Research for enhancing the precision of asymmetrical SBL system for any vessels

The SBL system (Short Baseline System) is usually utilized by offshore working vessels when performing its underwater orientation task so as to facilitate the exploitation of abundant benthal resources, therefore, the precise distance between the vessel and underwater targets for SBL system's estimation module are highly emphasized. However, hydrological data cited in the SBL system's estimation module is not real-time information and is difficult to accurately measure, which causes the calculation errors. Studies with regard to symmetrical SBL system are carried out by most of the researchers these days, yet research in this text shows the advantage to the asymmetrical SBL system's sensor on the vessel's bottom to be installed at discretion to measure and calculate the position. In addition to the locus equation used in the traditional position calculation, Haussiam Elimination, Cramer's rule, 3D geometry relation theory as well as substitution corrections applied to this asymmetrical SBL system to educe the correction for relative geometrical position between the underwater beacon and the sensor on the ship bottom. Through numeric simulation analysis, this SBL system is proved to be a high precision acoustic positioning system based on its quick correction and high precision position calculated by the asymmetrical SBL system established in this study.     

Target Deployment and Retrieval Using JIAOLONG Manned Submersible in the Depth of 6600 m in Mariana Trench

China''s 7000 m manned submersible JIAOLONG carried out an exploration cruise at the Mariana Trench from June to July 2016. The submersible completed nine manned dives on the north and south area of the Mariana Trench from the depth of 5500 to 6700 m, to investigate the geological, biological and chemical characteristics in the hadal area. During the cruise, JIAOLONG deployed a gas-tight serial sampler to collect the water near the sea bottom regularly. Five days later, the sub located the sampler in another dive and retrieved it successfully from the same location, which is the first time that scientists and engineers finished the high accuracy in-situ deployment and retrieval using a manned submersible with Ultra-Short Base Line (USBL) positioning system at the depth more than 6600 m. In this task, we used not only the USBL system of the manned submersible but also a compound strategy, including five position marks, the sea floor terrain, the depth contour, and the heading of the sub. This paper introduces the compound strategy of the target deployment and retrieval with the practical diving experience of JIAOLONG, and provides a promising technique for other underwater vehicles such as manned submersible or Remote Operated Vehicle (ROV) under similar conditions.     

Distribution and cycling of dimethylsulfide in surface microlayer and subsurface seawater

Laboratory experiments, along with in situ investigation in Funka Bay, Japan, were conducted to determine the enrichment factor (EF) of dimethylsulfide (DMS) in the sea surface microlayer, as well as its the production and consumption rates. The EF of DMS in the microlayer was largely affected by various factors including sampling methods, sampling thickness, temperature, salinity, and DMS concentration in bulk water. In all cases but the sealed system, a part of DMS in the microlayer was always unavoidably lost during sampling. High temperature, great wind speed, and slow sampling would increase the extent of loss of DMS due to volatilization. In the field, the screen-collected samples usually exhibited greater microlayer enrichment for DMS than the plate-collected samples, showing that the screen sampler might be more effective for collecting the in situ microlayer DMS. The production and consumption rates of DMS in the surface microlayer were higher than those in the bulk water and these two rates were significantly correlated with the microlayer DMS concentrations. Moreover, the EF of DMS appeared to be related to the microlayer production rate of DMS, providing evidence supporting the observed DMS enrichment in the microlayer. The DMS production and consumption rates were not directly related to its concentrations in the bulk water, suggesting that the processes of production and consumption of DMS were very complex. In the surface microlayer, the biological turnover time of DMS varied from 0.4 to 1.9 days, with an average of 0.9 days, which was about 540-fold greater than the mean DMS sea–air turnover time (2.4 min). Thus, the biological process occurring within the microlayer can be neglected when we consider the sea–air exchange of DMS. Considering the microlayer production rate of DMS (an average of 9.7 nM day⁻¹) to be too small to counteract the sea-to-air removal of DMS, the main source of DMS in the microlayer appears to be through vertical transport by turbulent diffusion from the underlying water.     

Autonomous underwater vehicles - challenging developments and technological maturity towards strategic swarm robotics systems

ABSTRACT

Reliable power supply, precise position determination and effective communication are the key requirements for strategic autonomous underwater vehicles (AUV) involved in long duration scientific missions, search operations and when operated as a swarm. The paper presents the challenging range of AUV developed for deep water, Polar and intervention applications; demanding technical requirements for strategic AUV; reliability modeling done on the lithium-ion batteries to identify the redundancy requirements for achieving near-zero failures; navigation model to estimate the achievable level of position accuracies using the state-of-the-art navigation system; limitations in underwater communication; and their importance in realizing vehicle autonomy and swarm intelligence. It is identified that a strategic grade Doppler velocity- aided inertial navigation system could provide position accuracies of about 0.5% of the distance travelled when navigated using sea bottom or ice reference, and a 38?kWh lithium-ion battery pack requires about 7% redundant battery capacity to achieve a failure probability of <?1% in a period of 1 year.     

Observations of shallow layering utilizing the Pingerprobe echo-sounding system

A “Pingerprobe” is a system of echo sounding in which the sound source is placed near bottom to improve resolution by restricting the area investigated. It is demonstrated that a commercially available 12-kHz “pinger” with a synchronized shipboard receiver is useful not only in the monitoring of the positioning of a bottom or near-bottom instrument package (such as a corer) but also in making observations on the acoustic nature of the sea floor. In rough terrain the Pingerprobe has measured stratified sediments in some places where the PDR (Precision Depth Recorder) cannot. Observations on proximal abyssal plains indicate that the prolonged echo character common to these areas may result from small-scale roughness or inhomogeneity. When a suspended instrument is sent to the bottom in rough terrain, or in areas of intermittent subbottom reflections, use of a Pingerprobe improves information about the conditions at the point of contact and permits selection of the desired topographic setting.     

海上风电工程结构安全监测体系框架设计

文章针对海上风电工程结构安全监测的需求,在系统回顾了目前的主要监测现状及存在的监测难点的基础上,初步构建了水上、水下一体化安全监测体系基础框架,阐述了主要的工作流程,重点探讨了海上风电工程安全监测中的精密单点定位（PPP）技术、高程传递、多传感器集成、精密水下定位技术、水下摄像机标校、水下三维激光点云快速建模、水下桩基全景影像与点云数据匹配、多波束与侧扫声呐数据融合等关键技术,以期为海上风电工程结构设施管控、变化监控和防灾减灾提供新的应急方案和技术支撑。     

The marine chemistry of dimethylsulfide

Dimethylsulfide (DMS) was determined in surface seawater and vertical hydrographic profiles in the Atlantic Ocean during two cruises from Hamburg to Montevideo (Uruguay), and from Miami (Florida) into the Sargasso Sea. These data cover most of the ecological zones of the Atlantic. DMS concentrations are related to the levels of marine primary production, in agreement with its release by marine phytoplankton in laboratory cultures. The vertical distribution of DMS in the euphotic zone follows that of primary production, with a maximum at or near the ocean surface and a decrease with depth. Below the level of 1% light penetration, DMS levels decline gradually, but DMS remains detectable even in the bottom waters. The mean DMS concentration in surface water is 84.4, and in deep water 3.2 ng S (DMS) 1^?1. No steep gradients of DMS exist near the sea surface on scales of centimeters to tenths of millimeters. At a drift station, DMS was observed to be diurnally variable, with an increase in concentration in the euphotic zone throughout the day. DMS is actively turned over in the surface ocean with a residence time of a few days, but it is apparently very stable in the deep sea. DMS is the major volatile sulfur compound in the ocean, and its transfer across the air-sea interface contributes significantly to the atmospheric sulfur budget.     

A Novel Mechanical Gas-Tight Sampler for Hydrothermal Fluids

A new mechanical gas-tight sampler has been designed to collect hydrothermal fluids at the seafloor. A key feature of the sampler is the novel sample valve which is pressure balanced under deep sea, and actuated by the ram on a submersible's manipulator. The sampler is designed to be deployed at the seafloor 3000 m underwater and can be used to sample hydrothermal fluid with temperature up to 400degC. Compressed gas is used to compensate for pressure reduction of sample fluids. Simulation of the flow system was conducted to estimate the fill rate. The sampler has been tested successfully in the first Sino-American Cooperative Deep Submergence Project from August 13 to September 3, 2005.     

Display of acoustic reflection profiles using a dot matrix plotter

Acoustic reflection profiling data display is traditionally done with the aid of a facsimile type of recorder. It is not uncommon to record the unprocessed acoustic data on a tape recorder for subsequent playback through a laboratory computer. This still involves the use of some sort of facsimile recorder for the ultimate display of profiles. This paper presents the results of a study to adapt a high-speed digital dot matrix plotter for the ultimate display in place of the conventional facsimile recorder. Because a minicomputer drives the display directly, a host of signal conditioning procedures are permitted, with the final display being generated in real time. Algorithms are developed to control the marking density, allow adaptive threshold control, bottom tracking, automatic gain control, and de-emphasis of water column boundary reverberation. These techniques are just a few of the many that can be employed since the computer can readily be carried on a large ship in deep water, or a small vessel in a harbour. Shallow water is the difficult case for high energy acoustic sources because the water column boundaries behave much like an excited acoustic cavity. For this reason, a section of seismic profile is shown which was obtained with a 7·5 kHz pinger in only 8 m of water in Narragansett Bay. This research was partiallysupported by the Division of Computer Research of the National Science Foundation.     

单元管件灌浆卡箍的吊装及安装设计研究

针对用于单元管件的非自应力灌浆卡箍和膨胀式自应力灌浆卡箍,讨论了灌浆卡箍水下安装的几个吊装和安装设计问题。首先介绍灌浆卡箍水下安装的总体设计及其安装步骤;然后进行了下水吊装时保持卡箍进浆口在下、出浆口在上的姿态分析和设计,计算出了合适的吊装悬挂距离;对帮助卡箍两瓣自动包拢受损管件的一个辅助闭合机构进行了力学分析和液压系统设计;介绍了卡箍对中及端部密封装置的工作原理;最后介绍了卡箍安装的海上试验情况,列出了各工序安装时间。为灌浆卡箍水下安装技术走向实际工程应用提供了设计和试验经验。     

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.     

Ocean bottom seismograph

The ocean bottom seismograph described in this paper has been developed primarily for recording earthquakes on the mid-oceanic ridges. The instrument is suitable for dropping onto the most rugged areas of the ocean floor. Acoustic tracking with the ship's precision echo sounder enables it to be located there relative to both the topography of the sea bed and the ship. The outputs of a 3-component seismometer and a hydrophone are recorded in FM form on a low-power magnetic tape recorder designed specifically for the instrument.     

Precise Positioning of Ocean Bottom Seismometer by Using Acoustic Transponder and CTD

We have obtained precise estimates of the position of Ocean Bottom Seismometers (OBS) on the sea bottom. Such estimates are usually uncertain due to their free falling deployment. This uncertainty is small enough, or is correctable, with OBS spacing of more than 10 km usually employed in crustal studies. But, for example, if the spacing is only 200 m for OBS reflection studies, estimates of the position with an accuracy of the order of 10 m or more is required.The determination was carried out with the slant range data, ship position data and a 1D acoustic velocity structure calculated from Conductivity–Temperature–Depth (CTD) data, if they are available. The slant range data were obtained by an acoustic transponder system designed for the sinker releasing of the OBS or travel time data of direct water wave arrivals by airgun shooting. The ship position data was obtained by a single GPS or DGPS. The method of calculation was similar to those used for earthquake hypocenter determination.The results indicate that the accuracy of determined OBS positions is enough for present OBS experiments, which becomes order of 1 m by using the DGPS and of less than 10 m by using the single GPS, if we measure the distance from several positions at the sea surface by using a transponder system which is not designed for the precise ranging. The geometry of calling positions is most important to determine the OBS position, even if we use the data with larger error, such as the direct water wave arrival data. The 1D acoustic velocity structure should be required for the correct depth of the OBS. Although it is rare that we use a CTD, even an empirical velocity structure works well.     

水下机器人运动的S面控制方法

由于水下机器人的强非线性以及系统存在不确定性，同时考虑到港湾环境下水声的噪声大，因此，水下机器人进行精确作业时的运动控制一直是其实用化过程中困扰人们的问题，通常水下机器人的控制方式有PID控制器，神经网络控制器和模糊逻辑控制器三种，但是，由于这三种方法在实际应用中都存在一些参数难以确定的缺陷，为了解决这一问题，本文从模糊逻辑控制方式出发，借鉴PID控制的结构形式，推导出一种全新而简单有效的控制方法，定义为S面控制法，从水下机器人的水池试验和海上实验来看，不论是定点的控制精度还是运动过程中的控制效果都较令人满意，尤其是在风浪，潮流都比较大的海上实验中得到验证，鲁帮性很好。     

Dimethyl sulfide in the atmospheric surface layer of the Equatorial Pacific Ocean

This paper reports a case study of atmospheric stability effect on dimethyl sulfide(DMS) concentration in the air. Investigation includes model simulation and field measurements over the Pacific Ocean. DMS concentration in surface sea water and in the air were measured during a research cruise from Hawaii to Tahiti. The diurnal variation of air temperature over the sea surface differed from the diurnal cycle of sea surface temperature because of the high heat capacity of sea water. The diurnal cycle of average DMS concentration in the air was studied in relation to the atmospheric stability parameter and surface heat flux. All these parameters had minima at noon and maxima in the early morning. The correlation coefficient of the air DMS concentration with wind speed (at 15 m high) was 0. 64. The observed concentrations of DMS in the equatorial marine surface layer and their diurnal variability agree well with model simulations. The simulated results indicate that the amplitude of the cycle and the mean     

Effects of acoustic alarms, designed to reduce small cetacean bycatch in gillnet fisheries, on the behaviour of North Sea fish species in a large tank

World-wide many cetaceans drown incidentally in fishing nets. To reduce the unwanted bycatch in gillnets, pingers (acoustic alarms) have been developed that are attached to the nets. In the European Union, pingers will be made compulsory in some areas in 2005 and in others in 2007. However, pingers may effect non-target marine fauna such as fish. Therefore in this study, the effects of seven commercially-available pingers on the behaviour of five North Sea fish species in a large tank were quantified. The species tested were: sea bass (Dicentrarchus labrax), pout (Trisopterus luscus), thicklip mullet (Chelon labrosus), herring (Clupea harengus), and cod (Gadus morhua). The fish were housed as single-species schools of 9-13 individuals in a tank. The behaviour of fish in quiet periods was compared with their behaviour during periods with active pingers. The results varied both between pingers and between fish species. Sea bass decreased their speed in response to one pinger and swam closer to the surface in response to another. Thicklip mullet swam closer to the bottom in response to two pingers and increased their swimming speed in response to one pinger. Herring swam faster in response to one pinger, and pout and cod (close relatives) showed no behavioural responses to any of the pingers. Of the seven pingers tested, four elicited responses in at least one fish species, and three elicited no responses. Whether similar responses would be elicited in these fish species in the wild, and if so, whether such responses would influence the catch rate of fisheries, cannot be derived from the results of this study. However, the results indicate the need for field studies with pingers and fish. Based on the small number of fish species tested, the present study suggests that the higher the frequency of a pinger, the less likely it is to affect the behaviour of marine fish.     

Dimethylsulphide and dimethylsulphoniopropionate in Antarctic sea ice and their release during sea ice melting

This study presents concentrations of dimethylsulphide (DMS) and its precursor compound dimethylsulphoniopropionate (DMSP) in a variety of sea ice and seawater habitats in the Antarctic Sea Ice Zone (ASIZ) during spring and summer. Sixty-two sea ice cores of pack and fast ice were collected from twenty-seven sites across an area of the eastern ASIZ (64°E to 110°E; and the Antarctic coastline north to 62°S). Concentrations of DMS in 81 sections of sea ice ranged from < 0.3 to 75 nM, with an average of 12 nM. DMSP in 60 whole sea ice cores ranged from 25 to 796 nM and showed a negative relationship with ice thickness (y = 125x^− 0.8). Extremely high DMSP concentrations were found in 2 cores of rafted sea ice (2910 and 1110 nM). The relationship of DMSP with ice thickness (excluding rafted ice) suggests that the release of large amounts of DMSP during sea ice melting may occur in discrete areas defined by ice thickness distribution, and may produce ‘hot spots’ of elevated seawater DMS concentration of the order of 100 nM. During early summer across a 500 km transect through melting pack ice, elevated DMS concentrations (range 21–37 nM, mean 31 nM, n = 15) were found in surface seawater. This band of elevated DMS concentration appeared to have been associated with the release of sea ice DMS and DMSP rather than in situ production by an ice edge algal bloom, as chlorophyll a concentrations were relatively low (0.09–0.42 μg l^− 1). During fast ice melting in the area of Davis station, Prydz Bay, sea ice DMSP was released mostly as extracellular DMSP, since intracellular DMSP was negligible in both hyposaline brine (5 ppt) and in a melt water lens (4–5 ppt), while extracellular DMSP concentrations were as high as 149 and 54 nM, respectively in these habitats. DMS in a melt water lens was relatively high at 11 nM. During the ice-free summer in the coastal Davis area, DMS concentrations in surface seawater were highest immediately following breakout of the fast ice cover in late December (range 5–14 nM), and then remained at relatively low concentrations through to late February (< 0.3–6 nM). These measurements support the view that the melting of Antarctic sea ice produces elevated seawater DMS due to release of sea ice DMS and DMSP.     

Mosaic-based navigation for autonomous underwater vehicles

We propose an approach for vision-based navigation of underwater robots that relies on the use of video mosaics of the sea bottom as environmental representations for navigation. We present a methodology for building high-quality video mosaics of the sea bottom in a fully automatic manner, which ensures global spatial coherency. During navigation, a set of efficient visual routines are used for the fast and accurate localization of the underwater vehicle with respect to the mosaic. These visual routines were developed taking into account the operating requirements of real-time position sensing, error bounding, and computational load. A visual servoing controller, based on the vehicle's kinematics, is used to drive the vehicle along a computed trajectory, specified in the mosaic, while maintaining constant altitude. The trajectory toward a goal point is generated online to avoid undefined areas in the mosaic. We have conducted a large set of sea trials, under realistic operating conditions. This paper demonstrates that without resorting to additional sensors, visual information can be used to create environment representations of the sea bottom (mosaics) and support long runs of navigation in a robust manner.     

Locating and determining the orientation of underwater research equipment: Acoustic range and range rate data

A formulation is presented for evaluating the performance of acoustic data systems to determine the location and orientation of underwater research apparatus. The variables to describe the position of the underwater research apparatus are referenced to a surface ship, and represent the straight-line distance from the stern of the ship to a point on the apparatus (R), the angular distance down from the sea surface (Phi), and the angular distance from the direction of motion of the ship (Theta). The three orientation variables on the apparatus are the angle between thezandz'axes (i), the angle between thexandx'axes in thex'-y'plane (Omega), and the angle which locates thex'axis in thex'-y'plane (omega). A simple model for the sound velocity variation with depth is included in the range data analysis, while the Doppler data are shown not to need that further complication in the analysis. An error model is constructed and applied to three geometries which represent common underwater research devices. Accuracy goals for possible applications of these devices are discussed, and performance requirements for an acoustic system which would meet the goals are derived.