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At least 217 records · Page 12

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NASA NTRS1973

Investigation of chemical vapor deposition of garnet films for bubble domain memories

The important process parameters and control required to grow reproducible device quality ferrimagnetic films by chemical vapor deposition (CVD) were studied. The investigation of the critical parameters in the CVD growth process led to the conclusion that the required reproducibility of film properties cannot be achieved with individually controlled separate metal halide sources. Therefore, the CVD growth effort was directed toward replacement of the halide sources with metallic sources with the ultimate goal being the reproducible growth of complex garnet compositions utilizing a single metal alloy source. The characterization of the YGdGaIG films showed that certain characteristics of this material, primarily the low domain wall energy and the large temperature sensitivity, severely limited its potential as a useful material for bubble domain devices. Consequently, at the time of the change from halide to metallic sources, the target film compositions were shifted to more useful materials such as YGdTmGaIG, YEuGaIG and YSmGaIG.

Besser, P. J.↗

NASA NTRS1972

Trace elements profiles, notably Hg, from a preliminary study of the Apollo 15 deep-drill core.

The possible thermal gradient near the surface during a lunation is considered together with the heat flow from the interior, the physical process of Hg migration, the results from core and trench samples from previous missions, and other temperature sensitive phenomena that may help understand the processes. U, Os, and Ru concentrations in the deep drill core samples are of potential interest and are summarized in a table. The Os tends to parallel the Hg profile with depth.

Jovanovic, S.↗

NASA NTRS1972

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration.

Determination of the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. A modified microhardness test unit permitted hardness determinations at homologous temperatures ranging from 0.02 to 0.15, where alloy softening normally occurs in bcc alloys. Results showed that alloy softening was produced by those elements having an excess of s + d electrons compared to Mo while those elements having an equal number or fewer s + d electrons than Mo failed to produce alloy softening. The magnitude of the softening and the amount of solute element at the hardness minimum diminished rapidly with increasing test temperature. At solute concentrations where alloy softening was observed, the temperature sensitivity of hardness was lowered. For solute elements having an excess of s + d electrons or fewer s + d electrons than Mo, alloy softening and alloy hardening can be correlated with the difference in number of s + d electrons of the solute element and Mo.

Stephens, J. R.↗

NASA NTRS1973

Intermediary metabolism during brief and prolonged low tissue temperature

The intermediary metabolism of the depressed metabolic state in the hypothermic hamster and the hibernating ground squirrel was studied by observing acetate and palmitic acid metabolisms in their tissues. The oxidative metabolism seemed to be dominant in the depressed state although synthetic reactions such as fat synthesis proceeded in some cases at a faster rate than normothermic metabolism for the same tissues. Fat syntheses proceeded in all tissues with brown fat and liver especially active. Enzymes for the synthesis of cholesterol seemed to be more temperature sensitive than enzymes for fatty acid synthesis. It was concluded that there are no great differences between metabolisms in hypothermic and hibernating animals.

Enteman, C.↗

NASA NTRS1973

OGO-6 gas-surface energy transfer experiment

The kinetic energy flux of the upper atmosphere was analyzed using OGO-6 data. Energy transfer between 10 microwatts/sq cm and 0.1 W/sq cm was measured by short-term frequency changes of temperature-sensitive quartz crystals used in the energy transfer probe. The condition of the surfaces was continuously monitored by a quartz crystal microbalance to determine the effect surface contamination had on energy accommodation. Results are given on the computer analysis and laboratory tests performed to optimize the operation of the energy transfer probe. Data are also given on the bombardment of OGO-6 surfaces by high energy particles. The thermoelectrically-cooled quartz crystal microbalance is described in terms of its development and applications.

Mckeown, D.↗

NASA NTRS1973

Problems of gaseous motion around stars

A distinction is drawn between radial and tangential modes of ejection from stars, and the possible flow patterns are described. They are: expanding streams, falling streams, jet streams, circulatory streams, and gaseous envelopes. Motion around Be stars is discussed at some length, as a preliminary to studying more complicated flow in binary systems. The rotational velocity of the Be star is insufficient to form the ring. It appears likely that radial instability is temperature sensitive. Rings and disks in binary systems are discussed from the point of view of periodic orbits for particles within the gravitational field of such a system. The formation of these rings is discussed. The expected relation between rotational velocity of the ring and the orbital period is discussed. The relation of circumstellar streams to period changes is mentioned. Finally, the influence of magnetic fields on the circumstellar material and the system is discussed.

Huang, S.-S.↗

NASA NTRS1973

An unidentified absorption in the spectra of C-S stars

An absorption feature in the low-dispersion red spectrograms of carbon Mira variables and C-S stars shown to exhibit strikingly different behavior in these similarly appearing carbon and carbonlike stars. Evidence is presented that in the carbon Miras the feature may be due to unresolved bandheads of the (0,0) system of calcium iodide. In this group of stars the feature exhibits a temperature sensitivity similar to absorptions due to calcium chloride and to the neutral sodium doublet. No identification is suggested for the feature appearing among the C-S stars, though there is evidence against it being composed partially of a zero-volt line of neutral scandium.

Rybski, P. M.↗

NASA NTRS1974

Data book for 12.5-inch diameter SRB thermal model water flotation test; 1.29 psia, series P022

Data acquired from tests conducted to determine how thermal conditions affect SRB (Space Shuttle Solid Rocket Booster) flotation at a scaled pressure of 1.29 psia are presented. Included are acceleration, pressure, and temperature data recorded from initial water impact to final flotation position using a 12.5-inch diameter thermal model of the SRB. Nineteen valid tests were conducted. These thermal tests indicated the following basic differences relative to the ambient temperature and pressure model tests: (1) more water was taken on board during penetration and (2) model flotation/sinking was temperature sensitive.

Allums, S. L.↗

NASA NTRS1977

Foldback current-limiting for hybrid regulator

Technique utilizes operational high gain amplifier, which greatly reduces temperature sensitivity of short circuit current, to amplify and subtract voltage across current sensing resistor from regulated output voltage. Small current sensing resistor may be used to eliminate power loss problem found in conventional circuits.

Crider, C. H.↗

NASA NTRS1976

Influence of acoustics in separation processes

The effects of introducing high energy acoustics into various filtering and drying systems were studied. With very slow velocity filtration systems, it was found that the introduction of acoustics could substantially increase the flow rate and also aided in the coagulation of the particulates before reaching the filter media. In the drying of temperature sensitive powders, the rate was increased by the introduction of acoustics. The acoustic frequency used was 20 kHz with power levels up to 3 watts per square centimeter.

Fairbanks, H. V.↗

NASA NTRS1977

System implications of large radiometric array antennas

Temperature sensitivity degradation due to antenna losses is recognized as a hindrance to extension of available remote-sensing radiometry techniques to larger systems for enhanced spatial resolution. The use of large antennas is also complicated by difficulties with bandwidth and integration time. Advantages of introducing active devices at the subarray level, with distributed Dicke switching or correlation detection, are examined, and their possible contribution to the design of effective imaging microwave radiometers for remote sensing of geophysical parameters (sea state, distribution of sea ice, cloud types and their distributions, soil moisture) is assessed.

Levis, C. A.↗

NASA NTRS1977

Satellite observations of the global distribution of stratospheric ozone

Observations of backscattered radiation from an orbiting geophysical observatory (Ogo) satellite for the period September 1967 to February 1968 have been used to determine the global distribution of ozone at different levels in the middle and upper stratosphere (30-55 km). The derived distributions show significant seasonal and geographic variations with important differences indicated between winter and summer hemisphere distributions. The Ogo-derived distributions are compared with other observations (rocket and satellite) and with photochemical calculations. It is suggested that the increased ozone mixing ratio in the high-latitude winter hemisphere can be accounted for by transport processes up to about 40-45 km and by temperature-sensitive chemistry above.

London, J.↗

NASA NTRS1977

Fresnel-Fizeau effect in a rotating optical fiber ring interferometer

Measurements of the Fresnel-Fizeau effect in a fiber ring interferometer gyroscope are reported. The presence of the dispersion term in the Fresnel drag coefficient was discernable. The temperature dependence of the coefficient bears on the temperature sensitivity of the optical fiber gyroscope. An alternate approach to measuring fiber dispersion is an added benefit, leading to determination of maximum pulse rate transmitted through single-mode fibers.

Vali, V.↗

NASA NTRS1978

The Allende meteorite - Evidence for a new cosmothermometer based on the Ti/3+/ to Ti/4+/ ratio

The mineral thermodynamic condensation sequence is applied to assemblages in Ca-Al-Ti-rich inclusions in the Allende meteorite, and it is suggested that the total amount of titanium and Ti(3+) contents of aluminous clinopyroxenes (fassaites) are temperature sensitive and that the ratio Ti(3+)/Ti(4+) may be used as a qualitative cosmothermometer. The direct gas-to-solid condensation hypothesis is favored because the predicted thermodynamic sequence is followed. Thermodynamic calculations indicate that the condensation interval of Ti(3+) stabilization is 1647-1125 K, while the titanian-fassaites probably condensed in the interval 1625-1349 K. It is suggested that the Allende meteorite has sampled a spectrum of the condensing solar nebula.

Haggerty, S. E.↗

NASA NTRS1979

GEOS 3 STDN S band Doppler tracking investigation

GEOS 3S Doppler band and laser ranging data, acquired from August 1975 to March 1976 in the spacecraft altimeter calibration area, are examined. An evaluation of two-way and three-way Doppler data, for the positioning of Spaceflight Tracking and Data Network S band stations is presented, as well as the Goddard Space Flight Center laser system that is used to reference the exact position of the Doppler stations. The two-way and three-way Doppler tracking devices, situated at Rosman and Bermuda, have yielded data for the recovery of GEOS 3 arc height with an uncertainty of only 1 m. Attention is given to the effects of beacon signal frequency instability, controlled by a temperature sensitive auxiliary crystal oscillator on board the spacecraft, and to the one-way range rate tracking noise that was found to be within a range of 2 to 10 cm/s. 1- and 2-way passes and their different arc meters are graphed, showing the Doppler tracking interval. It was concluded that other accurate computations and recovery of station coordinates could be performed employing tracking data from S band stations.

Rosenbaum, B.↗

NASA NTRS1980

An idealized model of homogeneous solid propellant combustion

The idealization of solid propellant combustion which consists of a single condensed-phase reaction and a single gas-phase reaction is discussed. A limiting-case solution to the gas-phase conservation equations is developed and tested by comparison with transformed thermocouple data. Closed-form expressions are derived for the burning rate and temperature sensitivity. Both quantities are linked explicitly to the solid and gas activation energies. It is concluded that the combustion phenomenology associated with the above idealization is still not fully understood. It is suggested that a careful study of the various limiting-case solutions tempered by a small set of numerical benchmark calculations might further such understanding.

Miller, M. S.↗

NASA NTRS1981

Laboratory evaluation of a pilot cell battery protection system for photovoltaic applications

An energy storage method for the 3.5 kW battery power system was investigated. The Pilot Cell Battery Protection System was tested for use in photovoltaic power systems and results show that this is a viable method of storage battery control. The method of limiting battery depth of discharge has the following advantages: (1) temperature sensitivity; (2) rate sensitivity; and (3) state of charge indication. The pilot cell concept is of interest in remote stand alone photovoltaic power systems. The battery can be protected from damaging overdischarge by using the proper ratio of pilot cell capacities to main battery capacity.

Cataldo, R. L.↗

NASA NTRS1982

Multidisciplinary Research Program in Atmospheric Science

A theoretical analysis of the vertical resolving power of the High resolution Infrared Radiation Sounder (HIRS) and the Advanced Meteorological Temperature Sounder (AMTS) is carried out. The infrared transmittance weighting functions and associated radiative transfer kernels are analyzed through singular value decomposition. The AMTS was found to contain several more pieces of independent information than HIRS when the transmittances were considered, but the two instruments appeared to be much more similar when the temperature sensitive radiative transfer kernels were analyzed. The HIRS and AMTS instruments were also subjected to a thorough analysis. It was found that the two instruments should have very similar vertical resolving power below 500 mb but that AMTS should have superior resolving power above 200 mb. In the layer 200 to 500 mb the AMTS showed badly degraded spread function.

Thompson, O. E.↗