• Journal of the korean society of oceanography
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• 제38권2호
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• pp.60-67
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• 2003

Typhoon Rusa passed over the East China Sea and crossed over the Korea Peninsula on August 31, 2002. The core of the typhoon passed directly over a data buoy mooring site at ($127^{\circ}45'E,\;34^{\circ}25'\;N$) and several ARGOS-tracked drifters capable of measuring salinity. Peak hourly mean wind speed reached 28 m/s at the mooring site and wind pattern in the East China Sea changed from southerly wind to northwesterly wind after the typhoon passage. Two or three days before the typhoon tile drifter displacement changed significantly and the region-wide circulation pattern changed from a northeastward current to a westward current one week after the typhoon had passed. The surface water in the East China Sea was cooled to about $4^{\circ}C$ under the typhoon core and a general cooling occurred in most of the East China Sea with the exception of the Chinese coast. The salinity as observed by the drifters in the East China Sea increased about 2 psu but the near-shore water along the Korean coast observed by the mooring was freshened about 3 psu. The freshening of near-shore water was caused by an intrusion of off-shore water rather than local freshening by typhoon precipitation.

• 한국해양학회지
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• 제6권1호
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• pp.16-24
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• 1971

Over 40 bottom sediment samples were collected from the southern sea of Korea. The detailed textural characteristic of the sediments, percent calcium carbonate and heavy and light mineralogy were determined. Seaward of these sediments is a nearly broad belt of sandy sediments. In a broad outline it is considered to constitute a near-shore deposits left from a Pleistocene time of eustatically lowered level of sea water, because the sediments on the outer half of the continental shelf are much coarser than that nearer shore. The carbonate content increases strongly to the southeast and northwest of Cheju Island. It is believed that the high calcium carbonate content can be largely attributed to the availability of carbonate materials.

• 대한토목학회논문집
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• 제29권1B호
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• pp.83-90
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• 2009

본 연구는 잔교를 설계할 때 수리모형실험을 통하여 잔교상판에 작용하는 양압력 분포 특성에 대해 기술하였다. 양압력이 상판하부에 작용할 때 압축공기 유출의 유무에 따라 양압력이 작용하는 형상이 다르고 양압력의 크기가 다르게 분포하고 있음을 알았다. 동일 Block 상판내의 양압력분포는 상판의 중심점과 가장자리에서 동일한 분포를 하지 않는 결과를 얻었다. 양압력 분포특성은 잔교길이인 무차원(l/L), 파형경사(H/L), 공간(D/H)에 의해 영향을 받는다. 양압력에 영향을 미치는 무차원 요소(H/L)은 양압력의 최대치를 결정하는 D/H의 값이 존재하고 있다는 것을 알았다. 동일한 D/H인 경우도 양압력은 파형경사에 따라서 변화하고 있다. 즉, H/L이 클수록 (D/H)이 작기 때문에 잔교를 설계할 때 $D_{max}$가 되는 Clearance가 생기지 않는 상판높이를 정하는 것이 안전한 설계가 된다. 압축공기가 양압력에 미치는 영향을 검토한 결과 양압력이 크게 작용하는 On-shore에서는 Off-shore보다 압축공기에 의한 양압력의 저감효과가 크게 발생하고 있다. 상판에 작용하는 양압력을 저감시키기 위해서는 압축공기 유출을 방지하는 상판설계가 필요하다.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.35-48
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• 2015

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

• 해양환경안전학회지
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• 제7권2호
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• pp.13-22
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• 2001

We studied the characteristics of marine casualties within the area under control of Korea National Maritime Police and leeway of drifting vessel. According to 5 years＇(1995~1999) data of casualties, it was found that the occurrence of casualties by fishing boats ranked the highest and a considerable numbers of casualties took place more than 20 miles off the shore. From a result of field experiment of G/T 50 tons vessel off Busan harbor on Apr. 26~28, 2000, we computed that the linear equation of leeway speed(cm/s) was 1.01$\times$U(U : wind speed in m/s)+11.36 with correlation coefficient between wind speed and leeway speed being 0.252 and we found leeway angle range from $+87^{\circ}$(right) to $-78^{\circ}$(left ) of the downwind direction.

• 한국환경과학회지
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• 제7권3호
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• pp.291-300
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• 1998

Recently, upwelling of anoxic bottom water mass have been frequently observed in northeast part of Tokyo Bay in Japan during summer to autumn. Since the colour of water surface becomes milkyblue or milkygeen, the upwelling phenomenon Is called 'Blue Tide'. The data analysis of field surveys during 'Blue Tide' appearance have been performed for understanding the physical features of the 'Blue Tide' phenomena In Tokyo Bay. It becomes clear that (1) the formation of the anoxic bottom water correlates well with the temperature difference between the surface and bottom waters, (21 there are two necessary conditions for generating 'Blue Tide': that Is, strong stratincation and off-shore wind. The strong southwest(on-shored wand before the 'Blue Tide' appearance may play an iniportant role to make the striancation strengthen. When these conditions are larger and the northeast or east-northeast (off-shored wind stronger than S ifs blows In succession, the 'Blue Tide' upwelling appears at the head of Tokyo Bay.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.210-216
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• 2016

조선해양플랜트 기자재 중 텔레콤 장비들의 고장, 오동작 등은 선박이나 해양플랜트의 안전항해 및 운영에 부정적인 영향을 미친다. 특히 해양플랜트는 작업 환경과 설비가 복잡하기 때문에 사고 위험이 높고 안전 사고가 발생하면 심각한 금전적 피해와 환경오염이 발생한다. 따라서 선박 및 해양플랜트의 안전 항해 및 운영 등을 위해 선박이나 해양플랜트 내 텔레콤 장비를 네트워크로 연결한 후 데이터를 취합하여 육해상에서 모니터링할 수 있도록 하는 자동화된 시스템이 필요하다. 이에 본 논문에서는 텔레콤 장비 관리 관련 표준인 NORSOK T-100을 기반으로 요구사항 및 기능 목록을 작성하고, 사용자 편의 측면의 요구사항을 더하여 TMS을 새롭게 설계하고 개발하였다. 또한 실험 환경을 구축하여 TMS가 정상적으로 동작함을 확인하기 위해 실험 환경을 구축하였다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1066_1067
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• 2009

Wind power is one of most promising renewable energy. The output capacity of large wind turbine has been increased for off-shore application. Number of installation of small wind turbine also has been increased for the stand-alone and off-grid application of remote area and recently small wind turbine equipped with lamp on the pole is used for street lamp. Maximum wind energy must be extracted by wind turbine within rated wind speed. Power must be controlled to protect the system such as blade, generator, and power system above the rated wind speed. In this paper, small wind power system of 800W rating for battery charging is implemented and output power control by furling system is verified at wind tunnel test.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.73-81
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• 2020

For the fault tree analysis (FTA) analysis of the packaged hydrogen filling station, the composition of the charging station was analyzed and the fault tree (FT) diagram was prepared. FT diagrams were created by dividing the causes of events into external factors and internal factors with the hydrogen event as the top event. The external factors include the effects of major disasters caused by natural disasters and external factors as OR gates. Internal factors are divided into tube tailer, compressor & storage tank, and dispenser, which are composed of mistakes in operation process and causes of accidents caused by parts leakage. In this study, the purpose was to improve the hydrogen station. The subjects of this study were domestic packaged hydrogen stations and FTA study was conducted based on the previous studies, failure mode & effect analysis (FMEA) and hazard & operability study (HAZOP). Top event as a hydrogen leaking event and constructed the flow of events based on the previous study. Refer to "Off shore and onshore reliability data 6th edition", "European Industry Reliability Data Bank", technique for human error rate prediction (THERP) for reliability data. We hope that this study will help to improve the safety and activation of the hydrogen station.