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  • METEOROLOGY AND CLIMATOLOGY  (63)
  • COMPOSITE MATERIALS  (45)
  • 1980-1984  (108)
  • 1980  (108)
  • 1
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    Eddy diffusion coefficients and the variance of the atmosphere 30-60 km (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The results of numerical models or of new observational programs are checked by comparing them with past observations. In view of the differing analysis techniques or differing data samples, the eddy diffusivities presented here agree remarkably well with past estimates. However, in the application of K-values to two-dimensional models, the actual magnitude of the diffusivities is no more important than their spatial patterns, i.e., their gradients with height and latitude. It should thus be noted that the present patterns are often much different from those of past results.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Pure and Applied Geophysics; 118; 5, 19; 1980
    Format: text
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  • 2
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    Thermal expansion of composites using Moire interferometry (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental technique for precise measurement of the thermal response of fiber-reinforced composite materials uses moire interferometry with fringe multiplication which yield a sensitivity of 833 nm (32.8 mu in.) per fringe. Results from the technique are compared with those obtained from electrical resistance strain gages, and also those predicted from classical lamination theory. Temperature dependent coefficients of thermal expansion for composite materials subjected to thermal cycling in the temperature range of 297 K (75 F) to 422 K (300 F) were determined for four laminate configurations (0, 90, 0/ + or - 45/90 sub s and 0/90/ + or - 45 sub s) of T300/5208 graphite epoxy, and ranged from -0.107 mu epsilon K/1 (-0.059 mu epsilon deg F/-) for the 0 laminate to 32.18 mu epsilon K/1 (17.88 mu epsilon F/1) for the 90 laminate. Moisture was found to greatly influence the thermal response of a quasi-isotropic laminate, resulting in hysteresis and residual compressive strain as the moisture content was reduced. Comparisons between moire and strain gage measurements were inconclusive with both techniques giving consistent but systematically different results. Differences of as much as 29% were observed.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-80788 , VPI-E-80-19 , IR-20
    Format: application/pdf
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  • 3
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    Determination of the complex refractive index and size distribution of atmospheric particulates from bistatic-monostatic lidar and solar radiometer measurements (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A method is presented for inferring both the size distribution and the complex refractive index of atmospheric particulates from combined bistatic-monostatic lidar and solar radiometer observations. The basic input measurements are spectral optical depths at several visible and near-infrared wavelengths as obtained with a solar radiometer and backscatter and angular scatter coefficients as obtained from a biostatic-monostatic lidar. The spectral optical depth measurements obtained from the radiometer are mathematically inverted to infer a columnar particulate size distribution. Advantage is taken of the fact that the shape of the size distribution obtained by inverting the particulate optical depth is relatively insensitive to the particle refractive index assumed in the inversion. Bistatic-monostatic angular scatter and backscatter lidar data are then processed to extract an optimum value for the particle refractive index subject to the constraint that the shape of the particulate size distribution be the same as that inferred from the solar radiometer data. Specifically, the scattering parameters obtained from the bistatic-monostatic lidar data are compared with corresponding theoretical computations made for various assumed refractive index values. That value which yields best agreement, in a weighted least squares sense, is selected as the optimal refractive index estimate. The results of this procedure applied to a set of simulated measurements as well as to measurements collected on two separate days are presented and discussed.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research; 85; Mar. 20
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  • 4
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    Estimating probabilities of cloud-free fields-of-view from the earth through the atmosphere (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper is an extension of previous papers by Lund and Shanklin (1972, 1973). It presents probabilities of cloud-free fields-of-view (CFFOV) to supplement probabilities of cloud-free lines-of-sight (CFLOS) contained in the earlier papers. A model is developed for estimating the probability of obtaining a CFFOV as a function of ground-observer-reported total sky cover for earth-to-space applications. The development of the model and examples of its application are described. A comparison of CFFOV and CFLOS results is made. In conclusion, climatic probabilities of CFFOV overhead through the entire atmosphere between the surface of the earth and space can be estimated for any desired geographical location through the use of a specified equation and conditional probabilities contained in the paper, if the frequency distribution of total sky cover categories for the desired location is known.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: AD-A086320 , AFGL-TR-80-0183 , Journal of Applied Meteorology; 19; Apr. 198
    Format: text
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  • 5
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    Coatings for graphite fibers (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-159304 , R80-914212-22
    Format: application/pdf
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  • 6
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    Effects of moisture, residual thermal curing stresses and mechanical load on the damage development in quasi-isotropic laminates (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Classical laminate theory and a finite element model were used to predict stress states prior to the first formation of damage in laminates fabricated from T/300/5208. Crack patterns characteristic of the laminate in a wet or dry condition were also predicted using a shear lag model. Development of edge damage was recorded and observed during the test by transferring an image of the damage from the edge surface on to a thin acetate sheet such that the damage imprinted could be immediately viewed on a microfiche card reader. Moisture was shown to significantly alter the interior and edge dry stress states due to swelling and a reduction of elastic properties and to reduce the transverse strength in 90 deg plies. A model was developed in order to predict changes in first ply failure laminate loads due to differences in stacking sequence together with a wet or dry environmental condition.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-162921 , VPI-E-80-5 , IR-16
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  • 7
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    An assessment of the risk arising from electrical effects associated with carbon fibers released from commercial aircraft fires (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The risks associated with electrical effects arising from carbon fibers released from commercial aviation aircraft fires were estimated for 1993. The expected annual losses were estimated to be about $470 (1977 dollars) in 1993. The chances of total losses from electrical effects exceeding $100,000 (1977 dollars) in 1993 were established to be about one in ten thousand.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-159205 , C-81857
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  • 8
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    Deep convection on day 261 of GATE (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The structural features of the deep convection observed on September 18, 1974, day 261 of the GARP Atlantic Tropical Experiment (GATE), as the ridge axis of a 700 mb wave passed the center of the GATE B-scale network are reported. Satellite and aircraft maps indicate the presence of clouds penetrating above 2.5 km into the middle troposphere organized in bands about 9 km apart and aligned roughly along the direction of the wind shear in the cloud layer. Radar echoes corresponding to cumulus convection of lifetime, peak height and peak rainfall rates on the orders of 30 min, 6 km and 1.3 mm/h, respectively, were observed to triple in number density as convergence at 950 hPa increased from 1.5 to 3 x 10 to the -5th/sec. The structural features of the radar echoes indicate that the day was similar to a mesoscale precipitation feature of Leary and Houe (1979), with the cluster consisting of many echoes appearing in succession. Data from aircraft penetrations of the deep convection reveal downdrafts accompanying the precipitation and updrafts immediately to their south. Shipboard and rawinsonde observations show that the convective downdrafts brought down air of low pseudo-equivalent potential temperature, with local surface convergence of up to 0.001/sec. Mean wind shears through the cloud layer to the top of a main cloud layer are found to be only 75% greater than those of Malkus (1958) for the Caribbean, with shears just above the cloud base several factors larger.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review; 108; Feb. 198
    Format: text
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  • 9
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    Statistical aspects of carbon fiber risk assessment modeling (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The probabilistic and statistical aspects of the carbon fiber risk assessment modeling of fire accidents involving commercial aircraft are examined. Three major sources of uncertainty in the modeling effort are identified. These are: (1) imprecise knowledge in establishing the model; (2) parameter estimation; and (3)Monte Carlo sampling error. All three sources of uncertainty are treated and statistical procedures are utilized and/or developed to control them wherever possible.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-159318
    Format: application/pdf
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  • 10
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    A proposed method for wind velocity measurement from space (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An investigation was made of the feasibility of making wind velocity measurements from space by monitoring the apparent change in the refractive index of the atmosphere induced by motion of the air. The physical principle is the same as that resulting in the phase changes measured in the Fizeau experiment. It is proposed that this phase change could be measured using a three cornered arrangement of satellite borne source and reflectors, around which two laser beams propagate in opposite directions. It is shown that even though the velocity of the satellites is much larger than the wind velocity, factors such as change in satellite position and Doppler shifts can be taken into account in a reasonable manner and the Fizeau phase measured. This phase measurement yields an average wind velocity along the ray path through the atmosphere. The method requires neither high accuracy for satellite position or velocity, nor precise knowledge of the refractive index or its gradient in the atmosphere. However, the method intrinsically yields wind velocity integrated along the ray path; hence to obtain higher spatial resolution, inversion techniques are required.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-TM-82053 , USNC/URSI Radio Sci. Meeting; Jan 12, 1981 - Jan 15, 1981; Boulder, CO; United States
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