• Ocean and Polar Research
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• 제24권4호
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• pp.331-343
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• 2002

The southern tidal flat of Kanghwa Island with an area of approximately $90km^2$ is one of the biggest flats on the west coast of Korea. Surface sediments for sedimentary analyses were sampled at 83 stations in August 1997, September 1999 and August 2000. The very poorly-sorted mud sediments were predominant in the eastern part of the tidal flat, whereas the poorly-sorted sand-mud mixed sediments were dominant in the western part. The area of muddy sediment distribution diminished, but that of sandy mud sediment extended to southeastward tidal flat for three years. In the western part of tidal flat, deposition occurred during the period of spring to summer, whereas erosion occurred in winter. Sediment accumulation rates during three years indicated that the sediments deposited continuously in the eastern part of tidal flat, whereas eroded in the western part of tidal flat. Recently, construction of artificial structures such as new airport, island-connecting bridges and dikes near the tidal flat might change tidal current and river flow pattern. In order to reduce the ecological damage and to preserve tidal-flat environment, it is necessary to Investigate long-term impacts on sedimentary environment and ecology.

• Water Engineering Research
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• 제6권1호
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• pp.17-30
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• 2005

The bed evolution of the stretch of the River Rhine between km-812.5 and km-821.5 is characterised by general bed degradation as a result of the river training works and dredging activities of the last two centuries. The degradation of the river bed affects the water levels, and so the navigation conditions. To combat the erosion of the river bed with the aim to keep up the shipping traffic and to avoid the ecological system damages due to water level reductions, sand-gravel-mixtures were added to the river (so called artificial grain feeding activities). This paper presents the results of an application of a graded sediment transport model in order to study morpholodynamical characteristics due to artificial grain feeding activities in the river stretch. The finite element code TELEMAC2D was used for flow calculation by solving the 2D shallow water equation on non-structured grids. The sediment transport module SISYPHE has been developed for graded sediment transport using a multiple layer model. The needs to apply such graded sediment transport approaches to study morphological processes in the domain are discussed. The calculations have been carried out for the case of middle water flow and different size-fraction distributions. The results show that the grain feeding process could be well simulated by the model.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.203-210
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• 2004

Consolidation properties were analysed by means of depositional environments. Depositional environments including geochemical properties, porewater chemistry, sediment structures, particle size distributions and carbon age dating were analysed using undisturbed samples retrieved successively from a boring hole in the study area. Laboratory oedometer tests and anisotropic consolidated triaxial tests(CKoUC) were performed to examine the overconsolidation phenomenons. Based on the carbon age dating results and profiles of geochemical properties, porewater chemistry, salinity and pH, it was founded that the upper silt/clay complex layer was deposited under marine condition while sand and clay layers were deposited under fluvial condition. Planar laminated structures of silts and clays were dominant in marine deposits. Although there was no clear evidences that geological erosion had been occurred in marine deposits, overconsolidation ratio obtained from oedometer tests were greater than unity. Stress paths of samples behaved similar to those of normally consolidated clays. Data plotted in stress state charts proposed by Burland(1990) and Chandler(2000) showed that the marine deposits were geologically normally consolidated. These apparent overconsolidations can be explained by the fabric and chemical bonding due to the difference of the rate of deposition.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.72-77
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• 2005

The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.

• 한국지반신소재학회논문집
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• 제16권1호
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• pp.53-61
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• 2017

바다 자원의 조성을 위해 시설되는 인공어초는 해저 연약지반에 설치될 경우 침하 및 세굴에 의한 기능 상실이 발생할 수 있다. 따라서 본 연구에서는 해저 연약지반의 보강에 따른 인공어초의 침하 거동을 알아보기 위해 모래, 실트 및 점토 지반을 각각 조성하여 관입실험, 침하실험 등과 같은 다양한 실내실험을 수행하였다. 무보강(unreinforced), 지오그리드(geogrid) 보강 및 하이브리드 대나무매트(hybrid bamboo mat, HBM) 보강과 같은 3종류의 보강과 보강재의 면적에 따른 특성을 살펴보았다. 실험 결과 보강재의 면적이 증가할수록 보강 효과가 증가하는 경향을 보였으며, HBM이 지오그리드 단일 보강에 비해 더 뛰어난 보강 효과를 보였다.

• 디지털콘텐츠학회 논문지
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• 제18권4호
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• pp.787-793
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• 2017

본 논문은 기존의 단순한 수위측정 방식과는 달리 저수지 및 사방댐 등의 담수량 및 토사의 퇴적량을 단위체적블록 객체모델링을 통하여 실시간 측정하고, 해당 정보를 영상 정보와 같이 제공하는 IoT기반 소규모 저수지/사방댐 담수량 및 토사량 모니터링 시스템을 제안한다. 제안 시스템은 점차 강화되고 있는 사방댐 관리규정과 함께 보다 정확한 준설계획의 수립과 효율적인 물 관리가 가능하고, 산사태 등의 재해사고 방지에 매우 효과적이다.

• 한국동물위생학회지
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• 제13권2호
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• pp.111-129
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• 1990

Based on the gross lesion, a survey of ulcer prevalence was carried out on pigs (3,161 heads) at a slaughterhouse in seoul from April to December in 1989. The pigs stomachs were observed anatomically and classified, according to the presence or absence of foreign bodies. Ulcer prevalence is usually classified according to size of pig farm, ages, and supplied month. The results in the studies were as follows, 1. Fundus followed the highest rate with 28.2%, esophagus with 24.5％ each of cardiac and pyloric part with 7.8% and 4.1％ in cases of gastric mucosa pathological studies examed total 3,161. In the acute ulcer prevalence, fundus follwed with 5.4%, esophagus with 2.6%, each of cardiac and pyloric part with 0.8% and 0.3%. When prevalent frequencies of fundus are compared with cardiac and pyloric part, they have meaning.(P <0.05). 2. In the survey pig of total 3,161, pathological changes of epithelium tissue foliowed 44.0%, erosion(11.5%), chronic ulcer(14.8%), acute ulcer(1.6%), scar formation (1.7%) and perforation (0.9%). 3. In general monthly prevalence rates of gastric lesion are higher in spring and fall than in summer. 4. In the size of pig farms, ulcer showed higher rate at professional farms than raising on the side. 5. When there are more fluid condition in stomach and they are old, the ulcer appeared for more. 6. Foreign bodies in stomach were sand, hairballs, and intestinal worms were detected (1%).

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.260-265
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• 2004

The materials of ship screw propeller are commonly the manganese bronze. The seawater corrosion and cavitation of the screw propeller reduce tire propulsive performance of ship. In screw manufactory, tire corrosion rust of tire screw propeller is removed by a hand grinding. The grinding work makes the dust of the heavy metals from the manganese bronze. The dust makes indoor working environment poor. A friendly-environmental and automatic corrosion removing apparatus was developed for the improvement of screw processing and working environment. The corrosion rust of a screw propeller was remarkably removed by using apparatus. And the screw surface roughness was improved by a blasting effect of the apparatus performance test. Anode polarization curves on jour processing conditions, that is to say, grinding, blasting, wire-brushing, fine sand papering, were confirmed by a potentiostat. Especially, two kinds of medias, alumina and emery, were used in the blasting processing. Then, investigated tire cavitation erosion of specimen. This result proved that tire blasting work has considerably improved the corrosion resistance of a screw propeller.

• 한국지형학회지
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• 제19권4호
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• pp.27-37
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• 2012

본 연구는 강원도 철원군 명성산 화강암과 현무암 용암대지 사이의 접촉대인 한탄강 승일교 인근 지역의 독특한 경관을 형성하고 있는 화강암 하천 침식 및 퇴적 지형과 풍화 지형 분석을 다루고 있다. 주요 화강암 지형으로서는 심층풍화된 구릉, 면상침식지형, 고지형면 및 고토양, 하천작용과 관련된 미지형으로 돌개구멍과 그루브, 램 파트형의 암괴, 사주와 사력퇴, 그리고 구하상 등이 있다. 그리고 풍화가 덜 진전된 구릉의 일부로 하천의 측방이동을 방해하는 화강암 하식애 지형이 있다.

• 한국지형학회지
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• 제23권3호
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• pp.93-104
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• 2016

High school textbooks of world geography show geomorphic featuresin arid environments such as sand dune, yardang and ventifact which are largely created by aeolian processes. Desert pavements, ubiquitous armored surfaces composed of a mosaic of clasts in hot and arid regions, are introduced as a major landform which can be attributed to wind erosion. However, they are formed by a variety of processes including deflation, surface runoff, upward clast migration and dust accretion that cause coarse particles concentration at the surface. The deflation by wind leaving a lag of coarse clasts has been solely regarded at home, even though the classical mechanism of deflation has been evaluated as a relatively unimportant process of pavement formation abroad through empiricalstudies. The accretionary model is gaining wider acceptance, thus implying that desert pavements could be formed through deposition of aeolian material. In addition, sheetflood and upward migration of clasts, irrelevant to the aeolian processes, could also create stone pavements. As a consequence, the deflation process in high school textbooks has to be urgently modified into a range of processes including aeolian mantling. By stressing that desert pavements are an exceptional geomorphic feature in deserts where wind is a predominant geomorphic agent, they can be used as a good example to demonstrate that a landform is not monogenetic.