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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...
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...
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...
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...
This paper explores the incorporation of false positives and Bayesian updates into the framework of optimal search. Optimal search is an open-loop optimal control framework developed by the US Navy to optimize search and rescue path planning for rapid sweep sensors such as sonar. Although useful as a pre-planning tool, this framework lacks features necessary for online planning, such as quantification...
Marine towed electrical resistivity survey is widely used for various purposes such as underground resources exploration, coastal engineering, archaeological detection, and UXO detection. To improve data quality and resolution, we propose enhanced in-house developed marine towed electrical resistivity survey system. First, hollow-type carbon fiber submersible electric field sensors were developed;...
Underwater acoustic sensor network (UWASN) can gather the ocean data such as temperature, salinity, pH, turbidity and dissolved oxygen etc. with the help of underwater sensor nodes. Using the underwater surface gateway, underwater sensor nodes forward the ocean data to terrestrial network for the analysis. These techniques can be used to detect the water-borne disease causing areas. Water-borne diseases...
The Ocean Observatories Initiative (OOI) is directed to operate and maintain arrays of moored and mobile assets in six locations around the globe. These locations include two coastal arrays off of the east and west coasts of the United States and four global arrays in the Southern Ocean, Argentine Basin, Irminger Sea, and North Pacific. These arrays are currently operational, supplying oceanographic...
Underwater sound source position is determined using a line array. However, performance degradation occurs owing to a multipath environment, which generates incoherent signals. For this reason, the system needs advanced signal processing such as high-resolution beamforming. In this paper, a hydrophone array is proposed for position estimation robust to a multipath environment using generalized cross-correlation(GCC)...
This work aims to study a new energy harvesting device to be anchored on the ocean floor and convert any type of currents, tides or oscillation movement into electrical energy using linear electromagnetic generators. The final application is to supply energy to a set of moored monitoring sensors that collects data and allowing the system to be energetically autonomous. The proposed setup is a spherical...
Acoustic wave interacts with submerged cylindrical shell to excite object resonance and then object reradiates acoustic wave into surrounding water. The backscattering field can be divided into two major parts: elastic echoes, which are produced by object resonance and the background field is composed of specular reflection echoes. Furthermore, specular echo is quite similar to the incident signal,...
Coherent-on-Receive X-band marine radar system was developed with the aim to map the nearshore surface current that responsible for sediment transportation in the coastal zone. In order to evaluate the performance of this land-based remote sensing system and to validate the data, in-situ measurement of the surface velocities over the domain that covers from the surf-zone to the inner-shelf are required...
We have developed a novel method to measure the absolute gain patterns of radar antennas that have elongated shapes such as marine, airborne, and coastal radars. This method requires an inexpensive and simple apparatus consisting of a turntable, a probe antenna, and a vector network analyzer. In addition, the measurement using this method can be done in high speed (a few minutes) at short distance...
The exploration of buried deposits under the sea sediment requires high directivity and low attenuation beams. The parametric sub-bottom profiler meets these requirements; moreover, it is comparatively small and can be easily mounted on autonomous underwater vehicles (AUVs). For this reason, we are developing a new PSBP system for AUVs. This paper presents the recent results of the PSBP system for...
A VHF pulse radar was used to observe the sea surface in the northern Taiwan Strait. Radar frequency is 52 MHz, and a range cell was 300 m. Four vertical dipole antennas, arranged linearly along the coastline with 3 meter separation between adjacent antennas, were used to collect the radar returns. The self-adaptive Capon method was employed in this study to determine the direction of arrival (DOA)...
This paper describes the application of a Dual Accelerometer Vector Sensor (DAVS) for the discrimination between the bottom reflections, the source direct arrival and the source ghost or multipath in an unconventional seismic acquisition scenario. The realisation of the DAVS device and the seismic acquisition scenario described in this paper, were carried out in the scope of the WiMUST project, an...
Phased array HF radars are widely used for mapping surface currents and wind directions at high resolution in time and space. The beam is formed using simple physical optics principles that produce sidelobes. Several authors have alluded to errors produced in the measurements by sea echo energy in the sidelobes. Here we simulate the effect of sidelobes in surface current and wind direction measurements,...
Eelume signifies a leap in subsea robotics capabilities. It is a modular, flexible robot capable of swimming like a snake, or being propelled by conventional thrusters. Eelume is designed to reside subsea to provide immediate response to unpredicted inspection, maintenance and repair (IMR) requirements.
This article describes the deployment of a passive acoustic monitoring (PAM) array from the AutoNaut wave-propelled unmanned surface vessel (USV). It highlights inherent challenges to be overcome by this new technology for the application and details the development of a suitable system.
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