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珠江磨刀门河口亚潮频率水位的控制论研究 总被引：3，自引：0，他引：3
本文应用现代控制论研究河口非潮汐海平面变化及其与影响要素的关系。两年连续的水位及水文气象要素资料表明,在0.01—0.50cpd的频带上水位有相当高能的波动,这些波动的能量主要直接或间接来自风应力、河流径流以及河口外的海平面波动。本文应用1982年时间序列辨识了五个二阶的MISO CAR模型,系统输出是河口亚潮频率海平面;系统输入是河流人注流量、风应力和气压。模型检验后对1983年亚潮频率海平面进行一步和多步后报,符合良好。系统仿真定量地估计了各控制因素对水位的相对重要性。频域和时域分析都表明河口水位系统具有振荡特性。 相似文献
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港口航道图测绘期间出于潮位控制的需要,除了利用长期验潮站外需要另设其他短期/临时验潮站。如何深入利用常设短期验潮站积累的历史水位资料以有效减少验潮工作量,已成为海洋测绘实践需解决的现实课题。基于港口长期验潮站与常设短期验潮站的历史同步实测水位资料,采用潮汐差分订正与余水位传递技术,实现了一种精度可靠的港外水域虚拟验潮站水位恢复方法。归纳了港口短期验潮站进行潮汐差分订正的适用条件,列出了采用该种虚拟水位技术恢复水位方法的计算步骤。实例验证及精度评估表明,经潮汐差分订正后的虚拟验潮站采用“天文潮位+邻近验潮站传递余水位法”恢复水位的推算精度,可以满足相关技术规范要求。 相似文献
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台湾海峡冬季亚潮频水位波动的初步研究 总被引：4，自引：0，他引：4
冬季台湾海峡两岸水位存在较强亚潮频波动,西岸尤为显著.波动能量在32、10.7、4.6、3.6和2.9天频带出现谱峰.分析表明除主要由风场波动造成的埃克曼增减水(32、3.6天波动)外,海峡风场的波动还激发了周期为4.6和2.9天的陆架波,16天波动也具有陆架波的物理性质,但源于东海,非海峡风场所致. 相似文献
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在海洋工程建设(如港口建设、沿岸工程和海上平台建筑等)中,必须对正常条件(即作业条件)和极端条件(即恶劣环境条件)下的海洋环境参数作出估计。对于海洋水位而言,如《港口工程规范》(以下简称《规范》)中的设计水位和乘潮水位等即属于前者,校核水位即属于后者。正常条件下的水位参数比较容易确定,因为这种条件下的观测数据比较容易获得,有比较丰富的已知资料。极值水位是指若干年内オ有可能出现的高水位或低水位,例如在《规范》中要求50年一遇的水位作为校核水位。所以如依靠直接观测,必须具备至少几十年的观测资料,这一要求只有在有长期验潮站的港口オ能达到。如资料系列不够长,则必须采用一定的方法对它们的数值作出估计。
在有相当长期观测资料的情况下,常常采用极值分布的方法,即每年取一个最高(或最低)水位,然后拟合某种理论或经验的分布曲线,从而得出不同重现期的极高(或极低)水位。这种方法所得结果比较可靠(但也不是没有问题,详见第五节),但对资料要求高，特别在新建港口或海上工程,常常不能采用。
在有数年观测资料的情况下,可以采用同步差比法(见《规范》)。当拟建港和主港潮汐性质和风暴潮特性相近,特别是两地距离较近时,这种方法常常能给出良好的结果,不失为一种有效的方法,但其应用受到一定的条件限制
近年来,国外提出了一种“联合概率法”(Pugh and Vassie,1978,1980)。这种方法把水位中的潮汐水位(这里指的是可用调和方法预报的潮位,其中也包括周期性的气象潮)和余水位(即实测水位减去预报水位)分开,分别求其分布,然后再用联合概率法回过来求合成水位的分布,从而得出极值水位高度。这种方法的优点是能够充分利用水位观测资料,因而可以在观测时间较短的情况下得出比传统方法更稳定的结果。在Pugh和Vassie所提出的方法中,潮汐和余水位被看作是互相独立的。这一假定在深水海区较接
近实际,但在某些浅海区则与实际有较大出入。例如Pugh和Vassie发现,对位于泰晤士河的绍森德港,由联合概率法按上述假定得出的百年一遇的高水位比由传统极值分布方法得出的数值大约高60cm;而传统方法的结果与49年期间观测到的最高水位较接近。Pugh和Vassie在后来的文章中对绍森徳港的问题作了专门处理,得出较合理的结果,但基本上是采用经验的方法,在一般实际中使用是困难的。
为了考虑潮汐和余水位的这种相关性,我们曾将联合概率法予以推广,提出了条件分布联合概率法(方国洪、王骥,1987)。这种方法不论潮汐和余水位是否相互独立均可应用,具有更强的适应性。本文根据该文的基本想法,选择了我国沿海资料较长,并具有较好代表性的10个长期验潮站共286年的潮汐逐时记录,进行了分析研究,对该文提出的方法作了修改和补充。 相似文献
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龙口湾的潮汐特征分析 总被引：1，自引：0，他引：1
根据龙口港验潮站的长期潮位资料和龙口湾内３个临时测站的短期验潮资料（２个站１个月，１个站ｌａ），对该区的潮汐特征、工程水位及暴潮增水等作了具体分析。 相似文献
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海面水位各种高度的出现频率在海洋工程和航运中具有重要意义。为了得出其分布，最直接和可靠的方法当然是利用长期实测资料进行统计。但是在需要获得水位分布的地点往往没有足够长期的资料，这时就必须采用其他的方法来推算。
我国近海引起水位升降的主要因素是天文潮，故利用潮汐调和常数推算天文潮并考虑到到非天文因素的水位变化是一个比较可靠的办法。这个方法比较准确，但需要进行潮汐预报，计算量比较大。本文提出的方法所涉及的计算量很小，但仍能获得较好的效果。这个方法的基本出发点是：由于不同地点海面水位分布有一定的共性，水位分布和它的数字特征之间有密切的关系，而数字特征又决定于潮汐调和常数及非天文水位标准差，因而可利用潮汐调和常数及非天文水位标准差求得数字特征，然后进一步得出水位分布。这个方法所用到的数字特征为标准差、偏度和峰度，它们汉语拼音的第一个字母分别为B,P和F，故这个方法被称为BPF 法。
1977年我们提出 BPF 法时，主要应用于海图深度基准面，应用中的有关问题将另文讨论。 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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Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63
This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested. 相似文献
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G. Parthiban 《Marine Georesources & Geotechnology》2000,18(3):223-235
Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments. 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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《海洋学报(英文版)》2014,(11):161-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