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51.
Tom Koch Kenneth Denike 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(5):523-531
The problem is not uncertainty—proposed here as an inevitable condition—but the chimera of certainty asserted by most contemporary
researchers. Problems of data definition, collection, and their use are reviewed in terms of spatial epidemiology and health
data with examples drawn from several areas of contemporary health research. The argument is that preconceptions limit data
modeled in a manner assuming its completeness. The result, as the West Nile Virus example seeks to demonstrate, may obscure
other patterns and limit avenues of research. 相似文献
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A New Lichenometric Dating Curve For Southeast Iceland. 总被引:2,自引:0,他引:2
Tom Bradwell 《Geografiska Annaler: Series A, Physical Geography》2001,83(3):91-101
This paper presents a new lichenometric dating curve for southeast Iceland. The temporal framework for the curve is based on reliably dated surfaces covering the last 270 years, making it the best constrained study of this nature conducted in Iceland. The growth of lichen species within Rhizocarpon Section Rhizocarpon is non-linear over time, with larger (older) thalli apparently growing more slowly. The linear 'growth' curves derived previously by former authors working in Iceland represent only part of a curve which has an overall exponential form. Reasons for the non-linearity of the new dating curve are probably physiological, although climatic change over the last three centuries cannot be ruled out. Use of linear 'growth' curves in Iceland is problematic over time-spans of more than c . 80 years. Pre-20th century moraines dated using a constant, linear relationship between lichen size and age are probably older than previously believed. Those moraines lichenometrically 'dated' to the second half of the 19th century in Iceland may actually pre-date this time by several decades (30–100 years), thus throwing doubt on the exact timing of maximum glaciation during the 'Little Ice Age'. 相似文献
55.
On using mixed-layer transport parameterizations with radiometric surface temperature for computing regional scale sensible heat flux 总被引:4,自引:0,他引:4
Recent mixed-layer formulations for computing large-scale surface energy fluxes under daytime convective conditions do not require the estimation of surface-layer parameters, such as the roughness lengths for momentum and heat. This greatly simplifies approaches using operational satellite measurements of surface temperature for computing the surface energy balance at regional scales because the surface roughness parameters are not well known for many landscapes. The utility of such mixed-layer formulations is tested using data from several recent multidisciplinary field experiments (HAPEX-MOBILHY, FIFE and Monsoon 90). The results indicate that specific mixed-layer formulations adequately simulate surface sensible heat fluxes in the grassland and shrubland sites. However, use of the original values of proposed empirical coefficients for the forested site yield poor results. This is probably due to the fact that the forested site has significantly different surface geometry and associated distribution of temperature among the surface components (especially the relative importance of soil background temperatures) compared to the other sites. Therefore, the relationship between aerodynamic and radiometric surface temperature may have greatly differed between the forested site and the other locations. However, differences in aerodynamic roughness between the experimental sites were not correlated with changes required in the values of the coefficients. Instead, a two-source model which makes the distinction between aerodynamic and radiative temperature is proposed, as a means to determine which surface properties significantly affect the magnitude of the mixed-layer coefficients. 相似文献
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Tom K. Ekström 《Contributions to Mineralogy and Petrology》1973,38(4):329-338
Hydrothermal syntheses of chlor-hydroxyapatite have been carried out between 300 and 700° C at a constant pressure of 1000
bar. The substitution of OH for Cl varies as a function of the amount of added CaCl2, temperature, and pH. In the main reaction the incorporation of Cl is negligible at 300° C but increases to over 40 mole
percent Cl-apatite at 700° C. A simple X-ray method for determining the Cl/Cl+OH ratio has been developed and this is also
extended to fluorine-bearing chlor-hydroxyapatites. A number of natural chlor-fluorhydroxyapatites are discussed in the light
of the X-ray method and the result of the synthesis. 相似文献
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Rigorous equations in compact symbolic matrix notation are introduced to transform coordinates and velocities between ITRF
frames and modern GPS-based geocentric geodetic datums. The theory is general but, after neglecting higher than second-order
terms, it is shown that the equations revert to the formulation currently applied in most major continental datums. We discuss
several examples: the North American Datum of 1983 (NAD83), the European Terrestrial Reference System of 1989 (ETRS89), the Geodetic Datum of Australia of 1994 (GDA94), and the South American Geocentric Reference System (SIRGAS).
Electronic Publication 相似文献