• Ocean Systems Engineering
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• 제5권4호
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• pp.319-329
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• 2015

Submerged breakwaters are used to prevent shore line erosion and sediment transportation. One of their advantages is low visual impact. In this paper, the effects of discontinuous submerged breakwaters over water surface elevation was numerically studied considering the extended Boussinesq equations as governing equations using MIKE21 software. The result of discontinuous breakwater was compared with a beach without breakwater. The results showed that the gap dramatically effects on surface elevation from shore line to offshore. It is also evident from results that with approaching the center of the gap, fluctuation of surface elevation is generated. It is because of passing longshore currents towards offshore through the gap which leads to an increase in sediment transportation rate. Nevertheless, transferring water mass from breakwater gap results in powerful rip currents leading to high changes on longshore wave profile.

• Ocean and Polar Research
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• 제23권2호
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• pp.161-172
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• 2001

A model-to-model comparison is attempted between Princeton Ocean Model (POM) and Miami Isopycnic Coordinate Ocean Model (MICOM) as a first step to extend our knowledge of models' performances in studying the East Sea circulation. The two models have fundamentally different numerical schemes and boundary conditions imposed on these models are not exactly the same each other. This study indicates that MICOM has a critical weak point in that it does not reproduce the shallow surface currents properly while it handles the thermohaline processes and associated movements of intermediate and deep waters efficiently. It is suggested that the mixed layer scheme needs to be modified so that it can match with inflow boundary conditions in order to reproduce the surface currents properly in MICOM. POM reproduces the surface current pattern better than MICOM, although the surface currents in POM appear to undergo the unrealistic seasonal variation and have exaggeratedly large vertical scale. These defects seem to arise during the process of adapting POM to the East Sea, and removing these defects is left as a future task.

• 한국해양학회지:바다
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• 제17권4호
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• pp.225-242
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• 2012

이 연구는 인공위성 고도계로 관측한 해수면 높이 자료를 이용하여 동해 표층해류를 생산하고, 동해 전체 영역에 대하여 동시성 있는 표층해류 분포를 동해 해류 정보 사용자에게 제공하기 위한 최초의 시도이다. 동해 전 영역에서 인공위성 고도계와 연안 조위관측소의 해수면 높이 자료를 동시에 얻을 수 있으므로 준실시간으로 넓은 해역에 대하여 동시성 있는 표층 지형류의 산출이 가능하다. 산출된 동해 표층 지형류로부터 주요 해류의 위치와 세기 그리고 중규모 이상의 소용돌이 발달 양상을 살펴볼 수 있다. 따라서 이들 해류의 이름과 평균적인 위치를 알 수 있도록 동해 해양지명에 대한 명칭과 위치를 기술하고, 개념적인 해류도를 제시하였다. 동해 해류정보가 실제 실용화될 수 있도록 인공위성 고도계 자료를 이용하여 산출한 지형류의 월 계절 연도별 해류 분포 예를 들고, 각 해류 분포를 설명하였다. 또한 시 공간적으로 변화하는 동해 표층해류 분포 형태를 객관적으로 분류하기 위하여 16년(1993~2008년)간의 표층해류 자료를 경험직교함수(Empirical Orthogonal Function, EOF)를 이용하여 분석하였다. EOF분석 제1모드(mode)는 주로 한국 동해안을 따라 북쪽으로 흐르는 동한난류와 야마도분지 남서부 시계방향 순환의 강화 또는 약화를 나타냈다. 제2모드는 동한난류가 동해 남부를 가로지르며 사행하는 정도를 나타냈으며, 해류 사행의 파장은 약 300 km이었다. 제1모드와 제2모드가 모두 해류의 연간 변동성을 나타냈으며, 제1모드와 제2모드의 시간계수에 따라 동해 표층해류 분포를 관성 경계류 패턴(pattern), 대마난류 패턴, 사행 패턴, 외해분지류 패턴으로 분류할 수 있다.

• 구강회복응용과학지
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• 제19권3호
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• pp.195-206
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• 2003

Several factors can affect the formation of bone tissues surrounding implants. One of the factors is electrical stimulation. It is known to change the movement of cells, form and destroy cells, and alter concentration and chemical component of soft tissues and bones. The effect of electrical stimulation on bone formation can vary according to the intensity of electric currents, stimulating time, the method of sending electric currents, and tissues and cells currents are applied to. This study examines how various enviroments affect osteoblasts. (1) effect on osteoblast with varying intensity of currents Osteoblast-like cells were raised on four plates where implants can be placed. A constant current sink (MC3T3-E1) that can adjust the intensity and stimulating time of electric currents was used. The four plates were stimulated with $0{\mu}A$, $10{\mu}A$, $20{\mu}A$, and $40{\mu}A$, respectively. After 24 hours of stimulation, the number and distribution of cells surrounding implants were examined. (2) effect on osteoblast with varying conditions The 3 study was performed with same method. (1) The change of attached cell number 72-hour after application of various currents (2) The change of attached cell number 72-hour after application of various interval (3) The comparison of attached cell number by implant surface texture The following are the results: 1. The distribution and density of cells surrounding implant is highest under the intensity of electric currents of $20{\mu}A$. 2. The number of cells attached implants is highest under the intensity of electric currents of $20{\mu}A$. 3. The number of cells attached implants is highest under continous electric currents 4. The number of cells attached implants is not different by implant surface texture.

• 한국해안해양공학회지
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• 제7권4호
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• pp.379-392
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• 1995

대한해협의 유황, 표류 예측모형을 수립하기 위한 초기노력을 수행하였는데 첫 대상해역은 대한해협주변해역으로 하였다. 해류의 요인별 Data Table에 의거한 시공적 유황예측에 의한 표류예측 시뮬레이션을 수행하여 이 해역에서 관측된 위성추적부표의 결과와의 비교로서 모형의 검증을 수행하였는데 비교적 좋은 일치를 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.88-90
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• 1998

In this paper, the indirect BIEM(boundary integral equation method) is adopted to analyze 3-D eddy currents in cover plate of power transformer. In indirect BIEM, the equivalent magnetic surface charge density and the eqivalent magnanetic surface current density are the unknowns. Using triangular constant elements, the integral equations are discretized into boundary element equations of minimum order. Eddy currents are obtained in terms of euqivalent magnetic surface sources. And the locad overheating can be predicted using the eddy currents distribution in cover plate of power transformer.

• 한국해양공학회지
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• 제30권4호
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• pp.320-326
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• 2016

Rip current forecasts, based on intensity, are marked in four levels—notice, watch, warning, and danger. However, numerical results are represented by current vectors, whose magnitudes are then converted into predictive levels. In the present study, the rose diagram is adapted as a determinative forecasting index and examined for the case of an ideal rip channel consisting of surface, bottom, and averaged currents. Further, it is employed in the sensitivity analysis of wave-induced currents generated by wave conditions at the Haeundae Beach. The simulation of surface onshore and bottom undertow currents is accomplished by including a mass flux term in the wave-averaged continuity equation.

• 조명전기설비학회논문지
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• 제25권4호
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• pp.97-103
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• 2011

The most important object of grounding systems is to protect human being from electric shock. Touch and step voltages are measured to evaluate the performances of grounding systems. Dangerous voltages have been largely studied by the power frequency fault currents, on the other hand, the ground current containing the high frequency components and surge currents haven't been considered. Many attempts about the grounding impedances reported in these days show that the performance of the grounding systems in high frequency range is very different with the ground resistance. It is necessary to analyze the dangerous voltages formed by the ground currents containing high frequency components. In this paper, the ground surface potential rises near the vertical and horizontal grounding electrodes are measured at the frequency of 100[Hz], 30[kHz], and 100[kHz]. Dangerous voltages are investigated with the frequency-dependent grounding impedance. As a result, the ground surface potential rise is increased as the grounding impedance increases. Touch and step voltages near the grounding electrode whose impedance increases with the frequency are sharply raised.

• 한국수산과학회지
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• 제26권4호
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• pp.346-352
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• 1993

Tidal currents and tidal residual currents in Chinhae Bay are investigated by the field observations and hydraulic experiments during the spring tide and neap tide. The horizontal and vertical scales of the model are l/2,000 and 1/159, respectively. The hydraulic model results roughly coincide with the field data. Maximum tidal currents during the spring tide and neap tide in the central channel of Chinhae Bay are strong as about 90 and 30cm/s respectively, and strong tidal residual currents take place. Maximum tidal currents during the spring tide and neap tide in the western and northern part of the bay are weak as below 30 and 10cm/s respectively, and also tidal residual currents are weak. Tidal residual currents rotating clockwise occur in the central part of the bay. Northward tidal residual currents in the northern part of Kajo-do are predominant, whereas southward ones in the southern part of Kajo-do are remarkable. The surface currents in the bay depend strongly on the wind and river flow, and it seems to be remarkable during the neap tide.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.83-86
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• 1994

On this paper, the structural changes of molecules on the water surface were monitored by the measuring system of displacement currents. The measuring system was constructed at home-made Kuhn type LB(Langmuir -Blodgett) deposition apparatus. Solutions of 4-octyl -4\\`- (5-car boxy$.$ -pentamethyleneoxy) azobenzene molecules (8A5H) and stearic acid(C$\_$18/) were spreaded at the air-water interface respectively, and the currents inducted by the dynamic behavior of molecules were measured when the molecules were the molecules were pressed by barrier. From C$\_$18/ mo1ecules two distinct peaks of displacement currents were obtained, which show that the orientations of mo1ecules were charged largely at these Points. The reversibility of displacement currents by compression and expansion was obtained from 8A5H molecules, which shows the compressed molecules which shows the compressed molecules have a tendency to disperse after the compression. But it was not obtained from C$\_$18/ molecules which means that this molecules disperse not easily by decreasing the pressure of the barrier.