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At least 1,063 records · Page 59

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NASA NTRS1972

Magnetic flux penetration into superconducting thin films.

The quantum-interference technique developed by Meservey (1965) is used to measure directly the absolute value of the penetration depth in lead in tin superconducting thin films. The technique assumes that the change in phase of the superconducting wave function around any contour within the superconductor must be 2 pi n, where n is a nonnegative integer. Results show that the critical current of a superconducting interferometer with two parallel junctions is not strictly periodic in the applied magnetic flux with a period equal to the flux quantum because of the magnetic field dependence of the critical currents of the junctions.

Peabody, G. E.↗

NASA NTRS1972

Diagnostics of nonradially stratified media

The diagnostics of nonradially stratified media are presented. The analysis is applied to distributions lacking spherical symmetry. It is assumed that the medium is thin enough so that the ray remains rectilinear. The data to be used consists of the change in phase of a wave propagated along a ray due to the presence of the medium, for a given set of rays. Two dimensional and three dimensional distributions are considered.

Shmoys, J.↗

NASA NTRS1973

Profiles of emission lines in Be stars. II - Interpretation of the long-period V/R variation.

Investigation of the long-period V/R variation in some Be stars studied by McLaughlin (1966) and others, based on the assumption that the variation is caused by the apsidal motion of an elliptical ring in which the emitting atoms revolve around the star according to Kepler's laws of motion. The results indicate that the behavior of the V/R variation depends upon both the eccentricity and the lateral extent of the gaseous ring. However, if the ring is narrower than a certain limit, the dependence on the width is negligible. In such a case, the eccentricity of the ring can be determined by the observed amplitude of the V/R variation. Based on this model, the radial-velocity curves of both emission edges and central absorption are derived. It is found that they all have the same amplitude, which also depends on the eccentricity, and that all are changing in phase with the V/R variation.

Huang, S.-S.↗

NASA NTRS1971

Analysis of ionospheric refraction error corrections for GRARR systems

A determination is presented of the ionospheric refraction correction requirements for the Goddard range and range rate (GRARR) S-band, modified S-band, very high frequency (VHF), and modified VHF systems. The relation ships within these four systems are analyzed to show that the refraction corrections are the same for all four systems and to clarify the group and phase nature of these corrections. The analysis is simplified by recognizing that the range rate is equivalent to a carrier phase range change measurement. The equation for the range errors are given.

Mallinckrodt, A. J.↗

NASA NTRS1974

Experimental investigation at Mach 8 of the effects of projections and cavities on heat transfer to a model of the Viking aeroshell

An experimental investigation into the aerodynamic heating on a Mars entry vehicle shape with several types of local surface distortion is presented. The configurations tested were 0.033-scale models of a spherically blunted 70 deg half-angle cone with two protuberances of different length, representing the tube leading to the gas chromograph mass spectrometer, and two aeroshell-bioshield attachment points of different size. These models were tested at free-stream Reynolds numbers per meter of 3.7 million and 17 million over an angle-of-attack range from 0 to 18 deg in the Langley Mach 8 variable density hypersonic tunnel. The phase change-coating technique was used to measure heat transfer coefficient. The long protuberance caused more severe interference heating than the short protuberance for the same conditions. When the short projection was located close to the edge of the aeroshell, the interference heating was greater than that on the same projection when located near the vertex. A significant increase in heat transfer coefficient was measured only on the larger aeroshell-bioshield attachment point.

Creel, T. R., Jr.↗

NASA NTRS1974

The problem of the influence of ocean currents on free internal gravity waves

The influence of ocean currents on free internal gravity waves is discussed. The dependence of the parameters of gravity waves on the characteristics of stationary marine currents is described. Necessary conditions for existence of these waves are obtained, and the phenomenon of abrupt changes in phase of the internal oscillation with depth is explained.

Savchenko, V. G.↗

NASA NTRS1974

Thermodynamic perspectives and the origin of life

A qualitative appraisal of a recently enlarged laboratory model for macromolecular and cellular origins is given. The experiments were performed under geologically relevant conditions, i.e., with irreversible thermodynamics, emphasizing open systems and changes in phase. It was found that heating appropriate nonneutral alpha-amino acids with other alpha-amino acids yields partly branched, mainly linear, copolymeric peptides incorporating some of the alpha-amino acids that would of themselves decompose. The resultant copolyamino acids display a high degree of internal order, enzymelike activities, enzymelike characteristics, and a tendency to form a kind of cell having many of the properties of contemporary cells.

Fox, S. W.↗

NASA NTRS1977

Interaction of NaCl/g/ and HCl/g/ with condensed Na2SO4

Na2SO4(l)-NaCl(g) interactions were studied at a total pressure of one atmosphere of air or oxygen for various temperatures of Na2SO4(l) and for various partial pressures of NaCl(g) and H2O(g). Mass spectrometric sampling techniques were used to identify and monitor gas phase species. Continuous recording thermomicrogravimetric measurements were conducted to determine condensed phase weight change rates. Experimental measurements were supplemented with thermodynamic calculations. Numerous experiments were performed at sample temperatures of 900 and 1000 C with 300 ppm NaCl(g). In these experiments, the reproducibility of the Na2SO4 vaporization weight loss rate and initial weight gain upon addition of NaCl(g) were found to be satisfactory. It was found that the addition of NaCl(g) to air flowing over Na2SO4(l) at 900 and 1000 C enhances the rate of weight loss of the Na2SO4(l). This enhancement increases when H2O(g) is also added to the air flow.

Stearns, C. A.↗

NASA NTRS1978

Ultraviolet photometry from the orbiting astronomical observatory. XXX - The Orion reflection nebulosity

Surface-brightness measurements are presented that cover the region of Orion in nine intermediate-width bandpasses ranging from 4250 to 1550 A. The existence of an extended ultraviolet reflection nebulosity in this area is confirmed, and the characteristics of its spectrum and spatial distribution are derived. The observations are consistent with a model in which the dense molecular cloud complex in Orion is illuminated by the foreground Orion aggregate of early-type stars. The interpretation is complicated by the fact that foreground dust may contribute to the observed scattered light. The scattering particles in the cloud appear to exhibit a wavelength-dependent albedo similar to that found for interstellar grains in general, with a strong indication that the phase function changes to a less forward-scattering form in the ultraviolet.

Witt, A. N.↗

NASA NTRS1978

Interpretation of ground-based microwave measurements of the moon using a detailed regolith properties model

A detailed model for the regolith's thermophysical and microwave properties has been used for the interpretation of ground-based measurements of the moon's microwave brightness temperature variation with lunar phase and changes during eclipses. The ground-based measurements include some crucial new lunation variation observations at 2.8, 6.0 and 13.1 cm. The many parameters in the regolith properties model were assigned values based on a careful review of Apollo in situ and lab sample measurements of thermophysical and electrical properties. The first identification of a wavelength-dependent component of scattering is reported.

Gary, B. L.↗

NASA NTRS1980

Phase-angle controller for Stirling engines

An actuator includes a restraint link adapted to be connected with a pivotal carrier arm for a force transfer gear interposed between the crankshaft for an expander portion of a Stirling engine and a crankshaft for the displacer portion of the engine. The restraint link is releasably trapped hydraulic fluid for selectively establishing a phase angle relationship between the crankshaft. A second embodiment incorporates a hydraulic coupler for use in varying the phase angle of gear-coupled crank fpr a Stirling engine whereby phase angle changes are obtainable.

Mcdougal, A. R.↗

NASA NTRS1981

Polarization characteristics of hydromagnetic waves at low geomagnetic latitudes

A field campaign, using three magnetometer stations spaced in latitude around the equatorial magnetic field distance L approximately 1.9, was conducted in early 1979 to investigate the polarization characteristics of hydromagnetic waves at low geomagnetic latitudes. The magnetic pulsations are observed to have periods in the range approximately 20-25 s and to occur primarily in the local morning hours. Statistically, the polarizations at all three stations were predominantly left handed in the local morning hours and right handed in the local afternoon. At the highest-latitude station (L approximately 2) the orientation of the major axis of the polarization ellipse changed from a predominantly NW-SE direction in the local morning to a mixed NW-SE/NE-SW direction in the afternoon. These two statistical results are consistent with the excitation of the waves by the Kelvin-Helmholtz instability at the magnetopause. However, frequent changes in phase are often observed in the magnetic variations, which result in polarization variations on the time scale of minutes, a situation not readily reconcilable with the Kelvin-Helmholtz instability. The existence of the waves at very low latitudes, furthermore, places constraints on the damping rate of externally excited surface waves inside the magnetosphere. We conclude that present theories for hydromagnetic waves in the geomagnetosphere cannot readily incorporate all of these low-latitude results.

Lanzerotti, L. J.↗

NASA NTRS1980

Microwave system performance summary

The design of the microwave system for the solar power satellite is described. Design modifications recommended include changes in phase control to the power module level, a reduction in allowable amplitude jitter, the use of metal matrix waveguides, and sequences for startup/shutdown procedures. Investigations into reshaping the beam pattern to improve overall rectenna collection efficiency and improve sidelobe control are surveyed.

Arndt, G. D.↗

NASA NTRS1981

The annoyance of impulsive helicopter noise

A total of 96 impulsive and non-impulsive sounds were rated for annoyance by 10 subjects. The signals had the same amplitude spectrum with a maximum frequency of 4.75 kHz. By changing the phase of the spectral components different levels of impulsivity were obtained. The signals had coefficients of impulsivity of 10,8, 7,9, and -0.2 respectively. Further, signals had intensity levels 89 and 95 dBA, pulse repetition rates 10 and 20 Hz, and half the signals had pink noise added at a level 12 dBA lower than the level of the sound. The significant results were: The four females and six male subjects rated the impulsive sounds respectively 3.7 dB less annoying and 2.6 dB more annoying than the non-impulsive sounds. Overall, impulsivity had no effect. The hish pulse repetition rate increased annoyance by 2.2 dB. Addition of pink noise increased annoyance of the non-impulsive sounds 1.2 dB, but decreased the annoyance of the impulsive sounds 0.5 dB.

Karamcheti, K.↗

NASA NTRS1982

IUE observations of reflection nebulae

Low-resolution IUE spectra in the SWP and LWR ranges were obtained of several reflection nebulae in the vicinity of their respective illuminating stars. Data for NGC 7023 (HD200775), NGC 1435 (Merope, 23 Tau), NGC 1432 (Maia, 20 Tau) and the Electra (17 Tau) nebula were found to display significant differences in the shape of their normalized nebular spectra. If the dust in these nebulae is similar from one object to the next, these differences can be most readily explained by differences in the line-of-sight dust distribution, coupled with a wavelength-dependent phase function, changing from a strongly forward throwing form (g = 0.6-0.7) in the visible to a more nearly isotropic shape (g approximately 0.25) at 1400A.

Witt, A. N.↗

NASA NTRS1982

Evapotranspiration and remote sensing

There are three things required for evapotranspiration to occur: (1) energy (580 cal/gm) for the change of phase of the water; (2) a source of the water, i.e., adequate soil moisture in the surface layer or in the root zone of the plant; and (3) a sink for the water, i.e., a moisture deficit in the air above the ground. Remote sensing can contribute information to the first two of these conditions by providing estimates of solar insolation, surface albedo, surface temperature, vegetation cover, and soil moisture content. In addition there have been attempts to estimate precipitation and shelter air temperature from remotely sensed data. The problem remains to develop methods for effectively using these sources of information to make large area estimates of evapotranspiration.

Schmugge, T. J.↗

NASA NTRS1983

Flare loop radiative hydrodynamics. IV - Dynamic evolution of unstable semiempirical loop models

The evolution of the unstable solar atmosphere into the nonlinear phase, in response to various perturbations, is followed. The initial dynamic evolution of the atmosphere follows the predictions of linear stability analysis. In the nonlinear phase, rapid changes are confined to the transition region; these changes are manifested as a propagation of the transition region through the plasma, i.e., chromospheric evaporation or condensation. Global evolution therefore proceeds on the coronal conductive time scale. The rate of propagation of the transition region is determined by the imbalance between the energy supplied by thermal conduction from the corona and radiative cooling within the transition region itself. Flow velocities in the lower corona during evaporation or condensation are, in the cases studied, of order 3 km/s. The observed dynamic evolution is consistent with the existence of relatively long-lived coronal loops whose brightnesses vary on the evaporative time scale.

An, C.-H.↗

NASA NTRS1982

Mathematical analysis for radiometric calorimetry of a radiating sphere

Equations are derived from which the temperature dependence of both the specific heat and the thermal diffusivity of a spherical sample of material can be calculated from observations of the time dependence of the surface temperature and the time-rate of energy loss from the sample as it cools. The derivation takes into account the nonuniformity of the interior temperature field of the sample, and the resulting equations can be applied not only to radiative cooling, but also to any other cooling mechanism that does not violate the assumed spherical symmetry. The analysis excludes change of phase, but it does take thermal expansion into account. To permit the making of estimates necessary for the design of radiative cooling experiments, a universal temperature-time cooling curve is derived for the post-transient cooling regime of a radiating sphere of any size with arbitrary, but constant, thermal parameters.

Schmid, L. A.↗