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Turbulent energy cascade and intermittency are very important properties in marine fluid flows and it has become an interesting field in physical oceanography research. To quantitatively characterize that how the turbulent dissipated energy are distributed among the various scales of motion and examine the different physical processes occurring on these different time scales, we propose a quantitative...
Marine water quality monitoring and subsequent management require to know when a specific event like harmful algae bloom may occur and which environmental conditions and pressures lead to this event. So, event detection and its dynamic understanding are crucial to adapt strategy. An algorithm is proposed to identify curves mixture and their dynamics features — initiation, duration, peaks and ends...
The thrust performance of propeller during underwater recovery process of Automatic Underwater Vehicle (AUV) is analyzed based on numerical simulations in this paper. In the AUV recovery process, AUV approaches a cone-shaped dock, and the thrust performance of propeller is influenced obviously by the gap flow between AUV and dock. The purpose of this paper is to exploit the thrust performance of propeller...
An autonomous sensor platform powered by a benthic microbial fuel cell (BMFC) has been developed and deployed to supply hourly dissolved oxygen (O2), temperature and conductivity measurements from a remote location in the core of the oxygen minimum zone of the northeast Pacific. The platform uses a compact acoustic modem to both store and transmit sensor and energy harvesting measurements. Initial...
This paper addresses the problem of localizing and tracking a surface or underwater vessel with the technique called as Hausdorff Distance. Two proposed approaches, based on TDOAs comparison, were used for 2-D localization, in range and depth, with one sensor only, and have been successfully applied to localize a motionless unknown target in a tank's experiment. Results in terms of the localization...
This work addresses a data driven approach which employs a machine learning technique known as Support Vector Regression (SVR), to identify the coupled dynamical model of an autonomous underwater vehicle. To train the regressor, we use a dataset collected from the robot's on-board navigation sensors and actuators. To achieve a better fit to the experimental data, a variant of a radial-basis-function...
In-stream tidal power turbines are becoming increasingly popular. In order to develop, test and realise tidal power stations that utilise strong ocean currents, test sites with suitable velocities and facilitated infrastructure should be developed. Finding new test sites for in-stream tidal current turbines is therefore an area of ongoing research. A combination of tides and river discharges causes...
During the past decades, multi-robot systems have been studied deeply and have demonstrated their advantages in conducting autonomous missions, particularly in underwater environment. When using multiple robots, high cost single sensor can be replaced by many coordinated low cost sensors, such as optical sensors used in our work for acquiring relevant data and coordinating the fleet of robots. In...
Ocean Thermal Energy Conversion (OTEC) is one of ocean renewable energy production technologies which exploits temperature difference between surface ocean water and deep ocean water to generate electric power. In Japan, demonstration and commercial scales of 1MW-100MW OTEC plants are being planned. Since the OTEC plant necessitates large flows of ocean water, it is important to investigate environmental...
Long-term time series of high frequency sampled sea level data collected in the Port of Genoa are analyzed to investigate the sub-daily variability. Spectral analysis evidences a well developed energy peak on 20–30 minutes band. Oscillations on this frequency band, the so-called meteo-tsunami, are an almost frequent feature in the analyzed signal. Their amplitudes are generally of few centimeters...
Vessel Monitoring Systems (VMS) provide trajectory data of fishing vessels to discover the spatial-temporal pattern of fishing activities. Although previous researches exhibit the fishing resource distribution in space and time, the information on vessel sailing activities traveling from one fishing region to another are lost. These kinds of activities indicate the link relationships among fishing...
In this paper, inner tension distribution of fiber optic cable spool for underwater communication in winding process is studied which adopts the structure design of end plates on both sides. We consider the axial compression force of the cable caused by the structure limitation of the end plates on both sides, analyze the force of the cable and the end plate, study on the relationship between radial...
Silicon Photomultipliers (SiPMs) have recently been recognized as an interesting alternative to photomultiplier tubes (PMTs) thanks to their high sensitivity and time resolution. They can closely approach quantum-limited sensitivity in the detection of weak optical signals. Ifremer (French Research Institute for Exploitation of the Sea) and Institut Fresnel research lab have been investigating appropriate...
Accurate position estimation is a key factor in any Autonomous Underwater Vehicle (AUV) mission. Generally, Inertial Navigation System which estimates the position and orientation by means of dead reckoning are employed by AUVs to provide location information. Inertial navigation is most accurate when the vehicle is traveling close to the sea bottom and the Doppler Velocity Log can acquire a bottom...
As an underwater detection sensor, side-scan sonar plays an important role in marine survey, mineral exploration, underwater archaeology and so on. During the use of side-scan sonar, classifiication and mosaicking of collected images is essential in most cases. There are two main contributions in our work. On the one hand, we propose a supervised learning method based on kernel-based extreme learning...
A Close-form solution of spatial coherence for collinear sub-arrays in spherically isotropic noise is proposed in this paper. By utilizing beamforming techniques, sub-array outputs can be expressed in a combination of the fixed weight vector, the steering vector and the frequency domain sequence received by the first sensor. Then the formulations of the power spectrum density and cross-power spectrum...
The delay-and-sum beamforming method (DAS) is robust, as a consequence, it is widely used in the underwater array signal processing. However, the array gain of the DAS method is limited, and is restricted to the array aperture. To tackle this problem, we propose a DAS method based on the diagonal reducing method in the data covariance matrix. Firstly, a reducing value is subtracted from the diagonal...
In order to detect and locate a receiver relative to a grid of transmitters in an underwater environment, it is necessary to detect each signal emitted by each transmitter and estimate its Time Of Arrival (TOA) and estimate the position through triangulation. The choice of the signals and their modulation is then crutial to have a good estimation of the TOA and reduce false alarms. This paper focuses...
High-frequency (HF) ground wave radar's over-the-horizon property can effectively overcome the restraints posed by the curvature of the earth. HF radar transmits low-power radar waves and its detection distance is up to several hundred kilometers. However, radar in HF bands may be easily contaminated by noise, which has temporal and spatial variability, and ionospheric interference, limiting system...
The explosive growth of the underwater images make the demand for automatic accurate object detection more and more urgent. In this paper, we introduced a deep but lightweight neural network to detect fishes. It achieved the state-of-the-art accuracy for fish detection on the dataset of ImageCLEF, which includes 24,277 fish images belonging to 12 classes. Compared with the common used detection network,...
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