Bulletin of the American Physical Society
2011 Annual Meeting of the California-Nevada Section of the APS
Volume 56, Number 14
Friday–Saturday, November 11–12, 2011; Menlo Park, California
Session B4: Applied Physics |
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Chair: Michelle Poliskie, Greenvolts Room: Bldg 51 - Kavli 3rd Floor Conference Room |
Friday, November 11, 2011 1:30PM - 1:42PM |
B4.00001: Non-Contact Ultrasound Imaging Applied to Cortical Bone Phantoms Peter Halcrow, Kenneth Ganezer The purpose of this project was to take the initial steps towards applying Non-Contact Ultrasound (NCU) to the in-vivo monitoring of osteoporosis and to quantitative ultrasound imaging (QUS) of the skeleton using cortical bone. This project was also undertaken to find additional applications of NCU beyond its past limited usage in assessing the severity of third degree burns. With an NCU imaging system, a pair of specially designed broadband 1.5 MHz non-contact transducers and cortical bone phantoms we determined bone mineral density, speed of sound (SOS), integrated acoustical response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and two reflection paths, and a digital signal processor were used to collect data from phantoms of known mass density and bone mineral density (BMD). Significant correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 14 phantoms. At least thirty to forty repeated measurements were collected over a period of 1.5 years of the SOS, thickness, and IR for our phantom set, extending through most of the in-vivo range of BMD found in cortical bone. The collected data showed a small variation in the range of measurements of plus or minus 1-2 {\%}. These NCU results were shown to be in agreement with similar results from contact ultrasound to within 1-2{\%}. This study suggests that NCU might find additional applications in a clinical setting in the near future in medical imaging. [Preview Abstract] |
Friday, November 11, 2011 1:42PM - 1:54PM |
B4.00002: Geant4 Microdosimetry for Simulation of Dose Enhancement in vivo at Orthovoltage Energy Nicole Ackerman, Magdalena Bazalova, Edward Graves Dose-enhanced radiotherapy utilizes high-Z materials at a tumor site to increase the local dose from external beam radiotherapy. This effect is due to the increased cross section from the photoelectric effect and the production of Auger electrons. Many past simulations calculated dose in millimeter-scale voxels and ignored heterogeneities in concentration as well as sites of dose deposition at the cellular scale. We develop a cellular-scale Monte Carlo model using Geant4 to predict the dose enhancement in a variety of scenarios. Gold, tungsten, and iodine are simulated in both in vitro and in vivo geometries. We vary the concentration of the contrast agent both internal and external to the cell, and we measure dose only in the nuclear volume, where DNA damage occurs. [Preview Abstract] |
Friday, November 11, 2011 1:54PM - 2:06PM |
B4.00003: Near-field investigation of plasmonic silver nanowires in the mid infrared frequency range Stefan Mastel, Terrance Dunlap, Yohannes Abate We study experimentally the plasmon resonances of silver nanowires (length between 1.5-3 $\mu$m) in the mid infrared (IR) (9-11 $\mu$m) using scattering-type scanning near-field optical microscopy (s-SNOM). We identify the mid IR plasmon modes of Ag rods at different polarizations of the excitation laser via near-field phase and amplitude. By varying the wavelength of the incident laser the interaction between closely spaced nanowires is investigated. [Preview Abstract] |
Friday, November 11, 2011 2:06PM - 2:18PM |
B4.00004: Foundations and Application of Non-equilibrium Thermodynamics Gregory Robinson Non-equilibrium thermodynamics provides a powerful but still unfamiliar way to peer into the properties of systems yet unexplored and holds promise for ready application to important engineered systems. This talk will consider some of the challenges, promises, and progress made toward an intuitive statistical theory of non-equilibrium behavior as well as recent work applying it. We will briefly discuss large deviations and the formalism of Freidlin and Wentzell for perturbed dynamical systems, which recasts certain questions about stochastic processes in the form of Hamiltonian mechanics. The methods and their applicability are illustrated by analyzing transitions between different stable states of a chemical reaction network, supplemented by a fast numerical solution of escape trajectories. We conclude with the prospects for using the ideas and methods in the design of more efficient and reliable grid computing platforms, which are crucial both to modern science and the operation of entire industries. [Preview Abstract] |
Friday, November 11, 2011 2:18PM - 2:30PM |
B4.00005: Anelastic Seismic Pulse Propagation through a Hysteretic Elastic Material using a Realistic Consitutive Relation Dan Kosik The stress-strain relation for unconsolidated or slightly consolidated materials that exhibit hysteretic elastic behavior are often modeled for small strains by higher order terms in the strain with derivative terms or for large strains by linear viscoelastic models. In this way, anelastic behavior is introduced with the characteristic nonlinear wave propagation that has attenuation and dispersion along with higher harmonics generated. A more natural approach is to use the Preisach-Mayergoyz method to model the stress-strain relation as due to opening and closing of void spaces in the material. This leads to a much more realistic stress-strain curve as compared to experimental tests of soil and sand with much of the guess work about what higher order terms should be included removed. For parameters characteristic of sand and soil at the Earth's surface, a comparison of nonlinear to linear seismic pulse propagation shows a nonlinear seismic pulse with a slower propagation speed, dispersion, and attenuation with the development of higher frequency harmonics. As a source input to a 2D model of surface ground roll generation, nonlinear surface wave motion can be studied with the aim to better understand how to attenuate this coherent noise contribution to seismic data. [Preview Abstract] |
Friday, November 11, 2011 2:30PM - 2:42PM |
B4.00006: Numerical Study of Anelastic Wave Interference in a Hysteretic Material with Boundary Andrew Smith, Dan Kosik Many real materials, such as sand, exhibit complex hysteretic behavior which is not modeled accurately using traditional constitutive relations. In this work, a numerical simulation of anelastic wave interference in a hysteretic medium is developed using the method of Preisach and Mayergoyz. In our previous work, two-dimensional anelastic wave propagation from a single cylindrical pressure source was studied. This work focuses on extending this simulation to include multiple simultaneous pressure sources which interfere with one another. A computational study examines deviations from the linear theory with a special emphasis on surface wave motion. Applications to geophysics, particularly in prospecting with the seismic reflection method, will be discussed. [Preview Abstract] |
Friday, November 11, 2011 2:42PM - 2:54PM |
B4.00007: 100 Years of Superconductivity: Perspective on Energy Applications Paul Grant One hundred years ago this past April, in 1911, traces of superconductivity were first detected near 4.2 K in mercury in the Leiden laboratory of Kammerlingh Onnes, followed seventy-five years later in January, 1986, by the discovery of ``high temperature'' superconductivity above 30 K in layered copper oxide perovskites by Bednorz and Mueller at the IBM Research Laboratory in Rueschlikon. Visions of application to the electric power infrastructure followed each event, and the decades following the 1950s witnessed numerous, successful demonstrations to electricity generation, transmission and end use -- rotating machinery, cables, transformers, storage, current limiters and power conditioning, employing both low and high temperature superconductors in the USA, Japan, Europe, and more recently, China. Despite these accomplishments, there has been to date no substantial insertion of superconducting technology in the electric power infrastructure worldwide, and its eventual deployment remains problematic. We will explore the issues delaying such deployment and suggest future electric power scenarios where superconductivity will play an essential central role. [Preview Abstract] |
Friday, November 11, 2011 2:54PM - 3:06PM |
B4.00008: Indian Summer Monsoon Variability during the Last Millennium Mary Rooker, Ashish Sinha The seasonal rainfall associated with the Indian summer monsoon during the instrumental period ($\sim$last 150 years) is characterized by a biennial oscillation, such that monsoon precipitation varied between singularly strong and weak years but rarely deviated far from its mean state for consecutive years. This observation has led to a hypothesis that monsoon is a self-regulating system, regulated by the annual cycle of the heat balance in the Indian Ocean, mediated by the cross-equatorial ocean heat transport from the summer hemisphere through wind-driven Ekman transport. Consequently, the present day water resource infrastructure and the contingency planning in the region does not take into account the possibility of protracted failures of the monsoon or drastic shifts in its spatial patterns. Here we present new millennial-length speleothem-based reconstructions of Indian monsoon variability from a number of sites across India that challenges the underlying physics of the aforementioned hypothesis. Our proxy records of Indian monsoon provide clear evidence for type of low frequency and high amplitude variability in rainfall that have not been observed during the short instrumental period. [Preview Abstract] |
Friday, November 11, 2011 3:06PM - 3:18PM |
B4.00009: Modeling Harpsichord Plucking: The Plectrum and the String Jack Perng, Thomas Rossing, Julius Smith The harpsichord is a plucked string keyboard instrument that was popular during the Renaissance and Baroque music eras. Although it was later replaced by the more expressive piano, it has mounted a comeback due to the early music movement today. A physical model of the harpsichord's plucking mechanism is presented, detailing the plectrum-string interaction which illustrates many aspects of the harpsichord's characteristic sound. [Preview Abstract] |
Friday, November 11, 2011 3:18PM - 3:30PM |
B4.00010: Optimization of a Small Scale Linear Reluctance Accelerator Thor Barrera, Robby Beard Reluctance accelerators are extremely promising future methods of transportation. Several problems still plague these devices, most prominently low efficiency. Variables to overcoming efficiency problems are many and difficult to correlate how they affect our accelerator. The study examined several differing variables that present potential challenges in optimizing the efficiency of reluctance accelerators. These include coil and projectile design, power supplies, switching, and the elusive gradient inductance problem. Extensive research in these areas has been performed from computational and theoretical to experimental. Findings show that these parameters share significant similarity to transformer design elements, thus general findings show current optimized parameters the research suggests as a baseline for further research and design. Demonstration of these current findings will be offered at the time of presentation. [Preview Abstract] |
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