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Articles 1 - 30 of 125
Full-Text Articles in Physics
Electrical Conductivity Of The Aluminum Oxide Diffusion Barrier Following Catalytic Carbon Nanotube Growth, Berg Daniel Dodson
Electrical Conductivity Of The Aluminum Oxide Diffusion Barrier Following Catalytic Carbon Nanotube Growth, Berg Daniel Dodson
Theses and Dissertations
Carbon nanotube templated microfabrication (CNT-M) is a method that allows high-aspect ratio structures to be made for microelectromechanical systems (MEMS) devices. One concern when making monolithic electrical devices using CNT-M is that the aluminum oxide diffusion barrier will create too large of a resistance in the device. However, in developing CNT based MEMS devices, it has been observed that an electrical DC current is capable of transport from a conductive substrate, across the aluminum oxide, and through to the CNT structure grown on top of it. This thesis attempts to determine the mechanisms responsible for current being able to cross …
Mechanically Scanned Interference Pattern Structured Illumination Imaging, Jarom Silver Jackson
Mechanically Scanned Interference Pattern Structured Illumination Imaging, Jarom Silver Jackson
Theses and Dissertations
A method of lensless, single pixel imaging is presented. This method, referred to as MAS-IPSII, is theoretically capable of resolutions as small as one quarter of the wavelength of the imaging light. The resolution is not limited by the aperture of any optic, making high resolutions (including subwavelength) feasible even at very large (greater than a meter) distances. Imaging requires only flat optics and a coherent source, making it a good candidate for imaging with extreme wavelengths in the UV and x-ray regimes. The method is demonstrated by the imaging of various test targets. Both real and complex imaging (i.e. …
Analytical Expressions For Acoustic Radiation Modes Of Simple Curved Structures, Caleb Burley Goates
Analytical Expressions For Acoustic Radiation Modes Of Simple Curved Structures, Caleb Burley Goates
Theses and Dissertations
The search for a convenient connection between vibration patterns on a structure and the sound radiated from that structure is ongoing in structural acoustics literature. Common techniques are wavenumber domain methods, or representation of the vibration in terms of some basis, such as structural modes or elementary radiators, and calculating the sound radiation in terms of the basis. Most choices for a basis in this situation exhibit strong coupling between the basis functions, but there is one choice which does not: Acoustic radiation modes are by definition the basis that orthogonalizes the radiation operator, meaning the radiation modes do not …
Noise Control Of Vacuum-Assisted Toilets, Michael Thomas Rose
Noise Control Of Vacuum-Assisted Toilets, Michael Thomas Rose
Theses and Dissertations
Vacuum-assisted toilets make use of a large pressure difference between the ambient pressure and a vacuum tank to transport waste from the toilet bowl to the septic tank. This process requires 98% less water per flush making it an attractive product for transport vehicles such as airplanes, cruise ships, and trains. Unfortunately, the water savings come at the cost of high noise levels. This thesis investigates the acoustic characteristics of a vacuum-assisted toilet flush and several methods to reduce the radiated noise. Some methods include changing rinse parameters such as rinse pressure, rinse length, and rinse timing, adding structural damping …
Using Symmetry To Accelerate Materials Discovery, Wiley Spencer Morgan
Using Symmetry To Accelerate Materials Discovery, Wiley Spencer Morgan
Theses and Dissertations
Computational methods are commonly used by materials scientists to make predictions about materials. These methods can achieve in hours what would take days or weeks to accomplish in a lab. However, there are limits to what computational methods can do and how accurate the predictions are.A limiting factor for computational materials science is the size of the search space. The space of potential materials is infinite. Selecting specific systems of elements on a fixed lattice to study reduces the number of possible arrangements of atoms in the lattice to a finite number. However, this number can still be very large. …
Penetration Depth Variation In Atomic Layer Deposition On Multiwalled Carbon Nanotube Forests, David Alan Kane
Penetration Depth Variation In Atomic Layer Deposition On Multiwalled Carbon Nanotube Forests, David Alan Kane
Theses and Dissertations
Atomic Layer Deposition (ALD) of Al2O3 on tall multiwalled carbon nanotube forests shows concentration variation with the depth in the form of discrete steps. While ALD is capable of extremely conformal deposition in high aspect ratio structures, decreasing penetration depth has been observed over multiple thermal ALD cycles on 1.3 mm tall multiwalled carbon nanotube forests. SEM imaging with Energy Dispersive X-ray Spectroscopy elemental analysis shows steps of decreasing intensity corresponding to decreasing concentrations of Al2O3. A study of these steps suggests that they are produced by a combination of diffusion limited delivery of precursors with increasing precursor adsorption site …
Implementation And Optimization Of Time Reversal For Use In Nondestructive Evaluation Of Stress Corrosion Cracking, Sarah Marie Young
Implementation And Optimization Of Time Reversal For Use In Nondestructive Evaluation Of Stress Corrosion Cracking, Sarah Marie Young
Theses and Dissertations
The time reversal (TR) process manipulates a system's impulse response in order to focus a peak of acoustic energy at a specific location in space and time. This technique has been implemented in both fluid and solid media for purposes ranging from communications to source localization. This thesis will examine both the implementation and processing of TR for nondestructive evaluation in steel, specializing in nonlinear detection methods. A series of steel samples are inspected for stress corrosion cracking (SCC) using TR focusing to excite nonlinearities inherent in cracks. It is determined that SCC exists in the expected regions of the …
Time-Domain Characterization Of Nonlinear Propagation In Military Aircraft Jet Noise, Brent Owen Reichman
Time-Domain Characterization Of Nonlinear Propagation In Military Aircraft Jet Noise, Brent Owen Reichman
Theses and Dissertations
Nonlinear propagation and shock formation are shown in noise radiated from full-scale military jet aircraft. Perception of sound is not only affected by the overall sound pressure level of the noise, but also characteristics of the sound itself. In the case of jet noise, acoustic shocks within the waveforms result in a characteristic commonly referred to as"crackle." The origin of shocks in the far-field of jet noise is shown to be through nonlinear propagation. Metrics characterizing the shock content of a waveform are explained and given physical significance, then applied to jet noise at various distances and engine conditions to …
Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack
Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack
Theses and Dissertations
Using a finite element method, we numerically solve the time-dependent Ginzburg-Landau equations of superconductivity to explore vortex nucleation in type II superconductors. We consider a cylindrical geometry and simulate the transition from a superconducting state to a mixed state. Using saddle-node bifurcation theory we evaluate the superheating field for a cylinder. We explore how surface roughness and thermal fluctuations influence vortex nucleation. This allows us to simulate material inhomogeneities that may lead to instabilities in superconducting resonant frequency cavities used in particle accelerators.
Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack
Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack
Theses and Dissertations
Using a finite element method, we numerically solve the time-dependent Ginzburg-Landau equations of superconductivity to explore vortex nucleation in type II superconductors. We consider a cylindrical geometry and simulate the transition from a superconducting state to a mixed state. Using saddle-node bifurcation theory we evaluate the superheating field for a cylinder. We explore how surface roughness and thermal fluctuations influence vortex nucleation. This allows us to simulate material inhomogeneities that may lead to instabilities in superconducting resonant frequency cavities used in particle accelerators.
Characterization Of Military Aircraft Jet Noise Using Wavepacket Analysis And Other Array Processing Methods, Blaine M. Harker
Characterization Of Military Aircraft Jet Noise Using Wavepacket Analysis And Other Array Processing Methods, Blaine M. Harker
Theses and Dissertations
Sound generation and radiation properties are studied of full-scale tactical jet engine noise. This is motivated by the high sound exposure levels from jet noise, particularly for tactical engines. Acoustic source reconstruction methods are implemented computationally on existing jet noise data. A comparative study is performed using numerical simulations to understand the capabilities of more advanced beamforming methods to successfully estimate the source properties of a distributed, partially correlated source distribution. The properties and limitations of each beamforming method are described. Having validated the methods, beamforming with regularization”via the Hybrid Method”is implemented on linear array measurements near an installed tactical …
Characterization Of Military Aircraft Jet Noise Using Wavepacket Analysis And Other Array Processing Methods, Blaine M. Harker
Characterization Of Military Aircraft Jet Noise Using Wavepacket Analysis And Other Array Processing Methods, Blaine M. Harker
Theses and Dissertations
Sound generation and radiation properties are studied of full-scale tactical jet engine noise. This is motivated by the high sound exposure levels from jet noise, particularly for tactical engines. Acoustic source reconstruction methods are implemented computationally on existing jet noise data. A comparative study is performed using numerical simulations to understand the capabilities of more advanced beamforming methods to successfully estimate the source properties of a distributed, partially correlated source distribution. The properties and limitations of each beamforming method are described. Having validated the methods, beamforming with regularization—via the Hybrid Method—is implemented on linear array measurements near an installed tactical …
Modeling Of Acoustic Resonators And Resonator Systems For Use In Passive Noise Control, Matthew Franklin Calton
Modeling Of Acoustic Resonators And Resonator Systems For Use In Passive Noise Control, Matthew Franklin Calton
Theses and Dissertations
Acoustic resonators, such as the Helmholtz and quarter-wave resonator, can be used to attenuate unwanted noise in an enclosed space. Classical formulations can be used to approximate resonator performance for a given resonator configuration, but may lack sufficient accuracy for some applications. This research aims to improve the analytical characterization of resonators to provide better correlation to experimental results. Using higher-order approximations and proper end corrections, more accuracy can be obtained in calculating the impedance and resonance frequency of a single resonator, which will then carry over into the overall configuration of the model. The impedance of a system of …
Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen
Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen
Theses and Dissertations
The two-point in situ method is a technique for measuring the room constant of a semi-reverberant room and the sound power of a source in that room simultaneously using two measurement positions. Using a reference directivity source, where the directivity factor along any given axis of the source has been measured, one is able to use the Hopkins-Stryker equation to measure both the room constant and the sound power level of another source rather simply. Using both numerical and experimental data, it was found that by using generalized energy density (GED) as a measurement quantity, the results were more accurate …
Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon
Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon
Theses and Dissertations
A high-resolution directivity measurement system at Brigham Young University has been renovated and upgraded. Acoustical treatments have been installed on the microphone array, professional-grade audio hardware and cabling have been utilized, and user-friendly MATLAB processing and plotting codes have been developed. The directivities of 16 played musical instruments and several loudspeakers have been measured by the system, processed, and plotted. Using loudspeakers as simulated musicians, a comprehensive analysis was completed to validate the system and understand its error bounds. A comparison and evaluation of repeated-capture to single-capture spherical systems was made to demonstrate the high level of detail provided by …
Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald
Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald
Theses and Dissertations
This work reports on the construction of a 408 nm laser system designed to drive stimulated Raman transitions between the F = 4 and F = 5 2 S 1/2 states of 87 Sr + using the 2 P 3/2 state as the intermediate state. This laser system will be used as part of a 87 Sr + ion interferometer. This work also includes a discussion of relevant theory describing the interaction of the ions and laser, along with a calculation of the transition rates as a function of laser power and detuning.
Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson
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 inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation …
Vector Intensity And Holography-Based Acoustic Source Characterization Of A Military Jet Aircraft, Trevor Alden Stout
Vector Intensity And Holography-Based Acoustic Source Characterization Of A Military Jet Aircraft, Trevor Alden Stout
Theses and Dissertations
The scientific community has employed multiple methods to analyze and describe the jet noise emanating from the turbulent exhaust flow from modern military aircraft engines, with the goal that better characterization of the sound radiation will improve noise reduction efforts. This thesis utilizes three different approaches to characterize the noise source region from a static F-22A Raptor. First, the energy flow field along planes near the aircraft and along an arc is measured using a multidimensional vector intensity probe. The resulting vector intensity maps give a clear indication of the directionality of the noise as a function of frequency at …
A Feasibility Study Of Photometric Reverberation Mapping With Meter-Class Telescopes, Carla June Carroll
A Feasibility Study Of Photometric Reverberation Mapping With Meter-Class Telescopes, Carla June Carroll
Theses and Dissertations
For the past several decades, mass estimates for supermassive black holes hosted by active galactic nuclei (AGN) have been made with the reverberation mapping (RM) technique. This methodology has produced consistent results and has been used to establish several relations that link the characteristics of the host galaxy to the mass of the central black hole. Despite this success, there are less than 50 AGN with black hole masses derived from RM. This low number is generally attributed to the difficulties in coordinating large blocks of telescope time for making simultaneous photometric and spectroscopic observations. Spectroscopic observations also generally require …
Characterization Of Order-Disorder Phase Transition Temperature For Select Nanoparticles, Gregory J. Sutherland
Characterization Of Order-Disorder Phase Transition Temperature For Select Nanoparticles, Gregory J. Sutherland
Theses and Dissertations
A method was found for creating ordered nanoparticles whose size and theoretical order-disorder temperature are ideal for study in the TEM. Specifically FePt, NiPt, FeNiPt and AuCu nanoparticles were studied. We were able to show how a nanoparticle's size affects its order-disorder temperature (Tod). When the particles were around 6 nm in diameter there was a shift downward of the Tod of 10-15 percent compared to the bulk. While particles around 10 nm in diameter experienced a downward shift of 0-6 percent compared to the bulk. One can approximate that particles less than 10-15 nm in diameter would show significant …
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 …
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 …
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 …
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) …
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 …
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 …
Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein
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 …