Shared-Memory Scalable k-Core Maintenance on Dynamic Graphs and Hypergraphs.
Abstract not provided.
Gabert, Kasimir Georg↗
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Shared-Memory Scalable k-Core Maintenance on Dynamic Graphs and Hypergraphs.
Abstract not provided.
Gabert, Kasimir Georg↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
The discovery of simple, theoretically sound upper limits for geomagnetic moments (dipole, quadrupole, etc.) provides a significant use of MAGSAT data, establishes useful constraints for future magnetic models, and bears strongly on the probable time required before the next polarity reversal can occur. The field models of MAGSAT data are of prime use and are highly suitable as supplied to date.
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
An additional approach is being taken to address the problem of how to decide where to truncate spherical harmonic representations of geomagnetic data. The idea is to simply evaluate some aspect of interest at successively higher levels of truncation and then to chose that value of truncation level (N) which gives the most reasonable appearance of convergence. The preliminary determination of the onset of relative numerical stability at a truncation level of N=7 in two independent studies is thought to be a potentially significant result of practical value for field modeling. It requires further substantiation and explanation before dissemination.
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
The magnetic determination of the depth of the core-mantle boundary using MAGSAT data is discussed. Refinements to the approach of using the pole-strength of Earth to evaluate the radius of the Earth's core-mantle boundary are reported. The downward extrapolation through the electrically conducting mantle was reviewed. Estimates of an upper bound for the time required for Earth's liquid core to overturn completely are presented. High order analytic approximations to the unsigned magnetic flux crossing the Earth's surface are also presented.
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
Progress in the use of MAGSAT data to confirm that the radius of the Earth's core-mantle boundary can be accurately determined magnetically is reported. The MAGSAT data was used in conjunction with a high quality manfield model for epoch 1965. The unsigned flux linking the core and mantle of the Earth is considered to be a legitimate invariant for a span of time. The value from MAGSAT of this constant is 16.056 GWb (gigawebers).
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
It was established that the total absolute magnetic flux crossing the core- mantle boundary has been a constant of the core motion for the last 50 years. This provides a scalar constraint that could be added to the geometric modelling procedure. The GSFC 8 8/80 model is being evaluated. The absolute magnetic flux linking the CMB to that model was plotted as a function of time during the span covered by the data, and increasing truncation level. The inclusion of the standard error of each Gauss coefficient derived from the statistics of fit in the GSFC 9/80 model is useful. The magnitude and sense (upwelling or downe welling) of vertical fluid motion adjacent to the core-mantle boundary was calculated using the model. Standard errors were found to be sufficiently small at all but one or two of the 40 or more critical points of B sub r. They do not nearly overlap the value gamma u/gamma r = 0. It is concluded that the core is upwelling and downwelling at an observationally detectable level.
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
Accomplishments to date were summarized in three parts submitted for publication. Goddard models and MAGSAT data were used heavily in the investigation which address: (1) the sensitivity of selected geomagnetic properties to truncation level of spherical harmonic expansions; (2) the pole strength of the Earth from MAGSAT, and magnetic determination of the core radius; and (3) frozen flux upper limits to the MAGSAT geomagnetic coefficients and relative multipole indices for Earth.
Benton, E. R.↗
Investigation of geomagnetic field forecasting and fluid dynamics of the core
Progress in the development, testing, and evaluation of kinematic geomagnetic forecast models and their utility in magnetic prediction of the core-mantle boundary of the Earth and in determination of the core radius is reported. The GFSC 9/80 model, which uses MAGSAT data, was determined to be of high quality.
Benton, E. R.↗
Core Formation Under Dynamic Conditions: Physical Processes and Geochemical Signatures
We have experimentally investigated liquid metal segregation from a solid silicate matrix under conditions of applied stress. Liquid moves in fractures and formation of fayalitic olivine from orthopyroxene by migrating Fe-Ni-S-O liquids is observed. Additional information is contained in the original extended abstract.
Rushmer, T.↗
Gas Sloshing and Radio Galaxy Dynamics in the Core of the 3C 449 Group
We present results from a 140 ks Chandra/ACIS-S observation of the hot gas around the canonical FR I radio galaxy 3C 449. An earlier, shorter 30 ks Chandra observation of the group gas showed an unusual entropy distribution and a surface brightness edge in the gas that could be a strong shock around the inner radio lobes. In our deeper data we find no evidence for a temperature increase inside of the brightness edge, but a temperature decrease across part of the edge. This suggests that the edge is a "sloshing" cold front due to a merger within the last 1.3-1.6 Gyr. Both the northern and southern inner jets are bent slightly to the west in projection as they enter their respective lobes, suggesting that the sloshing core is moving to the east. The straight inner jet flares at approximately the position where it crosses the contact edge, suggesting that the jet is entraining and thermalizing some of the hot gas as it crosses the edge.We also detect filaments of X-ray emission around the southern inner radio jet and lobe which we attribute to low entropy entrained gas. The lobe flaring and gas entrainment were originally predicted in simulations of Loken et al. and are confirmed in our deep observation.
Lal, Dharam V.↗
Microwave-induced dynamic switching of magnetic skyrmion cores in nanodots
The nonlinear dynamic behavior of a magnetic skyrmion in circular nanodots was studied numerically by solving the Landau-Lifshitz-Gilbert equation with a classical spin model. We show that a skyrmion core reversal can be achieved within nanoseconds using a perpendicular oscillating magnetic field. Two symmetric switching processes that correspond to excitations of the breathing mode and the mixed mode (combination of the breathing mode and a radial spin-wave mode) are identified. For excitation of the breathing mode, the skyrmion core switches through nucleation of a new core from a transient uniform state. In the mixed mode, the skyrmion core reverses with the help of spins excited both at the edge and core regions. Unlike the magnetic vortex core reversal, the excitation of radial spin waves does not dominate the skyrmion core reversal process.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
DYNAMICS OF MULTI-CORED MAGNETIC STRUCTURES IN THE QUIET SUN
We report on the dynamical interaction of quiet-Sun magnetic fields and granular convection in the solar photosphere as seen by Sunrise. We use high spatial resolution (0.″15–0.″18) and temporal cadence (33 s) spectropolarimetric Imaging Magnetograph eXperiment data, together with simultaneous CN and Ca ii H filtergrams from Sunrise Filter Imager. We apply the SIR inversion code to the polarimetric data in order to infer the line of sight velocity and vector magnetic field in the photosphere. The analysis reveals bundles of individual flux tubes evolving as a single entity during the entire 23 minute data set. The group shares a common canopy in the upper photospheric layers, while the individual tubes continually intensify, fragment and merge in the same way that chains of bright points in photometric observations have been reported to do. The evolution of the tube cores are driven by the local granular convection flows. They intensify when they are “compressed” by surrounding granules and split when they are “squeezed” between two moving granules. The resulting fragments are usually later regrouped in intergranular lanes by the granular flows. The continual intensification, fragmentation and coalescence of flux results in magnetic field oscillations of the global entity. From the observations we conclude that the magnetic field oscillations first reported by Martínez González et al. correspond to the forcing by granular motions and not to characteristic oscillatory modes of thin flux tubes.
79 ASTRONOMY AND ASTROPHYSICS↗
Spin-lattice dynamics of surface vs core magnetization in Fe nanoparticles
Magnetization of clusters is often simulated using atomistic spin dynamics for a fixed lattice. Coupled spinlattice dynamics simulations of the magnetization of nanoparticles have up to now neglected the change in the size of the atomic magnetic moments near surfaces. We show that the introduction of variable magnetic moments leads to a better description of experimental data for the magnetization of small Fe nanoparticles. To this end we divide atoms into a surface-near shell and a core with bulk properties. Here, it is demonstrated that both the magnitude of the shell magnetic moment and the exchange interactions need to be modified to obtain a fair representation of the experimental data. This allows for a reasonable description of the average magnetic moment versus cluster size, and also the cluster magnetization versus temperature.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Computational and Experimental Examination of Simulated Core Damage and Relocation Dynamics of a BWR Fuel Assembly - 16013
The Japan Atomic Energy Agency (JAEA) plans a large-scale test to evaluate damage and relocation behavior of Boiling Water Reactor (BWR) core materials consisting of fuel rods (zirconia as fuel simulant), channel boxes, control blade assemblies as well as lower core-support structures. Its purpose is to contribute to the understanding of the core material relocation behavior in the event of severe accidents with the BWR design conditions for which existing experimental database is quite limited. Prior to large-scale testing anticipated at JAEA in the future, JAEA desires preliminary investigations to examine melting test pieces, being composed of a mixture of zirconia and metals by a non-transferred thermal plasma heating system. The purpose of such tests is to verify the materials and test piece will be heated by plasma as a primary heat source to the target temperature of ca. 2900 K and to collect data about the relocation behavior of the high-temperature materials. This paper describes the first in a series of tests demonstrating the effective use of thermal plasma technology to recreate the dynamics of a typical fuel core bundle channel assembly section. Results from preliminary computational simulations of simplified fuel bundle assemblies are presented illustrating the effectiveness of a 150 kW, non transferred (NTR) configuration of a thermal plasma argon jet to heat the assembly within a highly-insulated containment vessel. An experimental test program using the computational analyses as a basis and a Phoenix Solutions Co (PSC) commercial model PT150, 150 kW plasma torch is described and the test results are presented illustrating the time versus temperature history of the fuel bundle assembly melting dynamics. Details on plasma operation are discussed including: power requirements, current flow, voltage levels achieved, argon gas flow rates, processing times and standoff distances of the torch discharge from the top of the fuel bundle assembly (achieved with remote control of the axial (vertical) translation of the torch within the containment processing chamber). Photos taken from the top of the processing chamber are presented illustrating the various phases of melting characteristics of the zircaloy-clad, zirconium oxide filled fuel tubes, all within a stainless steel tube bundle channel centered within an insulated zirconia crucible. Based on lessons learned from this initial test campaign, a brief discussion of the requirements and features of a follow-on Phase II test program is provided. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
A core–shell electrode for dynamically and statically stable Li–S battery chemistry
Sulfur is an appealing cathode material for establishing advanced lithium batteries as it offers a high theoretical capacity of 1675 mA h g -1 at low material and operating costs. However, the lithium–sulfur (Li–S) electrochemical cells face several formidable challenges arising from both the materials chemistry (e.g., low electrochemical utilization of sulfur and severe polysulfide diffusion) and battery chemistry (e.g., dynamic and static instability and low sulfur loadings). Here in this study, we present the design of a core–shell cathode with a pure sulfur core shielded within a conductive shell-shaped electrode. The new electrode configuration allows Li–S cells to load with a high amount of sulfur (sulfur loadings of up to 30 mg cm -2 and sulfur content approaching 70 wt%). The core–shell cathodes demonstrate a superior dynamic and static electrochemical stability in Li–S cells. The high-loading cathodes exhibit (i) a high sulfur utilization of up to 97% at C/20–C/2 rates and (ii) a low self-discharge during long-term cell storage for a three-month rest period and at different cell-storage conditions. Finally, a polysulfide-trap cell configuration is designed to evidence the eliminations of polysulfide diffusion and to investigate the relationship between the electrode configuration and electrochemical characteristics. Finally, the comprehensive analytical results based on the high-loading cathodes suggest that (i) the core–shell cathode is a promising solution for designing highly reversible Li–S cells and (ii) the polysulfide-trap cell configuration is a viable approach to qualitatively evaluating the presence or absence of polysulfide diffusion.
25 ENERGY STORAGE↗
Kernel fusion in atomistic spin dynamics simulations on Nvidia GPUs using tensor core
In atomistic spin dynamics simulations, the time cost of constructing the space- and time-displaced pair correlation function in real space increases quadratically as the number of spins N, leading to significant computational effort. The GEMM subroutine can be adopted to accelerate the calculation of the dynamical spin-spin correlation function, but the computational cost of simulating large spin systems (>40000 spins) on CPUs remains expensive. In this work, we perform the simulation on the graphics processing unit (GPU), a hardware solution widely used as an accelerator for scientific computing and deep learning. Here we show that GPUs can accelerate the simulation up to 25-fold compared to multi-core CPUs when using the GEMM subroutine on both. To hide memory latency, we fuse the element-wise operation into the GEMM kernel using CUTLASS that can improve the performance by 26% ~ 33% compared to implementation based on cuBLAS. Furthermore, we perform the on-the-fly calculation in the epilogue of the GEMM subroutine to avoid saving intermediate results on global memory, which makes the large-scale atomistic spin dynamics simulation feasible and affordable.
97 MATHEMATICS AND COMPUTING↗
Examination of the magnetism dynamics from intermixing effects in γ-Fe{sub 2}O{sub 3}/MnO core-shell nanoparticles
We have examined the effects of core-shell intermixing on the dynamical magnetism of γ-Fe{sub 2}O{sub 3}/MnO nanoparticles. The core and shell phases were identified using x-ray diffraction, and x-ray absorption spectroscopy identified Mn ions in both octahedral and tetrahedral sites, consistent with a significant amount of substitution at the core-shell interface to form an Fe/Mn-ferrite. The dynamical response was probed by Mössbauer spectroscopy, which decouples surface and core spins, and suggested a change in the relaxation behaviour among the spin populations within γ-Fe{sub 2}O{sub 3}/MnO relative to the γ-Fe{sub 2}O{sub 3} seed particles. Interestingly, the magnetic relaxation effects at the atomic scale, measured via Mössbauer spectroscopy, were enhanced, indicating that the addition of an MnO shell and intermixing affected the dynamical freezing process which altered the surface magnetism of the γ-Fe{sub 2}O{sub 3} core. Our results show that both the MnO shell and the interfacial intermixed layer are important in determining the core-shell nanoparticle magnetism.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗