Bulletin of the American Physical Society
Joint Meeting of the Four Corners and Texas Sections of the American Physical Society
Volume 61, Number 15
Friday–Saturday, October 21–22, 2016; Las Cruces, New Mexico
Session C6: Undergraduate Research and SPS |
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Chair: Victor Andersen, Aurora Community College Room: Meeting Room 4 |
Friday, October 21, 2016 1:00PM - 1:12PM |
C6.00001: Robotic 3D Printing of Lattice Structures Jasmine Kim, Daniel Marshall, Kam-Ming Mark Tam, Caitlin Mueller Lattice structures are known to be amongst the strongest materials per weight, however, previous scholarship upon lattices has only considered uniform lattices; new digital fabrication technologies allow for irregular lattices which are even more optimized for strength to weight ratios. In order to prevent the overuse of materials in construction, the MIT Digital Structures Group are researching the concept of digitally fabricated lattice structures. Using a Kuka Robotic Arm with a modified PLA (Polylatic-acid) extruder, we are able to print octahedral lattices, initially as small blocks that can be stress tested, and ultimately as something that can take the weight of the human body. Although 3D printing may provide a new technological method for future architectural structuring, it currently faces geometric and stability issues to print perfect form of lattice. To overcome these challenges, the research focuses on computation, structural design, and force testing. After iterations of load testing and finite element analysis comparison, it is identified that three point joint algorithm performs better than the one point joint algorithm overall. The specimens hold up to 500 times its weight in three point bending test and 1000 times in pure compression. These results prove potentials of lattice structure printing for practical usage in the future. [Preview Abstract] |
Friday, October 21, 2016 1:12PM - 1:24PM |
C6.00002: Confirming Exoplanets Using the Fort Lewis College Observatory Elinor Mullin, Charles Hakes The transit method was used to detect exoplanets. Exoplanets are planets that orbit other stars. Using the Fort Lewis College Observatory telescope, eight transits were captured. The change in magnitude was determined for all eight transit stars and the transit duration was determined for six of the stars. The change in magnitude recorded by the Fort Lewis telescope was compared to the change in magnitude reported on the Exoplanet Transit Database (ETD). All eight transits had an average difference from the ETD of within 0.004 magnitude or 21{\%}. Through this data analysis and comparison it was determined that the telescope at the Fort Lewis Observatory is capable of observing exoplanet transits having a change in magnitude of as small as 0.0087. [Preview Abstract] |
Friday, October 21, 2016 1:24PM - 1:36PM |
C6.00003: High Resolution Speech Directivity of Live Subjects Claire Pincock, Joshua Bodon, Jenny Whiting The directivity of human speech is something that has been often studied. This kind of data is useful for understanding the spectral difference between placing a microphone in one location or another when recording speech. It also can help improve speech privacy, speech synthesis, and classroom setups. Due to the expense of high-quality microphones, the three-dimensional radiation data is often taken with only 32 points of data or less. 32 points of data isn't enough to properly understand the radiation pattern.~Many students and professors at Brigham Young University have developed a higher resolution system which provides 2522 points of data, allowing for a clearer understanding of the radiation of speech around a head. The main focus of this project is to provide talker sources for room acoustics simulation packages so that simulations of speech in those packages will be more accurate. This presentation discusses the methods of measuring and processing that data and the final directivity patterns~of multiple male and female subjects. [Preview Abstract] |
Friday, October 21, 2016 1:36PM - 1:48PM |
C6.00004: Electrical characterization of carrier transport properties in CZTSe solar cells Istvan Gulyas, Ingrid Repins, Jian Li We report measurement of majority carrier concentration, depletion width, mobility, and resistivity in thin-film copper-zinc-tin-selenide (CZTSe) photovoltaic devices. The transport properties of carriers were measured using coordinated admittance spectroscopy and capacitance-voltage techniques in the dark. The depletion width and carrier density are calculated from capacitance-voltage data taken at a range of temperatures. The bias voltage dependence of the modified dielectric relaxation in the absorber of the CZTSe solar cell is also investigated to determine mobility and resistivity. The inflection frequency due to dielectric relaxation is extracted from admittance spectroscopy data. The mobility and resistivity are calculated from the slope of the linear relationship between the square of the freeze-out frequency and the bias voltage, based on a lumped-parameter equivalent-circuit model. We also examine the temperature dependence of the mobility and resistivity. We calculate the activation energy due to mobility and compare it to the activation energy obtained using conventional admittance spectroscopy. This investigation may help understanding the band tail phenomena and/or the potential barrier due to grain boundaries in polycrystalline CZTSe. [Preview Abstract] |
Friday, October 21, 2016 1:48PM - 2:00PM |
C6.00005: High Surface Area Lithium Electrodes Emily Laughlin, Kevin Laughlin, Rita Fan, Sterling Baird, Robert Davis, John Harb, Richard Vanfleet 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. [Preview Abstract] |
Friday, October 21, 2016 2:00PM - 2:12PM |
C6.00006: Electromotive force and current in a superconducting solenoid with limited length induced by a bar magnet and a monopole Lianxi Ma The magnetic flux, electromotive force, EMF, and current $I_{\mathrm{in}}$, induced by a moving magnetic bar and an imaginary magnetic monopole in a superconducting solenoid of multiple turns and length $L$, are numerically calculated. The magnetic field of the bar magnet is approximated with the magnetic field along $z$ axis of a solenoid with length $l$ and radius $a$ and current $I$, while the magnetic field of the monopole is supposed to be inversely proportional to $r^{\mathrm{2}}$. Calculations show that, for a bar magnet, magnetic flux and $I_{\mathrm{in}}$ essentially saturate when the bar moves inside superconducting solenoid, so EMF is zero while $I_{\mathrm{in}}$ is constant. EMF is only induced when the bar enters and exits the solenoid and $I_{\mathrm{in}}$ is zero after the bar leaves the solenoid. For a magnetic monopole, magnetic flux is discontinuous (from positive maximum to negative maximum) when the it moves through each turn of the superconducting solenoid, but EMF caused by changing magnetic flux is continuous while the EMF induced by the a moving monopole is a delta function (moving monopole produces a ring-shaped $E$ field). The total EMF$_{\mathrm{Tot}}$ in solenoid is the superposition of EMF of each turn of coil and the plateau appears. The current $I_{\mathrm{in}}$ continues to grow while the monopole leaves the solenoid. [Preview Abstract] |
Friday, October 21, 2016 2:12PM - 2:24PM |
C6.00007: Elliptical-like orbits on a warped spandex fabric: A theoretical/experimental undergraduate research project Chad Middleton, Dannyl Weller We present a theoretical and experimental analysis of the elliptical-like orbits of a marble rolling on a warped spandex fabric. We arrive at an expression describing the angular separation between successive apocenters, or equivalently successive pericenters, in both the small and large slope regimes. We find that a minimal angular separation of 197 degrees is predicted for orbits with small radial distances when the surface is void of a central mass. We then show that for small radii and large central masses, when the orbiting marble is deep within the well, the angular separation between successive apocenters transitions to values greater than 360 degrees. We lastly compare these expressions to those describing elliptical-like orbits about a static, spherically symmetric massive object in the presence of a constant vacuum energy, as described by general relativity. [Preview Abstract] |
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