# Thesis/Capstone Archive

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Hugh Bates (Senior Thesis, April 2017, Advisor: Eric Hintz )

Abstract

Hα and Hβ indexes are used in astronomy to compare prominent spectral features for celestial objects. By plotting these two particular indexes against each other, astronomers are able to easily differentiate between spectral types of stars. An extensive amount of research has been carried out to create a list of standard stars that appear in a line on the Hα vs Hβ plot. It has long been wondered if different types of objects occupy a different location on such a plot. For example, where do Seyfert galaxies appear on an Hα vs Hβ plot? There is a vast database of spectra from various Seyfert galaxies that can be used to obtain Ha and Hβ indexes. Before expending the time and resources to extract and manipulate these spectra, it is important to test one specific Seyfert galaxy and see if the location of the data on the final plot deems further research in this direction. Data, in the form of spectra, were obtained from the Dominion Astrophysical Observatory (DAO) in Canada for the Seyfert galaxy NGC 4151. This galaxy was studied for 11 nights over the span of two years. This data was reduced and analyzed to obtain the strength of the Hα and Hβ lines for the spectra at varying redshift values (ranging from a redshift of 0 km/s to 3000 km/s). An Hα vs Hβ plot was created for each redshifted spectrum. The results were compared to Ha vs Hβ plots of standard stars, and it was discovered that NGC 4151 occupies a unique location of the plot. Other active galactic nuclei (AGN) may provide information to other regions of this plot, and using this plot may assist astronomers in detecting Seyfert galaxies in a field of observation.

Ashton Brown (Senior Thesis, April 2017, Advisor: Lawrence Rees )

Abstract

With homeland security applications in mind, I constructed and tested a gamma ray and neutron detector designed to detect spontaneous fission events from highly shielded sources. The detector consisted primarily of a 25.4 cm $\times$ 25.4 cm $\times$ 15.2 cm block of Eljen EJ-200 plastic scintillator coupled to four Adit 5-inch photomultiplier tubes. The signals from all the tubes were added following gain matching with a $^{60}$Co gamma source. Using a $^{252}$Cf source, I measured the efficiency of the detector for various shielding types and thicknesses. Data were acquired both with a Cd foil placed on the front of the detector and with the Cd foil removed. The difference of the pulse-height histograms for these two configurations was shown to be a good measure of the neutron source strength. Neutron detection efficiency per fission neutron in a 4$\pi$ detector peaked at 13.5\%, corresponding to a shielding diameter of 20.4 cm. Through single and double pulse analysis, we were able to confidently determine if a fission source was present and also if boron was being used in the shielding.

Garett Brown (Senior Thesis, April 2017, Advisor: Manuel Berrondo )

Abstract

The complexity and pattern found in animal aggregations, such as starling murmurations, reveals emergent phenomena which arise from the simple, individual interactions of its members. Simulated in a two-dimensional algorithmic model, self-driven particles (boids) group together and display emergent flocking characteristics. The model is based on the ideas of consensus and frustration, where consensus is a nonlinear topological averaging that drives the boids toward one of three unique phases, and frustration is a perturbation that pushes the boids beyond these simple phases and toward disordered behavior. The nonlinearity merged with the perturbation produces characteristics which go beyond the dynamic interplay of global and local phase transitions. The emergent results are interpreted in terms of global and local order parameters, and correlation functions. The results also strongly agree with observational data and empirical analysis.

Abstract

The most common challenge faced in architectural acoustics is designing a room with a proper reverberation time that will suit the purposes of the space. At the Center for Change located at 1790 N State St in Orem, Utah, a room known as the Dance Room exhibits an extraordinarily high reverberation time, making communication in the room extremely difficult. Using the EASERA system (Electronic and Acoustic System Evaluation and Response Analysis), as well as a starter pistol with multiple Larson Davis 824 sound level meters, measurements of the reverberation time were made in the room at the Center for Change on March 26th, 2016. Several possible solutions designed to lower the reverberation time were investigated and tested by constructing a computational model of the room using the Sabine equation as well as EASE software (Enhanced Acoustic Simulator for Engineers). Two solutions were chosen, and proposed in a written report to the Physical Facilities Manager at the center, Glenn Klemetson.

Leanne Farnbach (Senior Thesis, April 2017, Advisor: Denise Stephens )

Abstract

Brown dwarf binary systems are typically too small and cold to be visually resolved, making the study of their spectral features the next best method to determine the general nature of these particu- lar systems. I obtained data from the Spitzer Heritage Archive in the near to mid-infrared spectrum for several brown dwarf binary candidates. Using a least-squares approach and over a thousand synthetic spectral models, I performed a statistical analysis to determine which models best fit the original data. From these models, I determined the most likely parameter values for each com- ponent of either the single or binary system which include the temperature, surface gravity, cloud density, and the amount of atmospheric convection for each star. A binary system, or combination of two models, was found to better fit the following dwarfs: Kelu-1, 2MASSW J0036159+182110, 2MASSW J2224438-015852, SDSS J080531.83+481233.1, SDSS J105213.51+442255.7AB, and 2MASS J05591914-1404488. Kelu-1 and SD1052 are visually confirmed binary systems. The results of the statistical fitting match the known temperatures of each component for both stars, implying that this is a reliable method. The next step will be to identify and perform the statistical spectral analysis on additional brown dwarf binary candidates.

Caleb Goates (Senior Thesis, April 2017, Advisor: Traci Neilsen )

Abstract

Acoustic beamforming uses recordings from a microphone array to find sound source locations. The response of a beamformer is limited by two requirements–the spatial Nyquist frequency on the high-frequency end and aperture requirements on the low-frequency end, which correspond respectively to the spacing of the microphones and the total length of the array. These limitations cause any array with a finite number of microphones to have a limited frequency bandwidth over which beamforming results are useful. This paper presents a method for overcoming the high-frequency limitation using phase unwrapping and array interpolation. This process can approximate the response of an array with many more microphones than are present by adding virtual microphone signals determined by interpolation. Experimental and numerical verifications of the method are presented. The method is found to octuple the bandwidth of the array when the source of interest is broadband.

Jeremy Goodsell (Capstone, April 2017, Advisor: )

Abstract

We are building a volumetric display that depends on photophoretic trapping to draw out images in free space. Because our display requires the particle to move very fast, we need to optimize the strength of our trap so the particle will not fall out. We studied the effect of angle-dependent aberration patterns on trapping strength so we can hold a particle and draw images at very high speeds. We mounted a lens on a rotation stage allowing for coarse control of lens angle relative to the incoming beam. By conducting 50 measurements on the maximum trapping time, velocity, and acceleration vs lens angle, we could determine at what angle the trap was strongest. Measurements showed the strongest trapping occurs within a degree of normal incidence but not at normal incidence.

Melissa Hallum (Senior Thesis, April 2017, Advisor: Mike Joner )

Abstract

Reverberation mapping is a technique used to determine the mass of the supermassive black hole at the center of an active galaxy. The technique uses both photometry and spectroscopy. This project focuses on the photometry aspect of reverberation mapping and seeks to determine if the photometric method used will significantly affect the results. The light curves of NGC 4151 produced using AstroImageJ, IRAF, and ISIS are compared. IRAF and AstroImageJ use differential aperture photometry with comparison stars, while ISIS uses image subtraction photometry. ISIS yielded light curves different to those created from AstroImageJ and IRAF. Furthermore, due to errors from comparison stars, it is concluded that image subtraction photometry may be more accurate than differential aperture photometry for this galaxy.

Andrew Patterson (Senior Thesis, April 2017, Advisor: Denise Stephens )

Abstract

Transiting planets can be discovered through the method of photometry. The Kilodegree Extremely Little Telescope (KELT) Transit Survey team is a collaborative effort to discover more transiting planets. Image Reduction and Analysis Facility (IRAF) has been used to create a script to efficiently pipeline the night sky's raw images into processed ones to prepare them for photometric measurements. The details to the structure and reliability of the data reduction script are outlined. The photometric results are sent back to the KELT team. Discussion of the significance of the light curve is also detailed.

David Squires (Senior Thesis, April 2017, Advisor: Justin Peatross )

Abstract

Existing wavefront sensing technologies, like those used in various adaptive optics systems, often have problems dealing with high turbulence conditions. Holographic interferometry could function as a more robust wavefront sensor in high turbulence conditions if the procedure can successfully be taken from theory to practice. To make that step, I built a Mach-Zehnder-style holographic interferometer that measured turbulent phase shifts accumulated in a signal beam over 80 m. To convert holographic interferograms into wavefront-sensing phase profiles, I converted the interferogram into the Fourier plane and isolated features of interest. The experimental results were inconclusive due to design problems and equipment issues.