• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.719-722
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• 2005

The watertightness of concrete is judged by the depth of penetration of water forced in under pressure with the mechanism of flow of seepage water examined theoretically and experimentally. As a result, it is found that in the case of low water pressure approximately 0.15Mpa or less, the flow is Darcy seepage flow, the same as flow in an ordinary sand stratum, whereas in the case of high water pressure, the flow is diffused seepage flow accompanied by internal deformation of concrete. It is suggested that the watertightness of concrete be evaluated by seepage coefficient in the case of the former and diffusion coefficient in the case of the latter.

• 콘크리트학회논문집
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• 제25권2호
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• pp.145-153
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• 2013

촉진 염화물 확산계수는 최근들어 염화물 거동 평가를 위하여 많이 사용되고 있다. 촉진 염화물 확산계수는 겉보기 확산계수와 마찬가지로 재령에 따라 감소하는데, 이 연구에서는 공극률을 이용하여 촉진확산계수의 감소를 구현하였다. DUCOM 프로그램을 이용하여 15 배합에 대한 공극률을 도출하였으며, 이를 회귀분석하여 재령 270일 동안 감소하는 염화물 확산계수를 모델링하였다. 또한 자유염화물과 구속염화물간의 관계인 비선형 구속능을 고려하여, 고성능 콘크리트내의 염화물 거동을 평가하였다. 기존의 실험자료인 180일간 염화물에 침지되어 있는 시편을 이용하여, 이 연구에서 제안한 기법의 검증을 수행하였다. 제안된 기법은 다양한 물-시멘트비 및 혼화재(고로슬래그 미분말 및 플라이애쉬)를 가진 고성능 콘크리트의 염화물 거동을 적절하게 평가하였다. 또한 혼화재료를 사용한 콘크리트의 경우, 확산계수의 시간의존성이 뚜렷하므로 염화물 거동 해석시 재령에 따른 염화물 확산계수의 감소를 반드시 구현해야 함을 알 수 있었다.

• 상하수도학회지
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• 제21권1호
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• pp.101-112
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• 2007

This study has used RMA2 model and RMA4 model, which are depth-averaged two-dimensional flow and water-quality prediction models, to analyze the variation of the water-quality by the gates operation in the Seonakdong River. Sensitivity analysis is performed to get the Manning coefficient and the coefficient of eddy viscosity for RMA2 model, and to get the diffusion coefficient for RMA4 model. Since the numerical simulation using RMA2 and RMA4 models did not consider tributary pollutant load except for that of Joman River, it could make a little difference from the natural phenomenon. Nevertheless, the numerical simulation shows that the discharge of $30m^3/s$, which is the continuous inflow from the Daedong-gate, can make it possible to achieve the target water-quality (BOD 4.3mg/L) of Nakbon-N watershed about 10 days later if the Daejeo-gate could remain opened in connection with the Noksan-gate operation.

• 대한기계학회논문집
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• 제16권6호
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• pp.1171-1178
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• 1992

본 연구에서는 직접접촉식 열교환기를 이용한 실험을 통하여 열교환기 설계에 가장 중요한 열교환기 단위 체적당 총괄 열전달 계수를 시스템의 작동조건에 따라 구 하여 실제 설계자료로 이용하는 데 그 목적이 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.679-684
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• 2002

In this study we performed test to compare and analyze the chloride diffusion properties in concrete according to organic coating materials used at concrete structures widely and inorganic coating materials as eco-materials in recently. The results of study were shown as follow ; 1) Chloride diffusion coefficient was low as low as and that of organic and inorganic painted was lower than non-painting 2) In case of inorganic coating material applied in this study, it should be possible to evaluate the chloride diffusion properties by CTH method. Because presumption value by CTH method is similar with real estimate value by digestion experiment.

• 패션비즈니스
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• 제20권6호
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• pp.66-78
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• 2016

Hygroscopic knitted cotton fabric was found to spontaneously absorb water showing a significantly wide concentration gradient in the absorption direction. A semi-empirical diffusion model was introduced to describe how the wicking behavior compared to the classical capillary model (Washburn's equation), which has been widely used in the textiles industry. The capillary sorption curve and the permeability coefficient, which are key variables for the model equations, were measured using an electronic balance. The concentration profile as a function of the wicking distance and the elapsed time was derived, based on the diffusion model. From the concentration profile, the wicking distance detectable by the human eye or a digital camera with the aid of an image-analysis system, could be described realistically as a function of the time. The classical capillary model could be modified by introducing the tortuous correction factor to match the diffusion model. Wicking models and data-processing techniques in the work could provide useful tools for objectively evaluating the textile's wicking performances.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.281-284
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• 2003

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the sea water. Because the damages of corrosion resulting from the chloride ion are very serious, many research have been performed. In this study, it was experimentally investigated that the mechanical and diffusion characteristics of concrete substituted with ordinary portland cement, silica fume and blast furnace slag to investigate the chloride ingress characteristics with concrete quality. Chloride diffusion coefficients in concrete shows increasing tendency as w/c ratio increase. Also test results indicate that blend of admixture become lower chloride diffusion coefficients in concrete as compared with normal concrete.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 추계학술대회 논문집
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• pp.186-191
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• 1999

The coagulation process of PAN (poly(acrylonitrile)) wet-spinning was modeled and simulated based on the numerical analysis of the coagulation of a viscous polymer solution by diffusional interchange with a bath. Experiments were performed with gelled solutions of PAN in nitric acid to determine the diffusion rate of solvent and nonsolvent (water) during the coagulation. The experimental data were analyzed by using equations of diffusion coefficient which are the function of the solvent concentrations of the coagulation bath and the filament. The concentration profile of solvent in moving filament was predicted by solving the diffusion model equation numerically. A simplex method was used in the computation of the parameters of the diffusion equations to minimize the difference between the numerical results and experimental data.

• 한국해안해양공학회지
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• 제4권4호
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• pp.261-270
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• 1992

서해안에 위치한 태안근해에서 대조기 때 유동특성 및 물질확산을 연구하기 위해서 조류, 염료운 및 온배수의 확산에 대한 현장관측, 수리실험 및 수치실험을 실시하였다. 현장관측, 수리 및 수치실험에 의한 유황은 상호간에 대체로 잘 일치하였다. 현장에서 조류는 해안선을 따라 낙조류시에는 남서방향으로, 창조류시에는 북동방향으로 탁월하게 흐르고, 대상영역내 최대유속은 WSW 방향으로 2.13㎧로 관측되었다. 현장에서 유속관측치로부터 구한 Eulerian 확산계수는 7.82$\times$$10^{5}$ $ extrm{cm}^2$/s이다. 수리모형에서 염료운의 면적으로부터 구한 확산계수는 0.18 $r^{(4}$3)/이며, 그 크기는 $10^{5}$ ~$10^{6}$$\textrm{cm}^2$/s로서 현장에서 Eulerian 확산계수와 비슷하게 나타났다. 모형실험에 의한 당 해역의 확산계수는 남해안에 위치한 진해만에서 구한 확산계수보다는 2~3 order, 동해안에 위치한 온산만에서 구한 확산계수보다는 1~2 order 크게 나타났다. 화전(1975)의 2차원 수치모델을 적용한 결과 얻어진 온배수의 확산양상은 수리실험에 의한 염료운의 확산양상과 유사하게 나타났다. 수리실험 및 수치실험 결과에 의하면, 태안해역의 물질확산은 창조류 때보다 낙조류 때 탁월하게 일어났다.다.

• 한국해양학회지
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• 제10권2호
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• pp.57-66
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• 1975

Structure of thermocline, characteristics of stability and intensity of vertical transfer have been studied with hourly oceanographic data in each layers on Line 207 from 1968 to 1969. It is found that a typical thermocline is formed at depths of 10 to 50 meters in summer and early autumn and its core is located near depths of 25 meters. The maximum diffusion coefficient of vertical turbulent is found to be 140$\textrm{cm}^2$/sec at the surface layer(i.e., 0-10 meters), while the minimum is 5$\textrm{cm}^2$/sec at depths of 25 meters, consistent with characteristics of stability and structure of thermocline layers. Our computed diffusion coefficient and stability indicate that the mixing hardly takes place below depths of 80 meters during summer and early autumn, but for the rest of the season mixing could move up to the depth of 50 meters. It appears that the Western Channel of the Korea Strait consist of three different water masses during summer and autumn, and for the rest of the season, two kinds are present.