Publisher: Macalester College   (Total: 5 journals)   [Sort by number of followers]

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Bildhaan : An Intl. J. of Somali Studies     Open Access   (Followers: 2)
Cities in the 21st Century     Open Access   (Followers: 17)
Macalester J. of Physics and Astronomy     Open Access   (Followers: 5)
Studies in Mediterranean Antiquity and Classics     Open Access   (Followers: 26)
Tapestries : Interwoven voices of local and global identities     Open Access  
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Macalester Journal of Physics and Astronomy
Number of Followers: 5  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2332-7669
Published by Macalester College Homepage  [5 journals]
  • Smart Grid Control: Demand Side Management in Household Refrigerators as a
           tool for Load Shifting

    • Authors: Anogh Utkalika Zaman et al.
      Abstract: With improved supply of renewable sources of energy the focus has shifted away from simply producing clean energy to efficient consumption of energy. Until cheaper methods of energy storage are developed, Demand Side Management (DSM) is the best option for maximising energy efficiency. This paper proposes a method of turning regular refrigerators into smart demand response fridges. First, we develop an algorithm that accounts for small fluctuations in price and switches the device for optimal performance and lowered running cost. Then, we use longer price fluctuations to predict suitable times for pre-cooling and investigate the reduction in price as a result. Finally, the two models are compared, evaluated and improvements are proposed.
      PubDate: Thu, 12 May 2022 12:23:45 PDT
  • Twisting Lasers with the Faraday Effect

    • Authors: Harrison Werrell
      Abstract: Our objective with this project was to create a system and procedure to quantify the magnetization of a material with polarized light by using the Faraday Effect, where the light is rotated according to the magnetization. This type of system has seen use in technologies such as magneto-optical drives and optical isolators, and is part of the study of optical materials, along with the similar MagnetoOptical Kerr Effect. Our system, specifically, is intended to be used as part of an advanced Physics Lab in the future. It uses an electromagnet to magnetize a sample, and a laser to observe the effects.
      PubDate: Thu, 12 May 2022 12:23:37 PDT
  • Electrical Analysis of a PEM Electrolysis Cell

    • Authors: Joey Wehrley et al.
      Abstract: Polymer Electrolyte Membrane (PEM) electrolysis is a form of electrolysis that is heavily used in commercial capacities. It functions by using a membrane and an electric charge in order to perform electrolysis water, splitting it into its component parts - Hydrogen and Oxygen. These parts can then be used in a number of different applications, including reversing the electrolysis process to regenerate some energy in the form of electricity. During this experiment, multiple currents were run through a PEM cell, and voltages across the membrane were measured. It was found that a standard R/C charging model can be fit to low current applications of the PEM cell, but beyond very small currents, there is little to no correlation between the data results and the model predictions
      PubDate: Thu, 12 May 2022 12:23:24 PDT
  • The Interaction of Topological Defects in Anisotropically-Elastic Nematic
           Liquid Crystals

    • Authors: Carter J. Swift
      Abstract: Topological defects are very well understood so long as the medium in which they exist is isotropically-elastic. They lead to director fields which are easy to calculate and superpose linearly so that a system with any number of defects is analytically treatable. They also have an interaction which is simple in form and can be accurately described by the Peach-Koehler force. In an anisotropically-elastic medium, however, such defects are very poorly understood outside of the single-defect case which was solved by Dzyaloshinskii. In this project, numerical and approximate analytical techniques are applied in order to better understand the interaction between two defects in an anisotropically-elastic medium and how it differs from the well understood isotropically-elastic case.
      PubDate: Thu, 12 May 2022 12:23:15 PDT
  • Neutrino Oscillations in the Presence of a Magnetic Field

    • Authors: Chinhsan Sieng
      Abstract: We calculate oscillation probabilities in the presence of an external magnetic field in a one-generation neutrino framework that includes both Majorana and Dirac mass terms. First, we write down the Euler-Lagrange equations and obtain a system of eight differential equations coupling together eight different neutrino states that can be distinguished by helicity, chirality, and particle/antiparticle-ness. We then solve this system of differential equations in various special cases, exhibiting different types of oscillations. When the magnetic field is in the direction of momentum, there are only four oscillation channels as helicity flip is forbidden. We observe that chirality flips are suppressed by a factor of m2/E2, whereas the transitions involving active neutrinos and sterile antineutrinos are not while having a form similar to two-generation flavor oscillations.
      PubDate: Thu, 12 May 2022 12:23:06 PDT
  • The Impact of Initial Abundances on Modeling the Weak s-Process

    • Authors: Lev S. Serxner
      PubDate: Thu, 12 May 2022 12:21:51 PDT
  • Spectral Fitting Approach for Collective Thomson Scattering Experiments on
           an Extreme Ultraviolet Plasma Light Source

    • Authors: Alyssa K. Rauschenberger
      Abstract: Modern computer chips as well as the entire semiconductor industry rely on Extreme Ultraviolet Lithography (EUVL) at 13.5 nm ± 1% to create finer resolution features. In the industrial settings, the 13.5 nm photons are generated by a plasma following the interaction of 20-30 μm diameter molten tin droplets with focused CO2 pulsed laser beams running at kHz repetition rates. Although the 13.5 nm light generation process has already been comprehensively studied numerically, only a handful of experimental studies report simultaneous measurements of the plasma parameters relevant to the production of the highly charged ions Sn8+‒Sn14+ responsible for the EUV light. Time-resolved collective Thomson scattering measurements, probing simultaneously the electron and ion features would provide a complete picture of the physics at play. To prepare experimental data analysis, a MATLAB-based fitting tool was developed for real-time inference of the electron density, electron temperature and average charge state from Thomson scattering experimental spectra. Least-squares fitting using lsqcurvefit from MATLAB is deployed in conjunction with the analytical expression of the Thomson scattering spectral density function to perform a non-linear regression model for the fitting of the experimental data.This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.
      PubDate: Thu, 12 May 2022 12:21:40 PDT
  • The Survey of HI in Extremely Low-mass Dwarfs: New Results from VLA

    • Authors: Francesco Pecere et al.
      Abstract: We present new HI spectral line imaging of 19 galaxies in the “Survey of HI in Extremely Low-mass Dwarfs” (SHIELD) acquired for Large Program VLA/ 20A-330. Using the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array (VLA) in the C configuration, we produce images of the neutral interstellar medium (HI) on angular scales of 15 to 20 arcseconds (corresponding to physical resolutions of 200 to 1100 parsecs). The three-dimensional cubes probe the morphology and kinematics of the gas at a range of spatial and spectral resolutions. The cubes were collapsed to produce two-dimensional moment maps (representing HI mass surface density and intensity weighted HI velocity). The HI gas was directly compared to the stellar component by comparison against optical and infrared imaging. In most cases, the gas and stars are co-spatial, with the exception of dwarfs with companion galaxies. The SHIELD galaxies are important to our understanding of galaxies’ properties at the low end of the mass spectrum.
      PubDate: Thu, 12 May 2022 12:21:26 PDT
  • Hunting for Fast Radio Bursts from Messier 82: Exploring the FRB--Magnetar

    • Authors: Susie Paine
      Abstract: Fast radio bursts (FRBs) are short-duration radio pulses of cosmological origin. Among the most common sources predicted to explain this phenomenon are bright pulses from a class of extremely highly magnetized neutron stars known as magnetars. In 2020, a Galactic magnetar produced an FRB-like burst, allowing researchers to constrain the Galactic magnetar burst rate. We assume that the magnetar burst rate scales with star formation rate and test an important prediction for similar bursts in nearby galaxies. Messier 82 (M82) has a star formation rate 40 times that of the Milky Way, implying that the magnetar burst rate would be quite high. We observed M82 with the 20 meter telescope at the Green Bank Observatory for 28.2 days. We found 291 candidate bursts, but none of those candidates had a signal-to-noise ratio greater than 10. An S/N of 10 is required for a candidate burst to be considered an FRB. Additionally, none of the repeating dispersion measures (DMs) we found had enough bursts to constitute a confidence level of 5 sigma. Using these constraints, we determined an upper bound for M82's magnetar burst rate to be 0.035/day. Based on this result, we determined that star formation rate cannot scale with magnetar burst rate in the case of M82.
      PubDate: Thu, 12 May 2022 12:21:17 PDT
  • Finite-Difference-Time-Domain Simulation of Ultrafast Experiments

    • Authors: Alpha Ma
      Abstract: The Finite-Difference-Time-Domain (FDTD) method is a numerical method that calculates electric fields or magnetic fields by interleaving them in space and time. Using a python package called “MEEP”, I was able to write optical simulations of ultrafast experiments, especially the Terahertz Pump-Probe experiments. The goal of this project was to use FDTD simulation to measure the transmission of an electro-magnetic pulse passing through a thin film of conducting material on a dielectric substrate in order to study the characteristic conductivity of potential solar cell materials.
      PubDate: Thu, 12 May 2022 12:21:04 PDT
  • Molecular Line Search in Archival ALMA Imaging of M87

    • Authors: Xueyi Li
      Abstract: We present a molecular line search in spectral imaging of the elliptical galaxy M87 using archival data from the Atacama Large Millimeter/sub-millimeter Array (ALMA). The primary goal of this project is to verify and characterize possible CO transition lines, which can be used for future studies to determine the dynamics of the system, or the mass of the supermassive black hole (BH) in the center of the galaxy. After performing extensive atmospheric modeling, we found that most of the absorption features have a corresponding atmospheric ozone transition, so it is unlikely that these features are either Galactic or extragalactic. We also found and corrected a calibration error that introduced an overly sharp absorption feature. After careful continuum subtraction, we calculated line strengths of these absorption features and identified CO emission from high-velocity gas very near the central BH. After analyzing the CO absorption and emission properties, we present a pathway forward for future spectral imaging programs of M87.
      PubDate: Thu, 12 May 2022 12:20:55 PDT
  • Lie Algebras and the Poincare Group

    • Authors: Jack Hempel Costello
      Abstract: This paper will discuss my research with
      Professor Tonnis ter Veldhuis on the Poincare Group
      and other similar algebraic approaches based on the
      Minkowski Metric. This paper will begin with an
      introduction discussing group theory and expand on its
      specific applications in theoretical physics.
      PubDate: Thu, 12 May 2022 12:20:42 PDT
  • Simulating Interactions Between Coronal Mass Ejections

    • Authors: Damen S. Beverlin et al.
      Abstract: Coronal mass ejections (CMEs) launch large amounts of plasma and magnetic fields into the interplanetary medium. Under the right initial conditions, this ejecta can reach Earth and cause issues with electronic devices. As such, we would like to have an accurate model that depicts how these CMEs propagate as they leave the sun. By using fluid dynamics and one-minute resolution in-situ solar wind data, we sought to simulate CME plasma propagation with analytical and numerical models. Because the interstellar medium contains other material and other events happen on the sun simultaneously, CMEs can interact with each other and other ejecta, which can cause them to change, so in order to have an accurate simulation we considered these interactions in our model. For our model, we made the assumption that the plasma was an ideal fluid, was super-alfvenic, and we employed an injection radius of 10 R⦿.
      PubDate: Thu, 12 May 2022 12:20:30 PDT
  • Custom Calibration and Correction of Photoemission Electron Microscope
           Images Using Graphene

    • Authors: Henry Bell
      Abstract: The Photoemission Electron Microscope (PEEM) is a full-field electron microscope that utilizes the photoelectric effect to image a surface. Due to a spatial resolution on the order of 10 nanometers and its ability to image both the morphology of a surface and its band structure, it is a useful tool for understanding the properties of materials for use in electronic devices. To correct for random sample misalignment and the experimental frame of reference in the spectroscopy mode of the PEEM, the 3D dataset must be rotated in both the momentum and energy coordinates which requires pixel calibration and energy alignment. I have created custom Python scripts to both automate this process and standardize the calibration and correction procedure to streamline data analysis for users of the PEEM. Graphene was utilized as an initial calibration material due to its distinct electronic band structure. The 6 Dirac cones of graphene were used as iso-energy points to align the frames on the energy axis and a series of matrix operations were utilized to rotate the image in the momentum axis to correct for sample misalignment. I used the corrected dataset to estimate the Fermi velocity and compared it to theoretical predictions.
      PubDate: Thu, 12 May 2022 12:20:20 PDT
  • Knocking Down NOx: Examining the Effects of Transportation Electrification
           on Urban Ozone Production in the South Coast Air Basin

    • Authors: Jason Beal
      Abstract: With last year’s commitment to all in-state sales of new passenger cars and trucks being zero-emission by 2035 (California Executive Order N-79-20), California is leading the charge for transportation electrification in the United States. Despite being at the forefront of climate change management and mitigation, California has some of the worst air quality in the nation. While primarily motivated by a desire to reduce carbon dioxide emissions and reliance on fossil fuels, transportation electrification will also have a significant impact on local air quality. The goal of this study is to quantify and qualify this impact in the context of urban ozone production. From robust studies of the weekend ozone effect, we know that reductions in vehicle emissions on weekend days can actually increase urban ozone concentrations. By examining data from eight ground monitoring stations in California’s South Coast Air Basin (SoCAB) over a period of 40 years, we show that this region is a volatile organic compound (VOC)-limited system in which the weekend ozone effect is a clear trend. Additionally, these data reveal that despite a significant decline in average annual nitrogen oxides (NOx) emissions, mean ozone levels have changed very little. With this in mind, the question looking forward becomes: how will local atmospheric chemistry and air quality evolve as transportation electrification accelerates' To investigate this question, VOC-NOx ratios are modeled for varying rates of light and heavy-duty vehicle electrification in order to gauge how urban ozone production will be affected. While it is clear that vehicle electrification will ultimately improve air quality and help mitigate climate change, this study provides a unique perspective into the less understood transient impacts of electrification.
      PubDate: Thu, 12 May 2022 12:20:07 PDT
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762

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