Internal wave dispersions in density-stratified deep oceans with a thermocline     

Jae Min Hyun 《Journal of Oceanography》1977,33(1):16-22

As to two typical Väisälä frequency profiles in deep oceans, one in the Arctic Ocean and one in the Atlantic, the approximate analytical method ofHyun (1976) is used to calculate internal wave dispersion relations. The method is shown to have good agreement with the matrix numerical method. By making calculations for an exemplary Väisälä frequency profile with a thermocline, an assessment is made of the inaccuracies in the dispersion curves obtained by the ordinary WKB method which does not take into account the turning point singularities.  相似文献   

Numerical flow simulation of flush type intake duct of waterjet   总被引：1，自引：0，他引：1  

Warn-Gyu Park  Hyun Suk Yun  Ho Hwan Chun  Moon Chan Kim 《Ocean Engineering》2005,32(17-18):2107-2120

Waterjet propulsion system is widely used to thrust high speed marine vessels in excess of 30–35 knots by virtue of high propulsive efficiency, good maneuverability, and less vibration. Since, however, approximately 7–9% of the total power is lost in intake duct due to flow separation, nonuniformity, etc., detail understanding of flow phenomena occurring within intake duct is essential to reduce the power loss. The present work solved 3D incompressible RANS equations on multiblocked grid system of the flush type intake duct of waterjet. The numerical results of surface pressure distributions, velocity vectors, and streamlines were compared with experiments and good agreements were obtained for three jet velocity ratios. Strong suction flow through the inlet was shown and the vortex induced by the separation along the corner of the side wall was clearly shown. Flow separation on the lip was also observed. The location of stagnation point on the lip was well predicted, in accordance with PIV measurement.  相似文献   

The Effects of Microstructure on Shear Properties of Shallow Marine Sediments     

Gil Y. Kim  Hong J. Yoon  Jin W. Kim  Dae C. Kim  Boo K. Khim  Seok Y. Kim 《Marine Georesources & Geotechnology》2007,25(1):37-51

This study was undertaken to investigate the implication of geoacoustic behaviors in the shallow marine sediments associated with the changes in geotechnical index properties. Two piston cores (270 cm and 400 cm in core length) used in this study were recovered from stations 1 and 2, the western continental margin, the East Sea. Scanning electron microscopy (SEM) was employed to illustrate the effects of microstructure on shear properties. The direct SEM observation of sediment fabrics is inevitable to understand the correlation of the changes in geoacoustic properties to the sediment structure. The consolidation of sediments by overburden stress resulting in the clay fabric alteration appears to play an important role in changing shear properties. Water contents and porosity of sediments gradually decreases with increasing depth, whereas wet bulk density shows a reverse trend. It is interesting to note that shear wave velocities increase rapidly from 8 to 20 m/s while compressional wave velocities significantly fluctuate, ranging from 1450 to 1550 m/s with depth. The fabric changes in sediment with increasing depth for example, uniform grain size and well oriented clay fabrics may cause the shear strength increase from 1 to 12 kPa. Shear wave velocity is, therefore, shown to be very sensitive to the changes in undrained strength for unconsolidated marine sediments. This correlation allows an in-situ estimation of shear stress in the subsurface from shear wave velocity data.  相似文献   

Separation of incident and reflected waves in wave–current flumes     

Kyung Doug Suh  Woo Sun Park  Beom Seok Park 《Coastal Engineering》2001,43(3-4)

A technique is developed to separate the incident and reflected waves propagating on a known current in a laboratory wave–current flume by analyzing wave records measured at two or more locations using a least squares method. It can be applied to both regular and irregular waves. To examine its performance, numerical tests are made for waves propagating on quiescent or flowing water. In some cases, to represent the signal noise and measurement error, white noise is superimposed on the numerically generated wave signal. For all the cases, good agreement is observed between target and estimation.  相似文献   

Alkaline phosphatase activity and phosphatase hydrolyzable phosphorus for phytoplankton in hiroshima bay, Japan     

Seok Jin Oh  Yang Ho Yoon  Tamiji Yamamoto  Yukihiko Matsuyama 《Ocean Science Journal》2005,40(4):183-190

We investigated the seasonal variability of free alkaline phosphatase activity in seawater and alkaline phosphatase hydrolysable phosphorus (APHP) at 3 stations in Hiroshima Bay using alkaline phosphatase extracted from the dinoflagellates Alexandrium tamarense and Gymnodinium catenatum. The dissolved inorganic phosphorus (DIP) was lower than 1 μM in all samples; the lowest values were in May. The amount of APHP was high at the surface and bottom waters of all stations in May, showing DIP-depleted conditions. In August and November, the amount of APHP was much less than the amount of APHP in May, indicating that the availability of dissolved organic phosphorus (DOP) for these species was low and/or uptake during the dinoflagellate blooming might have occurred in the area. The results obtained from short-term variations of AP activity might suggest that the growth of dinoflagellates in this season may be partly supported by the AP produced by other diatoms.  相似文献   

Effect of environmental conditions on variation in the sediment-water interface created by complex macrofaunal burrows on a tidal flat   总被引：1，自引：0，他引：1  

Bon Joo Koo  Kae Kyoung Kwon  Jung-Ho Hyun 《Journal of Sea Research》2007,58(4):302-312

We quantified the increase in the sediment-water interface created by the burrowing activities of the resident macrofaunal community and its variation with respect to the physical conditions of the habitat on a tidal fat. We investigated environmental factors and dimensions of macrofaunal burrows with respect to tidal height and vegetation during spring and summer at three sites. A resin-casting method was used to quantify the dimensions of all burrows at each site. The dimensions of macrofaunal burrows varied both temporally and spatially and the increase in the sediment-water interface reached a maximum of 311%, ranging from 20 to 255% under different habitat conditions. The sediment-water interface depended on the duration of exposure resulting from tidal height, increased temperatures resulting from seasonality, and marsh plant density. Burrows were deeper and more expansive at both higher tidal levels and higher temperatures in summer. Burrow dimensions were sharply reduced with the disappearance of adult macrofauna in areas where the roots of the marsh plant Suaeda japonica were dense. The significance of this study lies in quantifying the burrow dimensions of the entire macrofaunal community, rather than just a single population, and confirming their spatial and temporal variation with respect to physical conditions of the habitat. Environmental factors responsible for variation in burrow dimensions are discussed.  相似文献   

Changes in spatial variations of sap flow in Korean pine trees due to environmental factors and their effects on estimates of stand transpiration     

Minkyu Moon  Taekyu Kim  Juhan Park  Sungsik Cho  Daun Ryu  Sanguk Suh  Hyun Seok Kim 《山地科学学报》2016,13(6):1024-1034

It is difficult to scale up measurements of the sap flux density (Js) for the characterization of tree or stand transpiration (E) due to spatial variations in JS and their temporal changes. To assess spatial variations in the sap flux density of Korean pine (Pinus koraiensis) and their effects on E estimates, we measured the Js using Granier-type sensors. Within trees, the Js decreased exponentially with the radial depth, and the Js of the east aspects were higher than those of the west aspects. Among trees, there was a positive relationship between Js and the tree diameter at breast height, and this positive relationship became stronger as the transpiration demand increased. The spatial variations that caused large errors in E estimates (i.e., up to 110.8 % when radial variation was ignored) had varied systematically with environmental factors systematic characteristics in relation to environmental factors. However, changes in these variations did not generate substantial errors in the E estimates. For our study periods, the differences in the daily E (E _D) calculated by ignoring radial, azimuthal and tree-to-tree variations and the measured E _D were fairly constant, especially when the daily vapor pressure deficit (D__D) was higher than 0.6 kPa. These results imply that the effect of spatial variations changes on sap flow can be a minor source of error compared with spatial variations (radial, azimuthal and tree-to-tree variations) when considering E estimates.  相似文献   

<Emphasis Type="Italic">In-situ</Emphasis> measured primary productivity of ice algae in Arctic sea ice floes using a new incubation method     

Ho Jung Song  Jae Hyung Lee  Gawn Woo Kim  So Hyun Ahn  Houng-Min Joo  Jin Young Jeong  Eun Jin Yang  Sung-Ho Kang  Sang Heon Lee 《Ocean Science Journal》2016,51(3):387-396

Recent changes in climate and environmental conditions have had great negative effects such as decreasing sea ice thickness and the extent of Arctic sea ice floes that support ice-related organisms. However, limited field observations hinder the understanding of the impacts of the current changes in the previously ice-covered regions on sea ice algae and other ice-related ecosystems. Our main objective in this study was to measure recent primary production of ice algae and their relative contribution to total primary production (ice plus pelagic primary production). In-situ primary productivity experiments with a new incubation system for ice algae were conducted in 3 sea ice cores at 2 different ice camps in the northern Chukchi Sea, 2014, using a ¹³C and ¹⁵N isotope tracer technique. A new incubation system was tested for conducting primary productivity experiments on ice algae that has several advantages over previous incubation methods, enabling stable carbon and nitrogen uptake experiments on ice algae under more natural environmental conditions. The vertical C-shaped distributions of the ice algal chl-a, with elevated concentrations at the top and bottom of the sea ice were observed in all cores, which is unusual for Arctic sea ice. The mean chl-a concentration (0.05 ± 0.03 mg chl-a m^?3) and the daily carbon uptake rates (ranging from 0.55 to 2.23 mg C m^?2 d^?1) for the ice algae were much lower in this study than in previous studies in the Arctic Ocean. This is likely because of the late sampling periods and thus the substantial melting occurring. Ice algae contributed 1.5–5.7% of the total particulate organic carbon (POC) contents of the combined euphotic water columns and sea ice floes. In comparison, ice algae contributed 4.8–8.6% to the total primary production which is greater than previously reported in the Arctic Ocean. If all of the ice-associated productions were included, the contributions of the sea ice floes to the total primary production would be greater in the Arctic Ocean and their importance would be greater in the arctic marine ecosystems.  相似文献   

<Emphasis Type="Italic">Dracograllus trukensis</Emphasis> sp. nov. (Draconematidae: Nematoda) from a seagrass bed (<Emphasis Type="Italic">Zostera</Emphasis> spp.) in Chuuk Islands,Micronesia, Central Western Pacific Ocean     

Wongi Min  Dongsung Kim  Wilfrida Decraemer  Hyun Soo Rho 《Ocean Science Journal》2016,51(3):343-354

A new species of free-living marine draconematid nematode, Dracograllus trukensis sp. nov., is described based on the specimens collected from the sediments of a intertidal seagrass bed from Chuuk Islands, Micronesia. Dracograllus trukensis sp. nov. differs from other species of the genus by the combination of the following characteristics: the presence of numerous minute spiny ornamented body cuticular annules in both sexes, eight cephalic adhesion tubes inserted on the head capsule in both sexes, the presence of stiff posteriorly directed setae anterior to posterior adhesion tubes in both sexes, the shape (large, elongated, open loop-shaped in male and large, elongated, closed loop-shaped in female) and position (longer ventral arm extending to the first body annule in male) of amphideal fovea, shorter spicule length (34–42 μm), the presence of sexual dimorphism in shape and length of the non-annulated tail terminus, and number of posterior sublateral adhesion tubes (10 in male and 13–15 in female) and posterior subventral adhesion tubes (8–10 in male and 9–11 in female). A comparative table on the biogeographical and ecological characteristics of the species of Dracograllus is presented. This is the first taxonomic report on the genus Dracograllus from Chuuk Islands, Micronesia, central western Pacific Ocean.  相似文献   

Assessing and prioritizing environmental hazards associated with abandoned mines in Gangwon-do,South Korea: the Total Mine Hazards Index     

Sung-Min Kim  Jangwon Suh  Sungchan Oh  Jin Son  Chang-Uk Hyun  Hyeong-Dong Park  Seung-Han Shin  Yosoon Choi 《Environmental Earth Sciences》2016,75(5):369

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