Wintertime temperature-salinity characteristics in the southeastern Hwanghae (Yellow Sea)     

Heung -Jae Lie 《Journal of Oceanography》1985,41(5):291-298

Wintertime temperature-salinity properties of the southeastern Hwanghae (Yellow Sea) were analysed, based on long-term hydrographic data gathered between 1961 and 1980. A strong thermohaline front is formed in the area west of Cheju-do (along 33?40′N in the region bounded by 124? E and 126?20′E) during winter and extends to the bottom. This surface-to-bottom front, running from west to east, divides water properties into two types: one type of low temperature and low salinity to the north of the front and another one of high temperature and high salinity to the south of the front. The existence of the front suggests that there is no northward flow in the study area, a finding which runs counter to the conventional belief that there is the Hwanghae Warm Current carrying waters of high temperature and salinity to the north. T-S diagrams show that in winter the Hwanghae Warm Current Water and the Hwanghae Cold Water are the representative water masses in the study area.  相似文献   

Experimental Investigation into the performance of the Axial-Flow-Type Waterjet according to the Variation of Impeller Tip Clearance   总被引：1，自引：0，他引：1  

Moon-Chan Kim  Ho-Hwan Chun 《Ocean Engineering》2007,34(2):275-283

The tip clearance inside the duct from the tip of the impeller is very important to the performance of waterjet systems, which fact has been proven in the pump field. The tip clearance is especially important on the model scale because it is very difficult in manufacture to keep the tip clearance constant and minimally small along the inside of the duct. In the present study, a flush-type waterjet propulsion unit (duct, impeller, stator, and nozzle) was designed for an amphibious tracked vehicle. Two impellers of different inner diameter were designed and manufactured in order to investigate the gap effect. Resistance and self-propulsion tests with a 1/5-scale model were conducted in PNU towing tank. The flow rate at the nozzle exit, the static pressure at the various sections along the duct and also the nozzle, the revolution of the impeller, and the torque, thrust, and towing forces at various advanced speeds were measured. Based on these measurements, the performance was analyzed according to the ITTC 96 standard analysis method. Based on this analysis method, the full-scale effective and delivered power of the tracked vehicle was estimated according to the variation of tip clearance.  相似文献   

Wave reflection from partially perforated-wall caisson breakwater   总被引：2，自引：0，他引：2  

Kyung-Duck Suh  Jae Kil Park  Woo Sun Park   《Ocean Engineering》2006,33(2):264-280

In 1995, Suh and Park developed a numerical model that computes the reflection of regular waves from a fully perforated-wall caisson breakwater. This paper describes how to apply this model to a partially perforated-wall caisson and irregular waves. To examine the performance of the model, existing experimental data are used for regular waves, while a laboratory experiment is conducted in this study for irregular waves. The numerical model based on a linear wave theory tends to over-predict the reflection coefficient of regular waves as the wave nonlinearity increases, but such an over-prediction is not observed in the case of irregular waves. For both regular and irregular waves, the numerical model slightly over- and under-predicts the reflection coefficients at larger and smaller values, respectively, because the model neglects the evanescent waves near the breakwater.  相似文献   

Three cletodid copepods of the genera<Emphasis Type="Italic">limnocletodes</Emphasis> and<Emphasis Type="Italic">kollerua</Emphasis> (harpacticoida,cletodidae) from coastal marshes and estuaries in south Korea     

Ji Min Lee  Cheon Young Chang 《Ocean Science Journal》2007,42(4):255-267

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Water mass formation variability in the intermediate layer of the east sea     

Hong Sik Min  Cheol -Ho Kim 《Ocean Science Journal》2006,41(4):255-260

Long-term variability in the intermediate layer of the eastern Japan Basin has been investigated to understand the variability of water mass formation in the East Sea. The simultaneous decrease of temperature at shallower depths and oxygen increasing at deeper depths in the intermediate layer took place in the late 1960’s and the mid-1980’s. Records of winter sea surface temperatures and air temperatures showed that there were cold winters that persisted for several years during those periods. Therefore, it was assumed that a large amount of newly-formed water was supplied to the intermediate layer during those cold winters. Close analysis suggests that the formation of the Upper Portion of Proper Water occurred in the late 1960’s and the Central Water in the mid-1980’s.  相似文献   

Robust diagnostic modeling of the Japan Sea circulation   总被引：1，自引：0，他引：1  

Y. H. Seung  J. -H. Yoon 《Journal of Oceanography》1995,51(4):421-440

The Japan Sea circulation is numerically modeled with robust diagnostic terms included. The general features are nearly the same as previous prognostic models though small differences appear in local current fields, and agree with most of existing observation results. This model, however, seems to be more successful than prognostic ones in that the overshooting of the East Korean Warm Current, a northward western boundary current, is much reduced and the North Korean Cold Current, a southward western boundary current, is more enhanced. Based on the model results, discussions are made about the large convective structure and the global kinetic energy budget of the Japan Sea circulation.  相似文献   

Bragg resonant reflection of carrier waves composing wave groups     

Yong-Sik Cho  Jae-Sang Jung   《Ocean Engineering》2006,33(1):82-92

Numerical analyses for the Bragg resonant reflection of carrier waves associated long waves due to sinusoidally varying seabeds are performed by using a set of coupled ordinary differential equations derived from the Boussinesq equations. The Boussinesq equations are firstly approximated with the Fourier decomposition. The coupled governing equations are then derived and used to simulate evolution of both short and long wave components. It is also found that wave groups are generated by two carrier waves with slightly different frequencies. The wave energy of the initial wave components is transferred to other harmonic components during propagation over a long distance. Evolution and reflection of both short and long waves were largely affected by nonlinearity.  相似文献   

Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors   总被引：1，自引：0，他引：1  

Won Duk Yoon  Joon Yong Yang  Donghyun Lim  Sung Hwan Cho  Gyung Soo Park 《Ocean Science Journal》2006,41(1):11-29

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature, however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River Diluted Water. Four euphausiid species were identified:Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. andStylocheron affine. E. sanzoi andS. affine were collected, just one juvenile each, from the southern area in June and December, respectively.Pseudeuphausia sp. were collected in the eastern area all the year round except June.E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance. Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis, egg). From spring to fall,E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the near-coastal area with similar pattern for furcilia and calyptopis. The distribution pattern ofE. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll a showed a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll a and phytoplankton concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water current affect the distribution ofE. pacifica in the Yellow Sea.  相似文献   

A hierarchical real-time control architecture for a semi-autonomous underwater vehicle   总被引：1，自引：0，他引：1  

Ji-Hong Li  Bong-Huan Jun  Pan-Mook Lee  Seok-Won Hong 《Ocean Engineering》2005,32(13):282-1641

This paper describes a real-time control architecture for Dual Use Semi-Autonomous Underwater Vehicle (DUSAUV), which has been developed at Korea Research Institute of Ships and Ocean Engineering (KRISO) for being a test-bed of development of underwater navigation and manipulator technologies. DUSAUV has three built-in computers, seven thrusters for six DOF motion control, one 4-function electric manipulator, one ballasting motor, built-in power source, and various sensors. A supervisor control system with GUI and a multi-purpose joystick is mounted on the surface vessel and communicates with vehicle through a fiber optic link. Furthermore, QNX, one of real-time operating system, is ported on the built-in control and navigation computers for real-time control purpose, while Microsoft OS product is ported in the supervisor computer for GUI programming convenience. A hierarchical control architecture, which consists of application layer, real-time layer and physical layer, has been developed for efficient control system of above complex underwater robotic system. The experimental results with implementation of the layered control architecture for various motion control of DUSAUV in an ocean engineering basin of KRISO is also presented.  相似文献   

Identification of Pb sources in Yellow Sea sediments using stable Pb isotope ratios   总被引：1，自引：0，他引：1  

Man-Sik Choi  Hi-Il Yi  Shou Ye Yang  Chang-Bok Lee  Hyun-Ju Cha 《Marine Chemistry》2007

Rapid economic developments in East Asian countries have inevitably resulted in environmental degradation in the surrounding seas, and concern for both the environment and protection from pollutants is increasing. Identification of sources of contaminants is essential to environmental pollution management. In this study, the provenance of anthropogenic lead (Pb), a major pollutant of Yellow Sea sediments, was determined for river mouth sediments, including those of the Changjiang, Huanghe, Han, and Geum Rivers, and for age-determined shelf core sediments through the measurement of Pb isotope ratios in the HCl-leached fraction using multi-collector inductively coupled plasma-mass spectrometry (MC ICP/MS). Anthropogenic Pb has accumulated in shelf core sediments since 1910, and its isotope ratios were estimated as 0.863–0.866 and 2.119–2.125 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively, from the mixing relationships of the two endmembers. River mouth sediments exhibited enough distinction in anthropogenic Pb isotope ratios to be discriminated: 0.874 (2.144) in the Huanghe, 0.856 (2.129) in the Han, 0.857 (2.122) in the Geum, and 0.854 (2.101) in the Changjiang for ²⁰⁷Pb/²⁰⁶Pb (²⁰⁸Pb/²⁰⁶Pb), respectively. Although isotope ratios of geogenic Pb in sediments dating before 1910 showed narrow ranges (0.842–0.845 and 2.088–2.100 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively), distinct isotope ratios in each core permitted source identification of sediments in the Yellow Sea based on geographic locations and the geogenic Pb of each river. By comparing the isotope ratios of the estimated anthropogenic Pb to source-related materials, the provenances of anthropogenic Pb in Chinese river sediments were presumed to be Chinese coal or ore, which is also a major source of atmospheric particulate Pb. The anthropogenic Pb in the shelf core sediments in the northern Yellow Sea originated from northern Chinese cities such as Beijing and Tianjin through atmospheric pathways. Pb isotope ratios indicated that Pb in Korean river sediments was characteristic of local Korean ores.  相似文献