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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Glass Property-Composition Models Update for use in Direct Feed High-Level Waste Flowsheet Development: EWG2.6

A set of preliminary glass property models and constraints were developed and augmented by models from literature for use in design of direct-feed high-level waste (DFHLW) glasses for flowsheet evaluation, testing, and design of the Waste Treatment and Immobilization Plant (WTP) high-level waste (HLW) Facility. These models and constraints are meant to be used as a place-holder while glass property-composition data gaps are filled and final plant operating models are developed. This report describes the motivation and intended use of the models, the compilation of data, model fitting and selection, methods to apply the models and constraints in glass design and offers example calculations demonstrating their intended use.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1976

Galilean satellites - Observations of mutual occultations and eclipses in 1973

Seven Galilean satellite mutual events, two occultations and two eclipses of Europa and three eclipses of Io, were observed at three wavelengths (0.35, 0.50, 0.91 micrometers) with a time resolution of 0.1 sec. Preliminary model fits to the light curves are presented. Model satellites with different albedo distributions (uniform disk, bright solar caps, bright quadrant) are used in generating model occultation and eclipse curves to demonstrate the sensitivity of observed light curves to the brightness distribution on the surface of the occulted or eclipsed satellite. At the present the observations yield no conclusive information of the limb-darkening of Io. The best data for Europa indicate that the satellite is limb-darkened at both 0.50 and 0.91 micrometers.

Wasserman, L. H.↗
NASA NTRS1979

The phase of the ten-hour modulation in the Jovian magnetosphere /Pioneers 10 and 11/

The paper describes the study of the phase of the 10-hour modulation of energetic electrons seen by Pioneers 10 and 11 in the Jovian magnetosphere. Attention is given to the peaks rather than the valleys of each cycle because the peaks are where physically interesting features occur, such as particle acceleration, current sheets, etc. To identify the peaks, it is required that the instantaneous intensity be higher than the 5-hour running average and the 5-hour running average be greater than the 10-hour running average. These criteria select an interval rather than a point and it is determined that this interval is an appropriate estimate of the experimental uncertainty. When the phases of the peaks are plotted together, they create patterns which are discussed in terms of disk-like, clock-like, and rotating anomaly models of the magnetosphere. Each model fits some of the data, but no model explains all of the data convincingly. It is concluded that there is still no understanding of the configuration of the outer Jovian magnetosphere.

Fillius, W.↗
NASA NTRS1988

Interacting binary galaxies. V - NGC 4782/4783 (3C 278): Unbound colliders, not a supermassive pair

CCD imaging data of the elliptical galaxies NGC 4782 and NGC 4783 have been analyzed along with published spectroscopic measurements in order to develop a viable interaction model for this system. The best-fit model suggests that the binary orbit was hyperbolic before the encounter, but that the energy loss during the collision has led to a loosely bound system. The total system mass in the region occupied by the luminous matter is shown to be 1.4 x 10 to the 12th solar masses. The results support the previous theory that the internal velocity dispersions of colliding galaxies tend to increase just past closest approach.

Borne, Kirk D.↗
NASA NTRS2020

Chandra spectral measurements of the O supergiant ζ Puppis indicate a surprising increase in the wind mass-loss rate over 18 yr

New long Chandra grating observations of the O supergiant ζ Pup show not only a brightening of the X-ray emission line flux of 13 per cent in the 18 yr since Chandra’s first observing cycle, but also clear evidence – at more than 4σsignificance – of increased wind absorption signatures in its Doppler-broadened line profiles. We demonstrate this with non-parametric analysis of the profiles as well as Gaussian fitting and then use line-profile model fitting to derive a mass-loss rate of 2.47±0.09×10−6Myr−1, which is a 40 per cent increase over the value obtained from the cycle 1 data. The increase in the individual emission line fluxes is greater for short-wavelength lines than long-wavelength lines, as would be expected if a uniform increase in line emission is accompanied by an increase in the wavelength-dependent absorption by the cold wind in which the shock-heated plasma is embedded.

David H. Cohen↗
NASA NTRSDate not supplied

Marin County Wildland Fires: Examining Fuel Load and Land Cover Change to Inform Fire Prevention and Suppression Decisions in Marin County, CA

Heightened occurrence of severe wildfires in the Western United States is increasing the need to better understand regions of high potential wild fire severity and develop methodologies for identifying the best locations for fuels reduction and active wildfire suppression, especially in populated regions such as Marin County, California. Marin County, located in the San Francisco Bay Area, has had significant development in the wildland-urban interface and periods of highly wildfire-prone conditions. The NASA DEVELOP team collaborated with Fire Foundry, a Marin-based fire service work force development program, to develop new models to assist with fire management. Using data from Sentinel-2A, Planet Scope, ECOSTRESS, a county-wide LiDAR mapping effort, Landsat 7 Enhanced Thematic Mapper (ETM+), and Landsat 8 Operational Land Imager (OLI), the team developed several input data layers to three models evaluating wild fire severity. One model performed a suitability analysis with weights based on scientific literature, another utilized machine learning based on past fires in Marin and neighboring Sonoma County to predict the difference normalized burn ratio, and the third inputted data layers into the Flam Map tool, which outputs risk categories. The team compared model outputs and, using the best-fit model, performed fuzzy logic analysis to identify specific locations where a fire break could be constructed to interrupt the progress of an active fire. These tools were proven useful and will assist partners in preparing for and managing an active wildfire event.

Suhani Dalal↗
DOE OSTI2016

Multiscale Investigation of Thermal Transport in UO{sub 2} Fuel using Modeling and Simulation

The thermal conductivity of the UO{sub 2} fuel in light water reactors (LWRs) defines how efficiently heat is transported from the fuel to the coolant, and thus directly influences the reactor efficiency. Unfortunately, the same fission events that generate heat also cause radiation damage and fission product formation that decreases the thermal conductivity. This reduction in thermal conductivity reduces the safety of the reactor in addition to its efficiency, because excess heat generated during an accident cannot be transported from the fuel, resulting in high temperatures that can result in melting. Because thermal conductivity plays such an important role in reactor efficiency and safety, many experiments have been conducted to measure the thermal conductivity of UO{sub 2} and how it changes during reactor operation. Experiments on unirradiated fuel have resulted in a large set of data indicating how the bulk thermal conductivity changes as a function of temperature, which was used to develop a semiempirical model. Additional experiments have been conducted to determine how the thermal conductivity of UO{sub 2} changes as a function of burnup, leading to burnup dependent models fitted to the data. While these empirical models perform well within the conditions at which the data was collected, they cannot be extrapolated outside of those conditions. In addition, while burnup is a measure of the amount of fissioning that has occurred, it cannot account for the impact of the operating conditions on the thermal conductivity. While experimental data provides an empirical view on the value of the thermal conductivity in the fuel during reactor operation, a more mechanistic understanding of how temperature and burnup impact the transport of heat through the fuel would be extremely valuable. Such an understanding would allow for a more accurate prediction of fuel performance, but it could also be used to direct modifications to the fuel that would raise the thermal conductivity or reduce the impact of burnup. In this work we summarize recent efforts to use modeling and simulation at the atomistic and mesoscales to obtain a mechanistic understanding of thermal transport in UO{sub 2}. The thermal conductivity of LWR fuel is one of the most critical material parameters impacting the efficiency and safety of the reactor. Thus, a significant effort is being made to develop a mechanistic understanding of the impact of temperature and burnup on it. In this work, we have provided a short summary of modeling and simulation efforts being carried out at the atomistic and mesoscale to understand this critical property. These research efforts are providing a fundamental understanding of the thermal transport in unirradiated UO{sub 2}, as well as the impact of radiation damage and fission products on thermal transport. These efforts have been focused on UO{sub 2}, but they also are laying the framework for conducted similar simulations to investigate new accident tolerant fuel concepts. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1981

Voyager 1 assessment of Jupiter's planetary magnetic field

An estimate of Jupiter's planetary magnetic field is obtained from the Voyager 1 observations of the Jovian magnetosphere. An explicit model for the magnetodisc current system is combined with a spherical harmonic model of the planetary field with both sets of parameters determined simultaneously using a nonlinear generalized inverse methodology. The resulting model fits the observations extremely well throughout the analysis interval (r 20 Jovian radii). The Jovian internal field model obtained from the Voyager 1 data is very similar to the octopole Pioneer 11 models. The best fitting magnetodisc lies in the centrifugal equator, 2/3 of the way between the rotational and magnetic equators, as appropriate for centrifugal loading of the magnetosphere by a cold plasma.

Connerney, J. E. P.↗
DOE OSTI2019

Material Testing for Shear-Dominated Ductile Failure

An initial foray into the design of specimens that can be used to provide data about the quasistatic ductile failure of metals when subjected to shear-dominated (low triaxiality) states of stress was undertaken. Four specimen geometries made from two materials with different ductility (Al 7075, lower ductility and steel A286, higher ductility) were considered as candidates. Based on results from analysis and experimentation, it seems that two show promise for further consideration. Whereas preliminary results indicate that the Johnson-Cook model fit the failure data for Al 7075 well, it did not fit the data for steel A286. Further work is needed to consolidate the results and evaluate other failure models that may fit the steel data better, as well as to extend the results of this work to the dynamic loading regime.

36 MATERIALS SCIENCE↗
DOE OSTI2015

What Does The PAMELA Antiproton Spectrum Tell Us About Dark Matter?

Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. Depending on the assumptions made regarding cosmic ray propagation in the Galaxy, such constraints can be quite stringent. We revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. We derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. We also note (as have several previous groups) that simple GALPROP-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with PAMELA's observations above ~ 5 GeV, but that significantly underpredict the flux at lower energies. Although the complexity of modeling cosmic ray propagation at GeV-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. Suggestively, we find that this excess is best fit for m(DM) ~ 35 GeV and σ v ~ 10(−)(26) cm(3)/s (to bbar b), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the Galactic Center.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Soil Dust Aerosols and Wind as Predictors of Seasonal Meningitis Incidence in Niger

Epidemics of meningococcal meningitis are concentrated in sub-Saharan Africa during the dry season, a period when the region is affected by the Harmattan, a dry and dusty northeasterly trade wind blowing from the Sahara into the Gulf of Guinea. We examined the potential of climate-based statistical forecasting models to predict seasonal incidence of meningitis in Niger at both the national and district levels. We used time series of meningitis incidence from 1986 through 2006 for 38 districts in Niger. We tested models based on data that would be readily available in an operational framework, such as climate and dust, population, and the incidence of early cases before the onset of the meningitis season in January–May. Incidence was used as a proxy for immunological state, susceptibility, and carriage in the population. We compared a range of negative binomial generalized linear models fitted to the meningitis data. At the national level, a model using early incidence in December and averaged November–December zonal wind provided the best fit (pseudo-R2 = 0.57), with zonal wind having the greatest impact. A model with surface dust concentration as a predictive variable performed indistinguishably well. At the district level, the best spatiotemporal model included zonal wind, dust concentration, early incidence in December, and population density (pseudo-R2 = 0.41). We showed that wind and dust information and incidence in the early dry season predict part of the year-to-year variability of the seasonal incidence of meningitis at both national and district levels in Niger. Models of this form could provide an early-season alert that wind, dust, and other conditions are potentially conducive to an epidemic.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Hydrothermal but Not Mechanical Pretreatment of Wastewater Algae Enhanced Anaerobic Digestion Energy Balance due to Improved Biomass Disintegration and Methane Production Kinetics

This study used pilot-scale high-rate algae ponds to assess algal–bacteria biomass productivity and wastewater nutrient removal as well as the impact of mechanical and hydrothermal pretreatments on biomass disintegration, methane production kinetics, and anaerobic digestion (AD) energy balance. Mechanical pretreatment had a minor effect on biomass disintegration and methane production. By contrast, hydrothermal pretreatment significantly reduced particle size and increased the solubilized organic matter content by 3.5 times. The methane yield and production rate increased by 20–55% and 20–85%, respectively, with the highest values achieved after pretreatment at 121 °C for 60 min. While the 1st-order and pseudo-1st-order reaction equation models fitted methane production from untreated biomass best (R2 > 0.993), the modified Gompertz sigmoidal-type model provided a superior fit for hydrothermally pretreated algae (R2 ≥ 0.99). The AD energy balance revealed that hydrothermal pretreatment improved the total energy output by 25–40%, with the highest values for volume-specific and mass-specific total energy outputs reaching 0.23 kW per digester m3 and 2.3 MW per ton of biomass volatile solids. Additionally, net energy recovery (energy output per biomass HHV) increased from 20% for untreated algae to 32–34% for hydrothermally pretreated algae, resulting in net energy ratio and net energy efficiency of 2.14 and 68%, respectively.

09 BIOMASS FUELS↗
DOE OSTI2015

USING MULTIPLE-VIEWPOINT OBSERVATIONS TO DETERMINE THE INTERACTION OF THREE CORONAL MASS EJECTIONS OBSERVED ON 2012 MARCH 5

We examine the interaction of three coronal mass ejections (CMEs) that took place on 2012 March 5 at heights less than 20 R{sub ⊙} in the corona. We used a forward fitting model to reconstruct the three-dimensional trajectories and kinematics of the CMEs and determine their interaction in the observations from three viewpoints: Solar and Heliospheric Observatory (SOHO), STEREO-A, and STEREO-B. The first CME (CME-1), a slow-rising eruption near disk center, is already in progress at 02:45 UT when the second CME (CME-2) erupts from AR 11429 on the east limb. These two CMEs are present in the corona not interacting when a third CME (CME-3) erupts from AR 11429 at 03:34 UT. CME-3 has a constant velocity of 1456[±31] km s{sup −1} and drives a shock that is observed as a halo from all viewpoints. We find that the shock driven by CME-3 passed through CME-1 with no observable change in the geometry, trajectory, or velocity of CME-1. However, the elevated temperatures detected in situ when CME-1 reached Earth indicate that the plasma inside CME-1 may have been heated by the passage of the shock. CME-2 is accelerated by CME-3 to more than twice its initial velocity and remains a separate structure ahead of the CME-3 front. CME-2 is deflected 24° northward by CME-3 for a total deflection of 40° from its source region. These results suggest that the collision of CME-2 and CME-3 is superelastic. This work demonstrates the capability and utility of fitting forward models to complex and interacting CMEs observed in the corona from multiple viewpoints.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

A Nonempirical Relative Permeability Model for Hydrate-Bearing Sediments

There are currently two types of relative permeability models that are used to model gas production from hydrate-bearing sediments: fully empirical parameter-fitting models [such as the University of Tokyo model (Masuda et al. 1997) and the Brooks and Corey model (Brooks and Corey 1964)] and partially empirical models [such as the Kozeny and Carman model (Wyllie and Gardner 1958) and capillary-tube-based models that assume only a single phase]. This study proposes an analytical model to estimate relative permeability of gas and water in a hydrate-bearing porous medium without curve fitting or use of any empirical parameters. The model is derived by conserving the momentum balance with the steady-state form of the Navier-Stokes equation for gas/water flow in a hydrate-bearing porous medium. The model is validated against a number of laboratory studies and is shown to perform better than most empirical models over a full range of experimental data. The proposed model is an analytical function of rock properties (average pore size and shape, porosity, irreducible water saturation, and saturation of hydrate), fluid properties (gas/water saturations and viscosities), and the hydrate-growth pattern [pore filling (PF), wall coating (WC), and a combination of PF and WC]. Here, the benefits of the proposed model include sensitivity analysis of relevant physical parameters on relative permeability and estimation of rock parameters (such as porosity, pore size, and residual water saturation) using inverse modeling. The model can also be used to estimate two-phase permeability in a permeable medium without hydrates.

58 GEOSCIENCES↗
DOE OSTI2020

High-contrast Thermal Infrared Spectroscopy with ALES: The 3–4 μm Spectrum of κ Andromedae b

We present the first L-band (2.8–4.1 μm) spectroscopy of κ Andromedae b, a ~20 M Jup companion orbiting at 1" projected separation from its B9-type stellar host. We combine our Large Binocular Telescope (LBT) Arizona Lenslets for Exoplanet Spectroscopy (ALES) integral field spectrograph data with measurements from other instruments to analyze the atmosphere and physical characteristics of κ And b. We report a discrepancy of ~20% (2σ) in the L' flux of κ And b when comparing to previously published values. We add an additional L' constraint using an unpublished imaging data set collected in 2013 using the LBT Interferometer/LMIRCam, the instrument in which the ALES module has been built. The LMIRCam measurement is consistent with the ALES measurement, both suggesting a fainter L-band scaling than previous studies. The data, assuming the flux scaling measured by ALES and LMIRCam imaging, are well fit by an L3-type brown dwarf. Atmospheric model fits to measurements spanning 0.9–4.8 μm reveal some tension with the predictions of evolutionary models, but the proper choice of cloud parameters can provide some relief. In particular, models with clouds extending to very low pressures composed of grains ≤1 μm appear to be necessary. If the brighter L' photometry is accurate, there is a hint that subsolar metallicity may be required.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

CONSTRAINT-INDEPENDENT CONSTANT CTOA DETERMINATION FOR DUCTILE STABLE CRACK GROWTH

Crack tip opening angle (CTOA) has been used as a reliable fracture toughness parameter for decades to characterize stable ductile crack growth for thin-walled aerospace structures in the low-constraint conditions. Recently, the CTOA parameter was also applied to the pipeline industry, and a CTOA test standard ASTM E3039 was thus developed for testing a critical constant CTOA. Research showed that the constant CTOA can reasonably describe fracture toughness required to arrest a dynamic crack propagation for a modern gas pipeline. However, the CTOA fracture criterion requires constraint-independent CTOA toughness against stable ductile crack growth. ASTM E3039 recommends a drop weight tearing test (DWTT) specimen for CTOA testing. Since a shallow crack is used, DWTT measured CTOA may depend on constraint level at the crack tip. To understand if it is the case, this paper evaluates the critical CTOA for a set of fracture toughness tests on single edge notched bend (SENB) specimens with shallow and deep cracks based on four CTOA estimation models. In which, the Ln(P)-LLD linear fit model is similar to that used by ASTM E3039 in the CTOA calculation. Fracture test data for X80 pipeline steel and HY80 structural steel are considered in the CTOA evaluation. The results show that the four CTOA models can determine a crack size-independent constant CTOA over stable ductile crack growth for the SENB specimens. As a result, CTOA determined by ASTM E3039 is constraintindependent and transferable to use for an actual crack propagating in a gas pipeline.

Zhu, Xian-Kui↗
DOE OSTI2026

Glass Property-Composition Models Update for use in Direct Feed High-Level Waste Flowsheet Development: EWG3.0

A set of preliminary glass property models and constraints were developed and augmented by models from literature for use in design of Direct Feed High-Level Waste glasses for flowsheet evaluation, testing, and design of the High-Level Waste Facility at the Hanford Waste Treatment and Immobilization Plant. These models and constraints are meant to be used as a placeholder while glass property-composition data gaps are filled and final plant operating models are developed. This report describes the motivation and intended use of the models, the compilation of data, model fitting and selection, and methods to apply the models and constraints in glass design, and offers example calculations demonstrating their intended use.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗