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OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04

Date 9-12 Nov. 2004

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  • Implementation of multi-vessel tracking algorithm using multiple marine radar systems

    Publication Year: 2004 , Page(s): 2242 - 2248 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (717 KB) |  | HTML iconHTML  

    To prevent marine casualties, marine radars are widely used for tracking vessels near coast and, in general, multiple marine radars are applied to cover wide coastal area. Therefore their cooperative operation is very important for effective vessel traffic control. This work introduces implementation of a multivessel, multiradar tracking algorithm which can be used for such purpose. The implemented algorithm is based on the sensor-level tracking with centralized track file architecture which maintains a sensor-level (local) track file at each local radar site and integrate them into one central-level (global) track file using cross-correlation of the sensor-level tracks. The sensor-level tracking at each local radar site employs the conventional global nearest neighbor (GNN) approach which uses the auction algorithm for data association. The sensor-level tracks formed at each radar site are transmitted to data fusion center and combined by a track-to-track fusion algorithm to give central-level tracks. The resulting central-level tracks are also correlated against time to give a continuous track file for each target vessel even though it goes through the border of different radar's scan area. To validate the algorithm, a simulation was fulfilled and it showed that it operated properly as intended. View full abstract»

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  • Experimental study on stability of a caisson type quay wall by the artificial drain method using recycle material during earthquake

    Publication Year: 2004 , Page(s): 2092 - 2097 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    In order to improve earthquake-proof capacity of a caisson type quay wall, a series of shaking table model tests was performed using the new artificial drain system as a countermeasure against soil liquefaction. The tests were conducted under earthquake input motions, making the maximum acceleration level change. The results from these experiments indicate that the drainage provided by recycle artificial drains can significantly reduce pore pressure generation and deformation of the caisson type quay wall. The present study also shows that drain method is useful even under strong earthquake shaking to protect the horizontal movement of the caisson structure. View full abstract»

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  • Extreme events in ocean currents through depth in the vicinity of the Iceland-Scotland Ridge

    Publication Year: 2004 , Page(s): 2331 - 2337 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (846 KB) |  | HTML iconHTML  

    This study analyses the vertical structure of extreme currents for three sections in the vicinity of the Iceland-Scotland Ridge. The variation of speed and direction with depth of observational currents from the Variability of Exchanges in the Northern Seas (VEINS) project is studied. Currents have been divided into (1) the mean residual flow, (2) tidal current and (3) nontidal surge residuals to assess their relative importance in contributing to extremes. The results show considerable variation in the relative magnitude of the different components as function of both depth and location, which raises a number of fundamental questions concerning the structure of extreme currents and dominance of component effects. It is found that in these locations the amplitude and direction of extreme currents are dominated by the nontidal component in deep water, whereas tidal currents and surges are dominant near the surface and in shallow-water regions. In the section north of the Faroes the mean residual flow is equal to or larger than surge effects in near-surface measurements, where the direction of extreme currents is eastward for all the deployments; away from the sea-surface extremes have a southward-preferred direction. Here, the Faroe Current (FC) and the Iceland-Faroe Front (IFF) probably influence extremes. In the Faroe-Bank Channel current speed shows larger values in bottom measurements where the mean residual flow is dominant; in near-surface measurements the surge is dominant; extremes are found at bearings near 315°, particularly below 500 m. In the Faroe-Shetland Channel tide is generally larger than the surge and mean residual flow, particularly in the deployments on the Faroe side of the channel; the preferred direction is southward. View full abstract»

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  • A basic research on the long horizontal active time reversal communication

    Publication Year: 2004 , Page(s): 2219 - 2224 Vol.4
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB) |  | HTML iconHTML  

    We have researched on the application of time reversal waves to the underwater acoustic technology. Time reversal waves enable a desired signal to converge to the focus, even in unknown and inhomogeneous media. As time reversal waves converge to a "point" at any range, their focusing property is quite different from that of the conventional beam forming method. In this work, the results of the basic research on active time reversal communication are described. The "active" implies that time reversal waves are transmitted in practice in the ocean, and implies the communication from an array to a point. By using time reversal, the reflected and refracted waves are converged to the focus, the signal level received at the focus increased and the symbol interferences are reduced. However, in order to ensure the communication channel only with time reversal, it is necessary to install many transducers of time reversal array. So, in this study, it is proposed to combine the focusing effect of time reversal waves and conventional adaptive filter. After most of the multipath waves are utilized by using time reversal with a sparse array, unfocused waves, which appear like "noise", are removed by adaptive filter. The simulations in shallow water are performed with various ranges. It is concluded that this proposed method makes high speed communication to the long distance possible. View full abstract»

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  • Study on corrosion degradation of wire ropes in sea water

    Publication Year: 2004 , Page(s): 1910 - 1917 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB) |  | HTML iconHTML  

    Wire ropes used in marine environment have a great degradation due to corrosion. Accurate inspection methods for corrosion of wire ropes are necessary to ensure their safety. However, technical background data of corrosion is quite few at present, and is not sufficient for wire rope inspection. Collecting the technical data is important to establish and ensure the offshore structure's maintenance technology including wire rope inspection. A laboratory test of wire ropes degradation was carried out with seawater tanks for 5 years since 1994 to 1999. 14 kinds of ropes were used for the experiment. Further, an exposure test in real sea area was also carried out for 11 months in 1997 to acquire degradation data in dry zone above sea level, in ebb zone, and in the seawater zone. Eight kinds of ropes and 3 kinds of wires were used for the exposure test. During the test period, we examined the ropes for several times on the following characteristics. (1) appearance of ropes and strands, (2) cross section of each wire layers, (3) properties of wire: diameter, tensile strength, number of torsion, (4) mass of coating. The changes of characteristic values were approximated in the curve to eliminate fluctuation errors. We calculated the most suitable characteristics values when the experiment was finished and converted into normalized values divided by initial values. Corrosion degradation of some kinds of wire ropes was evaluated with normalized characteristics values, and appearance of their surface and their cross section. View full abstract»

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  • Basic requirements and options for communication systems in scientific underwater cable networks

    Publication Year: 2004 , Page(s): 2211 - 2218 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB) |  | HTML iconHTML  

    New innovative scientific underwater cable networks have been proposed and initiated in many locations around the world. These networks have become feasible due to recent evolution of underwater telecommunication cable technology. However, their communication systems are quite different from standard telecommunication cable systems. Differences between the characteristics of existing submarine telecommunication systems and the basic technical requirements of scientific underwater cable networks will first be described. Options for the use of existing technologies include optical gigabit Ethernet (GbE) over a separate DWDM optical transport, integrated CWDM GbE transceivers and DWDM with Raman modulators. These will be presented along with their advantages and disadvantages. The present status of NEPTUNE communication system and considerations on its reliability will also be presented. View full abstract»

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  • Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

    Publication Year: 2004
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    Freely Available from IEEE
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    Publication Year: 2004 , Page(s): 0_2
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    Publication Year: 2004 , Page(s): 0_3
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  • OCEANS '04 - MTS/IEEE TECHNO-OCEAN 04 - Title Page

    Publication Year: 2004 , Page(s): i
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    Freely Available from IEEE
  • Copyright

    Publication Year: 2004 , Page(s): ii
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  • Author's index

    Publication Year: 2004 , Page(s): vii - xxiii
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    Publication Year: 2004 , Page(s): xxiv
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  • Table of contents

    Publication Year: 2004 , Page(s): xxv - lviii
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  • Wave effect on microwave scattering at water surface

    Publication Year: 2004 , Page(s): 1803 - 1806 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB) |  | HTML iconHTML  

    Microwave scattering at the water surface where a water surface wave coexisted with wind-waves was measured in an experimental water tank. Scattering characteristics, scattering coefficients and Doppler spectra of backscattering microwaves and the relation between scattering characteristics and physical properties of a water surface wave such as wave length, wave height, wave phase and orbital velocity have been investigated. The tilt modulation by water surface slope and the change of wind velocity near water surface by the fluctuation of water surface level were confirmed as influence of water surface wave in microwave backscattering strength. However, the hydrodynamic modulation could not be confirmed. The influence of a water surface wave in microwave backscattering had a strong showing at the Doppler spectrum of backscattering microwave. At first, the middle frequency of the Doppler spectrum of backscattering microwave from the water surface where a water surface wave coexisted with wind-waves was corresponding to that of the wind-wave water surface generated only by wind in the same incident angle and azimuth. The band width of the Doppler spectrum was the value that added 2 times of orbital velocity of water surface wave to that of the wind-wave water surface. The influence of azimuth to the band width was not shown View full abstract»

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  • A long baseline kinematic GPS solution of ionosphere-free combination constrained by widelane combination

    Publication Year: 2004 , Page(s): 1807 - 1814 Vol.4
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    Why can't the dual frequency long baseline kinematic positioning be solved accurately? In kinematic positioning, the coordinates changes epoch by epoch, and the number of the observation equations per unknown does not increase. Hence, the averaging effect of the least square solution can't work well in contrast to the static positioning. So, when the baseline length is long and the error increases, the least square solution can't give the accurate solution. Supplementary information for the correct solution would be required. In case of static positioning, a constraint that the coordinates of the receivers are constant is imposed. If a similar constraint is found in kinematic positioning it may be a strong help to obtain the accurate solution. The initial phase ambiguities of the wide-lane combinations can be obtained correctly irrespective of the baseline length by using HMW (Hatch-Melbourne-Wubbena) combinations. The ionospheric delays may be estimated with rather nice accuracy by using the external source such as IONEX and the geometry free combinations. So, the use of the information may be useful. Specifically, a nice approximation of the coordinates is obtained by solving the wide-lane combinations where the above-mentioned wide-lane ambiguities and the ionospheric delays are used. The ionosphere free combinations are solved under the constraint of these coordinates View full abstract»

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  • An integrated approach of remote sensing and geophysics for investigating geological structure in the East Vietnam Sea

    Publication Year: 2004 , Page(s): 1815 - 1820 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (606 KB) |  | HTML iconHTML  

    The East Vietnam Sea (South China Sea) is a large area with the diversely complicated conditions of geological structure. In spite of over the past many years of investigation, many marine places have remained poorly understood because of a thick seawater layer as well as of the sensitive conflicts among the countries in the region. Fortunately, satellite altimeter technology is allowing the enhancement of marine investigation in any area. The spatial variation of the ocean surface topography can be measured by a very accurate radar altimeter mounted on a satellite. The ocean surface is an equipotential surface of the Earth's gravity field. Therefore it can be converted into marine satellite-derived gravity by using the mathematical model. The detailed satellite-derived gravity anomaly and its variants are essential for understanding geological structure and marine geophysics. They provide a reliable opportunity to geologists and geophysicists for studying the geological features beneath the oceanfloor. Also satellite altimeter data is perfect for planning the more detailed shipboard surveys. The satellite altimeter data is collected by the Geosat, ERS-frac12 altimeters. In this paper, the authors emphasize the application of satellite-derived data for investigating of geological structure in the East Vietnam Sea. The satellite data is compared and combined with the shipboard data and has resulted in a significant improvement on its accuracy and resolution. It is constrained by shipboard data using the finite difference, minimum curvature methods. The satellite-derived gravity along with the geophysical advanced methods such as finite difference, gravity gradient, gravity derivative, residual isostatic gravity etc, have brought out an unambiguous picture on the geological structure in the area. Many geological features, such as seafloor spreading ridges, fault systems, volcanic chains, seamounts and shear zones are revealed on the satellite-derived gravity maps as - well as on its variants. Especially, it is more meaningful in the remote or sparsely surveyed areas. The achieved results are checked and confirmed by the shipboard and seismic data View full abstract»

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  • Airborne polarimetric SAR monitoring for ships and coastal seas

    Publication Year: 2004 , Page(s): 1821 - 1824 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    Airborne polarimetric and interferometric synthetic aperture radar (PiSAR) images are analyzed for monitoring ships and coastal seas especially for estimating sea surface wind speed and direction. Though in situ ships data through AIS (Automatic Identification System) were not available by the time of analysis, PiSAR's X band images showed the potential to map coastal wind vectors with high spatial resolution of 2.5 m View full abstract»

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  • Offshore wind profile observation system on a floating buoy

    Publication Year: 2004 , Page(s): 1825 - 1829 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (417 KB) |  | HTML iconHTML  

    To detect the availability of wind farms, it is important to evaluate their profitability based on actual wind data. In case of an offshore wind farm, especially in deeper waters, we can not find any actual measured data to evaluate it. In Europe, the data are gained with a conventional meteorology tower mounted on the seabed in shallow water. However some offshore wind farms which may be expected in the Japanese coastal area will be located in the deeper waters. So, a floating type is one of the solutions in deeper waters to achieve cost-effectiveness and reliability. The new offshore wind profile observation system can provide wind profile of approx. 20 m to 200 m above sea surface in deeper waters. In this paper, outline of this study result is introduced View full abstract»

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  • Survey report of offshore wind conditions in prospect of offshore wind energy conversion systems in Japan

    Publication Year: 2004 , Page(s): 1830 - 1834 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    Wind energy is viewed as a promising new energy resource in its pure, clean, and inexhaustible nature. Because of less disturbed, stable and strong wind conditions, coastal areas are considered to be suitable for constructing wind energy systems. Moreover, it is said that offshore wind conditions are better than inshore wind conditions for power generation. However, actual measured reports of offshore wind are very few. This report describes the applicability of laser radar system to offshore wind measurement View full abstract»

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  • Field test and numerical simulation on the coastal wind-powered light system

    Publication Year: 2004 , Page(s): 1835 - 1840 Vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB) |  | HTML iconHTML  

    This paper introduces field test and numerical simulation on coastal wind-powered light and battery system, as one typical example of on-site wind power utilization. Field experiment was conducted at the Kurihama coast facing to the entrance of the Tokyo Bay. The experimental system with 12W powered light was set to operate daily 6 hours after sunset. Wind velocity and direction at the three points, light on-off signal, electric power generation rate, and battery voltage corresponding to the stored electric power were recorded continuously for eight months without interrupt. Three dimensional wind characteristics were numerically simulated to estimate topographical wind distribution. Based on the observation and numerical simulation, optimal design of coastal wind-powered lights and battery system was shown with consideration of topographical and time variation of wind characteristics View full abstract»

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  • Construction of the first offshore wind turbines in Setana Port in Japan

    Publication Year: 2004 , Page(s): 1841 - 1846 Vol.4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (638 KB) |  | HTML iconHTML  

    Two 600 kW wind turbines were built in the Setana Port area in summer 2003, and started official electric generation from April 1st, 2004. They are the very first wind turbines built in the offshore area in Japan. In Hokkaido, there are many wind energy development projects on land, and of course there are many wind turbines operating in Tohoku area, northern part of Honshu Island, too. While offshore wind farms, consisting of ten to twenty wind turbines at a single offshore location, are being built and operated from 1980s and 90s in Europe, no such offshore project is realized in Japan before. But cooperating with the Setana Town government, RIOE (Research Institute for Ocean Economics) had examined the feasibility of the offshore site selection of wind turbines, thanks to the large unused sea area of the port and to the financial support from NEDO (New Energy Development Corporation). Potential of the wind energy on site is quite favorable with 7.9 m/s average through a year, and good efficiency is expected. RIOE organized research committee on this project for a couple of years and executed the basic design phases. Joint Venture Construction company consisted of Kawasaki Heavy Industries and Penta-Ocean companies were engaged in construction and had unique experience. Problems faced with are not only in the technical but also in the economic field with regard to selling the produced electricity to the Hokkaido Electric Company. Those experiences are described and discussed the possibility of the offshore wind farms in Japan in this paper View full abstract»

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  • LPV technique for rotational speed control of wind turbines using measured wind speed

    Publication Year: 2004 , Page(s): 1847 - 1853 Vol.4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    In the paper, we apply LPV (linear parameter varying) control methodology for the rotational speed control problems of wind turbines. Our goals are extracting maximum power in the region below the rated wind speed and maintaining the rated power in the region over the rated wind speed. Effectiveness of the LPV control is shown by means of numerical simulations, compared with results by conventional controls View full abstract»

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  • AquaBuOY - the offshore wave energy converter numerical modeling and optimization

    Publication Year: 2004 , Page(s): 1854 - 1859 Vol.4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (547 KB) |  | HTML iconHTML  

    Ocean energy and offshore wave energy conversion in the United States is at a significant milestone. During the next couple of years, ocean energy technology developers and energy officials have a potential to deploy pilot scale ocean energy conversion installations. This capability comes at a time of increased interest in ocean energy worldwide. The paper outlines AquaEnergy's experience in developing the Makah Bay pilot offshore power plant and results of the projected performance data developed using E2I EPRI guidelines. The Makah Bay, WA offshore pilot power plant uses AquaEnergy's point absorber wave energy conversion device - AquaBuOY. The device is the next generation of the technology that combines the Swedish Hose-Pump and the IPS Buoy technologies to generate clean energy from ocean waves. Currently the project is undergoing environmental permitting in support of FERC & NOAA licenses. In early 2004 AquaEnergy, US, and RAMBOLL, DK, performed output projections to substantiate the expected performance of the Makah Bay pilot plant in support of the E2I EPRI Offshore Wave Energy Feasibility Demonstration Project. AquaEnergy will conclude its presentation with a brief overview of current legislation affecting the industry. In 2004, ocean scientists, engineers, and developers can continue to lay the groundwork for government spending and interest in ocean energies View full abstract»

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