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  • 1
    Publikationsdatum: 2006-06-26
    Beschreibung: Results of an assessment of the public risk associated with the release of carbon fibers from crash-fire accidents of civil aircraft having carbon composite structures are presented. The overall national impact is shown to be extremely low in 1993. Personal injury is found to be extremely unlikely. Based on these findings, the risk of electrical failure from carbon fibers should not prevent the exploitation of composites in aircraft, and additional protection of aircraft avionics to guard aginst carbon fibers is unnecessary.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Selected NASA Res. in Composite Mater. and Struct.; p 183-234
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  • 2
    Publikationsdatum: 2006-06-26
    Beschreibung: A fatigue analysis technique developed to predict damage growth in notched laminates is described. Features of the analysis include: criteria to relate matrix failure to cyclic stresses in and between plies; correlation of delamination growth with strain-release rate; and in-plane shear modulus change is related to cyclic shear stresses. A simplified finite element model is used to determine stresses in laminates that contain matrix damage. Failure criteria are integrated with the finite element model to form the fatigue analysis.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Selected NASA Res. in Composite Mater. and Struct.; p 79-106
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  • 3
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    In:  CASI
    Publikationsdatum: 2006-06-26
    Beschreibung: The damage tolerance of composites was investigated. Results show that severe degradation in material strength may occur due to impact damage and that reduced strain allowables should be considered to compensate for possible impact damage. The mechanisms of failure involved in impact so that local damage will be reduced and arrest of propagating fracture initiated at impact locations are examined. Compression strength reductions for damage due to impact by a 1.27 cm diameter spherical projectile in thick laminates representative of wing skin panels are presented. Also discussed are the results of concepts recently evaluated to improve damage tolerance. These concepts range from improvements at the materials level to advanced structural configurations designed to arrest or limit the growth of propagating fractures. The results indicate that substantial improvements in the damage tolerance of graphite-epoxy composite structures can be achieved through the proper combination of materials and structural design.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Selected NASA Res. in Composite Mater. and Struct.; p 107-142
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  • 4
    Publikationsdatum: 2006-06-26
    Beschreibung: Progress in the development of verified design technology for generic advanced-composite structural components loaded in compression is reported. Generic structural configurations material systems and load ranges of interest for a given application were investigated using structural procedures, structural analysis procedures, and laboratory testing of structural specimens. Both flat and curved composite compression panels that are designed either to be buckling resistant or to have postbuckling strength depending on the expected application of the panels were considered.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Selected NASA Res. in Composite Mater. and Struct.; p 35-78
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  • 5
    Publikationsdatum: 2006-06-26
    Beschreibung: The degree of notch sensitivity of composites in compression and whether their failures can be predicted over a wide range of plate and hole sizes. The notch sensitivity of composites is investigated by comparing actual failure loads of laminates with circular holes, with the extreme failure that would be expected from an ideal notch insensitive material and from an ideal notch sensitive material. The predictability question is addressed by applying the point stress failure criterion to a wide range of plate widths and hole sizes and comparing with available experimental data. The severity of impact is explored by comparing strength reductions resulting from impact with those resulting from comparable size circular holes. Finally, comparison is made of the differences to be expected from the effects of cracks and circular holes on failure strength.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Selected NASA Res. in Composite Mater. and Struct.; p 1-33
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  • 6
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 240-241
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  • 7
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 236-237
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  • 8
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 238-239
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  • 9
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 234-235
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  • 10
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 231
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  • 11
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 229-230
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  • 12
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 232-233
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  • 13
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 227-228
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  • 14
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 221-223
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  • 15
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 148
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  • 16
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 130-131
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  • 17
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 16
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  • 18
    Publikationsdatum: 2011-08-18
    Beschreibung: The chemiluminescent rocket ozonesonde utilizing rhodamine-B as a detector and self-pumping for air sampling has been improved. The instrument employs standard meteorological sounding systems and is the only technique available for routine nighttime ozone measurements above balloon altitudes. The chemiluminescent detector, when properly calibrated, is shown to be specific to ozone, stable, and of sufficient sensitivity for accurate measurements of ozone from about 65-20 km. An error analysis indicates that the measured ozone profiles have an absolute accuracy of about + or - 12% and a precision of about + or - 6%. Approximately 20 flights have been conducted for geophysical investigations, while additional flights were conducted with other rocket and satellite ozone soundings for comparisons. In general, these comparisons showed good agreement.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Review of Scientific Instruments; 51; Oct. 198
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  • 19
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    Publikationsdatum: 2011-08-18
    Beschreibung: The state of the art of PAN based carbon fiber manufacture and the science of fiber behavior is surveyed. A review is given of the stabilization by oxidation and the subsequent carbonization of fibers, of the apparent structure of fibers deduced from scanning electron microscopy, from X-ray scattering, and from similarities with soft carbons, and of the known relations between fiber properties and heat treatment temperature. A simplified model is invoked to explain the electrical properties of fibers and recent quantum chemical calculations on atomic clusters are used to elucidate some aspects of fiber conductivity. Some effects of intercalation and oxidative modification of finished fibers are summarized.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: American Chemical Society The 16th Natl. Symp. on Polymers in the Serv. of Man; p 125-130
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  • 20
    Publikationsdatum: 2011-08-17
    Beschreibung: A circular-scan streak tube designed for use in a laser ranging system is described. Electrostatic focusing is used between the photocathode and a microchannel plate, and electrons from the microchannel plate are proximity focused onto an output phosphor screen. Electron beam deflection is achieved by driving two orthogonal sets of deflection plate assemblies in phase quadrature at a frequency of 200 MHz. The light intensity in the output beam trace is measured by using a circular Reticon array of 720 photodiodes, which is fiber-optically coupled to the output phosphor screen of the tube. Sample measurements of frequency-doubled Nd:YAG laser-pulse waveforms are given. Also the output beamwidth has been measured at the 200-MHz deflection frequency. The results suggest a limiting resolution of 33 psec for the circular-scan streak tube used for these tests.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Oct. 15
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  • 21
    Publikationsdatum: 2011-08-17
    Beschreibung: The use of laser-induced water Raman backscatter for remote thin oil film detection and thickness measurement is reported here for the first time. A 337.1-nm nitrogen laser was used to excite the 3400-cm-1 OH stretch band of natural ocean water beneath the oil slick from an altitude of 150 m. The signal strength of the 381-nm water Raman backscatter was always observed to depress when the oil was encountered and then return to its original undepressed value after complete aircraft traversal of the floating slick. After removal of background and oil fluorescence contributions, the ratio of the depressed-to-undepressed airborne water Raman signal intensities, together with laboratory measured oil extinction coefficients, is used to calculate the oil film thickness.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Oct. 1
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  • 22
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    Publikationsdatum: 2011-08-17
    Beschreibung: Research, development, and application of atmospheric laser Doppler velocimetry are overviewed. Consideration is given to operation principles of CO2 heterodyne systems. Global wind, pollution, V/STOL flow, and true airspeed measurements are outlined. Wind energy, dust devils, water spouts, tornadoes, and aircraft wake vortices are covered.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering; 19; July-Aug
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  • 23
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    Publikationsdatum: 2011-08-17
    Beschreibung: A pulsed infrared lidar system designed for application to the remote sensing of atmospheric trace gases from an airborne platform is described. The system is also capable of measuring the infrared backscatter characteristics of the ocean surface, terrain, cloud, and aerosol targets. The lidar employed is based on dual wavelength pulse energy measurements in the 9-11 micrometer wavelength region.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering; 19; July-Aug
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  • 24
    Publikationsdatum: 2011-08-17
    Beschreibung: A simple device is described that is capable of providing real-time 3-D viewing of extended X-ray and gamma-ray objects. The visible-light images produced by the device are not merely stereoscopic, i.e., one perspective, but possess both horizontal and vertical parallax with a reasonably large field of view.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Sept. 1
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  • 25
    Publikationsdatum: 2011-08-17
    Beschreibung: Infrared grid polarizers consisting of copper lines with a 3.6-micron grid constant on a 4-micron-thick Mylar polyester substrate have been prepared by the techniques of photolithography and sputter-etching. Their polarization properties have been measured and found to be suitable for use at infrared frequencies below 700/cm. The polarizers have been used to extend the useful frequency range of a Martin-Puplett polarizing interferometer designed for Fourier transform spectroscopy. The efficiency of the interferometer has been measured over a frequency range from 50 to 700/cm and compared to that of a conventional Michelson interferometer. The results are shown to be consistent with the measured properties of the polarizers. Methods are suggested for improving the efficiency of a Martin-Puplett interferometer which employs these polarizers.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Infrared Physics; 20; July 198
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  • 26
    Publikationsdatum: 2011-08-17
    Beschreibung: A tunable diode laser spectrometer with several unique features has been developed for use in the middle IR. The all-reflective optical system has a dual-beam configuration before the dispersive mode selector to eliminate transit-angle errors at the calibration etalon. By maintaining separated beams through the mode selector, beam combiner losses are avoided. Averaging successive sweeps of the current-modulated laser permits stable reproducible spectral integrations, eliminating etalon thermal errors and producing high photometric sensitivity. Line strengths have been measured using this instrument for eleven transitions in nu4 of (C-12)H4. These include R0 and R1 and nine P-branch transitions in the 1202-1263-per cm range. Techniques for measuring strengths with a diode laser are discussed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Aug. 15
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  • 27
    Publikationsdatum: 2011-08-17
    Beschreibung: Aerosols containing solid, spherical stearic acid particles with a mean diameter of 0.8 micron and a geometric standard deviation of 1.28 were sampled with small bore front-facing aspirating probes in near-sonic and supersonic unheated free jets. The results are compared to compute the sampling error associated with a high-speed jet sample.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Air Pollution Control Association; vol. 30
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  • 28
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    Publikationsdatum: 2011-08-17
    Beschreibung: In order to relate the measured fringe shift of an interferometer to the density of a medium, the relation between density and refractive index, which is expressed by the specific refractivity, must be known. In the present paper, the specific refractivities of the wind tunnel test gases CF4 and C2F6 are determined in order to verify estimations based on the atomic refractivities of carbon and fluorine. A Twyman-Green two-beam interferometer with a 633-nm He-Ne laser light source was used to measure the specific refractivity as a function of fringe shift as the density of the gas was changed. Values of 0.122 and 0.131 cu cm/g were obtained for CF4 and C2F6 respectively at a temperature of 300 K, which are within 1% of the values computed from the atomic refractivities.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Chemical Physics; 73; July 15
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  • 29
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    Publikationsdatum: 2011-08-17
    Beschreibung: The solar power satellite concept which would make the sun's radiation available on earth as a source of energy, is discussed. Attention is given to the concept currently under evaluation in the USA, and also in Europe, though to a lesser extent. The advantages and problems associated with its adoption by the UK as a major source of electrical energy are discussed. The discussion covers topics such as sizing, reference system, and construction, costs, and problem areas.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
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  • 30
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    Publikationsdatum: 2011-08-17
    Beschreibung: A method for making aluminum-mica particle composites is presented in which mica particles are stirred in molten aluminum alloys followed by casting in permanent molds. Magnesium is added either as an alloying element or in the form of pieces to the surface of the alloy melts to disperse up to 3 wt% mica powders in the melts and to obtain high recoveries of mica in the castings. The mechanical properties of the aluminum alloy-mica composite decrease with increasing mica content; however, even at 2.2% it has a tensile strength of 14.22 kg/sq mm with 1.1% elongation, a compression strength of 42.61 kg/sq mm, and an impact strength of 0.30 kgm/sq cm. Cryogenic and self-lubricating bearing are mentioned applications.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Materials Science; 15; May 1980
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  • 31
    Publikationsdatum: 2011-08-17
    Beschreibung: The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; May 15
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  • 32
    Publikationsdatum: 2011-08-18
    Beschreibung: A technique has been developed for coating low-cost mullite-based refractory substrates with thin layers of solar cell quality silicon. The technique involves first carbonizing one surface of the ceramic and then contacting it with molten silicon. The silicon wets the carbonized surface and, under the proper thermal conditions, solidifies as a large-grained sheet. Solar cells produced from this composite silicon-on-ceramic material have exhibited total area conversion efficiencies of ten percent.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
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  • 33
    Publikationsdatum: 2011-08-18
    Beschreibung: A study has been made of the changes in the mass, thickness and flexural properties of initially wet and dry specimens of graphite/epoxy composite material due to the equivalent of eight weeks of exposure to nonionizing space environmental parameters. The parameters were near and middle solar UV irradiance, high vacuum, and temperature. The flexural properties were not affected by the exposures. Changes occurred to the mass, dimensions, and surface morphology of the specimens which varied with individual and combined parameter exposures. The combined UV and elevated thermal environment had synergistic effects on the properties of the specimens.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Composite Materials; 14; Oct. 198
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  • 34
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    Publikationsdatum: 2011-08-18
    Beschreibung: The technological development of large, horizontal-axis wind turbines (100 kW-2500 kW) is surveyed with attention to prototype projects managed by NASA. Technical feasibility has been demonstrated in utility service for systems with a rated power of up to 200 kW and a rotor diameter of 125 ft (Mod-OA). Current designs of large wind turbines such as the 2500 kW Mod-2 are projected to be cost competitive for utility applications when produced in quantity, with capital costs of 600 to 700 dollars per kW (in 1977 dollars).
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Journal of Industrial Aerodynamics; 5; May 1980
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  • 35
    Publikationsdatum: 2011-08-18
    Beschreibung: The positron lifetime technique of monitoring absorbed moisture is applied to several composites, including graphite/polymides which are candidates for high-temperature (over 260 C) applications. The experimental setup is a conventional fast-slow coincidence system wherein the positron lifetime is measured with respect to a reference time determined by the detection of a nuclear gamma ray emitted simultaneously with the positron. From the experiments, a rate of change of positron mean lifetime per unit mass of water can be determined for each type of specimen. Positron lifetime spectra are presented for a graphite/polyimide composite and for a pure polyimide.
    Schlagwort(e): COMPOSITE MATERIALS
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  • 36
    Publikationsdatum: 2011-08-18
    Beschreibung: A scaling correlator optical pattern recognition system is described in which a lensless matched spatial filter (with the second Fourier transform lens and the matched spatial filter recorded on the same plate) is used with a first Fourier transform lens that is also an holographic optical element. The matched spatial filter is recorded at one wavelength and correlation is obtained at a second wavelength. Experimental demonstration and output correlation SNR data are reported, together with a comparison of the system's noise level using conventional optics and holographic elements.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optics Communications; 34; Sept
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  • 37
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    Publikationsdatum: 2011-08-18
    Beschreibung: The value of resin/carbon fiber composites as lightweight structures for aircraft and other vehicle applications is dependent on many properties: environmental stability, strength, toughness, resistance to burning, smoke produced when burning, raw material costs, and complexity of processing. A number of woven carbon fiber and epoxy resin composites were made. The epoxy resin was commercially available tetraglycidylmethylene dianiline. In addition, composites were made using epoxy resin modified with amine and carboxyl terminated butadiene acrylonitrile copolymer. Strength and toughness in flexure as well as oxygen index flammability and NBS smoke chamber tests of the composites are reported.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: American Chemical Society The 16th Natl. Symp. on Polymers in the Serv. of Man; p 131-135
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  • 38
    Publikationsdatum: 2011-08-17
    Beschreibung: Photographic images enhanced by the method of Thiourea-S35 autoradiography are evaluated in terms of signal-to-noise ratio, detective quantum efficiency (DQE), and Wiener spectrum analysis using digitized images. It is determined that the original signal-to-noise ratio is not degraded by the intensification process which allows an increase in the practical working DQE as a function of density. These results apply at all spatial frequencies that were tested. The advantage given by autoradiography is the ability to produce usable images from emulsions originally exposed to the low densities corresponding to maximum DQE and movement of faint image densities above the level of the threshold for detection.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Astronomical Society of the Pacific; vol. 92
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  • 39
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    Publikationsdatum: 2011-08-17
    Beschreibung: The quality of image reconstructions from discrete data suffers not only from the blurring of spatial detail caused by limitations in the spatial frequency response of electrooptical systems, but also from the aliasing generated if spatial detail has been undersampled. Previous studies have observed that reasonable spot intensity profiles and photosensor aperture shapes of equivalent size result in about equal blurring but that some profiles and shapes suppress aliasing better than others. This paper presents quantitative results of the magnitude of aliasing and blurring as a function of random radiance fields typical for natural scenes and of spatial responses and sampling intervals typical for TV cameras and optical-mechanical scanners. These results indicate that aliasing may often be a larger source of degradation than either blurring or electronic noise.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; July 1
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  • 40
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    Publikationsdatum: 2011-08-17
    Beschreibung: Microscopic and electrical measurements were performed to explain the degradation mechanisms associated with the presence of titanium impurities in silicon. The measurements included X-ray topography, transmission electron microscopy, and deep level transient spectroscopy, before and after processing. The results indicated the presence of TiO2 precipitates, the density of which increased after phosphorus diffusion. A majority carrier trapping level was observed in the wafers before processing. It was concluded that 10% of the Ti in the N(+)/P silicon solar cells formed electrically active centers which caused degradation of the cell junction. 14% of the remaining Ti precipitated out as TiO2, forming electrically active defects, which also caused junction degradation.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Electrochemical Society; vol. 127
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  • 41
    Publikationsdatum: 2011-08-17
    Beschreibung: An apparatus is described in which hydrogen atoms were trapped at temperatures down to 1.1 K in the 11 T field of a large volume superconducting magnet. A high sensitivity thermal detector was used to study trapping and recombination of atoms on the detector surface. The apparatus permits the application of extremely high steady state magnetic fields to study the potential effects of electron spin polarization on the stabilization of hydrogen atoms.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Review of Scientific Instruments; 51; May 1980
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  • 42
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    Publikationsdatum: 2011-08-17
    Beschreibung: A coaxial dual-channel laser system has been developed for the measurement of extinction coefficients of highly absorbing liquids. An empty wedge-shaped sample cell is first translated laterally through a He-Ne laser beam to measure the differential thickness using interference fringes in reflection. The wedge cell is carefully filled with the oil sample and translated through the coaxially positioned dye laser beam for the differential attenuation or extinction measurement. Optional use of the instrumentation as a single-channel extinction measurement system and also as a refractometer is detailed. The system and calibration techniques were applied to the measurement of two crude oils whose extinction values were required to complete the analysis of airborne laser data gathered over four controlled spills.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Apr. 1
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  • 43
    Publikationsdatum: 2011-08-17
    Beschreibung: For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Solid-State Electronics; 23; Mar. 198
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  • 44
    Publikationsdatum: 2011-08-17
    Beschreibung: The paper covers the studies presented on nuclear science and nuclear power systems symposiums. The studies deal with nuclear radiation detectors, nuclear circuits and systems, space and medical instrumentation, as well as with environmental and reactor instrumentation. Data preprocessing and acquisition are discussed. Emphasis is placed on the engineered safety features of nuclear systems.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 45
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    Publikationsdatum: 2011-08-17
    Beschreibung: This note describes some details of recent (successful) attempts of wall proximity corrections for hot-wire measurements performed in a three-dimensional incompressible turbulent boundary layer. A simple and quite satisfactory method of estimating wall proximity effects on hot-wire readings is suggested.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: DISA Information; Feb. 198
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  • 46
    Publikationsdatum: 2011-08-18
    Beschreibung: The dielectric properties of polluted waters are measured with a reflection-type resonant cavity at 1.43 GHz. Very small water samples in quartz tubes of known volume are placed in the center of the maximum electric field. Measurement of the resonance-frequency variation and a change of the cavity's quality factor are used to determine the dielectric properties. The microwave emissivity of the polluted water is then calculated via the Fresnel equation and applied to data reductions of microwave radiometer measurements.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 47
    Publikationsdatum: 2011-08-18
    Beschreibung: The transport velocity transformation method was used to analyze solar cell designs to determine optimum cell structures. It was found that low resistivity materials should be used up to the onset of Auger recombination; a properly designed three-layer structure permits base region approaching an ideal device in performance; and that higher resistivity front regions will need more sophisticated grid metallization structures than those used now. It was concluded that new features will provide idealized silicon cell structures yielding airmass 1 efficiencies in the 24-26.5% range, with real efficiencies near 22%.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
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  • 48
    Publikationsdatum: 2011-08-18
    Beschreibung: The ultrasonic group velocity and attenuation were measured as a function of frequency for longitudinal and shear waves in the Hercules epoxy matrix (3501-6) and in the principal directions of the unidirectional Hercules graphite fiber epoxy composite (AS/3501-6). Tests were conducted in the frequency ranges 0.25-14 MHz and 0.5-3 MHz for longitudinal and shear wave modes, respectively. While the attenuation increased with frequency for all wave modes, the group velocity was independent of frequency for all wave modes. In studying the effects of transducer-specimen interface couplant and pressure, it was found that for each transducer, there exists a frequency-dependent 'saturation pressure' corresponding to the maximum output amplitude of the signal.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Nondestructive Evaluation; 1; June 198
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  • 49
    Publikationsdatum: 2011-08-18
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Solid-State Electronics; 23; Nov. 198
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  • 50
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    Publikationsdatum: 2011-08-18
    Beschreibung: Control of resistivity in NASA inorganic-organic separators is achieved by incorporating small percentages of high surface area, fine-particle silica with other ingredients in the separator coating. The volume resistivity appears to be predictable from coating composition, that is, from the surface area of filler particles in the coating. The approach has been applied to two polymer-'plasticizer'-filler coating systems, where the filler content of each is below the generally acknowledged critical pigment volume concentration of the coating. Application of these coating systems to 0.0254 cm thick (10 mil) fuel-cell grade asbestos sheet produces inexpensive, flexible, microporous separators that perform at least as well as the original inorganic-organic concept, the Astropower separator.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Electrochemical Society; vol. 127
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  • 51
    Publikationsdatum: 2011-08-17
    Beschreibung: The paper presents results of experiments in which the thermal expansion and swelling behavior of an epoxy resin system and two graphite/epoxy composite systems exposed to water were measured. It was found that the cured epoxy resin swells by an amount slightly less than the volume of the absorbed water and that the swelling efficiency of the water varies with the moisture content of the polymer. Additionally, the thermal expansion of cured epoxy resin that is saturated with water is observed to be more than twice that of dry resin. Results also indicate that cured resin that is saturated with 7.1% water at 95 C will rapidly increase in moisture content to 8.5% when placed in 1 C water. The mechanism for this phenomenon, termed reverse thermal effect, is described in terms of a slightly modified free-volume theory in conjunction with the theory of polar molecule interaction. Nearly identical behavior was observed in two graphite/epoxy composite systems, thus establishing that this behavior may be common to all cured epoxy resins.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Journal of Materials Science; 15; July 198
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  • 52
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    Publikationsdatum: 2011-08-17
    Beschreibung: Limits to low noise equivalent power (NEP) operation of a lithium niobate upconverter are investigated. Upconversion is achieved inside the optical cavity of an Ar-ion laser. Limits to NEP are imposed by limits to conversion efficiency and by noise present in the upconversion process. Conversion efficiency is limited by thermal effects in the lithium niobate. Thermally induced wedging, focusing, and aberrations are caused by the lithium niobate absorption at the 514.5-nm argon pump wavelength. The primary component of noise in the upconverter is due to upconversion of thermal radiation from the lithium niobate crystal. The lowest NEP, at a wavelength of 3.4 microns, achieved in this study was 8.9 x 10 to the -14th W/(Hz to the 1/2 power).
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 53
    Publikationsdatum: 2011-08-18
    Beschreibung: Two prototype solid-state phased array systems concepts for potential use in the Solar Power Satellite are described. In both concepts, the beam is centered on the rectenna by means of phase conjugation of a pilot signal emanating from the ground. Also discussed is on-going solid-state amplifier development.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 279-298
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  • 54
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    Publikationsdatum: 2011-08-18
    Beschreibung: Solid state dc-rf converters offer potential improvements in reliability, mass and low voltage operation, provided that anticipated efficiencies in excess of 80 percent can be realized. Field effect transistors offer the greatest potential in the SPS frequency band at 2.45 GHz. To implement this approach it is essential that means be found to sum the power of many relatively low power solid state sources in a low-loss manner, and that means be provided to properly control the phase of the outputs of the large number of solid state sources required. To avoid the power combining losses associated with circuit hybrids it was proposed that the power from multiple solid state amplifiers be combined by direct coupling of each amplifier's output to the radiating antenna structure. The selected power-combining antenna consists of a unique printed (metalized) microstrip circuit on a ceramic type dielectric substrate which is backed by a shallow lightweight aluminum cavity which sums the power of four microwave sources. The antenna behaves like two one-half wavelength slot-line antennas coupled together via their common cavity structure.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 268-277
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  • 55
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    Publikationsdatum: 2011-08-18
    Beschreibung: The possibilities of using solid state devices as part of the Satellite Solar Power System are discussed. Solid state advantages and disadvantages are presented along with two potential concepts for use of solid state in the system design.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Workshop on Microwave Power Transmission and Reception; p 253-257
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  • 56
    Publikationsdatum: 2011-08-18
    Beschreibung: A method for the precision-forming of thin-walled, slotted-waveguide arrays was devised. Models were constructed with temporary tools and evaluated. The application of the method to the SPS requirements is discussed.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 188-190
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  • 57
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    Publikationsdatum: 2011-08-18
    Beschreibung: The SPS transmitting array requires an architecture which will provide a low weight, high efficiency and high structural rigidity. As noted above, waveguide slot arrays constitute the most desirable option. Consequently, such an array has been chosen for the SPS. Waveguide slot arrays offer high efficiency, uniform illumination, are are fairly lighweight. Bandwidths of such arrays are narrow, typically 1/2-2%. Although this does not directly impact the SPS, which transmits power at a single frequency of 2.45 GHz, the narrow bandwidth does constrain the thermal and mechanical tolerances of the antenna. The purpose of this program is to better define the electronic aspects of an SPS specific waveguide slot array. The specific aims of the program are as follows: (1) To build a full-scale half-module, 10 stick, array, the design parameters for which are to be determined by analytical considerations tempered by experimental data on a single slotted radiating stick, (2) To experimentally evaluate the completed array with respect to antenna pattern, impedance and return loss, and (3) To measure swept transmission amplitude and phase to provide a data base for design of a receiving antenna.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 180-187
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  • 58
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: The SPS transmitting array requires an architecture which will provide a low weight, high efficiency and high structural rigidity. Waveguide slot arrays constitute the most desirable option. Consequently, such an array was chosen for the SPS. Waveguide slot arrays offer high efficiency, uniform illumination, and are fairly lightweight. Bandwidths of such arrays are narrow, typically 1/2-2%. Although this does not directly impact the SPS, which transmits power at a single frequency of 2.45 GHz, the narrow bandwidth does constrain the thermal and mechanical tolerances of the antenna. The purpose of this program is to better define the electronic aspects of an SPS specific waveguide slot array. The specific aims of the program are as follows: (1) To build a full-scale half-module, 10 stick, array, the design parameters for which are to be determined analytical considerations tempered by experimental data on a single slotted radiating stick, (2) To experimentally evaluate the completed array with respect to antenna pattern, impedance and return loss; and (3) To measure swept transmission amplitude and phase to provide a data base for design of a receiving antenna.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception 158-165 (SEE N82-12538 03-44)
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  • 59
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    Publikationsdatum: 2011-08-18
    Beschreibung: The fundamental theory of MW antenna operation and basic array technology development status was used in the design of the 1-km diameter 5-Gw SPS microwave antenna. However, the aperture size and the high efficiency requirements make the MW antenna extremely complex. Studies show that the slotted waveguide array is one of the most efficient radiators for the antenna. Subsequent analyses show that the temperature interface between waveguides and dc-RF conversion tubes can cause severe thermal design problems on the array. An alternate design, the Resonant Cavity Radiator, is described here.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 167-177
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  • 60
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2012-05-18
    Beschreibung: Flight experience gained with numerous composite aircraft structures is discussed. Both commercial transports and helicopters are included. Design concepts with significant mass savings and appropriate inspection and maintenance procedures are among the factors considered. Also, a major NASA/U.S. industry technology program to reduce fuel consumption of commercial transport aircraft through the use of advanced composites is described, including preliminary results. Ground and flight environmental effects on the composite materials used in the flight service programs are also discussed.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AGARD Effect of Serv. Environ. on Composite Mater.; 22 p
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  • 61
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    Publikationsdatum: 2011-08-17
    Beschreibung: Four types of sensors were used to make both dynamic and time-averaged flow measurements in a cold turbine rig to determine the magnitude of errors in time-averaged total-pressure measurement at a station 5 1/2 blade cords downstream from the rotor. The errors turned out to be negligible. The sensors and their intended use are discussed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 62
    Publikationsdatum: 2011-08-17
    Beschreibung: New techniques in nonlinear optical processing are explored, based on the operation of intensity level selection as performed by a Fabry-Perot interferometer containing a phase object. The image being processed is recorded on a medium between the mirrors as a spatially varying phase shift less than pi. The interferometer only transmits light through those portions of the object that corresponds to a single value of the phase and hence to a single intensity level in the input. More complicated operations such as thresholding and analog-to-digital conversion are performed by modulating the light source as the different levels are selected. Photoresist and lithium niobate have been used as phase objects, and experimental data for both are presented. Three kinds of Fabry-Perot interferometers have been used to demonstrate nonlinear processing using coherent and incoherent light. Color images have been produced with black and white inputs and white light illumination.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 63
    Publikationsdatum: 2011-08-17
    Beschreibung: High open circuit voltage cell designs based on 0.1 Ohm cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power per sq cm. Of the three cell designs, radiation induced degradation was greatest in the high low emitter (HLE) cell. The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short circuit current and open circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: ESA Photovoltaic Generators in Space; p 129-134
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  • 64
    Publikationsdatum: 2011-08-17
    Beschreibung: Cells 2 cm x 2 cm were produced having an efficiency of 16% at 100 C and 12% at 200 C. They were superior to silicon cells under 1 MeV electron bombardment up to fluences in excess of 10 to the 15th power electron per sq cm, and to protons with an energy in excess of 1 MeV. The possibility of producing cells in quantity using a graphite wafer holder is mentioned.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: ESA Photovoltaic Generators in Space; p 121-126
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  • 65
    Publikationsdatum: 2011-08-17
    Beschreibung: The digital recording acquisition subsystem (DRAS) is a wideband digital recording system that can accommodate data sample rates from 0.125 to 8 MHz in binary increments. The implementation of the DRAS for radio interferometry applications in support of the Crustal Dynamics Project is described. The functional and performance characteristics of the equipment and the key aspects of the implementation plan are discussed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: The Telecommun. and Data Acquisition Rept.; p 9-14
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  • 66
    Publikationsdatum: 2011-08-18
    Beschreibung: A laser beam manifold and particle photography system has been developed for use in fluid velocity measurements. The laser manifold is a device which transforms a single laser beam into several uniform parallel beams. By orienting two manifolds mutually perpendicular, an optical grid can be formed which acts as a reference for fluid velocity measurements. This optical grid is for all practical purposes totally nonperturbing to the flow. Tracer particles moving in the plane of the grid are then photographed to yield fluid velocities that can be measured relative to the optical grid. System construction and theory are presented.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Review of Scientific Instruments; 51; Nov. 198
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  • 67
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    Publikationsdatum: 2011-08-18
    Beschreibung: This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and digitally controlled current sources are implemented with redundant designs to avoid a loss of data in case of failures. Measurements are carried out with an accuracy of + or - 1 part in 64,000 in magnitude and 5 arcsec in orientation (1 arcsec = 0.00028 deg).
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Johns Hopkins APL Technical Digest; 1; July-Sep
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  • 68
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Magsat scalar magnetometer is derived from optical pumping magnetometers flown on the orbiting geophysical observatories. The basic sensor, a cross-coupled arrangement of absorption cells, photodiodes, and amplifiers, oscillates at the Larmor frequency of atomic moments precessing about the ambient field direction. The Larmor frequency output is accumulated digitally and stored for transfer to the spacecraft telemetry stream. In orbit the instrument has met its principal objective of calibrating the vector magnetometer and providing scalar field data.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Johns Hopkins APL Technical Digest; 1; July-Sep
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  • 69
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: The performance of solar energy devices is adversely affected by surface soiling, and generally, the loss of performance increases with increases in the quantity of soil retained on their surfaces. To minimize performance losses caused by soiling, solar devices should not only be deployed in low soiling geographical areas, but employ surfaces or surfacing materials having low affinity for soil retention, maximum susceptibility to be naturally cleaned by wind, rain and snow, and to be readily cleanable by simple and inexpensive maintenance cleaning techniques. This article describes known and postulated mechanisms of soil retention on surfaces, and infers from these mechanisms that low soiling and easily cleanable surfaces should have low surface energy, and be hard, smooth, hydrophobic and chemically clean of sticky materials and water soluble salts.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
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  • 70
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simple and direct method is obtained for assessing the distortion of a Doppler line by a Gaussian instrument function. It is suggested that a close approximation to the width of a Gaussian instrument function, or an almost Gaussian function, may be obtained by measuring a line with a Doppler absorption coefficient. The method is applicable to diode laser measurements, and may be used whenever a Gaussian instrument function is a reasonable approximation to real conditions
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Molecular Spectroscopy; 81; 1980
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  • 71
    Publikationsdatum: 2011-08-18
    Beschreibung: Developed to give a quick and accurate predictions HISPER, a simplification of the TRNSYS program, achieves its computational speed by not simulating detailed system operations or performing detailed load computations. In order to validate the HISPER computer for air systems the simulation was compared to the actual performance of an operational test site. Solar insolation, ambient temperature, water usage rate, and water main temperatures from the data tapes for an office building in Huntsville, Alabama were used as input. The HISPER program was found to predict the heating loads and solar fraction of the loads with errors of less than ten percent. Good correlation was found on both a seasonal basis and a monthly basis. Several parameters (such as infiltration rate and the outside ambient temperature above which heating is not required) were found to require careful selection for accurate simulation.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 23 p
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  • 72
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    Publikationsdatum: 2011-08-17
    Beschreibung: The astrometric application of the Wide Field Camera and the Planetary Camera is reviewed. It is shown that the digital image centering algorithms can yield a positional accuracy of 0.1 milli-arcsecond. Deconvolution of CCD's sensitivity, non-flatness of the filters, and crinkling of the CCD surface may limit the positional accuracy of 1 milli-arcsecond.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 73
    Publikationsdatum: 2011-08-17
    Beschreibung: New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for the BCL Process, which produces the solar-cell silicon by reduction of silicon tetrachloride with zinc vapor. Cost, sensitivity, and profitability analysis results are presented based on a preliminary process design of a plant to produce 1000 metric tons/year of silicon by the BCL Process. Profitability analysis indicates a sales price of $12.1-19.4 per kg of silicon (1980 dollars) at a 0-25 per cent DCF rate of return on investment after taxes. These results indicate good potential for meeting the goal of providing lower cost material for silicon solar cells.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Solar Energy; 24; 4, 19; 1980
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  • 74
    Publikationsdatum: 2011-08-17
    Beschreibung: The thermal response of the fused silica dome filter in an earth radiation budget WFOV shortwave channel conceptual design and the impact of that response on the channel measurement, is described. Attention is given to results from design definition and performance analysis studies. Consideration is given to problems associated with achieving the desired levels of confidence in a high accuracy filtered earth radiation budget WFOV radiometer. Finally, design approaches, ground calibration, and data reduction techniques that minimize measurement uncertainties are covered.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; June 1
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  • 75
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    Publikationsdatum: 2011-08-17
    Beschreibung: The paper discusses the Thematic Mapper (TM), a multispectral earth resources sensor that will be launched on the Landsat-D satellite. The TM will operate in a circular, near-polar orbit of 750-km altitude and will scan a swath of earth 185 km wide. One TM mirror is a moving scan mirror, active during the forward and reverse scans; the final design of this component incorporates a mirror which has the required linearity and is not influenced by structural vibration. Another TM component that presented a design difficulty was the optical metering structure which has to be thermally stable across the temperature range in the instrument's orbital environment and duty cycle.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: IEEE Transactions on Geoscience and Remote Sensing; GE-18; Apr. 198
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  • 76
    Publikationsdatum: 2011-08-17
    Beschreibung: A new method of ultrasonic frequency analysis is introduced which employs frequency-tracked gated RF drive pulses rather than shock-excited broadband spikes to generate the ultrasonic waveform. The new technique, a variation of the sampled-continuous wave technique, eliminates problems associated with finite pulse widths of conventional methods. It is shown to yield correct ultrasonic wave velocity measurements of the sample irrespective of receiver gate width or position provided any portions of two successive echoes are gated simultaneously into the spectrum analyzer. The experimental observations are substantiated by a theoretical model based on the time-frequency domain formulation of ultrasonic frequency analysis.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Acoustical Society of America; vol. 67
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  • 77
    Publikationsdatum: 2011-08-17
    Beschreibung: The contribution of the resin matrix to the performance of the composite is studied with particular emphasis on the flammability, and thermal and mechanical properties. Of the several thermoset and thermoplastic matrices examined, the lowest fire-resistant properties of the composite have been observed with epoxy matrices. Bismaleimide A composites exhibit high fire-resistant properties, low moisture absorption, and good mechanical properties at 23 C. Bismaleimide B and phenolic retain their mechanical properties at elevated temperatures but have lower mechanical properties than the epoxy composites at ambient temperatures. Phenolic-novolac, polyethersulfone, and polyphenylsulfone composites exhibit high oxygen index and low smoke evolution.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Plastics Design and Processing; Jan. 198
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  • 78
    Publikationsdatum: 2011-08-17
    Beschreibung: The paper presents the water depth measurement using an airborne pulsed neon laser system. The results of initial base-line field test results of NASA airborne oceanographic lidar in the bathymetry mode are given, with water-truth measurements of depth and beam attenuation coefficients by boat taken at the same time as overflights to aid in determining the system's operational performance. The nadir-angle tests and field-of-view data are presented; this laser bathymetry system is an improvement over prior models in that (1) the surface-to-bottom pulse waveform is digitally recorded on magnetic tape, and (2) wide-swath mapping data may be routinely acquired using a 30 deg full-angle conical scanner.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 19; Mar. 15
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  • 79
    facet.materialart.
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    Publikationsdatum: 2011-08-18
    Beschreibung: The motivations for considering solid state microwave power amplifiers for the solar power satellite transmitting antenna are the possibilities of greatly increased system reliability due to elimination of electron tube cathodes, a lower mass per unit power and transmitting array area due to the high power densities obtainable in semiconductors, and, probably, cost savings due to development of small hardware items that can be handled by individuals instead of organizations. In order to provide a fair assessment where we stand today with regard to solid state SPS technology, the design described here is close to that of the NASA/DOE reference and is implemented using today's solid state technology with only a small "push". The small push is raising the efficiency of DC-RF conversion from the .68 obtained by RCA in 1975 to somewhat over .8 of the solid state SPS. This is generally considered feasible by semiconductor industry representatives. Other solid state SPS configurations can yield somewhat better performance. However, these generally do not provide as fair a vehicle for comparison with the reference and usually also incorporate somewhat more advanced technologies.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 258-267
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  • 80
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    Publikationsdatum: 2011-08-18
    Beschreibung: The measured performance characteristics of a rectenna array are reviewed and compared to the performance of a single element. It is shown that the performance may be extrapolated from the individual element to that of the collection of elements. Techniques for current and voltage combining were demonstrated. The array performance as a function of various operating parameters is characterized and techniques for overvoltage protection and automatic fault clearing in the array demonstrated. A method for detecting failed elements also exists. Instrumentation for deriving performance effectiveness is described. Measured harmonic radiation patterns and fundamental frequency scattered patterns for a low level illumination rectenna array are presented.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 244-250
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  • 81
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Two micro aspects of rectenna design are discussed: evaluation of the degradation in net rectenna RF to DC conversion efficiency due to power density variations across the rectenna (power combining analysis) and design of Yagi-Uda receiving elements to reduce rectenna cost by decreasing the number of conversion circuits (directional receiving elements). The first of these involves resolving a fundamental question of efficiency potential with a rectenna, while the second involves a design modification with a large potential cost saving.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 223-231
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  • 82
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    Publikationsdatum: 2011-08-18
    Beschreibung: The history of the development of the rectenna is first reviewed through its early conceptual and developmental phases in which the Air Force and Raytheon Company were primarily involved. The intermediate period of development which involved NASA, Jet Propulsion Laboratory, and Raytheon is then reviewed. Some selective aspects of the current SPS rectenna development are examined.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 203-212
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  • 83
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    Publikationsdatum: 2011-08-18
    Beschreibung: Progress in adapting the crossed-field directional amplifier to the SPS is reviewed. Special emphasis is given to (1) recent developments in controlling the phase and amplitude of the microwave power output, (2) a received architecture for its placement in the subarray, and (3) recent developments in the critical pivotal areas of noise, potential cathode life, and efficiency.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 147-155
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  • 84
    Publikationsdatum: 2011-08-18
    Beschreibung: Due to complexity of the program which used a hydrodynamic, axially and radially deformable disk-ring model and the resulting long computing time only the output gap was investigated. Results from independent studies were used to initiate the starting conditions for the electrons and the RF voltage using our program. Although this method of computation is less exact than processing the entire klystron interaction in 3-Dimensions it is shown that, for a confined flow focused throughout the penultimate cavity, radial velocities remain very small and the beam is highly laminar. It is concluded that possible errors resulting from treating only the output cavity in 3-D would remain small.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 139-146
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  • 85
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    Publikationsdatum: 2011-08-18
    Beschreibung: The most likely compact configuration to realize both high efficiency and high gain is a 5-6 cavity design focused by an electromagnet. An outline of a potential klystron configuration is given. The selected power output of 70 kW CW resulted from a maximum assumed operating voltage of 40 kV. The basic klystron efficiency cannot be expected to exceed 70-75% without collector depression. Although impressive gains were achieved in raising the basic efficiency from 50% to 70% or so with a multi-stage collector, the estimated efficiency improvement due to 5-stage collector at the 75% level is only about 8% resulting in an overall efficiency of about 83%.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 127-136
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  • 86
    Publikationsdatum: 2011-08-18
    Beschreibung: The operation of an active retrodirective array (ARA) in an ionospheric environment (that is either stationary or slowly-varying) was examined. The restrictions imposed on the pilot-signal structure as a result of such operation are analyzed. A 3-tone pilot beam system is defined which first estimates the total electron content along paths of interest and then utilizes this information to aid the phase conjugator so that correct beam pointing can be achieved.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 115-125
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  • 87
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simulator which generates and transmits a beam of audible sound energy mathematically similar to the SPS power beam is described. The simulator provides a laboratory means for analysis of ground based closed loop SPS phase control and of ionospheric effects on the SPS microwave power beam.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 97-99
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  • 88
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: To properly point and form the SPS microwave power beam, the outputs of the power amplifiers in the transmitting array must be phased in a specific and coherent fashion. The purpose of the SPB phase control system is to bring this about reliably. A number of different phase control schemes were studied. The one selected for the SPS baseline system is a retrodirective CW phase that is distributed via fiber optics. The basis of this selection is relative technical simplicity and requisite assurance of success.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 100-109
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  • 89
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    Publikationsdatum: 2011-08-18
    Beschreibung: A system for focusing and pointing the SPS power beam is discussed. The system is ground based and closed loop. One receiving antenna is required on Earth. A conventional uplink data channel transmits an 8-bit phase error correlation back to the SPS for sequential calibration of each power module. Beam pointing resolution is better than 140 meters at the Rectenna.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 95-98
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  • 90
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    Publikationsdatum: 2011-08-18
    Beschreibung: Fiber optic technology was selected in the SPS baseline design to transmit a stable phase reference throughout the microwave array. Over a hundred thousand microwave modules are electronically steered by the phase reference signal to form the power beam at the ground receiving station. The initially selected IF distribution frequency of the phase reference signal was set at 980 MHz or a submultiple of it. Fiber optics offers some significant advantages in view of the SPS application. Optical transmission is highly immume to EMI/RFI, which is expected to be severe when considering the low distribution power. In addition, there will be savings in both mass, physical size, and potentially in cost.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 110-114
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  • 91
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    Publikationsdatum: 2011-08-18
    Beschreibung: A power density level of 23 mW/sq cm is presented as a design specification based on theoretical calculations of a threshold for microwave ionosphere nonlinear interaction (thermal runaway). For comparable power densities, enhanced electron heating is observed to change the electron temperature by a factor of two or three, but not by an order of magnitude.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 32-43
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  • 92
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    Publikationsdatum: 2011-08-18
    Beschreibung: The computer programming efforts were directed primarily to beam pattern analysis. The computer programs used for simulation provide: verification of the reference design; definition of feasible departures such as quantized distributions; the study of far-out sidelobe roll-off characteristics; the analysis of errors and failures; illumination function analysis to develop beam patterns for efficient collection; and beam shaping synthesis to meet environmental constraints.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 14-23
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  • 93
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    Publikationsdatum: 2011-08-18
    Beschreibung: In order to maximize the efficiency of the microwave power transmission system (MPTS), the surface of the array antenna must be extremely flat, which is difficult to achieve using passive techniques over the 1 km dimensions of the array. In order to achieve and maintain this required flatness, a rotating laser beam used for leveling applications on Earth was utilized as a reference system. A photoconductive sensor with a reflective collecting surface was used to determine the displacement and polarity of any misalignment and automatically engage a stepping motor to drive a variable-length mechanism to make the necessary corrections. Once aligned, little power is dissipated since a nulling bridge circuit that centers on the beam is used, an important alignment feature since even laser beams broaden considerably at 1 km distances.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Workshop on Microwave Power Transmission and Reception; p 26-31
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  • 94
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    Publikationsdatum: 2011-08-18
    Beschreibung: System sizing is discussed in terms of reduced power levels and antenna diameters smaller than 1 km. The microwave transmission efficiency for smaller SPS systems was investigated. Startup and shutdown operations were examined with emphasis on solar eclipse effects on the solar arrays. The antennas and subarray mechanical alignments are also discussed.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Workshop on Microwave Power Transmission and Reception; p 1-12
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  • 95
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2017-10-02
    Beschreibung: The feasibility of using solid state elements in the solar power satellite transmitter system is addressed. Recommendations are given concerning device types, the antenna modules, and the overall antenna system. The development of a solid state amplifier based on GaAs field effect transistor devices is also described.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Johnson Space Center Solar Power Satellite Microwave Transmission and Reception; p 358-366
    Format: application/pdf
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  • 96
    Publikationsdatum: 2017-10-02
    Beschreibung: Carbon composite materials are finding limited use in both civil and military aircraft structures to exploit their weight saving potential for improved performance or fuel efficiency. Since these needs are growing, and a manufacturing cost savings potential is also recognized, wider use of composites in the near future may be expected. Carbon composites generally involve fiber volume fractions in excess of 60 percent in a variety of orthotropic sandwich or solid laminates. Bidirectional woven carbon cloth, common in recently designed structure, may provide higher, more uniform laminate conductivities than tape.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AGARD Electromagnetic Effects of (Carbon) Composite Mater. Upon Avionics Systems; 19 p
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  • 97
    Publikationsdatum: 2017-10-02
    Beschreibung: Carbon and graphite fibers are known to be electrically conductive. The rapidly accelerating use of carbon fibers as the reinforcement in filamentary composite materials brought up the possibility of accidental release of carbon fibers from the burning of crashed commercial airliners with carbon composite parts. Such release could conceivably cause widespread damage to electrical and electronic equipment. The experimental and analytical results of a comprehensive investigation of the various elements necessary to assess the extent of such potential damage in terms of annual expected costs and maximum losses at low probabilities of occurrence are presented. A review of NASA materials research program to provide alternate or modified composite materials to overcome any electrical hazards from the use of carbon composites in aircraft structures is described.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AGARD Effect of Serv. Environ. on Composite Mater.; 21 p
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  • 98
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2017-10-02
    Beschreibung: A model for describing the response of uncoated and coated fiber reinforced composites subjected to repeated impingements of liquid (rain) droplets is presented. The model is based on the concept that fatigue is the dominant factor in the erosion process. Algebraic expressions are provided which give the incubation period, the rate of mass loss past the incubation period, and the total mass loss of the material during rain impact. The influence of material properties on erosion damage and the protection offered by different coatings are discussed and the use of the model in the design in the design of structures and components is illustrated.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AGARD Effect of Serv. Environ. on Composite Mater.; 9 p
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  • 99
    Publikationsdatum: 2017-10-02
    Beschreibung: The effects of low velocity impact on the compressive strength of graphite/epoxy structures are reviewed. Extensive tests were conducted on sandwich beams, laminated plates and stiffened panels. Conditions for failures were investigated by impact tests on statically loaded test specimens. Lightly loaded graphite structures (such as aircraft secondary structure) were insensitive to impact damage. In more heavily loaded structures, (such as wing panels), appreciable reductions in compressive strength occurred. The implications of the tests for structural design are discussed by comparing panel masses for designs where ultimate strains were reduced due to impact considerations with the masses of designs with higher ultimate strains. Preliminary test data are presented to show the possibility of improvements in damage to tolerance achievable by using an alternate matrix material.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: AGARD Effect of Serv. Environ. on Composite Mater.; 13 p
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  • 100
    facet.materialart.
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    In:  CASI
    Publikationsdatum: 2017-10-02
    Beschreibung: Charge control studies on nickel hydrogen cells are discussed. Characterization test data for the cells are presented in graphical form. The test areas covered were capacity versus temperature, ampere-hour cycling efficiency, and the charge method which involved voltage level with current limiting.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: NASA. Goddard Space Flight Center The 1979 Goddard Space Flight Center Battery Workshop; p 525-531
    Format: application/pdf
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