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  • ACOUSTICS  (2)
  • resistance  (2)
  • 5'-O-demethyl-8-O-methyl-7-epi-dioncophylline A  (1)
  • 5'-O-demethyl-8-O-methyl-dioncophylline A  (1)
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  • 1
    Publication Date: 2013-08-31
    Description: Axial segmentation of acoustically absorbing liners in rectangular, circular or annual duct configurations is a very useful concept for obtaining higher noise attenuation with respect to the bandwidth of absorption as well as the maximum attenuation. As a consequence, advanced liner concepts are proposed which induce a modal energy transfer in both cross-sectional directions to further reduce the noise radiated from turbofan engines. However, these advanced liner concepts require three-dimensional geometries which are difficult to treat theoretically. A very simple three-dimensional problem is investigated analytically. The results show a strong dependence on the positioning of the liner for some incident source modes while the effect of three-dimensional segmentation appears to be negligible over the frequency range considered.
    Keywords: ACOUSTICS
    Type: NASA-TM-80118
    Format: application/pdf
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  • 2
    ISSN: 1572-8927
    Keywords: Cell constant ; conductance ; demal ; electrolytic conductivity ; potassium chloride ; primary standards ; resistance ; specific conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An absolute determination of aqueous electrolytic conductivity has been made for primary standards 0.01D and 0.1D (demal) potassium chloride solutions over the temperature range of 0 to 50°C in 5 degree intervals. A cell with a removable center section of accurately known length and area was used for the measurements. Values were adjusted to be in conformity with the ITS-90 temperature scale. The overall uncertainty over the entire temperature range is estimated to be 0.03%. Values at 25°C for 0.01D and 0.1D KCl solutions are 0.0014086 and 0.012852 S-cm−1, respectively.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8927
    Keywords: Aqueous solution ; cell constant ; conductance ; electrolytic conductivity ; potassium chloride ; primary ; resistance ; resistivity, secondary, standards, and temperature scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Measurements of aqueous electrolytic conductance are performed routinely in a variety of disciplines and industries. Conductivity is a measure of the ionic content in solution and thus has applications in pharmaceuticals, power plants, rainwater, lake surveys, and oceanography, to name a few. A thorough review of the measurement of and standards for aqueous electrolytic conductance is herein presented. At present, the most precise and accurate standards have been set forth by the International Organization of Legal Metrology (OIML), and have been adopted by most other standards organizations. However, the uncertainty assigned to these standards, especially the secondary standards, is somewhat larger than would be expected from the physical aspects of the measurement. Several changes in the units and measurement scales, including temperature, volume, molar mass, resistance, and concentration obfuscate the accuracy of these standards. In addition to the review, research is proposed, using a conductance cell with variable length, to establish new standards for aqueous electrolytic conductance.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0031-9422
    Keywords: 5'-O-demethyl-8-O-methyl-7-epi-dioncophylline A ; 5'-O-demethyl-8-O-methyl-dioncophylline A ; Dioncophyllaceae ; Triphyophyllum peltatum ; atropisomerism. ; biaryls ; naphthylisoquinoline alkaloids ; stem bark
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2019-07-13
    Description: Sound attenuation in a rectangular acoustically lined duct containing uniform mean flow is analytically investigated using the generalized Wiener-Hopf technique. Uniqueness of the solution is enforced for lined sections of the finite axial extent by imposing edge conditions at the liner interface. Possible edge conditions are considered, including the Kutta condition, and the causal solution corresponding to edge conditions is considered the best choice. Solution methods such as the mode matching and singularity methods imply differing edge conditions, and results show that power attenuation is insensitive to the imposed edge conditions, although significant differences are observed for the reflection coefficient. The amplitude of the exponentially increasing instability mode in the lined section must be set to zero as a first approximation to the nonlinear situation, and results indicate that measurements of the reflection factor can be used to make a more definite decision about physically appropriate edge conditions.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 81-2017 , Aeroacoustics Conference; Oct. 5-7, 1981; Palo Alto, CA
    Format: text
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