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351.
We have executed numerical experiments using a two-layer, wind-driven ocean model with simplified coastal geometry and bottom topography to investigate the possibility of the Kuroshio path transition due to mesoscale eddies. A straight path easily changes into a meandering path due to the eddy action. For this transition, an anticyclonic eddy is preferable to a cyclonic one when imposed in the beginning region of the Kuroshio (east of Taiwan). When imposed southeast of Kyushu, on the other hand, a cyclonic eddy is more effective than an anticyclonic one. The reverse transition, from a meandering to a straight path, did not occur at all in this experiment. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
352.
设计合成一种尚未见文献报道的酚醚型双臂开链冠醚化合物L(L=2,6-二(8’-喹啉氧甲基)-4-甲基-苯甲醚),经元素分析、IR、1HNMR、MS等方法确定了其组成和结构。其Ag(Ⅰ)、Cu(Ⅱ)、Ni(Ⅱ)固体配合物的元素分析结果表明金属离子不同,则其配合物的配位比(M∶L)不同,Ag(Ⅰ)配合物为1∶1,Cu(Ⅱ)、Ni(Ⅱ)配合物为2∶3。并运用热重-差热分析对其热稳定性进行初步研究。  相似文献   
353.
论东海陆架盆地玉泉运动   总被引:1,自引:0,他引:1  
据地质及地球物理勘探资料,并结合周围邻近盆地的对比研究后提出:(1)目前确定的新玉泉运动,其影响比前人描述的轻微得多;(2)以前所确定的原(老)玉泉运动的活动强度比新玉泉运动强烈得多,不应将原(老)玉泉运动取消,而应将新、老玉泉运动的间隔期视为构造变革过渡期。  相似文献   
354.
The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin.  相似文献   
355.
0421号热带风暴"海马"登陆后的温带变性过程特征探讨   总被引:1,自引:1,他引:1  
赵凯  尹东屏  沈树勤 《台湾海峡》2005,24(2):243-250
0421号热带风暴“海马”于2004年9月13日12:00在浙江温州市沿海登陆后,迅速减弱为热低压,然后继续北移;并在中高纬高空槽后的冷平流和中低纬低层暖式切变南部的暖平流共同作用下,低压加深及冷、暖锋生,发展为斜压温带锋面气旋.采用相对辐散作为气旋发展的判据,能很好地体现整个变化过程,气旋的移向基本上沿着相对辐散中心长轴方向移动.通过对地面温度场水平结构分析后发现,该气旋经历了3个阶段:暖涡旋基本对称结构、半冷半热非对称结构、冷涡旋基本对称结构.对流层低层气旋中心上空为暖平流区,引导气旋移动,而对流层中层的冷平流中心区一直位于气旋移向的下侧,推动气旋移动.  相似文献   
356.
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358.
Fens, which are among the most biodiverse of wetland types in the USA, typically occur in glacial landscapes characterized by geo‐morphologic variability at multiple spatial scales. As a result, the hydrologic systems that sustain fens are complex and not well understood. Traditional approaches for characterizing such systems use simplifying assumptions that cannot adequately capture the impact of variability in geology and topography. In this study, a hierarchical, multi‐scale groundwater modelling approach coupled with a geologic model is used to understand the hydrology of a fen in Michigan. This approach uses high‐resolution data to simulate the multi‐scale topographic and hydrologic framework and lithologic data from more than 8500 boreholes in a statewide water well database to capture the complex geology. A hierarchy of dynamically linked models is developed that simulates groundwater flow at all scales of interest and to delineate the areas that contribute groundwater to the fen. The results show the fen receiving groundwater from multiple sources: an adjacent wetland, local recharge, a nearby lake and a regional groundwater mound. Water from the regional mound flows to an intermediate source before reaching the fen, forming a ‘cascading’ connection, while other sources provide water through ‘direct’ connections. The regional mound is also the source of water to other fens, streams and lakes in this area, thus creating a large, interconnected hydrologic system that sustains the entire ecosystem. In order to sustainably manage such systems, conservation efforts must include both site‐based protection and management, as well as regional protection and management of groundwater source areas. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
359.
Milankovitch Theory shows that glacial-interglacial cycles in the Quaternary are related to the variation of solar insolation forcing linked to the earth's astronomical parameters.However,the summer insolation at northern high latitudes,usually considered as the main external forcing for the ice age as Milankovitch pointed out,is marked by the 19- and 23-ka precession periodicities,which is not consistent with the glacial-interglacial cycles.On the other hand,recent studies indicate that the annual mean ...  相似文献   
360.
This work was undertaken for two main purposes. One was to examine spatial and temporal variability in surface water repellency under field conditions in sandy loam forest soils of NW Spain, and its relationship to weather and soil moisture conditions. The other purpose was to get further inside in the dynamics of soil water repellency by studying a wetting–drying cycle under controlled laboratory conditions. Both for the field and laboratory study, water repellency was determined using the Water Drop Penetration Time test. Soil water repellency under field conditions was found to exhibit a seasonal pattern, i.e. it peaked during the summer and was absent between November and May. The time required for repellency to become re‐established during the spring was shorter under eucalyptus than under pine. Spatial variability peaked at an early stage of soil drying and was minimal during the wet period when soils were hydrophilic as well as at the end of the summer, when repellency was strongest. Spatial and temporal variability in water repellency was found to be negatively correlated with soil moisture and, to a lesser extent, with antecedent rainfall. The moisture range of the so‐called transition zone (below which the soil is hydrophobic and also above which it is hydrophobic) differed for the pine (21–50%) and eucalyptus plantations (17–36%). The lower and upper bounds of the transition zone agreed well with the soil moisture contents at the permanent wilting point and at field capacity, respectively. The laboratory results with samples in the wetting phase confirmed those of the field tests. Water repellency increased slightly during the drying phase, but not so much as in the field. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
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