Bulletin of the American Physical Society
2007 Ohio Section of the APS Spring Meeting
Volume 52, Number 5
Friday–Saturday, May 4–5, 2007; Ypsilanti, Michigan
Session P1: Poster Session |
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Chair: Ernie Behringer, Eastern Michigan University Room: EMU Student Center 310AB, 5:00pm - 6:15pm |
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P1.00001: Transport at MARFE Onset in TEXTOR: Implications for H-mode Threshold and Density Peaking Frederick Kelly Analysis of TEXTOR power scan data, taken just before MARFE onset, shows an increase of the conductive heat flux from 40 to 60{\%} as the NBI heating increases from 0.61 to 2.33 MW. The effective thermal diffusivity generally increases from 12 to 25 m$^{2}$/s, while the convective velocity generally decreases from 50 to 25 m/s with increasing heating power. However, the convective velocity is anti-correlated with the line-average density suggesting a pinch effect. The pinch is explained in terms of SOL flows and implications for the H-mode threshold and density peaking are presented. [Preview Abstract] |
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P1.00002: New 100 + Year Road RALE System With T-Beam Foundation Saves Energy and Increases Safety by Reducing Work Zones David Pressler Traffic crashes represents a loss of 2.2 percent of the U.S. Gross Domestic Product a year. By reducing congestion and the number of dangerous construction zones it is possible to increase user safety with fewer accidents. This new system once implemented eliminates many major national road preservation projects, which include replacing or reconstructing the highway pavements over the long period. Other included costs like those of lost time and lost fuel incurred by passenger and freight transportation on the section being reconstructed amount to well over 100 billion dollars a year. All other things being equal, thicker concrete highway pavements will last longer, however, thicker pavement costs more. By utilizing the physics of the T-Beam or the ``floor-joist,'' concept where the upper deck of the highway is supported and reinforced by longitude beams or rails that protrude into the soil, there is a great improvement in the strength of the pavement system. The pavement structure configuration of rails supports and carries vehicle loads, which is transferred ``down-the-road.'' Much like a snowshoe or like a rail bridge this device spreads out the applied stresses over a much larger area and the high strength pavement resists flexing of the concrete. Stress reduction reduces concrete fatigue and this allows the highway to last three to four times as long without major road reconstruction. [Preview Abstract] |
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P1.00003: Using Data compression as a measure of predictability in stochastic stock price data Eli Sacks, Haowen Xi, Edward Mandere In this paper we will use a compression algorithm to study the information contained in a stochastic and noisy data. In particular we will use wavelets to compress the random stock price data and study whether the compressibility is a good indicator of the predictability of a price pattern We first apply the compression to data generated from a random walk. We then use this as the base to compare against other data. We will then apply the compression to a regular data set (such sine function). We will also add some noise to a regular function and try and compress that too. Finally we apply this to stock data to see if it reveals a pattern or not. [Preview Abstract] |
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P1.00004: MMI based Electro-Absorption Modulator Design A. Sala, Y. Sikorski Electro-Absorption Modulators (EAM) are among the most important components of high-speed WDM optical communications devices and systems. During the last decade, multiple EAM designs were proposed and fabricated as stand alone devices, as part of Electro-Absorption Modulated Lasers (EML), and as part of multi component Planar Lightguide Circuits (PLC). Vast majority of all designed and fabricated EAMs employ a straight section of single mode waveguide. In this work, we present a new approach for EAM design which is based on the use of 1*1 Multimode Interference structure (MMI). We demonstrate improvements in the extinction ratio of the EAM based on a combination of electro-absorption and optical interference effects in the MMI structure. The increase in extinction ratio is not accompanied by an increase in insertion loss or chirp, nor does it lead to higher drive voltage or lower bandwidth. The MMI based EAM devices can be easily fabricated using current InP based fabrication technologies and, in-fact, allow for less stringent tolerance requirements than currently used for traditional EAM devices. [Preview Abstract] |
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P1.00005: Calculation of Optical Signal using Bidomain/Diffusion model Reveals Exponential Decay of Transmembrane Potential Phil Prior, Brad Roth The understanding of how the transmembrane potential is affected during ventricular defibrillation is important in electrocardiology. One way of experimentally determining the potential is through optical mapping using voltage-sensitive fluorescent dyes. The fluorescent light of these dyes originates from a few millimeters below the tissue surface as well as at the surface, causing the optical signal to be averaged over a depth. In our study, the transmembrane potential is calculated in a 3-D cube of cardiac tissue located between two point electrodes. The transmembrane potential and optical signal have been numerically calculated using a Bidomain / Diffusion model. This model has the advantage of combining the electrical properties of cardiac tissue represented by the bidomain model with the equations that describe photon diffusion in turbid media. Our results show that the average transmembrane potential is greatly affected by lateral optical averaging as well as averaging over depth. We conclude that the effect of averaging is greater near the electrode than far from it. The result is that the averaged signal falls off more readily as a single exponential than does the surface transmembrane potential. [Preview Abstract] |
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P1.00006: The Role of Morphology in the Optical Response of a Nanocrystalline Organic Donor-pi-Acceptor System Jeffery Raymond, Guda Ramakrishna, Theodore Goodson, III The viability of small, donor-pi-acceptor (D-A) molecules for optical and non-linear optical studies is known. The effect of morphology on the solid-state optical response of a nanoscale organic D-A crystal will be investigated. Comparison of nanocrystals made under several conditions will be made, as wells with the liquid phase molecule and the bulk crystal. [Preview Abstract] |
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P1.00007: Single pulse excimer laser fabrication of nano-sharp conical silicon arrays: computer modeling for optimal experimental parameters. Julia Eizenkop, Ivan Avrutsky, Daniel Georgiev, Vipin Chaudhary We present computer simulation and experiment on the formation of sharp conical tips on single-crystal silicon thin films, silicon-on-insulator (SOI), subjected to irradiation by a single 25ns pulse from a KrF excimer laser, focused onto a spot several micrometers in diameter. These structures have heights of about 1 $\mu $m and apical radii of curvature of several tens of nanometers. Besides technological applications like probes for scanning probe microscopy techniques and emitters for field-emission-based devices, new methods for fabrication of such structures are of interest to a number of novel biomedical design schemes. These include regulation of the attachment, growth and morphology of neural cells, and implanted electrode arrays for neural communication experiments and sensing. This new laser-based technique is simple, offers very good reproducibility, and is a potentially low-cost technological solution for the fabrication of such structures. Our computer simulation includes two-dimensional time-dependant heat transfer and phase transformations in Si films on SiO$_{2}$ substrates that result from the laser irradiation and serves to determine best conditions to produce conical tips. [Preview Abstract] |
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P1.00008: Temperature-Dependent Characterization of Thin-Film Filters for Optical Communications Corneliu Rablau, Christopher Schenk The explosive increase in the demand for transmission capacity for optical communications networks has resulted in a widespread deployment of dense wavelength division multiplexing (DWDM). Thin film filters are a critical component of DWDM devices. They consist of Fabry-Perot resonant cavities obtained by vacuum deposition on a glass substrate of alternating layers of two dielectric materials of different indices of refraction. The performance requirements for these filters are determined by the density of channels to be multiplexed. For the 100 GHz ITU grid, these channels are spaced 100 GHz (0.8 nm) apart. Typical figures of merit include the insertion loss (IL), band width (BW) at 0.5 dB and at 25 dB below peak transmission, and the shape factor (BW@ 25 dB) / (BW@ 0.5 dB). The thermal drift of the transmission profile of the filter and the thermal stability of its insertion loss are two of the ``killers'' of thin-film filter devices. In this work, the thermal behavior of the wavelength-dependent transmission profile for several commercially-available thin-film filters for WDM is investigated, and the temperature limits for proper operation are determined. Comparison with other components for DWDM (such as Fiber-Bragg gratings and/or fused WDM devices) may also be included. [Preview Abstract] |
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P1.00009: Low-Energy Electron Diffraction Investigation of the Cu(511) Stepped Surface Christopher Lemon, Mellita Caragiu, Renee Diehl, Kelly Hanna, Hsin Li, Rundong Wan Preliminary results concerning the investigation of the clean Cu(511) (stepped) surface are presented with emphasis on the computation part of the investigation. Low-energy electron diffraction (LEED) calculations applied to stepped surfaces are usually associated with convergence problems due to the very small interlayer spacing of the sample to be investigated [K. Pussi, M. Caragiu, M. Lindroos, R.D. Diehl, Surf. Sci. 544 (2003), 35]. Therefore, composite layers made of several (7-10) close-spaced layers have been used in resolving the clean Cu(511) structure employing the TLEED (Tensor LEED) computer software [A. Barbieri, P.J. Rous, A. Wander, M.A. Van Hove, Automated Tensor LEED Programs]. Ideally, the electron beam diffracted by the sample should hit the surface under normal incidence. This is, however, hard to control due to the existence of only one symmetry plane of the real structure, which, in turn, gets translated into only one symmetry plane in the reciprocal space. The uncertainty in the angle of incidence makes the angle itself a variable parameter in the LEED calculation, beside the usual parameters to be fitted during the calculation. [Preview Abstract] |
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P1.00010: Resistivity Change During the Growth of Thin Cu Films Meredith Rogers, Dennis Kuhl The resistivity of thin metal films during growth by vacuum thermal evaporation of Cu was studied. It is known that during the first stages of growth atoms gather in small islands that increase in size and eventually form conducting paths across the substrate. Once a continuous film is formed, the resistivity decreases as the film grows. As long as the thickness of the film is smaller than the mean free path, scattering events from the surface contribute significantly to the resistivity causing it to be well above the bulk value. Once the film thickness exceeds the mean free path, the resistivity approaches the bulk resistivity of Cu. [Preview Abstract] |
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P1.00011: Practical Thermal Conductivity Problems Katherine Ballentine, Gregory Bee, Marshall Thomsen Introductory physics books often use simple, practical examples to illustrate the thermal conductivity equation. Heat conduction through a window is a particularly nice example due to its simple geometry. However, the temperature difference across the window is often incorrectly assumed to be approximately the difference between the indoor and outdoor air temperatures. Measurements of actual inside and outside surface temperatures on single pane windows show a much smaller temperature difference than that associated with the ambient air. Using the actual temperature difference across the glass can reduce the predicted heat flow rate by as much as an order of magnitude. Implications for other thermal conductivity problems will also be presented. [Preview Abstract] |
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P1.00012: Evaluation of the Performance of a ``Tube-Scanner'' Type STM Xiao Qiu Bao, Craig Howald The performance of a tube-scanner type scanning tunneling microscope (STM) is evaluated. Since tunneling current noise is a basic limitation for the performance of a STM, it is important to eliminate it as far as possible. The dominant noise in tunneling current is the noise in tip-to-sample distance because tunneling current is exponentially dependent on this distance. Minimizing this vibrational noise is achieved by raising the lowest mechanical frequency of the STM. To facilitate this, various dependencies of the lowest resonant frequency are calculated using three simplified models. Resonant frequencies are also measured using both the piezo-electric effect in the tube scanner and the tunneling current. Comparison of the measurements and calculations of the mechanical response of the STM allows us to identify useful improvements in STM designs. [Preview Abstract] |
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P1.00013: A Computational Study of the Dynamics of a Driven Hanging Cable William Hollandsworth, Cavendish McKay We take a look at two numerical methods to analyze the dynamics of a driven hanging cable.~ One includes the tension necessary to keep the length of the cable fixed, while the other employs a Lagrangian scheme which removes the necessity of calculating the forces of constraint.~ We then use the Lagrangian model to map out the phase space to get an idea of what kind of behavior various frequencies and amplitudes of driving create. [Preview Abstract] |
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P1.00014: Physical Analysis of the Drag and Magnus Coefficients of the Topspin Tennis Ball Elizabeth Smith, Craig Howald We experimentally determined the drag and Magnus coefficients of a topspin tennis ball using video analysis. Three video cameras were used to record the initial spin, projectile motion, and final spin of the ball. From these recordings the initial velocity, initial spin, final spin, horizontal acceleration, vertical acceleration, x position, and y positions of the ball were extracted. The coefficient of drag was calculated to be CD=0.6104 +/-0.06187 and the Magnus coefficient was calculated to be CM=0.6576+/-0.08767. [Preview Abstract] |
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P1.00015: Laboratory Test of Newton's Second Law for Small Accelerations Brian Woodahl, Jens Gundlach, Stephan Schlamminger, Chris Spitzer, Ki Choi, Jennifer Coy, Ephraim Fischbach We have tested the proportionality of force and acceleration in Newton's second law, F=ma, in the limit of small forces and accelerations. Our tests reach well below the acceleration scales relevant to understanding several current astrophysical puzzles such as the flatness of galactic rotation curves, the Pioneer anomaly, and the Hubble acceleration. We find good agreement with Newton's second law at accelerations as small as 5 x 10$^{-14}$ m/s$^2$. [Preview Abstract] |
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P1.00016: The Not-So-Simple Harmonic Oscillator William Sears, G. Whitmore Hancock The study of simple harmonic oscillators is a staple of physics courses and laboratories at the introductory level. We consider a system consisting of a vertical spring with a suspended mass. One typical laboratory experiment is the demonstration of Hooke's law using static measurements of extension vs. force. Another is the demonstration of simple harmonic motion using dynamic measurements of T$^{2}$ vs. the effective system mass. Theoretical analyses predict linear relationships for both experiments. The slopes of the best-fit lines are g/k for Hooke's law, where g is the gravitational field strength and k is the force constant, and (4$\pi^{2})$/k for simple harmonic motion. It would appear that these results provide a straightforward way of calculating a value for g. The work done for this senior capstone project strongly suggests that it may not be feasible to determine a reliable value of g using these two experiments alone. Some ideas for alternative formulations of these experiments at the level of intermediate and advanced physics laboratories will be suggested. An additional set of experiments involving magnetic damping of the same system was performed with excellent results. [Preview Abstract] |
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P1.00017: Experiments on interacting dust molecules in complex plasma A.C. Herrick, T.E. Sheridan A dusty plasma consists of an ionized gas with dust particles suspended in it. Dust molecules form when two microspheres are bound together vertically due to the wake potential. A two- dimensional configuration of two such dust molecules was created in the D.O.N.U.T. (Dusty Ohio Northern University experimenT). Experiments were done to determine how the forces acting on these molecules depends on the plasma density. Information about these forces was inferred through observations of particle spacing and thermal fluctuations as rf power was increased. [Preview Abstract] |
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P1.00018: Experiments on melting in two dimensions: Desperately seeking the hexatic phase T.E. Sheridan The melting transition in a two-dimensional complex plasma is studied in the DONUT experiment (Dusty Ohio Northern University experimenT). An initially strongly-coupled crystal made of $n\approx 3900$ monodisperse microspheres is ``heated'' by amplitude modulating the rf discharge power with a square wave at the vertical resonance frequency. The vertical motion is found to excite ``random'' acoustic waves in the plane of the crystal (i.e., the horizontal direction), effectively heating the crystal. As the ``temperature'' of the complex plasma increases, we observe a melting transition in qualitative agreement with the Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY) scenario. Translational order is initially lost as the dislocation density grows, and a hexatic phase is observed with short-range translational order and long-range orientational order. Further heating destroys the orientational order, resulting in a liquid. [Preview Abstract] |
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P1.00019: Simulation of solitons in two-dimensional complex plasma M.J. Garee, T.E. Sheridan We have developed a one-dimensional simulation for longitudinal waves propagating in a two-dimensional hexagonal lattice of particles interacting through a shielded Coulomb potential (i.e., a Yukawa or Debye--H\"uckel potential) with Debye length $\lambda$. Dispersion relations were computed for various values of the Debye shielding parameter $\kappa = a/\lambda$, where $a$ is the lattice constant. The acoustic speed computed from the simulation is in excellent agreement with theory. The evolution of localized Gaussian velocity perturbations has been studied. We find that compressive pulses steepen and form solitons. Rarefactive pulses do not form solitons, but rather evolve into wave trains. [Preview Abstract] |
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P1.00020: Analysis of Supersonic Dust particles in Complex Plasmas William Theisen Dust particles traveling at supersonic velocities were detected. Stable systems containing one, two and three supersonic particles were studied. The particles traveled below a two dimensional Coulomb crystal consisting of electrically charged microspheres. The strongly-coupled dusty plasma disk was arranged in a hexagonal lattice in a horizontal plane and levitated in a parabolic potential well. Trajectory plots and speed distribution charts of the supersonic particles indicate non Levy flight characteristics. The speed distribution of the particles is non Maxwellian and increases quadratically with a sharp cutoff. [Preview Abstract] |
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P1.00021: Gas and Stellar Kinematics in the Galaxy NGC 4736 Andrew Magyar, Jason Pinkney, Karl Gebhardt We use long-slit spectroscopy and CCD imaging from both ground-based and space-based observatories to analyse the gas and stellar kinematics of the Sa/b galaxy NGC 4736 (M 94). We intend to measure the mass of the central supermassive black hole. We use standard software (IRAF) for the reduction of the spectra, and to create a continuum-subtracted H-alpha image. We develop our own software for the fitting of absorption and emission lines. It subtracts the absorption-line (stellar) component from the emission-line spectra using a shifted template star. This improves the measurements of the shape, centroid, and line strengths of the residual emission lines (H-alpha, [NII], [SII]). We present a preliminary comparison of stellar and gas kinematics, including rotation curves and spatially resolved velocity dispersion. The emission line velocity profile is complex at both low and high resolutions. At high resolution, the profile is not consistent with a simple disc model for the line emitting gas, confounding the measurement of a central black hole. [Preview Abstract] |
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P1.00022: Simulations of Polarization from Radio Jet Cores of Active Galactic Nuclei Brian Welch, Daniel Homan We present results of simulations of the polarization properties of the parsec-scale radio cores from a complete sample of Active Galactic Nuclei (AGN). The jet cores were modelled as a cube of uniform plasma with magnetic field which could vary from sub-cell to sub-cell within the cube. The full equations for radiative transfer were solved numerically to find the polarization emerging from the cube. We found that the circular and linear polarization distributions from our sample could be reproduced either through an initially stochastic magnetic field with an induced shock or with some initial imposed field order. We will discuss the constraints and limitations of these competing models. [Preview Abstract] |
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P1.00023: Study of small Debye clusters in highly anisotropic potential wells Kevin Wells, T.E. Sheridan A Debye cluster is a group of n dust particles in a plasma interacting through a shielded Coulomb (i.e., a Debye) potential. A rectangular trap forms an anisotropic potential well which confines the cluster into a two-dimensional ellipse. It is expected that as the well anisotropy increases, the elliptical cluster will become elongated and at some point all the particles will lie in a straight line so that the cluster is fully one dimensional. Experiments performed in the DONUT experiment (Dusty Ohio Northern University experiment) for two confinement geometries and for n = 2 to 24 particles have shown the stages of the two-to-one dimension transition. We find that as the number of particles decreases, the two-dimensional ellipse shrinks and then grows two linear tails forming a ``barred elliptical'' cluster. For n less than or equal to 6 the clusters are fully one dimensional. [Preview Abstract] |
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P1.00024: Experimental Measurements of Diffusivity of Vapors through Porous Substrates Hongyang Li, Carlos Rincon, Elizabeth Bowden, Ali Zand, Yuri Sikorski, Matthew Sanders, Homayun Navaz The release of numerous toxic chemicals, such as hydrocarbons, pesticides, chemical warfare agents, etc.; into soil, subsurface, concrete, brick and asphalt poses a great threat to the biosphere environment. The quantification and extent of spread of these chemicals has primary importance for carrying out the remediation work. There are several well known spread mechanisms which govern the mass transport in porous media. They include various regimes of liquid and vapor transport/diffusion. Modeling the transport of vapors in porous substrates requires the knowledge of the diffusivity of each particular vapor in each substrate. We present a simple, effective and inexpensive experimental method and apparatus for measurement of vapor diffusivity in porous media. [Preview Abstract] |
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P1.00025: SEM Analysis of Glue Behavior When Bonding Glass Structures with Complex Geometries Yuri Sikorski, Robert Cunningham, Herman Orgeron, Chris Schenck, Ali Zand Bonding of glass has been studied for many years and is a mature technology today. However, the recent advances in bio-photonics and micro-fluidics, such as lab-on-a-chip devices, accentuate a need to provide reliable adhesion and sealing of components with extremely complex surface geometries. In many cases it is necessary to prevent the adhesives from leaking into microscopic channels, capillaries and holes. We present the Scanning Electron Microscopy study of adhesion of glass samples with complex surface features. Variety of adhesion conditions and procedures were tried and studied. The results demonstrate the possibility of controlled reliable adhesion and sealing without filling/obstructing the microstructures. [Preview Abstract] |
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