Preliminary

Nak Kyu Kim,Chung-Kyun Park,Jae-Kwang Lee,Seonggyu Choi,Jang-Soon Kwon 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

The deep geological disposal system is aimed to permanently isolate the high-level radioactive waste from the biosphere through a multi-barrier system composed of engineered and natural barriers. The buffer material used for the engineered barrier should have the performance to prevent and retard the migration of radionuclides to the outside of the deep disposal facility when radionuclides are released from a disposal canister by infiltration of groundwater after a long period of time. When the hydraulic conductivity of compacted bentonite is sufficiently low, the migration of radionuclides released into the surrounding rock can be significantly reduced since they are sorbed to bentonite during the diffusion process. Therefore, an investigation on diffusion of radionuclides in compacted bentonite is a fundamental task to obtain essential data for the safety assessment of the deep geological disposal system. The migration of radionuclides by diffusion can be evaluated by diffusion coefficient. In order to obtain the apparent diffusion coefficients of Sr, Sm, and Eu in compacted Ca-bentonite (1.6 g/cm3) a through-diffusion experiment have been carrying out. A cylindrical apparatus consists of a source cell with an appropriate concentration of radionuclides and diffusion cell filled with radionuclide free solution where the concentration is gradually increased by diffusion of radionuclides. The compacted bentonite was installed between the both cells. The sample used for the experiment is a Ca-type bentonite named Bentonil-WRK, and the diffusion experiment was performed under an oxidizing condition using a synthetic groundwater simulating KURT groundwater composition. The diffusion experiment will be terminated when an increasing rate of concentration of nuclides in the diffusion cell becomes constant over time. The concentration change with regard to the geochemical characteristic of the nuclide may appear to be apparently slow.In this study, the experimental results of the through-diffusion test of Sr, Sm, and Eu in the initial stage (~4 months) were presented. Through the results of the initial stage, the period of the through-diffusion experiment can be rearranged and also it is expected that the initial results provide the qualitative and quantitative diffusion properties of each nuclide.

Modeling of ion diffusion coefficient in saturated concrete

Xiao-Bao Zuo,Wei Sun,Cheng Yu,Xu-Rong Wan 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.5

This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test,have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

SmCo5 및 Sm₂Co17금속간화합물중에 Sm의 확산계수

송창빈 公州大學校工科大學生産技術硏究所 1997 論文集 Vol.5 No.-

For the purpose of obtaining basic information on the reduction-diffusion process, diffusion experiments were carried out for the Sm-Co binary system at 1000, 1050, 1100, and 1200℃. Sm was made diffuse into Co by containing a vapor from a molten Sm-Ca alloy with a polished surface of a Co-block. The use of the Sm-containing vapor was effective to supress the formation of a Co-containing melt on the surface of the Co block. The formation of the Co-containing melt hindered the uniform growth of diffusion layers and blurred the time of initiation of the diffusion. Though several intermetallic compounds are present in the Sm-Co binary system only SmCo5 and Sm₂Co17 phase were found to grow systematically. Diffusion coefficients of Sm for the reactive diffusion in these phases at the respective temperatures were calculated from the relationships between the diffusion layer thickness and the diffusion time by utilizing Sm concentrations at the boundaries of the phases which were read from Sm-Co binary phase diagrams. The diffusion coefficient of SmCo5 has been found at least thress times larger than that in Sm₂Co17 at each temperature of this study.

인체의 위 조직 시료에서 자기공명영상장치를 이용한 확산계수 측정에 대한 기초 연구

문치웅,최기승,양영일,장희경,은충기,Mun Chi-Woong,Choi, Ki-Sueng,Nana Roger,Hu, Xiaoping P.,Yang, Young-Il,Chang Hee-Kyung,Eun, Choong-Ki 대한의용생체공학회 2006 의공학회지 Vol.27 No.5

The aim of this study is to investigate the feasibility of ex vivo MR diffusion tensor imaging technique in order to observe the diffusion-contrast characteristics of human gastric tissues. On normal and pathologic gastric tissues, which have been fixed in a polycarbonate plastic tube filled with 10% formalin solution, laboratory made 3D diffusion tensor Turbo FLASH pulse sequence was used to obtain high resolution MR images with voxel size of $0.5{\times}0.5{\times}0.5mm^3\;using\;64{\times}32{\times}32mm^3$ field of view in conjunction with an acquisition matrix of $128{\times}64{\times}64$. Diffusion weighted- gradient pulses were employed with b values of 0 and $600s/mm^2$ in 6 orientations. The sequence was implemented on a clinical 3.0-T MRI scanner(Siemens, Erlangen, Germany) with a home-made quadrature-typed birdcage Tx/Rx rf coil for small specimen. Diffusion tensor values in each pixel were calculated using linear algebra and singular value decomposition(SVD) algorithm. Apparent diffusion coefficient(ADC) and fractional anisotropy(FA) map were also obtained from diffusion tensor data to compare pixel intensities between normal and abnormal gastric tissues. The processing software was developed by authors using Visual C++(Microsoft, WA, U.S.A.) and mathematical/statistical library of GNUwin32(Free Software Foundation). This study shows that 3D diffusion tensor Turbo FLASH sequence is useful to resolve fine micro-structures of gastric tissue and both ADC and FA values in normal gastric tissue are higher than those in abnormal tissue. Authors expect that this study also represents another possibility of gastric carcinoma detection by visualizing diffusion characteristics of proton spins in the gastric tissues.

LMC(Latex Modified Concrete)의 염소이온 확산 특성

박성기,원종필,박찬기,Park, Sung-Ki,Won, Jong-Pil,Park, Chan-Gi 한국농공학회 2008 한국농공학회논문집 Vol.50 No.4

It is most serious problem which is various occurs from the agricultural concrete structure and off shore concrete structure the problem which it comes to think is deterioration of the concrete which is caused with the corrosion of the reinforcing steel which is caused by with permeation of the water and the sea water. Specially the off shore concrete structure has been deteriorated by the steel reinforcement corrosion. The latex modified concrete(LMC) was adds latex in the plain concrete as the latex has increase the durability of concrete. This study were accomplished to the estimate the diffusion coefficient of LMC, and the time dependent constants of diffusion. The average chloride diffusion coefficient was estimated. Also, the average chloride diffusion coefficient was compared with diffusion coefficient test results of 28 curing days. The test results indicated that the average chloride diffusion coefficient could closely estimate the test results of the diffusion coefficient test results of 28 curing days.

An Electrochemical Evaluation on Relationship between Corrosion Resistance and Oxygen Diffusion Limiting Current Density of Anti-Corrosive paints

Kyung-Man Moon,Sung-Yul Lee,Yun-Hae Kim,Myung-Hoon Lee 한국마린엔지니어링학회 2009 한국마린엔지니어링학회 학술대회 논문집 Vol.2009 No.-

Relationship between corrosion current density and oxygen diffusion limiting current density or its diffusion coefficient were investigated with electrochemical methods such as measurements of corrosion potential, anodic and cathodic polarization curves etc. to five kinds of anti-corrosive paints including acryl, fluorine and epoxy resin series. it is supposed that there are considerably somewhat good relationships between corrosion current density and oxygen diffusion limiting current density or its diffusion coefficient for example, corrosion current density is decreased with decreasing of oxygen diffusion limiting current density or its diffusion coefficient. Consequently it is considered that corrosion resistance of anticorrosive paint can conveniently qualitatively be evaluated by measuring of oxygen diffusion limiting current density or its diffusion coefficient.

염해에 노출된 콘크리트의 내구수명 확보를 위한 최적 배합 도출에 대한 연구 - 유전자 알고리즘의 적용

권성준(Kwon Seung-Jun),이성칠(Lee Sung Chil) 대한토목학회 2010 대한토목학회논문집 A Vol.30 No.5A

콘크리트의 염화물 확산계수의 제어는 염해에 노출된 콘크리트 구조물의 내구수명 확보에 필수적이며, 이를 위해 많은 연구가 진행되어 왔다. 본 연구는 목표 내구수명을 만족하는 목표확산계수를 도출하고 유전자 알고리즘을 통하여, 최적배합을 도출하는데 있다. 이를 위하여, 동일한 골재 및 혼화재를 사용한 30개의 배합과 그에 따른 염화물 확산계수를 분석하였으며, 27개를 대상으로 확산계수 예측식을 도출하였다. 확산계수 예측식의 변수로는 물-결합재비, 단위 혼화재량(슬래그, 플라이 애쉬, 실리카퓸), 단위 시멘트량, 단위 잔골재 및 굵은 골재량을 포함하도록 하였으며 나머지 3개의 배합에 대하여 검증을 수행하였다. 최적 함수식은 27개의 배합에 대하여 평균 18.7%의 오차와 16.0%의 변동계수를 보이고 있었다. 주어진 3개의 확산계수에 대하여, 유전자 알고리즘을 통하여 도출된 배합은 0.3%~12.2%의 오차범위를 가지며 각각의 배합인지를 도출하였다. 최종적으로 서로 다른 내구성 설계변수(목표내구수명, 피복두께, 표면염화물량, 흔화재량)와 노출환경(온도 및 습도)을 가정하여 목표 확산계수를 도출하였으며, 이에 만족하는 최적화된 콘크리트 배합을 제안하였다. 본 연구에서는 유전자 알고리즘을 이용하여, 내구성 콘크리트 배합도출에 대한 적용성을 평가하였으며, 제안된 기법은 다양한 확산계수의 범위를 가지는 광범위한 자료구축을 통하여 개선될 것이다. A control of chloride diffusion coefficient is very essential for service life of reinforced concrete (RC) structures exposed to chloride attack so that much studies have been focused on this work. The purpose of this study is to derive the intended diffusion coefficient which satisfies intended service life and propose a technique for optimum concrete mixture through genetic algorithm(GA). For this study, 30 data with mixture proportions and related diffusion coefficients are analyzed. Utilizing 27 data, fitness function for diffusion coefficient is obtained with variables of water to binder ratio(W/B), weight of cement, mineral admixture(slag, flay ash, and silica fume), sand, and coarse aggregate. 3 data are used for verification of the results from GA. Average error from fitness function is observed to 18.7% for 27 data for diffusion coefficient with 16.0% of coefficient of variance. For the verification using 3 data, a range of error for mixture proportions through GA is evaluated to 0.3~9.3% in 3 given diffusion coefficients. Assuming the durability design parameters like intended service life, cover depth, surface chloride content, and replacement ratio of mineral admixture, target diffusion coefficient, where exterior conditions like relative humidity(R.H.) and temperature, is derived and optimum design mixtures for concrete are proposed. In this paper, applicability of GA is attempted for durability mixture design and the proposed technique would be improved with enhancement of comprehensive data set including wider range of diffusion coefficients.

Poly(ether)tailed Cobalt(Ⅱ)bipyridine 착물의 합성과 전기화학적 성질

김일광,한완수 목원대학교 자연과학연구소 1997 自然科學 硏究論文集 Vol.6 No.-

산화환원 반응 탐침제로, poly ether 꼬리가 결합된 Cobalt(Ⅱ)bipyridine 착물을 합성하였고, 이들 화합물이 느린 확산계수와 불균일 전자이동을 설명하였다. Co(bpy(ppgm)_2)_3-(CIO_4)_2에 전해질 LiCIO_4가 혼합된 neat 상태의 산화 반응에 대한 확산계수는 1.5×10^-15 ㎠/s 이었다. 이 화합물들의 불균일 전자이동 속도상수들은 확산계수와 관련이 있었다. 확산계수의 감소에 따라 속도상수(k)의 감소가 일어났다. 강한 이온쌍을 형성하는 ClO_4^-의 화합물은 약한 이온쌍을 형성하는 CF_3COO^- 화합물보다 확산계수가 훨씬 작았다. The synthesis of poly(ether)tailed bipyridine complex are redox reaction probes has advanced attempts to interpret very slow diffusion and heterogeneous electron transfer. Diffusion coefficients as low as 1.5×10^-15 ㎠/s have been observed for the oxidation of neat Co(bpy(ppgm)_2)_3-(CIO_4)_2 with LiCIO_4 electrolyte. Heterogeneous electron transfer rate constants of materials were found to vary with diffusion coefficient. The decrease in k as the diffusion coefficient decreases was actually caused by the decreasing D. Diffusion coefficient for compound of strong ion pairing anion(ClO_4^-) was much smaller than the diffusion coefficient for compound of weak ion pairing anion(CF_3COO^-).

폴리(에테르)사슬이 결합된 Cobalt(II)bipyridine 착물의 합성과 전기화학적 성질

김일광,전일철,Kim, II Kwang,Jun, II Chul,Murray, Royce W. 한국분석과학회 1996 분석과학 Vol.9 No.3

The synthesis of poly(ether)tailed bipyridine complex as redox reaction probes has advanced attempts to interpret very slow diffusion and heterogeneous electron transfer. Diffusion coefficients as low as $1.5{\times}10^{-15}cm^2/s$ have been observed for the oxidation of neat $Co(bpy(ppgm)_2)_{3^-}(ClO_4)_2$ with $LiClO_4$ electrolyte. Heterogeneous electron transfer rate constants of materials were found to vary with diffusion coefficient. The decrease in k as the diffusion coefficient decreases was actually caused by the decreasing D. Diffusion coefficient for compound of strong ion pairing anion($ClO{_4}^-$) was much smaller than the diffusion coefficient for compound of weak ion pairing anion($CF_3COO^-$). 산화환원반응 탐침제로, poly ether 꼬리가 결합된 Cobalt(II)bipyridine 착물을 합성 하였고, 이들 화합물의 느린 확산계수와 불균일 전자이동을 설명하였다. $Co(bpy(ppgm)_2)_{3^-}(ClO_4)_2$에 전해질 $LiClO_4$가 혼합된 neat 상태의 산화반응에 대한 확산계수는 $1.5{\times}10^{-15}cm^2/s$ 였다. 이 화합물들의 불균일 전자이동 속도상수들은 확산계수와 관련이 있었다. 확산계수의 감소에 따라 속도상수(k)의 감소가 일어났다. 강한 이온쌍을 형성하는 $ClO{_4}^-$의 화합물은 약한 이온 쌍을 형성하는 $CF_3COO^-$ 화합물보다 확산계수가 훨씬 작았다.

Study on Calculation of Diffusion Coefficient for Sublimation Diffusion of Disperse Dye Using Fourier Series

박건용 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3

The separation of variables to solve the diffusion equation and the Fourier series to represent the initial distributionwere applied to the study on a reliable method for measuring the diffusion coefficient. A disperse dye in paste was treated at170-190 °C for various times in a semi-infinite medium using a film roll method. As time increased, the concentrationdistribution approached linear, and a approximate steady state condition was set up. The linear regression line was drawn bylinear regression analysis and the converted straight line passing through the mean dye concentration of the first layer wasdrawn by obtaining the diffusion length and the surface concentration with which the diffusion coefficients were calculated. The correlation coefficients of the Arrhenius plots for the diffusion coefficients obtained from the converted straight line andthe linear regression line were 0.9999 and 0.9983, respectively. The reliability of the diffusion coefficients calculated by theequation derived from the Fourier series can be proved by the good linearity of the Arrhenius plots. The activation energiesobtained from the converted straight line and the linear regression line were 29.2 and 30.8 kcal/mol, respectively.