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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

RNA content in spinal cord motoneurons during hypokinesia

The effect of a diminished motor activity of rats upon the ribonucleic and (RNA) content in a single isolated motoneuron of frontal of their spinal cord was studied. Within a 1 to 30 day exposure of rats to the hypokinetic conditions, RNA content was found to decrease on the 1st, 3rd, and 5th day and to return to the initial level by the 7th day. No changes in RNA content were observed during the subsequent stages of the xperiments. The volume of the nerve cells declined on the 3rd and 5th day, whereas RNA concentration reduced on the 1st, 3rd, 5th, and 30th day.

Gorbunova, A. V.↗
NASA NTRS1979

The equatorial total electron content and shape factor

The diurnal variations of electron content and shape factor observed at an equatorial station during sunspot minimum are shown to be consistent with the electron density profiles observed at Jicamarca during sunspot minimum. The rapid increase in electron content and the shape factor at sunrise results from the EUV production of ionization in the E and F regions. Day-to-day variations in daytime electron content are observed to be quite small at the equator. The evening decrease in the shape factor results from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak or plateau in the shape factor is produced by the slow downward drift of the electron density profile. The deep predawn dip in the shape factor is caused by the main peak of the F layer reaching low altitudes where high loss rates cause a large reduction in ionization below 300 km and very flat electron density profile.

Donnelly, R. F.↗
NASA NTRS1980

Change in energy expenditure and brain and adrenal content of catecholamines in rats during muscular loading and hypokinesia

In male 1-7 month old rats, the growth and the protein content of skeletal muscles were higher than in female rats while the O2 consumption and the heart rate were lower. This is combined with reduction of the thyroid gland weight and of catecholamine content in adrenals at the age of 7 months. The development of male and female rats (1-7 month) under conditions of systematic muscular loads increases the growth tempo and protein of skeletal muscles and intensifies the degree of reduction of energy expenditure and the heart rate. This is accomplished by the greater reduction of relative weight of the thyroid gland and, at the age of 7 months, by reduction of the noradrenaline content in the brainstem. Hypodynamic conditions have the exact opposite effect.

Rozanova, V. D.↗
NASA NTRS1981

Effect of fuel nitrogen and hydrogen content on emissions in hydrocarbon combustion

The results of an investigation of the effect of operating conditions and fuel properties on emission for the two-stage combustion of fuels with significant organic nitrogen content are presented. The way in which the emissions of nitrogen oxides and carbon monoxide are affected by the decreased hydrogen content and the increased organic nitrogen content of coal-derived fuels is discussed. Limited measurements of smoke from the rich-lean combustion of simulated syncrude fuels indicate relatively high smoke emissions in spite of the very lean second-stage burning. This fact, together with the high observed carbon monoxide emissions, suggests that trade-offs will be necessary between the conditions that minimize NOx and those that control CO and smoke emissions.

Bittker, D. A.↗
NASA NTRS1951

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition.

Perkins, Porter J.↗
NASA NTRS1982

Measurement of total electron content of midlatitude ionosphere and protonosphere via Faraday rotation and group relay techniques using transmission from geostationary satellites ATS-3 and ATS-6

Measurement of integrated columnar electron content and total electron content for the local ionosphere and the overlying protonosphere via Faraday rotation and group delay techniques has proven very useful. A field station was established having the geographic location of 31.5 deg N latitude and 91.06 deg W longitude to accomplish these objectives. A polarimeter receiving system was set up in the beginning to measure the Faraday rotation of 137.35 MHz radio signal from geostationary satellite ATS 3 to yield the integrated columnar electron content of the local ionosphere. The measurement was continued regularly, and the analysis of the data thus collected provided a synopsis of the statistical variation of the ionosphere along with the transient variations that occurred during the periods of geomagnetic and other disturbances.

Paul, M. P.↗
NASA NTRS1982

Effect of reduced cobalt contents on hot isostatically pressed powder metallurgy U-700 alloys

The effect of reducing the cobalt content of prealloyed powders of UDIMET 700 (U-700) alloys to 12.7, 8.6, 4.3, and 0% was examined. The powders were hot isostatically pressed into billets, which were given heat treatments appropriate for turbine disks, namely partial solutioning at temperatures below the gamma prime solvus and four step aging treatments. Chemical analyses, metallographic examinations, and X-ray diffraction measurements were performed on the materials. Minor effects on gamma prime content and on room temperature and 650 C tensile properties were observed. Creep rupture lives at 650 C reached a maximum at the 8.4% concentration, while at 760 C a maximum in life was reached at the 4.3% cobalt level. Minimum creep rates increased with decreasing cobalt content at both test temperatures. Extended exposures at 760 and 815 C resulted in decreased tensile strengths and rupture lives for all alloys. Evidence of sigma phase formation was also found.

Harf, F. H.↗
NASA NTRS1982

Estimation of skeletal muscle mass from body creatine content

Procedures have been developed for studying the effect of changes in gravitational loading on skeletal muscle mass through measurements of the body creatine content. These procedures were developed for studies of gravitational scale effects in a four-species model, comprising the hamster, rat, guinea pig, and rabbit, which provides a sufficient range of body size for assessment of allometric parameters. Since intracellular muscle creatine concentration varies among species, and with age within a given species, the concentration values for metabolically mature individuals of these four species were established. The creatine content of the carcass, skin, viscera, smooth muscle, and skeletal muscle was determined for each species. In addition, the skeletal muscle mass of the major body components was determined, as well as the total and fat-free masses of the body and carcass, and the percent skeletal muscle in each. It is concluded that these procedures are particularly useful for studying the effect of gravitational loading on the skeletal muscle content of the animal carcass, which is the principal weight-bearing organ of the body.

Pace, N.↗
NASA NTRS1984

Effects of long-time elevated temperature exposures on hot-isostatically-pressed power-metallurgy Udimet 700 alloys with reduced cobalt contents

Because almost the entire U.S. consumption of cobalt depends on imports, this metal has been designated "strategic'. The role and effectiveness of cobalt is being evaluated in commercial nickel-base superalloys. Udiment 700 type alloys in which the cobalt content was reduced from the normal 17% down to 12.7%, 8.5%, 4.3%, and 0% were prepared by standard powder metallurgy techniques and hot isostatically pressed into billets. Mechanical testing and microstructural investigations were performed. The mechanical properties of alloys with reduced cobalt contents which were heat-treated identically were equal or better than those of the standard alloy, except that creep rates tended to increase as cobalt was reduced. The effects of long time exposures at 760 C on mechanical properties and at 760 C and 845 C on microstructures were determined. Decreased tensile properties and shorter rupture lives with increased creep rates were observed in alloy modifications. The exposures caused gamma prime particle coarsening and formation of sigma phase in the alloys with higher cobalt contents. Exposure at 845 C also reduced the amount of MC carbides.

Hart, F. H.↗
NASA NTRS1984

A System for Controlling the Oxygen Content of a Gas Produced by Combustion

A mixture of air, CH4 and OH(2) is burned in a combustion chamber to produce a product gas in the test section. The OH(2) content of the product gas is compared with the OH(2) content of reference air in an OH(2) sensor. If there is a difference an error signal is produced at the output of a control circuit which by the means of a solenoid valve, regulates the flow of OH(2) into the combustion chamber to make the error signal zero. The product gas in the test section has the same oxygen content as air.

Singh, J. J.↗
NASA NTRS1984

LANDSAT-4 MSS and Thematic Mapper data quality and information content analysis

LANDSAT-4 thematic mapper (TM) and multispectral scanner (MSS) data were analyzed to obtain information on data quality and information content. Geometric evaluations were performed to test band-to-band registration accuracy. Thematic mapper overall system resolution was evaluated using scene objects which demonstrated sharp high contrast edge responses. Radiometric evaluation included detector relative calibration, effects of resampling, and coherent noise effects. Information content evaluation was carried out using clustering, principal components, transformed divergence separability measure, and supervised classifiers on test data. A detailed spectral class analysis (multispectral classification) was carried out to compare the information content of the MSS and TM for a large number of scene classes. A temperature-mapping experiment was carried out for a cooling pond to test the quality of thermal-band calibration. Overall TM data quality is very good. The MSS data are noisier than previous LANDSAT results.

Anuta, P.↗
NASA NTRS1983

The information content of synthetic aperture radar images of terrain

A statistical model is developed that portrays an imaging radar as a noisy communication channel with multiplicative noise, and the model is used to evaluate the average amount of information that can be extracted about a target from its radar image. The average information content is also used to define a measure of radiometric resolution for radar images. It is shown that the information content and the resolution capabilities of an imaging radar reach a limit beyond which an increase in scene dynamic range does not improve the information content or the resolution. This limitation results from the multiplicative nature of the noise introduced in the imaging process.

Frost, V. S.↗
NASA NTRS1984

Landsat-4 MSS and Thematic Mapper data quality and information content analysis

Landsat-4 Thematic Mapper and Multispectral Scanner data were analyzed to obtain information on data quality and information content. Geometric evaluations were performed to test band-to-band registration accuracy. Thematic Mapper overall system resolution was evaluated using scene objects which demonstrated sharp high contrast edge responses. Radiometric evaluation included detector relative calibration, effects of resampling, and coherent noise effects. Information content evaluation was carried out using clustering, principal components, transformed divergence separability measure, and numerous supervised classifiers on data from Iowa and Illinois. A detailed spectral class analysis (multispectral classification) was carried out on data from the Des Moines, IA area to compare the information content of the MSS and TM for a large number of scene classes.

Anuta, P. E.↗
NASA NTRS1984

Beryllium-10 contents of core samples from the St. Severin meteorite

Beryllium-10 contents in the 20-28 dpm/kg range, averaging 24.5 + or - 0.9 dpm/kg, have been obtained for 11 samples taken from along the 35-cm core AIII of the St. Severin LL chondrite. Be-10 content increases with depth in the outermost 8 cm, and there is little change in content at greater depths. Significant disagreement is noted between the measured values and the results of calculations based on the cross sections for proton-induced Be-generating reactions. Cosmogenic Be-10 in stony meteorites is better described as a medium-energy product than a high energy one.

Tuniz, C.↗
NASA NTRS1985

Thermal sensing for characterizing the contents of waste storage drums

The present investigation is concerned with the feasibility to employ remote sensing for the characterization of the contents of liquid chemical waste storage drums. Philipson et al. (1981) had found that, when the air temperature is changing rapidly, differences in the thermal inertia of the drum contents can lead to detectable differences in the skin temperature of the drums. Thus, postsunset, airborne thermal remote sensing could potentially provide some level of discrimination among chemical storage drums. Discrimination should be possible among steel drums filled largely with: (1) aqueous solvents, (2) organic solvents, or (3) clay packing materials. The response of a drum filled with clay packing materials should be similar to that of an empty drum. The reported study had the objective to verify the theoretical findings, taking into account the use of a hand-held infrared radiometer. It was found that under the proper conditions the temperature differences among drums with the three different types of contents will be significant and consistent.

Philpot, W. D.↗
NASA NTRS1986

Total ionospheric electron content calibration using SERIES GPS satellite data

The current status of the Deep Space Network advanced systems research into ionospheric calibration techniques, based on Global Positioning System (GPS) data is described. A GPS-based calibration system is planned to replace the currently used Faraday rotation method by 1989. The SERIES receiver system determines the differential group delay of signals transmitted at two different carrier frequencies. This differential delay includes an ionospheric component and a GPS transmitter offset. The transmitter offsets are different for each GPS satellite. Tests were conducted to assess the effect of the offsets on the ionospheric calibration accuracy. From the obtained data, the total electron content and GPS transmitter offsets are calculated by a least squares estimation method employing a local model of total ionospheric electron content. The end product is an estimation of the total ionospheric content for an arbitrary line-of-sight direction. For the presented polynomial fitting technique, the systematic error due to mismodeling is estimated to be approximately 6 x 10 to the 16th power el/sq m, while the formal error is approximately 2 x 10 to the 16th power el/sq m. The final goal is an error of 3 x 10 to the 16th power el/sq m (approximately 0.7 ns at 2.3 GHz).

Lanyi, G.↗
NASA NTRS1986

The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m(PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. The cobalt levels ranged from 0 wt % to the nominal commercial content in each alloy. The alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200 and 100 hr respectively. An oxidation attack parameter, Ka derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the CR/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr alloys while a 5.0 wt % Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides perhaps due to the formation of the omni-present trirutile Ni(Ta,Cb,Mo,W)2O6. Both scales break down as increasing amounts of NiO is formed.

Barrett, C. A.↗
NASA NTRS1986

Relation between L-band soil emittance and soil water content

An experimental relation between soil emittance (E) at L-band and soil surface moisture content (M) is compared with a theoretical one. The latter depends on the soil dielectric constant, which is a function of both soil moisture content and of soil texture. It appears that a difference of 10 percent in the surface clay content causes a change in the estimate of M on the order of 0.02 cu m/cu m. This is based on calculations with a model that simulates the flow of water and energy, in combination with a radiative transfer model. It is concluded that an experimental determination of the E-M relation for each soil type is not required, and that a rough estimate of the soil texture will lead to a sufficiently accurate estimate of soil moisture from a general, theoretical relationship obtained by numerical simulation.

Stroosnijder, L.↗