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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 433 records · Page 24
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NASA NTRS2014

Prompt Emission of GRB 121217A from Gamma-Rays to the Near-Infrared

The mechanism that causes the prompt-emission episode of gamma-ray bursts (GRBs) is still widely debated despite there being thousands of prompt detections. The favoured internal shock model relates this emission to synchrotron radiation. However, it does not always explain the spectral indices of the shape of the spectrum, which is often fit with empirical functions, such as the Band function. Multi-wavelength observations are therefore required to help investigate the possible underlying mechanisms that causes the prompt emission. We present GRB 121217A, for which we were able to observe its near-infrared (NIR) emission during a secondary prompt-emission episode with the Gamma-Ray burst Optical Near-infrared Detector (GROND) in combination with the Swift and Fermi satellites, which cover an energy range of 5 orders of magnitude (10(exp −3) keV to 100 keV). We determine a photometric redshift of z = 3.1 +/- 0.1 with a line-of-sight with little or no extinction (AV approx. 0 mag) utilising the optical/NIR SED. From the afterglow, we determine a bulk Lorentz factor of Gamma(sub 0) approx. 250 and an emission radius of R < 1018 cm. The prompt-emission broadband spectral energy distribution is well fit with a broken power law with beta1 = −0.3 +/- 0.1 and beta2 = 0.6 +/- 0.1 that has a break at E = 6.6 +/- 0.9 keV, which can be interpreted as the maximum injection frequency. Self-absorption by the electron population below energies of Ea < 6 keV suggest a magnetic field strength of B approx. 10(exp 5) G. However, all the best fit models underpredict the flux observed in the NIR wavelengths, which also only rebrightens by a factor of approx. 2 during the second prompt emission episode, in stark contrast to the X-ray emission, which rebrightens by a factor of approx. 100. This suggests an afterglow component is dominating the emission. We present GRB 121217A, one of the few GRBs that has multi-wavelength observations of the prompt-emission period and shows that it can be understood with a synchrotron radiation model. However, due to the complexity of the GRB's emission, other mechanisms that result in Band-like spectra cannot be ruled out.

prompt↗
NASA NTRS1991

Anisotropic inverse Compton emission

The angular distribution of the power and spectrum of Compton-scattered radiation in the case of an anisotropic distribution of soft photons is considered. Results obtained show that both the intensity and spectrum of the scattered radiation are a function of the Lorentz factor of the electrons, the geometry of the soft X-ray source and the viewing angle. The intensity of the hard X-rays scattered back into the bowl can be significantly greater (by a factor of up to 5.5) than that scattered toward the observer for an isotropic distribution of relativistic electrons at the center of a hemispherical bowl of soft X-ray emission. This factor is increased as the solid angle of the soft X-ray source subtended at the location of the electrons is reduced. The results obtained here have inmplications for models invoking a further 'reflection' of the resultant hard X-rays from the surface of a disk.

Ghisellini, G.↗
NASA NTRS2001

Hydrogen/Air Fuel Nozzle Emissions Experiments

The use of hydrogen combustion for aircraft gas turbine engines provides significant opportunities to reduce harmful exhaust emissions. Hydrogen has many advantages (no CO2 production, high reaction rates, high heating value, and future availability), along with some disadvantages (high current cost of production and storage, high volume per BTU, and an unknown safety profile when in wide use). One of the primary reasons for switching to hydrogen is the elimination of CO2 emissions. Also, with hydrogen, design challenges such as fuel coking in the fuel nozzle and particulate emissions are no longer an issue. However, because it takes place at high temperatures, hydrogen-air combustion can still produce significant levels of NOx emissions. Much of the current research into conventional hydrocarbon-fueled aircraft gas turbine combustors is focused on NOx reduction methods. The Zero CO2 Emission Technology (ZCET) hydrogen combustion project will focus on meeting the Office of Aerospace Technology goal 2 within pillar one for Global Civil Aviation reducing the emissions of future aircraft by a factor of 3 within 10 years and by a factor of 5 within 25 years. Recent advances in hydrocarbon-based gas turbine combustion components have expanded the horizons for fuel nozzle development. Both new fluid designs and manufacturing technologies have led to the development of fuel nozzles that significantly reduce aircraft emissions. The goal of the ZCET program is to mesh the current technology of Lean Direct Injection and rocket injectors to provide quick mixing, low emissions, and high-performance fuel nozzle designs. An experimental program is planned to investigate the fuel nozzle concepts in a flametube test rig. Currently, a hydrogen system is being installed in cell 23 at NASA Glenn Research Center's Research Combustion Laboratory. Testing will be conducted on a variety of fuel nozzle concepts up to combustion pressures of 350 psia and inlet air temperatures of 1200 F. Computational fluid dynamics calculations, with the Glenn developed National Combustor Code, are being performed to optimize the fuel nozzle designs.

Smith, Timothy D.↗
NASA NTRS2012

Spatially-Resolved HST GRISM Spectroscopy of a Lensed Emission Line Galaxy at Z to approximately 1

We take advantage of gravitational lensing amplification by Abell 1689 (z=0.187) to undertake the first space-based census of emission line galaxies (ELGs) in the field of a massive lensing cluster. Forty-three ELGs are identified to a flux of i(sub 775)=27.3 via slitless grism spectroscopy. One ELG (at z=0.7895) is very bright owing to lensing magnification by a factor of approx = 4.5. Several Balmer emission lines detected from ground-based follow-up spectroscopy signal the onset of a major starburst for this low-mass galaxy (M(sub star) approx = 2 x 10(exp 9)Solar Mass) with a high specific star formation rate (approx = 20/ Gyr). From the blue emission lines we measure a gas-phase oxygen abundance consistent with solar (12+log(O /H)=8.8 +/- O.2). We break the continuous line-emitting region of this giant arc into seven approx 1 kpc bins (intrinsic size) and measure a variety of metallicity dependent line ratios. A weak trend of increasing metal fraction is seen toward the dynamical center of the galaxy. Interestingly, the metal line ratios in a region offset from the center by -lkpc have a placement on the blue HI! region excitation diagram with f([OIII]/ f(H-Beta) and f([NeIII/ f(H-Beta) that can be fit by an AGN. This asymmetrical AGN-like behavior is interpreted as a product of shocks in the direction of the galaxy's extended tail, possibly instigated by a recent galaxy interaction.

Frye, Brenda L.↗
NASA NTRS2019

Quantification of CO2 and CH4 emissions over Sacramento, California, based on divergence theorem using aircraft measurements

Emission estimates of carbon dioxide (CO2) and methane (CH4) and the meteorological factors affecting them are investigated over Sacramento, California, using an aircraft equipped with a cavity ring-down greenhouse gas sensor as part of the Alpha Jet Atmospheric eXperiment (AJAX) project. To better constrain the emission fluxes, we designed flights in a cylindrical pattern and computed the emission fluxes from two flights using a kriging method and Gauss’s divergence theorem. Differences in wind treatment and assumptions about background concentrations affect the emission estimates by a factor of 1.5 to 7. The uncertainty is also impacted by meteorological conditions and distance from the emission sources. The vertical layer averaging affects the flux estimate, but the choice of raw wind or mass-balanced wind is more important than the thickness of the vertical averaging for massbalanced wind for both urban and local scales. The importance of vertical mass transfer for flux estimates is examined, and the difference in the total emission estimate with and without vertical mass transfer is found to be small, especially at the local scale. The total flux estimates accounting for the entire circumference are larger than those based solely on measurements made in the downwind region. This indicates that a closed-shape flight profile can better contain total emissions relative to a one-sided curtain flight because most cities have more than one point source and wind direction can change with time and altitude. To reduce the uncertainty of the emission estimate, it is important that the sampling strategy account not only for known source locations but also possible unidentified sources around the city. Our results highlight that aircraft-based measurements using a closed-shape flight pattern are an efficient and useful strategy for identifying emission sources and estimating local- and city-scale greenhouse gas emission fluxes.

Ju-Mee Ryoo↗
DOE OSTI2021

Evaluating Emissions Reductions from DERs in REopt Lite

Creating a clear business justification for an energy & water project is essential for developing projects by transforming data and analysis into a compelling story to secure management buy-in. This presentation provides an overview of how distributed energy resources (DERs) can provide cost savings, resilience benefits, and emissions reduction. Many technical and economic factors affect which distributed energy technologies can best meet site goals, and should be considered concurrently. With increasingly integrated and complex systems, back-of-the envelope calculations are no longer sufficient to determine distributed energy project potential. REopt Lite can be used to model emissions and evaluate the impact of DERs on reducing emissions.

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

Analysis of EUV limb brightening observations from ATM. II - Influence of spicules

A comparison of limb brightening measurements with theoretical limb brightening curves calculated for simple atmospheric models indicates that a significant fraction of the EUV emission from lines formed in the transition layer comes from spicules. We find that spicules contribute about 20% of the total quiet sun intensity for lines of the C II, C III, N III, and O VI ions. The uncertainty in the magnitude of the percentage is about a factor of 2. The EUV-emission scale heights above the limb are consistent with the assumption that the variation with height of the number of EUV-emitting spicules is the same as for H-alpha-emitting spicules. Optical depths derived for the C II 1335 A and C III 977 A lines yield estimates for the pressure in the transition layer that are in good agreement with pressures derived under the assumption that the transition layer is in pressure equilibrium with the chromosphere and corona.

Withbroe, G. L.↗
DOE OSTI2025

Applying Gaussian Process Machine Learning and Modern Probabilistic Programming to Satellite Data to Infer CO 2 Emissions

Satellite data provides essential insights into the spatiotemporal distribution of CO 2 concentrations. However, many atmospheric inverse models fail to adequately incorporate the spatial and temporal correlations inherent in satellite observations and often lack rigorous methods for estimating parameters like spatial length scales. We introduce an inference model that processes the spatiotemporal covariance in satellite data and estimates hyperparameters such as covariance length scales. Our approach uses the Gaussian process (GP) machine learning (ML) and modern probabilistic programming languages (PPLs) to perform atmospheric inversions of emissions from satellite data. We develop a GP ML inversion system based on modern PPLs and the GEOS-Chem chemical transport model, simulating atmospheric CO 2 concentrations corresponding to the Orbiting Carbon Observatory-2/3 (OCO-2/3) data for July 2020. In our supervised learning framework, we treat the GEOS-Chem simulated data set as the target, with predictors derived by scaling the target with sector-specific factors hidden from the GP machine. Our results show that the GP model, combined with GPU-enabled PPLs, effectively retrieves true emission scaling factors and infers noise levels concealed within the data. This suggests that our method could be applied over larger areas with more complex covariance structures, enabling comprehensive analysis of the spatiotemporal patterns observed in OCO-2/3 and similar satellite data sets.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1987

Theoretical investigations of X-ray bursts

Current theoretical understanding of the X-ray burst phenomenon is reviewed, providing a framework in which the burst radiation can be used as a diagnostic of the fundamental properties of the underlying neutron star. The typical Type I X-ray burst is detected as a rapid increase in emission to a level about a factor of 10 above that seen during the quiescent state and recurs on time scales which range from several hours to several days. The thermonuclear flash model has successfully reproduced the basic features of the X-ray burst phenomenon and thereby provided strong theoretical evidence that neutron stars are involved. Topics covered include: theory of the emission spectrum; oscillation modes and prospects for diagnosing the thermal state of neutron stars through experiments on board the X-Ray Timing Explorer or the Advanced X-Ray Astrophysics Facility; applications to the mass and radius of a neutron star.

Taam, Ronald E.↗
DOE OSTI2020

Theory of molecular emission power spectra. I. Macroscopic quantum electrodynamics formalism

In this work, we study the emission power spectrum of a molecular emitter with multiple vibrational modes in the framework of macroscopic quantum electrodynamics. The theory we present is general for a molecular spontaneous emission spectrum in the presence of arbitrary inhomogeneous, dispersive, and absorbing media. Moreover, the theory shows that the molecular emission power spectra can be decomposed into the electromagnetic environment factor and lineshape function. In order to demonstrate the validity of the theory, we investigate the lineshape function in two limits. In the incoherent limit (single molecules in a vacuum), the lineshape function exactly corresponds to the Franck–Condon principle. In the coherent limit (single molecules strongly coupled with single polaritons or photons) together with the condition of high vibrational frequency, the lineshape function exhibits a Rabi splitting, the spacing of which is exactly the same as the magnitude of exciton–photon coupling estimated by our previous theory [S. Wang et al., J. Chem. Phys. 151, 014105 (2019)]. Finally, we explore the influence of exciton–photon and electron–phonon interactions on the lineshape function of a single molecule in a cavity. The theory shows that the vibronic structure of the lineshape function does not always disappear as the exciton–photon coupling increases, and it is related to the loss of a dielectric environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Compilation of a Global Emission Inventory from 1980 to 2000 for Global Model Simulations of the Long-term Trend of Tropospheric Aerosols

The approach to create a comprehensive emission inventory for the time period 1980 to 2000 is described in this paper. We have recently compiled an emission database, which we will use for a 21 year simulation of tropospheric aerosols with the GOCART model. Particular attention was paid to the time-dependent SO2, black carbon and organic carbon aerosol emissions. For the emission of SO2 from sporadically erupting volcanoes, we assembled emission data from the Global Volcanism Program of the Smithsonian Institution, using the VEI to derive the volcanic cloud height and the SO2 amount, and amended this dataset by the SO2 emission data from the TOMS instrument when available. 3-dimensional aircraft emission data was obtained for a number of years from the AEAP project, converted from burned fuel to SO2 and interpolated to each year, taking the sparsity of the flight patterns into account. Other anthropogenic SO2 emissions are based on gridded emissions from the EDGAR 2000 database (excluding sources from aircraft, biomass burning and international ship traffic), which were scaled to individual years with country/regional based emission inventories. Gridded SO2 emissions from international ship traffic for 2000 and the scaling factors for other years are from [Eyring et al., 2005]. We used gridded anthropogenic black and organic carbon emissions for 1996 [Bond et al., 2005], again excluding aircraft, biomass burning and ship sources. These emissions were scaled with regional based emission inventories from 1980 to 2000 to derive gridded emissions for each year. The biomass burning emissions are based on a climatology, which is scaled with regional scaling factors derived from the TOMS aerosol index and the AVHRR/ASTR fire counts to each year [Duncan et al., 2003]. Details on the integration of the information from the various sources will be provided and the distribution patterns and total emissions in the final product will be discussed.

Diehl, Thomas L.↗
NASA NTRS2007

Compilation of a Global Emission Inventory from 1980 to 2000 for Global Model Simulations of the Long-term Trend of Tropospheric Aerosols

The approach to create a comprehensive emission inventory for the time period 1980 to 2000 is described in this paper. We have recently compiled an emission database, which we will use for a 21 year simulation of tropospheric aerosols with the GOCART model. Particular attention was paid to the time-dependent SO2, black carbon and organic carbon aerosol emissions. For the emission of SO2 from sporadically erupting volcanoes, we assembled emission data from the Global Volcanism Program of the Smithsonian Institution, using the VEI to derive the volcanic cloud height and the SO2 amount, and amended this dataset by the SO2 emission data from the TOMS instrument when available. 3-dimensional aircraft emission data was obtained for a number of years from the AEAP project, converted from burned fuel to SO2 and interpolated to each year, taking the sparsity of the flight patterns into account. Other anthopogenic SO2 emissions are based on gridded emissions from the EDGAR 2000 database (excluding sources from aircraft, biomass burning and international ship traffic), which were scaled to individual years with country/regional based emission inventories. Gridded SO2 emissions from international ship traffic for 2000 and the scaling factors for other years are from [Eyring et al., 2005]. We used gridded anthropogenic black and organic carbon emissions for 1996 [Bond et al., 2005], again excluding aircraft, biomass burning and ship sources. These emissions were scaled with regional based emission inventories from 1980 to 2000 to derive gridded emissions for each year. The biomass burning emissions are based on a climatology, which is scaled with regional scaling factors derived from the TOMS aerosol index and the AVHRR/ATSR fire counts to each year [Duncan et al., 2003]. Details on the integration of the information from the various sources will be provided and the distribution patterns and total emissions in the final product will be discussed.

Diehl, T. L.↗
NASA NTRS2000

Separation of Atmospheric and Surface Spectral Features in Mars Global Surveyor Thermal Emission Spectrometer (TES) Spectra

We present two algorithms for the separation of spectral features caused by atmospheric and surface components in Thermal Emission Spectrometer (TES) data. One algorithm uses radiative transfer and successive least squares fitting to find spectral shapes first for atmospheric dust, then for water-ice aerosols, and then, finally, for surface emissivity. A second independent algorithm uses a combination of factor analysis, target transformation, and deconvolution to simultaneously find dust, water ice, and surface emissivity spectral shapes. Both algorithms have been applied to TES spectra, and both find very similar atmospheric and surface spectral shapes. For TES spectra taken during aerobraking and science phasing periods in nadir-geometry these two algorithms give meaningful and usable surface emissivity spectra that can be used for mineralogical identification.

Smith, Michael D.↗
NASA NTRS1987

Is optical Fe II emission related to the soft X-ray properties of quasars?

Radio-quiet quasars generally show broad, blended multiplets of Fe II emission in their optical and UV spectra. Radio-loud quasars also show UV Fe II emission, but their optical Fe II emission is generally weaker. No satisfactory theory connecting the generation of Fe II and radio emission has been found to explain this effect. A second, well-established distinction between the two clases of quasar is in their X-ray properties: radio-loud quasars are more X-ray luminous, and recent results have shown that they also have systematically flatter soft X-ray slopes. Here it is proposed that the second effect causes the first; i.e., that the primary factor controlling the optical Fe II emission is the soft X-ray spectrum. This proposition is supported by X-ray and optical data for nine quasars, which shows a correlation between the soft X-ray slope and the strength of the optical Fe II emission. One of these quasars (1803+676) is radio-quiet, and yet its optical spectrum shows no evidence for Fe II emission. This quasar is also unusual in that it has a flat X-ray spectrum. This further supports the proposal that the X-ray spectrum is important in determining the relative strengths of UV and optical Fe II emission.

Wilkes, Belinda J.↗
NASA NTRS2008

RFID Transponders' RF Emissions in Aircraft Communication and Navigation Radio Bands

Radiated emission data in aircraft communication and navigation bands are presented for several active radio frequency identification (RFID) tags. The individual tags are different in design, operation and transmitting frequencies. The process for measuring the tags emissions in a reverberation chamber is discussed. Measurement issues dealing with tag interrogation, low level measurement in the presence of strong transmissions, and tags low duty factors are discussed. The results show strong emissions, far exceeding aircraft emission limits and can be of potential interference risks.

Nguyen, Truong X.↗
DOE OSTI2024

Adoption of Plug-in Electric Vehicles: Local Fuel Use and Greenhouse Gas Emissions Reductions Across the U.S.

The dependence on gasoline-powered light-duty automobiles has made U.S. households vulnerable to the burden of fuel costs. Tailpipe emissions from these vehicles constitute 58% of greenhouse gas (GHG) emissions in the U.S., which are damaging to the environment (EPA, 2023). The adoption of plug-in electric vehicles (PEVs) has been shown to effectively reduce fuel costs and GHG emissions. However, local effects on these benefits are not well understood by American consumers, potentially limiting adoption and therefore the realization of PEV benefits at scale (MacInnis & Krosnick, 2020; EY Americas, 2023). To fill this research gap, this study estimates the fuel cost savings and GHG emission reductions at the state and ZIP code levels by considering local fuel prices, vehicle class preference, average vehicle model year, fuel efficiencies, and driving intensities. The study's findings reveal that the adoption of PEVs can yield substantial benefits in terms of fuel cost savings and GHG emission reductions nationwide. Specifically, driving a battery electric vehicle (BEV) is estimated to result in annual savings of up to $\$2,200$, while driving a plug-in hybrid electric vehicle (PHEV) can lead to savings up to $\$1,500$, when compared to an internal combustion engine vehicle (ICEV) of equivalent size. Moreover, using population-weighted averages by ZIP code, BEVs and PHEVs show the potential to save 400 and 200 grams of carbon dioxide equivalent per mile, respectively, compared to a representative ICEV of the same class. The magnitude of fuel cost savings and emissions reduction vary by region due to various factors. Generally, regions with high gasoline prices, low electricity prices, preferences for larger vehicles, and high driving intensities tend to see relatively large fuel savings. The emissions reductions are more pronounced in areas with clean grids where consumer preferences lie with large vehicles. This regional variability underscores the importance of considering local contextual factors when assessing the potential benefits of PEV adoption. In more than 99% of U.S. ZIP codes, PEVs result in overall savings in fuel use (and subsequent costs) and GHG emissions. While not a central focus of this analysis, reductions in GHG tailpipe emissions from PEV adoption would also come with reductions in criteria pollutant emissions, contributing to improved local air quality depending on the PEV penetration, population density, and electricity generation infrastructure in the locality.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS2004

Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of their Matter Content

We propose a method for estimating the composition, i.e. the relative amounts of leptons and protons, of extragalactic jets which exhibit Chandra - detected knots in their kpc scale jets. The method relies on measuring, or setting upper limits on, the component of the Cosmic Microwave Background (CMB) radiation that is bulk-Comptonized by the cold electrons in the relativistically flowing jet. These measurements, along with modeling of the broadband knot emission that constrain the bulk Lorentz factor GAMMA of the jets, can yield estimates of the jet power carried by protons and leptons. We provide an explicit calculation of the spectrum of the bulk-Comptonized (BC) CMB component and apply these results to PKS 0637 - 752 and 3C 273, two superluminal quasars with Chandra - detected large scale jets. What makes these sources particularly suited for such a procedure is the absence of significant non-thermal jet emission in the 'bridge', the region between the core and the first bright jet knot, which guarantees that most of the electrons are cold there, leaving the BC scattered CMB radiation as the only significant source of photons in this region. At lambda = 3.6 - 8.0 microns, the most likely band to observe the BC scattered CMB emission, the Spitzer angular resolution (approximately 1" - 3") is considerably smaller than the the 'bridges' of these jets (approximately 10"), making it possible to both measure and resolve this emission.

Georganopoulos, Markos↗