• 한국건축시공학회지
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• 제19권6호
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• pp.503-510
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• 2019

최근 RC 구조물의 건설기술에서는 콘크리트의 크리프에 대한 검토가 이루어져야 한다. 본 연구에서는 콘크리트의 크리프 예측 및 국내 건설현장의 크리프 결과에 영향을 미치는 요인을 검토했다. 크리프 테스트 기간이 길고 압축 강도가 높을수록 크리프 예측 정확도가 높아졌다. 경화 온도가 높을수록 콘크리트의 초기 강도가 높아지지만 크리프 계수의 차이는 시간이 지남에 따라 증가했다. 국내 건설현장 및 실험실에서의 크리프 평가 결과를 기반으로 ACI-209모델을 보완하는 수정 된 예측 모델을 제안했다. 일반~고강도 콘크리트를 사용한 실제 부재의 크리프 예측에서는 테스트 기간과 온도를 정확하게 고려해야한다.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1181-1181
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• 2001

Robinson with ${coworkers}^{1}$ have introduced two-state outer-neighbor bonding model to explain the anomalies of water. The studies on the properties of water as a function of temperature and pressure revealed that, unlike other ideas, all $H_2O$ molecules in liquid are tetrabonded. On the average they are forming two different bonding types. One type is the regular tetrahedral water-water bonding similar to that found in the ordinary ice Ih, whereas the other is a more dense nonregular tetrahedral bonding similar to that appearing in the ice II. The transformation between these two bonding forms is evidenced by FT-NIR experiment. The FT-NIR measurements were done for liquid water in the temperature range from $20^{\circ}C$ up to $80^{\circ}C$ in a wide extent of frequencies: 12 000 - 4000 $cm^{-1}$ /. Temperature dependent variations in the volume fraction of these two structures are directly related to the spectral changes. The absorbance variations are explored by means of the two-dimensional correlation spectroscopy (2DCOS), principal component analysis (PCA), curve fitting and second derivatives. The presence of the isosbestic points in a range of the combination and overtone transitions indicates that the experimental spectra are a superposition of two temperature independent components. One component of diminishing intensity with temperature increase, is assigned to a stronger hydrogen bonds occurred in the Ih type, whereas the second component showing an opposite behavior, one can attribute to a weaker H-bonds characteristic for the II type. The understanding of the hydrogen bonding network in the liquid water is very important in interpretation of the interaction between water and protein chain. The two-state model of water surrounding the protein surface could advance an understanding of the hydration process.

• 콘크리트학회논문집
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• 제19권5호
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• pp.613-621
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• 2007

내구성에 대한 중요성이 부각됨에 따라, 주요 열화현상인 탄산화에 대한 연구가 많이 진행되고 있다. 그러나 탄산화에 대한 연구는 주로 탄산화 깊이의 도출에 국한하고 있으며 경화된 콘크리트를 가정하므로 실제적인 탄산화 거동과는 많은 차이를 보이고 있다. 강재와는 다르게 콘크리트는 공극률과 내부의 수화물의 거동이 매우 중요한데, 탄산화 진행에 따라 초기재령에서 결정되어지는 거동 (공극률 및 수화물)이 다르게 변화한다. 열화 물질의 이동은 주로 콘크리트의 공극률 및 포화도에 의존하므로, 탄산화 후의 거동 평가는 장기열화해석 및 복합열화해석 등에 고려되는 것이 바람직하다. 공극률의 경우, 변화된 공극률이 고려되지 않으면 확산계수의 감소가 구현될 수 없으며 이에 따라 과다한 탄산화 해석을 야기하게 된다. 한편 수화물, 특히 수산화칼슘의 잔존량 평가는 탄산화 깊이의 평가 및 내부 공극수의 특성 변화를 결정하기도 하며, 복합열화에서 발생하는 고정화 염화물량에 큰 영향을 주게 된다. 그러므로 실내 실험들을 통한 공극률 및 수화물 분석은 최근들어 탄산화에 대해서도 많이 적용되고 있다. 본 연구는 미세 관측 실험을 통하여, 탄산화 전후의 공극률 분포 변화, 수화물 거동의 변화를 실험적으로 수행하였다. 공극률 측정으로는 MIP 실험을, 수화물 변화에서는 TGA 실험을 수행하였으며, 기존의 해석 모델인 다상복합수화발열모델 및 미세 공극 구조 형성모델을 개선하여 각각의 탄산화 이후의 공극률 변화 및 수화물 변화를 개발하였다. 개발된 각각의 모델의 결과는 탄산화 전후의 공극률 및 수화물의 변화를 잘 예측하였으며, 탄산화 이후의 열화현상 등에 기초적으로 사용될 수 있을 것으로 평가되었다.

• 한국응용과학기술학회지
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• 제17권1호
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• pp.43-48
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• 2000

Drug delivery system(DDS) applied to various fields, such as medicine, cosmetics, agriculture and necessities of life. Among these application fields, DDS is often used as the method of drug dosage into the epidermic skin. We investigated characters of transdermal therapeutic system(TTS) and the skin permeability of that with applying DDS. Chitosan was selected as material of TTS. We investigated the permeation of chitosan ointment containing drug in rat skin using horizontal membrane cell model. Permeation properties of materials were investigated for water-soluble drug such as riboflavin in vitro. We used glycerin, PEG 600 and oleic acid as enhancers. Since dermis has more content water(hydration) than the stratum corneum, skin permeation rate at steady state was highly influenced when glycerin was used in water-soluble drug. The permeation rate of content enhancer and drug was found to be faster than that of content water-soluble drug only. These results showed that skin permeation rate of drug across the composite was manly dependent on the property of ointment base and drug. Proper selection of the polymeric materials which resemble and enhance properties of the delivering drug was found to be important in controlling the skin permeation rate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.269-274
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• 1999

Various method have been developed for mass concrete structures to reduce the temperature increase of concrete mass due to exothermic hydration reactions of concrete compounds and thereby to avoid thermal cracks. One of the methods widely acceptable for practical use is pipe cooling, in which cooling is achieved by circulating cold water through thin-wall steel pipes embedded in the concrete. A numerical simulation was performed to investigate the effectiveness of pipe cooling. A three-dimensional finite element method was proposed to analyse the transient three-dimensional heat transfer between the hardening concrete and the cooling water in pipe and to predict the stress development during the curing process. The effects of the cement type and content and the environment were taken into consideration by the heat generation rate and the boundary conditions, respectively. In order to test the validity of the numerical simulation, a model RC structure with pipe cooling was constructed and the time-dependent temperature and stress distributions within the structure as well as the variation of the temperature of cooling water along the pipe were measured. The results of the simulation agreed well the experimental measurements. The results of this study have important implications for the optimal design of the cooling pipe layout and for the estimation of thermal stress in order to eliminate thermal cracks.

• Computers and Concrete
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• 제12권1호
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• pp.53-64
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• 2013

The curing temperature is known to influence the rate of mechanical properties development of early age concrete. In realistic sites the temperature of concrete is not isothermal $20^{\circ}C$, so the paper measured adiabatic temperature increases of four different concretes to understand heat emission during hydration at early age. The temperature-matching curing schedule in accordance with adiabatic temperature increase is adopted to simulate the situation in real massive concrete. The specimens under temperature-matching curing are subjected to realistic temperature for first few days as well as adiabatic condition. The mechanical properties including compressive strength, splitting strength and modulus of elasticity of concretes cured under both temperature-matching curing and isothermal $20^{\circ}C$ curing are investigated. The results denote that comparing temperature-matching curing with isothermal $20^{\circ}C$ curing, the early age concretes mechanical properties are obviously improved, but the later mechanical properties of concretes with pure Portland and containing silica fume are decreased a little and still increased for concretes containing fly ash and slag. On this basement using an equivalent age approach evaluates mechanical properties of early age concrete in real structures, the model parameters are defined by the compressive strength test, and can predict the compressive strength, splitting strength and elasticity modulus through measuring or calculating by finite element method the concreted temperature at early age, and the method is valid, which is applied in a concrete wall for evaluation of crack risking.

• Computers and Concrete
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• 제15권4호
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• pp.589-606
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• 2015

It is well-documented that the major deterioration of coastal RC structures is chloride-induced corrosion. Therefore, regional investigations are necessary for durability based design and evaluation of the proposed service life prdiction models. In this paper, four reinforced concrete jetties exposed to severe marine environment were monitored to assess the long term chloride penetration at 6 months to 96 months. Also, some accelerated durability tests were performed on standard samples in laboratory. As a result, two time-dependent equations are proposed for basic parameters of chloride diffusion into concrete and then the corrosion initiation time is estimated by a developed probabilistic service life model Also, two famous service life prediction models are compared using chloride profiles obtained from structures after about 40 years in the tidal exposure conditions. The results confirm that the influence of concrete quality on diffusion coefficients is related to the concrete pore structure and the time dependence is due to chemical reactions of sea water ions with hydration products which lead a reduction in pore structure. Also, proper attention to the durability properties of concrete may extend the service life of marine structures greater than fifty years, even in harsh environments.

• Journal of Pharmaceutical Investigation
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• 제28권1호
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• pp.43-50
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• 1998

Niosomes are vesicles formed from synthetic non-ionic surfactants, offering an alternative to chemically unstable and expensive liposomes as a drug carrier. Non-ionic surfactant and cholesterol mixture film leads to the formation of vesicular system by hydration with sonication method. The formation of niosome was ascertained by negative staining of TEM. The entrapment efficiency of niosomal suspension was gradually increased with increasing the ratio of cholesterol to surfactant. It was found that the niosome with 6 : 4 (polyoxyethylene 2-cetyl ether: cholesterol) ratio was more stable than those with other ratios. The topical application of acyclovir(ACV) in the treatment of herpes simplex virus type 1(HSV-1) skin disease has a long history. There are an increasing number of reports, however, in which topical ACV therapy is not as effective as oral administration. Lack of efficacy with topical ACV has been hypothesized to reflect the inadequate delivery of drug to the skin. We investigated the permeation of niosome containing $[^{3}H]ACV$ in hairless mouse skin using Franz diffusion cell model. Permeation coefficient(P) of aqueous ACV was $6.7{\times}10^{-4}\;(cm/hr)$ and that of ACV in niosome was $23.4{\times}10^{-4}\;(cm/hr)$, suggesting about 3.5 times increase in the transdermal permeation.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.1-7
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• 2011

PEM 연료전지에 있어서 수분의 균형이 연료전지의 시스템 성능에 현저한 영향을 미친다. 그래서 수분 균형은 가장 중요한 요소 중의 일부가 되었으며, 이에 관한 연구가 광범위하게 이루어지고 있다. 적절한 수분 균형을 유지하기 위해서는 적당한 멤브레인 수화작용(membrane hydration)이 필요하며, 반대로 촉매층(catalyst layer)에서의 익수(water flooding)현상이 없어져야 한다. 따라서 이와 같은 동적 상태에서 PEM 연료전지 내의 수분 균형을 유지하기 위해서는, 고도의 동적 수분 조정 기술이 확보되어야 한다. 현재의 연구는 이러한 특성을 고려하여 PEM 연료전지에서 동적부하 상태에서의 수분 이동에 관한 일차원 해석 모델에 관한 것이다. 금번 모델링의 결과, 양극촉매층(CCL, cathode catalystlayer)에서의 수분 상태는 거의 포화 단계에 이르고 있음을 보여주고 있으며, 이 모델링은 연료전지가 작동되는 동안의 CCL에 나타나는 수분의 양상을 예측하는데 활용될 수 있다. 본 논문에서는 수분 이동 모델이 국제규격에 따라 다양한 수송기관이 가동될 때, 동적부하 상태에서 서로 다른 차이점을 발견하기 위한 시뮬레이션 결과에 초점이 맞추어져 있다. 이 모델링을 적용한 결과, 수분 포화도가 상태에 따라 상이하게 나타남을 알 수 있었고, 또한 정적 수분 조절 요소에 따라 최적 상태가 모든 동적 분포에 따라 달라짐을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.230-235
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• 1992

The conformational analysis has been done for catecholamines (dopamine, norepinephrine, and epinephrine) in the cationic and di-anionic states. The species responsible for adsorption on silver metal surface is anionic deprotonated at hydroxyl groups of catechol moiety, i.e., di-anionic states of catecholamines. This was deduced from Fourier-transform Raman spectra of sodium salts of catecholamines. High resolution proton NMR (400 MHz) spectra of catecholamines in basic and neutral $D_2O$ solution show that the conformations of norepinephrine and epinephrine in the di-anionic states are preferred in gauche, but not for dopamine in the di-anionic state. However the energy difference between trans and gauche of catecholamines in the protonated cationic states is small enough to rotate freely through C-C bond in ethylamine moiety. The conformational calculations using an empirical potential function and the hydration shell model (a program CONBIO) show consistent with above experimental results. The calculations suggest that the species of catecholamines adsorbed on silver metal surface would be in favor of the gauche conformations.