Measurement of nuclides of uranium and thorium series of disequilibrium using γ-spectroscopy   总被引：3，自引：0，他引：3  

Liu Guangshan  Huang Yipu  Li Jing  Ye Lin 《海洋学报(英文版)》2002,21(4):505-517

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒａｄｉｏｎｕｃｌｉｄｅｓｏｆｎａｔｕｒａｌｕｒａｎｉｕｍａｎｄｔｈｏｒｉｕｍｓｅｒｉｅｓｃａｎｂｅｕｓｅｄｔｏｔｒａｃｅｍａｒｉｎｅｐｒｏ ｃｅｓｓｏｆｖａｒｉｏｕｓｔｅｍｐｏｒａｌａｎｄｓｐａｔｉａｌｓｃａｌｅａｎｄｐｒｏｐｅｒｔｉｅｓｔｈａｔｐｒｏｖｉｄｅｐｌｅｎｔｉｆｕｌｉｎｆｏｒｍａｔｉｏｎａｂｏｕｔｐｈｙｓｉｃｓ,ｃｈｅｍｉｓｔｒｙ ,ｇｅｏｓｃｉｅｎｃｅａｎｄｂｉｏｌｏｇｙｏｆｏｃｅａｎｂｅｃａｕｓｅｔｈｅｙｈａｖｅｄｉｆｆｅｒｅｎｔｃｈｅｍｉｃａｌｐｒｏ…  相似文献   

Bathymetry of the Tonga Trench and Forearc: a map series   总被引：1，自引：0，他引：1  

Wright  Dawn J.  Bloomer  Sherman H.  MacLeod  Christopher J.  Taylor  Brian  Goodlife  Andrew M. 《Marine Geophysical Researches》2000,21(5):489-512

Four new bathymetric maps of the Tonga Trench and forearc between 14 °S and 27 °S display the important morphologic and structural features of this dynamic convergent margin. The maps document a number of important geologic features of the margin. Major normal faults and fault lineaments on the Tonga platform can be traced along and across the upper trench slope. Numerous submarine canyons incised in the landward slope of the trench mark the pathways of sediment transport from the platform to mid- and lower-slope basins. Discontinuities in the trench axis and changes in the morphology of the landward slope can be clearly documented and may be associated with the passage and subduction of the Louisville Ridge and other structures on the subducting Pacific Plate. Changes in the morphology of the forearc as convergence changes from normal in the south to highly-oblique in the north are clearly documented. The bathymetric compilations, gridded at 500- and 200-m resolutions and extending along 500 km of the landward trench slope and axis, provide complete coverage of the outer forearc from the latitude of the Louisville Ridge-Tonga Trench collision to the northern terminus of the Tonga Ridge. These maps should serve as a valuable reference for other sea-going programs in the region, particularly the Ocean Drilling Program (ODP) and the National Science Foundation MARGINS initiative.  相似文献   

山东蓬莱大黑山岛碱性火山岩地球化学特征          下载免费PDF全文

黄朋  付永涛  李安春  肖尚斌 《海洋与湖沼》2007,38(1):91-96

庙岛群岛中的大黑山岛出露碱性火山岩,对研究壳-幔过程及黄、渤海演化具重要意义。文中作者对大黑山岛火山岩的常、微量元素、K-Ar年龄及Nd-Sr-Pb同位素体系进行测试确定。结果表明,岩石属钠质碱性玄武岩系列,岩浆岩喷发可分为8Ma前和8Ma后两个阶段;岩石常量元素含量除K2O、Na2O外差异小;随着火山岩的演化,岩浆源区深度变大;大黑山火山岩Nd-Sr-Pb同位素比值与夏威夷洋岛玄武岩相似,其岩浆的地幔端元组分为PREMA DM,又以PREMA为主,并有MORB物质混入。  相似文献   

一种基于BP算法学习的小波神经网络   总被引：2，自引：1，他引：2  

陈哲  冯天瑾  陈刚 《中国海洋大学学报(自然科学版)》2001,31(1)

为发展 Szu的基于信号表示的小波神经网络 ,提出一种多输入多输出的小波网络模型 ,网络隐层采用框架小波函数、输出层采用 Sigmoid激励函数 ,并选用“熵误差函数”以加速网络的学习速度。奇偶判别和混沌时间序列预测例子的实验结果表明了它具有良好的函数逼近能力和推广能力 ,收敛速度和均方误差均优于相同结构的多层感知器模型。  相似文献   

A Numerical Model of Coastal Processes of Sand Beaches Based on Long-Term Wave Series     

Zhang Changkuan  Wang Zhen  Zhang Dongsheng Associate Professor  Dept. of Navigation  Ocean Engineering  Hohai University  Nanjing Lecturer  Dept. of Navigation  Ocean Engineering  Hohai University  Nanjing Professor  Dept. of Navigation  Ocean Engineering  Hohai University  Nanjing 《中国海洋工程》1995,(2)

A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable.  相似文献   

A map series of the Southern East Pacific Rise and its flanks, 15° S to 19° S     

Daniel S. Scheirer  Ken C. Macdonald  Donald W. Forsyth  Stephen P. Miller  Dawn J. Wright  Marie-Hélène Cormier  Charles M. Weiland 《Marine Geophysical Researches》1996,18(1):1-12

Four large-scale bathymetric maps of the Southern East Pacific Rise and its flanks between 15° S and 19° S display many of the unique features of this superfast spreading environment including abundant seamounts (the Rano Rahi Field), axial discontinuities, discontinuity migration, and abyssal hill variation. Along with a summary of the regional geology, these maps will provide a valuable reference for other sea-going programs on-and off-axis in this area, including the Mantle ELectromagnetic and Tomography (MELT) experiment.  相似文献   

泥河湾盆地洞沟剖面的光谱光度时间序列     

韩志勇  李徐生 《海洋地质与第四纪地质》2006,26(4):73-79

泥河湾盆地东部的洞沟剖面出露一套以湖相为主的地层,其顶部覆盖了末次间冰期古土壤与末次冰期黄土。测量了该剖面的光谱光度和磁化率,结果显示,亮度(L*)随深度的变化趋势基本与色度a*、色度b*相反,即低亮度值对应高色度值。砂层的亮度值相对低,而质量磁化率高。亮度记录可以与洛川黄土剖面的磁化率记录对比,即亮度低值段可与磁化率高值段对比,这可能源于两者都受东亚季风的控制。对比后获得了30个时间控制点,在此基础上,建立了洞沟剖面测量参数的时间序列。谱分析表明,各参数的时间序列显示了主要的米兰科维奇周期,这显示泥河湾古湖沉积物对古气候的周期性变化敏感。  相似文献   

Far-field control of long-term changes in Northumberland (NW North Sea) coastal zooplankton     

Frid  Christopher L. J.; Huliselan  Niette V. 《ICES Journal of Marine Science》1996,53(6):972-977

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The Continuous Plankton Recorder: concepts and history, from Plankton Indicator to undulating recorders   总被引：1，自引：0，他引：1  

P. C. Reid  J. M. Colebrook  J. B. L. Matthews  J. Aiken  Continuous Plankton Recorder Team 《Progress in Oceanography》2003,58(2-4):117

Alister Hardy conceived the Continuous Plankton Recorder (CPR) survey in the 1920s as a means of mapping near-surface plankton in space and time, interpreting the changing fortunes of the fisheries and relating plankton changes to hydrometeorology and climatic change. The seed he planted has grown to become the most extensive long-term survey of marine organisms in the world and the breadth of his vision becomes ever more apparent. The survey has now run for over 70 years and its value increases with every passing decade. Operating from ‘ships of opportunity’ the machines used are robust, reliable and easy to handle. Wherever possible, all the sampling and analytical methods have not been changed to maintain the consistency of the time series. Computerisation and the development of new statistical approaches have increased our ability to handle the large quantities of information generated and enhance the sensitivity of the data analyses. This overview, based on almost 900 papers, recounts the various phases in the history of the survey. It starts with the Indicator Survey (1921–1934), the deployment of the first CPR on the Discovery Expedition (1924–1927) and the early CPR survey in the North Sea (1931–1939). The survey reopened in 1946 after the Second World War and expanded across the North Atlantic to North America from 1959. Taxonomic studies were initiated and an emphasis was placed on patterns of distribution, which were seen to reflect the varying oceanographic conditions. The years 1968–1976 saw further expansion with operations even in the American Great Lakes, publication of a Plankton Atlas and initial evidence for a downward trend in plankton biomass. At about this time electronic instrumentation was attached to CPRs to make additional measurements and work was started on the development of a new generation of undulating Continuous Plankton and Environmental Recorders (CPERs). In 1976 the survey moved to Plymouth. Scientific priorities in the UK changed in the subsequent decade and funding became more difficult to secure even though some of the CPR papers being published at the time are now regarded as classics in plankton ecology. In 1988 the UK Natural Environment Research Council (NERC) decided to close the survey. An international rescue operation led to the creation of the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) in 1990, which has continued with consortium funding from a number of countries, and from 1999 again included NERC. The scientific rationale of the survey has gained credibility as concern over climate change and other anthropogenic effects has grown and as the key role that plankton plays as an indicator of large-scale environmental conditions becomes ever more apparent. Recently, the survey became an integral component of the Global Ocean Observation System (GOOS) and expanded into the North Pacific. It plays a complementary role in many large international and multidisciplinary projects and is providing inspiration, advice and support to daughter surveys elsewhere in the world. At the start of a new millennium, Hardy’s vision from the 1920s is a powerful driving force not just in international biological oceanography, but in global environmental science.  相似文献   

Geochemical cycling in the Hooghly estuary, India     

B. L. K. Somayajulu  R. Rengarajan  R. A. Jani 《Marine Chemistry》2002,79(3-4)

U–Th decay series isotopes, δ¹⁸O and Si measurements in the river estuarine waters and sediments of the polluted Hooghly estuary as well as the surface waters of the Bay of Bengal, its high salinity end member, are reported. Dissolved Si indicates that there are probably two mixing regimes, dissolved U behaviour is nonconservative and δ¹⁸O behaves conservatively in the overall estuarine region. Isotopes of reactive elements, viz. ²³⁴Th and ²¹⁰Po, are removed from the estuarine waters in <2 days and <1 month, respectively, which is due to high suspended matter (30–301 mg l⁻¹). ²²⁸Ra and ²²⁶Ra are profusely released into the estuarine waters in the low to mid-salinity regions.As expected, the opposite trend is observed in the case of estuarine sediments and suspended matter. Reactive isotopes of Th, ²¹⁰Pb and ²¹⁰Po are enriched, whereas Ra isotopes are depleted with respect to their parent nuclides in the estuarine sediments and suspended matter. ²³²Th/Al ratio appears well suited to study the distribution and mixing of the bed load sediments of the Ganga–Brahmaputra (G–B) and the Hooghly rivers with those from other rivers on the Bay of Bengal floor.  相似文献