The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper we present numerical simulations performed prior to the deployment of a real-time seismic buoy in the Alboran Sea (Western Mediterranean), in an active seismic area at 250–300m depth. Due to the inherent difficulties in underwater communications there are not many real time data available and the implementation of seabed seismic real time networks has been neglected for years. Our system...
In this study, we investigated the effect of water temperature inversion layer on the propagation of acoustic wave in the western coastal sea of Jeju island in April 2015. When the acoustic source and receiver are simultaneously located within the water temperature inversion layer depth, the long range propagation of acoustic wave is confirmed by numerical modeling. This is caused by the duct effect...
A study of population and distribution of plankton in the sea can be a good indicator of the health of the marine environment. Many digital images of marine plankton have been recorded. Image extraction and plankton identification can aid research of oceanic plankton. In this paper, we present a method to compute affine-invariant Fourier Descriptors (FDs) for marine plankton image retrieval. This...
The self-repairing composite materials integrated with sensing is way forward to reduce maintenance cost and increase consumer safety. In this work, the novel self-healing carbon fibre reinforced unidirectional bulk tape of simple architecture is prepared using nanocomposite film. The bulk material tape was prepared using nanocomposite film of low melting temperature polymer sandwiched between two...
This paper proposes a superdirective beamforming method for dual concentric circular hydrophone arrays based on the previously established eigenbeam decomposition and synthesis model. The optimal solutions of superdirectivity, including the optimal beampattern, the global directivity factor, and the total sensitivity function, are all decomposed into corresponding sub-solutions termed eigenbeams,...
This paper addresses the topic of target detection and tracking using a team of UAVs for maritime border surveillance. We present a novel method on how to integrate the perception into the control loop using two distinct teams of UAVs that are cooperatively tracking the same target. We demonstrate and evaluate the effectiveness of our approach in a simulation environment.
In this paper we present a 3D node deployment strategy to improve the routing performance of an Underwater Wireless Sensor Network (UWSN). This is done by carefully considering the unique characteristics of underwater acoustic communication as well as three-dimensional (3D) and dynamic nature of Underwater Wireless Sensor Networks (UWSNs). This strategy targets 3D UWSN and not only improves the routing...
The absence of the global positioning system (GPS) is a challenge to navigation and localization in the underwater environment. Thus, for precise and accurate navigation, autonomous underwater vehicles (AUVs) often rely on very precise (yet very expensive and high energy consumption) inertial strap-down sensors which require external observations to constrain their dead-reckoned position error over...
This paper investigates four methods for calculation of fixed measurement positions for acquiring knowledge about an ocean area by observation and model based analysis. The qualities and limitations of the methods, applied to a rather complicated ocean area, is studied. We investigate two methods based on covariations in ocean data; (i) an extension of the data assimilation based method by [1] with...
This study investigates the capability of camera technology and Large Scale Particle Imaging Velocimetry (LSPIV) measurement techniques to access the sea surface velocity conditions in spatiotemporal dimensions in a tidal inlet, located in the southern North Sea. LSPIV shows reliable results for various applications in riverine and hydrographic studies, nonetheless LSPIV is up to date less prominent...
The Autonomous Underwater Vehicle (AUV) will suffer severe impact load during the water entry, sometime this load may cause structural failure of AUV. In order to decrease the impact load level, a design and cushioning properties analysis of mitigator for AUV is presented in this paper. Numerical simulations based on Arbitrary Lagrangian-Eulerian (ALE) method are carried out so as to study the mitigation...
Classification of submerged objects can be performed using broadband sonar and underwater sound scattering analysis. The backscattered signals, composed of specular echo and elastic echo, have information on the submerged target, including its dimensions and material characteristics. In this study, we performed shockwave-scattering simulations of backscattered signals when a broadband shockwave (1–60...
This paper presents experimental results of coherent communications comparing the following methods of underwater channel identification applied to a time-reversal processor: pulse compression, L1-norm regularization and channel physical modeling. The first method is the Passive Time Reversal in its conventional form: a low complexity technique to mitigate intersymbol interference due to multipath...
We applied blue LEDs to the prevention of the settlement of cyprids. The relatively strong intensity of the irradiation of ca. 500 (W m−2) could prevent the settlement of cyprids on the area of the bottom of a tub, above which the light source was adjusted. On the other hand, cyprids settled on the area on which the relatively weak intensity of the irradiation, < 100 (W m−2), was reached. In the...
Renewable energy systems that extract power from sustainable sources such as wind, wave and solar can provide clean energy to a range of marine applications. Currently a major challenge is in providing an uninterrupted power supply, given the variation and uncertainty in these renewable energy sources. To deal with the unpredictable nature of renewable energy resources, this paper investigates the...
Autonomous underwater vehicles (AUVs) are used to execute an increasingly challenging set of missions in commercial, environmental and defense industries. The resources available to the AUV in service of these missions are typically a limited power supply and onboard sensing of its local environment. Optimal path planning is needed to maximize the chances that these AUVs will successfully complete...
Fouling build up is a known problem in the industry. Accumulation of fouling can occur in different structures e.g. offshore pipes, ship hulls, floating production platforms. The type of fouling that is being accumulated is dependent on environmental conditions surrounding the structure itself. Current methods that are deployed for fouling removal spans over hydraulic, chemical and manual means. Current...
This paper presents a comparison between three popular guidance laws for path following of autonomous underwater vehicles: switching enclosure-based Line-Of-Sight (LOS), lookahead-based LOS, and vector field guidance laws. The equations of motion employ the concept of the relative kinematics, and a nonlinear controller is applied together with the guidance systems during path-following. The optimal...
P2-ROV is a portable polar ROV. Designed to be transported via-helicopter and easily handled by a small team of scientists it is specially addressed to work under the shelf ice of Antarctica by exploiting the holes drilled in the ice by means of a special 350 mm auger; the shape of the vehicle reminds that of a torpedo contained in a 340 mm diameter. Highly automated, P2-ROV is designed to work in...
Remotely Operated Vehicles are very useful tools for submarine exploration. We have customized a Micro-Class ROV for shallow marine geophysical and geochemical research. Due to our specific requirements, micro-ROV frame, fairing and pressure canisters must be of lightweight, resistant and non-magnetic material. Based on its mechanical and optical properties, for the realization of the micro-ROV pressure...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.