Fluvial processes and environmental change A.G. BROWN and T.A. QUINE (eds) Publisher John Wiley & Sons,Chichester 1999 (413 pp) $160 ISBN 0‐471‐98548‐1     

Rick Shakesby 《第四纪科学杂志》2000,15(5):562-563

  相似文献   

Improving Coal Quality Estimations with Geostatistics and Geophysical Logs     

Jeuken  Rick  Xu  Chaoshui  Dowd  Peter 《Natural Resources Research》2020,29(4):2529-2546

In most modern coal mines, there are many coal quality parameters that are measured on samples taken from boreholes. These data are used to generate spatial models of the coal quality parameters, typically using inverse distance as an interpolation method. At the same time, downhole geophysical logging of numerous additional boreholes is used to measure various physical properties but no coal quality samples are taken. The work presented in this paper uses two of the most important coal quality variables—ash and volatile matter—and assesses the efficacy of using a number of geostatistical interpolation methods to improve the accuracy of the interpolated models, including the use of auxiliary variables from geophysical logs. A multivariate spatial statistical analysis of ash, volatile matter and several auxiliary variables is used to establish a co-regionalization model that relates all of the variables as manifestations of an underlying geological characteristic. A case study of a coal mine in Queensland, Australia, is used to compare the interpolation methods of inverse distance to ordinary kriging, universal kriging, co-kriging, regression kriging and kriging with an external drift. The relative merits of these six methods are compared using the mean error and the root mean square error as measures of bias and accuracy. The study demonstrates that there is significant opportunity to improve the estimations of coal quality when using kriging with an external drift. The results show that when using the depth of a sample as an external drift variable there is a significant improvement in the accuracy of estimation for volatile matter, and when using wireline density logs as the drift variable there is improvement in the estimation of the in situ ash. The economic benefit of these findings is that cheaper proxies for coal quality parameters can significantly increase data density and the quality of estimations.

  相似文献   

Abundance of brown trout as related to littoral zone gradient in Lakes Te Anau and Manapouri,New Zealand     

Rick J. Stoffels  Gerard P. Closs 《新西兰海洋与淡水研究杂志》2013,47(2):455-458

Adult brown trout (Salmo trutta L.) in lakes are primarily littoral/benthic foragers. We predicted that the distribution of adult brown trout in lakes would be shaped by foraging demands, and that they would be more abundant in gently sloping littoral areas, that is, littoral areas that have a greater space available to support benthic foraging habitats. To address this hypothesis, we measured abundance of brown trout among littoral areas with different gradients in Lakes Te Anau and Manapouri. There was a significant negative relationship between littoral zone gradient and relative abundance (CPUE) of adult brown trout. This result supports the hypothesis that brown trout aggregate in littoral areas with greater amounts of foraging habitat in Fiordland lakes.  相似文献   

Two new species of Pseudostomella (Gastrotricha: Macrodasyida) with scaled triancres from the east coast of Australia   总被引：1，自引：1，他引：0  

Rick Hochberg 《新西兰海洋与淡水研究杂志》2013,47(3):571-579

Two new species of Pseudostomella from North Stradbroke Island, Australia, P. klauserae n. sp. and P. megapalpator n. sp., are characterised by scaled triancres, cuticular structures that until now were known only from one other member of the genus. The structure of the scaled triancres in both species is new: the triancre base is diamond‐ or triangular‐shaped with three shafts that arise to form feather‐like scales. P. klauserae n. sp. is characterised by scales arising from a diamond‐shaped triancre base, the distribution of cephalic papillae, and the abundance and distribution of anterior and lateral adhesive tubes. P. megapalpator n. sp. is distinguished by scales arising from a rounded‐triangular triancre base, large dorsal, digitiform papillae, and ventral adhesive tubes. The presence of two new species with scaled triancres allows for the formation of a novel species complex within the genus. An amended key to the species is included.  相似文献   

Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System     

Bishwajit Chakraborty  Hans Werner Schenke  Vijay Kodagali  Rick Hagen 《Marine Geodesy》2013,36(1-2):19-26

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.  相似文献   

Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America     

Torben C. Rick  Gregory A. Henkes  Darrin L. Lowery  Steven M. Colman  Brendan J. Culleton 《Quaternary Research》2012,77(1):205-210

Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (?R) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ?R, ranging from 148 ± 46 ¹⁴C yr on the Potomac River to ? 109 ± 38 ¹⁴C yr at Swan Point, Maryland. The ?R weighted mean for the Chesapeake's Western Shore (129 ± 22 ¹⁴C yr) is substantially higher than the Eastern Shore (? 88 ± 23 ¹⁴C yr), with outer Atlantic Coast samples falling between these values (106 ± 46 and 2 ± 46 ¹⁴C yr). These differences may result from a combination of factors, including ¹⁴C-depleted freshwater that enters the bay from some if its drainages, ¹⁴C-depleted seawater that enters the bay at its mouth, and/or biological carbon recycling. We advocate using different subregional ?R corrections when calibrating ¹⁴C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America.  相似文献   

Information systems playground—the target infrastructure     

Andrey N. Belikov  Fokke Dijkstra  Hans Gankema  Jeroen B. A. N. van Hoof  Rick Koopman 《Experimental Astronomy》2013,35(1-2):367-389

The Target infrastructure has been specially built as a storage and compute infrastructure for the information systems derived from Astro-WISE. This infrastructure will be used by several applications that collaborate in the area of information systems within the Target project. It currently consists of 10 PB of storage and thousands of computational cores. The infrastructure has been constructed based on the requirements of the applications. The storage is controlled by the Global Parallel File System of IBM. This file system takes care of the required flexibility by combining storage hardware with different characteristics into a single file system. It is also very scalable, which allows the system to be extended into the future, while replacing old hardware with new technology.  相似文献   

The Cognitive Load of Geographic Information     

Rick L. Bunch  Robert Earl Lloyd 《The Professional geographer》2006,58(2):209-220

Multimedia presentations that combine verbal and visual information are increasingly becoming important methods for communicating geographic information. This article discusses literature related to cognitive load theory (CLT) and offers ideas on how this theory might be used for geography education and research. By considering the limitations of the human mind, CLT offers geographers a way to assess critical components of the spatial learning processes. Methods for measuring cognitive load and reducing overloads are discussed within a map context. It is argued that managing the cognitive load experienced by learners is the key to representing geographic information.  相似文献   

A geophysical survey of the De Gerlache Seamounts: preliminary results     

Rick A. Hagen  Karsten Gohl  Rainer Gersonde  Gehard Kuhn  David Völker  V. N. Kodagali 《Geo-Marine Letters》1998,18(1):19-25

 The De Gerlache Seamounts actually consist of two medium-sized guyots, with summits at depths of 350–600 m. Acoustic profiler data show no significant sediment on these guyots. Alkaline basalts dredged from the summit of the eastern guyot yield K/Ar ages between 20.1±1.0 and 23.2±1.2 Ma. Basement ridges and sediment-filled troughs between the guyots are associated with the prominent gravity anomaly extending north from the Antarctic margin. This structure possibly played a role in the guyot formation, however, the question of how the De Gerlache Seamounts are related to this gravity anomaly remains uncertain. Received: 13 February 1997 / Revision received: 30 September 1997  相似文献   

A Reservoir–Geomechanical Model to Study the Likelihood of Tensile and Shear Failure in the Caprock of Weyburn CCS Project with Regard to Interpretation of Microseismic Data     

Cyrus Khazaei  Rick Chalaturnyk 《Geotechnical and Geological Engineering》2017,35(6):2571-2595

According to poroelastic theory and also field observations, an increase in reservoir pore pressures can result in a decrease in horizontal stresses in the seal layers. This reduction is in favor of hydrofracture initiation and reactivation of weak planes and has to be studied in caprock integrity analyses. In this paper, a field scale reservoir–geomechanical (GEM-FLAC3D) model is developed for the Phase IB area of the Weyburn (Canada) CCS project that is located in Williston sedimentary basin. A one-way coupling has been conducted between the two codes for the period of CO₂ injection in Phase IB area from 2000 to 2010. Therefore, the reservoir pore pressures at selected timesteps are unidirectionally fed to the FLAC3D. In order to study the likelihood of tensile and shear failure in the seal layer on top as a result of stress transfer due to poroelastic effects, two margin ratios are defined for tensile and shear failure and their variations are studied above the reservoir upon changes in pore pressures within the reservoir. The results show that overall; the likelihood of shear failure has been about 25% greater than that of tensile failure in Weyburn. However, between 2008 and 2009, the pressures were high enough to trigger both tensile and shear mechanisms above the reservoir. A discussion is also presented on relevance of this study for interpretation of microseismic data with regard to failure margin ratios, magnitudes and distribution of events recorded in each year.  相似文献