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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A Task Based Approach for Co-Scheduling Ensemble Workloads on Heterogeneous Nodes

Scientific workflows consist of multiple, connected applications, with data and results flowing from one to another in a pipeline. Traditionally, such workflows are executed in sequential order, storing intermediate data in storage disks. Co-scheduling application workflows concurrently on the same compute nodes would greatly reduce the cost of moving data to/from storage and allow real-time analysis of intermediate results. Nevertheless, most parallel programming runtimes do not allow seamless integration of various applications in a scientific workflow, in part due to the complexity of managing data and resources. The situation is even more complicated for heterogeneous systems. In this work we extend the Minos Computing Library (MCL) runtime to accelerate pipe-lined and parallel workloads where multiple applications are running in the same system. MCL’s asynchronous task library and runtime dynamically manages resources to allow co-scheduling of multiple processes sharing heterogeneous resources. In addition, we design a custom ex- tension of the Open Compute Language (OpenCL) to enable multiple processes to share device memory. We enable MCL to coordinate these shared buffers to allow for easy, fast data sharing between applications. Using malleable micro-benchmarks and two application workflows that combine scientific simulation and AI-based analysis, we show that our method outperforms traditional approaches.

Index Terms—Parallel systems, Scheduling and Task ↗
DOE OSTI2018

Development of a Converter-Based Transmission Line Emulator with Three-Phase Short-Circuit Fault Emulation Capability

A transmission line emulator has been developed to flexibly represent interconnected ac lines under normal operating conditions in a voltage source converter (VSC)-based power system emulation platform. As the most serious short-circuit fault condition, the three-phase short-circuit fault emulation is essential for power system studies. Here, this paper proposes a model to realize a three-phase short-circuit fault emulation at different locations along a single transmission line or one of several parallel-connected transmission lines. At the same time, a combination method is proposed to eliminate the undesired transients caused by the current reference step changes while switching between the fault state and the normal state. Experiment results verify the developed transmission line three-phase short-circuit fault emulation capability.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

An experimentally validated electro-thermal EV battery pack model incorporating cycle-life aging and cell-to-cell variations

Lithium-ion batteries are used in a wide variety of applications. To meet the power and energy demands of these applications battery packs are composed of hundreds to thousands of cells. The electrical and thermal interactions between cells introduce additional complexity in the pack dynamics. To capture these effects, a battery pack model composed of 192 cells based on a first-generation (2012) Nissan Leaf battery pack is developed in MATLAB/Simulink/Simscape. Here, with this model, we simulate the electrical dynamics (using a first-order equivalent-circuit model), the thermal dynamics (using a first-order lumped-parameter thermal model), and the aging dynamics (using a semi-empirical severity factor-based model) of every cell in the pack and we also create a pack thermal model that explicitly captures the heat exchange between the modules, and the cells contained within, during operation. The models are calibrated and validated, both at the cell and pack level, with experimental data. Two different case studies of this pack model are investigated. In the first case study, an initial, normally-distributed, cell-to-cell capacity variation is introduced and its effect on the pack voltage and module temperatures is studied. In the second case study, we deliberately insert cells with lower than nominal capacity into the pack and we investigate how this type of initial cell-to-cell capacity variation affects the pack’s ability to deliver energy over time. Finally, we also study how parallel-connected cells can reduce the effects of cell-to-cell variations at the expense of increased aging of the pack overall.

25 ENERGY STORAGE↗
DOE OSTI2021

Stabilization of the 81-channel coherent beam combination using machine learning

We develop a rapidly converging algorithm for stabilizing a large channel-count diffractive optical coherent beam combination. An 81-beam combiner is controlled by a novel, machine-learning based, iterative method to correct the optical phases, operating on an experimentally calibrated numerical model. A neural-network is trained to detect phase errors based on interference pattern recognition of uncombined beams adjacent to the combined one. Due to the non-uniqueness of solutions in the full space of possible phases, the network is trained within a limited phase perturbation/error range. This also reduces the number of samples needed for training. Simulations have proven that the network can converge in one step for small phase perturbations. When the trained neural-network is applied to a realistic case of 360 degree full range, an iterative scheme exploits random walking at the beginning, with the accuracy of prediction on phase feedback direction, to allow the neural-network to step into the training range for fast convergence. This neural-network-based iterative method of phase detection works tens of times faster than the commonly used stochastic parallel gradient descent approach (SPGD) using a single-detector and random dither when both are tested with random phase perturbations.

Wang, Dan↗
DOE OSTI2018

Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures

The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.

Liu, Zhicong↗
DOE OSTI2021

MicroResonators for Compacts Optical Sensors (μRCOS)

As the demand for continuous, in-situ surveillance of health of systems and environments rapidly increases, miniaturized sensors with fast responses are sought. Optical dielectric resonators supporting Whispering Gallery Modes (WGMs) have exceptional properties, like very high-power density, very narrow spectral linewidth, and extremely small mode volume. As the footprint of these sensors is drastically reduced, measurements of microvolumes samples with dramatic reduction in analysis time are possible, enabling large numbers of parallel analyses using microarrays. The high sensitivity and speed of WGM resonators combined with the ability to detect molecules in their native state have great future potential for basic and applied research such as reliable single molecule, trace-gas detection, environmental monitoring, chemical threat sensing, and biodefense Such appealing peculiarities motivated us developing WMG resonators (WGMRs) for Cavity Enhanced Absorption Spectroscopy (CEAS) for chem-bio detection. Specifically, we designed and batch-fabricated microspheres and fiber tapers for resonances excitation. We successfully detected gases (N 2 and CO 2 ) in customized environmental chambers, and bio-organisms (Inf. A and E. Coli) with integrated microfluidic systems. Background calibration and environmental isolation were always accounted for in proving the performances.

36 MATERIALS SCIENCE↗
DOE OSTI2021

MicroResonators for Compacts Optical Sensors (μRCOS)

As the demand for continuous, in-situ surveillance of health of systems and environments rapidly increases, miniaturized sensors with fast responses are sought. Optical dielectric resonators supporting Whispering Gallery Modes (WGMs) have exceptional properties, like very high-power density, very narrow spectral linewidth, and extremely small mode volume. As the footprint of these sensors is drastically reduced, measurements of microvolumes samples with dramatic reduction in analysis time are possible, enabling large numbers of parallel analyses using microarrays. The high sensitivity and speed of WGM resonators combined with the ability to detect molecules in their native state have great future potential for basic and applied research such as reliable single molecule, trace-gas detection, environmental monitoring, chemical threat sensing, and biodefense Such appealing peculiarities motivated us developing WMG resonators (WGMRs) for Cavity Enhanced Absorption Spectroscopy (CEAS) for chem-bio detection. Specifically, we designed and batch-fabricated microspheres and fiber tapers for resonances excitation. We successfully detected gases (N 2 and CO 2 ) in customized environmental chambers, and bio-organisms (Inf. A and E. Coli) with integrated microfluidic systems. Background calibration and environmental isolation were always accounted for in proving the performances.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Implementation of a Particle Accelerator Beam Dynamics Code on Multi-Node GPUs

Particle accelerators play an important role in a wide range of scientific discoveries and industrial applications. The self-consistent multi-particle simulation based on the particle-in-cell (PIC) method has been used to study charged particle beam dynamics inside those accelerators. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high-resolution applications. In this paper, we implemented a parallel beam dynamics PIC code on multi-node hybrid architecture computers with multiple Graphics Processing Units (GPUs). We used two methods to parallelize the PIC code on multiple GPUs and observed that the replication method is a better choice for moderate problem size and current computer hardware while the domain decomposition method might be a better choice for large problem size and more advanced computer hardware that allows direct communications among multiple GPUs. Using the multi-node hybrid architectures at Oak Ridge Leadership Computing Facility (OLCF), the optimized GPU PIC code achieves a reasonable parallel performance and scales up to 64 GPUs with 16 million particles.

43 PARTICLE ACCELERATORS↗
NASA NTRS1971

An efficient parallel algorithm for the solution of a tridiagonal linear system of equations

Tridiagonal linear systems of equations are solved on conventional serial machines in a time proportional to N, where N is the number of equations. The conventional algorithms do not lend themselves directly to parallel computations on computers of the ILLIAC IV class, in the sense that they appear to be inherently serial. An efficient parallel algorithm is presented in which computation time grows as log sub 2 N. The algorithm is based on recursive doubling solutions of linear recurrence relations, and can be used to solve recurrence relations of all orders.

Stone, H. S.↗
NASA NTRS1972

Advanced missions safety. Volume 3: Appendices. Part 1: Space shuttle rescue capability

The space shuttle rescue capability is analyzed as a part of the advanced mission safety study. The subjects discussed are: (1) mission evaluation, (2) shuttle configurations and performance, (3) performance of shuttle-launched tug system, (4) multiple pass grazing reentry from lunar orbit, (5) ground launched ascent and rendezvous time, (6) cost estimates, and (7) parallel-burn space shuttle configuration.

Source record↗
NASA NTRS1975

A survey of long term interplanetary magnetic field variations

Interplanetary magnetic field data from 10 IMP, AIMP, and HEOS spacecraft were merged into a composite data set spanning 1963 to 1974. A consideration of the mutual consistency of the individual data sets reveals agreement typically to within 0.2 gamma. Composite data set analysis reveals: (1) whereas the yearly averaged magnitudes of all field vectors show virtually no solar cycle variation, the yearly averaged magnitudes of positive- and negative-polarity field vectors show separate solar cycle variations, consistent with variations in the average azimuthal angles of positive- and negative-polarity field vectors, (2) there is no heliolatitude dependence of long time average field magnitudes, (3) field vectors parallel to the earth-sun line are on the average 1 gamma less in magnitude than field vectors perpendicular to this line, and (4) the heliolatitude-dependent dominant polarity effect exhibits a complex sign reversal in the 1968 to 1971 period and a measure of symmetry in 1972 to 1974 not found in earlier data.

King, J. H.↗
NASA NTRS1976

A survey of long-term interplanetary magnetic field variations

Interplanetary-magnetic-field data from the IMP-10, IMP-A, and Heos spacecraft have been merged into a composite data set spanning the period from 1963 to 1974. Consideration of the mutual consistency of the individual data sets reveals agrement typically to within 0.2 gamma. Analysis of the composite data set reveals the following: (1) although the yearly averaged magnitudes of all field vectors show virtually no solar-cycle variation, the yearly averaged magnitudes of positive- and negative-polarity field vectors show separate solar-cycle variations consistent with variations in the average azimuthal angles of positive- and negative-polarity field vectors; (2) there is no solar latitude dependence of long-time average field magnitudes; (3) field vectors parallel to the earth-sun line are on the average 1 gamma less in magnitude than field vectors perpendicular to this line; and (4) the solar latitude-dependent dominant polarity effect exhibits a complex sign reversal in the period from 1968 to 1971 and a measure of symmetry in 1972 through 1974 not found in earlier data.

King, J. H.↗
NASA NTRS1981

Phenomena induced by charged particle beams

The injection of energetic particles along the Earth's magnetic field lines is a possible remote sensing method for measuring the electric fields parallel to the magnetic field with good time resolution over the entire magnetic field. Neutralization processes, return-current effects, dynamics of the beams, triggered instabilities, and waves must be investigated before the fundamental question about proper experimental conditions, such as energy, intensity and divergence of the beams, pitch-angle injection, ion species, proper probes and detectors and their location, and rendezvous conditions, can be resolved. An experiment designed to provide a better understanding of these special physical processes and to provide some answers to questions concerning beam injection techniques is described.

Beghin, C.↗
NASA NTRS1982

A preliminary assessment of the self-induced environment and contamination of the Space Telescope

Preliminary estimates for the internal pressures and surface contamination of the Space Telescope were made. The calculations for the transient pressures in the aft-shroud and telescope compartments considered two large communicating volumes that contain gaseous sources and sinks. The outgassing sources in the aft shroud consist of several scientific instruments, paints, insulations, and graphite-epoxy structures. With the exception of the instruments, these sources also exist in the telescope compartment. the outgassing functions were generated from ample test results at various temperatures and from internal pressure measurements in a vacuum test of one of the instruments. The venting occurs through combinations of series and parallel passages in both compartments. The calculated time constant of the two volumes and their respective passages, with the telescope protective door closed, is a few seconds, which is slightly less than that of the shuttle bay volume with the bay doors closed. With the telescope door closed, the pressures in the two compartments should decay to about 1OE-5 torr in about 200 hours. The contaminant deposits were assessed on the basis of expected partial pressures of the contaminant fraction of the outgassing. These pressures and the activation energies of the source materials were used to calculate the adsorbed and condensed deposits on the surfaces as a function of time.

Scialdone, J. J.↗
NASA NTRS1980

Parallel processing implementations of a contextual classifier for multispectral remote sensing data

Contextual classifiers are being developed as a method to exploit the spatial/spectral context of a pixel to achieve accurate classification. Classification algorithms such as the contextual classifier typically require large amounts of computation time. One way to reduce the execution time of these tasks is through the use of parallelism. The applicability of the CDC flexible processor system and of a proposed multimicroprocessor system (PASM) for implementing contextual classifiers is examined.

Siegel, H. J.↗
NASA NTRS1982

Geometric registration and rectification of spaceborne SAR imagery

This paper describes the development of automated location and geometric rectification techniques for digitally processed synthetic aperture radar (SAR) imagery. A software package has been developed that is capable of determining the absolute location of an image pixel to within 60 m using only the spacecraft ephemeris data and the characteristics of the SAR data collection and processing system. Based on this location capability algorithms have been developed that geometrically rectify the imagery, register it to a common coordinate system and mosaic multiple frames to form extended digital SAR maps. These algorithms have been optimized using parallel processing techniques to minimize the operating time. Test results are given using Seasat SAR data.

Curlander, J. C.↗
NASA NTRS1987

Real-time data compressor for Eos-class missions

A conceptual design for a real-time VLSI compressor capable of processing rate up to one gigabit per second is presented. This scheme is capable of providing a three-to-one distortion-free data reduction factor to both the High Resolution Imaging Spectrometer and processed SAR imaging data. The design uses a VLSI parallel/piplined architecture capable of processing at a real time rate. The design consists of a parallel array of VLSI compressor modules. Each module is built on a single customized VLSI chip using existing state-of-the-art semiconductor technology.

Lee, Jun-Ji↗