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- Buchan, K. L., et al.
(författare)
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Comparing the drift of Laurentia and baltica in the Proterozoic : the importance of key palaeomagnetic poles
- 2000
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Ingår i: Tectonophysics. - 0040-1951 .- 1879-3266. ; 319:3, s. 167-198
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Tidskriftsartikel (refereegranskat)abstract
- Key palaeomagnetic poles are defined as those which pass basic reliability criteria and are precisely and accurately dated. They allow a more rigorous analysis of Precambrian continental drift and continental reconstructions than the traditional apparent polar wander path (APWP) approach using mostly non-key poles. Between ca. 2.45 and 2.00 Ga in the early Palaeoproterozoic, key poles define the drift of the Archaean Superior craton of Laurentia, yielding a result that is quite unlike the drift interpreted in earlier studies using the APWP method. There are no early Palaeoproterozoic key poles for the other Archaean cratons that amalgamated to form Laurentia and Baltica prior to 1.8 Ga, so that a rigorous test of early Palaeoproterozoic reconstruction models is not possible. Key poles from Laurentia between ca. 1.46 and 1.267 Ga and Baltica between 1.63 and 1.265 Ga help to define, in a preliminary fashion, the early Mesoproterozoic drift of the two shields. The key pole age match at ca. 1.265 Ga is consistent with Baltica located adjacent to eastern Greenland, and geological considerations suggest that the most reasonable fit aligns the Labradorian belt of Laurentia with the Gothian belt of Baltica. Although there is limited support from non-key poles and key poles that are not matched in age for such a fit as early as ca. 1.8 Ga, no rigorous assessment will be possible until a match in key pole ages is achieved. In the late Mesoproterozoic to Neoproterozoic, Laurentia's drift is reasonably well documented by seven key poles between 1.235 and 0.73 Ga. There are no key poles in this period from Baltica, however, so that a ≈90° clockwise rotation of Baltica relative to Laurentia between 1.265 and 1.0 Ga, widely used in the literature, cannot be confirmed.
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| 2. |
- Tarnawski, V.R., et al.
(författare)
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Inter-particle contact heat transfer in soil systems at moderate temperatures
- 2002
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 26:15, s. 1345-1358
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Tidskriftsartikel (refereegranskat)abstract
- An inter-particle contact heat transfer model for evaluating soil thermal conductivity is analysed with respect to soils, representing different textural classes, exposed to moderate temperatures ranging from 15 to 30°C. This model is a combination of a self-consistent approximation model, enhanced with an inter-particle contact heat transfer correction coefficient. For dry and saturated soils, this coefficient is defined as a ratio of a soil harmonic mean thermal conductivity of solid and fluid (air or water) phases, to the average thermal conductivity of soil solid grains. For unsaturated soils, we assume a linear interpolation of the correction coefficient between absolutely dry and saturated states, with a Kersten function (Ke) as a proportional factor. The strongest impact of the correction coefficient (maximum reduction of heat transfer) is observed for coarse soils below a critical value of saturation degree (Sr-cr-corresponds to Ke ? 0) followed by medium and fine soils. For Sr > Srcr, the reduction of heat transfer gradually diminishes as Sr approaches 1 (i.e. saturated state). Soil texture, soil specific surface area, porosity and mineralogical composition (particularly quartz content) are important factors influencing the heat transfer correction coefficient. Their influence appears to be more substantial at the lower half of the wetness range (Sr < 0.5). Simulation results from the new enhanced model closely follow experimental data. © 2002 John Wiley and Sons, Ltd.
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