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Abstract This paper describes a generic structure model for large numbers of spatially-related images held within a multi-media information system. Applications vary from multi-scale map tilings underlying geographical information system user interfaces to sets of spatially-related visual data held in image form, such as ‘structured walks’ and sets of views with finder maps. The model enables an abstract structure to be soft-configured onto any indexed collection of images and related to standard databases of textual and graphical information at various levels. This is achieved by defining a number of customized ‘image structures’ and providing techniques for their manipulation. Key features of the model are defined in VDM-SL, a formal specification language being standardized by the International Organization for Standardization. The formal definitions are accompanied by explanations in English and by examples. Prototype implementations are described. A glossary of symbols, terms and expressions is given in the Appendix. 相似文献
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CLIVE POTTER 《The Geographical journal》2006,172(3):190-196
Whatever their eventual outcome, the current round of international trade negotiations taking place as part of the Doha Development Round offers a clear demonstration of the growing influence of a neoliberal agenda for international agricultural policy reform. Despite being powerfully supported by an alliance of agribusiness interests and country groupings, neoliberalism is far from universally accepted as the model for the future governance of an agriculture which is both commodifying and market led. This paper assesses the nature of the resulting debate and the range of alternative visions being proposed. It analyses the development of the European negotiating stance within the current round of trade talks and compares the merits of a decoupled policy approach to managing the rural environment with one much more closely linked to the practice of farming. The paper concludes by suggesting that an outcome of the continuing liberalization of agricultural policy will be a more demarcated countryside, in which productive and internationally competitive operators will increasingly be removed in space and in terms of policy treatment from the large number of economically marginal producers whose role will be to supply the public environmental goods under contract from the state. 相似文献
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CLIVE OPPENHEIMER 《Geology Today》1993,9(2):66-68
The highest working mines in the world extract bright yellow deposits of sulphur from the peaks of towering volcanoes in the Central Andes. Workers and machinery must cope with the extreme environment at up to 6000 metres above sea level. 相似文献
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The Darlington (Sakmarian) and Berriedale (Artinskian) Limestones are neritic deposits that accumulated in high‐latitude environments along the south‐eastern margin of Pangea in what is now Tasmania. These rocks underwent a series of diagenetic processes that began in the marine palaeoenvironment, continued during rapid burial and were profoundly modified by alteration associated with the intrusion of Mesozoic igneous rocks. Marine diagenesis was important but contradictory; although dissolution took place, there was also coeval precipitation of fibrous calcite cement, phosphate and glauconite, as well as calcitization of aragonite shells. These processes are interpreted as having been promoted by mixing of shelf and upwelling deep ocean waters and enabled by microbial degradation of organic matter. In contrast to warm‐water carbonates where meteoric diagenesis is important, the Darlington and Berriedale Limestones were largely unaffected by meteoric diagenesis. Only minor dissolution and local cementation took place in this diagenetic environment, although mechanical compaction was ubiquitous. Correlation with burial history curves indicates that chemical compaction became important as burial depths exceeded 150 m, promoting precipitation of extensive ferroan calcite. This effect resulted from burial by rapidly deposited, overlying, thick, late Permian and Triassic terrestrial sediments. This diagenetic pathway was, however, complicated by the subsequent intrusion of massive Mesozoic diabases and associated silicifying diagenetic fluids. Finally, fractures most probably connected with Cretaceous uplift were filled with late‐stage non‐ferroan calcite cement. This study suggests that both carbonate dissolution and precipitation occur in high‐latitude marine palaeoenvironments and, therefore, the cold‐water diagenetic realm is not always destructive in terms of diagenesis. Furthermore, it appears that for the early Permian of southern Pangea at least, there was no real difference in the diagenetic pathways taken by cool‐water and cold‐water carbonates. 相似文献
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The Origin and Composition of Metasomatic Fluids and Amphiboles beneath Malaita, Solomon Islands 总被引：3，自引：2，他引：3
A suite of mantle peridotite xenoliths from the Malaitan alnoitedisplay both trace element enrichment and modal metasomatism.Pargasitic amphibole is present in both garnet- and spinelbearingxenoliths, formed by reaction of a metasomatic fluid (representedby H2O and Na2O) with the peridotite assemblage. Two pargasite-formingreactions are postulated, whereby spinel is totally consumed: 6MgAl2O4 + 8CaMgSi2O6 + 7Mg2Si2O6 + 4H2O + 2Na2O = 4NaCa2Mg4Al3Si6O12(OH)2+ 6Mg2SiO4 or spinel is both a reactant (low Cr) and a product (high Cr): 24MgAlCrO4 + 16CaMgSi2O6 + 14Mg2Si2O6 + 8H2O + 4Na2O = 8NaCa2Mg4Al3Si6O12(OH)2+ 12MgCr2O4 + 12Mg2SiO4 Seven garnet—spinel-peridotites display cryptic metasomatismas demonstrated by the LREE enrichment in clinopyroxenes. TheLREE enrichment correlates positively with 143ND/144ND (0?512771–0?513093)which defines a mixing line between a mantle MORB source anda metasomatic fluid. Isotopic evidence (Sr and Nd) from garnet,clinopyroxene, and amphibole demonstrate this fluid has notoriginated in the alnoite sensu stricto. Calculated amphiboleequilibrium liquids show a range in La/Yb and Ce/Yb ratios similarto those calculated for the augite and subcalcic diopside megacrysts.Sr and Nd isotope analyses from amphibole are within error ofthe augite (PHN4074) and subcalcic diopside megacrysts (CRN2I6,PHN4069, and PHN4085). It is concluded that fluids emanatedfrom a proto-alnoite magma throughout megacryst fractionation,and the mixing line was generated during the crystallizationof the subcalcic diopsides. This study demonstrates that metasomatismrepresented in these xenoliths is not a prerequisite for alnoitemagmatism, but is a consequence of it. 相似文献
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CLIVE OPPENHEIMER 《Geology Today》1991,7(1):19-23
Many of the world's most dangerous volcanoes are located in developing countries, which often lack resources for adequate hazard mitigation efforts. Despite technological advances in volcano monitoring, the increasing populations that crowd fertile ash slopes exacerbate the threat of future major volcanic disasters. 相似文献
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CLIVE PORTMAN JULIAN E. ANDREWS PETER J. ROWE MICHAEL R. LEEDER JURIAN HOOGEWERFF† 《Sedimentology》2005,52(3):441-465
The cyanobacterium Rivularia haematites has calcified to form unusually large (up to 10 m high) bioherms in the Pleistocene Gulf of Corinth. Today R. haematites calcifies only in freshwater environments but these Gulf of Corinth bioherms have a brackish affinity, limited areal extent, and occur within marine deposits. Field relations and preliminary U-series dating suggest a marine isotope stage (MIS) 5e age for the bioherms. This age is compatible with published MIS 5e ages for corals in the marine sediments above the bioherms and is consistent with their current elevation based on average uplift rates. Bioherm growth during MIS 5e constrains their formation during a time of near sea-level highstand when the Gulf of Corinth was marine. Growth cavities in the bioherms are encrusted by brackish tolerant coralline algae. Field mapping of the MIS 5e highstand palaeoshoreline shows the bioherms grew in water <16 m deep. Mg contents of the bioherm calcites, and associated coralline algal skeletons, are both much lower than expected for marine MIS 5e carbonates. They are best explained if the calcites precipitated from brackish fluids with Mg/Ca ratios below 2, implying at least 60% input of freshwater with low Mg/Ca ratio. Sr isotopes confirm a strong input of groundwater that had partially equilibrated with Mesozoic limestones. The limited areal extent of the bioherms and their close association with karstified fault scarps suggest that they formed in shallow sea water where freshwater submarine springs delivered CaCO3 saturated water that promoted rapid calcification of cyanobacteria. Rapid calcification and strong degassing of CO2 from the spring water resulted in disequilibrium stable isotope compositions for the calcites. 相似文献
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