• Computers and Concrete
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• 제13권2호
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• pp.149-171
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• 2014

This study presents the mathematical model for predicting chloride penetration into saturated concrete under non-isothermal condition. The model considers not only diffusion mechanism but also migration process of chloride ions and other chemical species in concrete pore solution such as sodium, potassium, and hydroxyl ions. The coupled multi-ionic transport in concrete is described by the Nernst-Planck equation associated with electro-neutrality condition. The coupling parameter taken into account the effect of temperature on ion diffusion obtained from available test data is proposed and explicitly incorporated in the governing equations. The coupled transport equations are solved using the finite element method. The numerical results are validated with available experimental data and the comparison shows a good agreement.

• Corrosion Science and Technology
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• 제8권2호
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• pp.74-80
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• 2009

The high alkaline property in the concrete pore solution protects the embedded steel in concrete from corrosion due to aggressive ions attack. However, a continuous supply of those ions, in particular, chlorides altogether with a pH fall in electrochemical reaction on the steel surface eventually depassivate the steel to corrode. To mitigate chloride-induced corrosion in concrete structures, finely grained mineral admixtures, for example, pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) and silica fume (SF) have been often advised to replace ordinary Portland cement (OPC) partially as binder. A consistent assessment of those partial replacements has been rarely performed with respect to the resistance of each binder to corrosion, although the studies for each binder were extensively looked into in a way of measuring the corrosion rate, influence of microstructure or chemistry of chlorides ions with cement hydrations. The paper studies the behavior of steel corrosion, chloride transport, pore structure and buffering capacity of those cementitious binders. The corrosion rate of steel in mortars of OPC, 30% PFA, 60% GGBS and 10% SF respectively, with chloride in cast ranging from 0.0 to 3.0% by weight of binder was measured at 7, 28 and 150 days to determine the chloride threshold level and the rate of corrosion propagation, using the anodic polarization technique. Mercury intrusion porosimetry was also applied to cement pastes of each binder at 7 and 28 days to ensure the development of pore structure. Finally, the release rate of bound chlorides (i.e. buffering capacity) was measured at 150 days. The chloride threshold level was determined assuming that the corrosion rate is beyond 1-2 mA/$m^3$ at corrosion and the order of the level was OPC > 10% SF > 60% GGBS > 30% PFA. Mercury intrusion porosimetry showed that 10% SF paste produced the most dense pore structure, followed by 60% GGBS, 30% PFA and OPC pastes, respectively. It was found that OPC itself is beneficial in resisting to corrosion initiation, but use of pozzolanic materials as binders shows more resistance to chloride transport into concrete, thus delay the onset of corrosion.

• Advances in environmental research
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• 제4권2호
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• pp.105-117
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• 2015

The groundwater is a very important part of the environment and must be protected for the benefit of the present and future generation. The contamination of soil and groundwater by chemicals has become an increasing concern in the recent past. These chemicals enter the groundwater system by a wide variety of mechanisms, including accidental spills, land disposal of domestic and industrial wastes and application of agricultural fertilizers. Once introduced into an aquifer, these contaminants will be transported by flowing groundwater and may degrade water quality at nearby wells and streams. For improving the management and protection of groundwater resources, it is important to first understand the various processes that control the transport of contaminants in groundwater. Predictions of the fate of groundwater contaminants can be made to assess the effect of these chemicals on local water resources and to evaluate the effectiveness of remedial actions. In this study, an attempt has been made to investigate the behaviour of solute transport through porous media using laboratory experiments. Sodium chloride was used as a conservative chemical in the experiment. During the experiment, pulse boundary condition and continuous boundary conditions were used. Experimental results have been presented for conservative solute transport in the sand. The pattern of the break through curve remains almost same in all the cases of varying flow rate and initial concentration of conservative chemical.

• 대한한방내과학회지
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• 제21권1호
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• pp.87-99
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• 2000

Objectives : This is the experimetal paper to evaluate and compare the effects of Bosimgunbitang(補心健脾湯) with those of Jungjungamiyijintang(正傳加味二陳湯) on contraction of isolated organs, anti-ulcer, secretion of gastric juice, secretion of gastrin in serum, transport ability of intestine, analgesic effect and sedative effect Methods : We used mice and rats administered with the extract of the above herbs. Results: Bosimgunbitang and jungjungamiijintang showed the inhibitory effect on the smooth muscle contraction of the isolated ileum induced by acethylcholine chloride and barium chloride in mice. transport ability of intestine. Bosimgunbitang and jungjungamiijintang showed the inhibitory effect on the contraction of the fundus-strip induced by acethylcholine chloride and barium chloride in rats. The preventive effect on pyloric ulcer, indomethacin induced ulcer and ethanol-HCl induced ulcer bf mice was significant. The inhibitory effect of Bosimgunbitang on gastric free acidity, total acidity in Shay rats was significant. The inhibitory effect of on gastrin secretion in serum was significant after only 1 hour when the Bosimgunbitang and jungjungamiijintang was administered. The promoting effect of the jungjungamiijintang on the transport ability of small intestine was significant in the high concentration. The promoting effect of the Bosimgunbitang and jungjungamiijintang on the transport ability of large intestine was significant. The analgesic and the sedative effect were recognized. It meaned that Bosimgunbitang and jungjungamiijintang effected on the C.N.S.. Conclusion : Bosimgunbitang and jungjungamiijintang have the inhibitory effect on the smooth muscle abnormal contraction of the isolated ileum and the anti-ulcer effect to prevent, secretion of gastric juice and gastrin in serum. And they also have to increase a transport ability of intestine, analgesic effect and sedative effect. Jungjungamiijintang especially is eminent for analgesic effect while Bosimgunbitang has excellent sedative effect.

• 한국지반공학회지:지반
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• 제12권3호
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• pp.109-126
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• 1996

이 연구에서 사용된 화학제는 NaCl이다. NaCl과 모래-벤토나이트 혼합물이 각기 다른 혼합률로 배합되어 삼축 압축 시험을 하였다(5, 10, 15%). 탄성계수와 점착력, 그리고 내부 마찰각이 구속 응력과 NaCl의 함수로 얻었다. 이로부터 구한 강도 정수를 근거로 하여 응력-변형률-강도의 거동 특성을 화학액의 농도함수로 residual flow procedure(REP)에 연결하였다. RFP와 함께 유한요소법을 이용한 사면안정 해석 프로그램을 개발하여 안전율을 구하였으며 강도정수를 화학용액의 농도함수로 요소방정식에 넣어구한 안전율을 비교하였다. 이로써 화학용액이 흙제방의 안정성에 미치는 영향을 분석하였다.

• 사상체질의학회지
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• 제9권2호
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• pp.187-201
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• 1997

An experimental study was done to examine the effects of Dokwhaljiwhang-tang on gastro-intestinal track and central nervous system and were undertaken by being carried out with rat. The following results have been obtained ; 1. Dokwhaljiwhang-tang showed to have an inhibitory effect on the smooth muscle contraction of the isolated ileum by acetylcholene chloride and barium chloride. 2. Dokwhaljiwhang-tang showed to have an inhibitory effect on the contraction of the gastric fundus-strip by acetylcholine chloride and barium chloride. 3. The preventive effect was recognized on the pylorus-ligated ulcer, by administration of Dokwhaljiwhang-tang. 4. The preventive effect was not recognized on the indomethacine -induced ulcer, by administration of Dokwhaljiwhang-tang. 5. The inhibitory effects on the secretion gastric juice, free acidity were recognized, by administration of Dokwhaljiwhang-tang 6. The transport ability in the small intestine was increased, by administration of Dokwhaljiwhang-tang. 7. The transport ability in the large intestine was increased, by administration of Dokwhaljiwhang-tang. 8. The analgesic effect was recognized, by administration of Dokwhaljiwhang-tang. 9. The effect of sleeping time was not recognized, by administration of Dokwhaljiwhang-tang. according to the results, it is considered that Dokwhaljiwhang-tang has effects of gastric ulcer, chronic gastritis,hyper-acidity, gastroptosis such as abdominal discomfort, gastric acid, indigestion and anorexia.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1727-1732
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• 2017

Pyroprocessing is an alternative method of reprocessing spent fuel, usually involving the dissolving spent fuel in a molten salt media. The National Nuclear Laboratory designed, built, and commissioned a molten salt dynamics rig to investigate the transfer characteristics of molten lithium chloride-potassium chloride eutectic salt. The efficacy and flow characteristics of a high-temperature centrifugal pump and argon gas lift were obtained for pumping the molten salt at temperatures up to $500^{\circ}C$. The rig design proved suitable on an industrial scale and transfer methods appropriate for use in future molten salt systems. Corrosion within the rig was managed, and melting techniques were optimized to reduce stresses on the rig. The results obtained improve the understanding of molten salt transport dynamics, materials, and engineering design issues and support the industrialization of molten salts pyroprocessing.

• Corrosion Science and Technology
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• 제4권5호
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• pp.171-177
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• 2005

A comprehensive framework for numerical simulation of time-dependent performance change of reinforced concrete (RC) structures subjected to chloride attack is presented in this paper. The system is composed of simplified computational models for transport of moisture and chloride ions in concrete pore structure and crack, corrosion of reinforcement in concrete and mechanical behavior of RC member with reinforcement corrosion. Service-life of RC structures under various conditions is calculated.

• Computers and Concrete
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• 제3권6호
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• pp.401-422
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• 2006

A multi-species model based on the Nernst-Planck equation has been developed by using a finite volume method. The model makes it possible to simulate transport due to an electrical field or by diffusion and to predict chloride penetration through water saturated concrete. The model is used in this paper to assess and analyse chloride diffusion coefficients and chloride binding isotherms. The experimental assessment of the effective chloride diffusion coefficient consists in measuring the chloride penetration depth by using a colorimetric method. The effective diffusion coefficient determined numerically allows to correctly reproduce the chloride penetration depth measured experimentally. Then, a new approach for the determination of chloride binding, based on non-steady state diffusion tests, is proposed. The binding isotherm is identified by a numerical inverse method from a single experimental total chloride concentration profile obtained at a given exposure time and from Freundlich's formula. In order to determine the initial pore solution composition (required as initial conditions for the model), the method of Taylor that describes the release of alkalis from cement and alkali sorption by the hydration products is used here. Finally, with these input data, prediction of total and water-soluble chloride concentration profiles has been performed. The method is validated by comparing the results of numerical simulations to experimental results obtained on various types of concretes and under different exposure conditions.

• 한국건설순환자원학회논문집
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• 제3권1호
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• pp.22-33
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• 2015

Chloride ions in RC (Reinforced Concrete) structures can cause very severe corrosion in reinforcement steel. It is generally informed that chloride penetration can be considerably accelerated by enlarged chloride diffusion due to cracks. These cracks play a role in main routes through which chloride ions penetrate into the concrete, and also lead to steel corrosion in RC structures exposed to chloride attack, such as port and ocean structures. In this paper, field survey including evaluation of crack and chloride concentration distribution in concrete is performed to investigate an effect of crack on chloride diffusion. The service life of cracked concrete exposed to the marine environmental condition is estimated considering the crack effect on chloride diffusion. For this purpose, diffusion coefficients in cracked concrete are obtained based on the field survey. Using the relationship between diffusion coefficients in the cracked concrete and the crack widths, service life of the cracked concrete is predicted in a probabilistic framework. A bimodal distribution with two peaks, consisting of a weighted sum of two normal distributions is introduced to describe chloride diffusion of the concrete wharf with crack.