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TREND Fair 2009
August 7, 2009
On this page... TREND 2009 Presentations
- Implementation of a Time-Delayed Nonlinear Feedback System with Tunable Delay, Stanislaw Antol
- Anomalous Cosmic Ray Production in the Heliosheath, Jacob Chamoun
- Thunderous Acoustics of Bent Plates, Agnès de Montaigne
- Analysis of Dictyostelium Discoideum Motion, Simon Freedman
- Nerve Damage Detection Using Magnetic Pulses, Deepa Jonnagadla
- Communication Using Synchronized Chaotic Systems, Rachel Kramer
- Boolean Gate Network Exploration: Chaos? David Meichle
- Electron Cyclotron Emission Radiometer, Christina Morales
- Use of Photochromic Polymers for Localized Tuning of Photonic Crystals, Daniel Rolando
- Alkali-Metal Photocathodes, Claire Stortstrom
- Velocity Analysis of Particles in Superfluid Helium, Abiy Teka
Stanislaw Antol, Olin College
Advisors: Prof. Rajarshi Roy and Prof. Thomas Murphy
The goal of this research is to design and construct nonlinear electronic time-delayed feedback loops with continuously adjustable time delays (both for feedback and coupling). The system I implemented is an electronic Mackey-Glass circuit with bucket brigade device (BBD) chips for voltage-controlled time delays. With this system, it is possible to experimentally investigate system dynamics for a range of time delays, explore how coupled networks synchronize with different time delay parameters, and investigate adaptive schemes for maintaining synchronization even in the presence of coupling channels with time-varying time delay.
Jacob N. Chamoun, Cornell University
Advisors: Prof. James F. Drake and Dr. Marc Swidak
The offset between the sun’s dipole and rotational axes generates a series of vast folds in the sun’s magnetic field, producing a sectored field structure in which the dominant azimuthal component reverses sign periodically. Between the heliospheric termination shock and the heliopause, these sectors are compressed and the decrease in current sheet thickness between sectors favors magnetic reconnection, an efficient accelerator of charged particles. As interstellar hydrogen drifts across the heliopause, the atoms become ionized in the solar wind and the “pickup” of these particles by the solar wind produces a family of high-energy ions. The energization of these ions is explored, demonstrating that they gain energy by means of reflection inside contracting magnetic islands in a first-order Fermi process.
Agnès de Montaigne, École Normale Supérieure dy Lyon, France
Advisor: Prof. Daniel P. Lathrop
In musical theaters, thin metallic plates are used to imitate thunder. Their broadband spectrum is commonly interpreted as a weak turbulent spectrum. However, complex structures (d-cones, ridges) appear when the plate locally buckles through from convex to concave, thus breaking the linearity of wave interaction. Indeed, the thundering spectrum appears at certain amplitudes, depending on the driving frequency and the plate curvature. We think this threshold is linked with the possibility for snap-through buckling to occur. Using an acoustic, optical and mechanical study of the plate, we detect the presence of a threshold in amplitude. For different radii of curvature, we determine the bifurcations as a function of amplitude and frequency.
Simon Freedman, Illinois Institute of Technology
Advisors: Assoc. Prof. Wolfgang Losert, Colin McCann, Meghan Driscoll
Under starvation conditions, the single-cell organism Dictyostelium discoideum performs an interesting life cycle in which independent cells aggregate to eventually form a spore that ensures the group’s survival. Analysis of the motion and shape deformations of these cells during migration can be used to better understand cell movement in many cell systems, such as embryogenesis and cancer. This work involved using custom MATLAB code to analyze image sequences of individual Dictyostelium cells unable to move toward a chemoattractant due to physical obstruction. Specifically, we focused on measuring the velocities of protrusions from the cell wall that have been observed traveling along the length of the cell. Preliminary results revealed that the motion of these protrusions occur at significantly faster rates when the cell is on the edge of a cliff than when it is unobstructed. Further analysis can reveal details of how a cell attaches to a surface and how this attachment is coupled to motion.
Deepa Jonnagadla, University of Maryland College Park
Advisors: Dr. Robert Fischell and Prof. Wesley Lawson
Currently, the instrument used to detect nerve conduction velocity (NCV), the electromyogram (EMG), operates by sending electric pulses through the body and is quite painful to the patients being tested. We are conducting research to replace the electric pulses with magnetic pulses for the purpose of measuring the NCV in a cost-effective and less painful manner. To accomplish this task, we built a control circuit to deliver a magnetic pulse on demand and constructed the magnet that will be implemented in this circuit. To find the NCV, a pulse detection circuit has to be designed and built. With the combination of these circuits, tests will be performed on humans to check for functionality and side effects. The results from this research could potentially produce a less detrimental and more effective way to administer tests for nerve damage detection.
Rachel Kramer, University of Michigan
Advisors: Asst. Prof. Edo Waks and Prof. Thomas Murphy
Chaotic oscillators, when suitably coupled, can exhibit synchronous dynamics. This phenomenon may be exploited for the encryption and decryption of messages. We unidirectionally couple a pair of chaotic time-delayed optoelectronic feedback loops and use the resulting synchronization to transmit and mask an audio or digital signal. We explore both additive and multiplicative signal encryption techniques. A system relying on synchronization of chaos is inherently sensitive to perturbations in the communication channel. We implement an adaptive strategy to track and compensate for such perturbations. The potential benefits of using such an adaptive strategy on a message-carrying system are explored.
David Meichle, Lawrence University
Advisor: Prof. Daniel Lathrop
Chaotic behavior is exhibited by simple networks of electronic Boolean logic gates allowed to function asynchronously. Previous experimental research has shown these networks are capable of oscillating with nonrepeating patterns of ultra-wideband frequency distribution (DC to ~2 GHz). These cheap and simple devices have potential uses as wideband radio wave sources, sensors, detectors, and jammers. Currently, we are attempting to increase the network’s operating frequency bandwidth by using very high speed logic chips and have seen oscillation harmonics out to 20 GHz. We are also investigating bifurcations and the synchronization of multiple, weakly interacting circuits as a function of the power supply voltage.
Christina Morales, Florida International University
Advisor: Dr. John Rodgers
There is much interest in studying plasmas that generate hot electrons. The goal of this project is to develop a wideband electron cyclotron radiometer to measure the non-Maxwellian rapid rises in electron temperature. These rapid increases in temperature will then be correlated to instabilities in the plasma. This project explores a type of noncontact temperature measurement. We will attempt to show the feasibility of electron cyclotron emissions to measure the Maryland Centrifugal Experiment’s (MCX) electron plasma temperature. The radiometer has been designed to have 100dB of gain and a sensitivity of 24mV/dB given by its logarithmic amplifier. If successful, this radiometer will be used as a diagnostic tool in later projects such as the proposed experiment studying magnetic reconnection using solar flux loops.
Daniel Rolando, Eastern Illinois University
Advisors: Assoc. Prof. Edo Waks and Deepak Sridharan
Due to the sensitivity of the fabrication process, photonic crystal cavities must often be tuned post-production to achieve the desired resonant wavelength. This project uses thin films of spiropyran, a polymer with reversible optical properties, to locally tune photonic crystal. Solutions of spiropyran and polymethyl methacrylate (PMMA) were spun as films onto glass, silicon, and GaAs substrates as well as GaAs photonic crystals. The samples were exposed to both ultraviolet (375nm) and visible (524nm) wavelengths of light, and the reversible changes in color, absorption, and refractive index were measured. Reversible shifts of 5nm in the resonance were observed in the photonic crystal structures. These results were compared to existing papers on similar, but irreversible, index shifts using calchogenide glass coatings.
Claire Stortstrom, Tulane University
Advisors: Prof. Patrick O'Shea and Dr. Eric Montgomery
Robust and efficient photocathodes are used to generate high-quality electron beams for free electron lasers (FELs). Because of their wide wavelength range, high power, and beam quality, applications of such lasers include x-ray diffraction, laser surgeries, and military applications. The FEL beam relies on a photocathode’s quantum efficiency (QE), the fraction of incident photons that cause an electron to be emitted. In order to increase the QE, an alkali metal coating is deposited onto a tungsten cathode from an external source. Alkali metals substantially lower the work function of a tungsten surface, allowing more excited electrons to escape hence increasing QE. In support of both future experimental and theoretical models of emission, we report studies on alkali-based coatings (Cs, K, Na) on tungsten substrates and the resulting QE for such photocathodes.
Abiy Teka, Montgomery College
Advisor: Prof. Daniel P. Lathrop
Previous studies have shown a formation of quantized vortices when liquid helium is cooled below 2.17K. In this experiment we analyze the motion of hydrogen tracer particles both inside and outside the quantized vortices. By developing an algorithm that can produce both the location and the time of different hydrogen particles within specified frames, we were able to show the velocity distribution of the hydrogen tracer particles inside the superfluid helium. We have also discussed the relationship of the acquired velocities of the particles and the transition temperature at which a system is operated. Finally, we are working on developing an algorithm that identifies uniformly spaced particles along the quantized vortices.