave-Generated Hydrogen Atoms As A Reducing Agent For Tungsten Atomic Layer Deposition, Jason Kyle Anderson, Dr. David Allred
Journal of Undergraduate Research
Traditional micro fabrication processes are confined to a small subset of possible materials due to limitations on etching and are confined to low aspect ratio fabrication due to limits in both etching and stability of thicker film deposition processes.
Generation Of A Low Velocity Controlled Beam Of Sr Ions, Jarom Jackson, Dr. Dallin Durfee
Generation Of A Low Velocity Controlled Beam Of Sr Ions, Jarom Jackson, Dr. Dallin Durfee
Journal of Undergraduate Research
The purpose of this project was to produce a slow controlled beam of Strontium (Sr) ions. This is a key step in a proposed experiment to build an ion interferometer capable of measuring electric fields to a degree of sensitivity that has never been done before. This device will be useful in conducting a number of new experiments and will help test and push the boundaries of modern electromagnetic theory.
Modeling Supernovae Light Curves: A Vital Step Toward Photometric Classification, Brittany Spencer, Dr. Shane Reese
Modeling Supernovae Light Curves: A Vital Step Toward Photometric Classification, Brittany Spencer, Dr. Shane Reese
Journal of Undergraduate Research
Type Ia supernovae play a critical role in understanding the nature of the evolving universe. The Dark Energy Survey is currently investigating the expansion rate of the universe, with the intent to gain insight into the nature of dark energy. One of their primary measures of expansion is Type Ia supernovae (DES Projects, 2011). Due to this type of supernova’s uniformity in formation, most supernova of this type explode to approximately the same absolute brightness (Goobar, 2011).
Development Of A Surface Magneto-Optic Kerr Effect Magnetometer, Susan Stoffer Sorensen, Dr. Karine Chesnel
Development Of A Surface Magneto-Optic Kerr Effect Magnetometer, Susan Stoffer Sorensen, Dr. Karine Chesnel
Journal of Undergraduate Research
The Kerr effect is a phenomenon in which as polarized visible light reflects off of a magnetized surface it experiences a small rotation in polarization. This is known as the Kerr rotation, denoted Δθ. This rotation is proportional to the magnetization of the sample, to a first-order approximation (Δθ∝M). The surface magneto-optic Kerr effect (SMOKE) is a subset of the Kerr effect which probes the magnetization of the surface of the sample. Since the samples measured by our SMOKE apparatus are as thin as 10 nm to 100 nm the surface magnetization equals the total magnetization. These samples can be …
Superparamagnetic Behavior Of Magnetite Nanoparticles: Preparation And Characterization, Matea Trevino, Dr. Karine Chesnel
Superparamagnetic Behavior Of Magnetite Nanoparticles: Preparation And Characterization, Matea Trevino, Dr. Karine Chesnel
Journal of Undergraduate Research
Magnetite (Fe3O4) nanoparticles have the unique ability of being superparamagnetic. When no field is applied to the nanoparticles, the nanoparticles’ assembly has a net magnetization of zero, meaning that the nanoparticles’ magnetic moments align in random positions leading to a net magnetization of zero. When a field is applied, the particles’ magnetic moments align with the magnetic field. This is considered superparamagnetic because this is looked at on the nanometer (nm) scale and not the atomic scale. Being able to understand this phenomenon will open up many doors in technology and medical usage. Nanocrystals, such as Fe3O4 particles, are good …
Femtosecond Frequency Comb Lock, Daniel Thrasher, Dr. Scott Bergeson
Femtosecond Frequency Comb Lock, Daniel Thrasher, Dr. Scott Bergeson
Journal of Undergraduate Research
Laser frequency control is imperative for cold atom experimentation. In our lab we use finely tuned lasers to optically cool and trap calcium atoms. Our ability to successfully trap atoms is highly dependent on the stability of the lasers we use to cool them. After trapping the atoms we use more finely tuned lasers to reveal how cold the atoms are and how quickly they leave our trap. Previous to this work our lasers were limited to 20 MHz precision. By installing a femtosecond laser as a standard by which to stabilize the other lasers in our experiment we successfully …
Dynamics Of Multi-Spin Systems : Landau-Lifshitz-Gilbert Model And Ferromagnetic Pattern Formation, Soyoung Jung, Dr. Manuel Berrondo
Dynamics Of Multi-Spin Systems : Landau-Lifshitz-Gilbert Model And Ferromagnetic Pattern Formation, Soyoung Jung, Dr. Manuel Berrondo
Journal of Undergraduate Research
Modeling has been an important part of many fields of research. Even though it sometimes could be considered to be non-practical, it has sharpened the questions and has been a useful tool for experimental research to understand what is being observed in the laboratory. Likewise, the Heisenberg model constitutes an essential stepping stone to understand anti/ferromagnetism in magnetic materials. We have been able to develop a spin model using Landau-Lifshitz-Gilbert equation enhanced with anisotropy and long range interaction that is comparable to experimental results.
Design And Implementation Of A Laser Locking Apparatus, Jarom Jackson, Dr. Dallin Durfee
Design And Implementation Of A Laser Locking Apparatus, Jarom Jackson, Dr. Dallin Durfee
Journal of Undergraduate Research
The experiment which we are building here in Dr. Durfee’s lab is a novel one, the key part of which is an ion interferometer. The interferometer consists of a beam of Sr+ ions which will be split in half. The two halves of the beam will travel along different paths, and then be recombined. Depending on the difference of phase of the two beams on recombining they may either constructively or destructively interfere with each other. Since the phase change of each beam depends on the potential energy along the path that beam follows, this will allow us to very …
The Calculation Of H-Beta Indices For Delta Scuti Variable Stars, Kelsey Jorgenson, Dr. Eric Hintz
The Calculation Of H-Beta Indices For Delta Scuti Variable Stars, Kelsey Jorgenson, Dr. Eric Hintz
Journal of Undergraduate Research
A large part of astronomical research involves gathering information about celestial objects and drawing conclusions about that information. Astronomers commonly gather data for research projects via sweeping surveys, either of particular regions of the sky or of specific kinds of stars or celestial objects. Data from these surveys are often arranged into catalogues. The aim of my research project was to fill in information gaps in the catalogue of information of known delta Scuti variable stars, particularly in the form of the hydrogen beta, or H-beta, index. I will give introductory information about delta Scuti stars as well as the …
Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies, Yanping Cai
Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies, Yanping Cai
Theses and Dissertations
Fe3O4 magnetic nanoparticles of 5 to 11 nm in size were prepared by organic methods. Particle size was analyzed by both X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques. Zero Field Cooling (ZFC) / Field Cooling (FC) and magnetization loop measurements were recorded by VSM, and they confirmed superparamagnetic behavior in the sample. The blocking temperature is found to be in the range of 30 K ~ 170 K. It has a dependence on the particle size. ZFC / FC curves also indicate the presence of magnetic coupling between particles. X-ray Magnetic Circular Dichroism (XMCD) measurements of these nanoparticles …
Estimating The Acoustic Power Of Sources In Nonideal Enclosures Using Generalized Acoustic Energy Density, Daniel Ryan Marquez
Estimating The Acoustic Power Of Sources In Nonideal Enclosures Using Generalized Acoustic Energy Density, Daniel Ryan Marquez
Theses and Dissertations
Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This …
Utah Valley Air Sample Measurements, Ryan Hamilton, Dr. Lawrenece Rees, Dr. Nolan Mangelson, Dr. Delbert Eatough
Utah Valley Air Sample Measurements, Ryan Hamilton, Dr. Lawrenece Rees, Dr. Nolan Mangelson, Dr. Delbert Eatough
Journal of Undergraduate Research
In an effort at reducing the carbon monoxide levels in the atmosphere, Utah has mandated the use of oxygenated fuels during winter inversions. While the fuel additive has been shown to reduce CO levels by as much as 4%, the unique chemistry of the air in Utah Valley has raised concerns about the oxygenated fuels contributing to air pollution in the form of fine particulate matter–a pollutant recently brought under tighter regulation by the EPA. To diagnose the problem, air samples from around Utah Valley were taken during the winter, both in times of inversion and in times when there …
A Comparison Of Y Scuti And Y Doradus Variable Stars, Matthew B. Garvin, Dr. Eric Hintz
A Comparison Of Y Scuti And Y Doradus Variable Stars, Matthew B. Garvin, Dr. Eric Hintz
Journal of Undergraduate Research
During the course of this summer, I observed a possible ã Doradus/ä Scuti variable star, V927 Herculis. Observations of this star were made using the David Derrick 16 inch telescope located on the Brigham Young University (BYU) campus in the Orson Pratt Observatory. Due to the often inclement weather, five nights of time-series photometry data were obtained. The data were compared to the known characteristics of the ä Scuti and ã Doradus class of variable stars. V927 Herculis was found to have characteristics similar to both classes. Spectroscopic data need to be obtained to make a clear distinction of which …
Preventing Asteroid Impact By Deflection: A Numerical Simulation, Rebecca J. Carlson
Preventing Asteroid Impact By Deflection: A Numerical Simulation, Rebecca J. Carlson
Journal of Undergraduate Research
Small objects from outer space collide with the earth’s atmosphere every day. Most of these are small enough to burn up completely before hitting the ground. A few, however, reach the earth’s surface as meteorites. On occasion, an asteroid large enough to cause serious darnage impacts the earth. Although impacts large enough to destroy cities only occur once in a thousand years or so, if such an event were to occur there would be great loss of life and damage of property (Rather 1992). Because of this, it is important to develop plans to deter an asteroid on a colllslon …
Pioneer Venus Orbiter Retarding Potential Analyzer Observations Of The Electron Component Of The Solar Wind And Observations Of Venus Bow Shock Crossings And The Magnetosheath Region, Noe Yamaguchi
Journal of Undergraduate Research
A bow shock is a paraboloid-shaped shockwave that forms around a planet similar to one that forms around an airplane traveling faster than the speed of sound. We may observe this shock by the change in plasma parameters before and after entering the bow shock. Those plasma parameters include temperature, density, pressure, velocity, magnetic field and others.
Study Of The Eclipsing Binary Ah Cancri, Delora Chere' Tanner, Dr. Benjamin Taylor
Study Of The Eclipsing Binary Ah Cancri, Delora Chere' Tanner, Dr. Benjamin Taylor
Journal of Undergraduate Research
Unlike research in many other disciplines, astronomical research is highly dependent upon the weather. My original proposed research was to further the task of calibrating standard stars in the M67 open cluster. Unfortunately the weather was unfavorable during the window of time that this cluster was available for viewing, therefore, I could not secure the amount of data needed to conduct my proposed research. I decided to change the focus of my research to an individual star located in M67, AH Cancri. I was able to use raw archive data of the M67 star field to study this star.
Scalar Waves Scattering Off A Cylinder, David Oliphant, Dr. R. Steven Turley
Scalar Waves Scattering Off A Cylinder, David Oliphant, Dr. R. Steven Turley
Journal of Undergraduate Research
Scattering problems are common in physics. A scattered (reflected) wave or particle from an object can give us hints to the nature of the object’s shape, size, color, or composition. This is the basic principle behind sonar, radar, ultrasound, NMR, and even vision. One technique in determining the nature of a scattered wave is called the Method of Moments. It involves solving the Helmholtz equation by representing the object’s response or current as a sum of basis functions and weights. The number of basis functions used is important. If there are too many the computational time becomes inordinate. However, there …
Extreme Ultraviolet Ellipsometry, Spencer E. Olson, Dr. R. Steven Turley
Extreme Ultraviolet Ellipsometry, Spencer E. Olson, Dr. R. Steven Turley
Journal of Undergraduate Research
Ellipsometry, a common technique used with visible light, measures the change of the state of polarization as it reflect off a material. By so doing, the way that light interacts with materials can be understood more clearly. Also, optical properties, known as the index of refraction and absorption coefficient, can be found from this technique. With these known optical properties of various materials, elements, such as mirrors and polarizers, can be optimized for optical instruments. The name ellipsometry comes from the fact that the technique is based on the analysis of what is called ellipsometrically polarized light. For the simple …