V-5 A study on the matching between the air turbine and phase control for the OWC wave power generator     

Hitoshi Hotta 《Ocean Engineering》1985,12(6):585-586

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Photographic observations of deep-sea infaunal ophiuroids in Suruga Bay,central Japan: an application of a free-fall system of time-lapse cameras and current meters     

Toshihiko Fujita  Suguru Ohta 《Journal of Oceanography》1990,46(5):230-236

Underwater observations of infaunal amphiurid ophiuroids were made at a depth of about 480 m in Suruga Bay, central Japan, using a free-fall system which consists of time-lapse stereo-photography units and current meters. The megabenthos fauna was characterized by the dominance of infaunal echinoderms; in particular, amphiurid ophiuroids were numerically dominant. The density and biomass of the amphiurids were 170 m^–2 and 37 g m^–2, respectively. They buried their discs in the sediment and extended their arm tips out of the sediment surface. They protruded 2.2 arms per individual on the average. Strong bottom currents were observed, and the average velocity was 12 cm sec^–1 at 4 m above the sea floor. No arm tip was observed to be raised vertically into the water column for suspension feeding utilizing the bottom current, and amphiurids were considered to be primarily a surface deposit feeder at the present site.  相似文献   

Modification of the damping function in the k–ε model to analyse oscillatory boundary layers     

Ahmad Sana  Abdul Razzaq Ghumman  Hitoshi Tanaka   《Ocean Engineering》2007,34(2):320-326

A simple relationship has been developed between the wall coordinate y⁺ and Kolmogorov's length scale using direct numerical simulation (DNS) data for a steady boundary layer. This relationship is then utilized to modify two popular versions of low Reynolds number k–ε model. The modified models are used to analyse a transitional oscillatory boundary layer. A detailed comparison has been made by virtue of velocity profile, turbulent kinetic energy, Reynolds stress and wall shear stress with the available DNS data. It is observed that the low Reynolds number models used in the present study can predict the boundary layer properties in an excellent manner.  相似文献   

Renewable energy from the ocean   总被引：3，自引：0，他引：3  

Robin Pelc  Rod M. Fujita   《Marine Policy》2002,26(6)

Growing concern over the threat of global climate change has led to an increased interest in research and development of renewable energy technologies. The ocean provides a vast source of potential energy resources, and as renewable energy technology develops, investment in ocean energy is likely to grow. Research in ocean thermal energy conversion, wave energy, tidal energy, and offshore wind energy has led to promising technologies and in some cases, commercial deployment. These sources have the potential to help alleviate the global climate change threat, but the ocean environment should be protected while these technologies are developed. Renewable energy sources from the ocean may be exploited without harming the marine environment if projects are sited and scaled appropriately and environmental guidelines are followed.  相似文献   

Distribution of phototrophic bacteria in Omura Bay during the summer with special reference to brownChlorobium     

Yuji Fujita  Buhei Zenitani 《Journal of Oceanography》1975,31(3):124-130

The distribution of phototrophic bacteria was investigated during the summers of 1969 and 1970 in Omura Bay of western Kyushu. Phototrophic sulfur- and nonsulfur-bacteria were distributed numerously in the mud and bottom water. Brown strains usually dominated in number. In water column, other than bottom water, there were usually few or no phototrophic bacteria. On occasion, however, a large number of brown bacteria were found in the middle of water column. Six strains, two each of the purple, green and brown bacterial colonies, were isolated from mud and sea water. The purple and green bacterial strains were identified as belonging to the generaChromatium andChlorobium, respectively. The brown strains could not be identified using Bergey's manual, but were found to be similar to the brownChlorobium described byPfennig. All six strains required sulfide for growth. Heterotrophic tendency was greater for the purple and green strains than for the brown strains. Their growth was enhanced by the addition of thymine. Living cells, taken from enrichment cultures of mud samples from four stations, gave absorption spectra almost identical to the spectrum of brownChlorobium. Thus it appears that during the summer brownChlorobium is the dominant phototrophic bacterial group in Omura Bay.  相似文献   

Decomposition of Phytoplankton in Seawater. Part I: Kinetic Analysis of the Effect of Organic Matter Concentration     

Minoru Fujii  Shinichiro Murashige  Yuka Ohnishi  Atushi Yuzawa  Hitoshi Miyasaka  Yoshimi Suzuki  Hiroshi Komiyama 《Journal of Oceanography》2002,58(3):438-443

Decomposition experiments were conducted on cultured phytoplankton (Skeletonema costatum) in seawater containing decomposer and consumer of size less than 500 μm. We determined the decomposition rates of bulk particulate organic matter (POM), the ratio of labile to semi-refractory fractions in the POM, and the POM carbon/ nitrogen (C/N) ratio during decomposition. To identify the kinetic mechanisms involved in the reactions of different order (e.g., first- and second-order), we studied the sensitivity of reaction rates to the initial concentration of POM, ranging from 2.4 to 71 mg-C L⁻¹. The results showed that decomposition consists of two first-order reactions: decomposition of labile and of semi-refractory particulate organic carbon (POC). The decomposition rate constants found for labile (0.13 day⁻¹ at 20°C), and semi-refractory POC (0.008 day⁻¹ at 20°C), and the carbon weight ratio of semi-refractory POC (13% at 20°C), were insensitive to the initial organic matter concentration. The time-dependence of the C/N ratio was also independent of this initial concentration. The decomposition rate constants and the content of semi-refractory POC did not change, regardless of the absence or presence of 25–500 μm organisms in natural seawater. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Importance of feeding on regenerable parts of prey for juvenile stone flounder Platichthys bicoloratus in estuarine habitats   总被引：3，自引：0，他引：3  

Takeshi Tomiyama  Satoshi Katayama  Michio Omori  Hitoshi Honda 《Journal of Sea Research》2005,53(4):297-308

Prey availability is one of the most important factors affecting the quality of nursery grounds. Estuaries play an important role as nursery grounds for juvenile stone flounder, but the mechanism behind the consistently high availability of prey has never been examined. This study investigates which prey is mainly selected by juvenile stone flounder (15–55 mm standard length) in the estuary of the Natori River, northern Japan. In a cage experiment, juveniles showed positive selection for the palps of the spionid polychaete Pseudopolydora kempi in March, and for the siphons of the bivalve Nuttallia olivacea in April, May and June in both sandy and muddy-sand habitats. This selective predation showed that sublethal predation on regenerable parts of invertebrates is important for stone flounder. Nuttallia olivacea, the dominant bivalve in the estuary, was more abundant and in better somatic condition in the sandy area in spite of the stronger siphon-cropping pressure by juvenile stone flounder. These results confirm that sublethal predation on highly abundant benthos plays an important role in forming estuarine habitats into areas of high prey availability for juvenile stone flounder, which leads to their high growth rate.  相似文献   

Mesoscale eddy effects on temporal variability of surface chlorophyll a in the Kuroshio Extension     

Shinya Kouketsu  Hitoshi Kaneko  Takeshi Okunishi  Kosei Sasaoka  Sachihiko Itoh  Ryuichiro Inoue  Hiromichi Ueno 《Journal of Oceanography》2016,72(3):439-451

We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow.  相似文献   

Fine-scale structure and mixing across the front between the Tsugaru Warm and Oyashio Currents in summer along the Sanriku Coast,east of Japan     

Sachihiko Itoh  Hitoshi Kaneko  Miho Ishizu  Daigo Yanagimoto  Takeshi Okunishi  Hajime Nishigaki  Kiyoshi Tanaka 《Journal of Oceanography》2016,72(1):23-37

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Influence of evaporation from the forest floor on evapotranspiration from the dry canopy     

Kenichi Daikoku  Shigeaki Hattori  Aiko Deguchi  Yu Aoki  Mari Miyashita  Kazuho Matsumoto  Junichi Akiyama  Shinichi Iida  Tae Toba  Yuji Fujita  Takeshi Ohta 《水文研究》2008,22(20):4083-4096

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