Distribution of sardine eggs and larvae related to the surface circulation in Sagami Bay     

Hideaki Nakata  Keiichi Hasunuma  Toshiyuki Hirano 《Journal of Oceanography》1989,45(1):11-23

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Bedforms produced by the Kuroshio Current passing over the northern Izu Ridge     

Yu'suke?KuboEmail author  Wonn?Soh  Hideaki?Machiyama  Hidekazu?Tokuyama 《Geo-Marine Letters》2004,24(1):1-7

Current-generated bedforms were found on sandy seafloor at water depths of 200–400 m on the northern Izu Ridge, where the Kuroshio Current encounters and passes over the ridge. The observed bedforms include large dunes and sand ribbons and are interpreted to be products of present-day oceanographic conditions and to indicate intensive flow activity controlled by local topography. A comparison between the surface flow velocity estimated from empirical relationships for dune formation and the observed flow velocity suggests that the dunes are generated when the main axis of the meandering Kuroshio Current passes through this area, and that subsequent current velocities are sufficiently high to maintain the dunes up to the next event.  相似文献   

Heat and salt balances in the Seto Inland Sea   总被引：1，自引：0，他引：1  

Mayumi Murakami  Yukio Oonishi  Hideaki Kunishi 《Journal of Oceanography》1989,45(3):204-216

Seasonal variations of heat and salt balances are estimated in the Seto Inland Sea with the use of a numerical experiment.The surface effect is dominant with respect to the heat balance. In spring, however, the effect of the horizontal heat transport is the same as or greater than that of the surface heating (or cooling). Annual mean heat transport is 85 cal cm^–2 day^–1 (356 J cm^–2 day^–1) which is supplied from the open ocean and lost through the sea surface in the Inland Sea as a whole. Because of the shallow water depth, heat is supplied through the surface and carried out by the horizontal heat transport in Hiuchi- and Bingo-nada in the annual mean. The heat transport has the opposite sense to that in the whole Seto Inland Sea and annual mean transport is negative (–10 cal cm^–2 day^–1,i.e., –42 J cm^–2 day^–1).The salt balance is primarily controlled by the river discharge and the surface effect (precipitation) in June and July. In the other months, the effects of horizontal salt transport, of river inflow and of sea surface exchange (especially of the evaporation in autumn) are comparable to each other. In the Bungo Channel the river effect is relatively small. Osaka Bay and the Kii Channel are characterized by a smaller surface effect.Contribution No. 446 from Tohoku Regional Fisheries Research Laboratory.  相似文献   

Measurements of the Turbulent Energy Dissipation Rate around the Shelf Break in the East China Sea   总被引：1，自引：0，他引：1  

Takeshi?MatsunoEmail author  Manabu?Shimizu  Yasuhiro?Morii  Hideaki?Nishida  Yasuaki?Takaki 《Journal of Oceanography》2005,61(6):1029-1037

Using the micro-structure profiler, TurboMAP, large values for the turbulent energy dissipation rate ε were found just above the bottom of the shelf and around the thermocline near the continental shelf break in the East China Sea. The values found above the bottom are produced by the bottom stress due to tidal currents, resulting in a distinct bottom mixed layer where the vertical eddy diffusivity Kz is also large. Distinct maxima in the values of ε detected around the thermocline are located at the depth of the fine-scale shear maxima detected with the moored ADCP. The vertical profiles of ε were compared with those of the current velocity, and it was found that the maxima in ε appear to correspond to those of the shear with fine scale. The magnitude of the observed ε coincided approximately with the ε calculated from the fine-scale shear and the buoyancy frequency according to the parameterization proposed by Gregg (1989), if the large-scale mean shear caused by the Kuroshio is subtracted. However, it is not clear whether the parameterization for the internal wave fields in the open ocean is applicable to the estimation of ε in the shelf break. Whereas the most predominant value of ε was found just above the bottom and around the thermocline, the maxima of ε could be found in the internal area. They could have been caused by the propagation of the vertically high wave number internal tides along the characteristic ray.  相似文献   

Modeling the kinetics of silica nanocolloid formation and precipitation in geologically relevant aqueous solutions     

Christine F. Conrad  Gary A. Icopini  Hideaki Yasuhara  Joel Z. Bandstra  Peter J. Heaney 《Geochimica et cosmochimica acta》2007,71(3):531-542

The kinetics of the formation and precipitation of nanocolloidal silica from geologically relevant aqueous solutions is investigated. Changes in monomeric (SiO_2(mono)), nanocolloidal (SiO_2(nano)) and precipitated silica (SiO_2(ppt)) concentrations in aqueous solutions from pH 3 to 7, ionic strengths (IS) of 0.01 and 0.24 molal, and initial SiO₂ concentrations of 20.8, 12.5 and 4.2 mmolal (reported in [Icopini, G.A., Brantley, S.L., Heaney, P.J., 2005. Kinetics of silica oligomerization and nanocolloid formation as a function of pH and ionic strength at 25 °C. Geochim. Cosmochim. Acta69(2), 293-303.]) were fit using two kinetic models. The first model, termed the concentration model, is taken from Icopini et al. (2005) and assumes that the rate of change of SiO_2(mono) as a function of time has a fourth-order dependence on the concentration of SiO_2(mono) in solution. The second model, termed the supersaturation model, incorporates the equilibrium concentration of amorphous silica and predicts that polymerization will be a function of the degree of silica supersaturation in solution with respect to amorphous silica. While both models generally predicted similar rate constants for a given set of experimental conditions, the supersaturation model described the long-term equilibrium behavior of the SiO_2(mono) fraction more accurately, resulting in significantly better fits of the monomeric data. No difference was seen between the model fits of the nanocolloidal silica fraction. At lower pH values (3-4), a metastable equilibrium was observed between SiO_2(mono) and SiO_2(nano). This equilibrium SiO_2(mono) concentration was found to be 6 mmolal, or three times the reported solubility of bulk amorphous silica under the experimental conditions studied and corresponds to the predicted solubility of amorphous silica colloids approximately 3 nm in diameter. Atomic force microscopy was used to determine the average size of the primary nanocolloidal particles to be ∼3 nm, which is in direct agreement with the solubility calculations. Larger aggregates of the primary nanocolloids were also observed to range in size from 30 to 40 nm. This work provides the first kinetic models describing the formation and evolution of nanocolloidal silica in environmentally relevant aqueous solutions. Results indicate that nanocolloidal silica is an important species at low pH and neutral pH at low ionic strengths and may play a more important role in geochemical cycles in natural aqueous systems than previously considered.  相似文献   

The Current Structure of the Tsushima Warm Current along the Japanese Coast   总被引：4，自引：0，他引：4  

Hideaki Hase  Jong-Hwan Yoon  Wataru Koterayama 《Journal of Oceanography》1999,55(2):217-235

The branching of the Tsushima Warm Current (TWC) along the Japanese coast is studied based upon intensive ADCP and CTD measurements conducted off the Wakasa Bay in every early summer of 1995–1998, the analysis of the temperature distribution at 100 m depth and the tracks of the surface drifters (Ishii and Michida, 1996; Lee et al., 1997). The first branch of TWC (FBTWC) exists throughout the year. It starts from the eastern channel of the Tsushima Straits, flows along the isobath shallower than 200 m along the Japanese coast and flows out through the Tsugaru Strait. The current flowing through the western channel of the Tsushima Straits feeds the second branch of TWC (SBTWC) which develops from spring to fall. The development of SBTWC propagates from the Tsushima Straits to Noto Peninsula at a speed of about 7 cm sec⁻¹ following the continental shelf break with a strong baroclinicity. However, SBTWC cannot be always found around the shelf break because its path is influenced by the development of eddies. It is concluded that SBTWC is a topographically steered current; a current steered by the continental shelf break. Salient features at intermediate depth are the southwestward subsurface counter current (SWSCC) between 150 m and 300 m depths over the shelf region in 1995–1998 with the velocity exceeding about 5 cm sec⁻¹, although discrepancies of the velocity and its location are observed between the ADCP data and the geostrophic currents. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Optimization of causative factors using logistic regression and artificial neural network models for landslide susceptibility assessment in Ujung Loe Watershed,South Sulawesi Indonesia     

Andang Suryana SOMA  Tetsuya KUBOTA  Hideaki MIZUNO 《山地科学学报》2019,(2)

Landslide susceptibility maps(LSMs) play a vital role in assisting land use planning and risk mitigation. This study aims to optimize causative factors using logistic regression(LR) and an artificial neural network(ANN) to produce a LSM. The LSM is produced with 11 causative factors and then optimized using forward-stepwise LR(FSLR), ANN, and their combination(FSLR-ANN) until eight causative factors were found for each method. The ANN method produced superior validation results compared with LR. The ROC values for the training data set ranges between 0.8 and 0.9. On the other hand, validation with the percentage of landslide fall into LSM class high and very high, ANN method was higher(92.59%) than LR(82.12%). FSLR-ANN with nine causative factors gave the best validation results with respect to area under curve(AUC) values, and validation with the percentage of landslide fall into LSM class high and very high. In conclusion, ANN was found to be better than LR when producing LSMs. The best Optimization was combination of FSLR-ANN with nine causative factors and AUC success rate 0.847, predictive rate 0.844 and validation with landslide fall into high and very high class with 91.30%. It is an encouraging preliminary model towards a systematic introduction of FSLR-ANN model for optimization causative factors in landslide susceptibility assessment in the mountainous area of Ujung Loe Watershed.  相似文献   

Thermal Image Velocimetry     

Atsushi Inagaki  Manabu Kanda  Shiho Onomura  Hideaki Kumemura 《Boundary-Layer Meteorology》2013,149(1):1-18

A method for measuring the two-dimensional distribution of wind velocity vectors near a surface exposed to solar radiation, by tracking brightness temperature images instead of particle images, is proposed. It is based on time-sequential thermography with the algorithm used for particle image velocimetry. This thermal image velocimetry (TIV) was tested on a full-scale building wall covered by polystyrene boards attached side-by-side over a vertically elongated area measuring 22.2 m by 2.73 m. A thermal infrared camera was installed 8 m from the test wall to capture the wall-surface temperature at 30 Hz frequency. A sonic anemometer was also installed 35 mm from the surface used for validation of the TIV. The advection velocity estimated from thermal infrared imagery had a linear relationship with the wind velocity measured by the sonic anemometer, irrespective of the wind speed and direction. This linear slope was multiplied by the advection velocity of the thermal infrared image to rescale it to the wind velocity, and the term ‘TIV velocity’ was then used. A histogram and power spectra of the TIV velocity showed quantitatively good agreement with the velocity measured by the sonic anemometer, except for the high-frequency region of the spectra, where the TIV velocity was overestimated compared with that of the sonic anemometer. The method was also tested on ground covered by artificial turf to demonstrate its application to a horizontal plane with a wider area, extending for more than 80 m by 60 m.  相似文献   

Characteristics and possible origin of native aluminum in cold seep sediments from the northeastern South China Sea     

Zhong Chen  Chi-Yue Huang  Meixun Zhao  Wen Yan  Chih-Wei Chien  Muhong Chen  Huaping Yang  Hideaki Machiyama  Saulwood Lin 《Journal of Asian Earth Sciences》2011,40(1):363-370

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Gravity measurements with a portable absolute gravimeter A10 in Syowa Station and Langhovde,East Antarctica     

Takahito Kazama  Hideaki Hayakawa  Toshihiro Higashi  Shingo Ohsono  Shunsuke Iwanami  Tomoko Hanyu  Harumi Ohta  Koichiro Doi  Yuichi Aoyama  Yoichi Fukuda  Jun Nishijima  Kazuo Shibuya 《Polar Science》2013,7(3-4):260-277

Absolute gravity values were measured with a portable absolute gravimeter A10 in East Antarctica, for the first time by the Japanese Antarctic Research Expedition. This study aims to investigate regional spatiotemporal variations of ice mass distributions and associated crustal deformations around Syowa Station by means of repeated absolute gravity measurements, and we obtained the first absolute gravity value in Southern Langhovde on the Antarctic Continent. The average absolute gravity value at the newly installed benchmark AGS01 in Langhovde (obtained on 3 February 2012) was 982535584.2 ± 0.7 μgal (1 [μgal] = 1 × 10^?8 [m/s²]), which was in agreement with the gravity values obtained by the past relative gravity measurements within 1 mgal. In addition, the average absolute gravity value obtained at AGSaux in Syowa Station was consistent with both previous absolute gravity values and those obtained by simultaneous measurements using an FG5 gravimeter, owing to adequate data corrections associated with tidal effects and time variations in atomic clock frequencies. In order to detect the gravity changes associated with the ice mass changes and other tectonic phenomena, we plan to conduct absolute gravity measurements at AGS01 again and at other campaign sites around Syowa Station as well in the near future, with careful attention paid to the impacts of severe environmental conditions in Antarctica on gravity data collection.  相似文献