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Results for “distributed parallelization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Application of a distributed network in computational fluid dynamic simulations

A general-purpose 3-D, incompressible Navier-Stokes algorithm is implemented on a network of concurrently operating workstations using parallel virtual machine (PVM) and compared with its performance on a CRAY Y-MP and on an Intel iPSC/860. The problem is relatively computationally intensive, and has a communication structure based primarily on nearest-neighbor communication, making it ideally suited to message passing. Such problems are frequently encountered in computational fluid dynamics (CDF), and their solution is increasingly in demand. The communication structure is explicitly coded in the implementation to fully exploit the regularity in message passing in order to produce a near-optimal solution. Results are presented for various grid sizes using up to eight processors.

Deshpande, Manish↗
NASA NTRS1984

Effect of parallel refraction on magnetospheric upper hybrid waves

Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

Engel, J.↗
DOE OSTI2022

Modular Hybrid Solid State Transformer (H-SST) for Next Generation Flexible and Adaptable Large Power Transformer (LPT) (Final Technical Report)

A 500 kVA HSST, the world first of such system, has been successfully developed. The HSST has the capability to regulate the power flow of the transmission or distribution power lines, or provide voltage regulation. The HSST design is modular therefore it has the ability to be connected in series of parallel to form a large power transformer with smart controllability. The project has enabled a high TRL level prototype be demonstrated at University of Texas at Austin which can lead to additional commercialization and demonstration opportunities. A large number of students were trained under this program that will benefit the power grid industry. A number of publications are published at well known international conferences and journals, further accomplish the mission of knowledge development and dissemination.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2025

Stability Analysis of Parallel Connected Bidirectional WPT System

This paper presents a stability analysis of parallel-connected bi-directional series-series resonant network wireless power transfer (WPT), optimized for Electric Vehicle (EV) charging and vehicle-to-grid (V2G) applications. The study addresses critical stability challenges in systems integrated with diverse distributed energy resources (DERs), including photovoltaics, fuel cells, wind turbines, energy storage systems, and the AC grid. The stability of such integrated DC grid systems is paramount for ensuring reliable operation, particularly under varying power flow conditions and dynamic interactions between parallel WPT systems. The analysis included system impedance characterization, state-space modeling, and open and closed-loop stability evaluations. The results demonstrated that the integration of a robust control architecture effectively mitigates instability risks and supports scalable, efficient operation. This work underscores the converter's adaptability and its potential for large-scale deployment in wireless EV charging infrastructures and integrated DC grid systems.

Asa, Erdem [ORNL] (ORCID:0000000190884812)↗
DOE OSTI2023

Multi-dimensional incoherent Thomson scattering system in PHAse Space MApping (PHASMA) facility

A multi-dimensional incoherent Thomson scattering diagnostic system capable of measuring electron temperature anisotropies at the level of the electron velocity distribution function (EVDF) is implemented on the PHAse Space MApping facility to investigate electron energization mechanisms during magnetic reconnection. This system incorporates two injection paths (perpendicular and parallel to the axial magnetic field) and two collection paths, providing four independent EVDF measurements along four velocity space directions. For strongly magnetized electrons, a 3D EVDF comprised of two characteristic electron temperatures perpendicular and parallel to the local magnetic field line is reconstructed from the four measured EVDFs. As a result, validation of isotropic electrons in a single magnetic flux rope and a steady-state helicon plasma is presented.

47 OTHER INSTRUMENTATION↗
NASA NTRS1994

The effect of wave-particle interactions on the polar wind: Preliminary results

A Monte Carlo simulation was developed in order to study the effects of wave-particle interactions (WPI) on the plasma outflow in the polar wind. The simulation also considered the other mechanisms included in the `classical' polar wind studies such as gravity, the polarization electrostatic field, and the divergence of geomagnetic field lines. Although the plasma consisted of electrons, H(+) and O(+) ions, we emphasized the behavior of H(+) in this preliminary study. The ion distribution function, as well as the profiles of its moments (density, drift velocity, temperatures, etc.) were found for different levels of WPI, that is, for different values of normalized diffusion rates in the velocity space (normalized D(sub perpendicular) H(+)). We found that as the WPI strength increases: (1) the ion drift velocity increases and its density decreases; (2) the perpendicular temperature T(sub perpendicular) (H(+)) increases; (3) the parallel temperature T(sub parallel) (H(+)) first decreases and then increases due to the balance between the parallel adiabatic cooling and the transfer of the energy from the perpendicular to the parallel direction; and (4) the temperature anisotropy ((T(sub parallel) (H(+))/T(sub perpendicular) (H(+)) is reduced and even reversed in some cases. For strong WPI (normalized D(sub perpendicular) (H(+) much greater than 1), the ion distribution function shows weak conic features at high altitudes.

Barakat, A. R.↗
DOE OSTI2022

Relationships between fault characteristics and seismic responses in a large lab-scale tri-axial injection test conducted on a faulted Castlegate Sandstone

Here to investigate mechanisms causing microseismicity (M w < 2) at a CO 2 injection site, a large-scale triaxial block experiment was carried out on a faulted (saw-cut) cubic-meter of Castlegate Sandstone. The experiment consisted of injection tests at varying differential stresses, while monitoring and recording pore pressure and acoustic emissions (AEs). During the experiment, ~33,000 AEs and ~14 mm of horizontal displacement/slip, like a strike-slip fault movement, occurred. To understand the AE responses and ascertain fault characteristics near the located AEs, we modeled the topography of the fault surface, fault aperture, and fault-gouge thickness using pre- and post-experiment laser scans of the fault surface on each half of the block. Additionally, we characterized surface roughness parallel and perpendicular to slip. Models show crushing and flattening of the fault surfaces can be linked to the spatiotemporal distribution of AEs within 50 mm of the fault surface. Approximately 65% of AEs were in areas with small aperture (≤300 μm); thicker fault gouge was observed in adjacent areas with wider aperture and shows a two-fold reduction in grain size relative to unaltered Castlegate Sandstone. This work provides a conceptual understanding on fault surface evolution, which can be applied towards modeling of seismic slip.

58 GEOSCIENCES↗
DOE OSTI2022

Efficient Probabilistic Computing with Stochastic Perovskite Nickelates

Probabilistic computing has emerged as a viable approach to solve hard optimization problems. Devices with inherent stochasticity can greatly simplify their implementation in electronic hardware. In this report we demonstrate intrinsic stochastic resistance switching controlled via electric fields in perovskite nickelates doped with hydrogen. The ability of hydrogen ions to reside in various metastable configurations in the lattice leads to a distribution of transport gaps. With experimentally characterized p-bits, a shared-synapse p-bit architecture demonstrates highly parallelized and energy-efficient solutions to optimization problems such as integer factorization and Boolean satisfiability. The results introduce perovskite nickelates as scalable potential candidates for probabilistic computing and showcase the potential of light-element dopants in next-generation correlated semiconductors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

Evidence of topological charge polarization at active-passive interfaces in acoustically powered active liquid crystals

Theoretical and computational studies predict topological charge separation at active-passive interfaces in active nematics, but reliable experimental validation has been lacking. We utilize a synthetic acoustically energized liquid crystal to experimentally investigate the dynamics of topological defects across an active-passive interface. The interference pattern induced by the acoustic wave inside the experimental cell creates a spatial distribution of activity, resulting in the formation of active-passive interfaces with the liquid-crystalline director field aligned parallel to those interfaces. The activity gradient drives the reorientation of positively charged topological defects along its direction, causing them to migrate into the passive zone and form a layer with net topological charge. That layer “discharges” upon cessation of activity through annihilation of positive and negative topological charges, resembling the discharge of a capacitor.

Active defects↗
NASA NTRS1972

Diffusion of charged particles in a random magnetic field

When charged particles move in a random magnetic field superimposed upon a relatively large constant field, their pitch angle distribution can be calculated to any desired precision by an iterative approximation procedure. Improved knowledge of the pitch angle distribution and of the characteristic time for relaxation of anisotropy leads to an accurate expression for the coefficient of diffusion parallel to the mean field.

Earl, J. A.↗
NASA NTRS1973

Diffusion of charged particles in a random magnetic field.

When charged particles move in a random magnetic field superposed upon a relatively large constant field, their pitch-angle distribution can be calculated to any desired precision by an iterative approximation procedure. Improved knowledge of the pitch-angle distribution and of the characteristic time for relaxation of anisotropy leads to an accurate expression for the coefficient of diffusion parallel to the mean field.

Earl, J. A.↗
NASA NTRS1979

Anisotropies in the fluxes of Pioneer 10 protons

One-hour-averaged fluxes of 1.8- to 2.15-MeV protons observed by the LET2 detector on Pioneer 10 on the inbound trajectory showed anisotropies attributable to corotation of Jupiter's magnetodisc only when Pioneer was near the dipole equator. Most of the time the anisotropy greatly exceeded the value expected from corotation. Gradients in the distribution function can be used to account for this excess anisotropy, but the amount of gradient required is unacceptably large by 1-2 orders of magnitude. If they were taken as real, these gradients would predict almost complete disappearance of these protons from Jupiter's magnetosphere in a matter of hours. The remedy is to introduce into the model of the distribution function proton flow along field lines away from the equator into both the southern and the northern hemisphere. The parallel flux at the southernmost latitudes reached by Pioneer can reach 25% of the product of proton density and velocity, i.e., 25% of the maximum possible.

Northrop, T. G.↗
NASA NTRS1987

Optimal mapping of irregular finite element domains to parallel processors

Mapping the solution domain of n-finite elements into N-subdomains that may be processed in parallel by N-processors is an optimal one if the subdomain decomposition results in a well-balanced workload distribution among the processors. The problem is discussed in the context of irregular finite element domains as an important aspect of the efficient utilization of the capabilities of emerging multiprocessor computers. Finding the optimal mapping is an intractable combinatorial optimization problem, for which a satisfactory approximate solution is obtained here by analogy to a method used in statistical mechanics for simulating the annealing process in solids. The simulated annealing analogy and algorithm are described, and numerical results are given for mapping an irregular two-dimensional finite element domain containing a singularity onto the Hypercube computer.

Flower, J.↗
NASA NTRS1995

Ponderomotive effects on distributions of O(+) ions in the auroral zone

Test particle calculations are used to compute the effects of gravity and ponderomotive acceleration by shear Alfven wave oscillations on the distribution function of O(+) ions along auroral field lines, assuming an ionospheric Maxwellian source of the ions at 2000 km altitude with approximately 0.5 eV of thermal energy in the parallel component of velocity. The electric field model corresponds to a standing wave oscillation with a frequency approximately 1 Hz in the azimuthal direction superimposed on the background dipole field, in which the wave amplitude is either increasing or decreasing in time. The electric field is taken to be primarily in the perpendicular direction. The time varying wave produces broad distributions with widths of 2 to 10 times the initial 0.5-eV thermal energy of the Maxwellian source, and the density and flux of upward going O(+) ions at one Earth radius are both enhanced in this model. The oxygen ion distribution functions at 1 R(sub E) altitude resulting from interaction with waves whose amplitudes are increasing in time have a more gradual lower energy cutoff than do the distribution functions resulting from decaying waves. The high-energy part of the distribution functions in growing waves reflects the temperature of the Maxwellian source, while the high-energy part of the distributions resulting from decaying waves steepens with time, independent of the source temperature.

Witt, E.↗
NASA NTRS1996

Advanced optical disk storage technology

There is a growing need within the Air Force for more and better data storage solutions. Rome Laboratory, the Air Force's Center of Excellence for C3I technology, has sponsored the development of a number of operational prototypes to deal with this growing problem. This paper will briefly summarize the various prototype developments with examples of full mil-spec and best commercial practice. These prototypes have successfully operated under severe space, airborne and tactical field environments. From a technical perspective these prototypes have included rewritable optical media ranging from a 5.25-inch diameter format up to the 14-inch diameter disk format. Implementations include an airborne sensor recorder, a deployable optical jukebox and a parallel array of optical disk drives. They include stand-alone peripheral devices to centralized, hierarchical storage management systems for distributed data processing applications.

Haritatos, Fred N.↗
NASA NTRS1995

Optical Logarithmic Transformation of Speckle Images with Bacteriorhodopsin Films

The application of logarithmic transformations to speckle images is sometimes desirable in converting the speckle noise distribution into an additive, constant-variance noise distribution. The optical transmission properties of some bacteriorhodopsin films are well suited to implement such a transformation optically in a parallel fashion. I present experimental results of the optical conversion of a speckle image into a transformed image with signal-independent noise statistics, using the real-time photochromic properties of bacteriorhodopsin. The original and transformed noise statistics are confirmed by histogram analysis.

Downie, John D.↗
NASA NTRS1997

An Assessmant of a Beofulf System for a Wide Class of Analysis and Design Software

This paper discusses Beowulf systems, focusing on Hyglac, the Beowulf system installed at the Jet Propulsion Laboratory. The purpose of the paper is to assess how a system of this type will perform while running a variety of scientific and engineering analysis and design software.

communications measurement parallel performance me↗
NASA NTRS2016

The Substructure of a Flux Transfer Event Observed by the MMS Spacecraft

On 15 August 2015, MMS (Magnetospheric Multiscale mission), skimming the dusk magnetopause, detected an isolated region of an increased magnetic strength and bipolar Bn, indicating a flux transfer event (FTE). The four spacecraft in a tetrahedron allowed for investigations of the shape and motion of the FTE. In particular, high-resolution particle data facilitated our exploration of FTE substructures and their magnetic connectivity inside and surrounding the FTE. Combined field and plasma observations suggest that the core fields are open, magnetically connected to the northern magnetosphere from which high-energy particles leak; ion "D" distributions characterize the axis of flux ropes that carry old-opened field lines; counter streaming electrons superposed by parallel-heated components populate the periphery surrounding the FTE; and the interface between the core and draped regions contains a separatrix of newlyopened magnetic field lines that emanate from the X line above the FTE.

Hwang, K.-J.↗