• 한국해양학회지:바다
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• 제9권3호
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• pp.137-152
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• 2004

한반도 남서해안에서 연안지대의 기후학적 특성을 조사하기 위해 AWS(automatic weather system)와 4개 지점의 부이자료를 사용하였다. 연안지대를 기후학적으로 정의하였는데 해안선을 가로지르는 풍속과 온도의 기울기에 있어서 뚜렷이 대비가 나타나는 지대로 정의하였고, 연안지대가 고정적인 것이 아니라 종관풍에 따라 변동될 수 있다는 것을 보였다. 한반도의 남해와 서해에서 부이와 나란한 AWS지점으로 구성된 4개의 단면도선을 거제도부이라인, 거문도부이라인, 칠발도부이라인, 덕적도부이라인으로 선택하였다. 일주기와 월변동의 분석에서 월별평균과 극값, 부이와 각 지점간의 온도경도와 풍속의 누적빈도수가 연안의 범위와 특징을 조사하는데 응용되었다. 그 결과 연안지대의 최대범위는 거제도부이라인은 offshore에서 생림(해안선에서 약 34 km), 거문도부이라인은 순천(약 52 km), 칠발도부이라인은 자은도(약 27 km), 덕적도부이라인은 용인(약 65 km)으로 분석되었다. 종관풍에 따른 연안지대의 변동을 onshore, offshore, calm에 대해 조사하였다. 그 결과 onshore 일 때 연안지대의 범위는 65∼90 km로 변화한다. 더욱 우리는 태풍(MAEMI)에 의해 영향을 받은 2003년 9월 12일∼13일 동안에 거제도부이라인에 대한 풍속과 온도의 변화와 해상과 육상의 풍속비를 알기 위해 조사하였다.

• 한국전산구조공학회논문집
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• 제35권2호
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• pp.109-117
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• 2022

기존 화석 연료의 고갈 및 환경오염의 문제와 대용량 발전을 위하여 해양환경 및 자원을 이용한 친환경에너지 발전에 대한 연구 및 개발이 증가하고 있으며, 이 중 높은 발전 효율을 가진 해상태양광 발전에 대한 연구가 크게 증가하고 있다. 환경하중이 비교적 약한 내수조건과 달리, 환경하중이 강한 해양에서의 태양광 발전을 위해서는 더 강한 강성의 구조재를 사용해야 한다. 하지만, 구조재의 생산 가능성, 무게를 포함한 구조물 특성 및 경제적 효율성 등의 제약조건이 발생할 수 있다. 따라서, 본 연구에서는 부유식 방파제를 설치함으로써 태양광구조물에 작용하는 파랑하중을 감소시켜 구조재의 강성 강화를 최소화하고자 하였다. 부유식 방파제의 크기 및 구조물로부터의 거리를 변화하여 이에 따른 파랑하중 및 구조재 응력의 감소 정도를 확인하였다. 다수 부력체의 상호간섭을 고려한 파랑하중의 경우, 고차경계요소법(Higher-Order Boundary Element Emthod)을 이용해 산정하였으며, 구조재에 작용하는 응력은 유한요소법(Finite Element Method)을 통해 평가하였다. 각 조건에서의 최대응력을 분석 및 비교함으로써 해상태양광 발전 시스템에 대한 부유식 방파제의 영향을 확인하였으며, 부유식 방파제의 크기가 파랑하중 및 구조재 응력 감소에 큰 영향을 미침을 확인하였다.

• ALGAE
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• 제30권2호
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• pp.89-101
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• 2015

Ecklonia cava Kjellman is a common kelp found in shallow subtidal in warm-temperate waters in the northwest Pacific Ocean. This species has shown substantial morphological variation along with subsistence in different locations and local environments. We quantified the magnitude of morphological variation of E. cava from six populations along ~700 km of coastline from Jeju Island to Dokdo in Korea. In addition, we examined genetic distance among the populations using random amplified polymorphic DNA (RAPD) analysis. Most morphological characteristics investigated were significantly different among locations. Multivariate analyses indicated two phenetically distinct groups (nearshore, sheltered vs. offshore, exposed), indicating wave exposure with turbidity are presumably major factors for the separation. With RAPD data, results of Nei's diversity (H) and AMOVA showed considerable variations in within- and between-populations. Pairwise ${\Phi}_{ST}$ and $N_m$ values indicated moderate gene flow between the six locations. Results of Nei's analysis revealed three genetically distinct groups, not consistent with the morphological groupings, indicating that a time gap may exist between morphological and genetic variations. This study also suggests dispersal distance of this kelp may be longer than what is commonly thought and genetic similarity in the populations was largely reflected by the direction of ocean current rather than just geographical distance.

• 한국초전도ㆍ저온공학회논문지
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• 제25권2호
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• pp.19-24
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• 2023

Recently, interest in renewable energy such as solar and wind power has increased as an alternative to fossil fuels. Renewable energy sources such as large wind farms require long-distance power transmission because they are located inland or offshore, far from the city where power is required. High-Temperature Superconducting (HTS) power cables have more than 5 times the transmission capacity and less than one-tenth the transmission loss compared to the existing cables of the same size, enabling large-capacity transmission at low voltage. For commercialization of HTS power cables, unmanned operation and long-distance cooling technology of several kilometers is essential, and pressure drop characteristic is important. The cryostat's spiral corrugation tube is easier to bend, but unlike the round tube, the pressure drop cannot be calculated using the Moody chart. In addition, it is more difficult to predict the pressure drop characteristics due to the irregular surface roughness of the binder wound around the cable core. In this paper, a CFD model of a spiral corrugation tube with a core was designed by referring to the water experiments from previous studies. In the four cases geometry, when the surface roughness of the core was 10mm, most errors were 15% and the maximum errors were 23%. These results will be used as a reference for the design of long-distance HTS power cables.

• 대한원격탐사학회지
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• 제28권1호
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• pp.95-100
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• 2012

큰 너울은 먼 해역에서 발생한 후 우리나라 해안에 전파하여 피해를 입히는 경우가 많다. 이를 방지하기 위해서는 우리나라 인근 해역에서 뿐만 아니라 외해역에서도 파랑 관측이 이루어져야 하지만 현장 관측의 경우 많은 비용 및 장비 망실 위험 때문에 어려움이 따른다. 위성의 고도계를 활용할 경우 우리나라 동해 중앙 해역이나 외해 그리고 타 국가의 해역과 같이 접근이 어려운 해양에서 파랑을 관측하는 일이 가능하다. 그러나 이에 앞서서 고도계 파랑 자료의 정확도를 검증하는 것이 필요하다. 본 연구에서는 ENVISAT 위성의 고도계 파고 자료와 이어도 기지에서 관측한 파랑 자료를 비교 분석 한 후 그 활용성을 검토한다.

• ALGAE
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• 제26권1호
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• pp.41-50
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• 2011

Yellow Sea surface sediment samples collected on October 15-31, 2003 were analyzed using the palynological process to investigate the spatial distribution of dinoflagellate resting cysts. The sampling areas comprised four latitudinal transects, the northernmost of which was located off the Shandong Peninsula, China and the southernmost off Jeju Island, Korea. Each transect line was composed of six to nine stations, spanning the distance between the Chinese and Korean coasts. Twenty-five different types of dinoflagellate cysts were identified. Gonyaulax scrippsae, Alexandrium spp. (ellipsoidal type), and G. spinifera were the most dominant at all stations surveyed. Dinoflagellate cysts belonging to the Gonyaulacales comprised over 50% of all cysts collected. The latitudinal distribution trend showed that cyst concentrations along the two middle transects were much higher than those along the two northern and southern transects. Cyst concentrations in the offshore central areas reached their highest values within each transect and gradually decreased toward the Chinese and Korean coasts. Overall, cyst concentrations were markedly elevated in the offshore central Yellow Sea areas and gradually decreased outward in all four directions. This concentric cyst distribution pattern was consistent with the hydrographic features of the Yellow Sea, such as circular current systems, sedimentary properties, and water depth.

• 대한안전경영과학회지
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• 제11권2호
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• pp.95-101
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• 2009

The present study is to estimate the effect of wave height affecting at the front face of breakwater systems due to specification of submarine trench such as distance from breakwater to dredged area and width of dredge. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine dredge on the sea bed designated by single horizontal long-rectangular pit system according to the various specific conditions of dredged locations. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height at the front face of breakwater was varied by dependance of distant from breakwater to dredged area and width of dredge. It means that, when the navigation channel or pit breakwater is dredged on seabed, engineers have to consider the specification of dredge. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field and provided for safety construction of offshore structure.

• 대한조선학회논문집
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• 제55권5호
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• pp.415-420
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• 2018

The development of sail gas has increased the production of ethane as well as natural gas. The decline in the market price for ethane has led to a change in the petroleum-based ethylene production process into an ethane-based ethylene production process and an increase in the ethane/ethylene trade volume. Large-scale ethane/ethylene carrier have been needed due to an increase in long-distance trade from the US, and cargo type change have leaded to consider a liquefaction process to re-liquefy Boil-Off gas generated during the voyage. In this paper, the liquefaction system of Liquefied Ethane Gas carrier was evaluated with Low-GWP (Low-Global Warming Potential) refrigerant and process parameters, Boil-Off Gas pressure and expansion valve outlet pressure, were optimized. Low-GWP refrigerants were propane (R290), propylene(R1270), carbon dioxide(R744) was considered at two type of liquefaction process such as Linde and cascade cycle. The results show that the optimal pressure point depends on the individual refrigerant and the highest liquefaction efficiency of carbon dioxide (R744) - propane (R290) refrigerant.

• Geomechanics and Engineering
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• 제28권6호
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• pp.585-598
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• 2022

The monopile-friction wheel hybrid foundation is an innovative solution for offshore structures which are mainly subjected to large lateral eccentric load induced by winds, waves, and currents during their service life. This paper presents an extensive numerical analysis to investigate the lateral load and moment bearing performances of hybrid foundation, considering various potential influencing factors in sand-overlaying-clay soil deposits, with the complex lateral loads being simplified into a resultant lateral load acting at a certain height above the mudline. Finite element models are generated and validated against experimental data where very good agreements are obtained. The failure mechanisms of hybrid foundations under lateral loading are illustrated to demonstrate the effect of the friction wheel in the hybrid system. Parametric study shows that the load bearing performances of the hybrid foundation is significantly dependent of wheel diameter, pile embedment depth, internal friction angle of sand, loading eccentricity (distance from the load application point to the ground level), and the thickness of upper sandy layer. Simplified empirical formulae is proposed based on the numerical results to predict the corresponding lateral load and moment bearing capacities of the hybrid foundation for design application.

• 풍력에너지저널
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• 제10권4호
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• pp.20-27
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• 2019

High-speed shaft coupling in a wind power system transmits power and absorbs variations in length and spindle dislocation between the gearbox and generator. Furthermore, the coupling has an insulation function that prevents electrical corrosion caused by the flow of the generator's current into the gearbox and prevents overload resulting from sudden power failure from being transferred to the gearbox. Its design, functions, and part verification are described in the IEC61400 and GL Guidelines, which specify that the part must have a durability life of 20 years or longer under distance variation and axial misalignment between the gearbox and the generator. This study presents the design of a high-speed coupling through composite stiffness calculation, structural analysis, and comparative analysis of test and theory to identify the characteristics of high-speed coupling for a large-capacity 6 MW wind power generator. A prototype was fabricated by optimizing the manufacturing process for each part based on the design, and the reliability of the fabricated prototype was verified by evaluating the performance of the target quantitative evaluation items.