• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.677-682
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• 2001

In this study, a method to evaluate diffusion coefficient of chloride ion in cracked concrete is proposed. For cracked concrete having either anisotropic or isotropic crack network, each crack of saturated concrete is considered as a V shape crack, and an effective diffusion coefficient is expressed with diffusion coefficients of cracked part and noncracked part and a so-called crack spacing factor. A comparison with experimental results shows that the diffusion coefficient for cracked concrete is accurately predicted by the effective diffusion coefficient. Prediction results also show that the cracks in concrete markedly change the diffusion properties and accelerate penetration of drifting species. The method in this paper can be effectively used to consider the effect of cracks on concrete diffusion coefficient of cracked concrete.

• 한국기계가공학회지
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• 제19권10호
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• pp.8-15
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• 2020

The diffusion cell method is the main technique employed for the in vitro diffusion test of transdermal drug delivery preparations. Most existing transdermal diffusion devices use a water bath heating structure and direct current motor magnetic stirrer. However, these devices are confronted with problems, such as large volume, incompatible vertical and horizontal diffusion cells, few diffusion cell sets, and poor reliability. To overcome these deficiencies, the system adopts a dry heating method and uses a rotating magnetic field generated by the electromagnetic stirrer to drive the magnetic stirrer. Accordingly, the resulting device is characterized by a simple structure and small volume, convenient operation, compatible vertical and horizontal diffusion cells, and numerous diffusion cell sets. The reliability and practicability of the system is verified by the in vitro percutaneous permeability test of the bisoprolol patch.

• 한국안전학회지
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• 제16권4호
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• pp.74-81
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• 2001

A direct numerical simulation (DNS) was applied to nonpremixed counter-flow diffusion flames between oxidizer and fuel ducts. The objective of this study is to evaluate the numerical method for simulation of axisymmetric counterflow diffusion flames. Effects of computational domain size and grid size were scrutinized, and then the method was applied to air-methane diffusion flames. The results at zero gravity conditions were in good agreement with those obtained by the one-dimension flame code OPPDIF. It was confirmed thai the numerical method is applicable to the diffusion flames at the normal gravity conditions since the results clearly showed the effects of buoyancy and velocity ratio.

• 한국광학회지
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• 제2권3호
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• pp.149-152
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• 1991

리튬나이오베이트 결정에 Ti를 열확산시켜 광도파로를 만드는 방법에서 문제가 되는 out-diffusion(삼출) 문제를 해결하는 방안으로 확산과정 이전에 $SiO_2$ 박막을 시료 위해 입히고 Ti을 열확산시켜 광도파로를 제조하는 방법을 제안하였으며, 기존의 방법에 의해서 만들어진 광도파로와 본 연구의 방법에 의해서 만든 광도파로의 근시야상(near field pattern)을 비교하였다.

• 대한전기학회논문지:전력기술부문A
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• 제51권12호
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• pp.630-637
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• 2002

This paper proposed a new diffusion model considering DSM rebate program's support conditions. The proposed method used some aspects of the rebate program such as support qualifications, annual support volume, and support level per appliance as following : The support qualifications were limited as the consumer which can get the rebate program's benefit, the annual support volume was constrained as the fixing budget and the support level per appliance was considered by high-efficient appliance actuality price. This paper also proposed a new method that used neural network as its parameter estimation moth[,4 for the diffusion model. The diffusion model and its parameter estimation method are expected to be able to analyze the diffusion characteristics of high-efficient appliance through the rebate program and the effects of rebate program's support conditions. Also, these will be able to evaluate the impacts and to analyze the cost-effectiveness of Energy Efficiency Demand-Side Management(EEDSM) resources. The case study is performed on the high-efficient lighting appliance rebate program of Korea by using the suggested diffusion model and estimation method and thus verified its validity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3073-3078
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• 2008

In this study to find out the amount of soot, LII method, which utilizes a laser, was used in laminar diffusion flame and based upon the temperature and soot measured from the turbulent Diesel diffusion flame in the constant-volume chamber using the two-color method. Through these experiments, we could know that the LII signal is generally proportional to the soot amount in a laminar diffusion flame. And we could acquire the temperature and soot using the two-color method in a turbulent Diesel diffusion flame effectively. In addition to, this experiment revealed that the KL factor was high on parts of the chamber where the temperature dropped. On the other hand, the KL factor was low where the temperature increased rapidly. Also, it was possible to measure the highest temperature of a turbulent Diesel diffusion flame is approximately 2300K.

• 한국표면공학회지
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• 제49권1호
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• pp.104-109
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• 2016

Graphite's thermal stability facilitates its widespread use as crucibles and molds in high temperatures processes. However, carbon atoms can be rather easily detached from pores and outer surfaces of the graphite due to the weak molecular force of the c axis of graphites. Detached carbon atoms are known to become a source of dust during fabrication processes, eventually lowering the effective yield of products. As an effort to reduce these problems of dust scattering, we have fabricated SiC composites by employing Si vapor infiltration method into the pores of graphites. In order to understand the diffusion process of the Si vapor infiltration, Si and C atomic percentages of fabricated SiC composites are carefully measured and the diffusion law is used to estimate the diffusion coefficient of Si vapor. A quadratic equation is obtained from the experimental results using the least square method. Diffusion coefficient of Si vapor is estimated using this quadratic equation. The result shows that the diffusion length obtained through the Si vapor infiltration method is about 10.7 times longer than that obtained using liquid Si and clearly demonstrates the usefulness of the present method.

• 응용통계연구
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• 제28권5호
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• pp.895-906
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• 2015

확산모형은 입자의 운동현상과 금융자산의 미시적 가격변동을 설명하기 위하여 사용되는 수리적 모형이다. 확산모형의 추정방법에 관한 논의는 다양한 분야에서 이루어져 왔다. 통계학적 관점에서 우도적 방법에 기반한 확산모형의 추정방법을 개발하려는 시도가 계속되어 왔다. 이산시간 간격으로 관측된 자료를 이용하여 확산모형을 추정할 때 최대우도 추정법을 적용하기 위해서는 확산모형에 대한 전이확률 밀도함수를 구해야 한다. 본 연구에서는 확산모형의 전이확률밀도를 근사하기 위하여, 정규분포를 따르는 확률변수를 이용하여 브라운다리 확률과정에 대한 경로적분을 대체하는 방법을 제안하고, 그 수치적 성질을 다른 방법들과 비교한다.

• 한국콘텐츠학회논문지
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• 제7권2호
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• pp.21-29
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• 2007

이방성 확산은 영상 분할 분야에서 광범위하게 사용되는 방식이다. 기존의 전통적인 이방성 확산 [1]-[6]에서는 이미지의 대각선 방향을 고려하지 않고 4 방향(동, 서, 남, 북)을 주로 이용하였다. 전통적인 이방성 확산(Diffusion)을 이용한 영상 분할은 확산이 반복될수록 윤곽선 정보를 적절히 유지 못하거나 잡음을 제거하지 못함으로써 웨터쉐드(Watershed) 알고리즘을 적용하는 경우 과다 분할을 피할 수 없다는 단점을 갖고 있다. 본 논문에서는 전통적인 이방성 확산의 이러한 단점을 보완하기 위하여 대각선 방향에 기반한 새로운 이방성 확산을 제안하고, 워터쉐드를 이용한 영상 분할 방법을 적용하였다. 실험 결과 본 논문에서 제안한 대각선 방향을 포함한 이방성 확산을 적용할 경우 기존의 방법과 비교하여 약 2배의 속도 향상을 가져왔으며, Circle 이미지의 경우 약 $0.45{\sim}2.33(dB)$정도 성능 향상된 화질을 보였다. 또한 기존의 방법보다 과다 분할이 줄어들고 영상이 매우 효과적으로 분할됨을 확인하였다.

• Journal of applied mathematics & informatics
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• 제32권1_2호
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• pp.185-201
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• 2014

In this paper, we construct a numerical method to solve singularly perturbed one-dimensional parabolic convection-diffusion problems. We use Euler method with uniform step size for temporal discretization and exponential-spline scheme on spatial uniform mesh of Shishkin type for full discretization. We show that the resulting method is uniformly convergent with respect to diffusion parameter. An extensive amount of analysis has been carried out to prove the uniform convergence with respect to the singular perturbation parameter. The obtained numerical results show that the method is efficient, stable and reliable for solving convection-diffusion problem accurately even involving diffusion parameter.