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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

On the relationship between acoustic energy density flux near the jet and far field acoustic intensity

The relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field directivity and intensity distribution is established by measurement and analysis. The numerical and experimental procedures involved have been checked out by using a known source. The results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number. The implications of these results for sound suppression techniques are discussed.

Maestrello, L.↗
NASA NTRS1974

Variability of intensity ratios of H to He and He to ions with Z not smaller than 3 in solar energetic particle events

Data from the solid-state detector on Explorer 35 are applied to a study of two intensity ratios in the sub-MeV per nucleon specific kinetic energy range for several energetic particle events. It is found that the intensity ratios vary markedly from event to event, particularly during the time history of the individual events. This implies that the ratios have no simple relationship to 'solar abundances' in the usual sense of the term. The pattern of the variability of each ratio is established; the ratio of He to ions with Z not smaller than 3 starts with a low value and increases as the event proceeds. The H/He ratio exhibits a qualitatively similar time history with marked relative enhancement of He early in an event. Differential diffusion of the various ionic species with differing magnetic rigidities is seen to be the dominant physical cause for the variabilities observed.

Van Allen, J. A.↗
NASA NTRS1974

Reinvestigation of rotational-line intensity factors in diatomic spectra

The theory of the intensity factors of rotational lines in diatomic molecular spectra is reviewed with an emphasis on removing obscurities and resolving ambiguities that exist. For example, a unified intensity-factor sum rule is derived that is valid for all spin-allowed and spin-forbidden dipole transitions. Further, it is shown that the electronic transition moments can always be chosen to be real and that a few simple rules ensure the application of consistent phase factors.

Whiting, E. E.↗
NASA NTRS1974

Analytic variational calculation of the ground-state binding energy of hydrogen in intermediate and intense magnetic fields

The present work investigates analytically the effect of an intermediate or intense magnetic field, such as probably exist in white dwarfs and near pulsars, on the binding energy of the hydrogen ground state. A wave-function 'prescription' is given for an analytic variational calculation of the binding energy. The calculation still gives a smooth transition between intermediate and intense fields. An explicit calculation of the ground-state binding energy as B goes to infinity is provided for the Yafet et al. (1956) trial function.

Wilson, L. W.↗
NASA NTRS1974

Intensity variation of ELF hiss and chorus during isolated substorms

Electromagnetic ELF emissions (100-1000 Hz) observed on the polar-orbiting OGO-6 satellite within three hours of the dawn-dusk meridian consistently exhibit a predictable response to isolated substorm activity. Near dawn, the emissions intensify during the substorm and then subside following the magnetic activity; the waves are most intense at L greater than 4, exhibit considerable structure and have been primarily identified as chorus. At dusk the response is entirely different; the wave intensity falls to background levels during substorm activity but subsequently intensifies, usually reaching levels well in excess of that before the disturbance. The emissions near dusk extend to low L, are relatively featureless, and have been identified as plasmaspheric hiss. These features are interpreted in terms of changes in the drift orbits of outer-zone electrons which cyclotron resonate with ELF waves.

Thorne, R. M.↗
NASA NTRS1974

The nu sub 9 fundamental of ethane - Integrated intensity and band absorption measurements with application to the atmospheres of the major planets

Measurements of the absolute intensity and integrated band absorption have been performed for the nu sub 9 fundamental band of ethane. The intensity is found to be about 34 per sq cm per atm at STP, and this is significantly higher than previous estimates. It is shown that a Gaussian profile provides an empirical representation of the apparent spectral absorption coefficient. Employing this empirical profile, a simple expression is derived for the integrated band absorption, which is in excellent agreement with experimental values. The band model is then employed to investigate the possible role of ethane as a source of thermal infrared opacity within the atmospheres of Jupiter and Saturn, and to interpret qualitatively observed brightness temperatures for Saturn.

Varanasi, P.↗
NASA NTRS1974

Transportation vehicle energy intensities. A joint DOT/NASA reference paper

A compilation of data on the energy consumption of air and ground vehicles is presented. The ratio BTU/ASM, British Thermal Units/Available Seat Mile, is used to express vehicle energy intensiveness, and related to the energy consumed directly in producing seat-mile or ton-mile productivity. Data is presented on passenger and freight vehicles which are in current use or which are about to enter service, and advanced vehicles which may be operational in the 1980's and beyond. For the advanced vehicles, an estimate is given of the date of initial operational service, and the performance characteristics. Other key considerations in interpreting energy intensiveness for a given mode are discussed, such as: load factors, operations, overhead energy consumption, and energy investments in new structure and equipment.

Mascy, A. C.↗
NASA NTRS1975

Absolute integrated intensity and individual line parameters for the 6.2-micron band of NO2

The absolute integrated intensity of the 6.2-micron band of NO2 at 40 C was determined from quantitative spectra at about 10 per cm resolution by the spectral band model technique. A value of 1430 plus or minus 300 per sq cm per atm was obtained. Individual line parameters, positions, intensities, and ground-state energies were derived, and line-by-line calculations were compared with the band model results and with the quantitative spectra obtained at about 0.5 per cm resolution.

Goldman, A.↗
NASA NTRS1974

Vibrational intensity distributions for continuum photoionization of oxygen

The paper reports on experimental vibrational intensity distributions for continuum photoionization of oxygen using both 584 and 304 A helium lines. A cylindrical mirror energy analyzer with known transmission properties was used to record photoelectron spectra at a resolution of 45 meV with dispersed He radiation. At each wavelength the vibrational intensity distribution were corrected for the transmission of the analyzer and normalized to 100 at the strongest level. A table lists the results with calculated Franck-Condon factors.

Gardner, J. L.↗
NASA NTRS1975

Lyman-band fluorescence intensity vs H2 pressure

The fluorescence intensity of the H2 Lyman bands excited by the argon 1066 A line is found to be a linear function of the H2 pressure. The fluorescence from naturally occurring HD is linearly dependent on the HD partial pressure. The experiments described show that these fluorescence intensities can be used to measure the H2 and HD densities below 10 trillion molecules per cu cm.

Inn, E. C. Y.↗
NASA NTRS1975

Cosmic ray intensity gradients in the solar system

Recent progress in the determination of cosmic-ray intensity gradients is reviewed. Direct satellite measurements of the integral gradient are described together with various types of indirect measurements, including measurements of the Ar-37/Ar-39 ratio in samples from the Lost City meteorite, studies of anisotropies in neutron-monitor counting rates, and analysis of the sidereal diurnal anisotropy observed at a single point on earth. Nucleonic radial gradients and electron gradients measured by satellites in differential energy windows are discussed, and theoretical studies of the physical processes involved in these gradients are summarized. Observations of intensity gradients in heliographic latitude are reported.

Mckibben, R. B.↗
NASA NTRS1975

Selective attention and the auditory vertex potential. 2: Effects of signal intensity and masking noise

A randomized sequence of tone bursts was delivered to subjects at short inter-stimulus intervals with the tones originating from one of three spatially and frequency specific channels. The subject's task was to count the tones in one of the three channels at a time, ignoring the other two, and press a button after each tenth tone. In different conditions, tones were given at high and low intensities and with or without a background white noise to mask the tones. The N sub 1 component of the auditory vertex potential was found to be larger in response to attended channel tones in relation to unattended tones. This selective enhancement of N sub 1 was minimal for loud tones presented without noise and increased markedly for the lower tone intensity and in noise added conditions.

Schwent, V. L.↗
NASA NTRS1976

Wide range stress intensity factor expressions for ASTM E 399 standard fracture toughness specimens

For each of the two types of specimens, bend and compact, described previously for plane strain fracture toughness of materials, E 399, a polynominal expression is given for calculation of the stress intensity factor, K, from the applied force, P, and the specimen dimensions. It is explicitly stated, however, that these expressions should not be used outside the range of relative crack length, a/W, from 0.45 to 0.55. While this range is sufficient for the purpose of E 399, the same specimen types are often used for other purposes over a much wider range of a/W; for example, in the study of fatigue crack growth. Expressions are presented which are at least as accurate as those in E 399-74, and which cover much wider ranges of a/W: for the three-point bend specimen from 0 to 1; and for the compact specimen from 0.2 to 1. The range has to be restricted for the compact specimen because of the proximity of the loading pin holes to the crackline, which causes the stress intensity factor to be sensitive to small variations in dimensions when a/W is small. This is a penalty inherently associated with the compactness of the specimen.

Srawley, J. E.↗
NASA NTRS1976

Intense soft X-ray flux from Her-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption the luminosity between 0.16 and 1 keV is comparable to that from 2-10 keV. The soft X-rays are modulated with the 1.24 sec period observed at higher energies but are approximately 180 deg out of phase with the high energy flux. These results extend the detection of this flux to higher energy, a different binary phase, and to a time 19 periods (of the 35 day cycle) later. These observations suggest that this soft emission is a stable feature in the spectrum of this source during its X-ray on state and that this emission is local to Her X-1.

Catura, R. C.↗
NASA NTRS1976

Intensity and spectral variations of Cyg X-1 observed from balloons

Observations of Cyg X-1 with a 20 to 200 keV balloon carried X-ray telescope in 1969, 1970, and 1972 are presented. These results reveal the following characteristics of Cyg X-1: The steep spectrum observed at E 10 keV during the radio quiet phase can extend to 200 keV. This phase may have lasted 21 months (July 1969 to March 1971). The low flux values are factors of 3 and 8 below the normal values at 30 and 100 keV respectively, are rarely observed, and may be associated with the early phase of the 1971 April X-ray transition. During some one hour periods, the intensity remained constant to approximately 20% and during other periods it varied a factor 2 in 5 minutes and a factor 10 in 1 hour. Complex spectral variations accompanied the intensity changes.

Matteson, J. L.↗
NASA NTRS1975

Intense soft X-ray flux from Hercules X-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption, the luminosity in the 0.16-0.28 keV band is comparable to that from 2 to 10 keV. This confirms the conclusion of Shulman et al. (1975) but extends the detection of this flux to higher energy, a different binary phase, and to a time 19 periods later in the 35-day cycle. These observations suggest that this soft emission may be a stable feature in the spectrum of Her X-1 during its X-ray on state. It appears difficult to account for the high soft X-ray luminosity by current simple models of the X-ray source.

Catura, R. C.↗
NASA NTRS1975

Strong scintillations in astrophysics. III - The fluctuations in intensity

Fluctuations in intensity due to wave propagation in a wide range of turbulent media, are discussed on the basis of a previously developed theory of strong scintillations. An asymptotic analytic solution to the fourth-moment equation is presented, and its range of validity is discussed. Various parameters characterizing the intensity fluctuations, such as scintillation index and correlation scale, are expressed in terms of turbulence parameters for both Gaussian and power-law irregularity spectra as well as for thick and thin turbulent media.

Lee, L. C.↗