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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Surface acoustical intensity measurements on a diesel engine

The use of surface intensity measurements as an alternative to the conventional selective wrapping technique of noise source identification and ranking on diesel engines was investigated. A six cylinder, in line turbocharged, 350 horsepower diesel engine was used. Sound power was measured under anechoic conditions for eight separate parts of the engine at steady state operating conditions using the conventional technique. Sound power measurements were repeated on five separate parts of the engine using the surface intensity at the same steady state operating conditions. The results were compared by plotting sound power level against frequency and noise source rankings for the two methods.

Mcgary, M. C.↗
NASA NTRS1980

Characterization of three types of silicon solar cells for SEPS Deep Space Mission. Volume 3: Current-voltage characteristics of spectrolab sculptured BSR/P+ (K7), BSR/P+ (K6.5) and BSR (K4.5) cells as a function of temperature and intensity

Three types of high performance silicon solar cells, sculptured BSR/P+(K7), BSR/P+(K6.5) and BSR(K4.5) manufactured by Spectrolab were evaluated for their low temperature and low intensity performance. Sixteen cells of each type were subjected to 11 temperatures and 9 intensities. The sculptured BSR/P+(K7) cells provided the greatest maximum power output both at 1 AU and at LTLI conditions. The average efficiencies of this cell were 14.4 percent at 1 SC/+25 deg C and 18.5 percent at 0.086 SC/-100 deg C.

Whitaker, A. F.↗
NASA NTRS1979

Solar cycle variations in IMF intensity

Annual averages of logarithms of hourly interplanetary magnetic field (IMF) intensities, obtained from geocentric spacecraft between November 1963 and December 1977, reveal the following solar cycle variation. For 2-3 years at each solar minimum period, the IMF intensity is depressed by 10-15% relative to its mean value realized during a broad 9-year period centered at solar maximum. No systematic variations occur during this 9-year period. The solar minimum decrease, although small in relation to variations in some other solar wind parameters, is both statistically and physically significant.

King, J. H.↗
NASA NTRS1979

Quantum-mechanical calculation of three-dimensional atom-diatom collisions in the presence of intense laser radiation

A formalism is presented for describing the collision of fluorine with the hydrogen molecule in the presence of intense radiation. For a laser frequency on the order of the spin-orbit splitting of fluorine, the interaction of the molecular system with the radiation occurs at relatively long range where, for this system, the electric dipole is vanishingly small. Hence the interaction occurs due to the magnetic dipole coupling. Even so, at low collision energies a substantial enhancement of the quenching cross section is found for a radiation intensity of 10 to the 11th W/sq cm.

Devries, P. L.↗
NASA NTRS1979

An angular momentum approximation for molecular collisions in the presence of intense laser radiation

An approximation to a previously presented rigorous description of molecular (atom-atom) collisions occurring in the presence of intense radiation is investigated. This rigorous description explicitly considers the angular momentum transferred between the molecule and the radiation field in the absorption or emission of a photon, but involves a complicated system of close-coupled equations which must be solved independently for each projection M of the initial, total molecular angular momentum. (This is a direct consequence of the lack of rotational invariance in the molecule-field problem). These equations are solved for a model system which mimics the collision of a halogen with a rare gas atom. Empirical observations made in the course of performing these calculations lead to the development of an approximation which avoids the repeated calculations for each initial M. This orientational average approximation greatly reduces the effort required to describe the system, and for the model calculation, yields accurate results for field intensities as high as 10 GW/sq cm.

Devries, P. L.↗
NASA NTRS1980

Temperature dependence of intensities of the 8-12 micron bands of CFCl3

The absolute intensities of the 8-12 micron bands from Freon 11 (CFCl3) were measured at temperatures of 294 and 216 K. Intensities of the bands centered at 798, 847, 934, and 1082 per cm are all observed to depend on temperature. The temperature dependence for the 847 and 1082 per cm fundamental regions is attributed to underlying hot bands; for the nu2 + nu5 combination band (934 per cm), the observed temperature dependence is in close agreement with theoretical prediction. The implication of these results on atmospheric IR remote-sensing is briefly discussed.

Nanes, R.↗
NASA NTRS1979

Stress-intensity factors for two symmetric corner cracks

This paper presents stress-intensity factors, calculated by a three-dimensional finite-element analysis, for shallow or deep quarter-elliptical corner cracks at the edge of a hole in a finite-thickness plate. The plate was subjected to remote uniform tension, remote bending, or simulated pin loading in the hole; a wide range of configuration parameters was investigated. To verify the accuracy of the three-dimensional finite-element models employed, convergence was studied by varying the numbers of degrees of freedom. The stress-intensity factor variations along the crack front are compared with solutions from the literature.

Raju, I. S.↗
NASA NTRS1980

Integrated band intensities of gaseous N/2/O/5/

Values for mid-IR integrated band intensities of gaseous N2O5 were determined at room temperature. The absorptions studied were at 1720, 1246, 743, and 557/cm. The integrated intensities were 2204, 581, 685, and 699/atm cm, respectively. Implications of these results for the stratospheric detection of N(2)O(5) are discussed.

Lovejoy, R. W.↗
NASA NTRS1980

Effect of molecular anisotropy on the intensity and degree of polarization of light scattered from model atmospheres

Computations of the properties of sunlight scattered from models of the earth-atmosphere system are presented to show the effect of molecular anisotropy on the intensity, flux, and degree of polarization of the scattered light. The values of these parameters change significantly when the anisotropy factor is neglected in the molecular optical thickness and scattering phase matrix. However, if the Rayleigh scattering optical thickness is kept constant and the molecular anisotropy factor is included only in the Rayleigh phase matrix, the flux does not change, the intensity changes by a small amount, but the changes in the degree of polarization are still significant.

Bahethi, O. P.↗
NASA NTRS1980

The longitudinal galactic cosmic ray intensity modulation in a diffusive and a scatter-free model of the inner heliosphere

Measurements of energetic solar flare electrons, Jovian electrons, and low-energy solar protons have led to the suggestion that the inner heliosphere is essentially scatter free. Consideration is given to a model in which scattering is only important within the corotating interaction regions (CIR's), while the cavity formed by the CIR's in the inner heliosphere is scatter free, as compared to an interplanetary diffusion model wherein scattering is determined by the solar wind and magnetic field microstructure everywhere in the heliosphere. The two models are compared in terms of the solar wind stream associated Forbush decreases at 1 AU and the longitudinal cosmic ray nucleonic intensity variations at larger heliocentric distances (Pioneer 11 measurements at about 3 AU). It is shown that the diffusion model is able to explain consistently all longitudinal galactic cosmic ray intensity modulation measurements.

Morfill, G.↗
NASA NTRS1980

Galactic cosmic-ray intensity to a heliocentric distance of 18 AU

The paper reports observations to heliocentric radial distances of 8.6 and 18.4 AU with Pioneer 11 and Pioneer 10 respectively. During a seven year period from March 1972 to March 1979, the galactic cosmic-ray intensity of greater than 80 MeV, as measured by detectors on Pioneers 10 and 11, exhibited aperiodic temporal variations by about a factor of 2 and on a time scale of the order of a year, and quasipersistent cyclic variations of a 26 day period and an amplitude of a few percent. For protons of an energy greater than 80 MeV, there is a fairly consistent heliocentric radial gradient of +2.1 (plus or minus 0.3%) per AU in integral intensity until 1978 April-May, at which time a substantial disruption of the distribution of cosmic rays in the heliosphere occurred.

Van Allen, J. A.↗
NASA NTRS1980

Transient stress intensity factors for edge and corner cracks in quench-test specimens

The transient temperature and stress fields in a quenched rectangular bar were computed and used to determine the stress intensity factors for midside and corner-edge cracks. The stress intensity factors, KI, are presented as a function of time, flaw size, and aspect ratio. The variations of KI along the crack edge are given and the self-limiting growth of the crack depth is discussed in relation to the nonlimited surface growth.

Emery, A. F.↗
NASA NTRS1980

Zeeman degeneracy effects in collisional intense-field resonance fluorescence

Resonance fluorescence due to intense laser fields from a Zeeman degenerate atom being perturbed by collisional interactions is calculated in the impact regime by using the quantum-fluctuation-regression theorem. Various interesting effects are found. For example, the scattered intensity spectrum for a J = 0 to J = 1 transition for polarization parallel to the laser polarization is essentially an asymmetric triplet, whereas for a perpendicular polarization due to collisions the spectrum is essentially a doublet (whose frequencies do not correspond with any of those of the triplet). Further, the width of the fluorescent component (whose frequency is close to the unperturbed frequency) actually decreases with increasing laser power.

Cooper, J.↗
NASA NTRS1980

Use of generalized population ratios to obtain Fe XV line intensities and linewidths at high electron densities

A generalized method for obtaining individual level population ratios is used to obtain relative intensities of extreme ultraviolet Fe XV emission lines in the range 284-500 A, which are density dependent for electron densities in the tokamak regime or higher. Four lines in particular are found to attain quite high intensities in the high-density limit. The same calculation provides inelastic contributions to linewidths. The method connects level populations and level widths through total probabilities t(ij), related to 'taboo' probabilities of Markov chain theory. The t(ij) are here evaluated for a real atomic system, being therefore of potential interest to random-walk theorists who have been limited to idealized systems characterized by simplified transition schemes.

Kastner, S. O.↗
NASA NTRS1981

Free-field propagation of high intensity noise

Research on high intensity (finite amplitude) acoustic waves shows that nonlinear distortion effects generally result in a shift of energy to higher frequencies. The higher intensities associated with supersonic jets would therefore indicate that high frequency enhancement of the spectrum should occur, resulting in the differences observed between subsonic and supersonic jets. A 10,000 acoustic watt source installed in an anechoic chamber generates sound levels such that acoustic shocks are readily observable. Dual frequency excitation of the source produces a strong parametric effect with a difference frequency comparable in level to the primary frequency. The test set up and recording equipment being used to determine the finite amplitude noise representative of an actual supersonic jet are described as well as the development of a computer program based on Burger's equation. The spectra of 1/2 octave band, 1 kHz sine wave, and dual frequency input and output are presented in graphs along with waveforms at Z = .025, 0.1, and 1.0.

Mcdaniel, O. H.↗
NASA NTRS1980

Visual evaluation of nystagmus intensity in points to diagnose vestibular dysfunction

The amplitude of nystagmus multiplied by its frequency gives a value commensurate to the velocity of slow phase. If the amplitude and the frequency during the visual observation are expressed in relative units (e.g., in points ranging from 1 to 3) the results of multiplication are used for a relative evaluation of nystagmus intensity. The relative evaluation of nystagmus intensity is used to compare the responses and, in particular, to calculate the coefficients of labyrinth asymmetry and of directional preponderance. A suggestion is made to analyze the formal results of caloric tests using a simple graphic model reflecting the left-right interactions by which the obtained coefficients are conditioned.

Levashov, M. M.↗
NASA NTRS1981

Tropical cyclone intensity change. A quantitative forecasting scheme

One to two day future tropical cyclone intensity change from both a composite and an individual case point-of-view are discussed. Tropical cyclones occurring in the Gulf of Mexico during the period 1957-1977 form the primary data source. Weather charts of the NW Atlantic were initially examined, but few differences were found between intensifying and non-intensifying cyclones. A rawinsonde composite analysis detected composite differences in the 200 mb height fields, the 850 mb temperature fields, the 200 mb zonal wind and the vertical shears of the zonal wind. The individual cyclones which make up the composite study were then separately examined using this composite case knowledge. Similar parameter differences were found in a majority of individual cases. A cyclone intensity change forecast scheme was tested against independent storm cases. Correct predictions of intensification or non-intensification could be made approximately 75% of the time.

Dropco, K. M.↗
NASA NTRS1982

Nitrogen, oxygen and air broadened widths and relative intensities of N2O lines near 2450/cm

Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for/m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20% with the values in this listing.

Hawkins, R. L.↗