Europe Oceans 2005最新文献

{"title":"Optimization of a data link protocol for an underwater acoustic channel","authors":"Milica Stojanovic","doi":"10.1109/OCEANSE.2005.1511686","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1511686","url":null,"abstract":"Acoustic modems typically operate in half-duplex, which limits the choice of a data link control protocol to the Stop and Wait (S&W) type. Unfortunately, on channels with poor quality and long propagation delay-such as the majority of acoustic channels-S&W protocol has low throughput efficiency. The basic S&W can be improved by using a modification in which packets are transmitted in groups and acknowledged selectively. Throughput efficiency can now be maximized by selecting the optimal packet size, which is a function of range, rate, and error probability. Quantitative analysis for typical acoustic links shows that modified S&W protocols offer good performance, provided that packet size is chosen close to optimal. In addition, as the group size increases, sensitivity to packet size selection is reduced. To ensure best ARQ performance in mobile acoustic systems where link conditions vary with time, future generation of acoustic modems must focus on adaptive selection of protocol parameters.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115663395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acoustic intensity gradient measuring and analysis equipment","authors":"I. Vasile","doi":"10.1109/OCEANSE.2005.1513252","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513252","url":null,"abstract":"The assessment of the field gradient distribution is of a great importance in the reduction of the ship's acoustic field since the early stages of the ship's design. Once the high acoustic level areas of the ship are calculated, these areas can be rigidified in order to minimize the acoustic radiation. The authors conduct a theoretical analysis of radiated acoustic energy of the ship's hull.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115736889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wave-induced drift and mixing","authors":"N. Rascle, F. Ardhuin","doi":"10.1109/OCEANSE.2005.1513147","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513147","url":null,"abstract":"Over the past 10 years, several investigations have revealed that waves dramatically enhance the turbulent mixing near the surface (e.g. Agrawal et al., 1992). Besides, waves are known to have a non-zero mean motion in the direction of propagation: the Stokes drift. In a rotating frame, waves also induce a stress to the right of the direction of propagation: the Hasselmann force or \"Stokes-Coriolis\" effect. This effect is believed to compensate the Stokes drift by driving the mean flow in the opposite direction, and recent studies have proposed that it significantly modifies the profile of the Eulerian current near the surface (Lewis and Belcher, 2004). To embrace all these effects, a model of the ocean mixed layer is proposed. The motion is separated into a quasi-Eulerian mean flow and the wave-induced Stokes drift. Sigma coordinates are used to follow the surface motion (Mellor, 2003). This yields equations for the mean flow that are compatible to those of ocean-circulation models, with the wave part acting as a supplementary forcing. A 2.5 level turbulence closure scheme is used, in which dissipation of waves enhances turbulent kinetic energy near the surface. The different effects are investigated and the model is validated with measured profiles of turbulent kinetic energy (Terray et al., 1996), shear of Eulerian currents (Santala and Terray, 1992) and Lagrangian surface drifts. The model is generally consistent with all these observation, and suggests that surface drift observations, of the order of 3% of the wind speed, must be related to a strong surface shear that mainly comes from the shear of the Stokes drift. Essentially, a strong surface mixing is incompatible with large surface shears of the quasi-Eulerian velocity. Still, the model mean water velocities are only about 60% of observed drift velocities. The model also suggests a dependence of surface mixing and drift on the state of development of the waves that can be represented by a wave age parameter. It raises the question of the adequacy of parameterisations based on the wind only, as usual in ocean circulation models. We argue for a coupled wave-circulation model, particularly for fetch limited conditions often met in coastal areas, and estimate the likely impact on upwelling-type circulations.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120945913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Technical advances in comprehensive oceanographic data management","authors":"J. Graybeal, K. Gomes","doi":"10.1109/OCEANSE.2005.1513258","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513258","url":null,"abstract":"MBARI has completed several operational releases of its new data management system, the Shore Side Data System (SSDS). SSDS is a distributed system which has been tested with data from multiple observing platforms, hundreds of instruments, and numerous software-based data sources. The SSDS architecture combines modern data standards and interfaces, an advanced yet open metadata schema, and open-source software libraries to provide flexible, expandable data management for ocean observatories. In this paper we discuss two of the key technical approaches followed for the SSDS, and analyze the operational results. The appropriateness of the selected approaches for use in observatories, institutions, and regional associations is also presented.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"397 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121003048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of objects in sea sediments and estimation of bottom parameters","authors":"M. A. Larsen, J. Hovem","doi":"10.1109/OCEANSE.2005.1511790","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1511790","url":null,"abstract":"An important objective of the SITAR project, abbreviation for \"Seafloor imaging and Toxicity: Assessment of Risks caused by buried waste,\" is to investigate various acoustic techniques for detection and classification of objects partially or completely buried in the sediments of the bottom. In this paper we report some results from in situ measurements in the Stockholm archipelago in fall 2003. A ROV is running over the bottom with an echo sounder transmitting pulses into the bottom. The pulses are short transients, with centre frequencies of 5 kHz, 10 kHz and 20 kHz. The echoes are received by hydrophones located at the same position as the transmitter, i.e. in the monostatic configuration. A partially buried object exists at the bottom. The first part of this paper will focus on detection of this target, and its appearance in the received signals for different transmitted pulse forms. The second part will focus on the appearance of the bottom in the data and estimation of bottom parameters. As a first approach the acoustic impedance of the bottom is estimated from the ratio of received to transmitted energy at the transmitter/receiver location, but corrected for geometric spreading loss in the water. It is observed a reduction of the higher frequencies in the spectra of the received signals when compared with the spectrum of the transmitted pulse. An attempt is made to explain this fact using theoretical modeling, and the results are used to obtain a roughness estimate as well as an improved acoustic impedance estimate of the bottom.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"35 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121242005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Autonomous underwater vehicle control using reinforcement learning policy search methods","authors":"A. El-Fakdi, M. Carreras, N. Palomeras, P. Ridao","doi":"10.1109/OCEANSE.2005.1513157","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513157","url":null,"abstract":"Autonomous underwater vehicles (AUV) represent a challenging control problem with complex, noisy, dynamics. Nowadays, not only the continuous scientific advances in underwater robotics but the increasing number of subsea missions and its complexity ask for an automatization of submarine processes. This paper proposes a high-level control system for solving the action selection problem of an autonomous robot. The system is characterized by the use of reinforcement learning direct policy search methods (RLDPS) for learning the internal state/action mapping of some behaviors. We demonstrate its feasibility with simulated experiments using the model of our underwater robot URIS in a target following task.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127204012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Industrial solutions for regional cabled ocean observatories","authors":"G. Waterworth","doi":"10.1109/OCEANSE.2005.1513200","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513200","url":null,"abstract":"As a result of field experience and recent activities with academic institutes, industry has developed robust and novel solutions for future generation cabled observatories. These solutions include the high availability of electrical power and data communications delivered by a combination of commercially off the shelf equipment and specialized equipment built to submarine telecommunication standards.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126869051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation of marine propulsors hydrodynamic behaviour","authors":"F. Deniset, R. Jaouen, J. Billard, J. Laurens, N. Lautrou, S. Moyne, S. Phoemspatawee","doi":"10.1109/OCEANSE.2005.1513248","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1513248","url":null,"abstract":"A numerical method is developed to assess the vibrations on rudder and pod strut due to the propeller action. The method involves both potential and RANSE (Reynolds-Averaged Navier-Stokes Equations) solvers. In unsteady state mode, amplitudes of fluctuations of hydrodynamic forces on the rudder or on the pod strut operating in the propeller slipstream are far from negligible and, depending on the configuration, frequencies of the fluctuations are not only at blade rate (BR) but also at blade rate multiples (BR/sub 4/) and at frequencies comprised between BR and RPM because the propeller is itself operating in an unsteady state mode. It is also shown how sheet cavitation developing on the propeller blades can be taken into account. Finally a finite element code can be used to complete the computation sequence.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116406652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Towards more accurate shadow modelling for simulated SAS imagery","authors":"Alan J. Hunter, M.H. Hayes","doi":"10.1109/OCEANSE.2005.1511802","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1511802","url":null,"abstract":"Shadows are a feature of particular interest in Synthetic Aperture Sonar (SAS) imagery. Shadows are cast by objects or features that are proud of the sea-floor. The shape of a shadow reveals information on the structure of the object or feature and can be used to assist in target classification. In most existing simulated imagery, the shadows are well-defined and resemble those obtained by conventional, high-frequency sonars. In practice, shadows are not well-defined or are sometimes lost in imagery obtained by low-frequency, free-towed, shallow-water SAS systems. In this paper, we show our attempts to simulate realistic SAS imagery and demonstrate some of the mechanisms responsible for the shadow degradation that is seen in practice. Our simulator uses a novel facet-based scattering model that incorporates wide-beam effects, shadowing, and multiple scattering. Using our simulator, we show that the fidelity of the shadow region is degraded by wide-beam effects, multi-path scattering from the sea-surface, and reconstruction artefacts caused by deviations from a linear tow-path.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122304420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adaptive anisotropic diffusion for speckle filtering in SAS imagery","authors":"F. Maussang, J. Chanussot, S.C. Visan, M. Amate","doi":"10.1109/OCEANSE.2005.1511730","DOIUrl":"https://doi.org/10.1109/OCEANSE.2005.1511730","url":null,"abstract":"Thanks to their high resolution, the images provided by synthetic aperture sonar (SAS) are of great interest for the detection and classification of underwater mines lying on the sea bed or buried in the sea floor. As with any acoustic imaging systems, SAS data are highly corrupted by a multiplicative noise, called the speckle, which can be very disturbing for the interpretation and the automatic analysis of the images. In order to reduce this noise and smooth the data, the properties of an anisotropic diffusion filter (ADF) are interesting. In this paper, we propose to adapt the setting of this filter parameters thanks the knowledge provided by an other process. This allows to smooth the speckle noise in the background, while the regions likely to contain any object of interest are preserved.","PeriodicalId":120840,"journal":{"name":"Europe Oceans 2005","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129581286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}