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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 23 (1984), S. 207-210 
    ISSN: 1435-1528
    Keywords: Shear viscosity ; liquid crystal ; nematic phase ; smectic phase ; biphenyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Rheological measurements have been carried out using a rotational viscometer with a system of coaxial cylinders on four liquid crystalline substances from the group of cyanobiphenyls. On the basis of results of these investigations it was found that in the investigated range of shear rates the nematic phases exhibited Newtonian flow behaviour, while the smectic phases exhibited non-Newtonian behaviour. For shear rates up to ca. 1000 s−1 the dependence of the shear stress on shear rate is well described by a power-law model.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1984-01-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
    Publication Date: 2011-08-18
    Description: A high-temperature Hall-effect apparatus is described which allows measurements up to temperatures greater than 1200 K using the van der Pauw method. The apparatus was designed for measurements on refractory materials having high charge carrier concentrations and generally low mobilities. Pressure contacts are applied to the samples. Consequently, special contacting methods, peculiar to a specific sample material, are not required. The apparatus has been semiautomated to facilitate measurements. Results are presented on n- and p-type silicon.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 55; 110-113
    Format: text
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  • 4
    Publication Date: 2019-06-28
    Description: Radioisotope Thermoelectric Generators (RTG) that will supply electrical power to the Galileo and International Solar Polar Mission (ISPM) spacecraft are exposed to several degradation mechanisms during the prolonged ground storage before launch. To assess the effect of storage on the RTG flight performance, a computer code has been developed which simulates all known degradation mechanisms that occur in an RTG during storage and flight. The modeling of these mechanisms and their impact on the RTG performance are discussed.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 5
    Publication Date: 2019-07-13
    Description: Features of the DEGRA 2 computer code for simulating the operations of a spacecraft thermoelectric generator are described. The code models the physical processes occurring during operation. Input variables include the thermoelectric couple geometry and composition, the thermoelectric materials' properties, interfaces and insulation in the thermopile, the heat source characteristics, mission trajectory, and generator electrical requirements. Time steps can be specified and sublimation of the leg and hot shoe is accounted for, as are shorts between legs. Calculations are performed for conduction, Peltier, Thomson, and Joule heating, the cold junction can be adjusted for solar radition, and the legs of the thermoelectric couple are segmented to enhance the approximation accuracy. A trial run covering 18 couple modules yielded data with 0.3% accuracy with regard to test data. The model has been successful with selenide materials, SiGe, and SiN4, with output of all critical operational variables.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: IECEC ''82; Seventeenth Intersociety Energy Conversion Engineering Conference; Aug 08, 1982 - Aug 12, 1982; Los Angeles, CA
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  • 6
    Publication Date: 2019-07-13
    Description: A joint JPL-NASA program to develop an automated system to measure the thermoelectric properties of newly developed materials is described. Consideration is given to the difficulties created by signal drift in measurements of Hall voltage and the Large Delta T Seebeck coefficient. The benefits of a computerized system were examined with respect to error reduction and time savings for human operators. It is shown that the time required to measure Hall voltage can be reduced by a factor of 10 when a computer is used to fit a curve to the ratio of the measured signal and its standard deviation. The accuracy of measurements of the Large Delta T Seebeck coefficient and thermal diffusivity was also enhanced by the use of computers.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IECEC ''84: Advanced energy systems - Their role in our future; Aug 19, 1984 - Aug 24, 1984; San Francisco, CA
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