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641.
Abhishek Singh Douglas D. Walker Barbara S. Minsker Albert J. Valocchi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(6):881-898
The interactive multi-objective genetic algorithm (IMOGA) combines traditional optimization with an interactive framework that considers the subjective knowledge of hydro-geological experts in addition to quantitative calibration measures such as calibration errors and regularization to solve the groundwater inverse problem. The IMOGA is inherently a deterministic framework and identifies multiple large-scale parameter fields (typically head and transmissivity data are used to identify transmissivity fields). These large-scale parameter fields represent the optimal trade-offs between the different criteria (quantitative and qualitative) used in the IMOGA. This paper further extends the IMOGA to incorporate uncertainty both in the large-scale trends as well as the small-scale variability (which can not be resolved using the field data) in the parameter fields. The different parameter fields identified by the IMOGA represent the uncertainty in large-scale trends, and this uncertainty is modeled using a Bayesian approach where calibration error, regularization, and the expert’s subjective preference are combined to compute a likelihood metric for each parameter field. Small-scale (stochastic) variability is modeled using a geostatistical approach and added onto the large-scale trends identified by the IMOGA. This approach is applied to the Waste Isolation Pilot Plant (WIPP) case-study. Results, with and without expert interaction, are analyzed and the impact that expert judgment has on predictive uncertainty at the WIPP site is discussed. It is shown that for this case, expert interaction leads to more conservative solutions as the expert compensates for some of the lack of data and modeling approximations introduced in the formulation of the problem. 相似文献
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Jonas Bergman Stefan Wastegrd Dan Hammarlund Barbara Wohlfarth Stephen J. Roberts 《第四纪科学杂志》2004,19(3):241-249
This paper presents one of the most extensive Holocene tephra records found to date in Scandinavia. Microtephra horizons originating from Icelandic eruptions were recorded in two ca. 2 m thick peat profiles at Klocka Bog in west‐central Sweden. Five of the microtephra horizons were geochemically correlated to the Askja‐1875, Hekla‐3, Kebister, Hekla‐4 and Lairg A tephras respectively. Radiocarbon‐based dating of these tephras broadly agree with previously published ages from Iceland, Sweden, Germany and the British Isles. The identification of the Lairg A tephra demonstrates a more widespread distribution than previously thought, extending the usefulness of Icelandic Holocene tephrochronology further north into west‐central Scandinavia. Long‐lasting snow cover and seasonal wind distribution in the lower stratosphere are suggested as factors that may be responsible for fragmentary tephra deposition patterns in peat deposits of subarctic Scandinavia. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
644.
The Fitzroy estuary (Queensland, Australia) receives large, but highly episodic, river flows from a catchment (144,000 km(2)) which has undergone major land clearing. Large quantities of suspended sediments, and particulate and dissolved organic carbon are delivered. At peak flows, delta(13)C (-21.7+/-0.8 per thousand) and C/N (14.8+/-1.3) of the suspended solids indicate that the particulate organic material entering the estuary is principally soil organic carbon. At the lower beginning flows the particulate organic matter comes from in-stream producers (delta(13)C=-26 per thousand). The DOC load is about 10 times the POC load. Using the inverse method, budgets for POC and DOC were constructed for high and low flows. Under high flows, only a small portion of the POC and DOC load is lost in the estuary. Under dry season (low flow) conditions the estuary is a sink for DOC, but remains a source of POC to the coastal waters. 相似文献
645.
Wal-Mart entered the German market at the end of 1997 but is still running at a loss in its 92 stores. This article tests the hypothesis that there are two main reasons for Wal-Mart’s problems in Germany. First of all, Wal-Mart is competing against very strong and well established deep discounters, especially Aldi. Secondly, there is the difference between the so-called Wal-Mart culture and German customer values. So far, Wal-Mart has not managed to close this gap or create a positive image in Germany. The first part of the article describes the differences between the two retail companies Wal-Mart and Aldi, whereas the second part focuses on the consumer perspective. Four hundred people were interviewed on the phone about their shopping behaviour in the city of Würzburg (northern Bavaria, 140,000 inhabitants). This survey is part of an international study also undertaken in Canada, Great Britain and China. 相似文献
646.
Tetsuya Watanabe Hirohisa Haka Toshifumi Shimizu Eijiro Hiei Robert D. Bentley James Lang Kenneth J. H. Phillips C. David Pike Andrzej Fludra Barbara J. I. Bromage John T. Mariska 《Solar physics》1995,157(1-2):169-184
Solar active-region temperatures have been determined from the full-Sun spectra of helium-like sulphur (Sxv) observed by the Bragg Crystal Spectrometer on board theYohkoh satellite. The average temperature deduced from Sxv is demonstrated to vary with the solar activity level: A temperature of 2.5 × 106 K is derived from the spectra taken during low solar activity, similar to the general corona, while 4 × 106 K is obtained during a higher activity phase. For the latter, the high-temperature tail of the differential emission measure of active regions is found most likely due to the superposition of numerous flare-like events (micro/nano-flares). 相似文献
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649.
Rob Staples Paul Hague Toon Weisenborn Peter Ashton Barbara Michalek 《Geophysical Prospecting》2005,53(2):243-251
In the central North Sea ‘Gannet‐A’ field, a 50 ft oil rim is overlain by a gas cap of variable thickness. Oil is produced from horizontal wells which initially produced dry oil, but as the field became more mature, a significant water cut was seen in several wells. A dedicated 4D seismic monitor survey was acquired in order to assess the remaining distribution of oil reserves. By forward modelling the synthetic seismic response to parameters such as contact movement and residual saturations (using 2D and 3D wedge models), and comparing the results with real seismic data, we are able to decipher the contact movements across the field. It is shown that, in one part of the field, the increased water cut is caused primarily by the vertical displacement of the entire oil rim into the initial gas cap. This oil‐rim displacement produces a very different 4D seismic response from the case of a static gas–oil contact and rising oil–water contact (normal production). As a result of these observations, we are able to optimize field production by both re‐perforation of existing wells and by drilling sidetracks into the displaced rim: a brown‐field development opportunity that might otherwise be missed. 相似文献
650.
2007: International Heliophysical Year 总被引:2,自引:0,他引:2
Prof. Richard Harrison Dr y Breen Dr Barbara Bromage Dr Joe Davila 《Astronomy& Geophysics》2005,46(3):3.27-3.30
The International Heliophysical Year is an international programme of global research to understand the external drivers of the space environment and climate, continuing the tradition of previous International Years. It is introduced here by Richard Harrison, Andy Breen, Barbara Bromage and Joe Davila. 相似文献