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101.
1 .Introduction Submarine pipelines are one of the safest and the least environmentally disruptive means for ma-rine gas or oil transport . With the development of exploitation of submarine oil or gas ,the safety ofsubmarine pipelines has becomethe major … 相似文献
102.
华北地区夏季降雨量与南海海温长期变化的关系 总被引:6,自引:0,他引:6
比较了华北地区7个站与17个站1951-1997年夏季(6,7,8月)降雨量与气候随时间的变化特征,并对其成因作了探讨。结果表明,用北京、天津、邢台、烟台、郑州、太原和济南等7个站可代表该地区夏季降雨量与气候的多尺度变化特征,过去47a该地区依次经历了湿凉、湿热、湿凉、干热、湿热几个时期,降雨量的长期变化与南海前冬(1-2月)海温成负相关。前冬南海海温偏高,意味着初夏南海地区大气对流低频振动偏弱,南海夏季风爆发较晚,西南季风较弱,夏季西太平洋副高位置偏南,华北地区大气低层北风加强,华北地区夏季少雨,前冬南海海温偏低时情况则相反,考虑冬季(1-2月)南海南温和7-8月西太平洋副高脊线位置(纬度)的影响用均生函数建模,试验结果与用子波变换重构方法考虑华北地区夏季降雨量的变化趋势比较,二者相吻合,预测试验结果与过去3a的实况基本一致。 相似文献
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H. Hummel C. Amiard-Triquet G. Bachelet M. Desprez J. Marchand B. Sylvand J.C. Amiard H. Rybarczyk R.H. Bogaards J. Sinke Y. De Wit L. De Wolf 《Journal of Sea Research》1996,35(4):315-321
Variation in the sensitivity to stress of Macoma balthica was measured in several French and Dutch estuaries. For adult and juvenile Macoma balthica exposed to copper under conditions of starvation, differences in mortality rate, condition, glycogen, burrowing rate and copper content were assessed. No significant differences were observed between adults and juveniles; the influence of treatment and origin was always evident. Animals from the most southern estuaries, Loire and Gironde, near to the species's southern limit of distribution, showed, in the field, the strongest deviations for the ecophysiological traits measured, and were in the experiments the most sensitive to stress. 相似文献
106.
采用TOGA/COARE国际合作考察期间(1992年10月─1993年2月)获得的267次定点(2°S,155°E)定时高空大气探测资料,进行计算分析,发现1992年12月─1993年2月低空存在一支西风急流,有两次分别持续半月之久,而1992年11月的两次赤道西风急流,因无赤道高空急流配合,仅持续2d便消失。本文还指出:(1)赤道低空西风急流是各种海-气指数产生ENSO异常的重要信息;(2)赤道高空急流有滞后赤道低空急流2d左右的响应关系;(3)赤道低空急流是纬向水汽输送的狭窄通道。 相似文献
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108.
用LA-ICP-MS测得安徽滁州2个闪长玢岩样品中锆石~(206)Pb/~(238)U年龄为126.19±0.44Ma和126.4±0.7Ma,结合前人研究,得出滁州地区岩体的侵位时代应为120~130Ma之间,为早白垩世。岩石地球化学研究显示,Si O_2含量变化范围为56.75%~60.90%,具有高Al_2O_3(14.82%~15.77%)、Mg O(4%)、Sr(750×10~(-6))、Sr/Y(62~110)、La/Yb(20~36),低Y、Yb的特征,同时富集轻稀土元素和大离子亲石元素,亏损高场强元素,Eu异常不明显,属于典型的埃达克质岩。Mg~#值为39~45,K_2O/Na_2O值为0.57~0.96,平均值为0.75,明显低于大别造山带加厚下地壳埃达克岩,Ce/Pb值较低,大多集中在3~5之间,类似于陆壳而明显低于洋壳。研究认为,安徽滁州地区埃达克质岩由拆沉下地壳部分熔融形成,埃达克质岩浆在上升过程中与地幔橄榄岩发生反应,导致熔体Mg O、Cr、Ni等含量增加。早白垩世中国东部地壳伸展减薄导致下地壳拆沉,地幔物质的参与带来铜、金等成矿物质,埃达克质岩可作为该地区重要的找矿标志。 相似文献
109.
Understanding the undrained strength of fine-grained soils has been of interest to geotechnical researchers from many practical considerations. In several civil engineering applications, water content of soil is quite high being near or above the liquid limit of soils, and understanding the factors responsible for imparting the strength of soil at high water contents is of great significance. Recently, it has been reported in the literature that the shear strength of soils at these limiting water contents has significant variation. However, the reasons and the factors that probably influence for this variation have not been reported in the literature. This experimental investigation is an attempt in the direction of understanding the reasons for the variation in the undrained strength at higher limiting water content, namely liquid limit considering the various influencing factors like clay mineralogy and fine-sand content present in soil used for determining liquid limit. The results from this study are quite revealing and have been explained based on the mechanisms controlling the undrained strength at liquid limit. 相似文献
110.
Guided by the theory of groundwater system, based on the groundwater level data from the northern basin of Laiyuan Spring area, the authors took into account factors such as the lithology, geological structure and topography to study the relationship between groundwater recharge, runoff and drainage in this area. It was concluded that the infiltration of atmospheric precipitation is the main source of groundwater supply in this area; the upper layer of the Spring area is distributed with the Cambrian-Lower Ordovician karst water, and the lower layer is filled with the Jixian system karst water. The upper layer of karst water supplies to the lower layer of karst water or the pore water in loose strata through the fault while the lower layer of karst water runs to the three strong runoff belts from the east and west sides of the watershed, southwards into the basin, partially replenishing the pore water in loose strata, or forming fault Springs (e.g. Nanguan Spring, Beihai Spring) when dolomite movement encounters faults. Replenished by atmospheric precipitation and the upper and lower layers of karst waters, the pore water in loose strata joins the groundwater in the southern basin and then flows eastwards, in the end it flows out of the system in Shangfanpu. Through the analyses of groundwater level data and hydrogeological drilling data, based on groundwater D and 18O isotope test results, the karst groundwater circulation system in the northern basin of Laiyuan Spring area is further verified, which provides hydrogeological basis for water resources development and utilization as well as protection in this area. 相似文献