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The recognition of places by using visual information in underwater environments is important when performing autonomous robotic exploration of the same area at different periods of time. It helps the robot to know its location and take decisions accordingly. However, vision-based recognition of underwater places can be a very challenging task due to the inherent properties of this kind of places...
In order to overcome the low-efficiency and low-accuracy of present manual demarcation method for the sub-bottom layers, an automatic demarcation and extraction method based on sediment quality factor and peak-trough on the echo energy loss level curve was proposed. Firstly, the original SEGY file from sub-bottom profile (SBP) was decoded and the amplitude data of each trace was transformed to echo...
In this paper, we propose a statistical channel model to study the performance of a line-of-sight underwater wireless optical communication (UWOC) link in a data mulling environment. We optimize the range of geometric parameters including detector aperture diameter and field-of-view (FOV) to reduce the effect of excessive scattering on the optical signal. By considering geometric losses, we observe...
We have been developed a radar for radial Doppler velocity measurements: a standard marine radar modified to coherent-on-receive capability (CORrad). It measures the intensity and the radial velocity component of the radar echo. The latter can be used to generate orbital wave velocity spatial maps of ocean waves, as well as the mean radial ocean surface velocity when sequences of map images are summed,...
We present results from a series of tracer dye experiments where ocean plume concentration is measured using unmanned surface vessels. The goal of the study is to characterize the fine-scale spatiotemporal plume structure which is used for developing and evaluating autonomous robotic sampling strategies. We present a description of the qualitative characteristics of experimentally generated marine...
During the launching of the AUV especially in air-launching, the water entry problem is inevitable. The AUV will stir the flow field of surrounding fluid during the moving into water, while the fluid will act a strong force on the AUV in return, which may cause trajectory deflection problems or damage to their structure and inner components in severe cases. The water entry experiment of full-size...
In this paper, a time reversal technique is proposed to enhance detection performance. When the time reversal technique is applied to the response of the clutter with strong time varying characteristic of shallow water, it is hard to obtain a high peak response. However, in the case that a cylindrical object is placed on the seafloor, However, in the case that a cylindrical object is placed on the...
Alaska's coastal waters exhibit a rich variety of sea-level fluctuations, driven by multiple processes and encompassing a wide range of timescales. Water level data from a set of stations along the Alaska coast are examined from different perspectives to isolate portions of the variability with different periods or subranges of timescales. The approach is exploratory, addressing selected aspects of...
In this paper, we present a novel approach for the sensing of erosive cavitation phenomena in underwater facilities. Cavitation phenomena are known for their destructive capacity of underwater structures and are caused by the pressure decreasing followed by an implosion when the cavitation bubbles find an adverse pressure gradient. Conventional cavitation detection techniques are based on passive...
This article presents a new water strider-like robot with buoyancy as the supporting force that is inspired by the water strider which can stand, glide and leap on the surface of water. The stroke mechanism of the robot has little disturbance to the water and is favorable for the stability of the water strider-like robot without extra action when it enters and leaves the water surface. Based on Interaction...
An increasing water to oil ration in the North Sea oil and gas production motivates for an optimization of the current deoiling facilities. Current facilities are operated on matured methodologies, which in most cases fulfill the government regulations. However, it has also observed that these solutions could be further improved. In order to more precisely monitor the deoiling operations, this study...
Rapid technical advancement has seen a move away from more traditional methods of mine clearance operations such as the use of divers in favour of using unmanned and remote vehicles. Remotely Operated Vehicles (ROVs) are now used extensively in offshore and military operations for complex inspection tasks where Dynamic Positioning (DP) software is used to reduce operator workload and provide stability...
A current trend is autonomous transport of goods and people in the air, at land, and at sea. For safe and reliable operations, autonomous systems require sensors that replace, or even exceed, the senses of a human operator. A system of spatially distributed inertial measurement units (IMUs) along the hull of a vessel, which allows sensing of local accelerations of a vessel or structure at sea is proposed...
In this work we are describing a multi-modal short-range navigation system for precision positioning tasks such as docking of a robotic vehicle in 3d space. The two input modalities, a monocular camera tracking a visual marker and an array of 3-axis magnetometers tracking a magnet, were chosen to cover a wide range of environmental conditions in order to increase the versatility and robustness of...
This paper introduces an underwater wheeled vehicle towing system which is composed of an anterior traction winch, a posterior brake winch, wire rope and fixed pulleys. Under the coordinate driving of two winches which one draw in the cable while another one let out the cable, the wheeled vehicle can be towed to achieve the accelerating, uniform speed and decelerating movement on the track which is...
In autonomous mapping surveys the autonomous underwater vehicle (AUV) cannot rely on receiving position aiding from a surface vehicle or any other external infrastructure. The AUV can however use any payload sensor to restrict the position error drift in the navigation system. In this paper we consider how to use the terrain in a pre-surveyed baseline to bound the drift in the estimated AUV position...
Podded propeller (POD) has been developed recently as a new type of propulsion system. It is composed of a pod body, a propeller, and a strut. This propulsion system can save cabin space, reduce vibration of the main engine, increase propulsion efficiency, and improve the ship maneuverability. This study verifies the reliability of computational fluid dynamics (CFD) for calculating the hydrodynamic...
An Arctic-capable coastal geomorphic change model was developed based on the open-source coastal geomorphic change model, Xbeach. In this paper, we describe an approach to make the 2D version of the Xbeach model Artic-capable by adding a heat transfer module which computes the temperature and the phase of the sediment and water (frozen or unfrozen). During execution of the overall model, the conventional...
One of the challenges for tsunami detection by HF radar is to make a first detection at the longest range possible from the shore in order to maximise the warning time for civil responses. A signal-to-noise advantage is obtained by using a dynamic filter in software to lock onto the Bragg spectral lines in mid-range of the radar, and track the Bragg lines into more distant ranges by dynamically changing...
Field measurements of turbulence are presented for a proposed current energy converter site near Kuchinoshima Island. The site was selected for its suitability to harness the energy of the Kuroshio Current. The measurements are analyzed focusing on the engineering aspects. Turbulence is known to effect the performance and working life of turbines due to fatigue so its characteristics are important...
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