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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
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.↗
NASA NTRS1986

Response of some Thematic Mapper band ratios to variation in soil water content

Bidirectional reflectance to nadir in the reflective TM bands and the 1.15-1.3-micron band was measured in the laboratory as moisture content was varied in ten soils. Stronger absorption by water in TM5 and TM7 was expected to cause ratios of other bands to TM5 and TM7 to increase with water content, but in most cases these ratios were constant or decreased at low to intermediate water content and increased only at high moisture levels. Because these ratios were found to decrease as illumination elevation angle decreased, it was suggested that increased roughness resulting from the methods of moistening and mixing the soil may have tended to counteract the expected ratio increases.

Musick, H. Brad↗
NASA NTRS1986

Megaregolith insulation, internal temperatures, and bulk uranium content of the moon

Finite-difference models are used to study the effects of insulation by the megaregolith on lunar thermal evolution. Results indicate that the megaregolith has two important influences on heat flow: (1) Because the megaregolith is exceptionally thin in mare regions, heat passes more readily through them than through highland regions, and even flows laterally from the highland toward the mare. As a result, heat flow is exceptionally high along a boundary between highland and mare regions. (2) On a global scale, megaregolith insulation combined with lithosphere insulation causes slow cooling, which as a cumulative effect results in high present-day mantle temperatures and heat flow. Assuming that the global mean megaregolith thickness is 2 km, a heat flow of 12 mW/sq m is best matched by models with bulk moon U contents of 20-21 ng/g. Independent constraints on lunar internal temperatures derived from magnetic and tectonic data are best matched by models with about 14 ng/g U. Thus the bulk moon U content is roughly 17 ng/g. These results imply that the bulk moon contents of U, and related refractory lithophile elements such as Th, Al, Ca, etc., must be considerably lower than commonly assumed.

Warren, Paul H.↗
NASA NTRS1986

Ionospheric electron content prediction from SERIES/GPS data

Total electron contents along arbitrary lines-of-sight are derived from dual band SERIES P-code data. At present, in a normal observing session, five Global Positioning Satellites (GPS) can be observed for a time interval of 5 h. A SERIES observing session consists of about 300 line-of-sight measurements. Transmitter offsets are different for each satellite and no reliable a priori data can be obtained at present. The electron content and the satellite offsets are estimated simultaneously by a least squares procedure using a simple empirical model. The present accuracy of this technique is estimated to be 6 x 10 to the 16th el/sq m. The results are compared with Faraday rotation measurements. The method may be used for local or global ionospheric content monitoring.

Lanyi, Gabor↗
NASA NTRS1987

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 pct 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 allys while a 5.0 wt pct 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 omnipresent trirutile Ni(Ta, Cb, Mo, W)2O6. Both scales break down as increasing amounts of NiO are formed.

Barrett, Charles A.↗
NASA NTRS1989

A change of mesospheric ozone content under electron precipitation influence

The simulation model of a change of O, O2 and O3 oxygen component content at the heights 50 to 140 km under electron precipitation influence is presented. Parameters of the air mass vertical transfer are introduced into the model. Calculation results showed that after the intense precipitation in approx. 3 days the ozone content increased at heights approx. 80 km. These results agree with the experimentally found effects of the content change under precipitation conditions.

Sosin, I. I.↗
NASA NTRS1990

Low Be-10 and Al-26 contents of ureilites - Production at meteoroid surfaces

The Be-10 contents of 22 ureilites and the Al-26 contents of 18 ureilites are reported. When corrected for exposure age, where known, and for composition, the results give production rate, P that are on average 20 percent lower than values typical of other meteorite classes. This depression of production rates, the weak correlations of both P26 and P10 with Ne-22/Ne-21 and the generally high He-3/Ne-21 and Ne-22/Ne-21 ratios in urelities all suggest that many of the samples occupied near-surface locations in their parent meteoroids. A reduced flux of cosmic rays does not by itself explain the elevated Ne-22/Ne-21 ratios and appears inconsistent with a proposed source for ureilites in the inner asteroid belt. Cosmogenic radionuclide data do not support the tentative pairing of ALHA 78019 with ALHa 78262 proposed on the basis of mineralogical similarities. The high Al-26 content of LEW 85440 may be the result of irradiation by solar cosmic rays.

Aylmer, D.↗
NASA NTRS1990

The H I content of non-isolated galaxies

It seems obvious that the evolution of star formation rate and hence of gas content in galaxies strongly depends on their environment. It reveals itself in particular in enhanced star formation or even in a strong burst of activity of massive stars often observed in interacting galaxies. Nevertheless it should be noted that the time scale for the gas to be exhausted in these galaxies is unknown even approximately. To clarify a role of surroundings in the evolution of disk galaxies we should compare the H I content of isolated and non-isolated galaxies otherwise similar by their properties. It is concluded that there are no systematic differences between H I content in isolated and non-isolated late-type galaxies; in spite of the differences of star formation rates their hydrogen mass is determined by slowly evolving kinematic parameters of the disk. Enhanced star formation in interacting galaxies, if it lasts long enough, must have an initial mass function enriched in massive stars in order not to significantly reduce the supply of gas. Certainly these conclusions are not valid for galaxies which are members of rich clusters such as Virgo or Coma, where H I-deficiency really exists, possibly due to the interaction of interstellar H I with hot intergalactic gas.

Zasov, Anatoli V.↗
NASA NTRS1992

A dual-frequency microwave technique for measuring rainwater content

This study shows that the dual-frequency (38, 25 GHz) differential attenuation (A(38-25)) coefficient can provide accurate estimates of rainwater content W potentially over a wide range of rainwater contents. While measurements along a microwave link are fairly easily implemented, radar estimates of A(38-25) can become clouded by differences between the radar reflectivity factors at the two frequencies (Z38, Z25). Root-mean-square deviations (epsilon) of the estimated W from the actual W are calculated for a wide variety of drop-size distributions and rainwater contents. The computed epsilon include the effects of standard measurement errors and differences between Z38 and Z25. Accurate estimates appear possible using a 38-25-GHz radar when W is not less than 1.5-2 g/cu m, depending upon the desired spatial resolution, and along a microwave link when W is not less than 0.5 g/cu m.

Jameson, A. R.↗
NASA NTRS1992

Ultrasonic evaluation of oxygen content, modulus, and microstructure changes in YBa2Cu3O(7-x) occurring during oxidation and reduction

Ultrasonic velocity measurement techniques were used to evaluate the effects of oxidation and reduction on the elastic properties, global microstructure and oxygen content of the YBa2Cu3O(7-x) ceramic superconductor for samples ranging from 70 to 90 pct of theoretical density. Bulk density, velocity, and elastic modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns were similar after oxidation and reduction treatments for a 90 pct. dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygen content.

Roth, Don J.↗
NASA NTRS1993

Visualizing the semantic content of large text databases using text maps

A methodology for generating text map representations of the semantic content of text databases is presented. Text maps provide a graphical metaphor for conceptualizing and visualizing the contents and data interrelationships of large text databases. Described are a set of experiments conducted against the TIPSTER corpora of Wall Street Journal articles. These experiments provide an introduction to current work in the representation and visualization of documents by way of their semantic content.

Combs, Nathan↗
NASA NTRS1993

Estimating the path-average rainwater content and updraft speed along a microwave link

There is a scarcity of methods for accurately estimating the mass of rainwater rather than its flux. A recently proposed technique uses the difference between the observed rates of attenuation A with increasing distance at 38 and 25 GHz, A(38-25), to estimate the rainwater content W. Unfortunately, this approach is still somewhat sensitive to the form of the drop-size distribution. An alternative proposed here uses the ratio A38/A25 to estimate the mass-weighted average raindrop size Dm. Rainwater content is then estimated from measurements of polarization propagation differential phase shift (Phi-DP) divided by (1-R), where R is the mass-weighted mean axis ratio of the raindrops computed from Dm. This paper investigates these two water-content estimators using results from a numerical simulation of observations along a microwave link. From these calculations, it appears that the combination (R, Phi-DP) produces more accurate estimates of W than does A38-25. In addition, by combining microwave estimates of W and the rate of rainfall in still air with the mass-weighted mean terminal fall speed derived using A38/A25, it is possible to detect the potential influence of vertical air motion on the raingage-microwave rainfall comparisons.

Jameson, Arthur R.↗
NASA NTRS1990

Physical retrieval of precipitation water contents from Special Sensor Microwave/Imager (SSM/I) data. Part 1: A cloud ensemble/radiative parameterization for sensor response (report version)

The physical retrieval of geophysical parameters based upon remotely sensed data requires a sensor response model which relates the upwelling radiances that the sensor observes to the parameters to be retrieved. In the retrieval of precipitation water contents from satellite passive microwave observations, the sensor response model has two basic components. First, a description of the radiative transfer of microwaves through a precipitating atmosphere must be considered, because it is necessary to establish the physical relationship between precipitation water content and upwelling microwave brightness temperature. Also the spatial response of the satellite microwave sensor (or antenna pattern) must be included in the description of sensor response, since precipitation and the associated brightness temperature field can vary over a typical microwave sensor resolution footprint. A 'population' of convective cells, as well as stratiform clouds, are simulated using a computationally-efficient multi-cylinder cloud model. Ensembles of clouds selected at random from the population, distributed over a 25 km x 25 km model domain, serve as the basis for radiative transfer calculations of upwelling brightness temperatures at the SSM/I frequencies. Sensor spatial response is treated explicitly by convolving the upwelling brightness temperature by the domain-integrated SSM/I antenna patterns. The sensor response model is utilized in precipitation water content retrievals.

Olson, William S.↗
NASA NTRS1994

The daytime course of total ozone content caused by cloud convection

Presented are the experimental data on the daytime course of the total O3 and SO2 content obtained by Brewer 044 spectrophotometer in the tropics (Thumba, India, 8.53 N, 76.87 W, March-May 1990) and at middle latitudes (Obninsk, Russia, 55.12 N, 36.6 W, May-October 1991) of the Northern Hemisphere. The analysis showed that under fine warm weather conditions without precipitation (air mass change and frontal passage were not observed during several days) in days with well-developed convective clouds (cloudless morning, convective clouds in the daytime, no clouds in the evening) there is a typical nearly symmetric (with respect to local noon) course of the total O3 (with the minimum at about local noon) and SO2 (with the maximum at about local noon) content. The minimum depth is about 2-5 percent of the average daytime values of the total ozone content. The synchronous measurements of pressure pulsations with microbarograph (they are the indicator of convective and turbulent motion development in the lower subcloud atmospheric layer) showed that during these days there is a nearly symmetric course of pressure pulsations with the maximum at about local noon.

Ishov, Alexander G.↗