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Results
Estimation Method For Arrival Directions of Radio Waves to Measure the Surface Current of Sea Using VHF Radar On Vessel
Arai, Rei (Osaka Prefecture University) | Nakatani, Naoki (Osaka Prefecture University) | Sachi, Kentaro (Osaka Prefecture University) | Yamada, Tomoki (Osaka Prefecture University) | Okuno, Taketoshi (Osaka Prefecture University) | Hamano, Tetsuya (Kawasaki Shipbuilding Corporation)
Recently, VHF (Very High Frequency) radars have frequently been used for measuring the flow velocity field on the coast, as they enable the velocity distribution for exceedingly wide regions to be obtained simultaneously. This paper describes the results of an examination of the inference of a radar installed on board a steel vessel, where a VLCC (Very Large Crude-oil Carrier) was used for the experiments. Even if the characteristics of the received waves, called ¿antenna pattern¿ here, is deformed, it is possible to estimate the arrival direction of the radio waves in specific regions. The results imply the possibility of measuring the flow velocity distribution by means of VHF radars on board vessels. INTRODUCTION Knowing the surface current of the sea is important for the management of marine transportation, environmental issues, and ocean resources. The ocean current has been traditionally measured by specific velocity meters, such as floating buoys, magnetic current meters, and so on. Such methods are categorized under ¿point measurement¿, reflecting the fact that they are capable of measuring the current at specific points. Furthermore, the ADCP (Acoustic Doppler Current Profiler) has recently become a very popular instrument with regard to the ¿line measurement¿ method, or the so-called one-dimensional measurement method (Appel et al. 1991). It is a powerful non-contact tool using supersonic waves which provides the velocity profile along a specific line, particularly the velocity distribution in depth direction. In addition, PIV (Particle Image Velocimetry) has been developed for the purpose of the so-called ¿plane measurement¿, which is sometimes also referred to as two-dimensional measurement (Aida et al. 2002). PIV is very useful for obtaining the velocity distribution in extremely wide regions simultaneously. However, it is not effective at night or in bad weather, as its performance strongly depends on its ability to acquire a clear image of the sea surface.
- Transportation > Marine (0.88)
- Energy > Oil & Gas > Upstream (0.34)
Distribution Characteristics of Chemosynthetic Communities Around Seafloor Massive Sulfide Deposits
Yamazaki, Tetsuo (Osaka Prefecture University Sakai, Japan) | Ikemoto, Masahito (Osaka Prefecture University Sakai, Japan) | Nakatani, Naoki (Osaka Prefecture University Sakai, Japan) | Arai, Rei (Osaka Prefecture University Sakai, Japan)
The distribution characteristics of chemosynthetic communities around seafloor massive sulfide deposits provide important quantitative background information for the understanding of these sensitive ecosystems. Using visual seafloor observation data obtained by a towed camera system, a preliminary quantification approach of the distribution of chemosynthetic communities around seafloor massive sulfide deposits is presented. A manual visual definition and a semi-automatic color intensity analysis of the seafloor video images are the methods tested for quantifying the distribution. Some requirements for improving the approach are discussed. INTRODUCTION Kuroko-type seafloor massive sulfides (SMS) in the western Pacific have received much attention as resources for gold, silver, copper, zinc, and lead for the commercial mining by private companies (; ). Since the end of the 1980s, SMS have been found in the back-arc basin and on oceanic island-arc areas at 1 to 2 km of water depths. The typical representatives found are in the Okinawa Trough and on the Izu- Ogasawara Arc near Japan (Halbach et al, 1989; Iizasa et al. 1999), in the Lau Basin and the North Fiji Basin near Fiji (Fouquet et al., 1991; Bendel et al, 1993), and in the East Manus Basin near Papua New Guinea (Kia and Lasark, 1999). The high gold, silver, and copper contents in one of the areas have increased the likelihood that mining would be profitable, and a pioneer commercial mining venture is scheduled to start in a few years (). However, no quantitative data is available for the environmental assessment of the mining, though many scientific observations have been conducted by ROVs and manned submersibles. A preliminary quantification approach of the distribution characteristics of chemosynthetic communities around the SMS deposits are introduced in this study.
- Asia > Japan (0.89)
- Oceania > Fiji > South Pacific Ocean (0.88)
- Oceania > Papua New Guinea > Bismarck Sea > Manus Basin (0.99)
- Oceania > New Zealand > South Pacific Ocean > Lau Basin (0.89)
- Oceania > Fiji > South Pacific Ocean > North Fiji Basin (0.89)
- (2 more...)