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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Measurement of energy muons in EAS at energy region larger thean 10(17) eV

A measurement of low energy muons in extensive air showers (EAS) (threshold energies are 0.25, 0.5, 0.75 and 1.38 GeV) was carried out. The density under the concrete shielding equivalent to 0.25 GeV at core distance less than 500 m and 0.5 GeV less than 150 m suffers contamination of electromagnetic components. Therefore the thickness of concrete shielding for muon detectors for the giant air shower array is determined to be 0.5 GeV equivalence. Effects of photoproduced muons are found to be negligible in the examined ranges of shower sizes and core distances. The fluctuation of the muon density in 90 sq m is at most 25% between 200 m and 600 m from the core around 10 to the 17th power eV.

Matsubara, Y.↗
NASA NTRS1985

Energy spectra of high energy atmospheric neutrinos

Focusing on high energy neutrinos ( or = 1 TeV), a new calculation of atmospheric neutrino intensities was carried out taking into account EMC effects observed in P-A collisions by accelerator, recent measurement of primary cosmic ray spectrum and results of cosmic ray muon spectrum and charge ratio. Other features of the present calculation are (1) taking into account kinematics of three body decays of kaons and charm particles in diffusion equations and (2) taking into account energy dependence of kaon production.

Mitsui, K.↗
NASA NTRS1986

Variably spaced superlattice energy filter, a new device design concept for high-energy electron injection

A new variably spaced superlattice energy filter is proposed which provides high-energy injection of electrons into a bulk semiconductor layer based on resonant tunneling between adjacent quantum well levels which are brought into alignment by an applied bias. Applications of this concept to a variety of optoelectronic devices and to thin-film electroluminescent devices and photodetectors are discussed.

Summers, C. J.↗
NASA NTRS1986

The beta-SiC(100) surface studied by low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectra

The beta-SiC(100) surface has been studied by low energy electron diffraction, Auger electron spectroscopy, high resolution electron energy loss spectra (HREELS), and core level excitation EELS. Two new Si-terminated phases have been discovered, one with (3 x 2) symmetry, and the other with (2 x 1) symmetry. Models are presented to describe these phases. New results, for the C-rich surface, are presented and discussed. In addition, core level excitation EELS results are given and compared with theory.

Dayan, M.↗
NASA NTRS1986

Average transverse momentum and energy density in high-energy nucleus-nucleus collisions

Emulsion chambers were used to measure the transverse momenta of photons or pi(0) mesons produced in high-energy cosmic-ray nucleus-nucleus collisions. A group of events having large average transverse momenta has been found which apparently exceeds the expected limiting values. Analysis of the events at early interaction times, of the order of 1 fm/c, indicates that the observed transverse momentum increases with both rapidity density and energy density.

Burnett, T. H.↗
NASA NTRS1987

Localization, time histories, and energy spectra of a new type of recurrent high-energy transient source

The detection of a recurrent high-energy transient source which is neither a classical X-ray nor a gamma-ray burster, but whose properties are intermediate between the two, is reported. The energy spectra of 12 recurrent events are found to be soft, characterized by kT's of 34-56 keV. The time histories are short with rise and fall times as fast as about 10 ms. The source location is a 0.12 sq deg region about 10 deg from the Galactic center.

Atteia, J.-L.↗
NASA NTRS1987

Wave energy in white dwarf atmospheres. I - Magnetohydrodynamic energy spectra for homogeneous DB and layered DA stars

The radiative damping of acoustic and MHD waves that propagate through white dwarf photospheric layers is studied, and other damping processes that may be important for the propagation of the MHD waves are calculated. The amount of energy remaining after the damping processes have occurred in different types of waves is estimated. The results show that lower acoustic fluxes should be expected in layered DA and homogeneous DB white dwarfs than had previously been estimated. Acoustic emission manifests itself in an enhancement of the quadrupole term, but this term may become comparable to or even lower than the dipole term for cool white dwarfs. Energy carried by the acoustic waves is significantly dissipated in deep photospheric layers, mainly because of radiative damping. Acoustically heated corona cannot exist around DA and DB white dwarfs in a range T(eff) = 10,000-30,000 K and for log g = 7 and 8. However, relatively hot and massive white dwarfs could be exceptions.

Musielak, Zdzislaw E.↗
NASA NTRS1988

Auroral energy deposition rate, characteristic electron energy, and ionospheric parameters derived from Dynamics Explorer 1 images

Auroral images obtained by the Spin Scan Auroral Imager (SAI) aboard the DE-1 satellite were used to derive auroral energy deposition rate, characteristic electron energy, and ionospheric parameters. The principles involved in the imaging technique and the physical mechanisms that underlie the relationship between the spectral images and the geophysical parameters are discussed together with the methodology for implementing such analyses. It is shown that images obtained with the SAI provide global parameters at 12-min temporal resolution; the spatial resolution is limited by the field of view of a pixel. The analysis of the 12-min images presented yielded a representation of ionospheric parameters that was better than can be obtained using empirical models based on local measurements averaged over long periods of time.

Rees, M. H.↗
NASA NTRS1995

Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

Patterson, James D.↗
NASA NTRS2000

An Estimation of Turbulent Kinetic Energy and Energy Dissipation Rate Based on Atmospheric Boundary Layer Similarity Theory

Algorithms are developed to extract atmospheric boundary layer profiles for turbulence kinetic energy (TKE) and energy dissipation rate (EDR), with data from a meteorological tower as input. The profiles are based on similarity theory and scalings for the atmospheric boundary layer. The calculated profiles of EDR and TKE are required to match the observed values at 5 and 40 m. The algorithms are coded for operational use and yield plausible profiles over the diurnal variation of the atmospheric boundary layer.

Han, Jongil↗
NASA NTRS1997

Rotational Energy Transfer of N2 Determined Using a New Ab Initio Potential Energy Surface

A new N2-N2 rigid-rotor surface has been determined using extensive Ab Initio quantum chemistry calculations together with recent experimental data for the second virial coefficient. Rotational energy transfer is studied using the new potential energy surface (PES) employing the close coupling method below 200 cm(exp -1) and coupled state approximation above that. Comparing with a previous calculation based on the PES of van der Avoird et al.,3 it is found that the new PES generally gives larger cross sections for large (delta)J transitions, but for small (delta)J transitions the cross sections are either comparable or smaller. Correlation between the differences in the cross sections and the two PES will be attempted. The computed cross sections will also be compared with available experimental data.

Huo, Winifred M.↗
NASA NTRS2012

Method for Predicting the Energy Characteristics of Li-Ion Cells Designed for High Specific Energy

Novel electrode materials with increased specific capacity and voltage performance are critical to the NASA goals for developing Li-ion batteries with increased specific energy and energy density. Although performance metrics of the individual electrodes are critically important, a fundamental understanding of the interactions of electrodes in a full cell is essential to achieving the desired performance, and for establishing meaningful goals for electrode performance in the first place. This paper presents design considerations for matching positive and negative electrodes in a viable design. Methods for predicting cell-level performance, based on laboratory data for individual electrodes, are presented and discussed.

Bennett, William, R.↗
NASA NTRS2012

Using Sdo's AIA to Investigate Energy Transport from a Flare's Energy Release Site to the Chromosphere

Coordinated observations of a GOES B4.8 microflare with SDOs Atmospheric Imaging Assembly (AIA) and the RamatyHigh Energy Solar Spectroscopic Imager (RHESSI) on 2010 July 31 show that emission in all seven of AIAs EUV channels brightened simultaneously nearly 6 min before RHESSI or GOES detected emission from plasma at temperatures around 10 MK. Aims. To help interpret these and AIA flare observations in general, we characterized the expected temporal responses of AIAs 94, 131, 171, 193, 211, and 335 channels to solar flare brightenings by combining (1) AIAs nominal temperature response functions available through SSWIDL with (2) EUV spectral line data observed in a flare loop Coordinated observations of a GOES B4.8 microflare with SDOs Atmospheric Imaging Assembly (AIA) and the RamatyHigh Energy Solar Spectroscopic Imager (RHESSI) on 2010 July 31 show that emission in all seven of AIAs EUV channels brightenedsimultaneously nearly 6 min before RHESSI or GOES detected emission from plasma at temperatures around 10 MK.Aims. To help interpret these and AIA flare observations in general, we characterized the expected temporal responses of AIAs 94,131, 171, 193, 211, and 335 channels to solar flare brightenings by combining (1) AIAs nominal temperature response functionsavailable through SSWIDL with (2) EUV spectral line data observed in a flare loop

Solar X-rays↗
NASA NTRS2018

Surface Irradiances of Edition 4.0 Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Data Product

The algorithm to produce the Clouds and the Earth’s Radiant Energy System (CERES) Edition 4.0 (Ed4) Energy Balanced and Filled (EBAF)-surface data product is explained. The algorithm forces computed topof- atmosphere (TOA) irradiances to match with Ed4 EBAF-TOA irradiances by adjusting surface, cloud, and atmospheric properties. Surface irradiances are subsequently adjusted using radiative kernels. The adjustment process is composed of two parts: bias correction and Lagrange multiplier. The bias in temperature and specific humidity between 200 and 500 hPa used for the irradiance computation is corrected based on observations by Atmospheric Infrared Sounder (AIRS). Similarly, the bias in the cloud fraction is corrected based on observations by Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat. Remaining errors in surface, cloud, and atmospheric properties are corrected in the Lagrange multiplier process. Ed4 global annual mean (January 2005 through December 2014) surface net shortwave (SW) and longwave (LW) irradiances increase by 1.3Wm22 and decrease by 0.2Wm22, respectively, compared to EBAF Edition 2.8 (Ed2.8) counterparts (the previous version), resulting in an increase in net SW 1LWsurface irradiance of 1.1Wm22. The uncertainty in surface irradiances over ocean, land, and polar regions at various spatial scales are estimated. The uncertainties in all-sky global annual mean upward and downward shortwave irradiance are 3 and 4Wm22, respectively, and the uncertainties in upward and downward longwave irradiance are 3 and 6Wm22, respectively. With an assumption of all errors being independent, the uncertainty in the global annual mean surface LW 1 SW net irradiance is 8Wm22.

Kato, Seiji↗
NASA NTRS2022

Probing the High-energy Gamma-Ray Emission Mechanism in the Vela Pulsar via Phase-resolved Spectral and Energy-dependent Light-curve Modeling

Recent kinetic simulations sparked a debate regarding the emission mechanism responsible for pulsed GeV γ-ray emission from pulsars. Some models invoke curvature radiation, while other models assume synchrotron radiation in the current sheet. We interpret the curved spectrum of the Vela pulsar as seen by H.E.S.S. II (up to ∼100 GeV) and the Fermi Large Area Telescope to be the result of curvature radiation due to primary particles in the pulsar magnetosphere and current sheet. We present phase-resolved spectra and energy-dependent light curves using an extended slot gap and current-sheet model, invoking a step function for the accelerating electric field as motivated by kinetic simulations. We include a refined calculation of the curvature radius of particle trajectories in the lab frame, impacting the particle transport, predicted light curves, and spectra. Our model reproduces the decrease of the flux of the first peak relative to the second one, evolution of the bridge emission, near-constant phase positions of peaks, and narrowing of pulses with increasing energy. We can explain the first of these trends because we find that the curvature radii of the particle trajectories in regions where the second γ-ray light-curve peak originates are systematically larger than those associated with the first peak, implying that the spectral cutoff of the second peak is correspondingly larger. However, an unknown azimuthal dependence of the E field, as well as uncertainty in the precise spatial origin of the GeV emission, precludes a simplistic discrimination of emission mechanisms.

Monica Barnard↗
NASA NTRS2022

Superclustering with the Atacama Cosmology Telescope and Dark Energy Survey. I. Evidence for Thermal Energy Anisotropy Using Oriented Stacking

The cosmic web contains filamentary structure on a wide range of scales. On the largest scales, superclustering aligns multiple galaxy clusters along intercluster bridges, visible through their thermal Sunyaev–Zel'dovich signal in the cosmic microwave background. We demonstrate a new, flexible method to analyze the hot gas signal from multiscale extended structures. We use a Compton y-map from the Atacama Cosmology Telescope (ACT) stacked on redMaPPer cluster positions from the optical Dark Energy Survey (DES). Cutout images from the y-map are oriented with large-scale structure information from DES galaxy data such that the superclustering signal is aligned before being overlaid. We find evidence of an extended quadrupole moment of the stacked y signal at the 3.5σ level, demonstrating that the large-scale thermal energy surrounding galaxy clusters is anisotropically distributed. We compare our ACT × DES results with the Buzzard simulations, finding broad agreement. Using simulations, we highlight the promise of this novel technique for constraining the evolution of anisotropic, non-Gaussian structure using future combinations of microwave and optical surveys.

M. Lokken↗