Fall 2016 Physics Colloquium
Thursday, September 22nd
Dr. Joshua Pepper, Astronomer & Assistant Professor, Department of Physics, Lehigh University
"The Golden Age of Exoplanet Discovery"
The past two decades have seen an explosion of discovery of extrasolar planets. For the first time we can learn about the properties of other solar systems. Even though we detect most planets indirectly, we are not beginning to understand what kinds of planets and solar systems are found in our galaxy, and in the next few years we will know how common Earthlink planets are. He will describe the new results from exoplanets surveys including the Kepler space mission, and how we are laying the groundwork for searching for life on other planets.
Thursday, October 27th
Physics Students Summer Research Talks
Natalie Ferris ’18 will present “Opacity of Dense Plasmas: A Model Comparison”
Isolated-atom and average-atom are two approaches for modeling optical properties of warm dense plasmas. The average-atom model includes density- and temperature- dependent wave functions but has crude atomic physics, whereas the isolated-atom approach taken in the Los Alamos National Laboratory ATOMIC code goes into great detail with respect to the atomic physics, with plasma effects included as corrections. We carried out a systematic comparison of these two methods. Despite model differences, we have shown that the average-atom and ATOMIC calculations can be made to give qualitatively similar predictions for the optical properties of warm dense plasmas.
Tyler Richey-Yowell ’17 will present “In Search of Stellar Music: Finding Pulsators for the TESS Mission”
In December 2017, the Transiting Exoplanet Survey Satellite (TESS) will launch for the start of its two-year mission to detect transiting exoplanets. One of the additional objectives of TESS is to observe oscillating variable stars to precisely measure these stars’ masses, radii, and internal structures. Since TESS can observe only a limited number of stars with high enough cadence to detect these oscillations, it is necessary to identify candidates that will yield the most valuable results. Using data from the Kilodegree Extremely Little Telescope (KELT), we searched for bright stars to be top candidates for TESS observation. We found 3,486 variable blue stars with a B-V color < 0.5 and 192 red stars with color > 0.5. Further analysis will be carried out on the blue stars to establish final candidates.
Emily Whitaker ‘17 & Sean Jones ’17 will present “Cooking on Biogas, A Collaborative Project”
This summer the research team worked on answering two key questions, could the implantation of a Solar Air Heater (SAH) increase the temperature of the Dickinson College Farm’s biogas digester and would this assist in the rate of biogas production? This summer work would then be extrapolated to see correlation between temperature and gas production in hopes of sustaining biogas production throughout the winter. The SAH used was designed by Physics Professor Hans Pfister, temperature testing was done with a SAH built during the spring 2016 semester along with a second SAH built over the summer. There were two greenhouses to keep the digester warm; one large one that the digester is stored in and a small one that covers the digester. To mimic cooler temperatures, the inner greenhouse was taken off and a shade cloth was placed over the main greenhouse.
We found that our SAH was 70% efficient and there was a 74% energy transfer from the pipes to the digester. We were then able to predict how much energy would be transferred to the digester over the fall and winter when we needed to increase production. While our ratios between ambient air temperature, greenhouse temperature, and digester are crude, we can still estimate overall digester temperature increase from both SAHs. Based on solar window, the combined efficiency and average temperatures it is expected that we will raise the digester’s temperature between 3 and 6 degrees Celsius in the winter months increasing production by 25-30%.
Cameron Ruhl ’17 will present “Multiferroic Oxide Thin Films: A New PARADIM”
Multiferroic (ferromagnetic and ferroelectric) oxide thin films may provide the foundation for the next generation of non-volatile memory devices and have the potential to overcome many of the limitations of current devices. The oxide thin films grown by molecular beam epitaxy (MBE), for these future devices, are novel compounds epitaxially stabilized to exhibit certain properties. However, although MBE can have atomic layer precision, the extreme condition sensitivity complicates the production of quality samples. To this end, much effort is put into the structural and/or electrical characterization of each sample. Additionally, due to their metastability and rarity in nature, the study of new thin film oxide compounds is often a process of theoretical calculation combined with computer modeling.
Thursday, November 10th
Physics Students Summer Research Talks
Chris Fritz ’17 & Kevin Skowronski ‘17 - “Dynamics of Nonlinear Oscillators”
From the repeated flash of a firefly to the periodic clicking of a car's turn-signal, nonlinear oscillations are ubiquitous in nature. We study the dynamics of populations of such nonlinear oscillators. In particular, we focus on the emergence of a Chimera State in a ring of experimental Electrical Wien-Bridge oscillators. We further present a novel model for nonlinear oscillators, and describe the emergence of Wave Self-Organization as a viable mechanism for understanding cortical oscillations in the mammalian brain.
Amanda Ratajczak ’17 - “Temperature Dependence of Transition-Metal-Dichalcogenide Vibrational Properties”
The vibrational properties of transition metal dichalcogenides (TMDS), specifically molybdenum disulfide and tungsten disulfide, were modeled at various temperatures ranging from 0 K to 1000 K. The qualitative motion of the normal modes of the materials analyzed by hand, and the quantitative frequencies of each were calculated using Density Functional Theory (DFT) and Quantum Espresso. From there, a Quasiharmonic Approximation (QHA) was used to model the thermal expansion of the system to allow for the calculation of thermal expansion coefficients. Comparison of the theoretical results to experimental data shows that the approximation captures some—but not all—of the temperature-dependent effects of the material. The models were observed to follow trends similar to those seen in previous experimental work despite yielding different values.
Jacky Han ’17 - “Human Heat Stress: Major Health Issue of Global Warming”
Human heat stress is already a major health issue in many parts of the world, and is becoming more serious as the climate warms. Previous work by Sherwood and Hooper has shown that exposure to an environment with wet bulb temperatures in excess of 35oC for more than a few hours can result in fatal heat stroke. Maximum wet bulb temperatures today are typically less than 31oC, so it appears this lethal threshold is comfortably far off. Our computer simulation shows that heat stroke threshold is much lower for people who are involved in physical activities, exposed to direct sunlight, obese, or in otherwise poor health conditions. Our results suggest that global temperature increases of a few degrees could trigger large numbers of
heat-related deaths within the next few decades.
Tuesday, November 15th
Sigma Pi Sigma Speaker & Induction Ceremony
Rob Webb '05
Preparing to engage the world? What are you going to do with your degree? Are you even going to use it? Given current employment, career, and lifestyle trends, you can expect unexpected changes in both the magnitude and direction of your career. How do we prepare and adjust for that?
Sigma Pi Sigma Dinner - must sign up for dinner in Tome 201 by November 10th
HUB Social Hall West
Monday, November 28th
Physics Senior Research Talks
Jacky Han - "Recreating the Logistic Map through Circuits - Theory and Simulation"
The logistic map is a dynamical system used to model the discrete-time growth of a population. Due to the existence of chaotic behavior in such a simple system, the logistic map is widely used by students and researchers as a toy model to study non-linear dynamics and the route to chaos. This semester, different simulation systems were attempted and a successful model with high precision was developed. The bifurcation datasets along with the graphs were simulated, and the Feigenbaum constant within chaotic route was also analyzed.
Sean Jones & Kevin Skowronski - "Electronic Realization of the Logistic Map Function"
The prevalence of chaos within the field of physics has drastically increased over the past few decades. However, it has been difficult for undergraduate programs to adjust their curricula to be more inclusive towards the study of chaos due to a lack of physical analogs. One tool through which an understanding of the behavior of chaos can be achieved is the logistic map function. Although the theoretical form of the function is quite simple, there is no simple physical representation with which students can solidify their understanding. We attempt to bridge this gap between the theoretical and physical aspects of chaotic behavior by building an electronic realization of the logistic map function. This circuit operates discretely, and can demonstrate behaviors such as period doubling, also known as bifurcation, and the onset of chaos. Providing undergraduate students with the ability to experience a tangible representation of the behaviors of chaos can allow for an accelerated learning process of the subject matter.
Jacob Grant - "The Cataclysmic Variable V723 Cas"
Recent observations of the binary star system, V723 Cas, indicate that not only is it a cataclysmic variable, but its continued activity indicate it may soon turn into a nova, by a series of events leading to uncontrolled fusion on the surface of the star. Once it does, it will be one of the very few times a star system has been witnessed undergoing such a process. Because of this, an observing run was performed at the National Undergraduate Research Observatory (NURO) in Flagstaff, AZ in order to obtain a more recent light curve for the star. We will then compare our results to the light curve attained in previous works on it in order to see if it shows any signs of increased activity.
Tyler Richey-Yowell - "Modeling of Short Period Eclipsing Binaries in the Cluster NGC 2362"
NGC 2362 is a relative young (5Myr) cluster located around Tau CMa. Because of its age, the cluster offers the opportunity to observe eclipsing binary star systems in several evolutionary stages. We present light curves of seven previously unknown and two scarcely-covered eclipsing systems, covering the entire range of evolutionary status. Among these stars, multiple show signs of the O’Connell effect, caused by either hot spots or circumstellar material. If this circumstellar material was shown to be present in a light curve, it would be possible to calculate the density of the material to predict the change in magnitude for future data. Therefore, the light curves were then recreated using Binary Maker 3.0 to model the systems. As such, we were able to determine the characteristics of these binary systems (mass ratio, temperature, fillout, disk and spot parameters) in every stage of evolution. The results of the models support current evolutionary theories regarding eclipsing binary star systems, as well as shed light onto sources of the O’Connell effect and why it is represented most in certain evolutionary stages.
Tuesday, November 29th
Physics Senior Research Talks
Cameron Ruhl - "Complexity from Simplicity: Observations of the Nonlinear Dynamics of Drven, Vertically Hanging Chains"
While the usual study of oscillating strings involves that of a transversely oscillating, horizontal string fixed at both ends, the situation explored in this project is of a string fixed at a single point of suspension hanging freely under gravity when it is driven horizontally or vertically. These relatively simple mechanical scenarios, result in behaviors of varied complexities, from rod-like and planar pendulum-like motions to types of rotational and even chaotic motions, with several regions of stability and instability and many different transition boundaries. The motions of these chains are experimentally determined at several positions along their length, using a high speed camera and video analysis tools, and then compared to numerically calculated results from different theoretical models in various regimes of the parameters: chain length (L), driver amplitude (A), and driver Frequency (f).
Eli Laue, Megan Hansen & Troy Thornton - "A Comprehensive Solar Air Heater Research Station for the New Senior Capstone Experience"
In accordance with the new direction of the senior seminar, we aim to create a comprehensive capstone project that involves state-of-the art research on a solar air heater.
Solar air heaters (SAHs) have a very high potential for use as sustainable, efficient, and affordable sources of heat. They consist of an insulated box, possibly filled with materials of high thermal conductivity, covered with a clear glazing, through which air is pushed and heated. The efficiency η of a SAH can be calculated as a function of solar irradiance and the air mass flow rate ṁ through the apparatus. Efficiency is maximized with a high air mass flow rate and when convective, conductive, and radiative heat losses are minimized. For this project, we took sample data runs on a 4x8-foot single-pass SAH with 2 layers of corrugated wire mesh and found that its maximum possible efficiency under optimal weather conditions to be ~84%.
At an entry level SAH research does not require extensive background knowledge, allowing any professor to advise such a project and permitting students to engage with the material expeditiously. Furthermore, a SAH leaves room for endless possibilities of modification, increased complexity, and extensive research of various aspects of the device. The SAH's versatility allows for it to be studied with foci in multiple different concentrations, such as fluid dynamics, thermodynamics, materials physics, and even interdisciplinary fields such as environmental science. Finally, research may be done not only experimentally, but also theoretically and through computer simulations. Our goal is to create a cohesive research station, instructor’s manual, and student manual that addresses all these criteria to allow the whole research team to start promptly and maximize their time for research in senior seminar.
Michelle Orden - "Modeling the Cooling of Pillow Lavas and their Fracture Patterns"
Pillow lavas are lava morphologies that form when molten lava comes in contact with ice or water, causing it to cool as a bulbous structure. Looking at the cross-sections of pillow lavas found in Southwest Iceland, we have investigated fracture patterns formed during this cooling process. Among the fracture patterns, we have identified seven end-member characteristics: fractures propagating radially from the pillow edge to the core (5-10cm), fractures on the outer edge (2-4cm), fractures between the edge and core, horizontal fractures, fractures inside the core, fractures propagating from the outer edge through the core, and ‘web-like’ fractures. Using the discretized Heat Equation we have created an Excel based computer simulation that predicts the change in temperature at infinitesimal points throughout a pillow lava as it cools in time. Using this model in tandem with Young’s Modulus and known properties of basalt and ice, we have produced a mathematical model that predicts when and where fractures originate as well as where the fractures will propagate in time. This model can be easily manipulated to fit many different sets of emplacement conditions. It also has potential to be manipulated and used in fields such as engineering or other geosciences in order to better understand when and why certain materials fracture.
Justin Gardner - "Upgrading the Britton Observatory at Dickinson College: Installation of the New CCD and Automation of Observatory Routines"
A new CCD camera, filter wheel, and filter set assembly has been installed on the 24 inch telescope in Britton Observatory. This process involved machining novel telescope mounts for the camera as well as calibrating the CCD, connecting it to the data acquisition computer and validating proper communication. The new filter wheel has auto-guiding capabilities, which enables higher tracking precision during long exposures. This required that a new cable be created and connected to the telescope control system (TCS). In an attempt to make observing runs using the Britton Observatory more efficient and streamlined, steps have been taken to automate many of the monotonous and time consuming tasks currently necessary for astronomical research. This includes telescope focusing and data reduction as well as unifying the hardware and software control systems. A reduction program has been created to process the raw data and prepare it for analysis. This Python script performs all necessary image corrections and reduces user interaction. MaximDL is used as the primary camera control system and data taking program and has capabilities for telescope and dome control, which we hope to utilize in the near future. An autofocusing routine is also being explored to reduce human error and further increase observing efficiency.
Thursday, December 1st
Physics Senior Research Talks
Harry Swanson - "Simulating Orbital Dynamics"
Accretion is a prominent aspect of many astrophysical bodies, from stellar nurseries to quasars. Utilizing the programming Language Python 2.7, various codes were created to model satellites orbiting stellar bodies. As an elementary programmer, the codes began with intense simplicity with gradual increase in complexity. Each of these codes is a step on the journey of creating a final simulation that accurately depicts inelastic collisions and the formation of an accretion disk surrounding a supermassive object.
Amanda Ratajczak & Emily Whitaker - "Exploring the Effects of Frequency on the Dynamics of Gravity-Capillary Waves"
Previous research has found that particles of different diameters have the tendency to cluster in different locations along standing Faraday waves based on their size. These varying accumulation behaviors seem to suggest the existence of some critical threshold diameter at which the contaminants no longer accumulate at the peaks, but rather in the troughs of the waves. The aim of this research is to study the effect of surfactant size and packing density on the coupling between Faraday waves and surface contaminants, and identify the critical size threshold at which accumulation behavior changes. Vertical sinusoidal oscillations will be used to induce Faraday waves in the water, and the system’s response will be observed using a high-speed camera and LabVIEW data collection. Thus far, we have designed our experimental set up, documented critical onset acceleration, examined the relationship of wave number to the amplitude of the wave, and explored how voltage amplitude changes with volume.
Chris Fritz - "A Novel Model for Nonlinear Oscillators"
Many oscillatory systems of great interest exhibit pulsing behavior. The analysis of such oscillators has historically utilized a constant-phase model such as the Kuramoto equation to describe their dynamics. These models accurately describe the behavior of pulsing oscillators on larger timescales, but to not explicitly capture the pulsing nature of the system being analyzed. Indeed, the Kuramoto model and its derivatives abstract the pulsing dynamics and instead use a constantly advancing phase, thereby blurring the specific dynamics in order to fit to an analytically tractable framework. In this thesis, a novel modification is presented by introducing a phase-dependence to the frequency of such oscillators. Consequently, this modification induces clear pulsing behavior, and thus introduces new dynamics such as nonlinear phase progressions that more accurately reflect the nature of such systems. The analysis of this new system of equations is presented and the discovery of a heretofore unknown phenomenon termed periodic stability is described in which the phase-locked state of the system oscillates between stability and instability at a frequency determined by the mean phase. The implications of this periodic stability on the system such as oscillations in the coherence are discussed. The theoretical predictions made by this novel analysis are simulated numerically, and extended to real experimental systems such as electrical Wien-Bridge oscillators and neurons; systems previously described using the abstract Kuramoto model. Finally, novel dynamics of a population of these oscillators such as wave self-organization are presented. The results of this work thus have clear implications on all real systems described presently by the Kuramoto model.