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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Applying ASTM International C1421 to Glasses and Optical Ceramics

Fracture toughness is a critical structural design parameter and an excellent metric to rank structural materials. It determines fracture strength by way of the flaws, both inherent and induced, and defines the endpoint of the slow crack growth curve. The fracture toughness of glasses and structural and optical ceramics as measured by several techniques is compared. When good metrology is employed, the results are very comparable with two exceptions: materials exhibiting crack growth resistance and those with low SCG exponents. For materials exhibiting crack growth resistance (R-curve), the result is a function of extension and can be minimized with short cracks. For materials with low SCG exponents, such as glasses, elimination of the corrosive media and/or increasing the stress intensity rate minimizes effects. A summary of values is given for optical materials and glasses.

fracture toughness↗
NASA NTRS1978

Lunar Seismology: the Internal Structure of the Moon

The direct P and S wave arrival times are the primary data set that can be measured on the seismograms of natural lunar seismic events. Polarization filtering techniques allow the enhancement of secondary body wave arrivals and record curves to identify the secondary phases and deduce structural information. Finally, shear wave amplitude vs. distance curves yield information on the location and magnitude of seismic velocity gradients in the interior. The results of these analyses show that the moon appears to have a two-layer crust at all four seismic stations: a 20 km upper crust that seems to be constant at all sites and a lower crust that is 40 km thick at stations 12 and 14 (mare), 55 + or - 10 km at station 16 (highland), and tentatively either 40 km or 70 km at station 15. The lower mantle extends from 480 km to at least 1100 km depth which is the maximum depth of penetration of all but a few seismic waves used as data. No definitive evidence for or against a lunar core exists.

Goins, N. R.↗
DOE OSTI2020

Structure-Composition Subtleties in NaZn 13 -type Derivatives of Sr/Ca(Au x Al 1– x ) 12–13

In the ternary (Sr/Ca)-Au-Al phase space for 5–8 at % Sr/Ca and nearly equimolar mixture of Au and Al, five new NaZn 13 -derivatives Sr/Ca(Au x Al 1–x ) 12–13 were discovered and their atomic site preferences and electronic structures were studied: (1) at higher Au content, cubic SrAuxAl 13–x [7.24(2) ≥ x ≥ 6.68(2)] shows no obvious atomic site preferences; (2) at lower Au content, tetragonal SrAu x Al 13–x [6.59(1) ≥ x ≥ 6.35(3)] shows icosahedra exclusively centered by Al and preferential atomic arrangements to maximize the number of Au–Al (or Al-rich) shortest distances; (3) a monoclinic SrAu 6.10(3) Al 6.40 compound was uncovered from studies of a single crystal specimen with problematic refinement issues but more detailed powder X-ray diffraction analysis which suggest even more pronounced geometric distortion from the NaZn 13 -type structure as well as preferential arrangements for Au–Al nearest contacts; (4) tetragonal SrAu 5.75(2) Al 6.25 with all empty icosahedra; and (5) orthorhombic CaAu 6.09(2) Al 6.01(1) with icosahedra that are half empty and half partially occupied by Al. Electronic DOS and COHP curves were used to rationalize the structural depiction of Sr/Ca(Au x Al 1–x ) 12–13 as icosahedra packing of (Au x Al 1–x) 12–13 with voids filled by the electropositive Sr/Ca.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

Soil temperature extrema recovery rates after precipitation cooling

From a one dimensional view of temperature alone variations at the Earth's surface manifest themselves in two cyclic patterns of diurnal and annual periods, due principally to the effects of diurnal and seasonal changes in solar heating as well as gains and losses of available moisture. Beside these two well known cyclic patterns, a third cycle has been identified which occurs in values of diurnal maxima and minima soil temperature extrema at 10 cm depth usually over a mesoscale period of roughly 3 to 14 days. This mesoscale period cycle starts with precipitation cooling of soil and is followed by a power curve temperature recovery. The temperature recovery clearly depends on solar heating of the soil with an increased soil moisture content from precipitation combined with evaporation cooling at soil temperatures lowered by precipitation cooling, but is quite regular and universal for vastly different geographical locations, and soil types and structures. The regularity of the power curve recovery allows a predictive model approach over the recovery period. Multivariable linear regression models alloy predictions of both the power of the temperature recovery curve as well as the total temperature recovery amplitude of the mesoscale temperature recovery, from data available one day after the temperature recovery begins.

Welker, J. E.↗
DOE OSTI2022

Modeling the partitioning of amphiphilic molecules and co-solvents in biomembranes

We report amphiphilic co-solvents can have a significant impact on the structure, organization and physical properties of lipid bilayers. Describing the mutual impact of partitioning and induced structure changes is therefore a crucial consideration for a range of topics such as anesthesia and other pharmacokinetic effects, as well as microbial solvent tolerance in the production of biofuels and other fermentation products, where molecules such as ethanol, butanol or acetic acid might be generated. Small-angle neutron scattering (SANS) is a key method for studying lipid and polymer bilayer structures, with many models for extracting bilayer structure (thickness, area per lipid etc.) from scattering data in use today. However, the molecular details of co-solvent partitioning are conflated with induced changes to bilayer structure, making interpretation and modeling of the scattering curves a challenge with the existing set of models. To address this, a model of a bilayer structure is presented which invokes a two-term partition constant accounting for the localization of the co-solvent within the bilayer. This model was validated using a series of SANS measurements of lipid vesicles in the presence of the co-solvent tetrahydrofuran (THF), showing several strategies of how to deploy the two-parameter partition constant model to describe scattering data and extract both structure and partitioning information from the data. Molecular dynamics simulations are then used to evaluate assumptions of the model, provide additional molecular scale details and illustrate its complementary nature to the data fitting procedure. This approach results in estimates of the partition coefficient for THF in 1,2-dimyristoyl-sn-glycero-3-phosphocholine at 35°C, along with an estimate of the fraction of THF residing in the hydrophobic core of the membrane. The authors envision that this model will be applicable to a wide range of other bilayer/amphiphile interactions and provide the associated code needed to implement this model as a fitting algorithm for scattering data in the SasView suite.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Hybrid Quantum-Classical Neural Network for Calculating Ground State Energies of Molecules

We present a hybrid quantum-classical neural network that can be trained to perform electronic structure calculation and generate potential energy curves of simple molecules. The method is based on the combination of parameterized quantum circuits and measurements. With unsupervised training, the neural network can generate electronic potential energy curves based on training at certain bond lengths. To demonstrate the power of the proposed new method, we present the results of using the quantum-classical hybrid neural network to calculate ground state potential energy curves of simple molecules such as H 2 , LiH, and BeH 2 . The results are very accurate and the approach could potentially be used to generate complex molecular potential energy surfaces.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Studying Transient Phenomena in Thin Films with Reinforcement Learning

Neutron reflectometry has long been a powerful tool to study the interfacial properties of energy materials. Recently, time-resolved neutron reflectometry has been used to better understand transient phenomena in electrochemical systems. Those measurements often comprise a large number of reflectivity curves acquired over a narrow q range, with each individual curve having lower information content compared to a typical steady-state measurement. In this work, we present an approach that leverages existing reinforcement learning tools to model time-resolved data to extract the time evolution of structure parameters. Further, by mapping the reflectivity curves taken at different times as individual states, we use the Soft Actor-Critic algorithm to optimize the time series of structure parameters that best represent the evolution of an electrochemical system. We show that this approach constitutes an elegant solution to the modeling of time-resolved neutron reflectometry data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1976

Stellar occultation spikes as probes of atmospheric structure and composition

The characteristics of spikes observed in occultation light curves of Beta Scorpii by Jupiter are discussed in terms of the gravity-gradient model. The occultation of Beta Sco by Jupiter on May 13, 1971, is reviewed, and the gravity-gradient model is defined as an isothermal atmosphere of constant composition in which the refractivity is a function only of the radial coordinate from the center of refraction, which is assumed to lie parallel to the local gravity gradient. The derivation of the occultation light curve in terms of the atmosphere, the angular diameter of the occulted star, and the occultation geometry is outlined. It is shown that analysis of the light-curve spikes can yield the He/H2 concentration ratio in a well-mixed atmosphere, information on fine-scale atmospheric structure, high-resolution images of the occulted star, and information on ray crossing. Observational limits are placed on the magnitude of horizontal refractivity gradients, and it is concluded that the spikes are the result of local atmospheric density variations: atmospheric layers, density waves, or turbulence.

Elliot, J. L.↗
NASA NTRS1992

Data reduction using cubic rational B-splines

A geometric method is proposed for fitting rational cubic B-spline curves to data that represent smooth curves including intersection or silhouette lines. The algorithm is based on the convex hull and the variation diminishing properties of Bezier/B-spline curves. The algorithm has the following structure: it tries to fit one Bezier segment to the entire data set and if it is impossible it subdivides the data set and reconsiders the subset. After accepting the subset the algorithm tries to find the longest run of points within a tolerance and then approximates this set with a Bezier cubic segment. The algorithm uses this procedure repeatedly to the rest of the data points until all points are fitted. It is concluded that the algorithm delivers fitting curves which approximate the data with high accuracy even in cases with large tolerances.

Chou, Jin J.↗
NASA NTRS1974

The occultation of beta Scorpii by Jupiter. I - The structure of the Jovian upper atmosphere

The light curves of beta Scorpii AB and C were recorded during occultation by Jupiter with a time resolution of 0.01 sec. The spikes on the curves, correlated with flashes observed through the eyepiece, are shown to be due to density fluctuations in Jupiter's atmosphere. Using the delays in spike arrival times, the ratio of the refractivities at 3934 and 6201 A is found to be 0.9713 + or - 0.0015. Temperature profiles for three different assumed atmospheric compositions are generated from the light curves. Assuming the terrestrial value for the eddy diffusion coefficient, the turbopause is calculated to occur at the 10 to the 13th power per cu cm level, below which a positive temperature gradient of about 1 K/km is indicated.

Veverka, J.↗
NASA NTRS1984

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIX - The structure of the eclipsing Wolf-Rayet binary V444 Cygni as derived from light curves between 2460 A and 3. 5 microns

The WN5 component of V444 Cyg is characterized on the basis of light curves constructed using 1971 OAO observations at 425, 332, 298, and 246 nm and the broadband data at 2.2 and 3.5 microns of Hartmann (1978). Data and calculation results are presented in tables and graphs and discussed. Parameters estimated include core radius 2.9 solar radii, surface temperature 90,000 K, surface electron density 9 x 10 to the 12th/cu cm, surface outflow velocity 400 km/s, and terminal velocity (at about 10 solar radii) 2500 km/s, suggesting that the flow is He. These results are found to agree with the model of Wolf-Rayet atmospheres proposed by Beals (1929, 1944).

Cherepashchuk, A. M.↗
NASA NTRS2012

Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

Grimsley, Brian W.↗
DOE OSTI2017

Traction curves for the decohesion of covalent crystals

We study, by first principles, the energy versus separation curves for the cleavage of a family of covalent crystals with the diamond and zincblende structure. We find that there is universality in the curves for different materials which is chemistry independent but specific to the geometry of the particular cleavage plane. Since these curves do not strictly follow the universal binding energy relationship (UBER), we present a derivation of an extension to this relationship that includes non-linear force terms. This extended form of UBER allows for a flexible and practical mathematical description of decohesion curves that can be applied to the quantification of cohesive zone models.

Enrique, Raúl A. (ORCID:0000000280974125)↗
DOE OSTI2022

Intra-canopy leaf trait variation facilitates high LAI and compensatory growth in a clonal woody encroaching shrub in the tallgrass prairie

This data package contains the data for Tooley et al. (2022) Intra-canopy leaf trait variation facilitates high leaf area index and compensatory growth in a clonal woody encroaching shrub. The purpose of this project was to evaluate the leaf ecophysiological traits of Cornus drummondii C.A. Mey to better understand how C. drummondii maximizes photosynthetic rates across large gradients of light availability in its short, dense canopies. We also evaluate how C. drummondii modifies its allocation of leaf traits in response to grassland disturbance. High LAI canopies and a compensatory growth response to disturbance are two key factors contributing to the success of C. drummondii and other woody species responsible for the encroachment of grasslands.The data package contains ecophysiological measurements, including leaf morphological, physiological, and chemical traits; photosynthetic measurements, leaf carbon and nitrogen stable isotopes, leaf area index, and photosynthetically active radiation. All measurements were taken vertically across canopies of the clonal woody-encroaching shrub Cornus drummondii under browsed, grazed, and control (unbrowsed and ungrazed) conditions.Files:SeasonalMeasurements_Archive.csv - Data for all seasonal measurements used in the study.LeafPhotoSeasonalRaw_Archive.zip - zip file containing raw data from an li-6400 for each sampling period in the study.LAI_Archive.xlsx - Data for LAI Measurements.ACiandLightCurveResults_Archive.xlsx - Contains parameters extracted from A-ci and Light Response curves along with the morphological and chemical traits for each leaf.ACiRaw Archive.xlsx - Raw data from Li-6400 for A-ci response curvesLightCurves_Raw.zip - zip file containing raw data for Li-6400 light response curves. Excel file format: "IslandID"-"Depth"-lc.xlsx (or .csv)DataCollectionMethods.docx - file containing the methods of data collection, processing, and QA/QC for all data files. File also contains a list of excel file headers, abbreviations, and their units.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Blueprinting extendable nanomaterials with standardized protein blocks

A wooden house frame consists of many different lumber pieces, but because of the regularity of these building blocks, the structure can be designed using straightforward geometrical principles. The design of multicomponent protein assemblies, in comparison, has been much more complex, largely owing to the irregular shapes of protein structures. Here we describe extendable linear, curved and angled protein building blocks, as well as inter-block interactions, that conform to specified geometric standards; assemblies designed using these blocks inherit their extendability and regular interaction surfaces, enabling them to be expanded or contracted by varying the number of modules, and reinforced with secondary struts. Using X-ray crystallography and electron microscopy, we validate nanomaterial designs ranging from simple polygonal and circular oligomers that can be concentrically nested, up to large polyhedral nanocages and unbounded straight ‘train track’ assemblies with reconfigurable sizes and geometries that can be readily blueprinted. Because of the complexity of protein structures and sequence–structure relationships, it has not previously been possible to build up large protein assemblies by deliberate placement of protein backbones onto a blank three-dimensional canvas; the simplicity and geometric regularity of our design platform now enables construction of protein nanomaterials according to ‘back of an envelope’ architectural blueprints.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Actinide opacities for modelling the spectra and light curves of kilonovae

ABSTRACT We extend previous ab initio calculations of lanthanide opacities to include a complete set of actinide opacities for use in the modelling of kilonova (KN) light curves and spectra. Detailed, fine-structure line features are generated using the configuration-interaction approach. These actinide opacities display similar trends to those observed for lanthanide opacities, such as the lighter actinides producing higher opacity than the heavier ones for relevant conditions in the dynamical ejecta. A line-binned treatment is employed to pre-compute opacity tables for 14 actinide elements (89 ≤ Z ≤ 102) over a grid of relevant temperatures and densities. These tabular opacities will be made publicly available for general usage in KN modelling. We demonstrate the usefulness of these opacities in KN simulations by exploring the sensitivity of light curves and spectra to different actinide abundance distributions that are predicted by different nuclear theories, as well as to different choices of ejecta mass and velocity. We find very little sensitivity to the two considered distributions, indicating that opacities for actinides with Z ≥ 99 do not contribute strongly. On the other hand, a single actinide element, protactinium, is found to produce faint spectral features in the far-infrared at late times (5–7 d post merger). More generally, we find that the choice of ejecta mass and velocity have the most significant effect on KN emission for this study.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

The effect of CO 2 -induced dissolution on flow properties in Indiana Limestone: An in situ synchrotron X-ray micro-tomography study

The injection of CO 2 -rich fluids in carbonate rocks results in an evolution of the pore space, with consequent changes in the hydraulic properties of the reservoir; how these properties evolve, particularly for parameters relevant to multiphase flow e.g. P c (s), remains a topic of active research despite several decades of study. We have carried out an in situ synchrotron X-ray microtomography experiment to monitor pore structure evolution during dissolution of an Indiana Limestone core; the experiment involved flowing CO 2 -saturated water through the core for 36 h and resulted in 10 volumes corresponding to different temporal stages of the dissolution process. The injection parameters corresponded to the flow velocities expected near the well-bore region of a shallow aqueous CO 2 injection; fast flow rates with high reactant availability. Analysis of the tomographic data shows flow-enhanced dissolution i.e. channeling, and provides a time-resolved map of pore space alteration. Using the resulting 4D pore space volume, we modeled the evolution of capillary-pressure curves; this exercise demonstrates how pore structure evolution could impact the invasion and remobilization of non-wetting fluids, dramatically decreasing the entry pressure and the P C in some parts of the sample. The modeling of permeability, using a Stokes solver approach, quantified the relationship of porosity vs. permeability; we found that a modest increase in porosity, especially when the channeling system is more developed, greatly affects permeability. Furthermore, these results demonstrate how movement of CO 2 saturated brine near injected plumes might alter drainage dynamics near the plume boundary, thus leading to mobilization across subtle capillary barriers.

58 GEOSCIENCES↗
DOE OSTI2022

Probabilistic inversion of circular phase spectra: application to two-station phase-velocity dispersion estimation in western Canada

SUMMARY Periodic directional and temporal measurements are common in seismology, and necessitate specific statistical analyses that are appropriate for circular quantities. In this work, we explore the use of a von Mises distribution as a representation of errors on circular seismological observations. Specifically, we automate the estimation of surface-wave phase-velocity dispersion for the teleseismic two-station method, which generally suffers from a 2π phase ambiguity. The use of Bayesian inverse techniques, which aim to rigorously quantify model parameter uncertainty, have become widespread throughout seismology over the last decade. Here, we apply Bayesian inversion to measurements of surface-wave phase spectra in order to estimate 1-D, path-averaged Earth structure between station pairs. The dispersion curve and associated uncertainties are additional results of the inversion, which can then be used as input for subsequent analyses (e.g. tomography). We demonstrate this technique through application to surface-wave recordings from long-running seismic stations throughout western Canada. Our results for over 10 000 station pairs reveal first-order tectonic features consistent with previous studies, which provides confidence in our approach as well as an initial step towards resolving a full 3-D seismic velocity model for the region. This work also presents a foundation for the inversion of surface-wave phase spectra to estimate 3-D Earth structure directly. Finally, the ideas presented in this work are not limited to the inversion of surface-wave phase spectra, but can also be considered for Bayesian geophysical inversion of any circular quantities.

Gosselin, Jeremy M. (ORCID:0000000203754102)↗