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  • Other Sources  (75)
  • 2020-2022  (2)
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  • 1985-1989  (8)
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  • 1
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    Optimized reconstruction of the crystallographic orientation density function based on a reduced set of orientations (2021)
    Details
    Publication Date: 2021-10-12
    Description: Crystallographic textures, as they develop for example during cold forming, can have a significant influence on the mechanical properties of metals, such as plastic anisotropy. Textures are typically characterized by a non-uniform distribution of crystallographic orientations that can be measured by diffraction experiments like electron backscatter diffraction (EBSD). Such experimental data usually contain a large number of data points, which must be significantly reduced to be used for numerical modeling. However, the challenge in such data reduction is to preserve the important characteristics of the experimental data, while reducing the volume and preserving the computational efficiency of the numerical model. For example, in micromechanical modeling, representative volume elements (RVEs) of the real microstructure are generated and the mechanical properties of these RVEs are studied by the crystal plasticity finite element method. In this work, a new method is developed for extracting a reduced set of orientations from EBSD data containing a large number of orientations. This approach is based on the established integer approximation method and it minimizes its shortcomings. Furthermore, the L1 norm is applied as an error function; this is commonly used in texture analysis for quantitative assessment of the degree of approximation and can be used to control the convergence behavior. The method is tested on four experimental data sets to demonstrate its capabilities. This new method for the purposeful reduction of a set of orientations into equally weighted orientations is not only suitable for numerical simulation but also shows improvement in results in comparison with other available methods.
    Keywords: 548 ; texture reconstruction ; integer approximation ; crystal plasticity ; micromechanical modeling
    Language: English
    Type: map
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    CITATION GEO-LEO
  • 2
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    IONS (ANURADHA): Ionization states of low energy cosmic rays (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: IONS (ANURADHA), the experimental payload designed specifically to determine the ionization states, flux, composition, energy spectra and arrival directions of low energy (10 to 100 MeV/amu) anomalous cosmic ray ions of helium to iron in near-Earth space, had a highly successful flight and operation Spacelab-3 mission. The experiment combines the accuracy of a highly sensitive CR-39 nuclear track detector with active components included in the payload to achieve the experimental objectives. Post-flight analysis of detector calibration pieces placed within the payload indicated no measurable changes in detector response due to its exposure in spacelab environment. Nuclear tracks produced by alpha-particles, oxygen group and Fe ions in low energy anomalous cosmic rays were identified. It is calculated that the main detector has recorded high quality events of about 10,000 alpha-particles and similar number of oxygen group and heavier ions of low energy cosmic rays.
    Keywords: GEOPHYSICS
    Type: NASA. Marshall Space Flight Center Spacelab 3 Mission Science Review; p 64-74
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    NASA TECHNICAL REPORTS
  • 3
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    Mode 1 delamination growth in adhesively bonded joints under static and fatigue loads (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objective of this investigation was to characterize the pure mode 1 delamination growth in metal to metal adhesively bonded joints under static and fatigue loading conditions, using FM 73 adhesive. Double cantilever beam specimens (DCB) were used for pure mode 1 tests. Aluminum 2024-T3 adherends were bonded with FM 73 adhesive. Delamination was introduced during fabrication by inserting a Teflon film between the two adherends. The mode 1 strain energy release rate G sub I sub c was obtained directly from static DCB tests conducted in accordance with the ASTM designation D1876-12. Constant amplitude fatigue tests on DCB specimens were conducted to determine the relationship between delamination growth rate da/dN and strain energy release rate G sub I sub c for a pure mode 1 delamination growth. It is found that the debond propagation rate in adhesive joints using FM 73 is more sensitive to errors in design load than is typical crack growth rate in metallic structures.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-179812 , NAS 1.26:179812
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    NASA TECHNICAL REPORTS
  • 4
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    Effect of biweekly shoot tip harvests on the growth and yield of Georgia Jet sweet potato grown hydroponically (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Sweet potato shoot tips have been shown to be a nutritious green vegetable. A study was conducted to determine the effect of biweekly shoot tip harvests on the growth and yield of Georgia Jet sweet potato grown in the greenhouse using the nutrient film technique (NFT). The nutrient solution consisted of a modified half Hoagland solution. Biweekly shoot tip harvests, beginning 42 days after planting, provided substantial amounts of vegetable greens and did not affect the fresh and dry foliage weights or the storage root number and fresh and dry storage root weights at final harvest. The rates of anion and cation uptake were not affected by tip harvests.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Alabama A & M Univ., NASA-HBCU Space Science and Engineering Research Forum Proceedings; p 9-14
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    NASA TECHNICAL REPORTS
  • 5
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    Relative abundances of sub-iron to iron nuclei in low energy (50-250 MeV/N) cosmic rays as observed in the Skylab experiment (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A Lexan polycarbonate detector exposed on the exterior of Skylab-3 for 73 days during a solar quiet period was used to study the relative abundances of calcium to nickel ions in low energy cosmic rays of 50 to 250 MeV/N. The method of charge identification is based on the measurement of conelength (L) and residual range (R) of these particles in various Lexan sheets. Since more than one cone (sometimes as many as five) is observed and is measured, the charge accuracy becomes precise and accurate. The ratio of (calcium to manganese) to (iron and cobalt) obtained at three energy intervals of 50 to 80, 80 to 150, 150 to 250 and 50 to 250 MeV/N are 7.6 plus or minus 3.8, 2.7 plus or minus 0.8, 1.4 plus or minus 0.6 and 3.3 plus or minus 0.7 respectively. These data thus indicate a large increase of this ratio with decreasing energy. The origin of this strong energy dependence is not understood at present.
    Keywords: SPACE RADIATION
    Type: OG-4.1-4 , 19th Intern. Cosmic Ray Conf - Vol. 2; p 12-15; NASA-CP-2376-VOL-2
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    NASA TECHNICAL REPORTS
  • 6
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    Detector calibration of the Indian cosmic ray experiment (IONS) in Space-Shuttle Spacelab-13 (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In the Indian cosmic ray experiment (IONS) in Spacelab-3 the intention is to study nuclei up to iron in low energy cosmic rays, using CR-39 (DOP) detectors. CR-39 (DOP) was exposed to He4, C12, O16, Ne20, Si28, Ar40, Cr52 and Fe56 accelerated beams from various accelerator facilities available around the world. Different beam energies and exposure angles were used. From these exposures, the charge resolution and energy resolution for the detector in the region of interest were studied. The effect of pre-annealing and depth on the response of our detector was studied. For isotopic resolution, exposed the detector samples were exposed to Ne2O and Ne22 accelerated beams. Samples of CR-39 (DOP) exposed to different accelerated heavy ions were kept in the detector module to take into account the effect of ambient conditions on detector response during the flight.
    Keywords: SPACE RADIATION
    Type: SH-9.1-2 , 19th Intern. Cosmic Ray Conf - Vol. 5; p 458-461; NASA-CP-2376-VOL-5
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    NASA TECHNICAL REPORTS
  • 7
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    Possible origin of the anomalous component of cosmic rays (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The possible origin of the anomalous cosmic rays (ACR) are studied in terms of stellar wind injection from O type stars and their acceleration in shock fronts of SNR's. It is assumed that a fraction of heavy ions will encounter interstellar shock fronts of SNR's and these are accelerated to about 5 to 100 MeV/N and give rise to ACR's. Typically these ions would travel a distance of the order of a few 1000 pc. Therefore it is estimated that O type stars in a volume of radius of a few Kpc around the solar system are contributing to the intensity of ACR in the local ISM. From observational data, the intensity of ACR in the local ISM is estimated. It is suggested that these ACR ions enter the solar system along the solar dipole field lines connected to the interplanetary magnetic field lines.
    Keywords: SPACE RADIATION
    Type: SH-4.6-7 , 19th Intern. Cosmic Ray Conf - Vol. 5; p 184; NASA-CP-2376-VOL-5
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    NASA TECHNICAL REPORTS
  • 8
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    Silicon to iron abundances in solar cosmic rays and in the sun (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Differential spectra of even charged nuclei between Si and Fe in the August 4, 1972 event were made in the energy region of 10 to 40 MeV/n-1 using rocket borne plastic detectors. The resulting relative abundances of elements and low energy enhancements are obtained and compared with spectroscopically determined photospheric abundances. The implications of the relative abundances on the acceleration mechanisms is discussed.
    Keywords: SOLAR PHYSICS
    Type: SH-2.1-6 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 221-224; NASA-CP-2376-VOL-4
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    NASA TECHNICAL REPORTS
  • 9
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    Abundance of low energy (50-150 MeV) antiprotons in cosmic rays (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The progress is presented of the nuclear emulsion experiment to determine abundance of low energy antiprotons in cosmic rays. No antiprotons have been detected so far at upper limit of p/p less than or similar to 4 x .0001 in the energy range 50 MeV to 15 MeV.
    Keywords: SPACE RADIATION
    Type: OG-6.1-1 , 19th Intern. Cosmic Ray Conf - Vol. 2; p 326-329; NASA-CP-2376-VOL-2
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    NASA TECHNICAL REPORTS
  • 10
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    A Model-based Prognostics Methodology for Electrolytic Capacitors Based on Electrical Overstress Accelerated Aging (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: A remaining useful life prediction methodology for electrolytic capacitors is presented. This methodology is based on the Kalman filter framework and an empirical degradation model. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their comparatively low reliability and given their criticality in electronics subsystems they are a good candidate for component level prognostics and health management. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. We present here also, experimental results of an accelerated aging test under electrical stresses. The data obtained in this test form the basis for a remaining life prediction algorithm where a model of the degradation process is suggested. This preliminary remaining life prediction algorithm serves as a demonstration of how prognostics methodologies could be used for electrolytic capacitors. In addition, the use degradation progression data from accelerated aging, provides an avenue for validation of applications of the Kalman filter based prognostics methods typically used for remaining useful life predictions in other applications.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN3987 , Annual Conference of the PHM Society 2011; 25-29 Sept. 2011; Montreal/Canada; United States
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    NASA TECHNICAL REPORTS
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