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  • 1
    Electronic Resource
    Electronic Resource
    Influences of temperature, pressure and eluent composition on the behavior of binary eluents at sub- and supercritical conditions. Pentane and diethyleneglycol dimethyl ether (1987)
    Springer
    Chromatographia 23 (1987), S. 171-178 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography (SFC) ; Binary eluents ; Sub- and supercritical conditions ; Capacity ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In supercritical fluid chromatography (SFC), studies on binary eluents composed of pentane and diethyleneglycol dimethylether were performed in the concentration rage of 5 to 15% of the ether compound and at pressures of 20 to 50 bar. Influences of temperature, pressure and eluent composition on the behavior of the mobile phase were found to closely resemble those for pentane-dioxane mixtures. Resolution depended on variations in capacity ratios, selectivities, and plate numbers. The critical data for diethyleneglycol dimethylether were estimated by means of different group contribution methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311475
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple gradients in supercritical fluid chromatography (SFC). Ternary gradients by programming eluent composition and temperature at varying pressure (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 525-527 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Eluent composition gradients ; Temperature gradients ; Resolution ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090908
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of temperature and mobile phase density on retention and efficiency in supercritical fluid chromatography (1987)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 519-521 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Retention ; Plate number ; Resolution ; Temperature and density effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240100909
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  • 4
    Electronic Resource
    Electronic Resource
    Isocratic networks in supercritical fluid chromatography (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 566-571 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Three-dimensional diagrams ; Capacity ratio ; Resolution ; Temperature dependence ; Pressure dependence ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For chromatography with supercritical fluids (SFC), the dependence of the capacity ratios k′ and of the mean resolution Rm on temperature and pressure is presented as a three-dimensional diagram. A sufficient number of test chromatograms were run for the diagram to lead to an isocratic network in form of a curved surface. The isocratic network possesses a characteristic shape and contains all information about the temperature and pressure dependence of k′ and Rm for a given volume flow rate and chromatographic system. The specific system studied comprised pentane as the mobile phase, unmodified silica as the stationary phase, and a set of four polycyclic hydrocarbons as the test mixture. The isocratic net of this system allows interpolation of k′ and Rm for any temperature and pressure. Together with similar experimental data from other systems, this allows qualitative forecasts about the isocratic nets of other systems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240091005
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  • 5
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    Rotor noise (1991)
    In:  CASI
    Details
    Publication Date: 2006-06-13
    Description: The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.
    Keywords: ACOUSTICS
    Type: NASA. Langley Research Center, Aeroacoustics of Flight Vehicles: Theory and Practice. Volume 1: Noise Sources; p 65-149
    Format: text
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  • 6
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    Experiment versus theory (1982)
    In:  CASI
    Details
    Publication Date: 2006-04-17
    Description: High speed compressibility noise and vortex interaction noise, which are aerodynamically generated noise sources, were investigated. Noise generating mechanisms were identified. Linear and nonlinear theory were compared and are in agreement with data on amplitude and wave forms. The interaction area between the acoustic planform and blade/vortex interaction lines are examined.
    Keywords: ACOUSTICS
    Type: NASA. Langley Research Center Rotorcraft Noise; p 319-330
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  • 7
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    Rotary wing aerodynamically generated noise (1982)
    In:  CASI
    Details
    Publication Date: 2006-04-17
    Description: The history and methodology of aerodynamic noise reduction in rotary wing aircraft are presented. Thickness noise during hover tests and blade vortex interaction noise are determined and predicted through the use of a variety of computer codes. The use of test facilities and scale models for data acquisition are discussed.
    Keywords: ACOUSTICS
    Type: NASA. Langley Research Center Rotorcraft Noise; p 97-106
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  • 8
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    Helicopter impulsive noise - Theoretical and experimental status (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
    Keywords: ACOUSTICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 109; 361-422
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  • 9
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    Helicopter impulsive noise - Theoretical and experimental status (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory/experiment are suggested.
    Keywords: ACOUSTICS
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  • 10
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    Helicopter model rotor-blade vortex interaction impulsive noise - Scalability and parametric variations (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scalig deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.
    Keywords: ACOUSTICS
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