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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Application and sensitivity investigation of Fourier transforms for microwave radiometric inversions

Existing microwave radiometer technology now provides a suitable method for remote determination of the ocean surface's absolute brightness temperature. To extract the brightness temperature of the water from the antenna temperature equation, an unstable Fredholm integral equation of the first kind was solved. Fast Fourier Transform techniques were used to invert the integral after it is placed into a cross-correlation form. Application and verification of the methods to a two-dimensional modeling of a laboratory wave tank system were included. The instability of the Fredholm equation was then demonstrated and a restoration procedure was included which smooths the resulting oscillations. With the recent availability and advances of Fast Fourier Transform techniques, the method presented becomes very attractive in the evaluation of large quantities of data. Actual radiometric measurements of sea water are inverted using the restoration method, incorporating the advantages of the Fast Fourier Transform algorithm for computations.

Holmes, J. J.↗
NASA NTRS1995

(abstract) A Polarimetric Model for Effects of Brine Infiltrated Snow Cover and Frost Flowers on Sea Ice Backscatter

A polarimetric scattering model is developed to study effects of snow cover and frost flowers with brine infiltration on thin sea ice. Leads containing thin sea ice in the Artic icepack are important to heat exchange with the atmosphere and salt flux into the upper ocean. Surface characteristics of thin sea ice in leads are dominated by the formation of frost flowers with high salinity. In many cases, the thin sea ice layer is covered by snow, which wicks up brine from sea ice due to capillary force. Snow and frost flowers have a significant impact on polarimetric signatures of thin ice, which needs to be studied for accessing the retrieval of geophysical parameters such as ice thickness. Frost flowers or snow layer is modeled with a heterogeneous mixture consisting of randomly oriented ellipsoids and brine infiltration in an air background. Ice crystals are characterized with three different axial lengths to depict the nonspherical shape. Under the covering multispecies medium, the columinar sea-ice layer is an inhomogeneous anisotropic medium composed of ellipsoidal brine inclusions preferentially oriented in the vertical direction in an ice background. The underlying medium is homogeneous sea water. This configuration is described with layered inhomogeneous media containing multiple species of scatterers. The species are allowed to have different size, shape, and permittivity. The strong permittivity fluctuation theory is extended to account for the multispecies in the derivation of effective permittivities with distributions of scatterer orientations characterized by Eulerian rotation angles. Polarimetric backscattering coefficients are obtained consistently with the same physical description used in the effective permittivity calculation. The mulitspecies model allows the inclusion of high-permittivity species to study effects of brine infiltrated snow cover and frost flowers on thin ice. The results suggest that the frost cover with a rough interface significantly increases the backscatter from thin saline ice and the polarimetric signature becomes closer to the isotropic characteristics. The snow cover also modifies polarimetric signatures of thin sea ice depending on the snow mixture and the interface condition.

thin sea ice radar backscatter frost flowers snow ↗
NASA NTRS1978

Relation of laboratory and remotely sensed spectral signatures of ocean-dumped acid waste

Results of laboratory transmission and remotely sensed ocean upwelled spectral signatures of acid waste ocean water solutions are presented. The studies were performed to establish ocean-dumped acid waste spectral signatures and to relate them to chemical and physical interactions occurring in the dump plume. The remotely sensed field measurements and the laboratory measurements were made using the same rapid-scanning spectrometer viewing a dump plume and with actual acid waste and ocean water samples, respectively. Laboratory studies showed that the signatures were produced by soluble ferric iron being precipitated in situ as ferric hydroxide upon dilution with ocean water. Sea-truth water samples were taken and analyzed for pertinent major components of the acid waste. Relationships were developed between the field and laboratory data both for spectral signatures and color changes with concentration. The relationships allow for the estimation of concentration of the indicator iron from remotely sensed spectral data and the laboratory transmission concentration data without sea-truth samples.

Lewis, B. W.↗
NASA NTRS1989

Secular change in chert distribution: a reflection of evolving biological participation in the silica cycle

In the modern oceans, the removal of dissolved silica from sea water is principally a biological process carried out by diatoms, with lesser contributions from radiolaria, silicoflagellates, and sponges. Because such silica in sediments is often redistributed locally during diagenesis to from nodular or bedded chert, stratigraphic changes in the facies distribution of early diagenetic chert provide important insights into the development of biological participation in the silica cycle. The abundance of chert in upper Proterozoic peritidal carbonates suggests that at this time silica was removed from seawater principally by abiological processes operating in part of the margins of the oceans. With the evolution of demosponges near the beginning of the Cambrian Period, subtidal biogenetic cherts became increasingly common, and with the Ordovician rise of radiolaria to ecological and biogeochemical prominence, sedimented skeletons became a principal sink for oceanic silica. Cherts of Silurian to Cretaceous age share many features of facies distribution and petrography but they differ from Cenozoic siliceous deposits. These differences are interpreted to reflect the mid-Cretaceous radiation of diatoms and their subsequent rise to domination of the silica cycle. Biogeochemical cycles provide an important framework for the paleobiological interpretation of the organisms that participate in them.

Non-NASA Center↗
NASA NTRS1968

Ballast barge concept for underwater structures

Ballast barge for underwater structure consists of a reinforced concrete structure partitioned into watertight compartments. The barge structure includes a 3-way venting valve, a compressed air manifold, a master valve for connecting the manifold to an air line, and an open port in each compartment for admitting and expelling sea water.

Payne, V. E.↗
NASA NTRS1968

Proposed gas generation assembly would recover deeply submerged objects

Gas generation system, used for recovery of submerged objects, generates hydrogen gas by the reaction of sodium with sea water. The assembly consists of flooded flotation tanks cabled together, equipped with relief valves to equalize pressure as the array ascends and hydrostatic pressure diminishes, and carrying remotely activated welding units.

Sprague, C. W.↗
NASA NTRS1972

The brightness temperature of the air-sea interface at microwave frequencies

Available results of observation have shown that at nadir the brightness temperature of the sea surface at 19.35 GHz increases linearly with increasing wind speed. The computational results of the modified theoretical model presented are in good agreement with the measurement results both at nadir and other angles. The model depicts that, for a fully developed sea driven by the wind with speed above 5 m/sec, the air in the transitional zone immediately above the air-sea interface is mixed with sea water droplets from bursting air bubbles. The droplet concentration has a profile tapering off to zero at a certain height. The dielectric constant of the inhomogeneous droplet profile is thus both a function of the height above the interface and the wind speed. Both the inhomogeneity effect and the possible attenuation effect of the droplet concentration have been considered.

Tang, C. C. H.↗
NASA NTRS1973

Evaluation of shuttle solid rocket booster case materials. Corrosion and stress corrosion susceptibility of several high temperature materials

Candidate alloys for the Shuttle Solid Rocket Booster (SRB) case were tested under simulated service conditions to define subcritical flaw growth behavior under both sustained and cyclic loading conditions. The materials evaluated were D6AC and 18 Ni maraging steel, both heat treated to a nominal yield strength of 1380 MN/sq m (200 ksi). The sustained load tests were conducted by exposing precracked, stressed specimens of both alloys to alternate immersion in synthetic sea water. It was found that the corrosion and stress corrosion resistance of the 18 Ni maraging steel were superior to that of the D6AC steel under these test conditions. It was also found that austenitizing temperature had little influence on the threshold stress intensity of the D6AC. The cyclic tests were conducted by subjecting precracked surface-flawed specimens of both alloys to repeated load/thermal/environmental profiles which were selected to simulate the SRB missions. It was found that linear removal operations that involve heating to 589 K (600 F) cause a decrease in cyclic life of D6AC steel relative to those tests conducted with no thermal cycling.

Pionke, L. J.↗
NASA NTRS1974

Stress corrosion cracking susceptibility of 18 Ni maraging steel

The stress corrosion cracking (SCC) resistance of 18Ni maraging steel (grades 200, 250, 300, and 350) was determined in 3.5 percent salt (NaCl) solution, synthetic sea water, high humidity, and outside MSFC atmosphere. All grades of the maraging steel were found to be susceptible to SCC in varying degrees according to their strengths, with the lowest strength steel (grade 200) being the least susceptible and the highest strength steel (grade 350), the most susceptible to SCC. The SCC resistance of 250 grade maraging steel was also evaluated in salt and salt-chromate solutions using fracture mechanics techniques. The threshold value, K sub SCC, was found to be approximately 44 MN/sq m square root m, (40 ksi square root in.) or 40 percent of the K sub Q value.

Humphries, T. S.↗
NASA NTRS1973

Mercury: Aspects of its ecology and environmental toxicity

A study was conducted to determine the effects of mercury pollution on the environment. The possible sources of mercury contamination in sea water are identified. The effects of mercury on food sources, as represented by swordfish, are analyzed. The physiological effects of varying concentrations of mercury are reported. Emphasis is placed on the situation existing in the Hawaiian Islands.

Siegel, S. M.↗
NASA NTRS1973

Quantification of the luminescence intensity of natural materials

Review of some of the results of an evaluation of the use of an airborne Fraunhofer line discriminator (FLD) for the detection of sun-stimulated luminescence emitted by rhodamine WT dye and some other materials. Rhodamine dye is reported to have been detected by airborne FDL in sea water in concentrations of less than 2 ppb. Experiments with a fluorescence spectrometer in the laboratory indicate that luminescence of some samples of crude and refined petroleum exceeds the luminescence intensity of rhodamine dye in concentrations of 10 ppm.

Watson, R. D.↗
NASA NTRS1975

Development of a three-dimensional time-dependent flow field model

A three-dimensional, time-dependent mathematical model to represent Mobile Bay was developed. Computer programs were developed which numerically solve the appropriate conservation equations for predicting bay and estuary flow fields. The model is useful for analyzing the dispersion of sea water into fresh water and the transport of sediment, and for relating field and physical model data.

Farmer, R. C.↗
NASA NTRS1975

Microconvection in evaporation and microconvection in ice formation

Absorption of solar radiation by sea water with contact heat exchange and evaporation leads to the formation of a thin cold film on the ocean surface. Microconvection to ice in this thin surface layer is attributed to nonuniform temperature distributions in wind and water and irregular drag by the air currents.

Shumilov, A. V.↗
NASA NTRS1975

Coacervate-like microspheres from lysine-rich proteinoid

Microspheres form isothermally from lysine-rich proteinoid when the ionic strength of the solution is increased with NaCl or other salts. Studies with different monovalent anions and with polymers of different amino acid composition indicate that charge neutralization and hydrophobic bonding contribute to microsphere formation. The particles also form in sea water, especially if heated or made slightly alkaline. The microspheres differ from those made from acidic proteinoid but resemble coacervate droplets in some ways (isothermal formation, limited stability, stabilization by quinone, uptake of dyes). Because the constituent lysine-rich proteinoid is of simulated prebiotic origin, the study is interpreted to add emphasis to and suggest an evolutionary continuity for coacervation phenomena.

Rohlfing, D. L.↗