OCEANS 2006 - Asia Pacific最新文献

{"title":"Wave-powered small-scale generation systems for ocean exploration","authors":"P. Brown, D. Hardisty, T. Molteno","doi":"10.1109/OCEANSAP.2006.4393878","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393878","url":null,"abstract":"This paper describes our initial investigation of an inertial power generation system, designed for use in small, low-power, long-endurance ocean exploration robots. The system recovers small amounts of power from the movements caused by ocean waves. The primary focus of the investigation to date has been the development of efficient power recovery system electronics that extract useful power from a wide range of ocean wave amplitudes and frequencies.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134239499","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":"Tsunami Detection using Multi-frequency Beam-Forming HF Radar","authors":"D. Trizna","doi":"10.1109/OCEANSAP.2006.4393896","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393896","url":null,"abstract":"We discuss a new multi-frequency beam-forming HF radar design for robust detection and tracking of tsunami waves from 200 km distances, providing continuous coverage of the tsunami approach to shore. The method works by mapping ocean currents at long range using traditional HF radar method of radial Bragg line Doppler shift measurement, then continuously looking for anomalous Doppler shift patterns and extremely high values due to the large orbital wave of the tsunami wave crest sequence. We discuss issues determining coverage quality improvement achievable using a multi frequency radar (MFR) in order to assure robust long range coverage. These issues include diurnal and seasonaly changes in noise character due to ionospheric conditions, and the effect of local wind speed and sea state providing a sufficiently good sea echo signal at long range. Multiple frequency utilization assures this higher quality at no design cost compared to existing single frequency HF radars, using the ISR digital radar design.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127577758","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":"Evaluation of River Regulatory Measures in Hughly Estuary using Tidal Asymmetry Characteristics","authors":"K. M. Sivakholundu, S. Kathiroli, J. Mani, V. G. Idichandy","doi":"10.1109/OCEANSAP.2006.4393870","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393870","url":null,"abstract":"Tidal asymmetry has a profound effect on estuarine hydrodynamics and sedimentation pattern. The information of tidal asymmetry can be a useful tool to evaluate the flow pattern in shallow estuary and characterize the dominance of flood or ebb flow. The effects of features (like obstructions, depressions, etc.) and discharge variation in a theoretical channel section is simulated to quantify the parameters of tidal asymmetry. A set of proposed river regulatory measures in a shallow estuary (Hughly, India) was taken up for evaluation using tidal asymmetry parameters to check whether this may be used as additional tool. The indications provided (flood dominance and hence sediment importing regime) with asymmetry parameters do match with field conditions (based on bathymetry survey data). The asymmetry parameters may be put to use to evaluate the change in flood/ebb dominance in relative terms in a given section.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130784592","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":"Bottom Boundary Layer Wave Measurements for Particle Studies","authors":"A. Williams","doi":"10.1109/OCEANSAP.2006.4393833","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393833","url":null,"abstract":"Suspended particles, which attenuate light and restrict visibility in moderate depths of the ocean, are commonly resuspended from the bottom by waves. This turbid layer initially consists of fine particles with settling rates of 0.01 mm/s that require weeks to settle out. However, the relaxation of the turbid conditions is often only a day or less implying particle settling rates of 1 mm/s, a rate requiring that the small particles aggregate into large particles that can settle more rapidly. Conditions that suspend and possibly disaggregate the fine sediment on the bottom and the aggregated particles in suspension are wave dominated in most continental shelf conditions. Thus formation of a turbid layer requires a shear stress exceeding a threshold. Relaxation of a turbid layer conversely requires a shear stress that remains always or nearly always below another threshold. This dependence of turbidity and the lifetime of turbid layers on shear stress focuses attention on what the shear stress is and what it depends upon. Shear stress at the bottom is a combination of Reynolds stresses from the mean current and the wave boundary layer. The thickness of the wave boundary layer is too small for direct Reynolds stress determinations in the boundary layer but the wave effects can be included into the model in other ways. Thus wave velocities in the wave boundary layer are very important in estimating the mean Reynolds stress. Even more important for the determination of the peak boundary layer stress felt by the bottom interface where the sediment may be eroded and the large particles disaggregated into smaller particles are the instantaneous velocities consisting of the sum of the mean current and the wave velocity. Determination of wave velocity should not be difficult for a rapidly sampling current meter near the bottom. The information required is present in the time series recorded by such an instrument. Yet the waves responsible for this sediment interaction at shelf depths are generally not revealed in conventional directional wave measurement instruments and wave spectra processing programs. Wave measuring instruments that are physically located on the surface or that sense the sea surface elevation acoustically or by wires are even more restricted by the dominance of short period, high amplitude waves when wind is present. Surface wave measurements rarely detect the low amplitude, very long period waves that are the dominant influence on the bottom in depths exceeding 10 meters because these waves are swamped by short period waves in all conditions except glassy calm. In order to adequately measure the waves that are significant for resuspension of benthic sediment, measurements of orbital wave velocity near the bottom in the depths of interest are preferred. While such near-bottom measurements present a problem for extrapolation back to the surface in generation of conventional directional wave spectra, the depth imposes a natural filter that","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132336779","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":"Coupling the stochastic matched filter and the à Trous algorithm for SAS image de-noising","authors":"F. Chaillan, P. Courmontagne","doi":"10.1109/OCEANSAP.2006.4393855","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393855","url":null,"abstract":"The wide research domain concerning SAS image de-noising shows the complexity of the problem. SAS devices designed to explore underwater world generate noise-corrupted data, strongly disturbed by the speckle noise, which affect both radiometric and spatial resolutions. Although many de-noising filtering techniques exist in the signal processing society and have shown their efficiency, they suffer of an important restrictive problem: the spatial resolution degradation. The matter is to design a processing having a strong de-noising power while preserving the spatial resolution. To perform this task, we present in this study a new way of SAS image de-noising consisting in coupling an efficient filtering technique, the stochastic matched filtering method, with a multi-resolution analysis technique, the a Trous algorithm. Comparison with some classical approaches on real SAS data reveal the efficiency of such an idea.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127798342","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":"Robust Tracking Control of Underwater Vehicles using Time-Delay Control in Discrete-Time Domain","authors":"R. Prasanth Kumar, A. Dasgupta, C. S. Kumar","doi":"10.1109/OCEANSAP.2006.4393967","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393967","url":null,"abstract":"This paper discusses the application of time-delay control law for robust trajectory tracking control of underwater vehicles. The idea is based on the cancellation of uncertain dynamics in the plant by estimating a function which closely approximates the plant uncertainty at any given instant. This is done through the feedback of the derivative of the state and the previous control inputs. By deriving the controller in discrete-time the necessity of using state derivative is removed. The controller is computationally simple and easy to implement. The effectiveness of the proposed controller is demonstrated through simulations for various test conditions.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117026331","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 Improvement of the Prescision of an Inertial Navigation System for AUV based on the Neural Network","authors":"S. Ishibashi","doi":"10.1109/OCEANSAP.2006.4393828","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393828","url":null,"abstract":"\"URASHIMA\" is an Autonomous Underwater Vehicle which was developed in Japan Agency for Marine-Earth Science and Technology in Japan. \"URASHIMA\" has the Inertial Navigation System in order to know its own current position, and it can cruise autonomously owing to the position data. However the position data includes some error which increases with the passage of time. In this paper, the method to improve the precision of the Inertial Navigation System based on the neural network is described. The network outputs the position data, which compensates the error of the position data calculated from it.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129697185","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":"Ambiguity Function and Cramer-Rao Lower Bounds for Passive Synthetic Aperture Sonar (SAS)","authors":"J. Passerieux","doi":"10.1109/OCEANSAP.2006.4393942","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393942","url":null,"abstract":"The resolving power of passive SAS is addressed by computing and plotting its ambiguity function in the frequency/bearing plane. It is proven that, even in ideal conditions, the apparently better spatial resolution of passive SAS is due only to the better frequency resolution which results from the longer processing time. In other respects the computation of Cramer-Rao Lower Bounds (CRLB) for joint source bearing and frequency estimation is detailed. It is shown that, in realistic situations, i.e. when the source frequency is not known, the bearing accuracy (standard deviation) does not depend upon the own speed (and hence on the length of the synthetic aperture). In fact the true, and maybe the sole, practical interest of the many proposed passive SAS algorithms [2, 4] is that they may appear as manners to perform a coherent very long time integration, thus possibly allowing detection of weak coherent narrow band sources.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130651831","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 Spread Spectrum Communication Based on M Family N group Parallel Transmission","authors":"Chengbing He, Jianguo Huang","doi":"10.1109/OCEANSAP.2006.4393940","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393940","url":null,"abstract":"Due to the low data rate of direct sequence spread spectrum (DSSS) underwater acoustic communication (UAC), a higher data rate spread spectrum UAC system based on M family phase modulation signal and N groups parallel transmission (MNSS) was designed. Lake tests were conducted and the results showed that it could reach 320 bps with BER below 10-4 at within the range of 25 km. In order to further improve the data rate of spread spectrum UAC, time overlapping method are introduced in this paper. Based on the saved channel (measured in lake tests), performance of time overlapping method and MNSS are compared. Simulation results show its robustness and relative higher data rate with little performance decrease. Meanwhile, a novel method for combining multipath messages using FFT/IFFT was also addressed to improve the performance of correlators in underwater environments. Computer simulates based on saved channel show its effectiveness with at least 2 dB processing gain.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130800038","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":"Navigation of an Autonomous Underwater Vehicle for Photo Mosaicing of Shallow Vent Areas","authors":"T. Maki, H. Kondo, T. Ura, T. Sakamaki","doi":"10.1109/OCEANSAP.2006.4393931","DOIUrl":"https://doi.org/10.1109/OCEANSAP.2006.4393931","url":null,"abstract":"Although underwater vent areas are scientifically important, precise photo mosaicing of them is for the following reasons still a hard task. Firstly, the visible range is limited by the turbid water and floating particles. Secondly, the conventional acoustic positioning is vulnerable to the bubble plumes of the vent areas. In this paper a navigation method of an autonomous underwater vehicle (AUV) for photo mosaicing of shallow vent areas where bubbles are spouting is proposed. Simultaneously, this method estimates the position of the AUV and the landmarks, such as bubble plumes and artificial sonar reflectors. The simultaneous localization and mapping (SLAM) based approach enables drift free, accurate, real-time and independent navigation in a local area, which is suitable for photo mosaicing. The proposed method has been implemented on the testbed AUV \"Tri-Dog 1\" and a tank experiment has been carried out to verify its performance.","PeriodicalId":268341,"journal":{"name":"OCEANS 2006 - Asia Pacific","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129249197","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}