Astrophysics and Astronomy | Open Access Articles

Semiclassical Quantization: Corrections And Causes, Teresa Griffin

Journal of Undergraduate Research

My research over the past six months has produced a method of understanding the differences between semiclassical approximation methods and the exact quantum results.

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Work Towards Building An Extreme Ultraviolet Ellipsometer, Cort N. Johnson, Dr. David D. Allred

Journal of Undergraduate Research

The extreme ultraviolet (EUV) optics group at Brigham Young University uses thin film technology to develop multiplayer mirrors and designed to reflect well at certain EUV wavelengths. We need methods of measuring layer thickness on the order of a few angstroms. One method often used in thin film sample analysis is ellipsometry.

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Determining Optical Constants With An Euv Polarimeter, Fabian Walter, Dr. R. Steven Turley

Journal of Undergraduate Research

Characterizing mirrors is of great importance when designing optical devices. In order to control the reflectivity, these mirrors are made of multilayer structures. The index of refraction n, which allows for the calculation of the reflectivity, depends on the wavelength of the light. In the XUV (extreme ultraviolet) regime, n is not well known and experiments to determine it have to be done under vacuum due to the absorption of XUV light by air. This complicates the performing of experiments with light of that wavelength.

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Characteristics Of An Infrared, Slitless, Spectroscopic, Emission-Line Galaxy Survey, Jacob Peter Fugal, Dr. J. Ward Moody

Journal of Undergraduate Research

Cosmology has always attracted the minds of those who pursue the burning question of how the universe began. Since Edwin Hubble proved not only the existence of galaxies outside the Milky Way but also that the further away they are, the faster they are moving away, more and more research has given support to the “Big Bang” theory of the birth of the universe. This research includes the discovery of the cosmological microwave background radiation and the agreement of modeled and observed ratios of Hydrogen, Deuterium, Helium, and Lithium seen in primitive areas of galaxies.

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Variability In Quasars, Catherine Morris, Dr. Eric Hintz

Journal of Undergraduate Research

This project looked for variability in quasars 3C273 and Mark 509. Between May 2003 and July 2003 several nights of data were taken on these quasars. The project was also to see if “good” data on quasars could be obtained using the BYU 16” telescope, since not much research has been done on this topic at BYU. Over the summer data were also taken on various other quasars whose brightness ranged between 12 and 14.

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Constructing The Remote Observatory For Variable Object Research, Jason A. Gilbert, Dr. J. Ward Moody

Journal of Undergraduate Research

Scientists who attempt to unravel the mysteries of the universe have some physical limitations to deal with in their quest. For example, an observer must stay up all night to operate the telescopes that record the data. There are now automated telescopes that allow the scientist to enter a list of objects (stars, asteroids, planets, galaxies, etc.) into the telescope’s computer, and the telescope will move by itself to each one, taking and recording data throughout the course of the night. Some telescopes can even be operated remotely so the scientists can run them from their offices, or even their …

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Development And Validation Of An Automated Directivity Acquisition System Used In The Acquisition, Processing, And Presentation Of The Acoustic Far-Field Directivity Of Musical Instruments In An Anechoic Space, Nicholas J. Eyring

Theses and Dissertations

A high spatial resolution acoustic directivity acquisition system (ADAS) has been developed to acquire anechoic measurements of the far field radiation of musical instruments that are either remote controlled or played by musicians. Building upon work performed by the BYU Acoustic Research Group in the characterization of loudspeaker directivity, one can rotate a musical instrument with sequential azimuthal angle increments under a fixed semicircular array of microphones while recording repeated notes or sequences of notes. This results in highly detailed and instructive directivity data presented in the form of high-resolution balloon plots. The directivity data and corresponding balloon plots may …

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Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein

Theses and Dissertations

Military aircraft generate high-amplitude noise which can cause injury to attending personnel. Efforts to mitigate the effects of this noise require a detailed understanding of the propagation of the noise, which was shown previously to be nonlinear. This thesis presents an analysis of high-amplitude noise propagation, emphasizing measures used to quantify the importance of considering nonlinearity. Two measures of the importance of nonlinearity are compared. These measures are the wave steepening factor and a skewness estimate. The wave steepening factor is a measure of how much nonlinear waveform steepening has occurred in a waveform. The skewness estimate is the skewness …

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Characterization Of Ingaas Quantum Dot Chains, Tyler Drue Park

Theses and Dissertations

InGaAs quantum dot chains were grown with a low-temperature variation of the Stranski-Krastanov method, the conventional epitaxial method. This new method seeks to reduce indium segregation and intermixing in addition to giving greater control in the growth process. We used photoluminescence spectroscopy techniques to characterize the quality and electronic structure of these samples. We have recently used a transmission electron microscope to show how the quantum dots vary with annealing temperature. Some questions relating to the morphology of the samples cannot be answered by photoluminescence spectroscopy alone. Using transmission electron microscopy, we verified flattening of the quantum dots with annealing …

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Simulation Of 810 Nm Light Propagation Through The Human Finger For Non-Invasive Blood Analysis, Nichole Millward Maughan

Theses and Dissertations

Non-invasive blood analysis devices that can measure characteristics less prominent than the oxygenation of hemoglobin are of interest in the medical community. An important step in creating these devices is to model the interaction of photons with human tissue in increasingly greater physiological detail. We have modeled, using a Monte Carlo technique, the interaction of photons through epidermis, blood and water arranged both in layers and in a homogeneous mixture. We confirm the expected linear relation between photon attenuation and material volumetric percentage in our two-layer models. We discovered that this relationship becomes non-linear in the homogeneously mixed models where …

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Cluster Expansion Models Via Bayesian Compressive Sensing, Lance Jacob Nelson

Theses and Dissertations

The steady march of new technology depends crucially on our ability to discover and design new, advanced materials. Partially due to increases in computing power, computational methods are now having an increased role in this discovery process. Advances in this area speed the discovery and development of advanced materials by guiding experimental work down fruitful paths. Density functional theory (DFT)has proven to be a highly accurate tool for computing material properties. However, due to its computational cost and complexity, DFT is unsuited to performing exhaustive searches over many candidate materials or for extracting thermodynamic information. To perform these types of …

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Experimental Analysis Of Energy-Based Acoustic Arrays For Measurement Of Rocket Noise Fields, Jarom Henry Giraud

Theses and Dissertations

Microphone arrays are useful for measuring acoustic energy quantities (e.g. acoustic intensity) in the near-field of a full-scale solid rocket motor. Proper characterization of a rocket plume as a noise source will allow for more accurate predictions in engineering models that design for protection of structures, payloads and personnel near the rockets. Acoustic intensity and energy density quantities were measured in three rocket noise fields and have shown that the apparent source region of the rocket becomes smaller and moves upstream as frequency increases. Theoretical results accounting for some scattering and finite-difference errors arising in these types of energy-based measurements …

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Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough

Theses and Dissertations

The material properties of low stress silicon nitride make it a possible replacement material for beryllium in X-ray windows. In this study, X-ray windows made of LPCVD deposited low stress silicon nitride are fabricated and characterized. The Young's modulus of the LPCVD low stress silicon nitride are characterized and found to be 226±23 GPa. The residual stress is characterized using two different methods and is found to be 127±25 MPa and 141±0.28 MPa. Two support structure geometries for the low stress silicon nitride X-ray windows are used. X-ray windows with thicknesses of 100 nm and 200 nm are suspended on …

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Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey

Theses and Dissertations

A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.

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Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson

Theses and Dissertations

The Direct Simulation Monte Carlo algorithm as coded in FENIX is used to model the transport of trace ions in the first vacuum stage of the inductively coupled plasma mass spectrometer. Haibin Ma of the Farnsworth group at Brigham Young University measured two radial trace density profiles: one 0.7 mm upstream of the sampling cone and the other 10 mm downstream. We compare simulation results from FENIX with the experimental results. We find that gas dynamic convection and diffusion are unable to account for the experimentally-measured profile changes from upstream to downstream. Including discharge quenching and ambipolar electric fields, however, …

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Modeling Radial Bernstein Modes In A Finite-Length Axisymmetric Non-Neutral Plasma, Mark Andrew Hutchison

Theses and Dissertations

Axisymmetric radial Bernstein modes are known to exist in non-neutral plasmas and have been studied theoretically and computationally in 1D, but detection of these modes has still proven to be difficult due to self-shielding. To help advance the work on this front we created a 2D particle-in-cell (PIC) code that simulates a non-neutral plasma in a Malmberg-Penning trap. A detailed description of the PIC code itself has been included that highlights the benefits of using an $r^2$--$z$ grid and how it can be tested. The focus of the PIC simulation was to discover how best to drive and detect these …

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Advanced Numerical Methods In General Relativistic Magnetohydrodynamics, Michael J. Besselman

Theses and Dissertations

We show our work to refine the process of evolutions in general relativistic magnetohydrodynamics. We investigate several areas in order to improve the overall accuracy of our results. We test several versions of conversion methodologies between different sets of variables. We compare both single equation and two equations solvers to do the conversion. We find no significant improvement for multiple equation conversion solvers when compared to single equation solvers. We also investigate the construction of initial data and the conversion of coordinate systems between initial data code and evolution code. In addition to the conversion work, we have improved some …

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Researching Effective Methods For Teaching The Phases Of The Moon, Heather Patti Jones

Theses and Dissertations

This study investigated the effectiveness of commonly used instructional methods for teaching the phases of the Moon to fifth and sixth grade students. The instructional methods investigated were the use of diagrams, animations, and models. The effectiveness of each method was tested by measuring students' understanding of Moon phases with a pre and post-assessment after receiving instruction with a specific method or combination of methods. These methods were then evaluated for their ability to help students learn essential concepts, reinforce relevant vocabulary and discourage misconceptions. Results showed that students had better scores with less prevalence of misconception when they were …

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Long-Lived Electron Spins In A Modulation Doped (100) Gaas Quantum Well, John S. Colton, D. Meyer, K Clark, D. Craft, J. Cutler, T. Park, P. White

Faculty Publications

We have measured T1 spin lifetimes of a 14 nm modulation-doped (100) GaAs quantum well using a time-resolved pump-probe Kerr rotation technique. The quantum well was selected by tuning the wavelength of the probe laser. T1 lifetimes in excess of 1 Us were measured at 1.5 K and 5.5 T, exceeding the typical T2 lifetimes that have been measured in GaAs and II-VI quantum wells by orders of magnitude. We observed effects from nuclear polarization, which were largely removable by simultaneous nuclear magnetic resonance, along with two distinct lifetimes under some conditions that likely result from probing two differently localized …

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Nanoscale Surface Patterning And Applications: Using Top-Down Patterning Methods To Aid Bottom-Up Fabrication, Anthony Craig Pearson

Theses and Dissertations

Bottom-up self-assembly can be used to create structures with sub-20 nm feature sizes or materials with advanced electrical properties. Here I demonstrate processes to enable such self-assembling systems including block copolymers and DNA origami, to be integrated into nanoelectronic devices. Additionally, I present a method which utilizes the high stability and electrical conductivity of graphene, which is a material formed using a bottom-up growth process, to create archival data storage devices. Specifically, I show a technique using block copolymer micelle lithography to fabricate arrays of 5 nm gold nanoparticles, which are chemically modified with a single-stranded DNA molecule and used …

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Curious Growth Of A Buried Sio2 Layer, Thomas O. Mcconkie

Theses and Dissertations

Initial investigation of Moxtek wire grid polarizers composed of Al and coated with SiO2 - SiX - SiO2 (where SiX is used to indicate a Si rich layer whose complete composition is not to be disclosed for proprietary reasons) showed a growth of 3x in the inner (closest to Al) SiO2 layer after baking. Upon removing the X and varying rib composition and layering composition and geometries in 12 sets of before and after samples, no obvious growth was observed. Even baking the original unbaked sample yielded no growth. Our data suggest that the initial conclusion of buried oxide growth …

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Quantum Dynamics Using Lie Algebras, With Explorations In The Chaotic Behavior Of Oscillators, Ryan Thomas Sayer

Theses and Dissertations

We study the time evolution of driven quantum systems using analytic, algebraic, and numerical methods. First, we obtain analytic solutions for driven free and oscillator systems by shifting the coordinate and phase of the undriven wave function. We also factorize the quantum evolution operator using the generators of the Lie algebra comprising the Hamiltonian. We obtain coupled ODE's for the time evolution of the Lie algebra parameters. These parameters allow us to find physical properties of oscillator dynamics. In particular we find phase-space trajectories and transition probabilities. We then search for chaotic behavior in the Lie algebra parameters as a …

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Array-Based Characterization Of Military Jet Aircraft Noise, David William Krueger

Theses and Dissertations

Since the 1950s the jet aeroacoustics community has been involved in predicting and measuring the noise distribution in jets. In this work, cylindrical and planar Fourier near-field acoustical holography are used to investigate radiation from a full-scale, installed jet engine. Practical problems involving measurement aperture and the highly directional nature of the source are addressed. Insights from numerical simulations reveal usable reconstruction regions. A comparison of cylindrical and planar NAH for the respective measurement apertures shows cylindrical NAH outperforms planar NAH on reconstructions both towards and away from the source.

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Analog Feedback Control Of Broadband Fan Noise, Cole Victor Duke

Theses and Dissertations

Active noise control (ANC) has been implemented using analog filters to reduce broadband noise from a small axial cooling fan. Previous work successfully attenuated narrow-band, tonal portions of the noise using a digital controller. The practical performance limits of this system were reached and it was desirable to attenuate the noise further. Additional research, therefore, sought to attenuate broadband noise from the fan using a digital controller, but performance was limited by the group delay inherent in the digital signal processor (DSP). Current research attempts to further attenuate broadband noise and improve performance of the system by combining the tonal …

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Active Noise Control Of A Centrifugal Fan Mounted In A Mock Laptop Enclosure, John J. Esplin

Theses and Dissertations

Noise from information technology (IT) equipment is a significant problem in today's modern society. Active Noise Control (ANC) has shown promise in reducing the effect of IT fan noise on users. Though ANC has been applied to axial fans (such as those found in desktop computers), it has not been applied to centrifugal fans, such as those found in laptop computers. This work applies an ANC method to a centrifugal fan mounted in a mock laptop enclosure. This method is applied in four steps. First, secondary sources are placed in the vicinity of the fan. Second, an accurate model of …

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Electron Microscopy Characterization Of Vanadium Dioxide Thin Films And Nanoparticles, Felipe Rivera

Theses and Dissertations

Vanadium dioxide (VO_2) is a material of particular interest due to its exhibited metal to insulator phase transition at 68°C that is accompanied by an abrupt and significant change in its electronic and optical properties. Since this material can exhibit a reversible drop in resistivity of up to five orders of magnitude and a reversible drop in infrared optical transmission of up to 80%, this material holds promise in several technological applications. Solid phase crystallization of VO_2 thin films was obtained by a post-deposition annealing process of a VO_{x,x approx 2} amorphous film sputtered on an amorphous silicon dioxide (SiO_2) …

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Measurement Of Plasma Density In A Gas-Filled Ionizing Laser Focus, Nathan Edward Heilmann

Theses and Dissertations

We use an interferometric method for measuring the plasma density in a laser-induced plasma as a function of time. Any changes in the density within 5 ns of generation is due plasma expansion and not recombination. The analytic solution for plasma expansion derived for ultracold Neutral Plasmas describes the expansion of our laser produced Neon plasma of densities up to approximately 40 Torr. A model for the utlracold neutral plasmas, in comparison with measurements of our plasmas, can be used to extract an electron temperature. Currently our plasmas have shown to have an electron temperature of approximately 44 eV.

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Ground-State Characterizations Of Systems Predicted To Exhibit L11 Or L13 Crystal Structures, Lance J. Nelson, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Despite their geometric simplicity, the crystal structures L11 (CuPt) and L13 (CdPt3) do not appear as ground states experimentally, except in Cu-Pt. We investigate the possibility that these phases are ground states in other binary intermetallic systems, but overlooked experimentally. Via the synergy between high-throughput and cluster-expansion computational methods, we conduct a thorough search for systems that may exhibit these phases and calculate order-disorder transition temperatures when they are predicted. High-throughput calculations predict L11 ground states in the systems Ag-Pd, Ag-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt and L13 ground states in the systems Cd-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt. Cluster expansions confirm …

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Stable Ordered Structures Of Binary Technetium Alloys From First Principles, Gus L. W. Hart, Ohad Levy, Junkai Xue, Shidong Wang, Stefano Curtarolo

Faculty Publications

Technetium, element 43, is the only radioactive transition metal. It occurs naturally on earth in only trace amounts. Experimental investigation of its possible compounds is thus inherently difficult and limited. Half of the Tc-transition-metal systems (14 out of 28) are reported to be phase separating or lack experimental data. Using high-throughput first-principles calculations, we present a comprehensive investigation of the binary alloys of technetium with the transition metals. The calculations predict stable, ordered structures in nine of these 14 binary systems. They also predict additional compounds in all nine known compound-forming systems and in two of the five systems reported …

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Ordered Phases In Ruthenium Binary Alloys From High-Throughput First-Principles Calculations, Gus L. W. Hart, Lance J. Nelson, Michal Jahnátek, Ohad Levy, Roman V. Chepulskii, J. Xue, Stephano Curtarolo

Faculty Publications

Despite the increasing importance of ruthenium in numerous technological applications, e.g., catalysis and electronic devices, experimental and computational data on its binary alloys are sparse. In particular, data are scant on those binary systems believed to be phase-separating. We performed a comprehensive study of ruthenium binary systems with the 28 transition metals, using high-throughput first-principles calculations. These computations predict novel unsuspected compounds in 7 of the 16 binary systems previously believed to be phase-separating and in two of the three systems reported with only a high-temperature σ phase. They also predict a few unreported compounds in five additional systems and …

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Full-Text Articles in Astrophysics and Astronomy

Semiclassical Quantization: Corrections And Causes, Teresa Griffin

Journal of Undergraduate Research

Work Towards Building An Extreme Ultraviolet Ellipsometer, Cort N. Johnson, Dr. David D. Allred

Journal of Undergraduate Research

Determining Optical Constants With An Euv Polarimeter, Fabian Walter, Dr. R. Steven Turley

Journal of Undergraduate Research

Characteristics Of An Infrared, Slitless, Spectroscopic, Emission-Line Galaxy Survey, Jacob Peter Fugal, Dr. J. Ward Moody

Journal of Undergraduate Research

Variability In Quasars, Catherine Morris, Dr. Eric Hintz

Journal of Undergraduate Research

Constructing The Remote Observatory For Variable Object Research, Jason A. Gilbert, Dr. J. Ward Moody

Journal of Undergraduate Research

Development And Validation Of An Automated Directivity Acquisition System Used In The Acquisition, Processing, And Presentation Of The Acoustic Far-Field Directivity Of Musical Instruments In An Anechoic Space, Nicholas J. Eyring

Theses and Dissertations

Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein

Theses and Dissertations

Characterization Of Ingaas Quantum Dot Chains, Tyler Drue Park

Theses and Dissertations

Simulation Of 810 Nm Light Propagation Through The Human Finger For Non-Invasive Blood Analysis, Nichole Millward Maughan

Theses and Dissertations

Cluster Expansion Models Via Bayesian Compressive Sensing, Lance Jacob Nelson

Theses and Dissertations

Experimental Analysis Of Energy-Based Acoustic Arrays For Measurement Of Rocket Noise Fields, Jarom Henry Giraud

Theses and Dissertations

Investigation Of Low-Stress Silicon Nitride As A Replacement Material For Beryllium X-Ray Windows, David B. Brough

Theses and Dissertations

Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey

Theses and Dissertations

Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson

Theses and Dissertations

Modeling Radial Bernstein Modes In A Finite-Length Axisymmetric Non-Neutral Plasma, Mark Andrew Hutchison

Theses and Dissertations

Advanced Numerical Methods In General Relativistic Magnetohydrodynamics, Michael J. Besselman

Theses and Dissertations

Researching Effective Methods For Teaching The Phases Of The Moon, Heather Patti Jones

Theses and Dissertations

Long-Lived Electron Spins In A Modulation Doped (100) Gaas Quantum Well, John S. Colton, D. Meyer, K Clark, D. Craft, J. Cutler, T. Park, P. White

Faculty Publications

Nanoscale Surface Patterning And Applications: Using Top-Down Patterning Methods To Aid Bottom-Up Fabrication, Anthony Craig Pearson

Theses and Dissertations

Curious Growth Of A Buried Sio2 Layer, Thomas O. Mcconkie

Theses and Dissertations

Quantum Dynamics Using Lie Algebras, With Explorations In The Chaotic Behavior Of Oscillators, Ryan Thomas Sayer

Theses and Dissertations

Array-Based Characterization Of Military Jet Aircraft Noise, David William Krueger

Theses and Dissertations

Analog Feedback Control Of Broadband Fan Noise, Cole Victor Duke

Theses and Dissertations

Active Noise Control Of A Centrifugal Fan Mounted In A Mock Laptop Enclosure, John J. Esplin

Theses and Dissertations

Electron Microscopy Characterization Of Vanadium Dioxide Thin Films And Nanoparticles, Felipe Rivera

Theses and Dissertations

Measurement Of Plasma Density In A Gas-Filled Ionizing Laser Focus, Nathan Edward Heilmann

Theses and Dissertations

Ground-State Characterizations Of Systems Predicted To Exhibit L11 Or L13 Crystal Structures, Lance J. Nelson, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Stable Ordered Structures Of Binary Technetium Alloys From First Principles, Gus L. W. Hart, Ohad Levy, Junkai Xue, Shidong Wang, Stefano Curtarolo

Faculty Publications

Ordered Phases In Ruthenium Binary Alloys From High-Throughput First-Principles Calculations, Gus L. W. Hart, Lance J. Nelson, Michal Jahnátek, Ohad Levy, Roman V. Chepulskii, J. Xue, Stephano Curtarolo

Faculty Publications