• 수산해양기술연구
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• 제34권2호
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• pp.117-134
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• 1998

The study on the Assembling Mechanism of the Hairtail, Trichiurus lenpturus, at the Fishing Grounds of the Cheju Strait had been investigated by analyzing the relationship of the oceanographic conditions and the fishing ground of the Hairtail in the Cheju Strait. 1. The fishing grounds of the hairtail at the Cheju Strait are formed at the bottom of a high temperature of the tidal front at the coast. area of northern Cheju Island, the tip of the linguiform is high in salinity at the eastern and western entrances of Cheju Island, low salinity eddy on the surface and its surrounding front, various water masses in the Strait and coastal waters of the South Sea in Korea. 2. The fishing grounds of the Hairtail at the Cheju Strait begins with the sea surface temperature higher than $15^{\circ}C$ and the incoming of low salinity water now from the East China Sea. 3. Estimation of optimum temperature and salinity per season based upon analysis for relationship between temperature of water and salinity of the bottom layer and the catch is : 15.2~$16.4^{\circ}C$, 34.20~34.40${\textperthousand}$ in spring(June); 14.4~ $17.0^{\circ}C$, 33.70~34.30${\textperthousand}$ in summer(July~September); and 15.7~ $18.6^{\circ}C$, 33.70~34.50$\textperthousand$ in autumn(October~December). Hairtail are mostly caught at the Yellow Sea Warm Current and Tsushima Current with temperature over $14.5^{\circ}C$ and salinity over 33.70${\textperthousand}$ at the bottom layers of the Cheju Strait. 4. Considering the relationship between the amount of hairtail catch and the water temperature of bottom layer, when the bottom water being above $14.0^{\circ}C$ flowed into Cheju Strait through the western entrance of the strait in summer, the ca-h appears to have been abundant. In contrast, the catch has been poor when the temperature of such water was recorded to be below $13^{\circ}C$ Therefore, distribution patterns of water at the bottom layer can be used as a forecast index whether the catch of a certain year will be good or poor.

• Geomechanics and Engineering
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• 제12권3호
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• pp.523-539
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• 2017

Clay soils are typical for their swelling properties upon absorption of water during rains and development of cracks during summer time owing to the profile desorption of water through the inter-connected soil pores by water vapour diffusion leading to evaporation. This type of unstable soil phenomenon by and large poses a serious threat to the strength and stability of structures when rest on such type of soils. Even as lime and cement are extensively used for stabilization of clay soils it has become imperative to find relatively cheaper alternative materials to bring out the desired properties within the clay soil domain. In the present era of catastrophic environmental degradation as a side effect to modernized manufacturing processes, industrialization and urbanization the creative idea would be treating the waste products in a beneficial way for reuse and recycling. Bottom ash and ecosand are construed as a waste product from cement industry. An optimal combination of bottom ash-eco sand can be thought of as a viable alternative to stabilize the clay soils by means of an effective dispersion dynamics associated with the inter connected network of pore spaces. A CATIA model was created and imported to ANSYS Fluent to study the dispersion dynamics. Ion migration from the bottom ash-ecosand pile was facilitated through natural formation of cracks in clay soil subjected to atmospheric conditions. Treated samples collected at different curing days from inner and outer zones at different depths were tested for, plasticity index, Unconfined Compressive Strength (UCS), free swell index, water content, Cation Exchange Capacity (CEC), pH and ion concentration to show the effectiveness of the method in improving the clay soil.

• The Journal of the Acoustical Society of Korea
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• 제13권2E호
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• pp.76-82
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• 1994

천해 해저 퇴적물의 특성은 수 미터 깊이에서도 변할 수 있다. 퇴적층에서의 음속 뿐만 아니라 감쇠계수도 퇴적물의 성분과 특성 자체에 의해서 결정되므로 감쇠계수는 퇴적층 깊이에 따라 가변적이라고 여기는 것이 합리적이다. 본 연구에서는 포물선 방정식 기법을 도입한 음향모델을 이용하여 퇴적층 종파 감쇠계수의 변화가 100-805 Hz 대역 음파의 전파에 미치는 영향을 고찰하였다. 대상 해역은 해저면이 사질로 구성되어 있고, 수심과 최적층의 깊이는 각각 40 m, 10m이다. 감쇠계수가 퇴적층 깊이에 따라 일정하게 또는 가변적으로 가정함에 따라 음파의 전파손실은 15 km 거리에서 10dB 까지 차이가 발생한다. 모델에 의하여 계산된 전파손실은 감쇠계수를 퇴적층 깊이에 따라 변하게 할 경우 실측된 전파손실과 잘 일치한다.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1370-1377
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• 2005

The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change of the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural integrity of the material capsule called 04M-17U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19.6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's in-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.

• 한국지반환경공학회 논문집
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• 제11권6호
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• pp.77-83
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• 2010

본 연구에서는 화력발전소에서 발생한 바텀애쉬를 성토재로 사용하기 전 환경에 미치는 영향을 평가하고자 하였다. 바텀애쉬에 대한 기본 물성치는 공업분석, 원소분석, XRD, XRF를 통해 구하였고, 폐기물 용출실험, 토양오염 공정실험을 통해 바텀애쉬에 대한 폐기물 분류 및 토양오염 가능성을 평가하였다. 위 용출실험 결과는 국내 수질환경기준 및 지하수 수질기준과 비교하였고 수질오염의 가능성은 없는 것으로 평가되었다. 측정된 대부분의 중금속은 검출한도 이하였으며 $Cr^{6+}$의 경우 미량이 검출되었으나 기준치 이하였다. 컬럼실험에서는 Pb, Zn 및 황산염이 기준치를 초과하였으나, Pb과 Zn은 1 PVE 전에 모두 기준치 이하로 감소하였고 황산염은 기준치 이하로 감소하는데 최대 8 PVE의 시간이 소요되었다. 중금속의 경우 대부분이 기준치 이하이므로 문제가 없으나 황산염은 기준치를 10배 정도 초과하므로 사용에 주의를 요한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.782-787
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• 2005

The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change or the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural Integrity of the material capsule called 04M-l7U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19 6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's In-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.

• 한국환경복원기술학회지
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• 제11권6호
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• pp.120-129
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• 2008

Removal rate of $NO_3-N$ and TN in a free water surface wetland system with litter layer on its bottom was compared with that without one. The system was established on floodplain in the down reach of the Gwangju Stream in 2001. Its dimensions were 31 meters in length and 12 meters in width. Water of the stream was funneled into it and its effluent was discharged back into the channel. Average litter layer of 9.6 cm was formed on its bottom in 2007. The layer and above-ground parts of reeds and cattails on the system were eliminated in Spring 2008. Volumes and water quality of inflow and outflow of the system were analyzed from May to November in 2007 and 2008, respectively. Inflow into the system both in 2007 and 2008 averaged approximately $40m^3/day$ and hydraulic residence time both in 2007 and 2008 was about 1.5 days. Average influent $NO_3-N$ concentration in 2007 and 2008 was 2.16 and 2.05 mg/L, respectively and influent TN concentration in 2007 and 2008 averaged 3.98 and 3.89 mg/L, respectively. With a 0.05 significance level, effluent temperatures, influent concentrations of $NO_3-N$ and TN, and stem numbers per square meter and height of the emergent plants showed no difference between the system with litter layer and without one. $NO_3-N$ removal in the system with litter layer and without it averaged 55.59 and 46.06%, respectively and TN retention averaged 57.24 and 48.97%, respectively. Both $NO_3-N$ and TN abatement rates in the system with litter layer were significantly high (p < 0.001) when compared with those without one. The wetland system having litter layer on its bottom was more efficient for $NO_3-N$ and TN retention than that without one.

• 수산해양기술연구
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• 제41권3호
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• pp.179-187
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• 2005

This study was conducted in order to the experiment of bottom trawl fisheries in the sea mount of central northern pacific($30^{\circ}-40^{\circ}N$, $170^{\circ}-175^{\circ}E$), during the period of July 1 to August 25, 2004 by commercial trawl ship. Fishing experiment was carried out by bottom trawl, with the codend of 110mm mesh size. The number of 101 test fishing was done in the sea mount of central northern pacific during 56 days and the total catches were 198,593kg as 18 fish species, and CPUE/day and catches/day were 8.3 hours towing time and 3,546kg. Catch ratio according to each fishing ground was higher with the order of B, C, and E, and catches for B was 7,171.0kg during the towing time of 13.2 hours. Main target species were Pseudopentaceros richardsoni and Beryx splendens, there was 14.9% of damage ratio for fishing gears on catching the target fishes inhabiting on the rough sea bottom. Catches by water depth was the order of 300m below, 301-350m, 451-500m and 351-400m. It is thought that there was no problem on the mesh size because most of fishes caught from the experimental fishing was 30cm over.

• 해양환경안전학회지
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• 제29권6호
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• pp.562-575
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• 2023

새만금 호의 수질 개선을 위하여 국가에서 해수 유통을 증가시킴에 따라 해수 유통 빈도 증가로 인한 새만금 호 내 염분과 저층수 교환 변화를 알아보기 위하여, EFDC(Environmental Fluid Dynamics Code) 모델을 이용하였다. 갑문 개폐 횟수를 하루 1회에서 2회로 증가했을 때, 새만금 호 내부 수위는 최대 약 0.7 m 상승하였다. 염분은 서측 방조제 근방에서 2.12 psu 증가하였으며, 담수 유입 부근에서는 1.18 psu 감소하였다. 입자추적을 이용하여 저층수 교환 정도 분석한 결과, 수심 5m 이하 입자 잔류율은 Case 2(1일 2회 개방)에서 Case 1(1일 1회 개방)에 비해 2.52% 감소한 것으로 나타났다. 이는 수문 개폐 횟수를 증가시켰을 때, 저층수 교환이 더 활발해 질 수 있다는 것을 알 수 있다. 따라서 해수 유통 증가에 따른 염분 및 저층수 교환 증가로 새만금 호의 수질 개선이 될 수 있다고 판단된다.

• Ocean Systems Engineering
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• 제4권4호
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• pp.263-278
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• 2014

The spudcan requires the suitable design considering the soil, platform, and environmental conditions. Its shape needs to be designed to secure sufficient reaction of soil so that it can prevent overturning accidents. Its shape also has to minimize the installation and extraction time. Even in the same soil condition, the reaction of soil may be different depending on the shape of spud can, mainly the slope of top and bottom plates. Therefore, in this study, the relation between the slope of plates and the reaction of soil with and without water jetting is analyzed to better understand their interactions and correlations. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the Gulf of Mexico is considered as the target site. A multi layered (sand overlying two clays) soil profile is applied as the assumed soil condition and the soil-structure interaction (SSI) analysis is performed by using ANSYS to analyze the effect of the slope change of the bottom plate and water jetting on the reaction of soil. This kind of investigation and simulation is needed to develop optimal and smart spudcan with water-jetting control in the future.