Search NASA⌕ Search

SEARCH · Search NASA

Results for “logging”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Large impact basins on Mercury and relative crater production rates

Mariner 10 revealed evidence for 40 impact basins having diameters greater than or equal to 200 km on the portion of Mercury imaged at sufficient resolution. A log (cumulative number/unit area) vs. log (diameter) plot for the mercurian basins has a least squares slope of -2. Mercury has (in cumulative number/unit area) only 37 percent as many basins as does the Moon over the entire range of diameters greater than or equal to 300 km. If both the Moon and Mercury have had similar preservation times for craters and if common populations of impactors are involved, then Mars crossers may have been a dominant contribution to the basin forming objects.

Frey, H.↗
NASA NTRS1978

Interpolation and extrapolation of creep rupture data by the Minimum Commitment Method. I - Focal-point convergence. II - Oblique translation. III - Analysis of multiheats

The framework in which minimum-commitment analyses of creep-rupture data can be implemented is outlined. The approach is termed the focal point convergence method (FPCM) because the basic parameter A, also known as stability factor, is geometrically the (imaginary) focal point of convergence of all isothermals when extended to the very long or very short times necessary for such convergence to occur. The method can be implemented either by manual-graphical analysis or by computer code. The method is illustrated in detail for the nickel-base alloy Astroloy, as well as for steels, other nickel-base alloys, and aluminum alloys. The minimum-commitment concept is extended to the analysis of creep-rupture data where each isothermal is generated by an oblique translation of the 'master curve' when plotted on log rupture time and log stress axes. The oblique translation method uses the same types of functions in the FPCM. Approaches for treating multiheats on the basis of the FPCM are discussed in detail.

Manson, S. S.↗
NASA NTRS1979

Fracture modes and acoustic emission of composite materials

Unidirectional fibrous composite material laminae are the construction material of a laminate. Four failure modes can occur in this material, and the identification of these modes is as important as the identification of onset of fracture. Acoustic emission (AE) pulses, generated by the change in the stress field resulting from cracking in a material, have a unique pattern of amplitude distribution that depends only on the mode of fracture and the type of material. By using a tapered double-cantilever beam as grips for the unidirectional lamina, a crack with a constant stress intensity factor was induced, thus eliminating the factor of the stress level. Placing the lamina in different directions relative to the grips imposed a different failure mode. By plotting the log of the relative number of AE pulses above some level versus the log of the relative level, a single constant coefficient can be measured for each material and mode of fracture. The AE energy is proportional to the energy released by the cracking; this proportionality depends on the medium where the AE waves have to travel, and not on the cracking mode.

Rotem, A.↗
NASA NTRS1979

Empirical data on the origin of 'new' comets

The mass distribution of a group of 62 comets from the sample of Marsden et al (1978) was determined by assuming that the size of a comet is in proportion to the surface area of its vaporizing nucleus. A bimodal distribution was found, with a gap between magnitudes 8.1 and 9. The 50 brighter comets (magnitudes 1 to 8) have been tentatively identified as true 'new' comets; their size distribution cannot be fit to a constant slope on a log-log graph. These comets were apparently formed by a mechanism which differs from the fragmentation process. The 12 fainter may be fragments of comets which split or dimmed during their first passages. Results indicate that new comets could be identified with pristine planetesimals; they decay rapidly, probably by splitting when they enter the inner solar system.

Delsemme, A. H.↗
NASA NTRS1979

Apollo-Soyuz survey of the extreme-ultraviolet/soft X-ray background

The paper reports results of the most extensive survey to date of the EUV/soft X-ray background, obtained with an EUV telescope on the Apollo-Soyuz mission. The principal results may be summarized as follows: (1) an intense background flux exists down to energies of 100 eV (4.0 plus or minus 1.3 photons/sq cm/sec/sr/eV average diffuse flux); (2) the Apollo-Soyuz data alone places lower and upper limits on single-temperature models for EUV-emitting interstellar gas for the log T range of 5.1-6.0; and (3) the allowed range would have to be restricted to log T of 5.1-5.6 for the Cash, Malina, and Stern (1976), Burstein et al. (1977), and Apollo-Soyuz data sets to satisfy a single-temperature model for the background at not greater than 280 eV.

Stern, R.↗
NASA NTRS1977

ATS-6 ascending: Near horizon measurements over water at 30 GHz

The return of the ATS 6 satellite to a western longitude during the fall of 1976 presented a unique opportunity to perform low angle of elevation measurements at 30 GHz. For this purpose a receiver using a 1.5 m antenna was set up at Port Aransas, Texas, resulting in a propagation path entirely over water. The 30 GHz beacon was monitored daily for at least one hour from 8 September 1976 to 21 September 1976. During the time the elevation angle changed from 1.5 deg to 17.3 deg, the mean attenuation decreased from 20 dB to 2 dB and the standard deviation from over 6 dB to less than .2 dB. The deep fades at angles below 4 deg show significantly sharper nulls than peaks on a log scale. Spectra of the log amplitude fluctuations vary as the (-8/3) power of the spectral frequency in the limit. A flattening is noticeable at the low frequencies. A precipitation event at 8.5 deg elevation produced a 16 dB fade and significantly increased the variance.

Vogel, W. J.↗
NASA NTRS1980

The distribution of maximum temperatures of coronal active region loops

The emission measure distribution across the range 4.5 log T 6.5 was derived for several coronal active regions by combining EUV line fluxes with broadband X-ray fluxes. The distributions of the maximum temperature was then derived using a numerical model. It is shown that the emission measure distribution can be represented over the full range 5.6 log Tm 6.5 by the superposition of simple loop models, if the models incorporate a substantial rise in their individual emission measure distributions near the maximum temperature. The unresolved loops may have substantial area ratios, since it is this ratio that fixes the extent of the rise in the emission measure distribution. Since the bulk of the emission measure is then contributed from the loop tops, the distribution of maximum temperatures has approximately the same shape as does the integrated emission measure distributions. The EUV and X-ray data used were obtained by from two separate experiments on ATM/Skylab.

Mayfield, E. B.↗
NASA NTRS1980

Film thickness for different regimes of fluid-film lubrication

Film thickness equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic lubrication of low-elastic-modulus materials (soft EHL), or isoviscous-elastic; and elastohydrodynamic lubrication of high-elastic-modulus materials (hard EHL), or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The results are presented as a map of the lubrication regimes, with film thickness contours on a log-log grid of the viscosity and elasticity for three values of the ellipticity parameter.

Hamrock, B. J.↗
NASA NTRS1979

Galactic distribution models of gamma-ray burst sources

The log N-log S relationships for several galactic distribution models of gamma-ray burst sources are derived. The resulting curves are substantially different from the galactic curves usually assumed (slope = -1). There is a relatively weak dependence on the radial distribution assumed but a strong dependence on scale height. Available observational data from several experiments appear to rule out both thin disk distributions and extended halo distributions which have a strong radial density dependence. The prospects are good for obtaining self-consistent distribution data from future large-area detectors.

Fishman, G. J.↗
NASA NTRS1979

Ultraviolet and X-ray observations of Seyfert galaxies and low z QSOs

An analysis of IUE observations of Seyfert galaxies and QSOs indicates that they have the same energy source and heating mechanisms. Neither collisional de-excitation nor simple dust models are sufficient to explain the small L alpha/H beta ratio of Seyfert galaxies and low z QSOs, which is below the recombination value. For Seyfert galaxies, the Log nu (1450) correlates well with Log W lambda (C IV), with a slope similar to that of QSOs. Regarding X-ray fluxes, which were obtained by the A2 experiment onboard the HEAO-1 satellite, the L alpha luminosity correlates well with the continuum luminosity at 1450 A, and there is a positive correlation between the X-ray luminosity and the full line width at zero intensity.

Wu, C.-C.↗
NASA NTRS1979

Large impact basins on Mercury and relative crater production rates

A search for impact basins on Mercury having diameters greater than 200 km revealed evidence for 40 such structures on the 47% of Mercury mapped at sufficient resolution by Mariner 10. This is similar to the number (35) found by Schaber et al. (1977), although there is disagreement in the details of both diameters (for basins observed by them and by the authors) and in the existence of individual basins. The differences are described in detail. A log (cumulative number/unit area)-log (diameter) plot for mercurian basins has a least squares slope of -2; basins show somewhat less scatter about this line than do the Schaber et al. basins. Mercury has (in cumulative number/unit area) only 37% as many basins as does the moon over the entire range of diameters greater than 300 km. If both the moon and Mercury have had similar preservation times for craters and if common populations of impactors are involved, then Mars-crossers may have been a dominant contribution to the basin-forming objects.

Frey, H.↗
NASA NTRS1980

Cosmological considerations on the diffuse gamma-ray isotropic background

Bignami et al (1979) have recently studied the problem of the origin of the diffuse gamma-ray isotropic radiation. They have concluded that within standard cosmology with Lambda = 0 and p = 0, BL Lacertae objects and Seyfert galaxies can account for most of the diffuse radiation if they have not evolved in time. For QSOs, an evolutionary factor is allowed by the data. From the study of radio data, however, it is known that strong evolutionary effects are expected. The discrepancy cannot be explained by changing the geometry of the universe. Contrary to the case of standard cosmology, it is found that in order to fit the diffuse gamma-ray background, the evolutionary function required is almost identical to the one previously determined from the study of the log N-log S relation.

Canuto, V. M.↗
NASA NTRS1980

Crater densities on the satellites of Mars

The density of craters larger than 1 km in diameter has been determined for the entire surface of Phobos, and half that of Deimos. Densities of craters as small as 10 m on Phobos and 5 m on Deimos have been measured for small areas of the satellites. On both objects, crater densities are similar and yield plots which have slopes close to -1.9 on both incremental and cumulative log-log graphs. These densities are close to those expected to obtain under equilibrium conditions. They are also near the maximum predicted, based on the fragmentation lifetimes of the two objects: that is, the densities are near to the maximum possible before such objects are likely to suffer an impact severe enough to disrupt them. While the observed crater densities cannot be converted to absolute ages in any rigorous fashion, they can be understood if the flux at Mars has been similar to that at the Moon and if the surfaces that we see today generally date back to the end of the period of heavy bombardment some 4 billion years ago. It is extremely unlikely that the surfaces are younger than 1 billion years. There are no large areas on Phobos for which crater densities differ by more than a factor of 3 from the average.

Thomas, P.↗
NASA NTRS1979

Velocity dispersions for X-ray-emitting clusters of galaxies

Combining spectroscopy for five clusters of galaxies reported to contain X-ray sources with previously published data for 21 X-ray clusters, suggested correlations between the cluster's velocity dispersions and their X-ray properties have been tested. Unlike previous investigations, it is found that, for all reasonable data subsets, the cluster radial velocity dispersions sigma(r) are correlated with the cluster X-ray luminosities L/x/ at a confidence level exceeding 99%. The best-fit slope of the (log sigma/r/, log L/x/)-relation is somewhat larger than theoretically predicted, but accurate determination of that relation requires further X-ray and optical observations. For the 'most reliable' data subsample a correlation between sigma(r) and the X-ray source temperatures is also found but at a much lower confidence level (85%) than derived by previous investigators from smaller samples.

Hintzen, P.↗
NASA NTRS1980

Mode I fracture behavior of nonlinear materials

A finite element analysis is presented for the Mode I fracture behavior of cracked plates (stationary crack) made of different nonlinear materials (elastoplastic or elastic locking). The assumed stress-strain behavior of the nonlinear materials was piecewise linear. For each given 'stationary' crack size, the corresponding critical remote tensile stress was calculated based on the maximum crack-tip stress failure criterion. It was found that in the log-log plots of the critical remote stress versus critical crack length, the fracture data of the piecewise linear materials obey a 'stepwise-linear-inverse-square-root' fracture law. It is also shown how the fracture data of the piecewise linear materials can be fitted by proper piecewise graphical shifting of the classical 'inverse-square-root' fracture curve for the linearly elastic materials.

Ko, W. L.↗
NASA NTRS1980

Numerical calculations of the collapse of nonrotating, magnetic gas clouds

Results of the first self-consistent numerical calculations of the dynamic collapse of a magnetized protostellar gas cloud are presented. Symmetry about an axis parallel to the initial magnetic field direction has been assumed, so that the calculations could be performed on a two-dimensional grid. Also, the cloud was taken to be nonrotating and isothermal, and the magnetic field was assumed to remain frozen in to the gas. As starting models for the calculations, gas spheres with uniform density and magnetic field were used. The time evolution of the clouds has been calculated for roughly two initial free-fall times, at which point the central density has increased by a factor of approximately 10,000 to 1,000,000. Several such calculations have been performed for different values of the cloud's initial thermal, magnetic, and gravitational energies. In virtually all cases it is found that, once a flattened core forms in the cloud, the central magnetic field strength, B, varies with gas density, rho, according to (d log B/d log rho) = 1/2. This behavior is independent of the initial energy ratios mentioned above. It is also found that the magnetic field is able to prevent completely the collapse of part of the outer envelope of the cloud.

Scott, E. H.↗
NASA NTRS1980

Origin of iron meteorite groups IAB and IIICD

Several low Ni-iron meteorites previously classified with group IAB are reclassified with group IIICD because of lower Ge, Ga, W, and Ir concentrations and higher As concentrations. The low Ni extreme of IIICD is now 62 mg/g, and that of IAB is 64 mg/g. It is proposed that the meteorites of both groups formed as individual shock melts on a chondritic parent body. The differences in log element-log Ni slopes of the daughter irons demonstrate that there were detailed differences in the composition and size of phases in the parental material (e.g., more Ni in the sulfides or metal of IAB, or more Ge and Ir in the oxides of IIICD).

Wasson, J. T.↗
NASA NTRS1980

The thermal decomposition of 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX) and RDXd6 at high temperatures

The ballistics behavior of nitramine propellants containing RDX in an inert binder was examined. It is shown that at 2000 to 5000 psi, depending on the particle size, a slope break or discontinuity in the log burning rate versus log pressure curve occurs. It is shown that at higher pressures the nitramine decomposition proceeds predominately by C-N bond rupture and gives CH2 and N20. At still higher pressures (after the slope break) the decomposition proceeds by N-N rupture. The decomposition of RDX was investigated from 170 to 800 C at atmospheric pressure. The major decomposition products were CH2, CO, CO2, N20, N2, and H20. The ratio of the products varied with the pyrolysis rate and temperature.

Miller, P. J.↗