Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session Z11: Energy/Computational Physics |
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Sponsoring Units: GERA DCOMP Room: Sheraton Governor's Square 17 |
Tuesday, April 16, 2019 3:30PM - 3:42PM |
Z11.00001: Nuclear Fission as a Truly Safe, Renewable and Sustainable Energy Source Robert B Hayes With the advent of uranium extraction from ocean water, the reality of nuclear fission being sustainable and renewable can now be realized. With the dissolved fraction in river water from natural erosion annually depositing almost 4 times the current total earth’s energy use, this source is continually being replenished by plate tectonics. With the medical consequences from the Fukushima disaster now comprehensively being predicted to be below statistical significance for observable medical effects, a revolutionary new paradigm is arising whereby nuclear fission is an environmentally friendly and safe energy option (even under disaster conditions). With nuclear waste now similarly demonstrating viable geological disposal at the WIPP, even enduring literal trials by fire, all legitimate technical arguments against the commercial use of nuclear energy are no longer viable. |
Tuesday, April 16, 2019 3:42PM - 3:54PM |
Z11.00002: Estimation of Diffuse Fraction, Hourly and Daily Clearness Indices over Kano and Port-Harcourt Nigeria using NCEP/NCAR Satellite Data Opeyemi Vincent Omole Estimation of Clearness index and Diffuse fraction were calculated using available satellite data obtained from National Centre for Environmental Prediction (NCEP) and National Centre for Atmospheric Research (NCAR) data base covering a period of 10 Years. Direct solar data and diffuse solar data collected were added to give the Global solar radiation. The clearness index (KT) which is the ratio of the global solar radiation obtained at the surface to the total solar radiation at the top of the atmosphere was obtained. The diffuse fraction (KD) was obtained from the ratio of the diffuse solar radiation incident on the horizontal level of earth surface (HD) to the global solar radiation that incident on the surface level (H).The computed clearness index value were used to characterize the sky conditions into clear skies and overcast skies. Port-Harcourt with low clearness index indicated low global solar radiation while Kano with large clearness index indicated high global solar radiation. The implications of these results on the effective utilization of solar energy are discussed. The results also serve as very useful for solar energy collectors in designing and estimation of solar application systems. |
Tuesday, April 16, 2019 3:54PM - 4:06PM |
Z11.00003: A Novel Approach to Study the most Energetic Lightning on Earth Using the Pierre Auger Observatory. Kevin-Druis L Merenda The Pierre Auger Cosmic Ray Observatory has been observing Emissions of Light from Very Low frequency perturbations due to Electromagnetic pulse Sources, or elve(s), since 2005. Elves are caused by the Electromagnetic Pulse (EMP) created during the lightning strike process. When the EMP interacts with the ionosphere base (90 km altitude), a ring of fluorescence emission expands radially, faster than the speed of light. The Fluorescence Detector (FD) of the Auger Observatory records the UV photons from elves every 100 ns. An elve observation by the Auger FD is a 2D projection of the EMP internal structure. Using the 1598 elves recorded by the Auger FD during 2014-2016, we can reconstruct fundamental parameters of elve-inducing lightning strikes. Peak current, current rise time and lightning height are key to characterize the convective thunderstorm below. The Cordoba region in Northern Argentina is known for the highest flash rate of the most extreme lightning on Earth. Global warming models predict a global increase of destructive convective thunderstorms such as the ones near Cordoba. With our elve dataset that overlaps this unique region, we can contribute to the understanding of such storms and refine current models of extreme lightning. |
Tuesday, April 16, 2019 4:06PM - 4:18PM |
Z11.00004: A Discontinuous Galerkin Method for General Relativistic Hydrodynamics in thornado Samuel J Dunham, Eirik Endeve, Anthony Mezzacappa, Jesse Buffaloe Discontinuous Galerkin[1] methods have been applied to special relativistic hydrodynamics, but little is known about their application to general relativistic hydrodynamics and/or problems in curvilinear coordinates. We are developing such a solver, with an eye strongly towards core-collapse supernovae (CCSNe). We show results from three test problems: The first is a 2D, special relativistic Kelvin-Helmholtz instability problem, showing the code’s ability to resolve turbulence; the second is a 2D, special relativistic Riemann problem, which demonstrates the code’s ability to resolve strong shocks; and the third is the standing accretion shock instability problem, a crucial element of the neutrino-driven CCSN explosion mechanism[2], which tests the code’s ability to handle curvilinear coordinates in a stationary background spacetime. These problems also test the code’s use of limiters, such as the slope and positivity limiters. We are developing this code under the thornado framework, and will make use of AMReX[3] to add AMR capabilities. [1] Cockburn, B., & Shu, C.-W. (2001), J. Sci. Comput., 16, 173 [2] Blondin, et al., (2002), ApJ, 584, 971 [3] LBNL |
Tuesday, April 16, 2019 4:18PM - 4:30PM |
Z11.00005: Path integrals for awkward actions David J Amdahl, Kevin Cahill We show how to construct path integrals in theories of scalar fields when the action is not quadratic in the time derivatives of the fields. In such theories, the hamiltonian is not quadratic in the canonical momenta and may be unknown. The weight functions of the resulting path integrals can assume negative or complex values. We show how to compute them by combining the Monte Carlo method with parallel numerical integration and a lookup table. This “Atlantic City” method lets one study a wide class of theories of scalar fields.
The approximation of multiple integrals whose weight functions assume negative or complex values is a long-standing problem. The Atlantic City method solves it in all the field theories we have examined.
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Tuesday, April 16, 2019 4:30PM - 4:42PM |
Z11.00006: Amorphous Graphene-Based Plasmonic Metasurface for Near-Infrared Absorbers ChunYu Lu, Md. Mahfuzur Rahman, Matteo Chiesa We experimentally demonstrated an amorphous graphene-based metasurface yielding near-infrared super absorber characteristics. The structure is obtained by alternatively combining magnetron-sputtering deposition and graphene transfer coating fabrication techniques. The thickness constraint of physical vapor deposited amorphous metallic layer is unlocked and as a result, the as-fabricated graphene-based metasurface absorber achieves near-perfect absorption in the near-infrared region with an ultra-broad spectral bandwidth of 3.0 μm. Our experimental characterization and theoretical analysis further points out that the strong light-matter interaction observed is caused by localized surface plasmon resonance of the metal film’s particle-like surface morphology. In addition to the enhanced light absorption characteristics, such an amorphous metasurface can be used for surface-enhanced Raman scattering applications. Meanwhile, the proposed graphene-based metasurface relies solely on CMOS-compatible, low cost and large-area processing, which can be flexibly scaled up for mass-production. |
Tuesday, April 16, 2019 4:42PM - 4:54PM |
Z11.00007: Investigating evidence of intrinsically localized vibrations in NaI crystal using van-Hove singularities of the two-phonon density of states Benjamin A Agyare, Peter S Riseborough Intrinsically localized modes (ILMs) are reported in NaI and exist only for wave-vectors at the corner of the 3-D Brillouin Zone. ILMs occur for high-symmetry values, q at which the van-Hove singularities of the two-phonon density of states (DOS) coalesce. The basis for this suggestion is that anharmonic interactions together with the rapid variation of the two-phonon DOS near the band edge may result in the preferential formation of ILMs at these q values. We investigate the van-Hove singularities in the two-phonon DOS, using the experimentally determined acoustic phonon modes ratio of nearest neighbor and next-nearest neighbor force constants. We obtained the two-phonon DOS spectrum for various q in the harmonic approximation and found that they exhibit non-divergent van-Hove singularities. The frequencies of these features vary as q is varied. We found the q value, which mostly enhanced the two-phonon DOS. Furthermore, we isolated the energy and related variable momentum values at which the two-phonon DOS coalesce at the upper edge of the continuum. Now we introduce anharmonic interactions and investigate whether that can bind the two-phonon excitations to produce a quantized ILM. |
Tuesday, April 16, 2019 4:54PM - 5:06PM |
Z11.00008: GGA+U and hybrid functional calculations of intrinsic defects and transition metal doping in NiO Samuel R Cantrell, Luisa Scolfaro, Pablo Borges, Wilhelmus J Geerts Nickel oxide (NiO) is a transparent conducting oxide which has become an active area of research due to it's potential to be used in the next generation of Resistive RAM (RRAM) and Solar Cell devices. Thus it is of interest to study the intrinsic defects responsible for this resistive switching mechanism as well as transition metal (TM) dopants (Fe, Cu, Ag,) in order to improve desired characteristics. Density Functional Theory (DFT) together with the VASP-PAW method based ab initio calculations was used to study the effects of introducing these into rocksalt NiO. Exchange-correlation effects were included in the calculations within the generalized gradient approximation where to better describe the d-orbitals of Ni and TM-dopants a Hubbard potential U contribution was added (GGA+U). Results also considering a hybrid functional (HSE06) to treat the exchange correlation are shown for both the pristine and TM-doped systems. Doped NiO systems were studied using supercells grown along the [111] direction of 32 to simulate anti-ferromagnetic configurations. Stability of these systems was investigated through the calculation of formation energies of these systems in order to discern what is most energetically favorable. |
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