Search NASA⌕ Search

SEARCH · Search NASA

Results for “intrinsic”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Methods of reducing low frequency cabin noise and sonically induced stresses, based on the intrinsic structural tuning concept

Control of low frequency interior noise has been difficult in all commercial and general aviation aircraft, since the existing sound attenuation techniques are less effective at these frequencies. Therefore low frequency cabin noise and sonically induced stresses can be reduced mainly by a proper design of the fuselage structure. For this purpose, a concept based on intrinsic tuning and damping of fuselage structural elements has been under development at Boeing for the past three years. This paper describes the results of some laboratory and field tests that were conducted for evaluation of the concept.

Sengupta, G.↗
NASA NTRS1977

Fabrication and performance of intrinsic germanium photodiodes

The paper presents fabrication details for an intrinsic germanium photodiode developed for study of atmospheric constituents, the airglow and auroras in the 1-2 micron spectral range. Attention is given to cutting of the single crystal, spreading of the lithium dispersion, sputtering of a gold coating, and surface passivation. A wavelength response curve is presented.

Beiting, E. J., III↗
NASA NTRS1978

Low frequency cabin noise reduction based on the intrinsic structural tuning concept: The theory and the experimental results, phase 2

Low frequency cabin noise and sonically induced stresses in an aircraft fuselage may be reduced by intrinsic tuning of the various structural members such as the skin, stringers, and frames and then applying damping treatments on these members. The concept is also useful in identifying the key structural resonance mechanisms controlling the fuselage response to broadband random excitation and in developing suitable damping treatments for reducing the structural response in various frequency ranges. The mathematical proof of the concept and the results of some laboratory and field tests on a group of skin-stringer panels are described. In the so-called stiffness-controlled region, the noise transmission may actually be controlled by stiffener resonances, depending upon the relationship between the natural frequencies of the skin bay and the stiffeners. Therefore, cabin noise in the stiffness-controlled region may be effectively reduced by applying damping treatments on the stiffeners.

Sengupta, G.↗
NASA NTRS1978

Illumination-dependent changes in the intrinsic fluorescence of bacteriorhodopsin

The paper describes the intrinsic UV fluorescence of bacteriorhodopsin in some detail and determines the changes during the rapid cyclic reaction following light flashes. The results suggest that several tryptophan residues are affected in the protein, among them one or more exposed to aqueous medium. The kinetics of the fluorescence changes coincide closely with events involving the retinal residue during the deprotonation and reprotonation of the Schiff base group.

Bogomolni, R. A.↗
NASA NTRS1979

Ion exchange with the solar wind for planets with negligible intrinsic magnetic fields

The exchange of ions between the ionosphere of a planet with negligible intrinsic magnetic field, and the solar wind is examined. It is suggested that a balance exists between the outflow of ionospheric ions at the plasmapause and ions from the solar wind in a restricted region close to the subsolar point. This results in a current system towards the subsolar point on the surface of the ionopause and a toroidal magnetic field. Simple calculations are made of the current and field configuration that might result from the system for conditions similar to those encountered on the Viking 1 and 2 transits of the Mars ionosphere.

Nisbet, J. S.↗
NASA NTRS1981

Intrinsic polarization of SS 433 - An electron scattering model

A model for the generation of the observed intrinsic linear polarization in the optical radiation from SS 433 due to scattering from free electrons in highly ionized material in a jet or inclined disk is examined and compared with observational data. Expressions for the Stokes parameters of the linear polarization as a function of phase are obtained for a simple jet model in which continuum light from a point source is singly scattered by free electrons located along the jets resulting in strikingly different relations between Q and U at different values of model parameters. Comparison of 30 broadband linear polarization measurements with the model indicates a mean value of rotation axis inclination to the line of sight of 63 deg, which is not inconsistent with X-ray and radio data. The measurements are also compatible with models invoking highly inclined disks or rings with emission arising in regions on opposite sides of a diameter.

Mclean, I. S.↗
NASA NTRS1980

On the search for an intrinsic magnetic field at Venus

Magnetic field observations obtained by the Pioneer Venus orbiter at low altitude are now available for two sets of orbits in the Venus wake. Data from these 130 orbits are examined for possible surface correlated features or any intrinsic magnetic moment. No surface correlated magnetic fields are observed, but the threshold for the detectability of such fields at Venus is about an order of magnitude greater than at the moon. A surface feature of 10 deg extent would have to create an anomaly of at least 5 gammas at 200 km to be detected in the Pioneer Venus data. Using measurements averaged in 72 10 x 10 deg bins, a planetary magnetic dipole moment of 0.87 + or - 3.00 x 10 to the 21st gauss-cu cm is obtained. Thus the upper limit of the present day Venus moment is less than 4 x 10 to the -5th of the terrestrial moment.

Russell, C. T.↗
NASA NTRS1982

The galaxy as the origin of gamma-ray bursts. II - The effect of an intrinsic burst luminosity distribution on log N/greater than S/ versus log S

The effect of intrinsic burst luminosity distributions on log N-log S has been investigated for halo and disk galactic sources, using a power-law burst luminosity distribution characterized by a shape exponent and a luminosity range. Properly chosen burst luminosity distributions are shown to produce the log N-log S relations sufficiently different from those obtained with monoluminosity bursts to yield halo and thick disk geometries which are compatible with the observations. The soft shape of luminosity distributions capable of altering log N-log S has such observable consequences as (1) gamma-ray burst expected repetitions which first become apparent at lower fluences, and (2) the occurrence of most phenomena at luminosities on the order of about 10 to the 39th ergs, and correspondingly lower fluences.

Jennings, M. C.↗
NASA NTRS1983

Carbon, oxygen and their interaction with intrinsic point defects in solar silicon ribbon material: A speculative approach

Some background information on intrinsic point defects is provided and on carbon and oxygen in silicon in so far as it may be relevant for the efficiency of solar cells fabricated from EFG ribbon material. The co-precipitation of carbon and oxygen and especially of carbon and silicon self interstitials are discussed. A simple model for the electrical activity of carbon-self-interstitial agglomerates is presented. The self-interstitial content of these agglomerates is assumed to determine their electrical activity and that both compressive stresses (high self-interstitial content) and tensile stresses (low self-interstitial content) give rise to electrical activity of the agglomerates. The self-interstitial content of these carbon-related agglomerates may be reduced by an appropriate high temperature treatment and enhanced by a supersaturation of self-interstitials generated during formation of the p-n junction of solar cells. Oxygen present in supersaturation in carbon-rich silicon may be induced to form SiO, precipitates by self-interstitials generated during phosphorus diffusion. It is proposed that the SiO2-Si interface of the precipates gives rise to a continuum of donor stables and that these interface states are responsible for at least part of the light inhancement effects observed in oxygen containing EFG silicon after phosphorus diffusion.

Goesele, U.↗
NASA NTRS1985

The intrinsic ultraviolet continua of O stars

Low-resolution IUE spectra of O and B stars in open clusters have been obtained. The main-sequence B stars are used to derive UV extinction curves for the program clusters, and these curves are used to determine the intrinsic UV to visual colors of O stars in NGC 2244, Trumpler 14, and NGC 6231. These data are analyzed in conjunction with the dereddened colors of O stars with color excesses less than 0.15 mag to obtain a set of reliable UV colors for O3-9, class V-I stars. The results can be summarized as follows: none of the observed O stars have UV colors significantly bluer than a normal B0 V star, and the late O supergiants have significantly redder UV colors than main-sequence O stars, although this luminosity distinction appears to vanish for the early O stars. Several possible explanations for these unexpected results are considered, but none of the presently available nonstandard models are sufficiently developed to be definitively tested.

Massa, D.↗
NASA NTRS1986

The extinction law in the open cluster NGC 457 and the intrinsic energy distribution of Phi Cassiopeiae (F0 Ia)

Five early B-type stars near the main-sequence turnoff in NGC 457 have been observed at low dispersion with the short-wavelength prime and the long-wavelength redundant cameras of the IUE satellite. The equivalent widths of spectral features that are particularly strong and sensitive to temperature and luminosity were computed in the cluster stars and in 20 lightly reddened stars of types O9-B3 and luminosity classes III-V. The comparison of the equivalent widths provides a reliable method for finding matching pairs. Having identified the best comparison star for each program star, binned fluxes were used to determine the mean extinction curve. In order to cover the visible region, monochromatic fluxes of Phi Cas were derived from observations with the intensified Reticon scanner mounted on the No. 2 0.9 m telescope of KPNO, and they were dereddened with the mean extinction curve of Savage and Mathis. Thus, the intrinsic energy distribution of Phi Cas were determined from 1500 to 5800 A for use in a detailed model-atmosphere analysis.

Rosenzweig, P.↗
NASA NTRS1987

Intrinsic frequency spectra of short gravity-capillary waves obtained from temporal measurements of wave height on a lake

Intrinsic frequency spectra of water waves in the range of 6-17 Hz were obtained as a function of both wind speed and wind stress from point measurements of wave height. In a lake with a limited fetch, there are two types of surface motions causing Doppler shift in the frequencies of short waves: orbital velocity of long waves and surface wind drift. The former was estimated from long-wave amplitude by using a linear wave theory. The error in this estimate is of the order of the long-wave slope, and for this work it is typically 10 percent. The latter was approximated by the friction velocity. The friction velocity could be either taken as 3 percent of the mean wind speed measured at a height of 10 m or obtained from direct measurements of the wind stress. The surface drift velocities obtained by these two approaches were found to be in close agreement. Doppler frequency shift can be corrected in either the frequency or the equivalent spatial domain. The two techniques were found to produce comparable results. Experimental results showed that the spectral energy of short waves rapidly increased in response to increasing winds and jumped up by an order of magnitude when wave breaking occurred.

Atakturk, S. S.↗
NASA NTRS1987

Ultraviolet interstellar extinction toward NGC 6530 and the intrinsic energy distribution of 9 Sagittarii and HD 165052

The ultraviolet interstellar extinction curve is determined toward 12 early B main-sequence stars and one O8 V star in NGC 6530. The extinction is found to be uniform across the cluster. At short wavelengths, the extinction curve of NGC 6530 falls below the average Galactic curve by a full magnitude, indicating that the population of small grains relative to larger grains is lower than normal. Longward of 2830 A the curve is almost coincident with the mean Galactic curve. The 2175 A feature is narrower than the average. The derived extinction curve is used to deredden the observed fluxes of two early O-type stars in NGC 6530:9 Sgr and HD 165052. The intrinsic continua are compared to model atmospheres in the region 1200-8200 A. The LTE, line-blanketed models of Kurucz (1979) fit the observations better than the non-LTE, unblanketed models of Mihalas (1972) suggesting that line-blanketing effects are more important than the non-LTE effects in the atmospheres of these stars. The temperatures of the models that best fit the observations are lower than the Zanstra temperatures and the temperatures estimated from the strengths of the He I and He II lines, by 10,000 to 20,000 K.

Torres, Ana V.↗
NASA NTRS1987

Intrinsically variable stars

The characteristics of intrinsically variable stars are examined, reviewing the results of observations obtained with the IUE satellite since its launch in 1978. Selected data on both medium-spectral-class pulsating stars (Delta Cep stars, W Vir stars, and related groups) and late-type variables (M, S, and C giants and supergiants) are presented in spectra, graphs, and tables and described in detail. Topics addressed include the calibration of the the period-luminosity relation, Cepheid distance determination, checking stellar evolution theory by the giant companions of Cepheids, Cepheid masses, the importance of the hydrogen convection zone in Cepheids, temperature and abundance estimates for Population II pulsating stars, mass loss in Population II Cepheids, SWP and LWP images of cold giants and supergiants, temporal variations in the UV lines of cold stars, C-rich cold stars, and cold stars with highly ionized emission lines.

Bohm-Vitense, Erika↗
NASA NTRS1988

The einstein equivalence principle, intrinsic spin and the invariance of constitutive equations in continuum mechanics

The invariance of constitutive equations in continuum mechanics is examined from a basic theoretical standpoint. It is demonstrated the constitutive equations which are not form invariant under arbitrary translational accelerations of the reference frame are in violation of the Einstein equivalane principle. Furthermore, by making use of an analysis based on statistical mechanics, it is argued that any frame-dependent terms in constitutive equations must arise from the intrinsic spin tensor and are negligible provided that the ratio of microscopic to macroscopic time scales is extremely small. The consistency of these results with existing constitutive theories is discussed in detail along with possible avenues of future research.

Speziale, Charles G.↗
NASA NTRS1987

Intrinsic asymmetry in NGC 6251

The giant radio galaxy NGC 6251, which has a one-sided 'core-jet' structure on parsec scales and sufficient density for mapping with the Mark II VLBI system, is studied. The large-scale radio structure of this source suggests that it is not being seen 'end-on' and that the basic relativistic beaming model thus does not explain the observed asymmetry in this source. The possibility that the parsec-scale asymmetry in the source is due to intrinsic factors is discussed.

Jones, Dayton L.↗
NASA NTRS1988

Intrinsic oxygen fugacity measurements of some Allende Type B inclusions

The intrinsic oxygen fugacities (IOFs) of two type B Ca-rich and Al-rich inclusions (CAI) from the Allende meteorite were measured using the solid-electrolyte double-cell IOF technique of Ulmer et al. (1976). The measurements were compared to calculated and experimentally extrapolated fO2 of type B phases. It was found that the IOFs of the type B are 6-8 orders of magnitude more oxidized (H2/H2O = 1-10) than the canonical solar nebular gas (H2/H2O = 100-2000). It is suggested that some local fO2 enhancing mechanism, such as dust or gas concentrations, or the release of oxygen-rich vapors during CAI volatilization in the type B inclusions was in operation at temperatures higher than 700 C.

Kozul, Jean M.↗
NASA NTRS1989

Intrinsic ultraviolet (912-3200 A) energy distribution of OB stars

Low-dispersion 500-3200-A spectra of 20 OB stars are used to derive three individual extinction curves in the wavelength range 912-1200 A. The dependence of the intrinsic UV fluxes of OB stars on both spectral type and luminosity is demonstrated. UV color indices are proposed. The results confirm the previous finding that O star spectra are not significantly bluer than the spectrum of the B0 main-sequence star Upsilon Ori.

Longo, Renata↗