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It has been asserted by Clough (1952) , amongst others, that British Military Survey was poorly prepared for the outbreak of war in 1939. An examination of the work carried out between the wars by the Air Survey Committee would seem to contradict that view. In this paper, the work of the Air Survey Committee is discussed and a brief assessment made of the impact of its work on British mapping during the Second World War. 相似文献
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正确认识和对待天气气候预报的不确定性 总被引:1,自引:2,他引:1
美国国家科学发展的指导机构同家研究顾问委员会(NRC)不久前发表了一份关于天气、气候和水文预报的不确定性的凋研报告.报告强调了预报不确定性信息在终端用户应用气象预报作决策中的重要性,同时指出一个预报如果没有定量地估计它的不确定性,那么该预报是不完全的.该报告中文版的出版工作正在进行中,现藉此机会向读者综合地介绍一下预报不确定性的问题.文中首先讨论了预报不确定性的缘由以及应该如何来科学地对待它.然后介绍了要应对这一问题所要进行的一些具体措施和策略.最后,简要地介绍了美国气象界为此所做的一些努力和计划以供参考.通过上述讨论和介绍,希望引起更多的人对预报不确定性问题的重视并科学应对以更好地服务社会. 相似文献
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Regional‐scale 40Ar–39Ar data presented in this paper reveal significant across‐strike and along‐strike age differences in the Committee Bay belt (CBb), Rae Province, Nunavut, Canada, that complement variations in observed monazite ages. 40Ar–39Ar hornblende ages are c. 1795, 1775, and 1750 Ma in the western, eastern and central parts of the Prince Albert Group (PAG) domain respectively. The migmatite domain and Walker Lake intrusive complex are characterized by c. 1750–1730 40Ar–39Ar hornblende ages without significant along‐strike variation. The 40Ar–39Ar data provide important constraints on the cooling history and on thermal modelling that elucidates the controls on diachroneity and metamorphic patterns within the belt. In the western CBb, prograde monazite growth occurred 26 ± 10 Myr earlier in the migmatite domain (1864 ± 9 Ma; peak P–T = 5 kbar?700 °C) than in the PAG domain (1838 ± 5 Ma; peak P–T = 5 kbar?580 °C). Calculations indicate that this earlier monazite growth results from tectonic thickening of higher heat productivity Archean lithologies in the migmatite domain, which undergoes more rapid prograde heating than the less radiogenetic and lower grade rocks of the PAG domain. Granite generation via biotite dehydration melting at 800 °C and 20 km depth is predicted to occur c. 1835 Ma, in agreement with geochronological constraints. The tectonic burial of crustal domains with contrasting radiogenic properties also explains the general congruence of lower to upper amphibolite facies metamorphic zones generated during the two main orogenic cycles (i.e. M2–D1 and M3–D2). The modelled timing of prograde monazite growth in the migmatite domain suggests that D2 tectonic thickening began at 1872 ± 9 Ma, some 8 ± 3 Myr before monzazite growth, coeval with the inferred time of collision of the Meta Incognita terrane with the southern Rae Province. Along‐strike diachroneity, reflected in 25 Myr younger monazite and 40Ar–39Ar hornblende ages in the eastern relative to the western PAG domain, cannot be accounted for by heat productivity contrasts along the belt. Instead the younger deformation and metamorphism in the eastern CBb was driven by its proximity to the eastern promontory of the Superior Province which collided with the Rae Province at c. 1820 Ma. The 40Ar–39Ar data presented here support the interpretation that the youngest monazite in the CBb crystallized at c. 1790 Ma in the central CBb when this part of the belt was downfolded into a gentle synformal structure while the western part of the belt cooled through 40Ar–39Ar hornblende closure. The results of this study illustrate the important influence of contrasting rock properties on the thermal evolution of orogenic belts and on the temporal record of this evolution. 相似文献
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在国际金融界享有盛誉的巴塞尔委员会近期发布的<信用风险管理原则>,对银行信贷资产的风险管理做出了全面的规定,内容包括风险战略、授信、风险监测、风险控制、风险的外部监管等很多方面,对我国都有很强的借鉴性.我国商业银行目前贷款经营管理水平较低,金融信贷管理法规有的地方已不适应形势需要.因而,有必要吸收借鉴该文件的精神并加以创新,建立有我国特色的完善的信贷风险法规体系. 相似文献
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对中国地震预测咨询委员会2004-2014这10年历年集体会商并上报中国地震局和全国会商会的书面预测意见做一回顾总结(重点是7级和7级以上地震),以作为今后预测工作的参考。 相似文献