• 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.

• 한국정밀공학회지
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• 제29권8호
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• pp.824-833
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• 2012

The shrinkage and the warpage of the moulded part are influenced by the design of the product and injection mould. In a flat part with a partly thick volume, the warpage of the flat part is created from the difference of the shrinkage between thin and thick regions. The warpage of the flat part with a partly thick volume can be reduced by a proper design of the cooling system in the injection mould. The goal of this paper is to design properly cooling channels of injection mould to manufacture a flat part with a partly thick volume. The conformal cooling channel is adopted to improve cooling characteristics of a region with the thick volume. The linear cooling channels are assigned to the other region. The proper design of the conformal cooling channels is obtained from three-dimensional injection molding analysis for various design alternatives. The moulding characteristics of the designed mould with both conformal and linear cooling channels are compared to those of the mould with linear cooling channels from viewpoints of temperature, shrinkage and warpage of the moulded part using numerical analysis. Injection mould with both conformal and linear cooling channels for the flat part with a partially thick volume is fabricated. In addition, injection moulding experiments are performed using the fabricated mould. From the results of the injection moulding experiments, it has been shown that the designed mould can successfully fabricate the flat part with a partially thick volume.

• 환경영향평가
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• 제11권1호
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• pp.51-66
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• 2002

The purpose of this study is to analyze the geomorphological environment changes of tidal flat in the Cheonsu Bay. Especially, it centers on the changes in the sedimentary environment using remote sensing data. Multi-temporal Landsat data and topographic maps were used in this study. The results are summarized as follows: the tidal flat of Cheonsu Bay changes in many ways depending on the direction of the tidal current. In the neighborhood of Ganwoldo, the scale of the tidal flat has continuously been expanded due to the superiority of sedimentation after a tide embankment was built. When we analyzed the grain size of sediments and implemented in-situ field survey, it was found that the innermost part of the bay consists of a mud flat, with the midway part mixed flat, and the nearest part to the sea sand flat. On the other hand, in the neighborhood of Seomot isle and its beach, sedimentation is superior in the eastern part whereas erosion is superior in the western part. In other words, the western coast of the beach is contacted with the open seas and under much influence of ocean wave. The eastern coast is placed at the entrance of the bay and has sand bar and tidal flat developed due to submarine deposits that are accumulated on the sea floor by the tidal current. In conclusions, remote sensing methods can be effectively applied for quantitative analysis of geomorphological changes in tidal flat, and it is expected that the proposed schemes can be applied to another geomorphological environments such as beach, sand dune, and sand wave.

• 경영과학
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• 제26권1호
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• pp.21-35
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• 2009

There is a controversy on Internet pricing, flat-rate vs. usage-based. This study gives a comparative analysis between flat-rate and two-part tariff which is realistic alternative of usage-based pricing. In a basic economic model, two-part tariff based on ISP's cost structure satisfies allocative efficiency and relatively expand the number of subscribers. But the characteristics of Internet service like consumers' uncertainty on cost, measurement cost of traffic and network externality induce increase of cost or decrease of marginal utility. The analysis shows that small impact of these can make flat-rate more efficient.

• 한국제4기학회지
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• 제18권2호통권23호
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• pp.19-22
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• 2004

Seasonal changes of topograpy, sediment grain size and accumulation rate on the Gomso-Bay tidal flat(Fig. 1), west coast of Korea, have studied in order to understand the seasonal accumulation pattern and preservation potential of tidal-flat sediments. Seasonal levelings across the tidal flat show that the landward movement of both intertidal sand shoals and cheiers accelerates during the winter and typhoon period, but it almost stops in summer when mud deposition is instead predominant on the middle to upper tidal flat. Seasonal variations of mean grain size were largest on the upper part of middle tidal flat where summer mud layers were eroded during the winter and typhoon periods(Fig. 2). Measurements of accululation depths from sea floor to basal plate reveal that accumulation rates were seasonally controlled according to the elevation of tidal-flat surface(Table 1) : the upper flat, where the accumulation rate of summer was generally higher than that of winter, was characterized by a continuous deposition throughout the entire year, whereas on the middle flat, sediment accumulations were concentrated in winter realtive to summer, and were intermittently eroded by typhoons. The lower tidal flat were deposited mostly in winter and eroded during summer typhoons. Cancores taken across the tidal flat reveal that sand-mud interlaers resulting from such seasonal changes of energy regime are preserved only in the upper part of the deposits and generally replaced by storm layers downcore(Fig. 3). Based on above results, it is suggested that the storm deposits formed by winter stors and typhoons would consist of the major part of the Gomso-Bay deposits(Fig. 4).

• 한국습지학회지
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• 제15권4호
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• pp.493-500
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• 2013

강화 남부 갯벌의 장기적인 퇴적환경 변화를 파악하기 위하여 1997년과 2011년 여름철 표층 퇴적물의 분포와 1998년 4월과 2013년 3월의 갯벌 고도를 비교하였다. 표층퇴적물은 1997년에 동부의 펄, 서부의 모래 펄 퇴적물이 우세하였으나, 2011년에는 동부의 선두리와 동검도 갯벌은 펄과 모래 펄, 중부의 동막리 갯벌은 모래 펄, 그리고 서부의 여차리와 장화리 갯벌은 모래와 펄 모래 퇴적물이 우세하게 분포하였다. 지난 14년 동안 펄 퇴적물 면적은 감소하였으나, 모래와 펄 혼합 퇴적물의 면적은 동쪽으로 확장되었다. 갯벌의 장기적인 지형 변화는 지난 15년 동안 동막리와 여차리 갯벌은 퇴적, 장화리 갯벌은 침식된 것으로 나타났다. 이러한 변화들은 1990년대 이후 강화 남부 갯벌 주변에 여러 종류의 인공구조물건설에 의하여 지역적인 수리적 변화가 영향을 주었을 것이다.

• 한국습지학회지
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• 제8권3호
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• pp.51-65
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• 2006

연구지역에서 2003년 8월에 199개 정점에서 표층퇴적물을 채취하여 분석하였다. 표층 퇴적물은 6개의 퇴적상으로 구성되어 있었다. 일반적으로 모래 펄 퇴적물이 강화 남단 갯벌에서 우세하였고 모래 퇴적물은 강화도 서부의 수로와 조하대에서 우세하였다. 이 지역의 1997년 퇴적상과 비교하여 모래펄 퇴적물은 갯벌의 동쪽으로 확장 되었다. 강화 남단 갯벌과 주변부 30 정점의 표층퇴적물에서 살아있는 유공충 34종을 포함하여 총 61종의 유공충이 확인되었다. 살아있는 유공충에서는 Ammonia beccarii와 Elphidium etigoense, 전체군집에서는 Ammonia beccarii, Elphidium etigoense, Jadammina sp.와 Textularia earlandi가 연구지역에 넓게 분포한다. 일반적으로 개체수와 종 다양성은 갯벌의 서부에서 상대적으로 높은 수치를 나타냈다. 전체 유공충 군집의 집괴분석 결과 4개의 생물상으로 구분되었다. 생물상 1은 강화 남단의 동부 갯벌, 생물상 4는 강화 남단의 서부 갯벌의 저서환경을 나타냈다. 생물상 3은 생물상 1과 4의 전이환경으로 보여 진다.

• 한국지리정보학회지
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• 제3권1호
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• pp.44-56
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• 2000

Landsat TM 영상을 이용하여 곰소만 간석지의 미지형을 분류하고, 현지조사를 통하여 분류된 각 미지형의 퇴적물 입도 특성과 지형특성을 밝혔다. 내만 쪽의 mud flat는 갯골과 갯골 사이의 평탄지로 이루어져 있으며, 평균입경이 $4{\phi}$ 이하의 세립질이고 분급은 1 S.D. 이상이며, positive skewness를 보인다. 만구쪽에 분포하는 sand flat는 갯골이 없이 평탄한 지형을 이루며 ripple mark가 발달해 있다. 분급이 좋은 모래로 대부분 구성되어 있고 negative skewness를 보인다. mixed flat는 mud flat 와 sand flat와의 중간적 특징을 보인다.

• 복식
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• 제34권
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• pp.67-78
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• 1997

We executed the wearing test in order to revise the basic Beosun pattern for five kinds of foot type. And we took sensory test to evaluated that revisions. The result were as follows: 1. The characteristics of slender foot is that the foot circumference III is short as compared with foot length. So Kou of basic Beosun is sharp-pointed Hoimok and beosunmok are broad. For slender foot we took down ou of Beosun and use foot cir-cumference III/2-1.5cm as Hoimok like the part shown in dotted line of Fin 6. 2. The characteristics of broad foot is that the foot circumference III is long as comparison with foot length. So Kou of ba-sic Beosun is stubby Hoimok and Beosunmok are narrow. For broad foot we took up Kou of Beosun put foot circum-ferenceI /2-1.5cm for the width of Apbol and circumfernce III 2/-1.5cm for Hoimok like the part shown in dotted line of Fig. 8. 3. because the arch of flat foot is flat the sole of basic Beosun is not suitable to the flat foot. It developes on wrinkles of Duichuk and sole. For flat foot we took down Hom of the basic Beousun like the part shown in dotted line of Fig. 10. 4 We evaluated the revisions of basic Beousun for foot types were useful in senso-ry test.

• 설비공학논문집
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• 제18권1호
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• pp.55-65
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• 2006

The air and water flow distribution are experimentally studied for a round header - flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is thirty. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.