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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1310-1314 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The flow over V-groove and U-groove riblets is examined computationally using a time dependent model of the viscous wall region. The flow at the upper bound of the computational domain (y+(approximately-equal-to)40) is described using a streamwise eddy model. Both drag neutral and drag reducing riblets are considered. Results suggest that the riblets limit the lateral spread of inrushes towards the wall and retain low momentum fluid in the riblet valleys, thereby effectively isolating much of the wall from such inrushes. The generation of intermittent secondary vortices within the riblet valleys also occurs; however, these appear to be both quite weak and fairly short-lived.
    Type of Medium: Electronic Resource
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  • 2
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    Nottingham : Periodicals Archive Online (PAO)
    Nottingham medieval studies. 38 (1994) 152 
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  • 3
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    Harlow, etc. : Periodicals Archive Online (PAO)
    English Historical Review. 53 (1938) 577 
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  • 4
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    Gloucester : Periodicals Archive Online (PAO)
    Parliamentary history. 9:2 (1990) 372 
    ISSN: 0264-2824
    Topics: History , Political Science
    Description / Table of Contents: Reviews of Books
    Notes: Parliament and Communities in the Middle Ages
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 18 (1994), S. 10-16 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Enhanced Variable Interval Time Averaging (EVITA) is introduced as a method that incorporates structure information directly into the detection method. The paper tests VITA and EVITA against an ersatz turbulence signal (antisymmetric exponential time decay) inserted into a random noise distribution. It is shown that EVITA is much less dependent than VITA on the choice of both threshold level and averaging time. EVITA is then applied to particle image velocimetry turbulence data from channel flow [7] at Re = 2872, and is shown to effectively extract bursting events.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-1561
    Keywords: Allelochemicals ; no-tillage ; conventional-tillage ; soils ; wheat ; Triticum aestivum ; mass spectrometry ; Petri-dish bioassay ; fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Putative allelochemicals found in the soil of no-tillage and conventional-tillage wheat plots near Stillwater, Oklahoma, were obtained by a mild alkaline aqueous extraction procedure, bioassayed to determine their biological activity, purified, and analyzed with a capillary gas chromatography-mass spectrometry-data analysis system. The most significant inhibition was found in bioassays of extracts from soil collected immediately after harvest in June, July, and August. No-tillage soils produced significant inhibition during the rest of the year also. Mass spectrometry showed fatty acids as the most abundant compounds. However, when bioassayed authentic samples of the five free fatty acids showed no significant biological activity toward wheat.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Flow, turbulence and combustion 51 (1993), S. 563-567 
    ISSN: 1573-1987
    Keywords: riblets ; turbulence modelling ; near-wall turbulent structures ; control-volume finite element methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The flow over drag reducing riblets is examined computationally using a time-dependent model of the viscous wall region. The flow at the upper bound of the computational domain (y +≃40) is described using a streamwise eddy model consisting of two scales. A control-volume finite-element method utilizing triangular meshes is used to exactly fit the riblet cross-sectional geometry. Observations of the transient flow conditions suggest that the riblets limit the lateral spread of fluid inrushes towards the wall and retain low momentum fluid in the riblet valleys effectively isolating much of the wall from such inrushes. The generation of intermittent secondary vortices within the riblet valleys also occurs; however, these appear to be quite weak and fairly short-lived.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Flow, turbulence and combustion 50 (1993), S. 299-314 
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The flow over riblets is examined computationally using a time dependent model of the viscous wall region. This “2 1/2 D model”, developed by Hatziavramidis and Hanratty (1979) and modified by Nikolaides (1984) and Chapman and Kuhn (1981, 1986) assumes homogeneity in the streamwise direction so that the flow is solved only in the cross-sectional plane. The flow at the upper boundary of the computational domain (y + ≅ 40) is described using a streamwise eddy model consisting of two scales, one of the streak spacing (λ+ ≅ 100), which dominates vertical momentum transport, and a larger scale that accounts for the influence of large outer flow eddies. The protrusion height concept (Bechert and Bartenwerfer, 1989) is used to define ay +=0 location for surfaces with riblets. A control volume finite element method utilizing triangular meshes is used to exactly fit the riblet cross-sectional geometry. Results obtained using fairly large riblets compare well with the limited experimental evidence available. Observations of the transient flow suggest that the riblets interact with the near-wall streamwise vortices, weakening them by the generation of intermittent secondary vortices within the riblet valleys. The riblets also appear to limit the lateral spread of inrushes towards the wall and retain low momentum fluid in the riblet valleys effectively isolating much of the wall from such inrushes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 17 (1991), S. 1909-1916 
    ISSN: 1573-1561
    Keywords: Serotonin ; nettles ; trichomes ; stinging hairs ; plant defense mechanisms ; Urtica dioica ; Cnidoscolus texanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Plants known as nettles bear trichomes that deliver a painful sting when touched. Studies of members of the Urticaceae have suggested that their trichomes may contain histamine, acetylcholine, and serotonin. We report investigations using TLC, HPLC, and UV-VIS spectrophotometry to analyze the hair fluids ofCnidoscolus texanus, a member of the Euphorbiaceae, along with standards of known histamine, acetylcholine, and serotonin. Of these, only serotonin was detected in hair extracts. Up to four other compounds were detected and partially characterized, but they have not been identified.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 18 (1994), S. 733-746 
    ISSN: 0271-2091
    Keywords: Penalty function ; Finite volume ; Direct Solver ; D'Yakonov ; Laminar ; Turbulent (k-∊) ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A penalty function, finite volume method is described for two-dimensional laminar and turbulent flows. Turbulence is modelled using the k-∊ model. The governing equations are discretized and the resulting algebraic equations are solved using both sequential and coupled methods. The performance of these methods is gauged with reference to a tuned SIMPLE-C algorithm. Flows considered are a square cavity with a sliding top, a plane channel flow, a plane jet impingement and a plane channel with a sudden expansion. A sequential method is employed, which uses a variety of dicretization practices, but is found to be extremely slow to converge; a coupled method, evaluated using a variety of matrix solvers, converges rapidly but, relative to the sequential approach, requires larger memory.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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