• International Journal of Ocean System Engineering
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• 제2권3호
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• pp.176-184
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• 2012

Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.229-230
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• 2010

The Carbonation, one of the main deterioration factors of concrete, reduces capacity of members with providing rebar corrosion environment. Consequently it suggested standards of all countries of world, carbonation depth prediction equation of respective researchers and time to rebar corrosion initiation. As a result of carbonation depth prediction equation calculation, difference of time to rebar corrosion initiation is 149 years and difference of carbonation depth prediction equation is 162 years when water cement ratio is 50%. So a study on rebar corrosion with carbonation depth will need existing reliable data and verifications by experiment.

• 대한조선학회논문집
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• 제59권6호
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• pp.345-354
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• 2022

It is easy for a ship passing through confined waters to be exposed in dangers of collisions and grounding due to different hydrodynamic responses. Since marine accidents can cause significant impacts on environments, global economy, and human lives, it is necessary to study the effect of shallow water on hydrodynamic performance of a ship. In this paper, the effect of water depth on resistance performance was investigated using CFD analysis as an initial study for improving navigational safety of a large container ship under confined waters. After a CFD set-up for deep water condition was validated and verified by comparing CFD analysis with model test results, CFD calculations according to ship speed and water depth were conducted. The features were investigated in terms of tendency and physical knowledge related to resistance performance. The increase of resistance due to shallow water effect was reviewed with empirical formula suggested from SWABE JIP. Speed loss due to shallow water effect was additionally reviewed from estimated delivered power according to ship speed and water depth.

• 한국작물학회지
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• 제59권1호
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• pp.83-88
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• 2014

제주피의 발아특성 및 파종 심도에 따른 초기 생육 특성을 조사한 결과를 요약하면 다음과 같다. 가. 사료피 1호 종자는 $15^{\circ}C$ 이상에서 발아가 가능하였으며, $10-25^{\circ}C$의 범위에서 $20^{\circ}C$에서 가장 높은 발아율을 보였다. 나. 입모율은 담수와 직파에서 모두 $20^{\circ}C$에서 가장 높았으며, 담수직파에서 평균 입모율은 5.9%, 건답직파는 70.5%로 나타났다. 다. 사료피 1호의 출아가 가능한 종자의 최대 파종 깊이는 담수직파에서 15, 20, $25^{\circ}C$에서 0.5, 1.8, 1.5 cm, 건답직파는 각각의 온도에서 9.5, 10.0, 9.9 cm로 파종조건과 온도에 따라 변이를 보였다. 라. 사료피 1호는 담수와 건답직파 모두에서 온도와 관계없이 파종심도와 중배축장이 정의상관관계를 보여, 출아에 중배축 신장이 가장 크게 영향을 미치고 있을을 알 수 있다.

• International Journal of Concrete Structures and Materials
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• 제10권2호
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• pp.249-256
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• 2016

This paper deals with the effects of silica fume content and polymer-binder ratio on the properties of ultrarapid-hardening polymer-modified mortar using silica fume and ethylene-vinyl acetate redispersible polymer powder instead of styrene-butadiene rubber latex to shorten the hardening time. The ultrarapid-hardening polymer-modified mortar was prepared with various silica fume contents and polymer-binder ratios, and tested flexural strength, compressive strength, water absorption, carbonation depth and chloride ion penetration depth. As results, the flexural, compressive and adhesion strengths of the ultrarapid-hardening polymer-modified mortar tended to increase as increasing polymer-binder ratio, and reached the maximums at 4 % of silica fume content. The water absorption, carbonation and chloride ion penetration resistance were improved according to silica fume content and polymer-binder ratio.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.61-64
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• 2005

The calculated characteristics of groundwater within the Youngsan river basin are : casing depth-17.1m, well depth-74.8m, natural water-2.6m, pumping water-43.9m, yields-391$m^3/D$, transmissivity-16.3$m^3/D/m$, storativity-0.068. As far as hydrogeological units are concerned, in casing depth, weathered granites are deepest followed by gneiss, volcanics, and sediments. In major aquifer development areas, sediments are deepest followed by volcanics, granites and gneiss in more shallow areas, Altogether, the major aquifar development depth of the Youngsan river basin is within the $35{\sim}60m$ range.

• 한국해양공학회지
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• 제37권6호
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• pp.256-265
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• 2023

Many numerical methods have been developed since 1961, but unresolved issues remain. This study developed a numerical method to address these issues and determine the coefficients and properties of rotational waves with a shear current in a finite water depth. The number of unknown constants was reduced significantly by introducing a wavelength-independent coordinate system. The reference depth was calculated independently using the shooting method. Therefore, there was no need for partial derivatives with respect to the wavelength and the reference depth, which simplified the numerical formulation. This method had less than half of the unknown constants of the other method because Newton's method only determines the coefficients. The breaking limit was calculated for verification, and the result agreed with the Miche formula. The water particle velocities were calculated, and the results were consistent with the experimental data. Dispersion relations were calculated, and the results are consistent with other numerical findings. The convergence of this method was examined. Although the required series order was reduced significantly, the total error was smaller, with a faster convergence speed.

• 한국측량학회지
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• 제30권1호
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• pp.97-104
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• 2012

본 연구에서는 2011년 강원도 영동 지방의 폭설 기간 동안 GPS 위성 신호의 대류권 지연량 추정으로부터 대기 가강수량을 복원하였다. 폭설이 발생하는 기간 동안에 GPS 가강수량과 신적설 발생량과의 상관관계에 대한 분석을 실시하였다. 분석 결과, GPS를 이용하여 복원한 대류권에서의 가강수량 증가가 발생된 이후에 강설량이 증가하는 추세를 나타냈다. 또한 웨이블릿을 이용한 주기 분석에서는 본 연구기간에 한해서 GPS 가강수량의 주기가 포화수증기압의 주기와 유사한 것으로 검출되었다. GPS 가강수량의 감소와 이에 대응하는 신적설량의 증감은 두 연구 지역인 강릉과 울진에서 모두 다르게 증감하는 경향을 나타냈다. 폭설 기간 동안 GPS 가강수량과 포화수증기압의 상관 계수는 강설이 발생하지 않는 기간 동안의 결과와는 달리 양의 상관성을 갖는 것으로 나타났다.

• 한국토양비료학회지
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• 제38권3호
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• pp.150-156
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• 2005

논토양에서 관개 깊이를 조절하여 온난화가스 배출특성을 구명하고, 그에 따른 온난화가스 배출량를 추정하여 온난화가스 배출 저감기술을 확립하고자 연구를 수행하였다. 볏짚시용후 담수 8 cm의 시기별 $CH_4\;flux$는 이앙 32일 경에 $23.9mg\;m^{-2}\;h^{-1}$로 가장 높았으며, 이앙 35일 이후부터 감소하기 시작하여 중간낙수 이후에는 $CH_4\;flux$가 급격히 감소하였다. 포화용수량 처리구의 시기별 $CH_4\;flux$는 이앙 32일에 $19.9mg\;m^{-2}\;h^{-1}$ 로 가장 높았으며, 전 생육시기 동안 담수 8 cm와 담수 4 cm에 비하여 $CH_4\;flux$는 적었다. 볏짚 무시용후 시기별 $CH_4\;flux$는 이앙 20일경 $2.2-3.8mg\;m^{-2}\;h^{-1}$의 범위를 보였으며 그 이후부터는 처리별 차이가 컸으나 이앙 50일 이후부터는 비슷한 경향을 보였다. 토양 Eh 변화는 벼 이앙후 20일부터 -100 mV로 낮아 졌으며, 중간낙수 이후인 이앙 60일경에는 50 mV로 상승하였고 논물 담수심이 낮을수록 토양 Eh는 높았다. 볏짚을 시용하지 않았던 구와 포화용수량 처리구에서의 토양 Eh변화는 볏짚 시용구에 비하여 벼 전 생육기간에 걸쳐서 높았다. 처리별 지구온난화지수는 볏짚 시용후 담수 8 cm 처리구가 $6,939kg\;CO_2\;ha^{-1}$, 담수 4 cm 처리구는 $6,431kg\;CO_2\;ha^{-1}$, 포화용수량 처리구는 $5,222kg\;CO_2\;ha^{-1}$ 이었다. 그리고 볏짚을 시용하지 않은 담수 8cm 처리구의 지구온난화지수는 $4,449kg\;CO_2\;ha^{-1}$, 담수 4 cm 처리구는 $3,702kg\;CO_2\;ha^{-1}$, 포화용수량 처리구는 $3,561kg\;CO_2\;ha^{-1}$ 이었다.

• Ocean and Polar Research
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• 제26권2호
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• pp.377-384
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• 2004

Annual variations of inorganic nutrients such as nitrate(+nitrite), phosphate and silicate in association with thermocline were investigated in the upper 200 m of the water column at KODES Long-term Monitoring (KOMO) station in the northeast equatorial Pacific from 1995 to 2002. Global climatic disturbances such as El Nino and La Nina, should have affected KODES area during the study period. In 1995-97 and 2000-2002, a thermocline where temperatures rapidly decrease with depth, was formed at 50-70 m water depth. Nutrient depletion, specially for nitrate and phosphate, was extended down to approximately 50 m depth, which coincided with the surface mixed layer depth. In 1998 and 1999, however a very fluctuating thermocline was observed at 20-100 m water depth. In the photic zone (up to 100 m depth), depth integration of nitrate, phosphate and silicate ranged from 2.02 to $23.14\;gN/m^2$, from 0.87 to $4.05\;gP/m^2$ and from 35.67 to $176.21\;gSi/m^2$, respectively. As a result of changes in the water column structures, nutrient concentrations also showed fluctuation parallel to the changes of thermocline in the study area.