OCEANS 2007最新文献

{"title":"Acoustic Inversion of the Cold Water Filaments Off the Southwest Coast of Portugal","authors":"P. Felisberto, S. Jesus, P. Relvas","doi":"10.1109/OCEANS.2007.4449336","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449336","url":null,"abstract":"Cold water filaments have important implications in the biological and chemical exchanges between the coastal and offshore ocean. The Cape Sao Vicente area in the Southwest coast of Portugal is a well know region where such phenomenon is observed. In October 2004, the multidisciplinary project ATOMS, involving oceanographers and acousticians, was conducted with the objective to complement the sea surface temperature (SST) satellite observation with a full water column characterization. Due to weather and technical conditions during the project sea trial, only CTD measurements in upper layers of the water column were performed. These at sea collected data together with archival data from the NODC database, allowed to establish a realistic scenario of the 3D temperature distribution in the area, including deeper water layers. Archival data of temperature profiles suggest the occurrence of other important oceanic phenomena such as the subduction of warm Mediterrenean water, that should also influence the acoustic propagation. With the help of forward acoustic modelling the significance and signature of the individual oceanographic phenomena on the acoustic propagation, regarding different sampling strategies of the area by acoustic means is investigated. These investigations allowed to develop strategies to settle the main problem addressed by this work: invert the cold water filament structure by acoustic means in a complex environment where acoustic propagation is affected also by other important oceanic and bathymetric features. Since, the objective of this work, is to evaluate the ability to perform a 3D characterization of vertical structure of the ocean, a minimal transmit-receive acquisition composed of a suspended source from a ship and a drifting vertical array, is assumed. The spatial structure is obtained by a combination of inversions for \"mean\" sound speed/temperature perturbations obtained for source-array cross-sections covering the area of interest. Matched-field and ray tracing based tomography techniques are used in the inversion for the \"mean\" perturbations. The planned sampling strategies and necessary acoustic equipment to resolve such oceanic features is discussed having in mind future sea trials.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122061363","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":"Underwater Acoustic Communications Performance Modeling in Support of Ad Hoc Network Design","authors":"W. Fox, P. Arabshahi, Sumit Roy, Nathan Parrish","doi":"10.1109/OCEANS.2007.4449156","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449156","url":null,"abstract":"This paper discusses a methodology for predicting underwater acoustic communications performance using high fidelity acoustic time series simulation and acoustic modem processing emulation. Multiple source/receiver combinations can be simultaneously simulated, so that aspects of a complete underwater network can be studied. Here, the fundamental modeling and emulation capability will be described, with examples of the propagation modeling, time series simulation, and modem processing over multiple realizations of example communications channels. The results show the dependence of source and receiver location in the water column with respect to the sound speed profile on communications performance. The utility of such simulations for ad hoc network design in the presence of moving communications nodes will be discussed.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128305162","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":"Beam pattern estimation of clicks of a free-ranging Ganges river dolphin","authors":"R. Bahl, H. Sugimatsu, J. Kojima, T. Ura, S. Behera, T. Inoue, T. Fukuchi","doi":"10.1109/OCEANS.2007.4449286","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449286","url":null,"abstract":"The first recordings of bio-sonar clicks of free-ranging Ganges river dolphin (Platanista gangetica) were made in Budhabalanga river in Orissa, India. The system used for recording is a 3.2 meter long array composed of three hydrophones forming an equispaced linear SBL array and another two hydrophones in conjunction with the central hydrophone forming a small SSBL triangular array in a plane perpendicular to the array axis. The array structure was deployed both in horizontal and vertical configurations. The clicks of the dolphin received on each hydrophone were sampled at a rate of 500 kHz per channel. From the sampled clicks data, the sonar transmit beam pattern of the dolphin in both horizontal and vertical plane was estimated using difference of ASL (apparent source level of the click signal) and the absolute angles of the dolphin's location between the central hydrophone and the other two peripheral hydrophones for the on-axis clicks. To estimate more accurate beam pattern, conditions for selection of on-axis clicks were well-considered, and thus we propose a new criteria for determining on-axis clicks. In this method, we assume that the dolphin's beam pointing direction is towards the central hydrophone and it's beam pattern is symmetrical. However, actual measurement of ASL from three hydrophones shows that values at the peripheral hydrophones are not always same. This suggests that the dolphin's beam is not pointing exactly towards the central hydrophone so that the central hydrophone's ASL is not the real peak value of the beam. We propose a refinement in the beam pattern estimation method using interpolation and curve fitting to obtain an improved estimate of the Ganges river dolphin's beam pattern. By analyzing all available clicks, we have estimated the dolphin's beam pattern in both horizontal and vertical plane. The 3-dB beamwidth is found to be approximately 10 degrees in horizontal plane and 14 degrees in vertical plane. In this paper, we propose the new beam pattern estimation method using interpolation and curve fitting.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128493098","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":"Traction properties of the wheels of an underwater crawler on different soils","authors":"C. Waldmann, L. Richter","doi":"10.1109/OCEANS.2007.4449354","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449354","url":null,"abstract":"Crawlers are specialized vehicles that allow for underwater intervention by staying in direct contact with the seafloor. These are completely different operating conditions as compared to free flying underwater vehicles. In particular one can expect from this vehicle concept that it offers a very stable platform for conducting delicate measurements at the interface of seafloor and the water column. Additionally, crawlers lend themselves to long term observations with passive phases where the system can go into sleep mode. In space sciences crawlers are already well established platforms (\"planetary rovers\") and have successfully proven their capabilities in several missions to the Moon and to Mars. For ocean sciences there are still a number of technical problems that have to be solved before a widespread use of these types of platforms can be expected. The attractive properties of crawler systems led to several attempts in the development of wheeled or tracked vehicles. However, it is still an open discussion which type is better suited for underwater applications. The reason why in the case reported here a decision has been made in favor of a wheel driven system mainly goes back to the fact that wheeled system can be designed to be more energy efficient. This is of particular importance for this crawler system as it is supposed to operate autonomously in deep waters, with a fixed energy supply per deployment. As the sediment properties in most parts of the world oceans are unknown a model has to be developed of how to predict the performance of crawler systems under different conditions and adjust the weight in water accordingly or select the right type of wheels. This implies a good knowledge of the traction properties of the individual wheel design. As part of the bi-national funded project MOVE! (Moving Lander) we conducted a number of laboratory tests which were used to firm up the wheel design and predict the performance. But during the last field tests some unforeseen problems with the traction of the wheels showed up. It appeared that the traction has been less than expected in the environment encountered and the wheel had a tendency for digging in although from the sinkage of the wheel and visual observations this should not have been the case. Therefore a set of field tests on different soils in a shallow water environment have been designed and carried out. The objective was to gain more insight into the interaction of an individual wheel with different soil types to be able to come up with an improved model based on a more reliable data set. To have better control on the conditions where the experiment has been carried out a single wheel test set-up has been designed and realised. In particular it is important to control the attitude and the load on the wheel under test. By combining the measurement of the sinkage of the wheel, the pull force, the rotation rate and the translational speed with the electrical parameters of the motors ","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"168 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128604260","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":"The Inventory of the Marine Habitats on the Romanian Littoral with Significance in Marine Conservation and Exploitation","authors":"T. Zaharia, R. Sîrbu, S. Nicolaev, D. Micu","doi":"10.1109/OCEANS.2007.4449134","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449134","url":null,"abstract":"The paper presents the results of the inventory of the habitats on the Black Sea Romanian littoral with an European significance, achieved by a team from NIMRD Constanta. The proceedings were carried out during the year 2006, in the context of Romania's integration in the European Union.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124700812","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":"Large Scale Ocean Based Ice Structures for Habitats, Storm and Flood Protection, and Industrial, Energy, and Transport Applications","authors":"J. Powell, J. Powell","doi":"10.1109/OCEANS.2007.4449118","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449118","url":null,"abstract":"A new approach, for large ocean structures, termed LISA (large ice structure assemblies) is proposed. Thermally insulated LISA ice structures can be used for a wide variety of applications, and can be constructed and maintained for many years at low cost. Three types of LISA structures are described: LISA-1 floating platforms for off-shore airports, habitats, industrial and power plants, drilling rigs, etc.; LISA-2 fixed structures in shallow waters for levees and dikes to protect coasts against storms and rising ocean levels; and LISA-3 submersibles for the long distance transport of large amounts of fresh water and other materials. LISA structures can be very large, multi- kilometers in lateral dimensions. Using conventional materials for thermal insulation, thermal leakage into LISA's-30degC ice interior is on the order of 1 watt(th)/per m2 of surface area, with annual refrigeration costs of less than $1 per m2. LISA structures can be constructed at their operating site, or at a different location and towed to their site. Methods of construction are described. Construction at high latitudes using low ambient temperatures for refrigeration is possible, and enables very low construction cost.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129490232","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":"Submerged Jet Currents in the Gulf of Mexico","authors":"S. Fan, G. Jeans, C. Yetsko, L. Oey","doi":"10.1109/OCEANS.2007.4449299","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449299","url":null,"abstract":"A recent screening study of MMS NTL ADCP 2005 and 2006 data has identified two modes of submerged jet currents in the Gulf of Mexico: (1) submerged speed peaks with inertial period and (2) events isolated in time with no clear periodicity. The latter can be divided further as shallow jet events (between 150 m to 600 m) and deep jet events (deeper than 600 m). The submerged jet events can last a few hours to several days. In order to investigate the jet generation mechanisms and test the predictability of the events, representative events for each mode were studied. Satellite sea surface height (SSH), sea surface temperature (SST) data and forecast data of the Princeton Regional Ocean Forecast System (PROFS) during the selected events have been used. Mode 1 jets are mainly due to downward propagating of inertial oscillations following hurricanes, while the deep jets of mode 2 appear to be caused by deep current propagation along the 1000 m isobath. The shallow jets of mode 2 are the result of on-slope flow convergence producing a subsurface downwelling/upwelling cell and frontogenesis over the slope. The comparison of PROFS model and observations shows good predictive skill although the model has the tendency to underestimate current strengths.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130369378","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":"An Adaptive Algorithm for Amplitude and Phase Measurements Based on Multiple Sampling","authors":"X. Xiong, A. Zielinski","doi":"10.1109/OCEANS.2007.4449159","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449159","url":null,"abstract":"Precise amplitude and phase measurement of a narrowband signal is required in many practical applications related to underwater sensing, navigation, and positioning. Existing methods or algorithms of phase and amplitude measurement such as in-phase and in-quadrature detection or quadrature sampling are useful, but lack capabilities to adapt to changing conditions. To overcome this limitation, we propose an adaptive algorithm based on multiple sampling that allows modification of certain parameters in response to changing conditions.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129283992","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":"A Novel Framework to Simulate Maritime Wireless Communication Networks","authors":"S. Wen, P. Kong, J. Shankar, Haiguang Wang, Y. Ge, C. Ang","doi":"10.1109/OCEANS.2007.4449340","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449340","url":null,"abstract":"We developed a framework for simulating wireless communications in the ocean environment, The framework incorporates three unique maritime features: the wave motion and its effect on wireless transmissions, the ocean surface path loss characteristics, and the mobility pattern of the ships conducting wireless transmissions. We implemented our design in the Qual-Net network simulator. Using the enhanced simulator, we were able to produce simulation results comparable to experimental measurements carried out under similar settings. In addition, we observed the expected communication quality changes as the sea condition worsens in the network simulator.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"495 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123197198","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":"Integrating passive and active acoustics for the assessment of fish stocks","authors":"G. Thomas, T. Hahn, R. E. Thorne","doi":"10.1109/OCEANS.2007.4449243","DOIUrl":"https://doi.org/10.1109/OCEANS.2007.4449243","url":null,"abstract":"The single most important information for the conservation of exploited marine fish stocks are precise measurements of their biomass so that harvest rates can be established that do not deplete the stock. However, the measurement of marine fish stocks is difficult due to the size, structure, and composition of the ocean, and the highly dynamic movements of the fish. Furthermore, traditional, discrete net sampling approaches have lacked sampling power to assess single fish stocks in time and space [2]. Without the ability to independently measure fish stock biomass with precision, managers have instead relied upon the commercial catch and deterministic indices as a primary source of empirical data. Also, without precise empirical data on stock biomass, the models used to make predictions are unverifiable and highly uncertain. Despite the severe management risks, this is the status quo, and it greatly confounds our efforts to sustain our fisheries, conserve exploited fish stocks and understand the dynamics of population response to natural and anthropogenic changes in the environment. High frequency active acoustics has been used to assess fish stocks for over four decades. When first introduced in the 1970s, there were hopes that acoustics would overcome the marine fish stock measurement problem because of a 105 increase in sampling power. However, prior to the introduction of acoustics the management agencies had already chosen large ocean areas to survey fish stocks, specifically in the summer months when the weather was good. In doing so, the agencies had assumed that surveys in large ocean areas would allow a representative assessment of single stocks of fish.","PeriodicalId":214543,"journal":{"name":"OCEANS 2007","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121687820","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}