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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Chemical analysis of metal and polymer surfaces on the front and rear LDEF

The University of Alabama in Huntsville experiment AO114 contained 128 solid surface samples, half of which were exposed on the front and half on the rear of the Long Duration Exposure Facility (LDEF). Each sample is being subject to a battery of analysis methods. In poster form, details of the x-ray photoelectron spectra, Auger electron spectra, Fourier Transform Infrared and ATR infrared spectra, high resolution profilometry, and scanning electron microscope imagery will be presented from a selection of metal and non-metal surfaces.

Christi, L.↗
NASA NTRS1990

Time-dependent treatment of scattering. II - Novel integral equation approach to quantum wave packets

The novel wave-packet propagation scheme presented is based on the time-dependent form of the Lippman-Schwinger integral equation and does not require extensive matrix inversions, thereby facilitating application to systems in which some degrees of freedom express the potential in a basis expansion. The matrix to be inverted is a function of the kinetic energy operator, and is accordingly diagonal in a Bessel function basis set. Transition amplitudes for various orbital angular momentum quantum numbers are obtainable via either Fourier transform of the amplitude density from the time to the energy domain, or the direct analysis of the scattered wave packet.

Sharafeddin, Omar A.↗
NASA NTRS1991

Determination of the altitude of the nitric acid layer from very high resolution ground-based IR solar spectra

A ground-based solar spectrum at a spectral resolution of about 0.002/cm is used to determine the altitude of the HNO3 layer. The 870/cm spectral region, which is essentially free from absorptions from other species, is employed. The data were obtained with the University of Denver 2.5-m maximum path difference Fourier Transform interferometer spectrometer system. A set of 13 HNO3 vertical profiles were used in the analysis. The best fit obtained for the 'starting' profile (which is centered at 24 km), and the best fit for the profile centered at 26 km are shown. For displacements of greater than 2 km, the discrepancy between the synthetic and observed spectra becomes readily discernible by inspection of the spectra. It is shown that the 'best fit' rms residuals are quite sensitive to the assumed altitude of the HNO3 layer.

Blatherwick, R. D.↗
NASA NTRS1995

ASIC For Complex Fixed-Point Arithmetic

Application-specific integrated circuit (ASIC) performs 24-bit, fixed-point arithmetic operations on arrays of complex-valued input data. High-performance, wide-band arithmetic logic unit (ALU) designed for use in computing fast Fourier transforms (FFTs) and for performing ditigal filtering functions. Other applications include general computations involved in analysis of spectra and digital signal processing.

Petilli, Stephen G.↗
NASA NTRS1998

Solar Flare Physics

We have continued our previous efforts in studies of fourier imaging methods applied to hard X-ray flares. We have performed physical and theoretical analysis of rotating collimator grids submitted to GSFC(Goddard Space Flight Center) for the High Energy Solar Spectroscopic Imager (HESSI). We have produced simulation algorithms which are currently being used to test imaging software and hardware for HESSI. We have developed Maximum-Entropy, Maximum-Likelihood, and "CLEAN" methods for reconstructing HESSI images from count-rate profiles. This work is expected to continue through the launch of HESSI in July, 2000. Section 1 shows a poster presentation "Image Reconstruction from HESSI Photon Lists" at the Solar Physics Division Meeting, June 1998; Section 2 shows the text and viewgraphs prepared for "Imaging Simulations" at HESSI's Preliminary Design Review on July 30, 1998.

Schmahl, Edward J.↗
NASA NTRS2017

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

Evidence of the collisional history of comets and asteroids has been emerging from analyses of cometary forsterite and enstatite returned from Comet Wild 2 by the Stardust mission (Keller et al.Geochim. Cosmochim. Acta 72, 2008; Tomeoka et al. MAPS 43, 2008; Jacobs et al. MAPS 44, 2009). Likewise, shock metamorphism is observed in many meteoritic forsterites and enstatites (McCausland et al. AGU, 2010), suggesting similar collisional histories for asteroids. Further exploration of the effects of collisions is slated for the upcoming Asteroid Impact Mission/Double Asteroid Redirection Test (AIM/DART) mission, expected for launch in 2020. DART will impact Didymoon, the companion of the larger 65803 Didymos (1996 G2) asteroid, and AIM will use its instrumentation to characterize the impact. A suite of relevant impact experiments have been carried out in the Experimental Impact Laboratory at the NASA Johnson Space Center at velocities ranging from approx. 2.0 - 2.8 km/s and temperatures from 25 C to -100 C. Targets include a suite of minerals typically found in cometary dust and in asteroids and meteorites: Mg-rich forsterite (olivine), enstatite (orthopyroxene), diopside (clinopyroxene), magnesite (Mg-rich carbonate), and serpentine (phyllosilicate). Transmission Electron Microscope (TEM) imaging indicates evidence of shock similar to that seen in forsterite and enstatite from Comet Wild 2. Fourier Transform Infrared (FTIR) Spectroscopy will also be used for comparisons with meteorite spectra. A quantitative analysis of the shock pressures required to induce planar dislocations and spectral effects with respect to wavelength will also be presented.

Lederer, Susan M.↗
NASA NTRS1995

Hierarchical analysis of spatial pattern and processes of Douglas-fir forests

There has been an increased interest in the quantification of pattern in ecological systems over the past years. This interest is motivated by the desire to construct valid models which extend across many scales. Spatial methods must quantify pattern, discriminate types of pattern, and relate hierarchical phenomena across scales. Wavelet analysis is introduced as a method to identify spatial structure in ecological transect data. The main advantage of the wavelet transform over other methods is its ability to preserve and display hierarchical information while allowing for pattern decomposition. Two applications of wavelet analysis are illustrated, as a means to: (1) quantify known spatial patterns in Douglas-fir forests at several scales, and (2) construct spatially-explicit hypotheses regarding pattern generating mechanisms. Application of the wavelet variance, derived from the wavelet transform, is developed for forest ecosystem analysis to obtain additional insight into spatially-explicit data. Specifically, the resolution capabilities of the wavelet variance are compared to the semi-variogram and Fourier power spectra for the description of spatial data using a set of one-dimensional stationary and non-stationary processes. The wavelet cross-covariance function is derived from the wavelet transform and introduced as a alternative method for the analysis of multivariate spatial data of understory vegetation and canopy in Douglas-fir forests of the western Cascades of Oregon.

Bradshaw, G. A.↗
NASA NTRSDate not supplied

Structural Dynamic Analysis in Rocket Propulsion and Launch Vehicles

Structural dynamics is one of the critical disciplines for the successful design, development, and testing of space launch vehicles. It is applied from the smallest component (turbine blades), all the way to the entire vehicle, and has to be calculated for every phase of a mission, from ascent and orbit to landing. Successful application of structural dynamics requires extensive knowledge of Fourier techniques, linear algebra, random variables, finite element modeling, and essentials of SDOF and MDOF vibration theory. Working knowledge of fluid dynamics, statistics, and data analysis also extremely useful.

Andrew M Brown↗
NASA NTRS2005

High-resolution spectroscopy of H2SO4, HDSO4, and D2SO4 vapor in the region 1200-10,000 cm(-1)

The high-resolution (0.05 cm(-1)) spectra of gas-phase H2SO4, HDSO4, and D2SO4 were measured over the frequency region 1200-10,000 cm(-1) using Fourier-transform infrared spectroscopy. The increased resolution of this work compared with previous studies has lead to an improved vibrational analysis of H2SO4. This study has answered unresolved questions about combination bands and overlapping features from previous gas-phase spectroscopic studies of H2SO4 and marks the first experimental measurement of the nu8 and nu15 torsional vibrations in this molecule. This work leads to a brief discussion on vibrational mode mixing in sulfuric acid.

Deuterium/chemistry↗
NASA NTRS1991

Line-frequency measurements and analysis of N2O between 900 and 4700/cm

The N2O infrared spectrum from 900 to 4700/cm has been studied with a high-resolution Fourier-transform spectrometer. Measurements were made of line frequencies of several N2O isotopes for several ground-state and hot bands. These bands include the 1530-0330, 2330-0330, 0441-0440, 0441-0330, 0531-0330, and 1331-0330 bands of (N-14)2(O-16). Also, perturbation-enhanced transitions in the 0710-0110 and 0730-0110 bands were assigned and measured. The frequencies have been analyzed to obtain a unique set of effective vibration-rotation parameters for each vibrational state. The results obtained from this research are of high accuracy for the ground-state, and the first-excited-state bands of (N-14)2(O-16), in which the computed frequencies derived from the least-squares fits, are known to an absolute uncertainty of only +/-4 x 10 exp -5 for nonperturbed transitions.

Toth, Robert A.↗
NASA NTRS1987

Damage growth in composite laminates with interleaves

The influence of placing interleaves between fiber reinforced plies in multilayered composite laminates is investigated. The geometry of the composite is idealized as two dimensional, isotropic, linearly elastic media made of a damaged layer bonded between two half planes and separated by thin interleaves of low extensional and shear moduli. The damage in the layer is taken in the form of a symmetric crack perpendicular to the interface and may extend up to the interface. The case of an H-shaped crack in the form of a broken layer with delamination along the interface is also analyzed. The interleaves are modeled as distributed shear and tension springs. Fourier integral transform techniques are used to develop solutions in terms of singular integral equations. An asymptotic analysis of the integral equations based on Muskhelishvili's techniques reveals logarithmically singular axial stresses in the half plane at the crack tips for the broken layer. For the H shaped crack, similar singularities are found to exist in the axial stresses at the interface crack tips in the layer and the half plane. The solution of the equations is found numerically for the stresses and displacements by using the Hadamard's concept of direct differentiation of Cauchy integrals as well as Gaussian integration techniques.

Goree, James G.↗
NASA NTRS1990

SINDA '85/FLUINT, Version 2.2

SINDA, Systems Improved Numerical Differencing Analyzer, software system developed for solving physical problems governed by diffusion-type equations modeled by lumped-parameter representations. Used as general thermal analyzer with resistor-and-capacitor-network representations, adapted to wide range of problems represented by such differential equations as Fourier, Poisson, or LaPlace. Software system updated. FLUINT, FLUid INTegrator, is advanced, one-dimensional fluid-analysis program solving equations of arbitrary fluid-flow networks. Written in FORTRAN and ASSEMBLER.

Cullimore, Brent↗
NASA NTRS1990

Optical and microwave detection using Bi-Sr-Ca-Cu-O thin films

Recent progress at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) in the development of optical and microwave detectors using high temperature superconducting thin films is described. Several objectives of this work have been accomplished, including: deposition of Bi-Sr-Ca-Cu-O thin films by laser abation processing (LAP); development of thin film patterning techniques, including in situ masking, wet chemical etching and laser patterning; measurements of bolometric and non-bolometric signatures in patterned Bi-Sr-Ca-Cu-O films using optical and microwave sources, respectively; analysis and design of an optimized bolometer through computer simulation, and investigation of its use in a Fourier transform spectrometer. The focus here is primarily on results from the measurement of the bolometric and non-bolometric response.

Grabow, B. E.↗
NASA NTRS1990

Monodeuterated methane in the outer solar system. IV - Its detection and abundance on Neptune

The 3nu2 band of CH3D was detected in the spectrum of Neptune near 1.6 micron recorded at a spectral resolution of 4/cm with the Cassegrain Fourier Transportation Spectrometer at the 3.6 m Canada-France-Hawaii Telescope CFHT) on Mauna Kea. The analysis of this spectrum, using spectral synthesis techniques, yielded a CH3D/CH4 ratio of about 0.0006, which corresponds to a global D/H ratio for Neptune of about 0.00012, if CH3D is in isotopic fractionation equilibrium with HD. This value is about an order of magnitude larger than an earlier estimate by Orton et al. (1987) based on deconvolution measurements of unresolved molecular emission in the 8-10-micron region. Comparison of this new determination with previous studies of CH3D in the outer solar system shows that, as in the case of Uranus, the D/H on Neptune is strongly enhanced over that found on Jupiter and Saturn and is comparable to the D/H in methane on Titan and in terrestrial methane and water.

De Bergh, C.↗
NASA NTRS1990

Use of polarization methods in earth resources investigations

The use of polarized light image pairs to investigate earth resources and to make meteorological and oceanographic observations is discussed. The differences between the pairs are found to contain a significant amount of information on contrast, contrast boundaries, shadow, and such terrestrial features as rivers. Combinations of the polarization images were used as input to a principal component analysis, which provided some useful pictorial information not contained in any of the input images. Differencing the Fourier spectra of the polarization image pair showed that significant differences exist between the images in the population, azimuthal distribution, and spatial frequency distribution of contrast boundaries.

Duggin, M. J.↗
NASA NTRS1991

Optical and microwave detection using Bi-Sr-Ca-Cu-O thin films

Recent progress at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) in the development of optical and microwave detectors using high temperature superconducting thin films is described. Several objectives of this work have been accomplished, including: deposition of Bi-Sr-Ca-Cu-O thin films by laser abation processing (LAP); development of thin film patterning techniques, including in situ masking, wet chemical etching, and laser patterning; measurements of bolometric and non-bolometric signatures in patterned Bi-Sr-Ca-Cu-O films using optical and microwave sources, respectively; analysis and design of an optimized bolometer through computer simulation; and investigation of its use in a Fourier transform spectrometer. The focus here is primarily on results from the measurement of the bolometric and non-bolometric response.

Grabow, B. E.↗
NASA NTRS1993

Microwave Holography Helps Improve Performance Of Large Antennas

Report describes use of microwave holography and related techniques of measurement and computation for diagnostics, analysis, and performance improvement of large microwave reflector antennas over all operating frequencies. Technique based on Fourier-transform relationship between complex far-field radiation pattern of antenna at small angles off boresight axis, and complex electromagnetic antenna aperture field distribution, as function of position, expressed in terms of equivalent surface current density.

Rochblatt, David J.↗
NASA NTRS1999

RXTE Observation of Cygnus X-1: III. Implications for Compton Corona and ADAF Models: Implications for Compton Corona and ADAF Models - Report 3

We have recently shown that a 'sphere + disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X-1. Separately, we have analyzed the temporal data provided by RXTE. In this paper we consider the implications of this timing analysis for our best-fit 'sphere + disk' Comptonization models. We focus our attention on the observed Fourier frequency-dependent time delays between hard and soft photons. We consider whether the observed time delays are: created in the disk but are merely reprocessed by the corona; created by differences between the hard and soft photon diffusion times in coronae with extremely large radii; or are due to 'propagation' of disturbances through the corona. We find that the time delays are most likely created directly within the corona; however, it is currently uncertain which specific model is the most likely explanation. Models that posit a large coronal radius [or equivalently, a large Advection Dominated Accretion Flow (ADAF) region] do not fully address all the details of the observed spectrum. The Compton corona models that do address the full spectrum do not contain dynamical information. We show, however, that simple phenomenological propagation models for the observed time delays for these latter models imply extremely slow characteristic propagation speeds within the coronal region.

Nowak, Michael A.↗