• Ocean Systems Engineering
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• 제12권1호
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• pp.23-38
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• 2022

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

• 한국해안·해양공학회논문집
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• 제26권3호
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• pp.120-130
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• 2014

서해 연안해역과 제주에서 국립해양조사원이 관측한 기왕의 조위자료를 분석하여 평균해수면을 산출하고, 그 변화추세와 원인을 고찰하였다. 서해안에서 그 동안 진행된 대규모 해안개발사업이 평균해수면을 변화시켰다는 것을 확인할 수 있었으며, 그 영향을 추정하였다. 해안개발로 인한 평균해수면 변화는 지역에 따라 큰 차이를 보였으며, 인천항 1단계 개발로 6.8 cm가 하락한 것을 제외하고는 해안개발로 인해서 평균해수면이 대체로 상승하였으며, 금강하구둑 개발로 인해서 인접한 군산내항에서는 평균해수면이 38 cm가 상승하였다. 또한 해안개발로 인한 해수면 변화량을 보정한 평균해수면 자료를 회귀분석하여 해안개발 이외의 요인 즉 자연적 요인으로 인한 해수면 상승률을 추정하였다. 서해안에서 평균해수면은 지구온난화 등의 자연적인 요인으로 인하여 연평균 1.1~4.4 mm/year가 상승하였으며, 지역적으로 편차가 커서 남부해역에서는 크고, 북부해역에서는 작았다. 제주에서는 해수온도의 상승과 평균해수면 상승과 서로 밀접한 관계가 있어서 수온이 $1^{\circ}C$ 상승하면, 평균해수면은 약 6 mm가 상승하였다. 서해안에서 평균해수면은 대체로 1980년대 중반이전에 비해서 1980년대 중반이후에 급격하게 상승하는 경향을 보였다.

• 한국패류학회지
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• 제29권2호
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• pp.97-103
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• 2013

In the present study, we monitored the early development of Saccostrea kegakia subtropical oyster species distributing on rocky intertidal off the northern Jeju Island using scanning electron microscope (SEM). The female oyster collected in early August, 2012 were fully mature exhibiting relatively small eggs ($46.5{\pm}1.4{\mu}m$ in diameter) in the gonad, while testis of the mature male oysters were filled with fully developed sperms of 36.9 ${\mu}m$ in length. The fertilized eggs developed into 2-cell stage with polar body after 1 hr 20 min of fertilization, then followed by Morula stage (3 hr 20 min), Blastula stage (4 hr 50 min), Gastrula stage (7 hr), and trochophore larvae stage (9 hr 30 min). The observed early development of S. kegaki in this study was similar the early development of other oysters, although size of the fertilized eggs were somewhat smaller.

• 수산해양교육연구
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• 제22권2호
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• pp.180-194
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• 2010

Coastal sand dunes are dynamic and fragile buffer zones of sand and vegetation where the following three characteristics can be found: large quantities of sand, persistent wind capable of moving sand, and suitable locations for sand to accumulate. The functional properties of coastal sand dunes include the roles in sand storage, underground freshwater storage, coastal defense, and ecological environment space, among others. Recently, however, the integrity of coastal dune systems has been threatened by development, including sand extraction for the construction industry, military usage, conversion to golf courses, the building of seawalls and breakwaters, and recreational facility development. In this paper, we examined the development mechanisms and structural/format types of coastal sand dunes, as well as their functions and value from the perspective of coastal engineering based on reviews of previous researches and a case study of a small coastal sand dune in the Nakdong river estuary. Existing data indicate that there are a total of 133 coastal sand dunes in South Korea, 43 distributed on the East Sea coast (32 in the Gangwon area, and 11 in Gyeongsangbuk-do), 60 on the West Sea coast (4 in Incheon and Gyeonggi-do, 42 in Ghungcheongnam-do, 9 in Jellabuk-do, and 5 in Jellanam-do), and 30 on the South Sea coast (16 in Jellanam-do, 2 in Gyeongsangnam-do, and 12 in Jeju).

• 전기학회논문지
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• 제61권2호
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• pp.329-334
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• 2012

The distribution submarine cables are normally used for power supply at island, which are mostly installed in the southern coast of KOREA, and partially installed in the west coast and Jeju-Island. There are two way of submarine cable burying system, buried and unburied type. Since 2003, KEPCO is entirely being constructing the distribution submarine cable by buried type. In this case, 'burial depth' is key index for evaluating the suitability of the buried situation. Therefore, the measurement accuracy of 'burial depth' is a big issue for burying system in the distribution submarine cable. This paper demonstrates the measurement error of burial depth that is affected by electrical factor such as grounding type of submarine cable in case of magnetic field detection method, and indicates the method to reduce the measurement error in buried type of distribution submarine cable system.

• ALGAE
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• 제21권4호
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• pp.425-432
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• 2006

Two species of Apoglossum is newly recorded in Korea collected from subtidal habitats of Jeju Island. Apoglossum minimum Yamada has previously been known only from the coast of Japan. It is characterized by having corticated midrib but lacking microscopic veins. Apoglossum gregarium (Dawson) Wynne is reported for the first time from the north western coast of Pacific Ocean. It has been distinguished by its ecorticate midrib from the former species. Their morphological characteristics in detail and taxonomic issues are discussed.

• Fisheries and Aquatic Sciences
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• 제19권9호
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• pp.36.1-36.3
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• 2016

Balssaxius habereri (Balss, 1903) has been newly reported in Korean waters. This species was previously known from the Pacific coast of northern Japan, Korea Strait, Yellow Sea, and Japanese coast of the East Sea. Specimens were collected from western Jeju Island using otter trawls at depths of 65-85 m. Regarding Korean axiid shrimps, a single species, Boasaxius princeps (Boas, 1880), previously known as Axiopsis princeps in Korea, has been recorded. B. habereri is easily distinguished from B. princeps as it does not have tufts of setae on its body and males do not have the first pleopod. Morphological descriptions and color photos of the specimens are provided.

• Journal of Multimedia Information System
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• 제5권4호
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• pp.245-256
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• 2018

This study estimated rainfall information more effectively by image signals through the information system of weather radar. Based on this, we suggest the way to estimate quantitative precipitation utilizing overlapped observation area of radars. We used the overlapped observation range of ground hyetometer observation network and radar observation network which are dense in our country. We chose the southern coast where precipitation entered from seaside is quite frequent and used Sungsan radar installed in Jeju island and Gudoksan radar installed in the southern coast area. We used the rainy season data generated in 2010 as the precipitation data. As a result, we found a reflectivity bias between two radar located in different area and developed the new quantitative precipitation estimation method using the bias. Estimated radar rainfall from this method showed the apt radar rainfall estimate than the other results from conventional method at overall rainfall field.

• 한국환경과학회지
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• 제33권7호
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• pp.533-546
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• 2024

The coastal urchin barren phenomenon in our country began to spread and expand from the 1980s, centering on the southern coast and Jeju Island, and by the 1990s, it appeared along the east coast and nationwide. The urchin barren phenomenon is mainly conducted through field surveys by diving, but recently, various surveying techniques have been applied. In this study, a spectral library for terrestrial and marine areas was established for the identification of urchin barrens using airborne hyperspectral imagery, and the distribution area was analyzed through the SAM (spectral angle mapper) algorithm. An analysis of the urchin barren phenomenon in the five islands of the West Sea revealed that it occurrs in most areas, with the combined severity of the urchin barren phenomenon in Sapsido and Oeyeondo being approximately 19.9%. Hyperspectral imagery is expected to be highly useful not only for detecting the urchin barren phenomenon but also for managing and monitoring marine fishery resources through the classification of seaweeds.

• Ocean and Polar Research
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• 제34권2호
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• pp.151-163
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• 2012

이매패류의 소화맹낭은 고도로 발달된 리소솜 시스템을 지니고 있어 소화작용과 함께 오염물질의 해독과 배출작용을 담당한다. 따라서 소화맹낭의 리소솜 시스템은 환경변화에 민감하게 반응한다고 알려져 있다. 이 연구에서는 동결절편을 이용한 조직학적 방법으로 조간대에 서식하는 참굴 소화맹낭의 리소솜 활동을 측정하였다. 참굴은 2010년 6월 광양만 내만의 초남대교, 차면리와 외만의 신덕리, 평산리 조간대에 서식하는 굴을 채집하였다. 제작된 동결절편을 이용하여 lysosomal membrane stability(LMS) 및 lipofuscin(LF) 축적, neutral lipid(NL) 축적, 소화맹낭 위축도(digestive gland atrophy, DGA)를 평가하였다. 비만도 및 소화맹낭 위축도는 내만에 서식하는 참굴이 다른 지역에 비해 유의적으로 낮았다(P<0.05). LMS는 내만이 외만에 비해 짧은 리소솜 막 불안정화 시간을 보였지만 지역별 통계적인 유의차는 없었다. LF 축적은 내만에 서식하는 참굴이 유의적으로 높은 축적을 보였지만(P<0.05), NL 축적의 경우 외만에 서식하는 참굴이 유의적으로 높은 축적을 보였다(P<0.05). DGA와 LF의 경우 내만과 외만에서 뚜렷한 차이를 보였고, 이는 환경오염의 수준과 관련 있을 것으로 사료된다. 따라서 이 두 가지 분석항목은 연안환경평가에서 좋은 biomarker로 사용될 수 있을 것으로 기대된다.