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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...
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...
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...
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...
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,...
Underwater gliders are widely used in ocean survey operations due to their unique capability of long-range cruising with low energy consumption. As a critical technique, accurate attitude control is challenging due to the highly nonlinear, heavily coupled system model of an underwater glider with uncertain hydrodynamic parameters and suffering from environmental disturbances. To investigate this problem,...
For Unmanned Underwater Vehicles (UUV), the problem of position estimation is crucial for many different aspects ranging from good navigation performance to suitable geo-referencing capabilities of the payload data. The possibility of accurately estimating the UUV orientation has a positive impact on it, as the most of position estimation algorithms rely on the orientation signal. Among the orientation...
This paper describes how to automatically identify Posidonea Oceanica (P.O.) from seabed images gathered by a bottom-looking camera. Different methods based on machine learning and deep learning algorithms are presented and compared. On the one hand, texture descriptors and co-occurrence matrices are used to characterize the images and classify the P.O. regions by means of Support Vector Machine and...
The detection of dissolved carbon dioxide (dCO2) is made possible through a colorimetric effect that occurs in a sensitive membrane. The reaction with dCO2 changes the pH of the membrane causing a small difference in its colour which results in a characteristic absorbance spectrum band near 435 nm. A sensing platform based on this effect was developed and tested in gaseous and in aqueous environments...
Analysis of the dynamics of coastal relief during long time scales allows us to define differences and general trends in the evolution of different coastal types. Long-term dynamics of various coastal profiles was explored on the basis of cartographic data and individual field measurements for different types of sandy beaches located in the northern and northwestern coasts of the Black Sea. The variability...
This paper investigates trajectory tracking control problem for Autonomous Underwater Vehicles (AUVs) in presence of actuator dynamics constraints and a large initial tracking error or a sudden change in the desired trajectory. A new tracking control algorithm is developed by re-planning a new local trajectory. Based on the AUV's current position and the desired position after a certain interval,...
Laser ranging in a water medium is always challenging owing to the attenuation and scattering of the laser. This paper presents a correction method for laser ranging based on a laser ranging experiment in different turbidities of water. First, this paper examines the influence of water on the dynamic range and accuracy of laser ranging. Then, the effects of attenuation and scattering are eliminated...
During the engineering feasibility study period of circular synthetic aperture sonar (CSAS) design, it is necessary to establish the computer simulation model of the CSAS imaging with various sonar parameters and underwater extended targets. In this work, the TriKirch scattering model also known as the Planar elements method, which is based on the Kirchhoff approximation and triangulation of target's...
There is an urgent need among the scientific community for a better understanding of the air-sea interactions that occur during typhoons and improved accuracy in typhoon forecasting. To this end, the Institute of Oceanography at the National Taiwan University (IONTU) has developed a buoy that can measure meteorological and hydrographic conditions, and transmit the high-precision data in near real-time...
Underwater object tracking is one of the most essential and fundamental tasks in ocean investigations recent years. In this paper, we try to capture multi-scale retinex (MSR) model as well as the partial least square (PLS) analysis for underwater object tracking. We first make use of multi-scale retinex model to evolve and enhance the partial color constancy from the underwater video sequences, which...
The performance of an automatic target recognition (ATR) system in the context of naval mine detection is severely affected by the underwater environment. Especially in regions with the presence of sand ripples or mine-sized stones the number of false alarms can become unacceptable high, if the detection algorithm does not account for the type of seafloor. Therefore, a robust way of discriminating...
This paper presents a concept for a heterogeneous unmanned team designed for autonomous persistent inspection of offshore wind turbines. This team consists of an unmanned surface vessel (USV) and an unmanned aerial system (UAS) operating cooperatively. We describe a concept of operations (CONOPS) in which the USV acts as a ground control station (gCS) for the UAS. The USV shuttles the UAS between...
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