Correspondence     

K. B. Atkinson 《The Photogrammetric Record》2006,21(115):296-297

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Ecosystem modelling in the southern Benguela: comparisons of Atlantis,Ecopath with Ecosim,and OSMOSE under fishing scenarios     

MD Smith  EA Fulton  RW Day  LJ Shannon  Y-J Shin 《African Journal of Marine Science》2015,37(1):65-78

Ecosystem-based management of marine fisheries requires the use of simulation modelling to investigate the system-level impact of candidate fisheries management strategies. However, testing of fundamental assumptions such as system structure or process formulations is rarely done. In this study, we compare the output of three different ecosystem models (Atlantis, Ecopath with Ecosim, and OSMOSE) applied to the same ecosystem (the southern Benguela), to explore which ecosystem effects of fishing are most sensitive to model uncertainty. We subjected the models to two contrasting fishing pressure scenarios, applying high fishing pressure to either small pelagic fish or to adult hake. We compared the resulting model behaviour at a system level, and also at the level of model groups. We analysed the outputs in terms of various commonly used ecosystem indicators, and found some similarities in the overall behaviour of the models, despite major differences in model formulation and assumptions. Direction of change in system-level indicators was consistent for all models under the hake pressure scenario, although discrepancies emerged under the small-pelagic-fish scenario. Studying biomass response of individual model groups was key to understanding more integrated system-level metrics. All three models are based on existing knowledge of the system, and the convergence of model results increases confidence in the robustness of the model outputs. Points of divergence in the model results suggest important areas of future study. The use of feeding guilds to provide indicators for fish species at an aggregated level was explored, and proved to be an interesting alternative to aggregation by trophic level.  相似文献   

A systematic review of landslide probability mapping using logistic regression   总被引：2，自引：0，他引：2  

M. E. A. Budimir  P. M. Atkinson  H. G. Lewis 《Landslides》2015,12(3):419-436

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On the use of the stress relaxation testing method in studies of the mechanical behaviour of geological materials     

E. H. Rutter  B. K. Atkinson  D. H. Mainprice 《Geophysical Journal International》1978,55(1):155-170

Summary. A summary is presented of the use of stress relaxation testing in studies of the mechanical behaviour of materials with emphasis on the underlying assumptions of the method. It is shown that relaxation testing is a powerful experimental method which could profitably be used in future studies of the mechanical properties of geological materials to augment, but not to replace, the more conventional creep and constant strain rate tests.
Stress relaxation data can be analysed to determine important parameters in equations describing (a) laws of flow and fracture, and (b) dislocation dynamics. The variation of the first derivative of any stress relaxation curve with stress can be used to establish the applied stress sensitivity to strain rate and the values of activation parameters such as 'activation volume'. Such parameters may be used to constrain the inference of the dominant deformation mechanism. This account is illustrated by reference to some recent experiments on polycrystalline, synthetic galena (lead sulphide) and pre-faulted cylinders of Tennessee sandstone deformed over a wide range of environmental conditions. The accurate sensing of the second derivative of a relaxation curve is required to establish parameters relating to dislocation dynamics, e.g. partition between thermal and athermal components of applied stress, and the stress dependence of dislocation velocity. The determination of such parameters is illustrated with new experiments on single crystals of calcite.  相似文献   

A comparison of gauge and radar precipitation data for simulating an extreme hydrological event in the Severn Uplands,UK     

Eloise M. Biggs  Peter M. Atkinson 《水文研究》2011,25(5):795-810

This paper provides a comparison of gauge and radar precipitation data sources during an extreme hydrological event. November–December 2006 was selected as a time period of intense rainfall and large river flows for the Severn Uplands, an upland catchment in the United Kingdom. A comparison between gauge and radar precipitation time‐series records for the event indicated discrepancies between data sources, particularly in areas of higher elevation. The HEC‐HMS rainfall‐runoff model was selected to assess the accuracy of the precipitation to simulate river flows for the extreme event. Gauge, radar and gauge‐corrected radar rainfall were used as model inputs. Universal cokriging was used to geostatistically interpolate gauge data with radar and elevation data as covariates. This interpolated layer was used to calculate the mean‐field bias and correct the radar composites. Results indicated that gauge‐ and gauge‐corrected radar‐driven models replicated flows adequately for the extreme event. Gauge‐corrected flow predictions produced an increase in flow prediction accuracy when compared with the raw radar, yet predictions were comparative in accuracy to those using the interpolated gauge network. Subsequent investigations suggested this was due to an adequate spatial and temporal resolution of the precipitation gauge network within the Severn Uplands. Results suggested that the six rain gauges could adequately represent precipitation variability of the Severn Uplands to predict flows at an approximately equal accuracy to that obtained by radar. Temporally, radar produced an increase in flow prediction accuracy in mountainous reaches once the gauge time step was in excessive of an hourly interval. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Surface geochemistry at Roosevelt Springs Kgra, Utah     

J.S. Lovell  W.T. Meyer  D. Atkinson 《Journal of Geochemical Exploration》1983,19(1-3)

As part of a research program conducted on behalf of the Department of Energy, available data on the Roosevelt Springs KGRA were synthesized to determine the spatial arrangement of the rocks, and the patterns of mass and energy flow within them. The resulting model led to a new interpretation of the geothermal system, and provided “ground truth” for evaluating the application of soil geochemistry to exploration for concealed geothermal fields. Preliminary geochemical studies comparing the surface micro-layer to conventional soil sampling methods indicated both practical and chemical advantages for the surface micro-layer technique.The elements arsenic, antimony and cesium in the surface microlayer samples in particular, gave a strong expression of one of the principal faults in the geothermal field. In contrast the analysis of soil samples from only 20 cm below the surface gave little or no expression of the geothermal field.As a consequence, the surface micro-layer was the chosen sampling medium for the second field program, which entailed the collection of a total of some 300 samples on both a regional and detailed pattern covering about 250 km². These samples were subsequently analyzed by a variety of methods yielding data on 41 elements and ions.Computer contouring revealed that, on a single-element basis, cesium, antimony and arsenic provided the best expression of the KGRA, and indicated other interesting areas of geothermal leakage. Elements such as beryllium and lithium, which are present in highly anomalous concentrations in the opaline sinter deposited by geothermal leakage, do not have an expression in the overlying soils or the surface micro-layer. Computer manipulation of the multi-element data using R-mode factor analysis provided the optimum method of interpretation of the surface micro-layer data. A single factor in which the principal contributors were arsenic, antimony and cesium provided the best indication of the leakage of geothermal solutions within the KGRA. Anomalies in the Escalante Desert to the west of the geothermal field are associated with the trace of a fault zone, and may, therefore, be an activity. Trend surface analysis of the soil mercury data has indicated a regional high in this element in the Mineral Mountains to the east of the KGRA, which may indicate the position of a dry heat source at depth.These data demonstrate that surface micro-layer sampling on a regional scale can serve as a prospecting tool for geothermal resource areas. However, it is possible that the optimum pathfinder elements may vary with the nature of heat source, the geochemistry of the local rocks and the local surficial environment. It is therefore recommended that a multi-element approach should be adopted, with subsequent computer processing of the data.  相似文献   

Proble´mes pratiques de me´canique des sols et de fondations | G. Sanglerat,G. Olivari and B. Cambou. Dunod,Paris, 1980. Vol. 1: 328 pp.; Vol. 2: 232 pp     

J.H. Atkinson 《Engineering Geology》1983,19(3):242-243

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Uncharged condensation nuclei produced by ultra-violet light     

J. R. Atkinson 《Pure and Applied Geophysics》1955,31(1):54-59

Summary A large number of experiments have been carried out with the object of determining the nature, properties and source of the condensation nuclei produced by the action of a beam of ultra-violet light within an expansion chamber. This paper is essentially a qualitative summary of the results which have been obtained. It is concluded that these experiments show that it is the rubber component of the chambers that has been responsible for the major part of the effect. It is by no means suggested that this is the only source of the nuclei, but it is implied that only apparatus free from rubber should be used in any study of the properties of the nuclei associated with a given gas or vapour.Work ofA. J. Barnard (now at University of Natal, Pietermaritzburg) andJ. R. Atkinson.  相似文献   

Machine vision for dimensional measurements in mines     

R. Singh  D. P. Chapman  K. B. Atkinson 《Geotechnical and Geological Engineering》1997,15(3):185-203

Summary Fast growing mechanization and automation in the mining industry has been adopted to increase production, productivity and safety, but it requires quick, precise and automatic measurements. In particular, the measurement of deformations around a coal-mining face has been an extremely difficult task due to the time and space constraints of such sites. In a continuing drive to reduce the inherent risks of danger during working around such difficult areas, much routine inspection work is increasingly being undertaken by remote measuring systems. The advent of digital photogrammetry provides an opportunity for real-time dimensional measurement of such inaccessible areas. In this paper, some examples of reliability testing of automatic measurements using grey scale digital images of mining structures is described. A CCD (charged coupled device) based active triangulation system is combined with image understanding algorithms to provide machine vision capability and for automatic measurement of the textureless and featureless surface of sandstone strata. This paper also presents some results of initial laboratory investigations conducted to test the reliability of basic components of the system.  相似文献   

Population biology of the Norway lobster, Nephrops norvegicus (L.) in the Firth of Clyde, Scotland - I: Growth and density     

Tuck  I. D.; Chapman  C. J.; Atkinson  R. J. A. 《ICES Journal of Marine Science》1997,54(1):125-135

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