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脐带缆用于连接水上浮体和水下生产系统,缆芯由钢管单元、光纤单元和电缆单元等组装而成,缆体外层是由铠装钢丝层螺旋缠绕以及聚合物外护套组装而成,截面结构复杂。利用ANSYS有限元通用软件建立双层铠装脐带缆的三维多层接触摩擦有限元模型,计算其截面拉伸刚度,将拉伸刚度数值模拟值与理论结果进行对比,验证有限元模型的正确性;分析比较铠装层不同缠绕角度、缠绕方式和钢丝直径下脐带缆模型的拉伸刚度。结果表明:铠装钢丝层缠绕方式、缠绕角度、铠装钢丝直径对双层铠装脐带缆模型的拉伸刚度、最大等效应力模拟结果均有影响。 相似文献
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潮汐能是可再生的清洁能源,现代潮汐能的利用,主要是潮汐能发电.基于南澎列岛潮汐能资源特点以及潮汐能发电的原理、和技术发展,提出在南澎列岛建设单库双向型潮汐电站,并提出了发电模式的初步设想. 相似文献
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遥控水下机器人脐带缆收放绞车设计及牵引力分析 总被引：1，自引：0，他引：1
脐带缆收放技术是有缆遥控水下机器人的一项关键技术,该技术直接影响水下机器人载体的收放及作业过程中脐带缆的安全。针对目前水下机器人收放系统中脐带缆收放技术的特点,给出了一种具有自动排缆、低张力缠绕、能够提供大牵引力和安全制动功能的紧凑新式脐带缆绞车方案,并对牵引绞车与储藏绞车之间脐带缆张力与牵引绞车的牵引力进行了理论分析,给出了二者之间的关系函数。 相似文献
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深水动态脐带缆内部结构复杂,其阻尼特性对脐带缆的舞动以及疲劳损伤有着重要的影响。脐带缆在和流体相互作用过程中,脐带缆内部构件可能会产生滑动,进而影响脐带缆的结构阻尼,这也使得真实海况中脐带缆的舞动和疲劳是一项复杂而值得深入研究的课题。为验证有限元模型能够很好地模拟脐带缆的结构阻尼特性,在考虑内部结构单元间摩擦的基础上,利用ANSYS建立了用于中国南海某油田的脐带缆多层滑移接触摩擦模型。同时,采用自由衰减法对该动态脐带缆开展了原型试验,测得了该缆的结构阻尼比与自振周期。通过对比有限元模型计算结果与原型试验结果发现：数值模型获得的该脐带缆的结构阻尼值与试验值非常接近,这为工程中获得脐带缆结构阻尼比的值提供了好的方向。 相似文献
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脐带缆是连接平台或浮式生产系统与海底油井的控制管缆,缆芯由管单元、光纤单元、电缆单元、以及填充单元组装而成,缆体外层由铠装钢丝螺旋缠绕和聚合物护套组成。基于ANSYS有限元软件,建立无铠装含填充的钢管脐带缆三维有限元模型,在自由端可扭转、不可扭转约束条件下,计算模型的拉伸刚度,将拉伸刚度的数值模拟与理论结果进行对比,验证有限元模型的正确性;分析比较含填充与不含填充两种截面形式脐带缆模型的力学性能,结果表明:填充单元、拉伸率对脐带缆模型的拉伸刚度、最大等效应力模拟结果均有影响。 相似文献
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脐带缆是进行水下油气资源开采的关键设备,在深海油气资源的开发过程中起着至关重要的作用。脐带缆是由多种功能单元螺旋缠绕而成的非粘结复合结构,各层构件之间会出现接触摩擦与滑动现象,使脐带缆的截面设计和结构分析变得十分困难。本文结合国内外研究的成果,在对脐带缆结构进行理论分析的基础上,利用ANSYS软件分别对无铠装和有铠装脐带缆进行数值模拟分析,采用梁单元和壳单元模拟管件,并用点-点和点-面接触单元模拟管件之间的相互作用,将数值模拟结果与理论计算结果进行对比,探讨不同的管件缠绕角度、摩擦因数对脐带缆的拉伸和弯曲刚度的影响。分析结果可为工程应用提供参考和借鉴。 相似文献
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脐带缆是深海油气开发的关键设备之一,主要由钢管单元、电缆单元、光缆单元、护套及铠装单元组成。脐带缆在全寿命周期经过设计制造、储存、安装、在位运行、修复阶段,其每个阶段的可靠性并不是某个常数,而是随时间变化的函数,因此有必要对脐带缆全寿命周期可靠性的变化进行分析。建立某气田水下脐带缆在储存、安装、在位运行阶段的故障树模型,将其转化为多阶段贝叶斯网络模型进行建模分析,基于OREDA手册数据,假设部件寿命服从指数分布,对脐带缆存储、安装、在位运行阶段的可靠性进行分析,得到不同阶段脐带缆可靠性的变化曲线,并与可靠性框图方法进行对比分析。同时,通过引入条件可靠性对该方法进行了优化,分析脐带缆修复后的可靠性变化,以及对脐带缆关键部件进行重要度分析,针对薄弱环节提出改进措施。可靠性分析可为水下脐带缆的安全运行提供技术支持,同时也为海洋结构与设备的全寿命周期可靠性分析提供了一种方法参考。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 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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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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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 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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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 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