CODAR in Germany--A status report valid November 1985

The use of CODAR by the University of Hamburg has extended to a wide variety of experimental and oceanographic activities over the last three years. These have ranged from Arctic studies from land and ships to observations of the Dead Sea, all yielding surface current data. Hardware improvements have been investigated, including IF amplifier changes and loop-antenna arrays for shipboard operation.     

Performance comparison between vertical and horizontal arrays for geoacoustic inversion

Most of the research on model-based geoacoustic inversion techniques has concentrated on data collected using moored vertical receiver arrays. However, there are many advantages to considering geoacoustic inversion using a towed horizontal array. Towed arrays are easily deployed from a moving platform; this mobility makes them well suited for surveying large areas for sea-bed properties. Further, if a model-based geoacoustic inversion scheme uses both a towed source and array, the separation between the two can be kept short, which reduces the requirement for range-dependent modeling. Range-independent modeling is used for inverting all the horizontal array data considered in this paper. Using the Inversion Techniques Workshop Benchmark Test Cases, the performance of a horizontal (simulated towed) and vertical arrays are compared and found to be very similar. However, it will be shown that, for Benchmark Test Case 3, where the bathymetry is flat and a hidden bottom intrusion exists, a towed horizontal array is ideal for determining the range-dependent sea-bed properties. The practical advantages of using a towed array are clear and the purpose of this paper is to show that the performance is similar (and in some cases better) than using moored vertical arrays.     

Geoacoustic inversion of tow-ship noise via near-field-matched-field processing

This paper discusses geoacoustic inversion from tow-ship noise data acquired via a horizontal towed array. Through simulations and experimental results, it is shown that even very quiet ships radiate sufficient noise power to enable self-noise inversion of basic geoacoustic parameters such as effective bottom velocity. The experimental results presented are particularly encouraging in view of the high level of interference shown to be tolerated from nearby shipping.     

正弦激励下零浮力海洋拖缆动力特性与实验研究

海洋地震拖缆是海洋油气资源勘探中的关键设备,为研究海洋地震拖缆的动力特性及其在不同频率正弦激励干扰下的动力响应,建立了零浮力拖缆的数学模型,设计了一套完整的实验方案,通过弹性测力机构放大张力信号以排除环境干扰,测量了不同拖曳速度与激振频率条件下拖缆首部的张力变化及缆上位移响应情况,初步分析了正弦激励作用下零浮力拖缆的动力学响应。弹性测力机构具有良好的线性度与可重复性,拖缆受到的水阻力与拖曳速度的平方成正比,数值计算与实验结果对比验证了数学模型的正确性,初步分析了正弦激励作用下零浮力拖缆的动力学响应。     

星载SAR监测海洋溢油污染的初步研究

对星载SAR监测海洋溢油的基本原理进行总结并分析了影响溢油监测的SAR参数及干扰SAR海洋溢油监测的各种因素;对搜集到的星载SAR数据进行处理,并给出中国黄海海域的海上溢油分布的初步统计分析,结果表明该海区的溢油主要分布在海上主要航线附近。     

Monitoring benthic biodiversity restoration in Lyme Bay marine protected area: Design,sampling and analysis

Long-standing concerns about the effects of scallop dredging and demersal trawling on high diversity mudstone reef and cobble habitats in Lyme Bay, southwest England, were addressed by the exclusion of bottom towed fishing gear from a 206 km² area in July 2008. A consortium led by Plymouth University Marine Institute was funded by the UK Department of Environment, Food and Rural Affairs to design and implement a study (initially funded for 3 years) to examine the effects of the closure on both nekton and epibenthos. This paper provides a detailed account of the methodology employed from survey design to data analysis to provide a protocol for future MPA monitoring programmes. Information on historical fishing effort, substrate distributions and current and previous closure boundaries was overlaid using GIS to locate suitable monitoring sites. Non-destructive and cost-effective techniques, including a towed high-definition video array and static baited video, were used to quantify changes in relative abundances of epibenthos and nekton over three years at sites previously fished but now closed to bottom towed fishing compared to both fished and un-fished reference sites. The monitoring programme as described provides a model for robust, cost-effective evaluation of the efficacy of policy instruments for feedback into the adaptive management cycle.     

近海底高分辨率地震探测系统设计与实现

受大深度水体的影响,传统的海面拖曳式多道地震技术在进行深水地层探测时,目标地层深度处的菲涅耳半径非常大,水平分辨率低,难以满足海域天然气水合物高精度探测需求。针对海面拖曳式地震探测技术存在的上述问题,设计了一套可以在2 000 m水深近海底作业的地震探测系统。应用耐压透声发射阵技术,克服了20 MPa外压环境和瞬时内压冲击对等离子体震源子波幅频特性的不利影响,研制的深拖等离子体震源的声源级达到214 dB,主频低于1 000 Hz;水下控制中心采用集成SoC片上系统设计,可以对震源进行定距激发控制,进行近海底多道地震数据的连续采集。系统在2019年深海试验拖曳最大深度达2 025 m,测试剖面数据显示最大地层穿透深度达380 m,纵向分辨率<2 m,横向分辨率<10 m,为深水海域沉积地层的深拖高分辨率地震探测提供了技术支撑。     

Spar平台湿拖阻力性能研究

海洋平台由拖船拖至工作地点,计算海洋平台的湿拖阻力在实际工程应用中具有重要意义。采用实验和数值模拟两种方法进行桁架式Spar平台的湿拖阻力性能研究,并将两种结果进行对比。并分析了桁架式Spar平台的垂荡板间流场的变化规律。研究结果表明,Spar平台的湿拖阻力中,摩擦阻力所占总阻力的比例小于10%;在平台拖曳运动的前几秒中,垂荡板间流体剧烈运动,速度和压力显著变化,随后就运动慢慢变缓;Spar平台在低速拖曳时会产生明显的波浪,尾部有回流。     

Dynamics and control of a towed underwater vehicle system, part I: model development

Autonomous vehicles are being developed to replace the conventional, manned surface vehicles that tow mine hunting towed platforms. While a wide body of work exists that describes numerical models of towed systems, they usually include relatively simple models of the towed bodies and neglect the dynamics of the towing vehicle. For systems in which the mass of the towing vehicle is comparable to that of the towed vehicle, it becomes important to consider the dynamics of both vehicles. In this work, we describe the development of a numerical model that accurately captures the dynamics of these new mine hunting systems. We use a lumped mass approximation for the towcable and couple this model to non-linear numerical models of an autonomous surface vehicle and an actively controlled towfish. Within the dynamics models of the two vehicles, we include non-linear controllers to allow accurate maneuvering of the towed system.     

基于热红外视频图像监测的海面溢油识别技术研究

针对现有海面溢油检测技术难以在石油泄漏初期（尚未形成海面大规模油膜覆盖）及时发现油膜的难题,本文在前期基于热红外图像测算海面油膜面积方法研究的基础上,结合油泄漏至海面后油膜的扩散特征,提出了一种基于热红外视频图像监测油膜面积变化以及时识别海面溢油的方法。首先,基于单帧热红外图像处理算法提取海面前景区域（包含油膜区域与相似物干扰区域）并计算各区域所代表的实际物理面积。基于视频图像处理技术跟踪测算前景区域中各连通区域的实际物理面积变化情况,根据各连通区域的面积变化率识别前景区域中是否存在油膜,从而判断海面是否发生溢油。实验结果表明:所提出的方法能有效识别不同黏度的石油泄漏至海面形成的扩散油膜,在水面包含波浪与相似物干扰时也具有良好的识别精度。该方法适用于特定场景下（如码头、船舶等）的溢油事故的鉴别,能为溢油事故的及时发现和预警提供技术支持。     

An underwater towed electromagnetic source for geophysical exploration

Low-frequency electromagnetic methods are used in geophysical exploration to detect the magnetic field distortion between a transmitter and receiver produced by locally conductive bodies. Both ground and airborne systems are in current use. It is possible to similarly conduct underwater geophysical exploration by using an underwater towed source of electromagnetic radiation and a receiving magnetic or electric field detector. The receiver can be towed on an auxiliary cable, mounted on a boom on the towing platform, or land based. An underwater towed electromagnetic source suitable for ocean-bottom exploration has been constructed, and its underwater propagation characteristics at low frequency have been studied. This underwater calibrated source (UCS) is 4 m long, weighs 383 kg in air, and can produce vertical and horizontal magnetic dipoles and a horizontal electric dipole. Powered by a current-feedback-controlled, high-power, modified sonar amplifier, the UCS can produce 9710 ampereturn.m2 of magnetic dipole or 200 A.m of electric dipole at 50 A at frequencies up to 200 Hz without significant attenuation from coil inductance. This paper concentrates on the mechanical, hydrodynamic, and magnetic design details of the UCS and the electrical system, consisting of the high-current drive power system and the shipboard monitoring system for attitude and depth detectors.     

深度学习在海洋信息探测中的应用:现状与展望

深度学习可以通过深度神经网络,使机器理解学习数据,从而提高数据分类效果和预测结果的准确性,因此在海洋信息探测中应用越来越受到重视.作者基于深度学习的基本原理,阐述了海洋上常用的深度学习神经网络模型,并结合海洋信息探测要素,对温度、盐度、风场、有效波高和海冰等进行了海洋环境信息因子的预测分析;同时,对船舶、溢油和涡旋等进...     

Comparison of theoretical and experimental wall pressure wavenumber-frequency spectra for axisymmetric and flat-plate turbulent boundary layers

The measurement and analysis of turbulent boundary layer wall pressure fluctuations using a wavenumber filter of sensors provide quantitative knowledge of turbulence physics. In addition, the sources of flow-induced noise and vibration for towed SONAR arrays can be determined. An axisymmetric turbulent boundary layer can have significantly different features than those of a comparable flat-plate boundary layer. Here, a detailed comparison of the distribution of wall pressure energy in both wavenumber and frequency between flat-plate and thick axisymmetric boundary layers is presented. The background theory of wavenumber-frequency spectra and state-of-the-art models for flat-plate boundary layers are discussed. The widely used model of Chase (1987), valid for flat-plate boundary layers over a wide range of Reynolds numbers, is used and combined with a sensor response function to allow the effects of spatial averaging to be considered. It is demonstrated that when measured boundary layer parameters for the axisymmetric case are used in the Chase flat-plate model, the results accurately predict the axisymmetric boundary layer wall pressure measurements.     

近海工程环境应用中各种风资料的平均时间分析

本文从近海工程设计应用的需要出发，对于通常使用的不同来源的测风资料平均时间进行了分析，这些资料来源包括：岸边及近海探查与生产设施上的气象台站、天气观测船、浮标、商船气象报、从受灾情况估计出的极大风速以及动力诊断模型估计出的海面风速。     

深海半潜浮式生产平台关键理论与技术问题

深海半潜浮式生产平台FPU(floating production unit)是国际海洋油气资源开发的关键基础性装备。针对半潜浮式生产平台的技术特点,系统阐述其各方面特性(包括:总布置、系泊和立管、水动力性能、结构设计与分析等)及相关研究现状和未来发展趋势。并结合我国南海地理、水文和资源环境等特点,对未来半潜浮式生产平台的开发提出了一些建议。     

Estimation of sea-bed conductivity and its influence upon velocity measurements with towed electrodes

A formula to determine an effective electric conductivity of channel-bed from measurements of water velocity, cross-channel potential difference and electric current-density is presented. The effective conductivity defined in this paper is the conductivity averaged over depth from channel-bed surface to a depth of the order comparable to a breadth of the channel. Effective conductivities for the Izu Island region and the Straits of Tsugaru are estimated as 2.2×10^–2 mhos/m and 6.0×10^–2 mhos/m, which are considerably large and very large, respectively, in comparison to most of those determined for several regions near England. High conductivities for these regions are consistent with the distribution of underground conductivity anomaly deduced from that of geomagnetic field anomaly observed at the earth's surface in Japan. An influence of underground conductivity upon measurements of sea surface water velocity with towed electrodes is estimated for the regions.     

Peculiarities of distribution of oil polution in the Southeastern Baltic by satellite data and in situ measurements

The results of satellite monitoring of oil pollution of the sea surface and field measurements of the concentration of oil products in the water column and bottom sediments for the first time allowed the establishment of a relation between the surface pollution from ships and the general characteristics of spatial and temporal distribution of oil products in the Southeastern Baltic Sea. Areas with increased concentrations of oil products in the surface and bottom layers were determined in the southeastern Baltic Sea. The basic directions of pollution spread, which are consistent with the main direction of annual mean transport of substances in the Gdansk Basin, are determined.     

Vertical distribution of giant jellyfish, <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> using acoustics and optics

Nemopilema nomurai jellyfish, which are believed to complete their development in the East China Sea, have started migrating into the Yellow Sea in recent years. We obtained biomass estimates of this species in the Yellow Sea using bottom trawl fishing gear and sighting surveys over a 5-year period. These methods are effective for obtaining N. nomurai jellyfish density estimates and information about the community distribution near the bottom or surface of the sea. To verify the vertical distributions of giant jellyfish between, we used hydroacoustic equipment, including an optical stereo camera system attached to a towed sledge and an echo counting method with scientific echosounder system. Acoustic and optical data were collected while the vessel moved at 3 knots, from which the distribution and density of N. nomurai jellyfish were analyzed. Subsequently, the camera system was towed from a 7 m mean depth to sea level, with the detection range of the acoustic system extending from an 8 m depth to the bottom surface. The optical and acoustic methods indicated the presence of vertical distribution of 0.11³ (inds/m³) and 0.064 (inds/m3), respectively. However, the vertical distribution indicated that around 93% of individuals occurred at a depth range of 10–40 m; thus, a 2.4-fold greater density was estimated by acoustic echo counting compared to the optical method.     

Investigation on a two-part underwater manoeuvrable towed system

A hydrodynamic model of a two-part underwater manoeuvrable towed system is proposed in which a depressor is equipped with active horizontal and vertical control surfaces, and a towed vehicle is attached to the lower end of a primary cable. In such a system the towed vehicle can be manoeuvred in both vertical and horizontal planes when it is towed at a certain velocity and the coupling effect of excitations at the upper end of the primary cable and disturbances of control manipulations to the towed vehicle can be reduced. In the model the hydrodynamic behavior of an underwater vehicle is described by the six-degrees-of-freedom equations of motion for submarine simulations. The added masses of an underwater vehicle are obtained from the three-dimensional potential theory. The control surface forces of the vehicle are determined by the wing theory. The results indicate that with relative simple control measures a two-part underwater manoeuvrable towed system enables the towed vehicle to travel in a wide range with a stable attitude. The method in this model gives an effective numerical approach for determining hydrodynamic characteristics of an underwater vehicle especially when little or no experimental data are available or when costs prohibit doing experiments for determining these data.     

Investigation of strategies to improve the recycling effectiveness of waste oil from fishing vessels

The marine ecological environment and fishery resources can be severely polluted or destroyed by waste oil from fishing vessels if they are emitted directly into the ocean without any proper pre-treatment process. International conventions such as MARPOL 73/78 regulate waste-oil emissions and require the installation of a waste oil–water separator only for ocean-going ships of over 400 gross tons. Hence, these international conventions are not applicable to most fishing ships due to their low gross tonnages. In addition, space on most fishing vessels is too limited to allow waste-oil storage tanks or a waste oil-water separator to comply with international maritime regulations. Because a significant amount of waste oil is produced by fishing vessels around the world every day, effective strategies or measures are needed to prevent this waste oil from polluting the marine environment. This study thus investigates strategies and measures for improving the effectiveness of waste-oil collection from fishing vessels. This study found that existing procedures for the collection and treatment of waste lubricating oil on land could be applied to the management of waste oil and bilge water from fishing vessels. Sufficient oil–water separators and storage facilities for the collection of waste oil should be placed at each fishing port and shipyard. Fishermen should then be required to deliver their waste oil to these storage facilities, from where it can be transported to legal recycling companies for further treatment. In addition, fishing harbor authorities should bear definitive responsibility for monitoring the illegal dumping of waste oil and for checking the waste-oil record books of fishing vessels. Each maritime country should enforce relevant laws and regulations to reduce the emission of waste oil from fishing vessels into the ocean.