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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Criticality Evaluation of Low Density Product Oxides for Air Transport for the ES-3100 Package

This document presents the criticality safety evaluation of the Y-12 National Security Complex (Y-12) Model ES-3100 package for the addition of lower bulk density limits for HEU product oxides transported by air. The current authorized oxide density range for air transport is 2.0 to 6.54 g/cm 3 . The analysis in this report looks at lower densities, specifically in the range of 1.0 to 2.0 g/cm 3 . For reasons presented in this report, it was decided to present the entire range of oxide densities (1.0 to 6.54 g/cm 3 ) as a series of sub-ranges. The lowest density in each range was evaluated. Thus calculations were performed for the following oxide densities: 5.0 g/cm 3 , 4.0 g/cm 3 , 3.0 g/cm 3 , 2.0 g/cm 3 , 1.5 g/cm 3 and 1.0 g/cm 3 . Calculations presented herein were performed using a third generation computing platform; the Microway Parallel Linux Cluster ENGHPC workstation using the Monte Carlo Criticality Safety Analysis Sequence (CSAS5) criticality code sequence and 238-group ENDF/B-VII cross-section library of Standardized Computer Analysis for Licensing Evaluation (SCALE) 6.1.3 (ORNL/TM-2005/39, SCALE: A Comprehensive Modeling and Simulation Suite for Nuclear Safety Analysis and Design).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Type-Ia supernova rates to redshift 2.4 from clash: The cluster lensing and supernova survey with Hubble

We present the supernova (SN) sample and Type-Ia SN (SN Ia) rates from the Cluster Lensing And Supernova survey with Hubble (CLASH). Using the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope (HST), we have imaged 25 galaxy-cluster fields and parallel fields of non-cluster galaxies. We report a sample of 27 SNe discovered in the parallel fields. Of these SNe, ∼13 are classified as SN Ia candidates, including four SN Ia candidates at redshifts z > 1.2. We measure volumetric SN Ia rates to redshift 1.8 and add the first upper limit on the SN Ia rate in the range 1.8 < z < 2.4. The results are consistent with the rates measured by the HST/GOODS and Subaru Deep Field SN surveys. We model these results together with previous measurements at z < 1 from the literature. The best-fitting SN Ia delay-time distribution (DTD; the distribution of times that elapse between a short burst of star formation and subsequent SN Ia explosions) is a power law with an index of −1.00{sub −0.06(0.10)}{sup +0.06(0.09)} (statistical){sub −0.08}{sup +0.12} (systematic), where the statistical uncertainty is a result of the 68% and 95% (in parentheses) statistical uncertainties reported for the various SN Ia rates (from this work and from the literature), and the systematic uncertainty reflects the range of possible cosmic star-formation histories. We also test DTD models produced by an assortment of published binary population synthesis (BPS) simulations. The shapes of all BPS double-degenerate DTDs are consistent with the volumetric SN Ia measurements, when the DTD models are scaled up by factors of 3-9. In contrast, all BPS single-degenerate DTDs are ruled out by the measurements at >99% significance level.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Templating Growth of a Pseudomorphic Lepidocrocite Microshell at the Calcite–Water Interface

The growth of lepidocrocite (gamma-FeOOH) has been observed through oxidation of Fe(II) on calcite (CaCO 3 ). Here, we seek to understand the structural relation between lepidocrocite and the calcite substrate and its growth mechanism. The formation of iron oxyhydroxide layers having distinct morphologies was observed during the dissolution of calcite in acidic Fe(II)-rich solutions. A pseudomorphic lepidocrocite shell together with multiple iron oxyhydroxide layers encapsulated within the shell was imaged by optical and transmission X-ray microscopies. The presence of a several-nanometer-thick ordered lepidocrocite film was observed by X-ray reflectivity, with the lepidocrocite (100) plane oriented parallel to the calcite (104) surface. Lath-shaped lepidocrocite aggregates formed during the initial precipitation, which eventually grew into clusters of parallel platy crystals. The formation of a nanometer-thick well-ordered lepidocrocite film on a pristine calcite surface appears critical for the subsequent pseudomorphic overgrowth. Detachment of the lepidocrocite film from the dissolving calcite surface yielded a free-standing pseudomorphic iron oxyhydroxide shell, suggesting weak interactions between the shell and the calcite substrate. This growth mechanism yields the potential of using carbonate minerals as templates for pseudomorphic synthesis of iron oxyhydroxides having well-defined size and morphology.

25 ENERGY STORAGE↗
DOE OSTI2018

HipMCL: a high-performance parallel implementation of the Markov clustering algorithm for large-scale networks

Biological networks capture structural or functional properties of relevant entities such as molecules, proteins or genes. Characteristic examples are gene expression networks or protein–protein interaction networks, which hold information about functional affinities or structural similarities. Such networks have been expanding in size due to increasing scale and abundance of biological data. While various clustering algorithms have been proposed to find highly connected regions, Markov Clustering (MCL) has been one of the most successful approaches to cluster sequence similarity or expression networks. Despite its popularity, MCL’s scalability to cluster large datasets still remains a bottleneck due to high running times and memory demands. In this paper, we present High-performance MCL (HipMCL), a parallel implementation of the original MCL algorithm that can run on distributed-memory computers. We show that HipMCL can efficiently utilize 2000 compute nodes and cluster a network of ~70 million nodes with ~68 billion edges in ~2.4 h. By exploiting distributed-memory environments, HipMCL clusters large-scale networks several orders of magnitude faster than MCL and enables clustering of even bigger networks. Finally, HipMCL is based on MPI and OpenMP and is freely available under a modified BSD license.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

ION INJECTION AT QUASI-PARALLEL SHOCKS SEEN BY THE CLUSTER SPACECRAFT

Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

STABILITY OF SMALL SELF-INTERSTITIAL CLUSTERS IN TUNGSTEN

Density functional theory was employed to explore the stability of interstitial clusters in W up to size seven. For each cluster size, the most stable configuration consists of parallel dumbbells. For clusters larger than size three, parallel dumbbells prefer to form in a multilayer fashion, instead of a planar structure. For size-7 clusters, the most stable configuration is a complete octahedron. The binding energy of a [111] dumbbell to the most stable cluster increases with cluster size, namely 2.49, 3.68, 4.76, 4.82, 5.47, and 6.85 eV for clusters of size 1, 2, 3, 4, 5, and 6, respectively. For a size-2 cluster, collinear dumbbells are still repulsive at the maximum allowable distance of 13.8 Å (the fifth neighbor along [111]). On the other hand, parallel dumbbells are strongly bound together. Two parallel dumbbells in which the axis-to-axis distance is within a cylindrical radius of 5.2 Å still exhibit a considerable binding of 0.28 eV. The most stable cluster in each size will be used to explore interactions with transmutation products.

density functional theory↗
DOE OSTI2016

Parallel File System I/O Performance Testing On LANL Clusters

These are slides from a presentation on parallel file system I/O performance testing on LANL clusters. I/O is a known bottleneck for HPC applications. Performance optimization of I/O is often required. This summer project entailed integrating IOR under Pavilion and automating the results analysis. The slides cover the following topics: scope of the work, tools utilized, IOR-Pavilion test workflow, build script, IOR parameters, how parameters are passed to IOR, *run_ior: functionality, Python IOR-Output Parser, Splunk data format, Splunk dashboard and features, and future work.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2013

Massively parallel implementations of coupled-cluster methods for electron spin resonance spectra. I. Isotropic hyperfine coupling tensors in large radicals

Coupled cluster (CC) methods provide highly accurate predictions of molecular properties, but their high computational cost has precluded their routine application to large systems. Fortunately, recent computational developments in the ACES III program by the Bartlett group [the OED/ERD atomic integral package, the super instruction processor, and the super instruction architecture language] permit overcoming that limitation by providing a framework for massively parallel CC implementations. In that scheme, we are further extending those parallel CC efforts to systematically predict the three main electron spin resonance (ESR) tensors (A-, g-, and D-tensors) to be reported in a series of papers. In this paper inaugurating that series, we report our new ACES III parallel capabilities that calculate isotropic hyperfine coupling constants in 38 neutral, cationic, and anionic radicals that include the {sup 11}B, {sup 17}O, {sup 9}Be, {sup 19}F, {sup 1}H, {sup 13}C, {sup 35}Cl, {sup 33}S,{sup 14}N, {sup 31}P, and {sup 67}Zn nuclei. Present parallel calculations are conducted at the Hartree-Fock (HF), second-order many-body perturbation theory [MBPT(2)], CC singles and doubles (CCSD), and CCSD with perturbative triples [CCSD(T)] levels using Roos augmented double- and triple-zeta atomic natural orbitals basis sets. HF results consistently overestimate isotropic hyperfine coupling constants. However, inclusion of electron correlation effects in the simplest way via MBPT(2) provides significant improvements in the predictions, but not without occasional failures. In contrast, CCSD results are consistently in very good agreement with experimental results. Inclusion of perturbative triples to CCSD via CCSD(T) leads to small improvements in the predictions, which might not compensate for the extra computational effort at a non-iterative N{sup 7}-scaling in CCSD(T). The importance of these accurate computations of isotropic hyperfine coupling constants to elucidate experimental ESR spectra, to interpret spin-density distributions, and to characterize and identify radical species is illustrated with our results from large organic radicals. Those include species relevant for organic chemistry, petroleum industry, and biochemistry, such as the cyclo-hexyl, 1-adamatyl, and Zn-porphycene anion radicals, inter alia.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Massively parallel GPU enabled third-order cluster perturbation excitation energies for cost-effective large scale excitation energy calculations

We present here a massively parallel implementation of the recently developed CPS(D-3) excitation energy model that is based on cluster perturbation theory. The new algorithm extends the one developed in Baudin et al. [J. Chem. Phys., 150, 134110 (2019)] to leverage multiple nodes and utilize graphical processing units for the acceleration of heavy tensor contractions. Furthermore, we show that the extended algorithm scales efficiently with increasing amounts of computational resources and that the developed code enables CPS(D-3) excitation energy calculations on large molecular systems with a low time-to-solution. More specifically, calculations on systems with over 100 atoms and 1000 basis functions are possible in a few hours of wall clock time. This establishes CPS(D-3) excitation energies as a computationally efficient alternative to those obtained from the coupled-cluster singles and doubles model.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Ad Hoc File Systems for High-Performance Computing

Storage backends of parallel compute clusters are still based mostly on magnetic disks, while newer and faster storage technologies such as flash-based SSDs or non-volatile random access memory (NVRAM) are deployed within compute nodes. Including these new storage technologies into scientific workflows is unfortunately today a mostly manual task, and most scientists therefore do not take advantage of the faster storage media. One approach to systematically include nodelocal SSDs or NVRAMs into scientific workflows is to deploy ad hoc file systems over a set of compute nodes, which serve as temporary storage systems for single applications or longer-running campaigns. This paper presents results from the Dagstuhl Seminar 17202 “Challenges and Opportunities of User-Level File Systems for HPC” and discusses application scenarios as well as design strategies for ad hoc file systems using node-local storage media. The discussion includes open research questions, such as how to couple ad hoc file systems with the batch scheduling environment and how to schedule stage-in and stage-out processes of data between the storage backend and the ad hoc file systems. Also presented are strategies to build ad hoc file systems by using reusable components for networking and how to improve storage device compatibility. Various interfaces and semantics are presented, for example those used by the three ad hoc file systems BeeOND, GekkoFS, and BurstFS. Their presentation covers a range from file systems running in production to cutting-edge research focusing on reaching the performance limits of the underlying devices.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Advances in Patch-Based Adaptive Mesh Refinement Scalability

Patch-based structured adaptive mesh refinement (SAMR) is widely used for high-resolution simu- lations. Combined with modern supercomputers, it could provide simulations of unprecedented size and resolution. A persistent challenge for this com- bination has been managing dynamically adaptive meshes on more and more MPI tasks. The dis- tributed mesh management scheme in SAMRAI has made some progress SAMR scalability, but early al- gorithms still had trouble scaling past the regime of 105 MPI tasks. This work provides two critical SAMR regridding algorithms, which are integrated into that scheme to ensure efficiency of the whole. The clustering algorithm is an extension of the tile- clustering approach, making it more flexible and efficient in both clustering and parallelism. The partitioner is a new algorithm designed to prevent the network congestion experienced by its prede- cessor. We evaluated performance using weak- and strong-scaling benchmarks designed to be difficult for dynamic adaptivity. Results show good scaling on up to 1.5M cores and 2M MPI tasks. Detailed timing diagnostics suggest scaling would continue well past that.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

The Importance of Three-Body Interactions in Molecular Dynamics Simulations of Water with the Fragment Molecular Orbital Method

The analytic first derivative with respect to nuclear coordinates is formulated and implemented in the framework of the three-body fragment molecular orbital (FMO) method. The gradient has been derived and implemented for restricted Hartree-Fock, second-order Møller-Plesset perturbation, and density functional theories. The importance of the three-body fully analytic gradient is illustrated through the failure of the two-body FMO method during molecular dynamics simulations of a small water cluster. The parallel implementation of the fragment molecular orbital method, its parallel efficiency, and its scalability on the Blue Gene/Q architecture up to 262,144 CPU cores, are also discussed.

Pruitt, Spencer R.↗
DOE OSTI2024

Accelerating science: The usage of commercial clouds in ATLAS Distributed Computing

The ATLAS experiment at CERN is one of the largest scientific machines built to date and will have ever growing computing needs as the Large Hadron Collider collects an increasingly larger volume of data over the next 20 years. ATLAS is conducting R&D projects on Amazon Web Services and Google Cloud as complementary resources for distributed computing, focusing on some of the key features of commercial clouds: lightweight operation, elasticity and availability of multiple chip architectures. The proof of concept phases have concluded with the cloud-native, vendoragnostic integration with the experiment’s data and workload management frameworks. Google Cloud has been used to evaluate elastic batch computing, ramping up ephemeral clusters of up to O(100k) cores to process tasks requiring quick turnaround. Amazon Web Services has been exploited for the successful physics validation of the Athena simulation software on ARM processors. We have also set up an interactive facility for physics analysis allowing endusers to spin up private, on-demand clusters for parallel computing with up to 4 000 cores, or run GPU enabled notebooks and jobs for machine learning applications. The success of the proof of concept phases has led to the extension of the Google Cloud project, where ATLAS will study the total cost of ownership of a production cloud site during 15 months with 10k cores on average, fully integrated with distributed grid computing resources and continue the R&D projects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functions with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ{sub UV}, at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ{sub UV} decrease trend can be reconciled with the large Thomson scattering optical depth, τ{sub e}, measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ{sub UV} decrease and the large τ {sub e}. It is possible that the ρ{sub UV} decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The sizes of z ∼ 6–8 lensed galaxies from the Hubble Frontier Fields Abell 2744 data

We investigate the sizes of z ∼ 6–8 dropout galaxies using the complete data of the Abell 2744 cluster and parallel fields in the Hubble Frontier Fields program. By directly fitting light profiles of observed galaxies with lensing-distorted Sérsic profiles on the image plane with the glafic software, we accurately measure intrinsic sizes of 31 z ∼ 6–7 and 8 z∼8 galaxies, including those as faint as M{sub UV}≃−16.6. We find that half-light radii r{sub e} positively correlates with UV luminosity at each redshift, although the correlation is not very tight. The largest (r{sub e}>0.8 kpc) galaxies are mostly red in UV color while the smallest (r{sub e}<0.08 kpc) ones tend to be blue. We also find that galaxies with multiple cores tend to be brighter. Combined with previous results at 2.5≲z≲12, our result confirms that the average r{sub e} of bright ((0.3–1)L{sub z=3}{sup ∗}) galaxies scales as r{sub e}∝(1+z){sup −m} with m=1.24±0.1. We find that the ratio of r{sub e} to virial radius is virtually constant at 3.3 ± 0.1% over a wide redshift range, where the virial radii of hosting dark matter halos are derived based on the abundance matching. This constant ratio is consistent with the disk formation model by Mo et al. with j{sub d}∼m{sub d}, where j{sub d} and m{sub d} are the fractions of the angular momentum and mass within halos confined in the disks. A comparison with various types of local galaxies indicates that our galaxies are most similar to circumnuclear star-forming regions of barred galaxies in the sense that a sizable amount of stars are forming in a very small area.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

psst: An open-source power system simulation toolbox in Python

This paper is an overview of Power System Simulation Toolbox (psst). psst is an open-source Python application for the simulation and analysis of power system models. psst simulates the wholesale market operation by solving a DC Optimal Power Flow (DCOPF), Security Constrained Unit Commitment (SCUC) and a Security Constrained Economic Dispatch (SCED). psst also includes models for the various entities in a power system such as Generator Companies (GenCos), Load Serving Entities (LSEs) and an Independent System Operator (ISO). psst features an open modular object oriented architecture that will make it useful for researchers to customize, expand, experiment beyond solving traditional problems. psst also includes a web based Graphical User Interface (GUI) that allows for user friendly interaction and for implementation on remote High Performance Computing (HPCs) clusters for parallelized operations. This paper also provides an illustrative application of psst and benchmarks with standard IEEE test cases to show the advanced features and the performance of toolbox.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

A Global Climate Model Agent for High Spatial and Temporal Resolution Data

Fine cell granularity in modern climate models can produce terabytes of data in each snapshot, causing significant I/O overhead. To address this issue, a method of reducing the I/O latency of high-resolution climate models by identifying and selectively outputting regions of interest is presented. Working with a Global Cloud Resolving Model and running with up to 10240 processors on a Cray XE6, this method provides significant I/O bandwidth reduction depending on the frequency of writes and size of the region of interest. The implementation challenges of determining global parameters in a strictly core-localized model and properly formatting output files that only contain subsections of the global grid are addressed, as well as the overall bandwidth impact and benefits of the method. The gains in I/O throughput provided by this method allow dual output rates for high-resolution climate models: a low-frequency global snapshot as well as a high-frequency regional snapshot when events of particular interest occur.

global cloud resolving model↗