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71.
Montegriffo Bellazzini Ferraro Martins Sarajedini & Fusi Pecci 《Monthly notices of the Royal Astronomical Society》1998,294(2):315-326
We present deep V - and I -band CCD photometry of the globular cluster Terzan 8, recently found to be a member of the globular cluster system of the Sagittarius dwarf spheroidal galaxy. We accurately estimate the metallicity of Terzan 8, and provide the first direct determination of the colour excess toward this cluster. Our robust age estimate confirms that this cluster is indeed coeval with typical Galactic globulars of comparable metal content, and thus it is probably significantly older than at least two other Sagittarius clusters, Terzan 7 and Arp 2. The implications of this result on the star formation history of the Sagittarius galaxy are briefly discussed. 相似文献
72.
分析印度板块与欧亚板块俯冲带、尼泊尔Ms8.1地震震中区地震构造及地震发震构造,讨论主震对余震触发及余震的时空强特征和地震对周边地区地震活动趋势的影响。初步分析认为,主边界断裂为本次地震的发震构造,属于低角度逆冲断层地震;余震分布范围与震源破裂面积和方式基本一致,具有向东迁移的时空特征;西藏定日Ms5.9、聂拉木Ms5.3地震不属于尼泊尔地震余震,是应力扰动的结果;沿俯冲带向东至喜马拉雅东构造结是大震发生的危险地段。 相似文献
73.
Evidence from the Trent terrace archive, Lincolnshire, UK, for lowland glaciation of Britain during the Middle and Late Pleistocene 总被引:1,自引:1,他引:0
Tom S. White Andy J. Howard 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):141-153
The late Middle Pleistocene fluvial terrace sequence of the lower Trent system, Lincolnshire (eastern England), provides an excellent record of environmental change, including evidence for the last two interglacial episodes. It also provides important stratigraphical evidence for the timing and extent of three separate glaciations. Two of these, the Anglian and Devensian, are well-established correlatives of Marine Isotope Stages (MIS) 12 and 2 respectively; the third is a hitherto un-named post-Anglian-pre-Devensian glaciation in eastern England that has been the subject of much previous speculation, but can now be attributed with some confidence to MIS 8. Crucially, the recognition of MIS 7 interglacial deposits within the Balderton-Southrey terrace of the proto-Trent indicates that the underlying Wragby Till, which is ascribed to this additional glaciation, was emplaced no later than MIS 8. The oldest terrace preserved within the lower Trent staircase, the Eagle Moor-Martin Terrace, is considered to be a complex glacial outwash terrace related to the Wragby Till glaciation. It is suggested that deposits representing MIS 11-9, which are conspicuously absent throughout the Trent system, were removed by this glaciation. This is a departure from previous interpretations, which have suggested MIS 10 or MIS 6 as the most likely stages in which an extensive post-Anglian-pre-Devensian lowland glaciation might have occurred in Britain. However, the widespread preservation of undisrupted post-MIS 8 fluvial sequences throughout the Trent valley and in neighbouring systems, within which MIS 7 interglacial deposits have now been recognized at a number of localities, indicates that ice sheets are unlikely to have advanced further into this catchment during MIS 6 than during the Devensian (MIS 2). Recognition of a British glaciation during MIS 8 corresponds with widespread evidence in Europe, which suggests that glacial deposits classified as ‘Saalian’ represent both MIS 8 and MIS 6; in many areas, distinguishing these remains controversial, as confident correlation with either stage is often only possible where glacial sediments interdigitate with well-constrained fluvial records. 相似文献
74.
添加剂对KAlSi_3O_8-CaSO_4-CaCO_3体系反应表观活化能的影响 总被引:2,自引:0,他引:2
首先测定了KAlSi3O8-CaSO4-CaCO3体系在不同焙烧条件下钾长石转化成可溶性氧化钾的转化率,进而通过模拟计算表明:KAlSi3O8-CaSO4-CaCO3体系的固相扩散动力学过程符合金斯特林格动力学方程,反应表观活化能Ea为128.92kJ/mol。并着重考察了4种添加剂Na2SO4、Na2SO3、NaCl和NaF对KAlSi3O8-CaSO4-CaCO3体系的影响,结果表明:向体系中分别加入占反应物总质量3%的Na2SO4、Na2SO3、NaCl和1%的NaF后,体系的反应表观活化能Ea从原来的128.92kJ/mol依次下降至87.15、98.71、117.38和126.14kJ/mol,这表明4种添加剂中Na2SO4的效果最好,它能较大程度上降低反应表观活化能,从而降低反应温度和提高固相反应速率。 相似文献
75.
76.
根据地震震源机制、断层参数结果,结合GPS测定的同震位移场与构造研究的最新结果,综合分析研究了2008年汶川8级大地震汶川地震发生的地震活动背景、震源应力场、断层构造运动特征及其动力学机制。地震活动性分析研究结果表明,2008年汶川8级大地震是在青藏高原与其周边地域构造运动剧烈,2001年起始的地震活动高潮期的背景下发生的。其长达300km的地震震源断层填补了青藏高原东缘1900年以来存在的8级地震活动的空区。震源机制与区域应力场特征及其动力学机制研究表明,汶川8级地震震源处于南北地震带中南段东部,青藏高原东向扩张与四川盆地的抵抗是该区构造运动的主要特征。汶川地震及其强余震是在一个稳定的、主压应力P轴以北西西-东南东方向为主的震源应力场控制下发生的。说明汶川地震震源区域主要受到四川盆地、华南块体区域应力场的控制并发震的。龙门山断裂带西侧的青藏高原相对于四川盆地发生的东向上升;而东侧的四川盆地相对于青藏高原发生的西向下降构造运动是2008年汶川8级地震发生的主要地震成因即地震发生机制。 相似文献
77.
78.
????2013????5.1?????????????????????????????????????????????仯??????????????????????????Ч???????????????????????????????й?????????з???????????????????????????淢????????????????????????????????????????й??????????????????????????????????Ms5.1?????????????????????????????????????????????????????????????????????????淢???????????γ?????????????????????????????????????????????????桢???????????????????μ???????????--???????????????? 相似文献
79.
Land cover classification of finer resolution remote sensing data is always difficult to acquire high-frequency time series data which contains temporal features for improving classification accuracy. This paper proposed a method of land cover classification with finer resolution remote sensing data integrating temporal features extracted from time series coarser resolution data. The coarser resolution vegetation index data is first fused with finer resolution data to obtain time series finer resolution data. Temporal features are extracted from the fused data and added to improve classification accuracy. The result indicates that temporal features extracted from coarser resolution data have significant effect on improving classification accuracy of finer resolution data, especially for vegetation types. The overall classification accuracy is significantly improved approximately 4% from 90.4% to 94.6% and 89.0% to 93.7% for using Landsat 8 and Landsat 5 data, respectively. The user and producer accuracies for all land cover types have been improved. 相似文献
80.
通过岩心观察并充分利用普通薄片、铸体薄片、阴极发光、X-衍射和扫描电镜等资料,对姬塬地区长8油层组储层的成岩作用、成岩矿物、成岩阶段和成岩演化序列特征等进行了研究。根据成岩作用类型及强度、成岩矿物等将储层划分为绿泥石衬边弱溶蚀、不稳定组分溶蚀、压实致密、高岭石充填和碳酸盐胶结5种成岩相。并通过岩心薄片资料刻度测井归纳出不同成岩相在GR、AC等测井曲线及其组合上的响应特征,由此实现各单井储层成岩相的连续划分。对长8油层组层序界面和基准面旋回与成岩相展布的关系进行了研究,结果表明层序界面附近不稳定组分溶蚀相及高岭石充填相较为发育,且各井之间对比性良好,同时层序界面也控制了碳酸盐胶结;中期基准面旋回的最大湖泛面处均发育井间可对比的压实致密相,长82中期基准面下降半旋回砂体一方面易于遭受溶蚀产生次生孔,另一方面由于受沉积驻留和碎屑组分影响导致压实强度较弱,因此物性总体比长81砂体好。 相似文献