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101.
地理信息及其元数据标准化 总被引:29,自引:0,他引:29
通过对标准化历史的回顾,阐述了数据标准化在当今人类由工业社会向信息化社会迈进中的作用,并根据全球信息高速公路建设对地学研究的挑战,指出了信息化社会中数据标准对信息采集及信息共享的作用;依ISO/TC211对地理信息数据描述中元数据的建议,通过对ISO及CEN标准的分析,提出了建立我国元数据标准的基本思路,对我国地理信息标准化的建设具有重要意义。 相似文献
102.
Differences between statistical unertainty and modeling uncertainty are briefly discussed. It is pointed out that, when different models are proposed for the interpretation of reality, the uncertainty cannot be described in terms of mean value and coefficient of variation. The important question is: which of the proposed models is more reliable than the others? The attention, then, is concentrated on the comparison between different models proposed for the estimate of the required quantity, looking for a criterion leading to the selection of the most reliable one. A criterion for comparison of different models is suggested. In the example of application considered in this paper, it proved to be effective, so that the continuation of numerical experiments, exploring different and more complex situations, seems promising. 相似文献
103.
利用动测桩中的桩底反射信号研究了应力波在桩体和土体中的衰减情况。结果表明,应力波在桩体中的衰减比在土中小的多,在考虑了桩周土与反射系数的关系后,尝试给出应用桩底反射信号与桩头人射信号振幅之比判定单桩承载力相对大小的基本理论和初步研究结果。 相似文献
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地震前兆信息量的研究:(一)地震异常延续有效性的研究 总被引:2,自引:1,他引:1
根据我国大陆58个Ms≥5级地震的震列资料,详细地研究了地震异常延续有效时间与持续时间的相关关系,给出了由地震异常持续时间计算地震异常预测的有效时间(即地震异常延续有效时间的最优估值)的公式,经多种数理统计方法检验,证明这一公式是保信、可用的。这为进一步深入开发的震异常前兆信息量的研究奠定了基础,同时也为日常地震会商中常震确定地震异常延续有效性问题,提供了定量分析判定依据,因此本研究具有一定的实际 相似文献
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Elizabeth A. V. Mackie Jeremy M. Lloyd Melanie J. Leng Michael J. Bentley Carol Arrowsmith 《第四纪科学杂志》2007,22(6):579-591
Carbon isotopes (δ13C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea‐level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between δ13C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of δ13C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between δ13C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO2 concentration, poor vegetation development and temperature influence δ13C values during this period. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
109.
The first detailed investigation of a deep, coastal, sedimentary basin in Orkney reveals a complex Holocene history of back‐barrier morphodynamics. At Scapa Bay, the sea flooded a freshwater marsh after ca. 9400 yr BP at ca. ?5.4 m OD. Before ca. 7800 BP, abundant sediment from nearby cliffs was mobilised inland into a series of gravel barriers across the valley mouth. By ca. 7500 BP, direct marine influence was restricted in the back‐barrier area, although saltmarsh persisted until ca. 5900 BP. By then, at least four gravel ridges had enclosed the backing lagoon, where freshwater inputs became dominant. As terrestrial sediments filled the basin, another freshwater marsh developed. The multiple barrier complex demonstrates progradation resulting from continuous sediment supply in a sheltered embayment. The progressively rising height of the barrier crests seawards probably resulted from a combination of factors such as barrier morphodynamics, increased storminess and long‐term rising relative sea levels. The dominant vegetation surrounding Scapa Bay changed from open grassland to scrub ca. 9400 BP, then to deciduous woodland ca. 7800 BP, and to dwarf‐shrub heath ca. 2600 BP, the latter probably a response to a combination of climate change and human activity. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
110.
Gamma‐ray curves from surface outcrops together with U–Pb SHRIMP zircon dating are used to redefine the evolution of a Palaeoproterozoic sandy dolostone succession from northern Australia. This case history indicates that gamma‐ray logging of surface sections should accompany lithostratigraphic logging or an inadequate interpretation of stratigraphic evolution is a likely outcome. The 1200 m‐thick Nathan Group from the McArthur River area had previously been interpreted as a more‐or‐less continuous package of carbonates deposited in lacustrine and associated shallow‐water environments. Now it is seen to comprise the preserved remnants of three truncated, second‐order supersequences—the Lawn, Wide and Doom Supersequences—each a few hundred metres thick and each deposited over a time period of a few million years. These supersequences are separated by major stratigraphic breaks each approaching probably 10 million years duration. Each supersequence comprises several third‐order sequences which themselves contain higher‐order cycles. These were deposited in a series of continental, shoreline, and inner to outer carbonate platform environments. Transgressive, high‐energy, fluvial to marginal marine, mixed clastic‐carbonate facies dominate most of the sequences. The middle, Wide Supersequence, however, preserves deeper water (mostly sub‐storm‐wave‐base) stromatolitic facies in one sequence, and storm‐reworked clastics in another. These are interpreted as condensed intervals deposited around their respective maximum flooding surfaces and are succeeded by regressive facies that probably represent highstand systems tracts. New correlations between these 1615–1575 Ma sandy carbonate successions of the McArthur Basin (Amos, Balbirini and Dungaminnie Formations) and time‐equivalent largely clastic successions in the Lawn Hill area (Lawn Hill and Doomadgee Formations), some 400 km to the southeast, are proposed. 相似文献