• 한국농공학회논문집
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• 제47권5호
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• pp.3-13
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• 2005

The present study examined the 3 dimensional space distribution characteristics of sea water intrusion using data available from previous observations. For this study, we used 3D FEMWATER, which is a 3 dimensional finite element model. The target area was around Daechang-ri, Gimje-si, Jeollabuk-do. The area is relatively easy to formulate a conceptual model and has observation wells in operation for surveying sea water intrusion. Considering the uncertainty of numerical simulation, we analyzed sensitivity to hydraulic conductivity, which has a relatively higher effect. According to the result of the analysis, the variation of TDS concentration had an error range of $-1,336{\~}+107 mg/{\iota}$. Taking note that the survey data from observation wells were collected when the boundary between fresh water and sea water in the aquifer was in equilibrium, we set the range of time for numerical simulation and estimated the spatial distribution of TDS concentration as the range of sea water intrusion. According to the result of estimation, the spatial distribution of TDS concentration calculated when 1,440 days were simulated was taken as the range of sea water intrusion. Using the result of calculation, we can draw not only vertical views for a certain section but also horizontal views of different depth. These views will be greatly helpful in understanding the spatial distribution of the range of sea water intrusion. In addition, the result of this study can be used rationally in proposing an optimal quantity of water pumping through investigating the moving route of sea water intrusion over time in order to prevent excessive water pumping and to maintain an optimal number of water pumping wells per interval.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.641-646
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• 1998

The structures exposed to marine environment do not show long-term durability due to corrosion of steel and deterioration of concrete by the attack of various salts dissolved in sea water. In this study, Partial substitution of cement with fly ash(20%) or blast furnace slag(40%) was made together with the addition of 4 different corrosion-inhibitors, as a protective measure of concrete structures against chemical attack of salts. Combined effects of mineral and corrosion-inhibiting admixtures were tested by measuring the resistance and compressive strength of concretes under the simulated tidal condition, which consists of alternating 12 hour periods of immersion in artificial sea water and drying in air. Both the strength and concrete resistance were found to decrease in following order, regardless of the corrosion inhibitors the concretes with blast furnace slag, those with fly ash and those without any mineral admixtures. The interrelation between compressive strength of concrete and resistance was investigated.

• 대한원격탐사학회지
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• 제15권3호
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• pp.227-238
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• 1999

발사 이전에 OSMI 모의 복사량을 산출함은 실제로 관측할 자료를 추정하고, 자료처리를 위한 준비에 매우 유용하다. 1999년 발사예정인 다목적 실용위성의 탑재체 중의 하나인 OSMI 자료처리 시스템은 SeaWIFS 자료처리 시스템을 OSMI에 맞추어 재개발된 것이다. 모의 복사량 계산은 OSMI 센서의 파장대역 및 스캔방식, 다목적 실용위성의 궤도에 관한 정보가 고려되어야 한다. 본 연구에서는 대양에서의 OSMI 모의 복사량을 산출하기 위해 CZCS에서 관측한 엽록소를 다목적 실용위성이 관측한다는 가정을 하게 되었다. 궤도 예측에는 수정된 Brouwer-Lyddane 모델이, water-leaving 복사량을 산출하기 위해 CZCS 엽록소 농도가, OSMI가 관측할 대기에 의한 복사량 계산에는 여러 가지 복사모델이 이용되었다. OSMI의 412, 443, 490, 555, 765, 865nm 6가시광선 파장대역에서 모의 복사량을 산출하였다. 예상대로, 총 복사량 중 water-leaving 복사량은 아주 작으며 (10% 미만), 태양해면반사에 의한 영향은 태양 적위 근처에서 관측된다. 그러므로 대기보정은 총 복사량으로부터 엽록소 농도를 계산하는데 매우 중요하다. 태양해면반사에 의해 영향을 받는 자료는 사용할 수 없으므로 OSMI 임무 기간내에 지속적인 전구 해양관측을 위해서는 체계적인 자료수집 계획이 요구된다.

• 한국해안·해양공학회논문집
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• 제28권1호
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• pp.13-26
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• 2016

일반적으로 해수위 변동은 조석, 기상, 수온, 염분, 파랑, 지형 등 다양한 요인에 의해 영향을 받는다. 비조석 외력 조건 중 대기압 변화는 수위 변화를 유발하는 큰 요인 중 하나이다. 수위 변동을 예측함에 있어 서해와 달리 조차가 작은 동해 연안은 조석 성분만을 외력 조건으로 고려하여 관측 수위를 재현하기는 현실적으로 어렵다. 본 연구에서는 동해 연안의 수위 예측 및 재현 시 대기압의 시간적 변화가 수위의 변화에 미치는 영향을 검토하고자 Telemac-2D 모형에 역기압 효과(IBE, Inverted Barometer Effect)를 반영하여 수치 모의를 실시하고 그 결과를 검토하였다. 역기압 효과와 조석을 동시에 반영한 예측 결과는 조석만을 반영한 예측결과보다 관측 자료와의 상관도가 크게 증가함으로 동해 연안 관측 수위의 수치 재현에 역기압 효과가 반드시 반영되어야함을 확인하였다.

• 한국지진공학회논문집
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• 제2권1호
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• pp.11-21
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• 1998

해상에 설치된 기초말뚝의 경우 지진의 3가지 성분 즉, 지반의 수평운도, 지반의 연직진동에 의해 발생된 상부구조물과의 피드백 (feedback)에 의한 말뚝의 연직진동, 그리고 지반의 연직진동에 의해 유발된 해진(seaquake)의 진동이 말뚝 기초의 거동에 영향을 미친다. 본 연구에서는 유발된 해진의 진동을 해저면에서 유사화된 sine 정현파 형상의 동수압으로 모델링하였다. 해진(seaquake) 작용중 약 220m 이상의 심해에 설치된 개단 말뚝의 지지력은, 지반내에 유발된 과도한 과잉 간극수압으로 인하여, 심각하게 저감도었으며, 관내토 폐쇄력도 80% 이상 감소되었다. 해진중 관내토 선단 하부에서 발생된 과도한 과잉 간극수압으로 인하여 관내토내에 과도한 상향의 침투력이 유발되어 관내토 폐색이 손상되었다. 약 220m 이하의 천해에 설치된 개단말뚝의 지지력은 해진에 의해 약 10% 감소하였으며, 관내토의 폐쇄력은 5%이하만큼 감소하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.81-88
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.645-649
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• 2005

In this study, redesign of a vaporizer sea-water pump has been carried out using computational fluid dynamics. The flow field of the specified pump model is simulated and analyzed. In the flow analysis full pump model has been used, and multi-block grids are employed to solve the governing equations. In order to improve pump efficiency, systematic redesign has been performed to remove the flow recirculation near the hub of the diffuser vanes. The modified model shows about 4 % improvement in pump efficiency compared to the given model.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.199-202
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• 2008

It is well-known fact that tidal difference between the ebb and flow in Yellow Sea is about 9 m so that it has largest value in the world. This wide range of tide level enables Yellow Sea water to intrude into main stream of Han River. However, the study of the tidal reach of Han River has not been carried out thoroughly since North and South Koreas share this region so that topography data and physical measurement are lacking. In this study, to examine the reverse flow and dispersion behavior by tidal effect at the tidal reach of Han River, 2-D river analysis models were applied. RMA-2 was applied to calculate the horizontal velocities and water surface elevation. With the results of velocities and water depth, RAM4, which is 2-D advection-dispersion model based on FEM was simulated to analyze the horizontal transport behavior of BOD.

• 한국초전도ㆍ저온공학회논문지
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• 제23권3호
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• pp.10-13
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• 2021

The method of removing micro-plastics from sea water has been developed using electro-magnetic force. Plastics are difficult to decompose and put a great load on the marine environment. Especially a plastic with a size of 5 mm or less is defined as micro-plastic and are carried by ocean currents over long distances, causing global pollution. These are not easily decomposed in the natural environment. The Lorentz force was generated in simulated sea water and its reaction force was applied to the micro-plastic to control their motion. Lorentz force was generated downward and the reaction force to the plastics was upward. The plastic used in the experiment was polystyrene with a diameter of 6 mm, and the density was 1.07 g/cm³. The polystyrene sphere levitated at the current density of 0.83 A/cm² and the external field of 0.87T. The particle trajectory calculation was also made to design separation system using superconducting magnet.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.451-454
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• 2008

Potential tsunamis which may occur near Ryukyu Islands were simulated. Propagation characteristics of the potential tsunamis over the southwestern sea and the influence of tsunamis on the southwestern coast of Korean Peninsula were analyzed. The shallow water area in the east sea of China and the deep water Okinawa Trough play an important role in wave transformation and propagation of the potential tsunamis. The propagation characteristics of the potential tsunamis generated near Ryukyu Islands can be described as in followings : In the first stage after generation, the tsunamis propagate with high speed both northeastward and southwestward along the Okinawa Trough. As a result the waves are elongated and the tsunami height is significantly reduced. The elongated crest of tsunamis spans the whole distance of the Okinawa Trough and lines up toward the edge of the continental shelf of East China Sea. Then, the tsunamis are propagating towards the southeast coast of China. Thus, the influence of tsunamis on the Korean coasts becomes weak.