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如何有效利用海洋环境要素多种来源资料建立其极值概率模型,是实际工程中常遇到的问题.根据海洋环境要素母体子样与其极值子样之间的关系,讨论了现场子样的确定,并推导了其一致性检验方法和计算公式.结合前人对于通过一致性检验的数据进行深入分析建立了数据的可信度概念及其计算方法的研究结果,建立了先验环境要素资料的可信度计算方法.在此基础上结合加权融合方法,建立了海洋环境要素极值的加权融合概率模型,从而使可用信息得到充分利用.通过模拟算例和实际数据验证了一致性检验方法和加权融合概率模型的合理性. 相似文献
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异地海域年极值风暴增水同现规律的探讨 总被引：1，自引：1，他引：1
以塘沽和龙口海洋观测站20年极值增水值为样本，基于二维冈贝尔逻辑分布模式，探讨了不同海域风暴潮增水极值的联合分布规律。通过对二维分布的联合概率密度、条件概率密度和同现概率的计算，给出了相应的工程设计参数，供有关部门在防潮规划时参考。 相似文献
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在钢悬链线立管分析中,材料性能、载荷参数、计算方法等都存在着大量不确定性。为考虑不确定性因素造成的影响,采用作用效应-抗力半随机过程构建可靠性模型,并采用极小化变换转化为静态可靠性问题。选用物理含义较为明确的屈服判定准则建立功能函数,通过单样本K-S检验对载荷随机过程的概率特性进行极值统计,提出载荷转化的方法以实现与目标可靠性指标的比对,并引入模型和主观不确定性随机变量。在此基础上采用改进的一次二阶矩法,对立管的强度可靠性进行了计算。结果表明此方法与利用系数方法能够相互印证,可以为立管的可靠性计算提供参考。 相似文献
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重现期波高是港口海岸及海洋工程设计中不可回避的一个重要设计参数,尤其对深水海港、海上平台、海底油气管道、沿海核电站等重大涉海工程设计具有巨大的经济价值和深远的社会效益。但是,现有重现期波高推算缺乏统一的计算方法,导致计算结果相差悬殊。研究重现期波高的统一化计算方法,分析重现期波高计算中存在的各种不确定因素,提出减少这些不确定因素的新方法,建立误差小、应用方便、方法统一的重现期波高计算方法。基于澳大利亚悉尼站的长期连续观测波浪数据,研究发现:广义帕累托函数(generalized Pareto distribution III,GPD-III)和威布尔(Weibull)是重现期波高计算的最佳候选极值分布函数,新推导的函数形状参数计算公式较好提高重现期波高的计算精度,极值波高数据的分析方法和样本大小是影响重现期波高计算精确度的两个重要因素,短期波浪资料和年极值法可能高估重现期波高值。逐个风暴的极值波高数据分析法及最佳候选极值分布函数GPD-III和Weibull建议应用于涉海工程设计的重现期波高推算。 相似文献
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全球气候变化背景下,海平面上升是一个潜在的重大风险,为防范气候灾害,应对极端气象海洋事件,需客观、定量地对未来极端海平面变化进行科学预测。为此,基于Copula函数和动态极值分析理论,综合考虑平均海平面变化(包括垂直陆地运动和基准的局地变化)与潮、涌、浪等其他气候变化的增水对极端海平面高度的影响,采用DREAM方法改进Bayes推断对动态极值模型的参数空间估计问题,提出一种新的模型对未来极端海平面高度变化进行预测,旨在改进传统模型存在的不确定性问题,并运用该模型对气候变化背景下厦门地区未来35年的海平面变化情景进行了模型应用和实验模拟。 相似文献
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根据收集的渤、黄海沿岸主要海洋站(塘沽、羊角沟、烟台、威海、乳山口、青岛和日照)1950年以来各年最高潮位资料(个别站位资料样本较小),应用能优化处理小样本的基于信息扩散原理的模糊风险评估模型,对渤、黄海沿岸各海洋站年最高潮位的多年一遇极值情况进行了超越概率计算,并与《港口工程技术规范》推荐的极值I型(Gumbel曲线)方法进行比较。除羊角沟站误差3%外,其它站误差均在2%及以下,表明文中基于信息扩散原理的风险评估模型在兼顾小样本条件下所给结果是比较可靠的。这对于潮位等水文实测资料短缺的新建或拟建工程区进行工程水文要素设计重现期的推算将有较好的帮助。 相似文献
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《海岸工程》2018,(4)
船舶和海洋结构物长期服役在恶劣的海洋环境中,受到风、浪、流等各种随机载荷甚至极端载荷的作用,而极端载荷将造成不可逆的结构损伤,严重影响海上作业安全。确定船舶与海洋结构物所在海域的极端天气情况,包括重现期内的最大风速或最大浪高等成为结构设计的关键问题之一。基于平均条件超越率(Arerage Conditional Exceedance Rate,ACER)方法的基本原理,利用蒙特卡罗法产生多组随机风速载荷样本,建立基于极值分布规律的插值计算方法,利用平均超越率和极值的关系,对由蒙特卡罗法产生的模拟随机风速数据进行了重现期为25,50和100a的极值预测。本方法适用于包括非独立同分布在内的任何分布类型数据的极值预测,且通过对比验证了方法的预测精度。 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
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Hoi-Soo Jung Kap-Sik Jeong Yong-Shik Chu Sung-Hyun Park Ki-Hyune Kim 《Marine Georesources & Geotechnology》2001,19(3):181-195
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2001,24(1):27-33
This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake. 相似文献
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This study tests the hypothesis that the in situ void ratio of surficial marine sediments may be predicted from shear wave velocity-depth data with a reliability equal to that of other methods currently available. Shear wave velocity is fundamentally controlled by the number of grain-to-grain contacts per unit volume of material and by the effective stress across those contacts. In this study, three previously established empirical formulae are used to predict void ratio from velocity-depth data. Field data were acquired along a transect off the northern Californian coast across which water depth increased from 35 to 70 m and seafloor sediment type varied from sand to silty-sand, respectively. A towed seafloor sled device was used to collect shear wave refraction data, and a marked, systematic decrease in velocity was observed along the line, ranging from 35-70 m/s for the coarse, near-shore material to 25-40 m/s for the finer, offshore deposits. Void ratios predicted from these velocities were compared with data measured directly from box-core samples. Of the formulae used for prediction, two agree remarkably well with the control data. Both predicted and control values increase from 0.6-0.8 for the sandy material to 1.1-1.5 for the silty-sand. Thus, this study does not disprove the hypothesis set and demonstrates the potential of field shear wave velocity-depth data as a means of delineating spatial variation in void ratio for surficial marine sediments in a remote, nondestructive manner. 相似文献
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Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ～ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream. 相似文献