• 지구물리와물리탐사
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• 제25권1호
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• pp.1-13
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• 2022

포항분지 천부가스 탐사를 위해 육상과 해상이 연결되는 전이대에서 탄성파 탐사 방법을 제안하고 탐사를 수행하였다. 해저면 환경, 육상 탐사 환경을 고려하여 탐사를 설계하였다. 육상노드 수진기는 육상에만 설치하였고 육상에서는 바이브로사이스 음원을, 해양에서는 에어건 음원을 이용하여 자료를 취득하였다. 전이대에서 취득한 탄성파 탐사자료의 경우 육상탐사와 해상탐사 간의 정확한 연계를 위해 신중한 자료 취득과 처리 과정이 필요하다. 음원 종류에 따른 진폭과 위상변화를 고려하고, 음원위치에 따른 정적보정을 적용한 자료처리를 통해 지층단면도에서 반사파 연속성이 유지되게 하였다. 자료처리 결과 육상과 해상의 지층구조가 연결된 탄성파 지층단면도를 확보하고 포항분지 천부 가스층 탐사에 활용하고자 하였다. 전이대에서 탄성파 탐사는 천부가스뿐만 아니라 연안지역 단층대 조사에도 활용할 수 있을 것으로 기대된다.

• 한국지형학회지
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• 제24권3호
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• pp.1-11
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• 2017

The pollen analysis on the deposits of the lower marine terrace I of the estimated paleoshoreline height of 18m was performed in order to estimate the formation age of this terrace developed at the Sanha-dong coast, Ulsan, southeastern coast of the Korean peninsula. The pollen assemblage of the peat layer of SH-1 pollen zone (Quercus-Ulmus/Zelkova zone), lying directly on the marine rounded pebble layer of this terrace, shows that the climatic environment of the deposition period of SH-1 pollen zone was almost similar to that of the Postglacial climatic optimum period, but slightly cooler than that of the late warm stage of Last Interglacial(MIS 5a) in the eastern coast of Korea. This heightens the possibility that the deposition period of the marine rounded pebble layer which was covered by the above SH-1 peat layer is the MIS 5e which has been estimated by a previous study of the sedimentary facies of this terrace deposits (Choi, 2016). The pollen assemblage of SH-2 pollen zone (Pinus-Quercus zone) shows that the climate of this period was almost similar to that of the late Postglacial, but slightly cooler than that of the period of SH-1 pollen zone. This means that the climate around the Sanha-dong was still warmer in the deposition period of the peat layer of SH-2 pollen zone. Thus, the peat layer of SH-2 pollen zone was considered to have been deposited during the period from the early regression stage of the MIS 5d which is the estimated final stage in the deposition period of the above peat layer of SH-1 pollen zone to any stage in which the warmer environment of MIS 5 has still lasted. The humic silt layer of SH-3 pollen zone (Pinus-Ulmus/Zelkova-Abies zone) is assumed to have been deposited during the interstadial of the Last Glacial (MIS 3).

• Journal of Species Research
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• 제12권2호
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• pp.180-188
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• 2023

The region of the marine environment between shallow waters and deep-sea (30-150 m in depth) is referred to as the twilight or mesophotic zone. This zone has been scarcely examined, as these depths are too shallow for safe submersible operation. Since 2018, a survey of mesophotic echinoderms in Korea has yielded many specimens of interest. In this study, we present two newly recorded echinoderms, Henricia irregularis and Parastichopus nigripunctatus based on morphological redescriptions with high-definition photographs and DNA barcoding data for P. nigripunctatus.

• Corrosion Science and Technology
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• 제7권2호
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• pp.134-137
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• 2008

Cold arc welding of cast iron has been widely used with repair welding of metal structures. However its welding is often resulted in the galvanic corrosion between weld metal zone and heat affected zone(HAZ) due to increasing of hardness. In this study, corrosion properties such as hardness, corrosion potential, surface microstructures, and variation of corrosion current density of welding zone with parameters of used electrodes for cast iron welding were investigated with an electrochemical evaluation. Hardness of HAZ showed the highest value compared to other welding zone regardless of kinds of used electrodes for cast iron welding. And its corrosion potential was also shifted to more negative direction than other welding zone. In addition, corrosion current density of WM in polarization curves was qualitatively smaller than that of HAZ. Therefore galvanic corrosion may be apparently observed at HAZ. However galvanic corrosion may be somewhat controlled by using an optimum welding electrode.

• 한국해양환경ㆍ에너지학회지
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• 제13권4호
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• pp.305-312
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• 2010

잘피밭은 많은 생태계서비스를 제공하는 경제적 가치가 매우 높은 연안습지의 한 종류다. 중국에서도 북부연안을 따라 넓은 잘피밭이 분포하나 오랫동안 중요성이 간과되어 왔고 연구도 부족한 실정이다. 본 논문은 최초로 중국 북부연안 잘피의 종류와 분포를 제시하였으며, 과거로부터 현재까지의 변동양상을 기술하여 역사적인 감소추세를 분포와 생물량의 관점에서 기술하였다. 대표적인 잘피밭의 현황을 나타내기 위해 추다오 지역을 선정하여 사례를 제시하였다. 환경조건이 좋은 곳에서는 잘피도 회복되고 있으며, 잘피밭에 의존하는 플랑크톤과 어류, 돌고래 등 해양포유류도 풍부하였다. 역사적인 감소추세와 현상황에 대한 원인이 토의되었으며 보호를 위하여 필요한 연구내용을 제시하였다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.331-338
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• 2005

The grain structure, dislocation density and second phase particles in various regions including the stir zone(SZ), thermo-mechanically affected zone(TMAZ), and heat affected zone(HAZ) of a friction stir weld 6.35mm thick aluminum 7075-T651 alloy were investigated and compared with the base metal. The microstruectures of nugget zone were compared according to tool rotation speeds and tool transition speeds. The hardness profiles of nugget zone were increased, while decreasing rotation speed and increasing welding speed. The optimal microstructure was gained at the low rotation speed 800rpm and th high welding speed 124mm/min. The nugget microstructures of fracture surface, transgranular dimple and quasicleavage type were showed different fracture type with the HAZ, shear fracture type.

• 한국환경과학회지
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• 제31권12호
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• pp.1027-1038
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• 2022

The intertidal zone has both land and marine characteristics and shows complex weather environments. These characteristics are suited for studying climate change, energy balance and ecosystems, and may play an important role in coastal and marine weather prediction and analysis. This study was conducted at Odo Island, approximately 300m from the mainland in Yeosu. We built a weather observation system capable of real-time monitoring on the mud flat in the intertidal zone and measured actual weather and marine data. Weather observation was conducted from April to June 2022. The results showed changes in air temperature and water temperature with changes in the tide level during spring. Correlation analysis revealed characteristic changes in air temperature and water temperature during the day and night, and with inundation and exposure.

• Ocean and Polar Research
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• 제40권2호
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• pp.69-75
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• 2018

We investigated the effects of environmental variations on the growth and survival rate of Stichopus japonicus to determine the optimum environmental conditions for its growth. Literature studies and a 12 month-long diver survey were carried out to understand the habitat, ecology and size of the surveyed area. Based on the collected data, we suggested optimum habitat conditions for releasing S. japonicus. Experiments on releasing S. japonicus were conducted in the breakwater of the Hwagye fishing cooperative in Hwagey-ri, Namhae-un, Gyeongsangnam-do, Korea. To implement the experiments, we divided the surveyed area into 4 sub-areas with different characteristics: (1) sand and silt zone; (2) artificial sea cucumber bank zone; (3) artificial rock bank zone; and (4) marine algae zone. The experiment lasted for 12 months. We released 32,000 sea cucumbers over $120m^2$ of each of the sand and silt zone, artificial rock bank zone and marine algae zone and released 6,000 sea cucumbers over $120m^2$ of the artificial sea cucumber bank zone. The average density of the released sea cucumbers from day 30 to day 360 after the releasing was conducted was the highest in the artificial sea cucumber bank zone ($23.7animal/m^2$), which was followed by artificial rock bank zone ($2.0animal/m^2$), marine algae zone ($1.9animal/m^2$) and sand and silt zone ($0.8animal/m^2$). The analysis on growth showed that the initial average weight of 2.3 g increased on day 360 after the releasing to 12.5 g in the artificial sea cucumber rank zone, 20.2 g in the sand and silt zone, 23.3 g in the artificial rock bank zone and 22.9 g in the marine algae zone. Results from the experiment along with the literature analysis suggest the following optimum habitat conditions: $10-15^{\circ}C$ water temperature; 28-34 psu salinity; 5-10 m water depth; 0.2-0.5 m/s velocity; rock, stone and muddy sand as substrate; and less than 20% mud in the substrate.

• 한국해양환경ㆍ에너지학회지
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• 제16권3호
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• pp.163-170
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• 2013

본 논문에서는 낙동강 하구역 진우도 자연해빈을 대상으로 해안표착물과 식생대 전선의 상관성 및 상호거동에 대하여 연구하였다. 해안표착물과 식생대 주변의 비사에 의한 퇴적 특성을 고찰하기 위해 현장 바람과 바닥조건을 고려하여 실내 풍동실험을 수행하였다. 본 연구에서 고려하는 주요 영향은 해안표착물과 식생대 주변의 바람에 의한 모래의 퇴적현상이다. 해안표착물에 대한 실험결과로서, 모형 전면부터 퇴적되고 퇴적된 높이가 모형의 70% 정도 퇴적되었을 때 모형 후면이 퇴적되는 양상이 나타났다. 이에 반해, 식생을 대상으로 한 실험에서는 모형 전면보다 후면이 먼저 퇴적되고, 후면이 전면보다 60%정도 더 높게 쌓이는 양상이 나타났다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.233-239
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• 2004

Microbial activity of biofilm formed on the surface of gravels from intertidal zone was estimated using an aerobic respirometer system, and compared with that of suspended marine microorganisms contained in a near shore water. The maximum oxygen uptake rate of the suspended marine microorganisms was 0.15mg O$_2$／L／hr, indicating the potential of purification of polluted near shore water. For the gravels from the intertidal zone, the maximum uptake rate of oxygen was affected by the vertical positions, but their gross value was 0.77mg O$_2$／L／hr, which was around 5.1 times higher than the purification potential of polluted near shore water by the microorganisms contained in the near shore water. The nitrogen removed by the gravels from the intertidal zone and the marine microorganisms was about 1／20-1／39 times of the total consumption of oxygen, which was similar to that of the phosphate. The gravel intertidal zone contained lots of particulate organics, over than that in the near shore water, and this was confirmed from the large difference between total oxygen consumption and the removed soluble COD in the microbial activity test. This indicates that the gravel intertidal zone plays an important role in controlling the non-point source pollutants from land, as well as self-purification of polluted near shore water by trapping and degrading the particulate organics.