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  • Electronic Resource  (2)
  • Ammonium  (1)
  • Building effects  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Extraction of nitrogen from soils (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 189-190 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen ; Ammonium ; Nitrate ; Nitrogen extraction ; Soils ; Nitrogen mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A roller bed and rotary end-over-end shaker were compared for the extraction of mineral N from a variety of soil types; both were equally efficient with an optimum extraction time of 30 min. However, the roller bed permitted a greater operational capacity, a faster throughput of samples, and easier identification of sample bottles compared with the end-over-end shaker. More NH4 +-N and NO3 −-N (P〈0.001) was recovered from soil by 2 M KCl than by any other extractant, in a soil: extractant ratio of 1 to 5 (w:v), except water, which was equally efficient at removing NO3 −-N from soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257765
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Modelling The Mean Velocity Profile In The Urban Canopy Layer (2000)
    Springer
    Boundary layer meteorology 97 (2000), S. 25-45 
    Details
    ISSN: 1573-1472
    Keywords: Building effects ; Roughness length ; Turbulence scale ; Urban canopy ; Urban pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A simple model originally derived for meanwind speed profiles in vegetative canopy flows ismodified for application to arrays ofthree-dimensional surface obstacles (cubes), whichcould be representative of a simple urban-typesurface. It is shown that for cube arrays that arenot too densely packed, the predicted exponentialvelocity profile provides an adequate fit to thespatially averaged velocity profile (u(z))within the obstacle canopy. Application of the model to a set of wind-tunnel dataallows for the evaluation of an empirical fittingparameter called the attenuation coefficient. This isrelated to the turbulence length scale, which can befound by manipulating the results of thegradient-diffusion model used to derive the velocityprofile. The results show a reduction of theturbulence length scale with increasing obstaclepacking density. By assuming a linear transition fromthis length scale at the top of the canopy to theclassical Prandtl length scale in the overlyinginertial sublayer, an acceptable model is obtained forthe full velocity profile within simple obstaclearrays, from the ground up to the overlyingsemi-logarithmic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002785830512
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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