• 한국해양환경ㆍ에너지학회지
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• 제15권2호
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• pp.101-110
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• 2012

가막만 두 개의 만구에서의 수온·염분변화 및 해수교환특성을 이해하기 위하여, 하계 및 동계에 수온 염분 및 흐름을 15일간 동시 관측하였다. 현장조사결과, 흐름은 바람과 비교적 밀접한 상관관계를 가지고 있었고, 또한, 상관분석결과 수온은 조석보다는 기온의 영향을 더 크게 받고 있는 것으로 나타났다. 특히, 수온은 남쪽만구의 얕은 수심으로 인하여, 동쪽만구보다 계절에 따라 더 민감한 반응을 보였다. 염분의 농도변화에 기초한 해수교환율은 하계에 동쪽만구에서 0.5~29.9%(평균 11.6%), 남쪽만구에서 1.3~62.6%(평균 18.6%)로 각각 나타났다. 반면, 동계의 해수 교환율은 동쪽만구에서 0.3~28.5%(평균 8.9%), 남쪽만구에서 0.1~97.9%(평균 31.2%)로 각각 나타났다. 따라서, 가막만의 해수교환율은 남쪽만구가 동쪽만구에 비해 약 3배정도 더 높았고, 하계에는 동쪽만구, 그리고 동계에는 남쪽 만구의 해수교환율이 각각 타 계절에 비해 증가하는 것으로 나타났다. 이 결과는 계절에 따른 풍향변화가 가막만의 해수교환율에 영향을 미치고 있음을 반증하였다.

• Corrosion Science and Technology
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• 제11권6호
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• pp.263-269
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• 2012

Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.

• 동력기계공학회지
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• 제18권1호
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• pp.63-68
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• 2014

The numerical analysis of fluid flow in the tube cleaning system is examined. The working flow used in this study is seawater, and the temperature change is not considered as the temperature change of seawater in the tube cleaning system is negligible. Also, the analysis is performed under the assumption of steady state. The screens of complicated morphologies are simplified for the analysis, and only one fourth of the tube cleaning system is modeled as the system has a symmetrical shape. The velocity inlet boundary condition is employed for the seawater inlet, whereas the outflow boundary condition is employed for two seawater outlets. In applying the outflow boundary condition for the system with more than two outlets, the flow rate can be arbitrarily assigned. In the analysis, the finite-volume method based numerical analysis tool, the pressure based solver, the standard k-$\varepsilon$ model are utilized, and the under relaxation factor is modified appropriately. From the analysis, the distribution of velocity vectors, pressure and path lines are obtained, and the physical characteristics of fluid flow in the tube cleaning system is well-examined.

• 동력기계공학회지
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• 제21권2호
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• pp.77-82
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• 2017

In the fishing boat, freshwater ice is loaded on the fishroom in advance and it is used for storage of fishes. However, it causes degradation of catches' freshness. Therefore, seawater ice machine on board is necessary for the fishing industry. In this study, seawater ice machine with drum type evaporator was manufactured, and the system was tested under various operating conditions having an influence on the COP and amount of ice produced. The main results are as follow : The COP of the system gets larger when the evaporation temperature and rotation speed of the drum in the evaporator increases. The most effective refrigerant is R22 and the value of the COP was 1.43 times higher than that of R404A. The amount of produced ice increases with respect to increment of the evaporation temperature, while that decreases with respect to increment of the evaporator drum rotation speed.

• 한국안전학회지
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• 제38권3호
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• pp.20-26
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• 2023

Fiber-reinforced composite materials with carbon, glass, and aramid fibers are widely applied to industrial field structures due to their excellent properties. However, carbon fibers are vulnerable to external impacts, whereas aramid fibers degrade when exposed to water. This study evaluated carbon/aramid fiber composites degraded and damaged by high-temperature saline environments using acoustic emission (AE). The test specimen was molded using an autoclave and immersed in seawater at 70 ℃ for 224 days. In order to imitate the damage, a 3-mm-diameter hole was drilled using a diamond drill. Additionally, the specimen with the perforation was repaired by patch attachment processing. Three-point bending was used to conduct the flexural experiment, and an AE sensor with a 150-kHz resonance frequency was attached to evaluate the damage and the effect of patch attachment. AE accumulative counts obtained at the maximum load were 69.2, 67.1, and 91.2 for a high-temperature seawater deteriorated condition, a hole specimen, and a repaired patch specimen, respectively. Furthermore, the maximum amplitude of AE was detected at low values of 28 dB, 31.3 dB, and 30.3 dB.

• 한국환경과학회지
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• 제8권2호
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• pp.161-164
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• 1999

This study was done to research the effects of temperature on biological evaluation of seawater quality using gametes, embryos and early development system of seaurchin species, Hemicentrotus pulcherrimus, Anthocidaris crassispina and Scaphechinus brevis. As the result of performing effects of temperature on early embryo development, the conditions of appropriate temperature on formation of normal pluteus were appropriate at 5-16$^{\circ}C$ for H. pulcherrimus, 8-2$0^{\circ}C$ for A. crassispina, 12-2$0^{\circ}C$ for S. brevis. The conditions of optimum temperature on biological evaluation were 16$^{\circ}C$ for H. pulcherrimus and 2$0^{\circ}C$ for A. crassispina and S. brevis.

• 한국해양학회지
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• 제25권1호
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• pp.1-7
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• 1990

동해 서남해역의 상부 125미터 수층을 대상으로 1981년 9월부터 1984년 10월에 걸 쳐 6회의 현장조사를 실시하여 841개의 해수시료를 구하였고, 이들의 수온, 염분, 무 기영향염류 및 식물플랑크톤 종별 현존량에 대하여 연구하였다. 도합 235종류의 식물플랑크톤을 동정하였으며, 이 가운데 Cylindrothecqa closterium 과 Nitzschia delicatissuma 등의 두 종이 최고의 공통종인 동시에 우점종으로 나타났다. 연구해역 상부혼합 층 시료 중의 식물플랑크톤 현존량과 수온, 염분 및 무기영양염류 등의 환경 요인과의 관계를 다중회귀 분석한 결과 봄에는 수온의 회귀상수가 염분에 비해 1.6-4.2배 컸으며, 반대로 가을에는 염분의 회귀상수가 수온에 비해 2.1-3.4배 크게 나타났다. T-S diagram 위에서 식물플랑크톤 현존량 분포가 봄에는 수온 변화에 민감 하였으며 가을에는 염분 변화에 민감하였고, 도식적으로 T-S diagram 상에 표시한 높 은 현존량 구역은 계절적으로 순환하는 양상을 나타내었다. 이는 연구해역의 식물플랑 크톤 현존량 분포가 여타가 여타의 환경요인보다 특별히 해양물리학적 특성과 긴밀한 관계가 있음을 의미한다.

• Fisheries and Aquatic Sciences
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• 제21권1호
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• pp.1.1-1.12
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• 2018

Pacific bluefin tuna (Thunnus orientalis) is one of the commercially important species in Korea as well as other countries of the North Pacific. Korean offshore large purse seine fisheries targeting small pelagic fishes such as chub mackerel have caught T. orientalis temporarily in the east of Jeju Island. The catch of T. orientalis in March through June occupied approximately 60% of the total. The monthly catch around Jeju Island from 2004 to 2013 showed a negative correlation (r = - 0.755, p < 0.01) with the seawater temperature at 50 m and had a significant positive correlation (r = 0.856, p < 0.01) with the Pacific Decadal Oscillation Index (PDOI). The highest catch and catch per unit effort (CPUE) of T. orientalis around Jeju Island occurred either when the seawater temperature ranged between 15 and $16^{\circ}C$ at 50 m or when the catch was taken near the frontal area where two water masses from offshore and coastal areas collide. The length of T. orientalis caught around Jeju Island from 2004 to 2013 ranged from 19 to 193 cm in fork length (FL). The time series of the monthly mean FL of T. orientalis had a negative correlation (r = - 0.592, p < 0.01) with the seawater temperature at 50 m and had a significant positive correlation (r = 0.668, p < 0.05) with PDOI.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.329-332
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• 2003

Aquaculture have been important role to supply food resources for mankind. However, competitive power of domestic mariculture industry was declined due to increase of labor and feed expenditures, and quantity import of low-priced livefishes from the developing underdeveloped nations in North and South East Asia. Mass production and quality enhancement can be pointed out to overcome such an industrial environment in this decade. To meet these requirement, movable mariculture base remodeling feasible vessel of chemical tanker or crude oil carrier has been proposed for more advanced mariculture management system by using deep seawater from about 200m which is sustainablely clean, nutrient-rich and cold seawater. Deep seawater can be applied for control of seawater temperature for mariculture base and cultivation phytoplankton and seaweed as feed. Besides mariculture, strategic marketing can be implemented by raw water and ice of deep seawater. Feasibility of applying deep seawater was considered after evaluating general movable mariculture base and management system.

• 한국환경보건학회지
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• 제33권4호
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• pp.325-337
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• 2007

The effect of seawater and air pollutants on the three-story stone pagodas on Gameunsa Temple Site have been studied in order to establish conservation basic plan. Also, an experimental study has been conducted to evaluate the effect of seawater salt and air pollutants on the weathering of granite. The results could be summarized as follows. Because the three-story stone pagodas on Gameunsa Temple Site are located outdoors, the external appearance has been largely deteriorated due to natural and artificial factors such as typhoon, wind, microorganisms, moisture, extreme change in temperature, air pollutants, and seawater, etc. When G.J fresh granite was dipped into the seawater, dissolution rate of three minerals (Mg, Ca, and K) are increased linearly until about 40 days and then increased abruptly. After seawater dipping experiments, the mineral compositions of the granite surface were lower then that of the G.J fresh granite but Poisson's ratio and absorption ratio were slightly increased. Therefore, from these results we can say that stone cultural properties could be weathered by seawater and air pollutants and it's considered being a meaningful experiment to study the conservation method of stone cultural properties from seawater.