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在2004年10月2日，圣海伦斯火山（MountSt．Helens）断断续续地释放了整整一中午的蒸汽；随之而来的是近1小时的低频地震。岩浆似乎正在地下涌动。由于担心即将来临的火山喷发威胁人类生命，位于华盛顿州西南的喀斯喀特火山观测站（Cascades Volcano Observatory）的科学家们发布了3级火山警报，航空代码为红色。第二天，联邦航空局（FAA）在火山周围5．5英里内实行了禁航，要求航班改变航线或是推迟起飞。两三天后，这些警报似乎得到了证实，火山喷发产生的火山灰形成了遮天蔽日的尘雾，一直向东北方向绵延70英里。 相似文献
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火山往往呈灾难性事件喷发,对它还不能作出预报.我们对火山现象的了解和认识是广泛的,但还不能进行详细的预测.火山预报仍处于初期阶段.人们从火山方面得到好处,而且学会了在火山附近生活.现在人们需要从科学方面来对待火山,应该对它们大部分活动过程进行监测.需要搜集多次喷发期间的资料,作为建立物理和化学模型的基础.为此,世界上许多地方已经和正在建立火山观测站. 相似文献
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准确的预报是降低火山灾害造成的损失的重要前提。但是,由于火山喷发活动周期较长引发的原因多种多样,我们目前对火山喷发的预报还处于探索阶段,非常不精确。不过随着一些新的预测方法不断出现，我们将能够逐步提高火山喷发预报的准确性。 相似文献
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火山喷发是一种突发性自然现象,而近几年全球气候异常变化.世界各地火山、地震等地质灾害此起彼伏,严重威胁了人类的生命和财产安全.阐述用3S技术对活火山监测的研究.根据火山喷发在陆地卫星TM影像上的特征,通过不同时相TM影像叠加,目视解译确定火山是否在活动,为火山区减灾、防灾和合理规划经济布局服务. 相似文献
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火山是地下炽热的岩浆上升到地表后冷却堆积所形成的地质体。火山喷发既可以给人类带来巨大的经济效益,也可以给人类带来巨大的灾难。火山灾害作为自然界最严重的自然灾害之一,还可以对人类的生存产生极大影响。例如1783年冰岛拉基火山喷发, 相似文献
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《大科技．科学之谜》2015,(6)
<正>如果地球上的火山一齐喷发,将会怎么样?粗略估计地球上有1500座活火山,其中包括地表的活火山,以及隐藏在海底深处的火山。如果这1500座火山同时喷发,会是怎样的情况呢?首先,火山喷发之后,厚厚的火山灰将笼罩地球,地球进入黑暗之中,地球上大多数生物由于失去阳光的普照,而面临灭绝的风险。这些火山灰至少要在大气中停留10年左右才会消失。尽管不是地球上所有的火山喷发都会喷出火山灰,比如夏威夷群岛的火山通常只产生少量的熔岩,但是也别忘了,这些活火山中还包括一些火山大佬,比如黄石国家公园那座超级火山。如果这座火山喷发,那将会给美国的天空铺上一层厚厚的火山灰。紧跟着火山灰的脚步而来的是严寒。火山 相似文献
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针对电喷发动机产生的积碳现象,先从电喷发动机产生积碳的外部特征、引起的原因、造成的危害、预防的措施几个方面分析故障现象的成因与应对方法,从而达到排除故障的目的。 相似文献
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R.S.J Sparks 《Endeavour》1979,3(1):27-31
In the late Bronze Age, sometime between 1500 and 1450 BC, a paroxysmal explosive eruption of the volcano Santorini took place in the Aegean Sea. Many scientists now link the rapid decline of the Minoan Civilisation centred on Crete with the destructive effects of this catastrophic eruption. The geological record indicates that one or two eruptions of comparable magnitude may occur every 1000 years. In our present-day world with its rapidly expanding population and economy the catastrophic effects of such an eruption occurring today should be seriously considered. 相似文献
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Christos Doumas 《Endeavour》1983,7(3):144-149
The abrupt decline of the Minoan civilisation in Crete between 1500 and 1450 BC has been linked with the consequences of an exceptionally violent eruption of the volcano Santorini. This article reviews this, and other theories, in the light of archaeological evidence acquired in the course of excavations at Thera during the past fifteen years. 相似文献
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Dörries M 《Endeavour》2003,27(3):113-116
The eruption of the volcano Krakatau in the Netherlands East Indies (Indonesia) in 1883 had worldwide impact. This was perceived in the three quite different types of global propagation that occurred after the eruption: a rapid pressure wave, noticeable only to measuring instruments, followed a few hours later by the spread of the news of the event, succeeded by a slowly expanding optical phenomenon that lasted for a couple of years. Krakatau was the first natural catastrophe of global magnitude that was almost immediately recognized as such throughout the world, largely thanks to the recently installed worldwide telegraphic network. 相似文献
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才艳华 《科技成果管理与研究》2010,(7):75-77
本文通过室内物模实验和数值模拟研究,论证了蒸汽吞吐采油技术在低渗透油藏的可行性,对油层组合和注汽参数进行了优化设计,研究了注汽过程中的隔热和防止粘土膨胀配套技术。在此基础上,首次在低渗透油田二类区块2口井进行了两个周期的蒸汽吞吐采油现场试验,取得了较好增油效果,单井产液量和产油量增加,改善了油层动用状况,降低了原油粘度,提高了原油流动性。 相似文献
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中小企业问题是一个世界性的课题,也是一个永久性的课题。因此,能否准确、恰当界定中小企业．无论对于理论界还是实务界都具有非常重要的意义。本文从定性和定量两个方面分析、比较和评价了国内外对于中小企业界定的最新标准,并对我国现行中小企业界定标准存在的问题以及如何将进一步规范化和定量化做了详尽地探讨。 相似文献
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David S. Ross 《Journal of The Franklin Institute》2010,347(7):1281-1308
If a circle in the plane is to roll along a track so that a given point on the circle traces out another circle, what must the shape of the track be? In this paper we give a full answer to this question. This question arises in the design of internal combustion engines and other machines. It is a sort of inverse problem to the classical problem of the trajectories of points on circles rolling inside other circles; the problem whose solution is hypocycloids and hypotrochoids. We derive a system of nonlinear differential equations for the coordinates of the track regarded as a parametric curve. We express the solution of this differential equation in terms of an elliptic integral. We establish the uniqueness of this solution for a given choice of the relevant parameters, the radius of the circle to be traced out and the location on the rolling circle of the tracing point. We show that if we allow the rolling circle to intersect the track, there is at least one track for any circle. We find all possible tracks, and we derive formulas to determine, for a given radius of the circle to be traced out, how many different tracks produce circles of that radius; there is always a finite number, and the number increases roughly linearly with the radius. We characterize those tracks that are mathematical solutions but are not practical physical solutions; tracks that the rolling circle intersects in such a way that it would get stuck. 相似文献
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Fyfe A 《Endeavour》2006,30(4):120-125
With the arrival of steam power and new machinery in the 19th century, the production of printed media was transformed for the first time since the emergence of the printing press more than 300 years earlier. Yet until the 1850s, most publishers remained content with traditional methods, which enabled them to make profits from a small but affluent circle of readers. This article (part of the Science in the Industrial Revolution series) will show how William Chambers (1800-1883) was one of the first to make full use of the new technologies. He was driven by a determination to reach readers of all social classes, to produce a genuinely cheap instructive publication and to overcome the challenges of reaching a national market from his base in Edinburgh. 相似文献
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李作学 《科技成果管理与研究》2010,(10):55-57
为及时了解齐40块65井组汽驱开发进展情况,提高井组汽驱效果,对齐40块65井组10个井组进行汽驱前缘微地震监测。通过监测分析汽驱井组问蒸汽腔及蒸汽通道发展情况,确定汽驱优势方向及蒸汽波及范围,实现对汽驱井组开发动态实时跟踪评价,为下步动态调整提供依据。 相似文献