Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “texture”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

River Valley pluton, Ontario - A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

This paper presents Nd, Sr, and Pb isotopic data indicating a late-Archean/early-Proterozoic age for the River Valley anorthositic pluton of the southwestern Grenville Province of Sudbury, Ontario. Pb-Pb isotopic data on 10 whole-rock samples ranging in composition from anorthosite to gabbro yield an age of 2560 + or - 155 Ma. The River Valley pluton is thus the oldest anorthositic intrusive yet recognized within the Grenville Province. The Sm-Nd isotopic system records an age of 2377 + or - 68 Ma. High Pb-208/Pb-204 of deformed samples relative to igneous-textured rocks implies Th introduction and/or U loss during metamorphism in the River Valley area. Rb-Sr data from igneous-textured and deformed samples and from mineral separates give an age of 2185 + or - 105 Ma, indicating substantial disturbance of the Rb-Sr isotopic system.

Ashwal, Lewis D.↗
NASA NTRS1989

High compression image and image sequence coding

The digital representation of an image requires a very large number of bits. This number is even larger for an image sequence. The goal of image coding is to reduce this number, as much as possible, and reconstruct a faithful duplicate of the original picture or image sequence. Early efforts in image coding, solely guided by information theory, led to a plethora of methods. The compression ratio reached a plateau around 10:1 a couple of years ago. Recent progress in the study of the brain mechanism of vision and scene analysis has opened new vistas in picture coding. Directional sensitivity of the neurones in the visual pathway combined with the separate processing of contours and textures has led to a new class of coding methods capable of achieving compression ratios as high as 100:1 for images and around 300:1 for image sequences. Recent progress on some of the main avenues of object-based methods is presented. These second generation techniques make use of contour-texture modeling, new results in neurophysiology and psychophysics and scene analysis.

Kunt, Murat↗
NASA NTRS1989

What if chondritic porous interplanetary dust particles are not the real McCoy

To select a target comet for a Comet Nucleus Sample Return Mission (CNSRM) it is necessary to have an experimental data base to evaluate the extent of diversity and similarity of comets. For example, the physical properties (e.g., low density) of chondritic porous (CP) interplanetary dust particles (IDPs) are believed to resemble these properties of cometary dust although it is yet to be demonstrated that the porous structure of CP IDPs is inherent to presolar dust particles stored in comet nuclei. Porous structures of IDPs could conceivably form during sublimation at the surface of active comet nuclei. Porous structures are also obtained during annealing of amorphous Mg-SiO smokes which initially forms porous aggregates of olivine + platey tridymite and which, upon continued annealing, react to fluffy enstatite aggregates. It is therefore uncertain that CP IDPs are entirely composed of unmetamorphosed presolar dust. Conceivably, new minerals and textures may form in situ in nuclei of active comets as a function of their individual thermal history. Unmetamorphosed comet dust is probably structurally amorphous. Thermal annealing of this dust can produce ultra fine-grained minerals and this ultrafine grain size of CP IDPs should be considered in assessments of aqueous alterations that could affect presolar dust in comet nuclei between 200 and 400 K. Devitrification and hydration may occur in situ in ice-dust mixtures and the mantle of active comet nuclei. Devitrification, or uncontrolled crystallization, of amorphous precursor dust can produce a range of chemical compositions of ultrafine-grained minerals and (non-equilibrium) mineral assemblages and textures in dust contained in comet nuclei as a function of period and trajectory of orbit and number of perihelion passages (not considering internal heating). Thus, experimental data on relevant processes and reaction rates between 200 and 400 K are needed in order to evaluate comet selection, penetration depth for sampling device and curation of samples for CNSRM.

Rietmeijer, Frans J. M.↗
NASA NTRS1989

The effects of atomic oxygen on the thermal emittance of high temperature radiator surfaces

Radiator surfaces on high temperature space power systems such as SP-100 space nuclear power system must maintain a high emittance level in order to reject waste heat effectively. One of the primary materials under consideration for the radiators is carbon-carbon composite. Since carbon is susceptible to attack by atomic oxygen in the low earth orbital environment, it is important to determine the durability of carbon composites in this environment as well as the effect atomic oxygen has on the thermal emittance of the surface if it is to be considered for use as a radiator. Results indicate that the thermal emittance of carbon-carbon composite (as low as 0.42) can be enhanced by exposure to a directed beam of atomic oxygen to levels above 0.85 at 800 K. This emittance enhancement is due to a change in the surface morphology as a result of oxidation. High aspect ratio cones are formed on the surface which allow more efficient trapping of incident radiation. Erosion of the surface due to oxidation is similar to that for carbon, so that at altitudes less than approximately 600 km, thickness loss of the radiator could be significant (as much as 0.1 cm/year). A protective coating or oxidation barrier forming additive may be needed to prevent atomic oxygen attack after the initial high emittance surface is formed. Textured surfaces can be formed in ground based facilities or possibly in space if emittance is not sensitive to the orientation of the atomic oxygen arrival that forms the texture.

Rutledge, Sharon K.↗
NASA NTRS1990

Pristine moon rocks - An alkali anorthosite with coarse augite exsolution from plagioclase, a magnesian harzburgite, and other oddities

Results are presented on the analyses of 18 samples of pristine rocks obtained from the primarily mare Apollo 12 site and from the primarily highland Apollo 14 site, as well as samples from the nonmare Apollo 15 site. It was found that, while two of anorthosites from Apollo 12 were similar in composition to most other anorthosites from the west-central near region, the texture of an alkali anorthosite featured a long and narrow crystal of augite surrounded by a single crystal of plagioclase, clearly suggesting that the augite formed by exsolution out of the plagioclase. Another Apollo 12 rocklet was an unusual magnesian harzburite, with subequal amounts of enstatite and olivine, traces of Cr-Fe spinel, and FeNi metal, but no plagioclase; the bulk composition was found to be remarkably Ir-rich (53 percent) for a pristine rock, and the texture was also unusual. Apollo 14 samples included several uncommonly Al-rich and REE-poor impact melt breccias.

Warren, P. H.↗
NASA NTRS1991

Effects of dust accumulation and removal on radiators surfaces on Mars

Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper and niobium-1 percent-zirconium samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

Gaier, James R.↗
NASA NTRS1991

LDEF contaminants analysis data

Modification of surface texture for Ram Facing FEP Teflon on the Long Duration Exposure Facility (LDEF) satellite is documented. Photos of changes in surface texture if thermal blanket material with position on tray C-08 are presented. Infrared spectra and photographic documentation of molecular film deposits on LDEF surfaces by location is reported. Results of a survey of the functional groups and elemental composition of the brown film found widely distributed on the surface of LDEF is shown. A partial photographic catalog of LDEF particulate contaminants is included. A set of photos of particles collected or photographed in place on the surface of LDEF is shown. Particle counts and surface obscuration data for the LDEF satellite are reported. The surface data in tables and charts is presented for the LDEF satellite by location.

Crutcher, E. Russ↗
NASA NTRS1991

Thermal emittance enhancement of graphite-copper composites for high temperature space based radiators

Graphite-copper composites are candidate materials for space based radiators. The thermal emittance of this material, however, is a factor of two lower than the desired emittance for these systems of greater than or equal to 0.85. Arc texturing was investigated as a surface modification technique for enhancing the emittance of the composite. Since the outer surface of the composite is copper, and samples of the composite could not be readily obtained for testing, copper was used for optimization testing. Samples were exposed to various frequencies and currents of arcs during texturing. Emittances near the desired goal were achieved at frequencies less than 500 Hz. Arc current did not appear to play a major role under 15 amps. Particulate carbon was observed on the surface, and was easily removed by vibration and handling. In order to determine morphology adherence, ultrasonic cleaning was used to remove the loosely adherent material. This reduced the emittance significantly. Emittance was found to increase with increasing frequency for the cleaned samples up to 500 Hz. The highest emittance achieved on these samples over the temperature range of interest was 0.5 to 0.6, which is approximately a factor of 25 increase over the untextured copper emittance.

Rutledge, Sharon K.↗
NASA NTRS1989

The discrimination of sea ice types using SAR backscatter statistics

X-band (HH) synthetic aperture radar (SAR) data of sea ice collected during the Marginal Ice Zone Experiment in March and April of 1987 was statistically analyzed with respect to discriminating open water, first-year ice, multiyear ice, and Odden. Odden are large expanses of nilas ice that rapidly form in the Greenland Sea and transform into pancake ice. A first-order statistical analysis indicated that mean versus variance can segment out open water and first-year ice, and skewness versus modified skewness can segment the Odden and multilayer categories. In additions to first-order statistics, a model has been generated for the distribution function of the SAR ice data. Segmentation of ice types was also attempted using textural measurements. In this case, the general co-occurency matrix was evaluated. The textural method did not generate better results than the first-order statistical approach.

Shuchman, Robert A.↗
NASA NTRS1990

A distinct variant of high-titanium mare basalt from the Van Serg core, Apollo 17 landing site

A fragment of basalt picked from the drive tube collected at Van Serg crater at the Apollo 17 landing site has a bulk chemistry more primitive than that of other high-titanium mare basalt groups collected at the site. The sample has a fine-grained olivine phyric, subophitic texture that is distinct from that of other high-titanium basalt samples. The grain size and texture suggest that the sample has a composition close to that of a magma. The crystallization sequence, with appearance of oxide minerals later than in other groups, and other petrographic features such as more-calcic plagioclase and early pigeonite rather than augite, are consistent with this sample representing a distinct variant of Apollo 17 high-titanium basalts. It is not related through closed-system igneous processes to any of the other mare basalt groups identified among Apollo 17 samples. Its characters emphasize the complexity of contemporaneous magma processes on the moon and the heterogeneity of that part of the mantle that was melted.

Ryder, Graham↗
NASA NTRS1991

Phobos - Spectrophotometry between 0.3 and 0.6 micron and IR-radiometry

A 0.3 - 0.6 micron UV-visible spectrophotometer and a 5 - 50 micron radiometer in the KRFM experiment on Phobos 2 measured two groundtracks in the equatorial region of Phobos. Preliminary results indicate that three surface units can be recognized on the basis of differing UV-visible spectral reflectance properties. One of the units is most comparable spectrally to optically darkened mafic material, and a second is comparable either to anhydrous carbonaceous chondrite or to blackened mafic material. Spectral properties of the third unit do not resemble those of known meteorite types. Brightness temperatures measured by the radiometer are consistent with a typical surface thermal inertia of 1 - 3 x 10 to the -3 cal/(sq cm deg s exp 1/2), as suggested by previous investigations, implying a lunar-like regolith texture. At least one area of possibly higher thermal inertia has been tentatively identified, where a large degraded crater is crossed by several grooves. These results indicate significant lateral heterogeneity in the optical and textural properties of Phobos' surface.

Ksanfomality, L.↗
NASA NTRS1991

Lunar ferroan anorthosite 60025 - Petrology and chemistry of mafic lithologies

Eleven splits from the mafic-mineral-rich part of anorthosite 60025 were studied in order to establish the exact nature and causes of compositional variations in the minerals of lunar ferroan anorthosites. All splits were analyzed by INAA, and five were studied intensively by petrologic techniques. All splits were found to have similar cataclastic textures and show textural evidence of at least two episodes of deformation. The whole-rock split contains mafic minerals having a wide range of compositions and is probably polymict. It is suggested that the rare-earth patterns for all splits can be duplicated safactorily, assuming that the equilibrium liquids had flat, or nearly flat, chondrite-normalized rare-earth patterns. The plagioclases in all splits were found to be identical. Data obtained indicate that in ferroan anorthosites An content in plagioclase and mg' of associated mafic minerals are not strongly correlated.

James, O. B.↗
NASA NTRS1991

Thermal emittance enhancement of graphite-copper composites for high temperature space based radiators

Graphite-copper composites are candidate materials for space based radiators. The thermal emittance of this material, however, is a factor of two lower than the desired emittance for these systems of greater than or equal to 0.85. Arc texturing was investigated as a surface modification technique for enhancing the emittance of the composite. Since the outer surface of the composite is copper, and samples of the composite could not be readily obtained for testing, copper was used for optimization testing. Samples were exposed to various frequencies and currents of arcs during texturing. Emittances near the desired goal were achieved at frequencies less than 500 Hz. Arc current did not appear to play a major role under 15 amps. Particulate carbon was observed on the surface, and was easily removed by vibration and handling. In order to determine morphology adherence, ultrasonic cleaning was used to remove the loosely adherent material. This reduced the emittance significantly. Emittance was found to increase with increasing frequency for the cleaned samples up to 500 Hz. The highest emittance achieved on these samples over the temperature range of interest was 0.5 to 0.6, which is approximately a factor of 25 increase over the untextured copper emittance.

Rutledge, Sharon K.↗
NASA NTRS1991

The perplexing continuum slope of Mars: Effects of thin ferric coatings and viewing geometry

The experiment discussed here was designed to constrain interpretations of variations in continuum slope variations which define several spectral annuli on the flanks of Olympus Mons, observed in the Imaging Spectrometer (IMS) data. The IMS Olympus Mons data reveal that the rings, seen as alternating brighter and darker reflectance in Viking data, correspond to annuli of alternating shallower and steeper continuum slope. At least three factors contributing to continuum slope are identified: ferric coating thickness, viewing geometry, and surface texture. Because the Olympus Mons spectral annuli were observed at nearly constant backscatter geometries in the ISM data, with only slight viewing variations due to the volcanoe's flank slopes, the difference of continuum slope between annuli probably cannot be explained by viewing geometry alone. This suggests that the variation of some fundamental surface characteristics, such as ferric dust/rind thickness or surface texture, is the cause of the Olympus Mons special annuli observed in the ISM imaging spectrometer data.

Fischer, Erich M.↗
NASA NTRS1992

Feature detection in satellite images using neural network technology

A feasibility study of automated classification of satellite images is described. Satellite images were characterized by the textures they contain. In particular, the detection of cloud textures was investigated. The method of second-order gray level statistics, using co-occurrence matrices, was applied to extract feature vectors from image segments. Neural network technology was employed to classify these feature vectors. The cascade-correlation architecture was successfully used as a classifier. The use of a Kohonen network was also investigated but this architecture could not reliably classify the feature vectors due to the complicated structure of the classification problem. The best results were obtained when data from different spectral bands were fused.

Augusteijn, Marijke F.↗
NASA NTRS1991

Properties of large area ErBa2Cu3O(7-x) thin films deposited by ionized cluster beams

ErBa2Cu3O(7-x) films have been produced by simultaneous deposition of Er, Ba, and Cu from three ionized cluster beam (ICB) sources at acceleration voltages of 0.3 to 0.5 kV. Combining ozone oxidation with ICB deposition at 650 C eliminated any need of post annealing processing. The substrates were rotated at 10 rotations per minute during the deposition which took place at a rate of about 3 to 4 nm. Films with areas up to 70 mm in diameter have been made by ICB deposition. These films, 100 nm thick, were deposited on SrTiO3 (100) substrates at 650 C in a mixture of six percent O3 in O2 at a total pressure of 4 x 10(exp -4) Torr. They had T(sub c) ranging from 84.3 K to 86.8 K over a 70 mm diameter and J(sub c) above 10(exp 6) A/sq cm at 77 K. X ray diffraction measurements of the three samples showed preferential c-axis orientation normal to the substrate surface. Scanning electron micrographs (SEM) of the three samples also show some texture dependence on sample position. For the three samples, there is a correlation between SEM texture, full width at half-maximum of rocking curves and J(sub c) versus temperature curves.

Levenson, L. L.↗
NASA NTRS1992

Thermal Control Surfaces Experiment (TCSE) materials analysis

Materials on the Thermal Control Surfaces Experiment (TCSE) underwent changes in their properties during the 5.8 years of exposure to the combined space environment. The analysis of these materials is continuing and current results are discussed. Some materials were significantly degraded such as silver Teflon, S13GLO, and Z302; while others such as Z93 and YB71 were stable. Time dependent flight data is provided, along with preflight and postflight measurements. Results are compared with other experiments, demonstrating the atomic oxygen (AO) ram effect. Atomic oxygen texturing of silver Teflon varies with incident angle. Even indirect exposure to atomic oxygen appears to be involved with surface texturing on the interior of the TCSE. Localized contamination occurred at discrete locations both inside and on exterior surfaces. Most of the visible deposits were the result of the classical photo-enhanced contamination deposition. The synergism of combined space environmental effects is demonstrated by the specific localization of contamination caused by photo-enhanced deposition versus AO removal. Optical degradation measurements of these contaminated areas, utilizing a new portable reflectometer, are presented.

Wilkes, Donald R.↗
NASA NTRS1990

Remote sensing science for the Nineties; Proceedings of IGARSS '90 - 10th Annual International Geoscience and Remote Sensing Symposium, University of Maryland, College Park, May 20-24, 1990. Vols. 1, 2, & 3

Various papers on remote sensing (RS) for the nineties are presented. The general topics addressed include: subsurface methods, radar scattering, oceanography, microwave models, atmospheric correction, passive microwave systems, RS in tropical forests, moderate resolution land analysis, SAR geometry and SNR improvement, image analysis, inversion and signal processing for geoscience, surface scattering, rain measurements, sensor calibration, wind measurements, terrestrial ecology, agriculture, geometric registration, subsurface sediment geology, radar modulation mechanisms, radar ocean scattering, SAR calibration, airborne radar systems, water vapor retrieval, forest ecosystem dynamics, land analysis, multisensor data fusion. Also considered are: geologic RS, RS sensor optical measurements, RS of snow, temperature retrieval, vegetation structure, global change, artificial intelligence, SAR processing techniques, geologic RS field experiment, stochastic modeling, topography and Digital Elevation model, SAR ocean waves, spaceborne lidar and optical, sea ice field measurements, millimeter waves, advanced spectroscopy, spatial analysis and data compression, SAR polarimetry techniques. Also discussed are: plant canopy modeling, optical RS techniques, optical and IR oceanography, soil moisture, sea ice back scattering, lightning cloud measurements, spatial textural analysis, SAR systems and techniques, active microwave sensing, lidar and optical, radar scatterometry, RS of estuaries, vegetation modeling, RS systems, EOS/SAR Alaska, applications for developing countries, SAR speckle and texture.

Source record↗