Thesis/Capstone Archive

Year:
Advisor:
Keir Ashby (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Discovering and understanding the properties of exoplanets, or planets orbiting other stars, is one of the great scientific quests of the 21st century. Since launching in 2009, NASA’s Kepler space telescope has returned measurements for 200,000 stars along with the exoplanet candidates orbiting them. To correct for Kepler’s bias against small and/or long-period planets, we are developing an advanced computer model capable of inferring the true underlying architectures of exoplanetary systems. This Exoplanetary System Simulator, “SysSim”, generates simulated catalogs of exoplanet systems and uses Approximate Bayesian Computation over several generations to produce several estimations of the actual exoplanet population. I have produced a flowchart to help users navigate the complex code structures of SysSim. To improve the accuracy of our MES (Multiple Event Statistic) calculations, I wrote and integrated code to interpolate MES values for individual exoplanets. I have produced several plots to analyze and interpret the results of SysSim. These figures revealed that SysSim works well in determining a good estimate for exoplanet occurrence rates but we also found that individual bins have “leaking” Simulated Observed planets and that the Simulated Observed Catalog and Kepler Catalog are significantly out of balance with each other. Further work will be undergone to examine and correct these problems.

Tyler Averett (Capstone, June 2018, Advisor: )

Abstract

It is difficult to optimize communications systems when they must work in a variety of environments. Such is the challenge presented by the Mars Society each year during the international University Rover Challenge. This report describes the journey taken by the communications sub-team of the 2018 BYU Mars Rover Team in order to build a reliable communications system capable of communicating between a stationary base station and a moving rover both in and out of line-of-sight. First, we took time to analyze and understand the competition rules, ensuring that our design would meet all the necessary specifications. Then we considered how the design would affect other sub-teams. Then, we decided on a communications plan and purchased antenna hardware in order to implement it. We soon modified this plan to use only two 900 MHz antennae. In the last stage of development, we created a rotating antenna mount. We tested our design at several intermediate points and finally at the University Rover Challenge held May 30¬–June 2.

Tyler Bahr (Senior Thesis, April 2018, Advisor: Mark Transtrum )

Abstract

In 1952 Hodgkin and Huxley formulated the fundamental biophysical model of how neurons integrate input and fire electric spikes. With 25 parameters and 4 dynamical variables, the model is quite complex. Using information theory, we analyze the model complexity and demonstrate that it is unnecessarily complex for many neural modeling tasks. Using the manifold boundary approximation method of model reduction, we perform a series of parameter reductions on the original 25-parameter model and create a series of spiking Hodgin-Huxley models, each with decreasing parameter number. We analyze the physical meaning of some key approximations uncovered by our systematic reduction methods, which are "blind" to the real physical processes the model is intended to capture. We then evaluate the behavior of the most greatly reduced 14-parameter model under different experimental conditions, including networks of neurons. We also discuss new questions that have arisen as a result of our work

Sterling Baird (Senior Thesis, September 2018, Advisor: Robert Davis )

Abstract

The high theoretical gravimetric energy density (Wh/kg) of lithium-sulfur batteries holds promise for battery applications such as UAVs, electric vehicles, and military applications. Here, we report the use of a carbon nanotube based interfacial layer in conjunction with highly scalable sulfur cathodes using the doctor-blade coating technique for high capacity, highly coulombic efficient lithium-sulfur batteries. The interfacial layer consists of vertically-aligned multi-walled carbon nanotubes and a conductive nonporous layer which aids in polysulfide trapping. We observe a high initial discharge capacity of 930 mAh/g-S and high coulombic efficiencies above 93% without the use of gas-forming additives such as lithium nitrate. Ratio effects between sulfur, electrolyte, and lithium reveal correlations to lower capacity with higher sulfur loading, higher capacity with stronger electrolyte to sulfur ratios, and increased cycle life with greater lithium overcapacity. Overcharge experiments reveal that a 15% overcharge cut-off provides reasonable efficiency (~87%), and cycle life. Addition of 1% selenium to the cathode composition increased discharge voltages, but slightly decreased capacity and did not have a discernable effect on rate capability at 1C. Addition of PEO/LiTFSI/HNT binder stabilized cycling, but decreased capacity in some instances. Enhanced diffusion pathways and electrolytic contact had a positive correlation with capacity, suggesting that micro-patterned carbon nanotube architectures may play a unique role in lithium-sulfur batteries.

Jonathan Bassett (Senior Thesis, April 2018, Advisor: David Neilsen )

Abstract

We study the effects of spinning bodies on the chaotic properties of the three-body problem in general relativity. We use the post-Newtonian Hamiltonian to order 2 with the leading-order spin-orbit Hamiltonian. We study a system composed of a binary star system in a circular orbit and an incoming star. We generalize previous work by adding spin to each of the objects. The parameter space includes both regions with predictable behavior and regions with chaotic behavior, but the spin of the stars does not significantly alter the size of chaotic regions. Spin does not appear to have a significant effect on chaos in the relativistic three-body problem for this system.

William Black (Senior Thesis, April 2018, Advisor: David Neilsen )

Abstract

Supermassive black holes (SMBHs) are orphans—since no known progenitors exist, their origins are mysterious. They are so massive that even if the first stars collapsed into black holes, they would struggle to even come close to supermassive sizes. I investigate whether primordial black holes (PBHs), formed by overdensities in the Big Bang, could be the progenitors of SMBH. I use the cosmology code Enzo to simulate the growth of single solar mass PBHs over the course of ~325 Myr to see if the PBHs can reach supermassive sizes. Additionally, I compare Bondi accretion to viscous accretion. I use two methods to test whether PBHs could grow fast enough to become SMBHs. First: comparison to the growth of their surrounding halos—if a PBH is roughly 10^3 M⊙ by the time its halo is 10^8 M⊙, PBH–SMBH evolution is possible. Second: comparison to observed early SMBHs. If our PBHs reach similar sizes by similar times, PBH–SMBH evolution could be a viable pathway for those early observed SMBHs. Aside from the main results, I discovered that Bondi accretion and viscous accretion result in drastically different accretion rates. While black holes growing with Bondi accretion grew on order 10^-4, black holes with viscous accretion grew on order 10^+4. This is likely due to the dependence of Bondi accretion on simulation resolution. Given sufficiently dense seeding points, I found that the growth of PBHs does match the growth needed to reach supermassive sizes. The PBHs reached 10^3 M⊙ by the time their halos were 10^8 M⊙, so they do have the potential to reach the sizes of many observed SMBHs. Their extrapolated growth barely fell short of observed early SMBHs, but if 10–100 M⊙ PBHs were seeded, their growth trajectory would be on track to reach the sizes of early SMBHs.

Clint Carlson (Capstone, August 2018, Advisor: )

Abstract

Communication with devices in the Ku-band region, 12-14 GHz, has become paramount in applications such as UAVs, spacecraft, and satellites. Cost, size, and weight have become an increasing issue with these types of communication devices, as such, traditional mechanical antenna have become obsolete and different methods are being approached to solve this problem. A phased array receiver is the method that this research proposes to use to remedy the shortcomings of traditional antennas. A phased array system that is smaller, lighter, and more cost effective than a traditional antenna can be implemented through the use of a CMOS phase shifter. The desired result of this research is to implement a phased shifter with a 360° phase shift that operates in the Ku-band region with an amplitude magnification of 15dB. 3 prototypes of the specified phase shifter have been made, but they all have fallen short of the necessary specifications. In order to prevent failure in the next prototype extensive testing must be done on the previous prototypes to identify the cause for errors. In depth simulations must also be done after the design of the fourth prototype is complete, to ensure the correct operation of this device before production.

Michael Carlson (Senior Thesis, April 2018, Advisor: Ross Spencer )

Abstract

The shock structure near the skimmer cone of the plasma/vacuum interface of an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) is computationally modeled using a Direct Simulation Monte Carlo (DSMC) code, FENIX. These shocks are caused by a hypersonic, rarefied gas flow hitting a metal surface. To determine the most accurate simulation of the shocks, three different gas--surface interaction models are tested against existing experimental data. The three interaction models used in this study are the specular, thermal and Cercignani-Lampis-Lord (CLL) models. The specular and thermal models are simpler to implement, but do not result in the correct shock structure. Namely, the specular model conserves too much energy in the reflected particles and does not scatter the particles enough. The thermal model does not conserve enough energy and scatters particles too much. The CLL model requires more time to set up, but results in a more accurate representation of the shock. This additional set up time comes from accommodation coefficients in the CLL model that can be set to approximately represent any surface, with its accompanying roughness and temperature. To find these accommodation coefficients, the simulated shocks need to be matched with experimental data. We found that the specular gas--surface interaction model gave the most accurate shock structure.

Joseph Chandler (Senior Thesis, April 2018, Advisor: Ross Spencer )

Abstract

Between the skimmer cone and the mass analyzer of an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) lies an electrostatic ion lens. The lens uses a large negative potential to remove the electrons from the plasma and to collimate the ions forming a plasma sheath. By using Boltzmann electrons and collisionless ions to computationally model this interaction, we can calculate the electrostatic potential and ion density near the skimmer cone. Doing this calculation on a cylindrically symmetric grid gives a version of Poisson's equation, which is a second order nonlinear partial differential equation that we try to solve using a successive overrelaxation technique. In this plasma sheath calculation, no pre-sheath is required due to the supersonic velocities of the ions. By calculating the position of the plasma sheath based on different initial conditions we are developing an understanding of how and where this sheath forms in both one and two dimensions.

Mitchell Clingo (Capstone, May 2018, Advisor: Grant Hart )

Abstract

Non-neutral plasma in a Malmberg-Penning trap has been shown computationally to exhibit nonlinear mode coupling between Trivelpiece-Gould modes. We used a computational model that shows similar mode coupling between the nz=1 and nz=2 modes. This occurs because of the nonlinear terms found in the momentum and the continuity equations. By driving both modes, we can get large enough magnitudes to see the coupling. If the magnitude of either mode is not large enough, coupling factors become insignificant. Also, a relation exists between the relative phase difference between modes and the direction of energy transfer in coupling.

Scott Crossen (Senior Thesis, April 2018, Advisor: John Colton )

Abstract

Electron spin resonance (ESR) is an important tool in understanding the quantum-mechanical properties of condensed matter. Its applications range from studying lattice defects in solids to studying spin coherence in qubit candidate materials used for quantum computing. When coupled with a photoluminescence measuring component, it is possible to optically record ESR information contained in the resulting induced light. This unique form of ESR is called optically detected magnetic resonance (ODMR). In this thesis we compare experimental ODMR data with ESR predictions generated from a computational modeling system. To investigate the differences between these two methods we will study one spin-system in particular: irradiated 4H silicon carbide. This specimen will serve as the primary means to connect the two very different forms of computational and practical ESR spectroscopy commonly used today. Methods and theory for both methods will be described and resulting spectra will be presented for comparison. Though there will always be some differences, results show that computational ESR predictions match experimental results to the same extent that the underlying Hamiltonian for that particular system is understood.

Michael Hunter Denison (Masters Thesis, August 2018, Advisor: Brian Anderson )

Abstract

[Abstract]

Adam Dodson (Senior Thesis, April 2018, Advisor: Scott Bergeson )

Abstract

Emission spectra from atoms with hyperfine structure typically show closely-spaced atomic transitions. This happens because the hyperfine interaction splits and shifts the fine-structure energy levels in both the ground and excited state by a small amount. In laser-induced fluorescence measurements, the atoms are driven into a superposition of excited hyperfine states which then decay into a range of ground hyperfine states. Interference in different quantum pathways for this process influences the probability of excitation. Unless this is properly accounted for, this interference effect systematically shifts the apparent center of the fluorescence lineshape. We report measurements of this quantum interference (QI) effect in Yb-171 and Yb-173 and show that QI shifts the line centers by up to 5 MHz. We extend and verify a published QI model for Yb-171. We show that optical pumping complicates a straightfoward application of the model to the experiment for Yb-173. We then demonstrate that optical pumping-induced variations in the distribution of magnetic sub-levels in the hyperfine structure are insufficient to explain observed shifts in Yb-173.

Ryan Doel (Capstone, January 2018, Advisor: Bryan Peterson )

Abstract

A single-stage parallel wire ionic wind device was investigated in an effort to further elucidate thrust dependencies. An attempt to measure the strength of the relationship between the geometrical constant C and the ratio of the emitter and collector diameters, C proportional to de/dc, was undergone. Consequently a 1m long assembly was created wherein electrode gap distance, applied voltage, and diameter of emitter and collector wire were varied. We found that the collector size has a larger impact on thrust than emitter diameter. It was observed that the lengthened device reduced end effects witnessed by other researchers. The relationship C proportional to de/dc was never quantified due to the propagation of errors in our results. In an effort to reduce these errors, future research should acquire force measurements at 30+ different voltages for each configuration. Also, further studies should combine 4+ collector sizes and 4+ emitter sizes, in order to paint a broader picture of the force dependence on electrode size.

Carson Evans (Senior Thesis, April 2018, Advisor: Ross Spencer )

Abstract

The plasma torch of the Inductively Coupled Plasma Mass Spectrometer (ICP) is powered by a 3-turn coil attached to a radio-frequency generator running at 40 MHz. The discharge is started by a Tesla coil that briefly ionizes a small fraction of the argon gas flowing through the coil. After the initial ionization pulse, the RF field produces the electric field that gives the electrons enough energy to heat the argon gas. As the electrons gain energy from the RF field they reach an energy capable of either exciting or ionizing the argon atoms. We are modeling the effect of the RF field on the electrons as well as the effect of collisions between electrons with neutral, excited, and ionized argon and with other electrons. We are also including the possibility of de-excitation argon. Our goal is to see an electron avalanche, a chain reaction where electrons ionizing argon neutrals create more free electrons which in turn ionize more argon.

Trey Fanning (Capstone, August 2018, Advisor: )

Abstract

Purpose: To analyze the symmetry and adherence to the attempted end parameters of the lenticule formed during the Small Incision Lenticule Extraction (SMILE) procedure and create a 3D model of the lenticule using the MATLAB platform. Methods: Three human donor corneoscleral buttons were each mounted on an artificial anterior chamber maintainer and received the SMILE procedure. Immediately following treatment, these corneas underwent imaging on the Avanti OCT to obtain lenticule pachymetry data. The data was then extracted and exported into Microsoft Excel, as well as a program written in MATLAB that compiles and displays the data as a 3D model of the lenticule. Statistical analysis was performed in Microsoft Excel. Results: Attempted maximum lenticule thickness was 107 µm as reported by the VisuMax laser with a minimum thickness of 15 µm at 3.25 mm from the center. Post-treatment lenticule data showed an average central lenticule thickness of 117.24 µm, a minimum central thickness of 99 µm and a maximum central thickness of 128 µm. Lenticule thickness, when measured at the same radial distance within the same meridian varied by 9 µm on average and had an average standard deviation of 6.936 µm. Conclusions: Lenticules formed during a SMILE procedure to treat a -6D refractive error using the VisuMax femtosecond laser were shown to be radially symmetric within 9 µm, having an average standard deviation of all points measured at each radial distance of 6.936 µm. The symmetry of the lenticule formed during the SMILE procedure shows that small incision lenticule extraction is an effective treatment for those eyes without astigmatism. However, the measured post-treatment lenticule data showing the lenticule to be 10 µm thicker than the attempted lenticule thickness necessitates special consideration to be taken when treating an eye that presents with thinner than ideal pachymetry data. Due to the symmetric nature of the lenticule, it may be a viable option for the correction of high hyperopia without astigmatism by implanting it in a created pocket or under a flap.

Trent Furlong (Senior Thesis, June 2018, Advisor: Brian Anderson )

Abstract

Time reversal (TR) acoustics is capable of remotely focusing sound energy to a point in space. This thesis explores the remote delivery of a noise-canceling signal to a desired location (e.g. a patient’s ears) using TR. A parameterization study testing frequency dependence, and signal length is conducted in a reverberation chamber to determine the effectiveness of using TR with active noise control (ANC). The reduction of Magnetic Resonance Imaging (MRI) noise using ANC delivered by TR (ANC+TR) is demonstrated using recordings of MRI noise. For both the parameterization study and the MRI noise experiments, the simulated noise and ANC+TR signals are broadcast from two separate sources, recorded by a microphone, and their responses are linearly superposed in post-processing to determine the noise attenuation. The parameterization study results show that TR is better at reducing noise at frequencies below 1 kHz and for narrowband signals with reductions as great as 20 dB. MRI noise is reduced by up to 18 dB in overall sound pressure level. Both the parameterization study and the MRI noise reduction study utilized a single control loudspeaker; further reductions should be possible with the use of more control sources.

Ryan Hatch (Senior Thesis, August 2018, Advisor: Eric Hirschmann )

Abstract

The full eigenvector decomposition for the flux Jacobian matrices of the equations of general relativistic magnetohydrodynamics (GRMHD) are found. The matter equations for GRMHD in the ideal limit can be written in a system of balance law equations. These equations can then be framed as a single 8$\times$8 matrix equation written in terms of the fluid and magnetic field variables. Obtaining the full decomposition allows for the implementation of sophisticated numerical techniques. In this paper we provide the right and left eigenvectors as well as the wave speeds for use in such numerical modeling.

Andy Hernandez (Senior Thesis, April 2018, Advisor: Eric Hintz )

Abstract

Magnitudes of stars are measured from the energy we measure (apparent) and the total energy output over the entire surface of the star (absolute). In this work we find apparent magnitudes for specified wavelengths of the double cluster h and χ Persei. Apparent magnitudes are attained using point spread function photometry, which is utilized in order to help separate closely spaced stars existing in the clusters. Color-color diagrams are shown detailing the physical properties of h and χ Persei. These are done using the Hα index, described herein, with the Hα magnitude. From these diagrams we can recreate a Hertzsprung-Russel diagram with the addition of Be type stars being easily identifiable. A second, unknown group is discussed. An analysis of the Hα index with the Hβ index shows how Hα emission continues beyond Hβ emission for emission type objects. Using this Hα Hβ index plot emission objects are easily identifiable.

Lauren Hindman (Senior Thesis, May 2018, Advisor: Joseph Moody )

Abstract

Blazars, a subclass of Active Galactic Nuclei (AGN), are characterized by a jet of particles accelerated by magnetic fields around supermassive black holes. For blazars, these jets are angled toward Earth. These objects are known to change magnitude, or flare, often and sometimes rapidly. It is thought that two mechalisms are mainly responsible for flaring: geometric instabilities in the jetswhichoccurstochastically,andperiodicchangesinjetoraccretiondiskactivityaddoriendation from orbital perturbations. Using our Remote Observatory for Variable Object Research (ROVOR), we monitored 192 of these objects using both V and R Johnson broadband spectral filters over the course of a year. We comment on the variability observed and which mechanism may be most responsible.

Heather Hogg (Senior Thesis, April 2018, Advisor: John Colton )

Abstract

Determining the relationship between temperature and photoluminescence lifetime is central to creating temperature probes for microfluidic devices and laser surgery. Rhodamine B, a highly photoluminescent organic dye, is a particularly good candidate for temperature probes. This thesis discusses the use of time-correlated single photon counting to determine photoluminescence lifetimes of rhodamine B at temperatures from 16 K to 296.5 K. The instrument response function is separated from the true photoluminescence lifetime data with deconvolution data analysis techniques. The relationship between temperature and photoluminescence lifetime for rhodamine B is shown to be most accurately represented by a sigmoidal function, with very little variation at low temperature ranges. It is concluded that the behavior of the lifetime follows theoretical quenching regions over different temperature ranges.

Stephen Hogg (Senior Thesis, June 2018, Advisor: Brian Anderson )

Abstract

Spent nuclear fuel rods are stored in stainless steel containers and may be stored for decades. In order prevent radiation leakage, the stainless steel structure must not be compromised. These containers are susceptible to stress corrosion cracking (SCC). Traditional nondestructive evaluation methods have been developed to detect open cracks but these cannot detect the closed portion of the crack that may extend further. Nonlinear Resonant Ultrasound Spectroscopy (NRUS) is used here to determine if it can be used to quantify a cumulative amount of SCC in a structure. To induce SCC in a timely manner, cylindrical, 304L stainless steel rods are immersed in a heated 42% magnesium chloride solution. A set of rods are removed one by one after different lengths of exposure to the hot magnesium chloride solution. NRUS measurements are then conducted on longitudinal modes in the rods. Rods exposed longer did indeed result in a larger resonance frequency shift, and therefore a larger nonlinear parameter, α, in NRUS measurements. It is observed that α can be used to detect SCC before visible cracks appear on the rods.

Tyler Hopkin (Capstone, April 2018, Advisor: Kent Gee )

Abstract

Acoustical room characterization typically involves a lot of high end and expensive equipment for measuring, modeling, and finding solutions to problems. Recently, Room EQ Wizard (REW) was introduced to BYU as a less costly option. This paper will evaluate REW's effectiveness through the metrics of mapping sound coverage, reverberation time and clarity calculations, while providing the Missionary Training Center with acoustical consulting for their auditorium. REW proved to be efficient and effective in all metrics and helped narrow the problem down to an unforeseen interaction between the loudspeakers and podium microphone.

Annie Laughlin (Senior Thesis, July 2018, Advisor: Robert Davis )

Abstract

Modern advancements in technological fields including electric vehicles and high powered laptops rely on battery storage. Lithium is useful in creating high capacity batteries because it has high energy density. However, when cycling a battery at a fast rate, the lithium becomes unstable due to the small amount of accessible energy on the surface of the lithium electrode. The solution to this problem is to increase the surface area of the lithium electrode through electrodeposition techniques onto a carbon scaffolding. This increases the current density limit. Electrodeposition is beneficial because the user can control how much lithium is deposited onto the substrate. This enables researchers to cycle high capacity batteries at an accelerated rate.

Kevin Robert Laughlin (Masters Thesis, August 2018, Advisor: Robert Davis )

Abstract

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Joseph Scott Lawrence (Masters Thesis, August 2018, Advisor: Kent Gee )

Abstract

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Stefan Lehnardt (Capstone, April 2018, Advisor: Robert Davis )

Abstract

Single-layer graphene consists of a single layer of sp2-bonded carbon atoms and exhibits many remarkable properties. It is the strongest material ever measured with a tensile strength of 90 GPa. As a single layer of atoms, however, single-layer graphene cannot cope with macroscopic forces and its applications are limited. Multi-layer graphene combines many layers of graphene and may be able to withstand forces that single-layer graphene cannot. To determine whether or not multi-layer graphene, (MLG) is suitable for a given application, it is important to know its mechanical properties and how they compare to those of single-layer graphene. This report focuses on the burst pressure of MLG membranes as grown on modified nickel substrates suspended over openings in silicon.

Steven Maggard (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Thousands of asteroid-like objects reside in the Kuiper Belt Region. For accurate dynamical classification, the precision of their orbits needs rigorously tested. Using an analysis pipeline we created, we generated 30 statistically-weighted orbital clones for over 2000 Kuiper Belt Objects(KBOs). These orbits are integrated backwards in time 50 Myr. We created a database from the propagated orbits, from which we calculated the proper orbital elements for each KBO. We used the method established by Ragozzine and Brown (2007) to determine each KBOs relation to the dwarf planet Haumea. Currently, we have more than tripled the number of Haumea Family Members established by Ragozzine and Brown (2007). We conclude that other collisional families can befound using similar methods applied to Haumea and the orbital database we created.

Brittni Newbold (Senior Thesis, April 2018, Advisor: Karine Chesnel )

Abstract

Magnetite nanoparticles have great potential for use in medical and other applications, so understanding their properties is crucial. A property still left to be understood is the magnetic ordering of assemblies of nanoparticles at the nanoscale. This paper addresses how the magnetic ordering in magnetite nanoparticle assemblies changes as a function of nanoparticle size and external magnetic field at high temperature. Nanoparticle assemblies were fabricated using organic methods and placed on membranes. These samples were put through x-ray resonant magnetic scattering (XRMS) which produced scattering images that provided information about the magnetic ordering of the particles. Various images were obtained using XRMS for different field values and temperatures. These images were reduced to one-dimensional scattering profiles. By fitting these scattering profiles with a model, we found the percentages of ferromagnetic contribution, antiferromagnetic contribution, and the random contribution. There is a large random contribution as the field value approaches 0 Oe for Sample 9, the sample with the smallest particles, at 300 K. For Sample 3, the sample with the largest particles, at 280 K and at 300 K, there is a slight increase in the antiferromagnetic contribution and large random contribution at low field value. The larger particles are thus demonstrating more antiferromagnetic ordering at low magnetic field values than the smaller particles when placed in high temperature. Therefore, our methods yield information about the magnetic ordering of magnetite nanoparticles and the possibility to control the magnetic ordering through particle size.

Felicity Nielson (Senior Thesis, April 2018, Advisor: Gus Hart )

Abstract

Steel is an incredibly valuable, versatile material. Unfortunately, high-strength steels are vulnerable to hydrogen embrittlement, a process that describes the degradation of a crystalline- structured material when too much hydrogen is absorbed. When enough hydrogen builds up, it can lead to early and unexpected failure of the material, which is both costly and dangerous. Recent decades have seen a surge of efforts to solve this problem, but a general, viable solution has yet to be found. In this paper, we continue a new method using machine learning techniques in conjunction with atomic environment representations to predict global properties based on local atomic positions. Steel is comprised mostly of the base element iron. The defects in the iron crystal structure are where hydrogen prefers to adsorb. By developing a technique that will allow us to understand the global properties in these areas, future research will lead to predicting where the hydrogen will adsorb so that we can find another element that will non-deleteriously adsorb to those same sites, thus blocking the hydrogen and preventing hydrogen embrittlement. This methodology can further be applied to any crystalline material, allowing engineers to understand the basic building blocks of what gives a material its properties. Its application will help improve the versatility of materials manufacturing, allowing manufacturers to precisely design a material with whatever properties a customer desires, enhance the properties of existing materials, and stabilize materials that so far only exist in theory.

Will Oldroyd (Senior Thesis, April 2018, Advisor: Darin Ragozzine )

Abstract

Meteorites with high specific gravities, such as irons, appear to be underrepresented in Antarctic collections over the last 40 years. This underrepresentation is in comparison with observed meteorite falls, which are believed to represent the actual population of meteorites striking Earth. Meteorites in the Antarctic ice sheet absorb solar flux, possibly leading to downward tunneling into the ice. This descent is counteracted by ice sheet flow supporting the meteorites coupled with ablation near mountain margins, which helps to force meteorites toward the surface. Meteorites that both absorb adequate thermal energy and have a high enough thermal conductivity may instead reach a shallow equilibrium depth as downward melting overcomes upward forces during the Antarctic summer. Using a pyranometer, the incoming solar flux was measured at multiple depths in two deep field sites in Antarctica, the Miller Range (2013-14) and Elephant Moraine (2016-17). Thermal and physical interactions between a variety of meteorites and their surroundings were modeled, incorporating constraints derived from the pyranometer data. We find that a typical iron meteorite traveling upward through the ice during the Antarctic summer reaches an equilibrium depth of approximately 30 cm beneath the surface. This is slightly less deep than previous estimations. The effect of snowfall on equilibrium depth in our model is minimal. The recovery of an additional population of heavy meteorites would increase our knowledge of the formation and composition of the solar system by further constraining the number of differentiated planetesimals forming in the early inner solar system.

Sean Pearce (Senior Thesis, April 2018, Advisor: Mike Joner )

Abstract

To better understand the effects of high metallicity on white dwarf cooling processes, especially the white dwarf cooling age, we have analyzed images of the metal-rich open cluster NGC 6253, from the 8 m Gemini-South Observatory. To standardize the Gemini photometry of the cluster, we have also secured imaging data of both the cluster and standard star fields using the 0.6 m SARA Observatory at Cerro Tololo Inter-American Observatory. By comparing the photometric magnitudes and colors of additional stars in standard star fields of both the SARA data and the published Gemini zero-points of the standard star fields, we calibrated the data obtained for the cluster. These calibrations are an important part of the project to obtain a standardized deep color magnitude diagram and white dwarf luminosity function to analyze the cluster. With the standardized color magnitude diagram, we determined the cluster’s main sequence turnoff age to be 4.6±0.2 Gyr., much older than the earlier results showing an age ∼ 3.6 Gyr. Because the cluster is much older than expected, the white dwarfs have cooled and dimmed beyond our limits of detection. Since we were unable to detect the coolest white dwarfs, we could not make a white dwarf luminosity function with the current data set.

J. Ryan Peterson (Senior Thesis, April 2018, Advisor: John Colton )

Abstract

Zinc oxide is a promising wide band gap semiconductor with applications in high-temperature, radiation-hard devices and ultraviolet optoelectronics. The p-type material, however, has historically been difficult to produce. In this work, p-type zinc oxide films are grown by rf magnetron sputtering on c-sapphire substrates. Arsenic doping is provided by a Zn3As2 intermediate layer. Electrical characterization shows that while the conductivity correlates strongly with substrate temperature while sputtering, carrier type is inconsistent for samples grown in similar conditions. Photoluminescence measurements reveal poor optical performance related to deep defects. These defects may explain the n-type conductivity and comparison with previous work suggests future improvements to the growth process.

Seth Price (Capstone, June 2018, Advisor: John Ellsworth )

Abstract

The design and construction of a Wien Velocity Filter to be used in the BYU Physics Department to help with thin film, and low energy nuclear reaction experiments. Designed as an attachment to the school’s 400KeV particle accelerator. Built specifically to filter Hydrogen and Deuterium ions from a high energy ion beam. Design properties of the Wien Filter are shown. The Characterization of ceramic magnets and their fields along with the electric fields are presented. The attachment and programming of a Tektronix programmable power supply and communication of commands through MATLAB.

Reese Rasband (Senior Thesis, August 2018, Advisor: Kent Gee )

Abstract

For a Marine in training, he or she will spend many hours on the firing range expending ammunition. This can cause lasting hearing damage for marines. Although previous weapons measurements have been done, the standards require further testing. To address this problem a team composed of members from Brigham Young University (BYU), Air Force Research Laboratory (AFRL), and the National Institute for Occupational Safety and Health (NIOSH) performed a test of M16A4 rifles measured at Quantico Marine Base in July 2017. In this thesis measurement techniques are presented for measuring rifle noise as well as data verification. A 113-microphone array was used to acquire the data with microphone heights selected to mirror shooters’ ear positions in the standing, kneeling, and prone configurations. It was found that peak levels (Lpk) exceeded 162 dB near the muzzle blast of the rifle, and within a 20 m radius Lpk exceeded 140 dB. These levels are known to cause hearing damage. Measurements clearly show specific events, such as the muzzle blast, sonic boom, and ground reflections, as well as effects of shielding. This thesis proposes that the quality of data acquisition promotes further use of the protocol employed here.

AJ Rasmusson (Senior Thesis, June 2018, Advisor: Jean-Francois Van Huele )

Abstract

Quantum measurement theory provides a relationship between measurement error and disturbance caused in observables due to measurement. This relationship describes the lower limit of error in quantum measurement. I expand current theory from two to three observables—two disturbances and one error—to better describe three dimensional properties (like spin). I create three quantum circuits, which together, represent error and two different disturbances in a spin-1/2 system. The quantum circuits are executed on IBM’s real and simulated quantum computers. Simulate data match the two-observable relation while real data progressively gets further from the relation as the data approaches the relational boundary. For the two-observable relation, the quantum circuits are accurate on simulated quantum computers suggesting the inaccuracy in the real IBM quantum computers is due to internal IBM quantum computer workings. For three-observables, simulated and real quantum computer data suggest the constructed relation is not tight and thus not capturing the correct lower limit boundary. Tightening the three-observable relation is needed.

Brent Owen Reichman (PhD Dissertation, August 2018, Advisor: Kent Gee )

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Jesse Richmond (Senior Thesis, April 2018, Advisor: David Allred )

Abstract

The Labeled Release experiment of the Viking landers led to the hypothesis that martian soil is highly oxidized. Hydrogen peroxide has been suggested as the primary oxidant, but no definitive theory exists as to how it forms in the martian environment. We propose that ultraviolet radiation interacts with carbon dioxide, water, and other trace substances in the martian atmosphere to form this hydrogen peroxide. We tested this theory by constucting a Mars-like atmosphere within a vacuum system and then exposing it to ultraviolet radiation from a UV lamp. The resulting products were then collected into a cold trap and analyzed by a mass spectrometer. Initial results do seem to indicate that hydrogen peroxide was generated by the interaction, as well as other substances. If correct, this data further expands our knowledge of the martian environment and explains why no martian organics have been discovered thus far.

Robert Tucker Sprenkle (Masters Thesis, August 2018, Advisor: Scott Bergeson )

Abstract

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Mark Hunter Standring (Capstone, August 2018, Advisor: )

Abstract

The characteristics of a stock electronic controller for a hobby-size engine were tested to in order to design and build an open source full authority digital engine controller (FADEC) using off-the-shelf parts. It was found that the sponsor-determined requirements for the new controller could be fulfilled by segmenting the design into the following subsystems: microcontroller, microcontroller software, user interface software, communication, and power driver circuit. The controller hardware was built using a rugged Arduino, a Mego Motor Shield, a customized wiring harness, a 65 ft USB cable to a PC computer, and an SK-19 NEMA 4X Waterproof Enclosure. The controller software was developed using Arduino code and a LabVIEW VI incorporating a PID controller element. The final product exhibited excellent contral of a JetCat P-100 jet turbine engine and was delivered to the sponsor by April 23rd, 2018.

David Van Komen (Senior Thesis, April 2018, Advisor: Traci Neilsen )

Abstract

An improved understanding of the sound generation of high-performance military aircraft is studied through beamforming. Conventional methods of beamforming, while powerful for localizing equivalent acoustics sources, are inadequate due to the complexities of jet noise. These complexities arise from the large, partially correlated source region, which violates the uncorrelated monopole assumption of conventional beamforming, and multiple types of noise sources, including directional and omnidirectional sources that vary with the aircraft’s operating power. These complexities require the utilization of advanced beamforming methods, such as the Hybrid Method and the Generalized Inverse method. The aim of this research is to apply advanced beamforming methods to the high-performance military aircraft jet noise to create frequency-dependent equivalent acoustic source distributions. These methods are applied to a ground-based array of 71 microphones that recorded noise from an F-35 aircraft. To investigate the multiple types of noise sources, the array is split into several subarrays that cover the sideline, maximum, and downstream regions of the noise. The advanced beamforming methods are applied to each of the subarrays at two different operating powers to investigate the different noise sources and how they change with operating powers. Subarray analysis on the F-35 engine noise yields equivalent sources for the different types of noise in overlapping regions.

Aaron Vaughn (Senior Thesis, April 2018, Advisor: Traci Neilsen )

Abstract

Jet noise has primarily been examined for laboratory-scale jets and only recently for full-scale jets. In this thesis, jet noise from a laboratory-scale Mach 1.8 jet and an F-35B high-performance military aircraft are observed and compared. Both contain turbulent mixing noise while only the full-scale jet contains broadband shock-associated noise (BBSAN). Previously developed empirical models for turbulent mixing noise were used to perform spectral decompositions. Similar angular trends for similarity spectra decompositions of the turbulent mixing noise exist across both sets of measurements. Full-scale BBSAN spatial trends are similar to laboratory-scale results from the literature for peak frequency but differ for peak level and spectral width. Similarity spectra decomposition is sufficient to match the spectra from the laboratory-scale jet while a three-way spectral decomposition including BBSAN is needed to fit the F-35B spectra. Discrepancies between fits and measured spectra exist for both jets at small inlet angles for high frequencies and at the region of maximum radiation for the F-35B. However, overall, the empirical models produce realistic representations of the measured spectra

Emily Welch (Senior Thesis, August 2018, Advisor: Denise Stephens )

Abstract

Brown dwarfs form like stars but are not massive enough to fuse hydrogen fusion in the core. They from between 0.013 M⊙ and 0.072 M⊙ and are difficult to detect because of their low luminosities. Brown dwarfs act as point sources that when imaged spread out their light on the CCD in predictable patterns. These patterns are known as point spread functions (PSF). It is because of this “spreading” that brown dwarf binaries are unresolved when there is small angular separation. Kyle Matt has produced a python script that uses PSF models to determine binarity for unresolved brown dwarfs. I have tested this code and have found some problems in comparing the single and binary fits, but have used the metric of flux percentage from the script output to suggest probable binaries.

Ethan Welch (Senior Thesis, April 2018, Advisor: Dallin Durfee )

Abstract

I seek to make injection locking a more reliable tool in atomic physics by active stabilization. An injection-locked diode laser can be actively stabilized by monitoring either the laser's frequency spectrum or the overall intensity. I used the transmission of a Fabry-Perot cavity to measure the frequency spectrum of an injection-locked laser. When the injection lock is about to break, the intensity of the dominant spectral mode decreases while the overall intensity increases. Similarly, a photodiode measures the overall intensity of the laser. Under certain conditions, the injection-locked laser's intensity corresponds to how strong the injection-lock is. To prevent the injection-lock from breaking, an Arduino Uno measures either the amplitude of the main spectral peak or the overall intensity while simultaneously adjusting the current of the injection-locked laser. By so doing, an injection-lock that has an average lifetime of a few minutes can be stabilized to have a lifetime of several hours.

Jennifer Kay Whiting (Masters Thesis, April 2018, Advisor: Timothy Leishman )

Abstract

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Christopher Yost (Senior Thesis, June 2018, Advisor: Branton Campbell )

Abstract

Crystalline solids consisting of three-dimensional networks of interconnected polyhedra or other rigid polyatomic units are ubiquitous amongst functional materials. In many cases, application-critical properties are sensitive to the rotations of individual rigid units. But the shared atoms that connect the rigid units together impose severe constraints on any rotational degrees of freedom, which must then be cooperative throughout the entire network. A purely algebraic approach to the identification of such cooperative rotational rigid-unit modes (RUMs) has been developed, wherein the constraints of interconnectedness are linearized in the limit of small rotation angles to form a homogeneous linear system of equations. This approach has been integrated into a software package named ISOTILT wherein a user can determine the allowed RUMs of a given network. We’ll explain details of software as well as underlying algorithms used to generate and solve the system of equations.

Sarah Marie Young (Masters Thesis, August 2018, Advisor: Brian Anderson )

Abstract

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