Bulletin of the American Physical Society
2013 Annual Meeting of the California-Nevada Section of the APS
Volume 58, Number 14
Friday–Saturday, November 1–2, 2013; Rohnert Park, California
Session H1: Computation and Other |
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Chair: Jerome Buerki, CSU Sacramento Room: Darwin 107 |
Saturday, November 2, 2013 2:00PM - 2:12PM |
H1.00001: Investigating One-Dimensional Stochastic Models for Traffic Flow D. Frawley, N. Pilgram, I. Powell, W. Snyder We developed a program using iPython to investigate traffic. Three different one-dimensional rulesets for the movement and interaction of cars on a road were employed. By studying current vs. density of cars we identified the conditions that lead to phase transitions between smooth traffic flow and traffic jams. The program includes a configurable animation that allows the user to adjust the conditions and observe the flow of traffic. An overview of the program and discussion of future extensions will be presented. [Preview Abstract] |
Saturday, November 2, 2013 2:12PM - 2:24PM |
H1.00002: Escaping from Swarms Katherine Copenhagen, David Quint, Ajay Gopinathan Swarming behavior extends across multiple length scales in biology ranging from bacteria to whales. Swarms are affected differently by erratic, dissenting behavior, sometimes a swarm will follow an agent which changes directions, such as a school of fish when they are done feeding, while other times the swarm lets the individual leave the group while the swarm continues on its way, like a few birds leaving the flock to land in a tree. This research investigates the different universal swarm characteristics that can lead to these different kinds of behaviors. We model flocks with a finite number of agents utilizing a velocity alignment interaction and a Lennard-Jones potential, which provides both cohesive and repulsive interactions between neighboring agents. In the swarming regime of our model, an agent is selected at random to ``escape" the flock, by choosing a particular direction to travel in, and no longer align with it's neighbors. We found that close to the swarming transition the escapee was unable to escape, while deeper in the swarming regime the swarm was more stable and the particle was able to escape with little effect on the rest of the swarm. Our research sheds light on the varied responses of swarms to internal dissent and suggests optimal strategies to escape o [Preview Abstract] |
Saturday, November 2, 2013 2:24PM - 2:36PM |
H1.00003: Testing Machine Learning Methods on Density Functional Theory and Simple Toy Model Kevin Vu, John Snyder, Kieron Burke Kohn-Sham density functional theory (KS-DFT) is a ubiquitous electronic structure method characterized by its relatively high accuracy and low computational cost. However, deficiencies in KS-DFT hamper its efficacy and thus present ongoing avenues of research. The application of machine learning (ML) to KS-DFT is a novel approach which can potentially circumvent many of the drawbacks inherent in KS-DFT. To explore ML's efficacy, we tested it on a simple toy function to see how well our model performed. We examined the dependence of the ML model on the different parameters of the problem and noted how the error of the model responded to changes in each. We also tested the method on the density functional of the standard 1D particle in a box system in order to observe how effective it was in yielding the correct energies. The results showed that ML consistently provided an accurate approximation to the exact functions, demonstrating great promise for the viability of our method. Future efforts will focus on refining the method and continuing to clarify the relationships between the parameters and the ML error. [Preview Abstract] |
Saturday, November 2, 2013 2:36PM - 2:48PM |
H1.00004: Size DOES Matter (the smaller the better) Annie O, Harjyot Mohar, Victor Hernandez, Arturo Estrada A micro droplet generator was designed and constructed to automatically form and eject droplets in the micron size range in a repeatable manner. These droplets were used to investigate dynamic properties such as velocity, acceleration, and drag force. The working medium was composed of a 3 to 1 ratio of water to propylene glycol. An apparatus consisting of a camera, lamp, and electronics were used to facilitate observations of the droplets. Using Stokes' law we extrapolated the terminal velocity through precise measurements of droplet radii. The data revealed that during the ejection process, the droplets experienced a drag force many times their own weight. This led us to the surprising discovery that the droplets were experiencing a significantly large deceleration up to 30 times that of gravity. [Preview Abstract] |
Saturday, November 2, 2013 2:48PM - 3:00PM |
H1.00005: Teichmuller Space Interpretation of Quantum Mechanics Friedwardt Winterberg As Newton's mysterious action at a distance law of gravity was explained as a Riemannian geometry by Einstein, it is proposed that the likewise mysterious non-local quantum mechanics is explained by the analytic continuation below the Planck length into a complex Teichm\"{u}ller space. Newton's theory worked extremely well, as does quantum mechanics, but no satisfactory explanation has been given for quantum mechanics. In one space dimension, sufficient to explain the EPR paradox, the Teichm\"{u}ller space is reduced to a space of complex Riemann surfaces. Einstein's curved space-time theory of gravity was confirmed by a tiny departure from Newton's theory in the motion of the planet Mercury, and an experiment is proposed to demonstrate the possible existence of a Teichm\"{u}ller space below the Planck length. [Preview Abstract] |
Saturday, November 2, 2013 3:00PM - 3:12PM |
H1.00006: Designing Highly Tunable Semiflexible Filament Networks Ronald Pandolfi, Lauren Edwards, Linda Hirst Semi-flexible polymers can generate a range of filamentous networks significantly different in structure from those seen in conventional polymer solutions. Our coarse-grained simulations with an implicit cross-linker potential show that networks of branching bundles, knotted morphologies and structural chirality can be generated by a generalized approach independent of specific cross-linkers. Network structure depends primarily on filament flexibility and separation, with significant connectivity increase after percolation. Results should guide the design of engineered semi-flexible polymers. [Preview Abstract] |
Saturday, November 2, 2013 3:12PM - 3:24PM |
H1.00007: Silicon Photomultiplier Characterization Leonel Munoz, Leo Osornio, Adam Para Silicon Photo Multiples (SiPM's) are relatively new photon detectors. They offer many advantages compared to photo multiplier tubes (PMT's) such as insensitivity to magnetic field, robustness at varying lighting levels, and low cost. The SiPM output wave forms are poorly understood. The experiment conducted collected waveforms of responses of Hamamatsu SiPM to incident laser pulse at varying temperatures and bias voltages. Ambient noise was characterized at all temperatures and bias voltages by averaging the waveforms. Pulse shape of the SiPM response was determined under different operating conditions: the pulse shape is nearly independent of the bias voltage but exhibits strong variation with temperature, consistent with the temperature variation of the quenching resistor. Amplitude of responses of the SiPM to low intensity laser light shows many peaks corresponding to the detection of 1,2,3 etc. photons. Amplitude of these pulses depends linearly on the bias voltage, enabling determination of the breakdown voltage at each temperature. Poisson statistics has been used to determine the average number of detected photons at each operating conditions. [Preview Abstract] |
Saturday, November 2, 2013 3:24PM - 3:36PM |
H1.00008: Silicon Photomultiplier Characterization Leo Osornio Silicon Photo Multiples (SiPM's )or Multi-Pixel Photon Counters (MPPC's) are relatively new photon detectors. They offer many advantages compared to photo multiplier tube. The SiPM output wave forms are still poorly understood. The experiment collected waveforms of responses of Hamamatsu SiPM to incident laser pulse at varying temperatures and bias voltages. Ambient noise, coherent and incoherent, was characterized by averaging the waveforms. Pulse shape of the SiPM response was determined under different operating conditions. Amplitude of responses of the SiPM to low intensity laser light shows multiple peaks corresponding to the detection of 1,2,3 etc. photons. Amplitude of these pulses depends linearly on the bias voltage, enabling determination of the breakdown voltage at each temperature. Several methods determining the breakdown voltage have been developed, with the results being very consistent. Breakdown voltage changes with temperature with the slope of about 50 mV/deg C, although a significance deviation from linearity has been observed at temperatures below -100C.Poisson statistics has been used to determine the average number of detected photons at each condition. This number is proportional to the Geiger probability at the given conditions with respect to over voltage [Preview Abstract] |
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