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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Prediction Based Design of Fire Detection for Buildings with Ceiling Heights between 9m and 18m

The purpose of this paper is to provide the experimental and theoretical background necessary to extend guidelines to ceiling heights between 9 m and 18 m. Based on the results of experiments conducted in 15 m and 22 m high hangars, detector activation thresholds and detector spacing are analyzed for both smoke and heat detectors. Only ceiling mounted detection devices are analyzed in this paper. In addition to the detector threshold study, the predictive capabilities of computer fire model simulations were compared with experimental results. This comparison, which is based on 12 fire tests, resulted in the development of a new ceiling jet algorithm to model phenomena which had not been included in previous algorithms. The improved algorithm provides a better representation of the development of the ceiling jet temperature to a growing hot layer and a better estimation of plume centerline temperature. Guidelines are examined, based on the experimental results, for fire detector spacing, placement, and sensitivity. Recommendations concerning the use of computer fire models at these heights are made as a function of fire size and hot layer development. The role of draft curtains is discussed and their impact on detector activation is demonstrated.

Davis, W. D.↗
DOE OSTI2020

Custom NEON AOP reflectance mosaics and maps of shade masks, canopy water content

This mosaic of visible to shortwave infrared (VSWIR) data was derived from the assignable asset NEON AOP radiance data that was collected by LBNL’s Watershed Function SFA during the summer of 2018 (DOI: 10.15485/1617204). This atmospheric correction was completed to take into account site-specific terrain variability in the 334 km2 survey area centered around Crested Butte, CO. The atmospheric correction was completed using ACORN atmospheric correction software executed on 200 x 200 pixel kernels rather than line by line in order to capture local flight altitude conditions. Manual cloud delineation removed any small shaded areas that occurred within the data collection areas. Mosaics were developed based on preference for days that were in close timing proximity to the coincident ground campaign and with mosaicing criteria that minimized the angle between the sun and the sensor to retrieve the most consistent reflectance (min_phase_refl_tiled). Finally, we generated shade masks based on the geometry between the sun angle at time of flight, the ground surface, and the sensor. Here we provide the orthomosaiced estimated reflectance data (min_phase_refl_tiled.tif), canopy water content (wtrl), estimated atmospheric water vapor (wtrv), the observational data (obs) for this particular mosaic, the estimated visibility (vis), shade masks derived from the digital surface elevation model (shade) and the digital terrain model (shade_tch) added to the canopy height model (DOI: 10.15485/1617203), and a wavelength metadata file. Each image file is provided as a GeoTiff with internal tiling and LZW compression. These data can also be found on Google Earth Engine for extraction, download, and analysis of smaller extents (Google Earth Engine data is linked in external link table).

2018 NEON and 2025 CHESS Campaigns↗
DOE OSTI2022

Data from: Emerging wild virus of native grass bioenergy feedstock is well established in the Midwestern USA and associated with premature stand senescence

This dataset includes values for the prevalence of switchgrass mosaic virus (Genus Marafivirus, Family Tymoviridae) detected with molecular diagnostics (RT-PCR) in individual Panicum virgatum (switchgrass) plants and in Graminella leafhoppers that feed on them. Surveys were conducted in 15 sites in August 2012. Stands surveyed had been established for some time and represent a range of landscape contexts. Measures of stand height and percent senescence were also collected. Land cover composition surrounding each site was calculated from the USDA-NASS Cropland Data Layer and estimates of drought impact were derived from the US Drought Monitor.

09 BIOMASS FUELS↗
NASA NTRS1973

Mechanisms for Mars dust storms.

Characteristics of the Mars global dust storm are reviewed. At the Mariner 9 encounter, the dust consisted of highly absorbing particles distributed rather uniformly up to great height (about 50 km). These observations together with temperature distributions inferred from the Mariner 9 IRIS by Hanel et al. (1972) are used to estimate global wind systems during the dust storm. The global distribution and direction of light surface streaks indicate that the axisymmetric circulation was a dominant part of flow during the dust storm. The axisymmetric winds may become strong enough to raise dust over wide areas of Mars' tropics under unusual conditions: the incoming solar radiation must be near its seasonal maximum, the static stability must be low, and the atmosphere must be able to absorb and re-emit a sizeable fraction of the incoming radiation. Strong winds around the periphery of the retreating south polar cap would be driven by the temperature gradient at the cap edge and by the mass outflow due to subliming CO2. These polar winds could generate local dust storms, raising the general level of dustiness, and providing the conditions necessary for onset of a global dust storm.

Leovy, C. B.↗
NASA NTRS1974

Observations of coronal disturbances from 1 to 9 solar radii. I - First event of 1973 January 11

H alpha, white-light and radio observations of a coronal disturbance on Jan. 11, 1973, commencing at about 0036 hr UT show that a piston-driven shock wave propagated outward through the corona to heights of at least 9 solar radii. Probably most of the expelled coronal gas originated in a coronal enhancement in the lower corona. An estimate of the kinetic energy and the mass of the expelled gas is obtained which is compatible with observations of piston-driven shock waves near the earth. Shock-wave parameters are evaluated, and a model of the disturbance is outlined.

Stewart, R. T.↗
NASA NTRS1978

GEOS-3 ocean geoid investigation

A determination of the fine scale sea surface topography in the GEOS-3 calibration area using the radar altimeter data is presented. Estimates of the north-south and east-west components of the deflections of the vertical as well as values of the geoidal heights were made. Three major stages of processing were used in obtaining the final results. The first two use pass processors; in the final stage, the processor combines all the pass results to compute the final results. The results obtained compare favorably with gravimetrically determined geoids for this calibration area.

Yionoulis, S. M.↗
NASA NTRS1979

GEOS 3 ocean geoid investigation

A determination of the fine-scale sea surface topography in the GEOS 3 calibration area using the radar altimeter data is presented. Estimates of the north-south and east-west components of the deflections of the vertical as well as values of the geoidal heights are made. Three major stages of processing are used in obtaining the final results. The first two use pass processors; in the final stage the processor combines all the pass results to compute the final results. Comparison with a gravimetrically determined geoid for the calibration area, provided by the National Aeronautics and Space Administration, yielded a mean and standard deviation of 0.45 and 1.5 m, respectively

Yionoulis, S. M.↗
NASA NTRS1979

Smythii basin topography and comparisons with Orientale

The Smythii basin has the most extensive topographic coverage of any lunar multi-ringed basin. Topographic data are used to study the morphology and morphometry of Smythii and to make comparisons with similar basins. The depth of the basin is shown to be over 8 km, which is comparable to that of Orientale. The inner ring reaches heights of 3.4 km, while the intermediate ring exhibits little relief. Lowest points in the basin are related to mare ridges. Basin volume is estimated to be 21 million cubic kilometers. Evidence suggests that significant differences in substrate characteristics may have existed for the Smythii and Orientale impacts.

Strain, P. L.↗
NASA NTRS1982

Effects of miso- and mesoscale obstructions on PAM winds obtained during project NIMROD

Data from 27 PAM (Portable Automated Mesonet) stations, operational as a phase of project NIMROD (Northern Illinois Meteorological Research on Downburst), are presented. It was found that PAM-measured winds are influenced by the mesoscale obstruction of the Chicago metropolitan area, as well as by the misoscale obstruction of identified trees and buildings. The mesoscale obstruction was estimated within the range of near zero to 50%, increasing toward the city limits, while the misoscale obstruction was estimated as being as large as 58% near obstructing trees which were empirically calculated to cause a wind speed deficit 50-80 times their height. Despite a statistical analysis based on one-million PAM winds, wind speed and stability transmission factors could not be accurately calculated; thus, in order to calculate the airflow free from obstacle, PAM-measured winds must be corrected.

Fujita, T. T.↗
NASA NTRS1985

Mesospheric Winds and Tides at Arecibo/puerto Rico (18 Deg N, 67 Deg W) November 20-23, 1981

The SOUSY-VHF-Radar was operated in the period November 20 to 23, 1981 during a continuous run at the Arecibo Observatory. The data used for this analysis were recorded from 06 AST on November 20 until 06 AST on November 23. Meridional winds were measured at odd hours and zonal winds at even hours. The occurrence of mesospheric VHF radar echoes was limited as usual to the daylight hours between 06 and 18 AST. The height limits, were variable from day to day, they were roughly 62 to 90 km. The intermittency of echoes in time and height, as well as radio interference, made it fairly difficult to deduce tidal information for this time period. About 10 to 45 single velocity estimates could be used to calculate an hourly mean. The variance of the displayed resulting in data, obtained by weighted averaging over the 3 day period, is about similar to the mean. The winds were extremely low during the observation period. Velocities of the prevailing wind, observed during an earlier campaign were 5 to 10 times larger than in the period of November 20 to 23, 1981. The amplitudes of the diurnal tide are comparable.

Rottger, J.↗
NASA NTRS1985

Jovian ionospheric conductivity and magnetospheric plasma outflow - Voyager 1

Using magnetic field and plasma data from the Voyager 1 inbound encounter, local values are derived for the mass outflow rate and the radial bulk velocity in the dayside Jovian magnetosphere, and for the height-integrated Pedersen conductivity of the Jovian ionosphere. These values, accurate within a factor of 2, are compatible with previous order-of-magnitude estimates of these quantities. The results suggest that the shape of the plasma sheet is more complicated than previously suspected. A search for evidence of enhanced plasma outflow in the active sector was inconclusive.

Hairston, M. R.↗
NASA NTRS1990

Theoretical characterization of the 5Pi and 3Pi potential energy surfaces for NH + O yields N + OH

The reactant, product, and saddle point regions of the 5Pi and 3Pi potential energy surfaces for the reaction NH + O yields N + OH have been characterized using complete active space self consistent field/externally contracted configuration interaction calculations with large atomic natural orbital basis sets. The computed barrier heights are 5.6 and 11.7 kcal/mol on the 5Pi and 3Pi surfaces, respectively. Transition state theory with an Eckart tunneling correction is used to estimate the rate constant on the 5Pi surface.

Walch, Stephen P.↗
NASA NTRS1993

Accurate ab initio quartic force fields for the ions HCO(+) and HOC(+)

The quartic force fields of HCO(+) and HOC(+) have been computed using augmented coupled cluster methods and basis sets of spdf and spdfg quality. Calculations on HCN, CO, and N2 have been performed to assist in calibrating the computed results. Going from an spdf to an spdfg basis shortens triple bonds by about 0.004 A, and increases the corresponding harmonic frequency by 10-20/cm, leaving bond distances about 0.003 A too long and triple bond stretching frequencies about 5/cm too low. Accurate estimates for the bond distances, fundamental frequencies, and thermochemical quantities are given. HOC(+) lies 37.8 +/- 0.5 kcal/mol (0 K) above HCO(+); the classical barrier height for proton exchange is 76.7 +/- 1.0 kcal/mol.

Martin, J. M. L.↗
NASA NTRS2021

Locating the Isolator Shock-Train Leading Edge with Limited Pressure Information

Real-time detection and control of the isolator shock-train leading edge (STLE) is important to the performance of high-speed air-breathing engines, such as dual-mode scramjets. Typically, the STLE location is determined using wall static-pressure measurements, but there are often restrictions on the placement and overall number of the pressure transducers, reducing the viability and accuracy of such approaches. To address these issues, we introduce the adaptive pressure profile (APP) method for estimating the STLE location. This method does not require extensive prior characterization of the isolator or engine model. Instead, it uses real-time pressure measurements from a small number of transducers to adaptively learn the isolator pressure profile and subsequently uses this deduced profile to estimate the STLE location in a data-driven manner. The APP method works well in situations with sparse transducer placement. It produces accurate estimates when the STLE location is 1) not bounded by two or more transducers or 2) between two transducers that are several isolator duct heights apart. We demonstrate the efficacy of the APP method using simulations and experimental data from direct-connect isolator models. This validation shows that the APP method is accurate and robust for different flow regimes, transducer configurations, and model geometries.

Gregory J. Hunt↗
DOE OSTI2023

Reducing Uncertainty in Offshore Wind Energy Yield Estimates via a Metocean Reference Site

The offshore wind industry is burgeoning in the coastal waters of the United States, specifically along the Atlantic. For wind energy to be successful, reliable observations and model simulations are needed for resource assessment and forecasting. While many of these activities have already begun, there is currently an absence of observations at hub-height in these waters, with the closest available hub-height measurements usually taken onshore. Deployment of floating lidars has occurred through various federally funded projects, but only encapsulates time periods of a couple of years at best. Private industry is also beginning to leverage floating lidars, but this data is often proprietary, and not shared with the general public. In this work, we make the case for a metocean reference site for long-term offshore wind energy. Specifically, we quantify the impact of having a metocean reference site compared to other methods of determining hub-height winds and energy production. We use an offshore floating lidar to directly measure the wind resource, and compare these measurements to predictions derived from other widely-available surface meteorological variables. These prediction methods (vertical extrapolation, machine learning, and NWP output) produce a variety of vertical wind speed profiles, of which produce different energy yield estimates for a reference offshore turbine (Figure 1). While some methods perform reasonably well against the lidar, the uncertainty in these energy yield estimates has financial implications, further illustrating the need for long-term measurements in coastal waters.

machine learning↗
NASA NTRS2007

The Width of a Solar Coronal Mass Ejection and the Source of the Driving Magnetic Explosion: A Test of the Standard Scenario for CME Production

We show that the strength (B(sub F1are)) of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width (Final Theta(sub CME)) of the CME in the outer corona and the final angular width (Theta(sub Flare)) of the flare arcade: B(sub Flare) approx. equals 1.4[(Final Theta(sub CME)/Theta(sub Flare)] (exp 2)G. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid; (2) in the outer corona (R > 2 (solar radius)) the CME is roughly a "spherical plasmoid with legs" shaped like a lightbulb; and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. One of these CMEs was an over-and-out CME, that is, in the outer corona the CME was laterally far offset from the flare-marked source of the driving magnetic explosion. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement (1) indicates that CMEs are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field; (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs; and (3) shows that a CME's final angular width in the outer corona can be estimated from the amount of magnetic flux covered by the source-region flare arcade.

Moore, Ronald L.↗
NASA NTRS2004

First Look at the Upper Tropospheric Ozone Mixing Ratio from OMI Estimated using the Cloud Slicing Technique

The Cloud Slicing technique has emerged as a powerful tool for the study of ozone in the upper troposphere. In this technique one looks at the variation with cloud height of the above-cloud column ozone derived from the backscattered ultraviolet instruments, such as TOMS, to determine the ozone mixing ratio. For this technique to work properly one needs an instrument with relatively good horizontal resolution with very good signal to noise in measuring above-cloud column ozone. In addition, one needs the (radiatively) effective cloud pressure rather than the cloud-top pressure, for the ultraviolet photons received by a satellite instrument are scattered from inside the cloud rather than from the top. For this study we use data from the OMI sensor, which was recently launched on the EOS Aura satellite. OMI is a W-Visible backscattering instrument with a nadir pixel size of 13 x 24 km. The effective cloud pressure is derived from a new algorithm based on Rotational Raman Scattering and O2-O2, absorption in the 340-400 nm band of OMI.

Bhartia, Pawan K.↗
DOE OSTI2020

An extended radar relative calibration adjustment (eRCA) technique for higher-frequency radars and range–height indicator (RHI) scans

Abstract. This study extends the relative calibration adjustment technique for calibration of weather radars to higher-frequency radars as well as range–height indicator (RHI) scans. The calibration of weather radars represents one of the most dominant sources of error for their use in a variety of fields including quantitative precipitation estimation and model comparisons. While most weather radars are routinely calibrated, the frequency of calibration is often less than required, resulting in miscalibrated time periods. While full absolute calibration techniques often require the radar to be taken offline for a period of time, there have been online calibration techniques discussed in the literature. The relative calibration adjustment (RCA) technique uses the statistics of the ground clutter surrounding the radar as a monitoring source for the stability of calibration but has only been demonstrated to work at S- and C-band for plan-position indicator (PPI) scans at a constant elevation. In this work the RCA technique is modified to work with higher-frequency radars, including Ka-band cloud radars. At higher frequencies the properties of clutter can be much more variable. This work introduces an extended clutter selection procedure that incorporates the temporal stability of clutter and helps to improve the operational stability of RCA for relatively higher-frequency radars. The technique is also extended to utilize range–height scans from radars where the elevation is varied rather than the azimuth. These types of scans are often utilized with research radars to examine the vertical structure of clouds. The newly extended technique (eRCA) is applied to four Department of Energy Atmospheric Radiation Measurement (DOE ARM) weather radars ranging in frequency from C- to Ka-band. Cross comparisons of three co-located radars with frequencies C, X, and Ka at the ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) site show that the technique can determine changes in calibration. Using an X-band radar at the ARM Eastern North Atlantic (ENA) site, we show how the technique can be modified to be more resilient to clutter fields that show increased variability, in this case due to sea clutter. The results show that this technique is promising for a posteriori data calibration and monitoring.

47 OTHER INSTRUMENTATION↗