• 한국컴퓨터산업교육학회:학술대회논문집
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• 한국컴퓨터산업교육학회 2003년도 제4회 종합학술대회 논문집
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• pp.87-94
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• 2003

Anisotropic diffusion is a selective smoothing technique that promotes smoothing within a region instead of smoothing across boundaries. In anisotropic diffusion, the rate of smoothing is controlled by the local value of the diffusion coefficient chosen to be a function of the local image gradient magnitude. El-Fallah and Gary E. Ford represented the image as a surface and proved that setting the inhomogeneous diffusion coefficient equal to the inverse of the magnitude of the surface normal results in surface evolving speed that is proportional to the mean curvature of the image surface. This model has the advantage of having the mean curvature diffusion (MCD) render invariant magnitude, thereby preserving structure and locality. In this paper, the proposed MCD model efficiently reduces diffusion coefficient at the thin edges using the smoothness of the surface.

• Investigative Magnetic Resonance Imaging
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• 제11권2호
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• pp.110-118
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• 2007

목적: 확산텐서자기공명영상(DT-MRI: Diffusion Tensor Image)을 이용하여 확산의 주축을 구성하는 세 성분에 대한 고유치 (eigefvalue)의 영상을 구현해 보고자 하였다. 대상 및 방법: 고유치 영상을 구현하기 위해서 3.0 테슬러 MRI(Magnetic Resonance Imaging)를 이용하여 확산텐서영상을 얻었으며, Moore-Penrose pseudo-inverse 방법과 SVD(single value decomposition) 방법을 이용하여 확산 주축을 계산하였다. 이 과정을 픽셀단위로 반복적으로 계산하여 새로운 확산 주축 영상들을 만들었으며, 이 확산 주축 영상들과 분할 비등방성 영상의 관계를 조사하였다. 결과: 확산텐서영상 기법으로 얻어진 확산텐서영상을 이용하여, 세 방향의 확산 주축에 대한 고유치 영상을 구성하였으며, 고유치 영상들과 분할 비등방성 영상을 함께 분석함으로써, 뇌의 해부학적 구조물에 따른 분할 비등방성 값의 차이를 확인할 수 있었다. 또한, 확산 주축에 대한 고유치의 변화에 대한 컴퓨터 모의실험에서, 변화하는 고유치에 따른 분할 비등방성 값의 변동 추이를 알아볼 수 있었다. 그리고 확산 주축의 크기가 비등방성을 좌우하는 것이 아니라, 세 확산 주축의 조합으로 비등방성의 정도를 표현한다는 것을 확인할 수 있었다. 확산 주축 방향의 고유치들을 분리하여 영상화 함으로써, 뇌의 병변에 의한 비등방성의 변화의 원인이 확산 주축의 어떠한 변화에 의해 발생하는 것인지 확인할 수 있을 것으로 기대된다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.114-116
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• 2005

Natural attenuation has been actively studied and often selected as final clean-up process in remediation of contaminated ground-water and soil for the last decade. Accordingly, understanding of natural processes affecting the fate and transport of contaminants in the subsurface becomes important for a success of implementation of the natural remediation strategy, Contaminant advection and diffusion processes in the unsaturated zone are naturally related to environmental changes in the atmosphere. The atmospheric pressure changes affecting the transport of contaminants in the subsurface are investigated in this study. Moisture content, trichloroethylene (TCE) concentration, temperature, and pressure variations in the subsurface were measured for the July, August, November, and December 2001 at Picatinny Arsenal, New Jersey. These data were used for a one-phase flow and one-component transport model in simulating the soil-gas flow and accordingly the TCE transport in the subsurface in accordance with the atmosphere pressure variations at the surface. The soil-gas velocities during the sampling periods varied with a magnitude of $10^{-6}\;to\;10^{-7}\;m\;s^{-1}$ at land surface. The TCE advection fluxes at land surface were several orders of magnitude smaller than the TCE diffusion fluxes. A sensitivy analysis indicated that advection fluxes were more sensitive to changes in geo-environmental conditions compared to diffusion fluxes. Of all the parameters investigated in this study, moisture content has the most significant effect on TCE advection and diffusion fluxes.

• 한국자기공명학회논문지
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• 제16권2호
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• pp.122-132
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• 2012

The effects of the sample viscosity and volume on the convective flows induced by temperature gradient in PGSE-NMR self-diffusion measurements at high temperature have been investigated. The experimental results showed that the viscosity of the liquid sample strongly affects the magnitude of the convective flows as well as the diffusion coefficient itself. It was also found that the convective flows increase as the sample volume increase.

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2973-2977
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• 2011

It has been known that the inertial dynamics has a little effect on the reaction rate in solutions. In this work, however, we find that for diffusion-controlled reactions between a ligand and a receptor on the cell surface there is a noticeable inertial dynamic effect on the reaction rate. We estimate the magnitude of the inertial dynamic effect by comparing the approximate analytic results obtained with and without the inertial dynamic effect included. The magnitude of the inertial dynamic effect depends on the friction coefficient of the ligand as well as on the relative scale of the receptor size to the distance traveled by the ligand during its velocity relaxation time.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.90-94
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• 1998

Self diffusion coefficients of $^{67}$Co and impurity diffusion coefficients of $^{51}$Mn and $^{65}$Zn in single crystalline CoO have been measured by applying different radioactive isotopes simultaneously. To compare the residual activity method and the tracer sectioning method we analyzed our tracer diffusion experiments by using both methods simultaneously. According to our experimental results, the diffusion coefficients obtained from both methods are identical within experimental error, demonstrating the relibility of our experimental procedures. The diffusion coefficients of all the isotopes obtained during these test experiments for the methodology are similar in magnitude and show similar dependences on oxygen partial pressure. These first observations indicate that impurity diffusion of Mn and Zn occur via a vacancy mechanism as known for self diffusion of cobalt.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.159-162
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• 2008

This paper presents a modified mean curvature diffusion filter to smooth speckle noise in images. Mean curvature diffusion filter has already shown good results in reducing noise in images while preserving fine details. In the mean curvature diffusion, the rate of smoothing is controlled by the local value of the diffusion coefficient chosen to be a function of the local image gradient magnitude. In this paper, the diffusion coefficient is modified to be controlled adaptively by local image surface slope and heterogeneity. The local surface slope contributes to preserving details (e.g.edges) in image and the local surface heterogeneity helps the smoothing filter consider the amount of noise in both edge and non-edge area. The proposed filter's performance is demonstrated by quantitative experiments using speckle noised aerial image and TerraSAR-X satellite image.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.

• Ocean and Polar Research
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• 제30권4호
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• pp.537-543
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• 2008

The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun $4^{th}$ dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two.

• Archives of Pharmacal Research
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• 제16권3호
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• pp.191-195
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• 1993

We investigated the effects of n-alkanols on the range and rate of the lateral diffusion of 1, 3-di(1-pyrenyl)propane in the model membranes of total phospholipid fraction extracted from synaptosomal plasma membrane vesicles. n-Akanols increased the range and rate of the lateral diffusion of 1, 3-di(1-pyrenyl)propane in the bulk model membrane structures (inner + outer monolayers) and the potencies of n-alknols up to 1-nonanol increased by 1 order of magnitude as the carbon chain length increases by two carbon atoms. The cut-off phenomenon was reached at 1-decanol, where further icnrease in hydrocarbon length resulted in a decrease in the lateral diffusion. However, significant changes in the 1'/1 value were not observed by methanol (from 100 to 2500 mM), ethanol (from 25 to 800 mM), and 1-propanol (from 10 to 250 mM) over entire concentration.