Remote estimation of surficial seafloor properties through the application Angular Range Analysis to multibeam sonar data   总被引：2，自引：2，他引：2  

Luciano Fonseca  Larry Mayer 《Marine Geophysical Researches》2007,28(2):119-126

The variation of the backscatter strength with the angle of incidence is an intrinsic property of the seafloor, which can be used in methods for acoustic seafloor characterization. Although multibeam sonars acquire backscatter over a wide range of incidence angles, the angular information is normally neglected during standard backscatter processing and mosaicking. An approach called Angular Range Analysis has been developed to preserve the backscatter angular information, and use it for remote estimation of seafloor properties. Angular Range Analysis starts with the beam-by-beam time-series of acoustic backscatter provided by the multibeam sonar and then corrects the backscatter for seafloor slope, beam pattern, time varying and angle varying gains, and area of insonification. Subsequently a series of parameters are calculated from the stacking of consecutive time series over a spatial scale that approximates half of the swath width. Based on these calculated parameters and the inversion of an acoustic backscatter model, we estimate the acoustic impedance and the roughness of the insonified area on the seafloor. In the process of this inversion, the behavior of the model parameters is constrained by established inter-property relationships. The approach has been tested using a 300 kHz Simrad EM3000 multibeam sonar in Little Bay, NH. Impedance estimates are compared to in situ measurements of sound speed. The comparison shows a very good correlation, indicating the potential of this approach for robust seafloor characterization.  相似文献   

Evaluation of long-term extreme response statistics of jack-up platforms   总被引：1，自引：0，他引：1  

M. J. Cassidy  P. H. Taylor  R. Eatock Taylor  G. T. Houlsby 《Ocean Engineering》2002,29(13):1603-1631

This paper is concerned with the models appropriate for the dynamic assessment of jack-ups, concentrating particularly on the long-term response due to random ocean waves and on work-hardening plasticity models used for spud-can response. A methodology for scaling of short-term statistics, calculated using a Constrained NewWave technique, is shown in a numerical experiment for an example jack-up and central North Sea location. The difference in long-term extreme response statistics due to various footing assumptions is emphasised. Results for two environmental load conditions are described (one excluding and one including wind and current effects) and the role of sea-state severity in the variation of short-term extreme response statistics is also highlighted.  相似文献   

Data assimilation for a coastal area morphodynamic model: Morecambe Bay     

T.R. Scott  D.C. Mason 《Coastal Engineering》2007

This paper investigates the use of data assimilation in coastal area morphodynamic modelling using Morecambe Bay as a study site. A simple model of the bay has been enhanced with a data assimilation scheme to better predict large-scale changes in bathymetry observed in the bay over a 3-year period. The 2DH decoupled morphodynamic model developed for the work is described, as is the optimal interpolation scheme used to assimilate waterline observations into the model run. Each waterline was acquired from a SAR satellite image and is essentially a contour of the bathymetry at some level within the inter-tidal zone of the bay. For model parameters calibrated against validation observations, model performance is good, even without data assimilation. However the use of data assimilation successfully compensates for a particular failing of the model, and helps to keep the model bathymetry on track. It also improves the ability of the model to predict future bathymetry. Although the benefits of data assimilation are demonstrated using waterline observations, any observations of morphology could potentially be used. These results suggest that data assimilation should be considered for use in future coastal area morphodynamic models.  相似文献   

Experimental investigation on a two-part underwater towed system     

Jiaming Wu  Allen T. Chwang 《Ocean Engineering》2001,28(6)

An experimental set-up is developed and proved to be effective for laboratory study of an underwater towed system. The experimental technique gives a practical method for monitoring the kinematic and dynamic performance of an underwater towed system in a ship towing tank. Both the theoretical and experimental results in the investigation indicate that the hydrodynamic response of a towed vehicle to the wave induced motion of a towing ship can be significantly reduced by applying a two-part tow method. A comparison of the numerical and experimental results in the investigation demonstrates that the numerical simulation results are close to the experimental data, overall agreement between experimental and theoretical results is satisfactory. The results qualitatively verify the mathematical model of a two-part underwater towed system proposed by Wu and Chwang [Wu, J., Chwang, A.T., 2000. A hydrodynamic model of a two-part underwater towed system. Ocean Engineering 27 (5), 455–472].  相似文献   

深海资料浮标体及系泊系统的阻力试验研究   总被引：1，自引：0，他引：1  

张子俊  张祖枢 《海洋技术学报》1993,12(3):7-15

本文结合国家“七五”重点科技攻关项目“深海资料浮标”研制而进行浮标体和系泊系统的各种阻力试验研究，试验成果已直接应用于深海资料浮标系泊系统设计。实践表明本文介绍的各种阻力试验结果是可靠的。  相似文献   

On the fairing of resistance test data: A software-based approach     

Ali Can Takinaci   《Ocean Engineering》2006,33(17-18):2260-2269

A fairing method is presented for giving a good representation of ship model resistance test data, which in general tend to exhibit a scattered trend and need to be smoothed appropriately. One component of the test data originates from the frictional resistance and can be formulated smoothly. The second component is the wave resistance which exhibits a specific harmonic character with peaks and troughs. In this method, this component is modelled using suitable harmonic cosine terms for obtaining the best representation of the corresponding resistance data. The performance of the method is then tested on two example cases, using the characteristic parameters of the sample data as input during the smoothing process.  相似文献   

Estimating migration rates from two tag-release/one recovery experiments   总被引：1，自引：0，他引：1  

Shirakihara  Kunio; Kitada  Shuichi 《ICES Journal of Marine Science》2004,61(5):821-828

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黄茅海河口湾现代动力地貌体系和冲淤过程分析     

杨雪舞  于红兵  孙宗勋  梁添明 《热带海洋学报》1997,(1)

1980—1993年对黄茅海河口湾进行沉积物采样和水流测定及水深测量。根据水动力和地形条件，冲淤分析及Mclaren模型研究河口湾的动力地貌体系、冲淤特征和现代沉积物运移。结果表明：（1）水下地形主要为下泄流或上溯流控制的“深槽－槽沟－浅滩－湾口”的动力地貌体系，反映了河口湾“东进西出”的水流格局；（2）整个河口湾以淤积为主，只有崖门深槽有较明显的优势冲刷特征，并随着崖门深槽向海推移和河口湾“东进西出”水动力作用，黄茅海落潮三角洲相应向西南进积；（3）应用Mclaren模型揭示了黄茅海河口湾现代沉积物运移规律，同样反映了河口湾具有“东进西出”的运移趋势。  相似文献   

用Matlab中的Neural Network Toolbox仿真赤道东太平洋SST的预报模型   总被引：2，自引：0，他引：2  

张韧  蒋国荣  李妍 《海洋科学》2001,25(2):38-42

基于ＮＣＥＰ／ＮＣＡＲ再分析资料和ＣＯＡＤＳ海洋资料中的全球月平均海平面气压场、８５０hPa纬向风场及海洋温度场，利用Ｍatlab中的Ｎeural Network Toolbox仿真环境和ＢＰ模型改进算法比较准确地仿真和反演出了南方涛动指数、赤道纬向风指数和滞后的赤道东太平洋海温之间的动力结构和预报模型。该模型具有很好的拟合精度和可行的预报效果。可在一定时效内预测赤道东太平洋月平均海温的变化趋势。由于所建系统是具有直接因果关系的预报模型，因此不仅可直接用于预测，而且可有效避免类拟非线性微分方程组在积分过程中由于对初值敏感性而可能产生的对预报结果的不确定性。  相似文献   

Th sorption and export models in the water column: A review   总被引：2，自引：3，他引：2  

Nicolas Savoye  Claudia Benitez-Nelson  Adrian B. Burd  J. Kirk Cochran  Matthew Charette  Ken O. Buesseler  George A. Jackson  Matthieu Roy-Barman  Sabine Schmidt  Marc Elskens 《Marine Chemistry》2006,100(3-4):234

Over the past few decades, the radioisotope pair of ²³⁸U / ²³⁴Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to ²³⁴Th. It is focused on the models associated with ²³⁴Th whereas the companion papers (same issue) are focused on present and future methodologies and techniques (Rutgers van der Loeff et al.), C / ²³⁴Th ratios (Buesseler et al.), ²³⁴Th speciation (Santschi et al.) and present and future applications of ²³⁴Th [Waples, J.T., Benitez-Nelson, C.R., Savoye, N., Rutgers van der Loeff, M., Baskaran, M., Gustafsson, Ö., this issue. An Introduction to the application and future use of ²³⁴Th in aquatic systems. Marine Chemistry, FATE special issue]. In this paper, we review current ²³⁴Th scavenging models and discuss the relative importance of the non-steady state and physical terms associated with the most commonly used model to estimate ²³⁴Th flux. Based on this discussion we recommend that for future work the use of models should be accompanied by a discussion of the effect that model and data uncertainty have on the model results. We also suggest that future field work incorporate repeat occupations of sample sites on time scales of 1–4 weeks in order to evaluate steady state versus non-steady state estimates of ²³⁴Th export, especially during high flux events (> ca. 800 dpm m^− 2 d^− 1). Finally, knowledge of the physical oceanography of the study area is essential, particularly in ocean margins and in areas of established upwelling (e.g., Equatorial Pacific). These suggestions will greatly enhance the application of ²³⁴Th as a tracer of particle dynamics and flux in more complicated regimes.  相似文献