Bulletin of the American Physical Society
2014 Annual Meeting of the Mid-Atlantic Section of the APS
Volume 59, Number 9
Friday–Sunday, October 3–5, 2014; University Park, Pennsylvania
Session E4: Plasma and Statistical Physics |
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Chair: Deepak Iyer, Pennsylvania State University Room: Life Sciences Building 007 |
Saturday, October 4, 2014 3:30PM - 3:42PM |
E4.00001: Computational Study of Neoclassical Transport in NSTX using GTC-NEO Matthew Parsons, St\'ephane Ethier, Stanley Kaye, Weixing Wang The stability of a plasma within a magnetic confinement device is subject to the transport of particles and energy across the magnetic field lines. Neoclassical transport theory, describing the motion of charged particles in non-uniform magnetic and electric fields, is often considered the baseline for comparison to experiments. It has previously been noticed that in the National Spherical Torus Experiment (NSTX) device the level of ion thermal diffusion is inversely correlated with the plasma collisionality, such that at low collisionality the level of transport is greater than the neoclassical limit. Three specific NSTX shots at varying collisionality are being studied using the GTC-NEO code to simulate the neoclassical equilibrium and make an accurate calculation of the transport levels during those shots to verify the transport/collisionality correlation and characterize any anomalous transport present. Here is presented preliminary results from this study. [Preview Abstract] |
Saturday, October 4, 2014 3:42PM - 3:54PM |
E4.00002: A simple experimental spontaneously synchronizing phase oscillator circuit Zhuwei Zeng, David Mertens Spontaneous synchronization appears in many natural and laboratory settings, from the synchronous beating of pacemaker cells in the heart to optically coherent arrays of coupled lasers. The toy model for synchronization is the Kuramoto model, a model of nonlinear coupled phase oscillators notable for its phase transition to collective synchronization. Unfortunately, the Kuramoto model is too simple to accurately characterize the dynamics of any experimental collection of oscillators. We endeavored, therefore, to build a set of simple electronic auto-oscillators and to model them with a minimal but accurate phase oscillator description. In this talk, we will introduce the Wien bridge design that we chose for our oscillators. A single auto-oscillator can be described with coefficients for five harmonics and a noise amplitude. We hope this will lead to easy-to-build experimental tests of a number of predictions for and extensions to the Kuramoto model. [Preview Abstract] |
Saturday, October 4, 2014 3:54PM - 4:06PM |
E4.00003: Rotating space elevators: Nonlinear dynamics of celestial scale spinning strings Steven Knudsen, Leonardo Golubovic We explore classical and statistical mechanics of a novel dynamical system, the Rotating Space Elevator (RSE). The RSE is a \textit{double} rotating floppy string reaching extraterrestrial locations. Objects sliding along the RSE string (climbers) do \textit{not} require internal engines or propulsion to be transported far away from the Earth's surface. The RSE thus solves a major problem in space elevator science which is how to supply energy to the climbers moving along space elevator strings. The RSE can be made in various shapes that are stabilized by an approximate equilibrium between the gravitational and inertial forces acting in a double rotating frame associated with the RSE. This dynamical equilibrium is achieved by a special (``magical'') form of the RSE mass line density. The RSE exhibits a variety of interesting dynamical phenomena. Thanks to its special design, the RSE exhibits everlasting double rotating motion. Under some conditions however, we find that the RSE may undergo a morphological transition to a chaotic state reminiscent of fluctuating directed polymers in the realm of the statistical physics of strings and membranes. [Preview Abstract] |
Saturday, October 4, 2014 4:06PM - 4:18PM |
E4.00004: The impact of resolution upon the complexity, information, thermodynamics, and transferability of coarse-grained models Thomas Foley, M. Scott Shell, William Noid By eliminating atomic degrees of freedom, coarse-grained (CG) models allow highly efficient simulations of complex phenomena. However, as a consequence of changing the model resolution, the coarse-graining procedure alters the apparent thermodynamic properties and model transferability. The present work analyzes the effects of model resolution upon the exact many-body potential of mean force (PMF), $W$, and, in particular, its entropic component, $S_W$. We demonstrate that $S_W$ quantifies the loss of information from the atomistic model and impacts the complexity, thermodynamics, and transferability of the CG model. In order to investigate these formal results, we analytically calculate the exact PMF for the popular Gaussian Network Model of proteins and quantify both the energy-entropy balance as well as the entropic contribution to intramolecular interactions as a function of resolution. Interestingly, seven diverse proteins demonstrate strikingly similar shifts in energy-entropy balance with decreasing model resolution. We expect that these results may provide general insight into both the thermodynamic properties and transferability of coarse-grained models for soft materials. [Preview Abstract] |
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