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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Zn(H3C)2 by Materials Project

Zn(CH3)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four dimethylzinc molecules. Zn2+ is bonded in a linear geometry to two equivalent C4- atoms. Both Zn–C bond lengths are 1.94 Å. C4- is bonded to one Zn2+ and three H1+ atoms to form corner-sharing CZnH3 tetrahedra. All C–H bond lengths are 1.10 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. The H–C bond length is 1.10 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. The H–C bond length is 1.10 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Neural network-based single material beam-hardening correction for X-ray CT in Additive Manufacturing

Beam-hardening (BH) artifacts are ubiquitous in X-ray CT scans of dense metal additively manufactured (AM) parts. While linearization approaches are useful for correcting beam-hardened data from single material objects, they either require a calibration scan or detailed system and material composition information. In this paper, we introduce a neural network-based, material-agnostic method to correct beam-hardening artifacts. We train a neural network to map the acquired beam-hardened projection values and the corresponding estimated thickness of the part based on an initial segmentation to beam-hardening related parameters, which can be used to compute the coefficients of a linearizing correction polynomial. A key strength of our approach is that, once the network is trained, it can be used for correcting beam hardening from a variety of materials without any calibration scans or detailed system and material composition information. Furthermore, our method is robust to errors in the estimated thickness due to the typical challenge of obtaining an accurate initial segmentation from reconstructions impacted by BH artifacts. We demonstrate the utility of our method to obtain high-quality CT reconstructions from a collection of AM parts -- suppressing cupping and streaking artifacts

Rahman, Obaid↗
DOE OSTI2023

An accurate and efficient Ehrenfest dynamics approach for calculating linear and nonlinear electronic spectra

Linear and nonlinear electronic spectra provide an important tool to probe the absorption and transfer of electronic energy. Here, we introduce a pure state Ehrenfest approach to obtain accurate linear and nonlinear spectra that is applicable to systems with large numbers of excited states and complex chemical environments. We achieve this by representing the initial conditions as sums of pure states and unfolding multi-time correlation functions into the Schrödinger picture. By doing this, we show that one can obtain significant improvements in accuracy over the previously used projected Ehrenfest approach and that these benefits are particularly pronounced in cases where the initial condition is a coherence between excited states. While such initial conditions do not arise when calculating linear electronic spectra, they play a vital role in capturing multidimensional spectroscopies. We demonstrate the performance of our method by showing that it is able to quantitatively capture the exact linear, 2D electronic spectroscopy, and pump–probe spectra for a Frenkel exciton model in slow bath regimes and is even able to reproduce the main spectral features in fast bath regimes.

Chemistry↗
DOE OSTI2020

Block Krylov Subspace Methods for Functions of Matrices II: Modified Block FOM

We analyze an expansion of the generalized block Krylov subspace framework of [Electron. Trans. Numer. Anal., 47 (2017), pp. 100--126]. This expansion allows the use of low-rank modifications of the matrix projected onto the block Krylov subspace and contains, as special cases, the block GMRES method and the new block Radau--Arnoldi method. Within this general setting, we present results that extend the interpolation property from the nonblock case to a matrix polynomial interpolation property for the block case, and we relate the eigenvalues of the projected matrix to the latent roots of these matrix polynomials. Some error bounds for these modified block FOM methods for solving linear systems are presented. We then show how cospatial residuals can be preserved in the case of families of shifted linear block systems. This result is used to derive computationally practical restarted algorithms for block Krylov approximations that compute the action of a matrix function on a set of several vectors simultaneously. Finally, we prove some error bounds and present numerical results showing that two modifications of FOM, the block harmonic and the block Radau--Arnoldi methods for matrix functions, can significantly improve the convergence behavior.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Evolution of the SLATE linear algebra library

SLATE (Software for Linear Algebra Targeting Exascale) is a distributed, dense linear algebra library targeting both CPU-only and GPU-accelerated systems, developed over the course of the Exascale Computing Project (ECP). While it began with several documents setting out its initial design, significant design changes occurred throughout its development. In some cases, these were anticipated: an early version used a simple consistency flag that was later replaced with a full-featured consistency protocol. In other cases, performance limitations and software and hardware changes prompted a redesign. Sequential communication tasks were parallelized; host-to-host MPI calls were replaced with GPU device-to-device MPI calls; more advanced algorithms such as Communication Avoiding LU and the Random Butterfly Transform (RBT) were introduced. Early choices that turned out to be cumbersome, error prone, or inflexible have been replaced with simpler, more intuitive, or more flexible designs. Applications have been a driving force, prompting a lighter weight queue class, nonuniform tile sizes, and more flexible MPI process grids. Of paramount importance has been building a portable library that works across several different GPU architectures – AMD, Intel, and NVIDIA – while keeping a clean and maintainable codebase. Here we explore the evolving design choices and their effects, both in terms of performance and software sustainability.

Gates, Mark↗
DOE OSTI2022

In-Situ Laser-Induced-Desorption-Spectroscopy Diagnostic Deployment on the Linear Plasma Device CSDX

A calibrated laser induced desorption diagnostic (LIDS) concept is developed under this award for application to fusion relevant plasma materials interactions studies. Small areal amounts of hydrogenic release from a deuterium filled PMI target are measured and quantified when irradiated by a LID flash heat event on the target surface. Good success was demonstrated by this project with the PISCES-E rf plasma device at UCSD by fully quantified measurement and removal of D from W-D co-deposit layers in experiments. However, adapting the LIDS technique to D plasma exposed W targets in the linear plasma CSDX device, now labelled PISCES-Rf, was prone to several technical challenges ranging from target line of sight access, laser focusing, and loss of optical spectroscopic signal strength in the larger PISCES-Rf vacuum system. The results are summarized in this report.

08 HYDROGEN↗
DOE OSTI2022

Computational Imaging for Intelligence in Highly Scattering Aerosols (Final Report)

Natural and man-made degraded visual environments pose major threats to national security. The random scattering and absorption of light by tiny particles suspended in the air reduces situational awareness and causes unacceptable down-time for critical systems and operations. To improve the situation, we have developed several approaches to interpret the information contained within scattered light to enhance sensing and imaging in scattering media. These approaches were tested at the Sandia National Laboratory Fog Chamber facility and with tabletop fog chambers. Computationally efficient light transport models were developed and leveraged for computational sensing. The models are based on a weak angular dependence approximation to the Boltzmann or radiative transfer equation that appears to be applicable in both the moderate and highly scattering regimes. After the new model was experimentally validated, statistical approaches for detection, localization, and imaging of objects hidden in fog were developed and demonstrated. A binary hypothesis test and the Neyman-Pearson lemma provided the highest theoretically possible probability of detection for a specified false alarm rate and signal-to-noise ratio. Maximum likelihood estimation allowed estimation of the fog optical properties as well as the position, size, and reflection coefficient of an object in fog. A computational dehazing approach was implemented to reduce the effects of scatter on images, making object features more readily discernible. We have developed, characterized, and deployed a new Tabletop Fog Chamber capable of repeatably generating multiple unique fog-analogues for optical testing in degraded visual environments. We characterized this chamber using both optical and microphysical techniques. In doing so we have explored the ability of droplet nucleation theory to describe the aerosols generated within the chamber, as well as Mie scattering theory to describe the attenuation of light by said aerosols, and correlated the aerosol microphysics to optical properties such as transmission and meteorological optical range (MOR). This chamber has proved highly valuable and has supported multiple efforts inclusive to and exclusive of this LDRD project to test optics in degraded visual environments. Circularly polarized light has been found to maintain its polarization state better than linearly polarized light when propagating through fog. This was demonstrated experimentally in both the visible and short-wave infrared (SWIR) by imaging targets made of different commercially available retroreflective films. It was found that active circularly polarized imaging can increase contrast and range compared to linearly polarized imaging. We have completed an initial investigation of the capability for machine learning methods to reduce the effects of light scattering when imaging through fog. Previously acquired experimental long-wave images were used to train an autoencoder denoising architecture. Overfitting was found to be a problem because of lack of variability in the object type in this data set. The lessons learned were used to collect a well labeled dataset with much more variability using the Tabletop Fog Chamber that will be available for future studies. We have developed several new sensing methods using speckle intensity correlations. First, the ability to image moving objects in fog was shown, establishing that our unique speckle imaging method can be implemented in dynamic scattering media. Second, the speckle decorrelation over time was found to be sensitive to fog composition, implying extensions to fog characterization. Third, the ability to distinguish macroscopically identical objects on a far-subwavelength scale was demonstrated, suggesting numerous applications ranging from nanoscale defect detection to security. Fourth, we have shown the capability to simultaneously image and localize hidden objects, allowing the speckle imaging method to be effective without prior object positional information. Finally, an interferometric effect was presented that illustrates a new approach for analyzing speckle intensity correlations that may lead to more effective ways to localize and image moving objects. All of these results represent significant developments that challenge the limits of the application of speckle imaging and open important application spaces. A theory was developed and simulations were performed to assess the potential transverse resolution benefit of relative motion in structured illumination for radar systems. Results for a simplified radar system model indicate that significant resolution benefits are possible using data from scanning a structured beam over the target, with the use of appropriate signal processing.

58 GEOSCIENCES↗
DOE OSTI2022

Final Report: Next Generation Diamond Drumhead X-Ray Optics

Problem / Opportunity Statement: Future high-impact scientific applications at synchrotron and Free-Electron Laser (FEL) X-ray sources require the development of processing and mounting methods for ultra-thin diamond crystals to meet the most challenging needs of pioneering research at next generation light source facilities. These methods should be capable of manufacturing crystal plates as thin as 10 micrometers over an area of a few mm2, and with a surface cut in different crystal orientations, such as the diamond {100}, {111}, {110} and {113} planes. Project Purpose and Approach: In Phase I, Great Lakes Crystal Technologies (GLCT) partnered with Stonybrook University (SUNY) to created thin diamond drumhead crystals. The purpose of the Phase I project is to transfer the drumhead membrane window etching technology from SUNY to GLCT. Testing of a device using the beamline at Stanford Linear Accelerator Laboratory was initially planned, however, a delay on the part of a third party service provided required us to get beamline testing done at Argonne National Laboratory. Phase I Taskwork: Testing of a high purity diamond plate thinning and etching process was performed. By SUNY and GLCT. Plates were sent to a third party service provider for thinning to ~100 microns, however, delays required that GLCT develop an in-house thinning process to complete the taskwork. GLCT successfully developed this in-house capability even though it was initially planned to be part of the Phase II Taskwork. Multiple practice and deliverable plates were provided to SUNY to be etched into the target drumhead devices. GLCT practiced and refined an in-house plate thinning process and produced five plates with thicknesses in the 60 – 150 micron range. Processing of the plates has begun and will continue in a no-cost extension period necessitated by the third party service provider delay. GLCT also procured and installed a reactive ion etching/inductively coupled plasma system. In addition, one of the thinned plates was measured at the Applied Photon Source at APL for a pre-processing assessment of the crystalline strain. After processing the plate into a drumhead and annealing, a post-processing assessment of the strain will be performed. Phase I Results: The initial data from GLCT’s plate thinning process development, SUNY’s drumhead etching processing, and characterization at APS/ANL demonstrate our teams capabilities to achieve the project goals. Commercial Applications & Benefits: The proposed technology will benefit advanced x-ray science performed at BNL and the 70+ additional advanced beamlines around the world. There are also a number of medical and homeland security applications which could benefit from the technology.

Quayle, Paul↗
DOE OSTI2020

Density weighted angular redshift fluctuations: a new cosmological observable

We propose the use of angular fluctuations in the galaxy redshift field as a new way to extract cosmological information in the Universe. This new probe $\delta z (\hat{\mathbf {n}})$ consists of the statistics of sky maps built by projecting redshifts under a Gaussian window of width σz centred upon a redshift zobs, and weighted by the galaxy density field. We compute the angular power spectrum of the $\delta z (\hat{\mathbf {n}})$ field in both numerical simulations and in linear perturbation theory. From these, we find that the $\delta z (\hat{\mathbf {n}})$ field (i) is sensitive to the underlying density and peculiar velocity fields; (ii) is highly correlated, at the $\gtrsim 60\, {{\ \rm per\ cent}}$ level, to the line-of-sight projected peculiar velocity field; (iii) for narrow windows (σz < 0.03), it is almost completely uncorrelated to the projected galaxy angular density field under the same redshift window; and (iv) it is largely unaffected by multiplicative and additive systematic errors on the observed number of galaxies that are redshift-independent over ~σz. We conclude that $\delta z (\hat{\mathbf {n}})$ is a simple and robust tomographic measure of the cosmic density and velocity fields, complementary to angular clustering, that will contribute to more complete exploitations of current and upcoming galaxy redshift surveys.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on Na5CuSO2 by Materials Project

Na5CuSO2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a linear geometry to four equivalent S2- and two equivalent O2- atoms. All Na–S bond lengths are 3.24 Å. Both Na–O bond lengths are 2.29 Å. In the second Na1+ site, Na1+ is bonded in a 2-coordinate geometry to two equivalent S2- and two equivalent O2- atoms. Both Na–S bond lengths are 3.02 Å. Both Na–O bond lengths are 2.31 Å. Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.81 Å. S2- is bonded to twelve Na1+ atoms to form SNa12 cuboctahedra that share corners with four equivalent SNa12 cuboctahedra, faces with four equivalent SNa12 cuboctahedra, and faces with eight equivalent ONa5Cu octahedra. O2- is bonded to five Na1+ and one Cu1+ atom to form ONa5Cu octahedra that share corners with six equivalent ONa5Cu octahedra and faces with four equivalent SNa12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–16°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na5CoSO2 by Materials Project

Na5CoSO2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a linear geometry to four equivalent S2- and two equivalent O2- atoms. All Na–S bond lengths are 3.26 Å. Both Na–O bond lengths are 2.28 Å. In the second Na1+ site, Na1+ is bonded in a distorted linear geometry to two equivalent S2- and two equivalent O2- atoms. Both Na–S bond lengths are 3.05 Å. Both Na–O bond lengths are 2.33 Å. Co1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Co–O bond lengths are 1.77 Å. S2- is bonded to twelve Na1+ atoms to form SNa12 cuboctahedra that share corners with four equivalent SNa12 cuboctahedra, faces with four equivalent SNa12 cuboctahedra, and faces with eight equivalent ONa5Co octahedra. O2- is bonded to five Na1+ and one Co1+ atom to form ONa5Co octahedra that share corners with six equivalent ONa5Co octahedra and faces with four equivalent SNa12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–14°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2PbO2 by Materials Project

Ag2PbO2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.12 Å. In the second Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.13 Å. Pb2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. There are two shorter (2.28 Å) and two longer (2.47 Å) Pb–O bond lengths. O2- is bonded to two Ag1+ and two equivalent Pb2+ atoms to form a mixture of distorted edge and corner-sharing OAg2Pb2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlCu7S4 by Materials Project

TlCu7S4 crystallizes in the tetragonal P4/n space group. The structure is three-dimensional. there are four inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a linear geometry to two equivalent S2- atoms. Both Cu–S bond lengths are 2.19 Å. In the second Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.26–2.78 Å. In the third Cu1+ site, Cu1+ is bonded in a trigonal non-coplanar geometry to three S2- atoms. There are two shorter (2.35 Å) and one longer (2.36 Å) Cu–S bond lengths. In the fourth Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to three S2- atoms. There are a spread of Cu–S bond distances ranging from 2.27–2.37 Å. There are two inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded in a body-centered cubic geometry to eight S2- atoms. There are four shorter (3.30 Å) and four longer (3.33 Å) Tl–S bond lengths. In the second Tl1+ site, Tl1+ is bonded in a body-centered cubic geometry to eight S2- atoms. All Tl–S bond lengths are 3.33 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Cu1+ and two Tl1+ atoms. In the second S2- site, S2- is bonded in a 8-coordinate geometry to six Cu1+ and two Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3N by Materials Project

Li3N crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a linear geometry to two equivalent N3- atoms. Both Li–N bond lengths are 1.94 Å. In the second Li1+ site, Li1+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All Li–N bond lengths are 2.11 Å. N3- is bonded to eight Li1+ atoms to form a mixture of corner and edge-sharing NLi8 hexagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li7Br3O2 by Materials Project

Li7O2Br3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a linear geometry to two equivalent O2- and four Br1- atoms. Both Li–O bond lengths are 1.99 Å. There are two shorter (2.84 Å) and two longer (2.88 Å) Li–Br bond lengths. In the second Li1+ site, Li1+ is bonded in a distorted single-bond geometry to one O2- and five equivalent Br1- atoms. The Li–O bond length is 1.93 Å. All Li–Br bond lengths are 2.82 Å. In the third Li1+ site, Li1+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent Br1- atoms. Both Li–O bond lengths are 2.01 Å. All Li–Br bond lengths are 2.82 Å. O2- is bonded to six Li1+ atoms to form OLi6 octahedra that share corners with five equivalent OLi6 octahedra and faces with four equivalent BrLi12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded to twelve Li1+ atoms to form BrLi12 cuboctahedra that share corners with four equivalent BrLi12 cuboctahedra, faces with four equivalent BrLi12 cuboctahedra, and faces with eight equivalent OLi6 octahedra. In the second Br1- site, Br1- is bonded in a 9-coordinate geometry to nine Li1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2PbO2 by Materials Project

PbCu2O2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. In the second Cu1+ site, Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. Pb2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. There are two shorter (2.31 Å) and two longer (2.52 Å) Pb–O bond lengths. O2- is bonded to two Cu1+ and two equivalent Pb2+ atoms to form a mixture of distorted corner and edge-sharing OCu2Pb2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on P2PbAu2 by Materials Project

Au2PbP2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Au2+ sites. In the first Au2+ site, Au2+ is bonded in a linear geometry to two equivalent P3- atoms. Both Au–P bond lengths are 2.38 Å. In the second Au2+ site, Au2+ is bonded in a distorted T-shaped geometry to one Pb2+ and two equivalent P3- atoms. The Au–Pb bond length is 2.93 Å. Both Au–P bond lengths are 2.36 Å. Pb2+ is bonded in a single-bond geometry to one Au2+ atom. P3- is bonded to two Au2+ and two equivalent P3- atoms to form corner-sharing PP2Au2 tetrahedra. Both P–P bond lengths are 2.23 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca7Tl3N2 by Materials Project

Ca7Tl3N2 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are four inequivalent Ca sites. In the first Ca site, Ca is bonded in a linear geometry to four Tl and two equivalent N atoms. There are two shorter (3.49 Å) and two longer (3.60 Å) Ca–Tl bond lengths. Both Ca–N bond lengths are 2.48 Å. In the second Ca site, Ca is bonded in a single-bond geometry to six equivalent Tl and one N atom. There are two shorter (3.43 Å) and four longer (3.49 Å) Ca–Tl bond lengths. The Ca–N bond length is 2.33 Å. In the third Ca site, Ca is bonded in a linear geometry to four equivalent Tl and two equivalent N atoms. All Ca–Tl bond lengths are 3.48 Å. Both Ca–N bond lengths are 2.56 Å. In the fourth Ca site, Ca is bonded in a linear geometry to four Tl and two equivalent N atoms. There are two shorter (3.50 Å) and two longer (3.65 Å) Ca–Tl bond lengths. Both Ca–N bond lengths are 2.45 Å. There are two inequivalent Tl sites. In the first Tl site, Tl is bonded to twelve Ca atoms to form TlCa12 cuboctahedra that share corners with twelve TlCa12 cuboctahedra, faces with six TlCa12 cuboctahedra, and faces with eight equivalent NCa6 octahedra. In the second Tl site, Tl is bonded to ten Ca and two equivalent Tl atoms to form distorted TlCa10Tl2 cuboctahedra that share corners with eight TlCa12 cuboctahedra, corners with two equivalent NCa6 octahedra, edges with four equivalent TlCa10Tl2 cuboctahedra, faces with seven TlCa12 cuboctahedra, and faces with four equivalent NCa6 octahedra. The corner-sharing octahedral tilt angles are 45°. Both Tl–Tl bond lengths are 3.29 Å. N is bonded to six Ca atoms to form NCa6 octahedra that share corners with two equivalent TlCa10Tl2 cuboctahedra, corners with five equivalent NCa6 octahedra, and faces with eight TlCa12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°.

36 MATERIALS SCIENCE↗