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  • 1990-1994  (4)
  • 1945-1949
  • Chemical Engineering  (2)
  • 07.65.-b  (1)
  • 82.40.Py  (1)
  • A/Ci  (1)
Material
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 58 (1994), S. 459-466 
    ISSN: 1432-0649
    Keywords: 82.40.Py ; 07.20.Dt ; 07.65.-b ; 33.20.Lg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the use of Degenerate Four-Wave Mixing (DFWM) in the OHA 2 Σ + ←X 2 ∏ (υ′ = 0 ←υ″ = 0) band for temperature determination in a propane/air flame using laser powers below the saturation level. We show that at these low power levels the dependence of the signal on the dipole moment for the transition has to be established before meaningful temperature data can be obtained. This presents a paradox in that the temperature has to be known before the form of the dependence on the dipole moment can be determined. Solutions to this paradox are presented. We also show that absorption of the laser beams in this OH band system cannot be neglected and that failure to correctly account for the absorption leads to a large over estimate of the flame temperature. Furthermore, we show that the accuracy of the absorption-corrected temperature is critically dependent on the accuracy with which the measurement position within the flame is known. Finally, the temperature calculated from DFWM spectra using the correct dipole moment power and absorption is compared to the temperatures obtained using Laser-Induced Fluorescence (LIF) and Coherent Anti-Stokes Raman Spectroscopy (CARS).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: A/Ci ; C3 ; CAM ; Pi regeneration ; RuBP carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of nine tropical species varying in growth and carbon metabolism were exposed to twice the current atmospheric level of CO2 for a 3 month period on Barro Colorado Island, Panama. A doubling of the CO2 concentration resulted in increases in photosynthesis and greater water use efficiency (WUE) for all species possessing C3 metabolism, when compared to the ambient condition. No desensitization of photosynthesis to increased CO2 was observed during the 3 month period. Significant increases in total plant dry weight were also noted for 4 out of the 5 C3 species tested and in one CAM species, Aechmea magdalenae at high CO2. In contrast, no significant increases in either photosynthesis or total plant dry weight were noted for the C4 grass, Paspallum conjugatum. Increases in the apparent quantum efficiency (AQE) for all C3 species suggest that elevated CO2 may increase photosynthetic rate relative to ambient CO2 over a wide range of light conditions. The response of CO2 assimilation to internal Ci suggested a reduction in either the RuBP and/or Pi regeneration limitation with long term exposure to elevated CO2. This experiment suggests that: (1) a global rise in CO2 may have significant effects on photosynthesis and productivity in a wide variety of tropical species, and (2) increases in productivity and photosynthesis may be related to physiological adaptation(s) to increased CO2.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 373-377 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1157-1163 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A knowledge of flow behavior is important in the study of laminar flow in twin-screw extrusion processes to predict the velocity distribution and to understand the mixing process. The flow of a power law fluid in self-wiping twin-screw extruders is examined using a two-dimensional finite element analysis of a mid-channel section of intermeshing screws. Theory is compared with experiment using food biopolymer and plastic materials. Comparisons showing overprediction of throughputs, but similarities in behavior, suggest that this model could provide an upper limit for melt conveying. For most of the throughput range examined, pumping of intermeshing self-wiping screws appears to be almost independent of the power law flow index of the melt extruded, but the value of the flow index determines the degree of influence intermeshing has on the overall pressure gradient generated in the extruder.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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