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Max Planck 《Die Naturwissenschaften》1938,26(48):777-779
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Retreat and advance of shoreline position occurs naturally, and also as a result of defences which are constructed to prevent
erosion and flooding. Retreat more commonly manifests itself down-drift of defences due to a sediment deficit causing the
coast to become ‘set-back’. Advance normally develops due to sediment accumulation up-drift of a barrier inhibiting longshore
drift, resulting in the coast becoming ‘set-forward’. Many examples of set-backs and set-forwards are recorded, but their
location, number and cause is not known on a national scale. Using the Futurecoast aerial photographs, approximately 200 localities
were identified as set-back or set-forward in England and Wales, with half situated in the Eastern and South East regions
of England. Half of the total set-backs or set-forwards were on cliffed coasts, and half on low-lying coasts. Without local
knowledge it is difficult to distinguish between set-backs and set-forwards. Set-backs often indicate higher retreat rates,
thus threatening cliff-top infrastructure which requires defence upgrade and extensions, as well as raising maintenance costs.
Monitoring set-backs is important for shoreline management, because as retreat continues, set-backs evolve and artificial
headlands form and grow. This is reinforced by the shift from hard defence policies towards softer engineering approaches,
managed realignment and limited intervention. 相似文献
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Markus Stumm Michael Entezami Karsten Haug Cornelia Blank Max Wüstemann Bernt Schulze Gisela Raabe-Meyer Maja Hempel Markus Schelling Eva Ostermayer Sabine Langer-Freitag Tilo Burkhardt Roland Zimmermann Tina Schleicher Bernd Weil Ulrike Schöck Patricia Smerdka Sebastian Grömminger Yadhu Kumar Wera Hofmann 《黑龙江环境通报》2014,34(2):185-191
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Flanagan JB Jayanty RK Rickman EE Peterson MR 《Journal of the Air & Waste Management Association (1995)》2006,56(4):492-499
The objectives of this paper are to contrast the relative variability of replicate laboratory measurements of selected chemical components of fine particulate matter (PM) with total variability from collocated measurements and to compare the magnitudes of the uncertainties determined from collocated sampler data with those currently being provided to U.S. Environmental Protection Agency (EPA)'s Air Quality System (AQS) database by RTI International (RTI). Pointwise uncertainty values are needed for modeling and data analysis and should include all the random errors affecting each data point. Total uncertainty can be decomposed into two primary components: analytical measurement uncertainty and sampling uncertainty. Analytical measurement uncertainties are relatively easy to calculate from routine quality control (QC) data. Sampling uncertainties, on the other hand, are comparatively difficult to measure. In this paper, the authors describe data from collocated samplers to provide a snapshot of whole-system uncertainty for several important chemical species. The components of uncertainty were evaluated for key species from each of the analytical methods employed by the PM2.5 Speciation Trends Network (STN) program: gravimetry, ion chromatography (IC), X-ray fluorescence (XRF), and thermal-optical analysis for organic carbon and elemental carbon. The results show that the laboratory measurement uncertainties are typically very small compared with uncertainties calculated from the differences between samples collected from collocated samplers. These differences are attributable to the "field" components uncertainty, which may include contamination and/or losses during shipping, handling, and sampling, as well as other distortions of the concentration level due to flow and sample volume variations. Uncertainties calculated from the collocation results were found to be generally similar to the uncertainties currently being loaded into EPA's AQS system, with some exceptions described below. 相似文献
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