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  • 1
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    Evaluation and optimization of the advanced signal counting techniques on weldments (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The signal counting technique with the Delta ultrasonic method is evaluated and optimized for flaw detection in aluminum welds. A comparison is made between the counting and conventional amplitude-gate methods to detect flaws. No conclusion is drawn on the sensitivity of these two methods to detect flaws when the mismatch at the welds is small (25 mils or less). When the mismatch is 25 mils or more, the signal counting method is more sensitive. Of the 24 welded specimens, 50 flaws were found by X-ray inspection and 59 by the Delta method. On 1/4-inch thick welds, X-ray is equal to or slightly more sensitive than Delta method, but on the 1/2-inch thick welds Delta ultrasonic appears more sensitive in flaw detection.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-CR-123649 , FZM-5917
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Air Circulation and Heat Exchange Under Reduced Pressures (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Heat exchange rates decrease non-linearly with reductions in atmospheric pressure. This decrease creates risk of thermal stress (elevated leaf temperatures) for plants under reduced pressures. Forced convection (fans) significantly increases heat exchange rate under almost all pressures except below ~ 10 kPa. Plant cultivation techniques under reduced pressures will require forced convection. The cooling curve technique is a reliable means of assessing the influence of environmental variables like pressure and gravity on gas exchange of plant. These results represent the extremes of gas exchange conditions for simple systems under variable pressures. In reality, dense plant canopies will exhibit responses in between these extremes. More research is needed to understand the dependence of forced convection on atmospheric pressure. The overall thermal balance model should include latent and radiative exchange components.
    Keywords: Life Sciences (General)
    Type: KSC-2010-137 , Committee on SQace Research (COSPAR) meeting; Jul 18, 2010 - Jul 23, 2010; Bremen; Germany
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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