• 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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.573-576
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• 2006

To predict service life of concrete structures exposed to chloride attack, surface chloride concentration, diffusion coefficient of chloride ion, and chloride corrosion threshold value in concrete, are used as important factors. of these, as the diffusion coefficient of chloride ion for concrete is strongly influenced by concrete quality and environmental conditions of structures and may significantly change the service life of structures, it is considered as the most important factor for service life prediction. The qualitative factors affecting the penetration and diffusion of chloride ion into concrete are water-binder(W/B) ratio, age, cement type and constituents, chloride ion concentration of given environment, wet and dry conditions, etc. In this paper the influence of cement type on the diffusion characteristics of chloride ion in concrete was investigated through the chloride ion diffusion test. For this purpose, the diffusion characteristics in concrete with cement type such as ordinary portland cement(OPC), binary blended cement(BBC), and ternary blended cement(TBC) were estimated for the concrete with W/B ratios of 32% and 38%, respectively. It was observed from the test that the difussion characteristics of BBC containing OPC and ground granulated blast-furnace slag was found to be most excellent of the cement type used in this study.

• 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.

• 한국기계가공학회지
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• 제18권7호
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• pp.71-76
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• 2019

The diffusion of the drug component of the inflammatory patch into the living tissue was analyzed by laser induced plasma spectroscopy (LIBS). Calcium element, which is a diffusion catalyst of the drug in the inflammatory analgesic patch, is transferred into the body through the diffusion process of the substance. The test pieces used in the experiment are pig skin tissues which are similar to human skin. As a result, the diffusion coefficient D of the calcium element was found to be average $8.24{\times}10^{-2}({\mu}m^2/s)$. Experimental results showed that the most influential factors on the diffusion of materials were temperature variables.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.491-495
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• 2015

This paper aims to provide some unique insights into the verification of organisational innovation diffusion through empirically identifying the major factors determining the level of organisational innovation diffusion. The paper presents a two-stage sequential mixed method analysis: structural equation modelling analysis and regression analysis. A questionnaire survey was administrated to a sample of 223 organisations operating in Saudi Arabia. The results suggest that participative culture and, technology availability and implementation would intensify organisational climate for innovation. The results revealed compelling evidence in support of the moderating role of technology on the relationship between country socio-culture and organisational climate for innovation. Equally important, organisational innovation characteristics could play a crucial role in the intention to adopt a particular innovation. Specifically, maintaining Saudi Arabian top management's status quo is an obstacle to organisational innovation diffusion. This paper expands and improves upon the current understanding of how organisational innovation diffusion, in particular the Project Management Office (PMO), can be accelerated. By focusing on the critical factors within the conceptual model, the paper depicts the crucial role of certain factors that could leverage improved organisational innovation diffusion outcomes.

• 스마트미디어저널
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• 제13권2호
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• pp.9-15
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• 2024

본 논문에서는 신용 예측에서 발생하는 불균형 문제를 해결하기 위해 Diffusion Multi-step Classifier(DMC)를 제안한다. DMC는 Diffusion Model을 통해 신용 예측 데이터의 연속적인 수치형 데이터들을 생성하고 생성된 데이터들을 Multi-step Classifier로 구분하는 것으로 범주형 데이터를 생성한다. DMC를 통해 기존의 데이터를 생성하는 다른 알고리즘보다 실제 데이터와 유사한 분포를 가지는 데이터를 생성할 수 있었다. 이렇게 생성된 데이터를 사용하여 실험을 진행하였을 때 연체를 예측할 확률이 20%이상 상승하였으며, 전체적으로 예측 정확성은 약 4%정도 상승하였다. 이러한 연구 결과는 실제 금융기관에 적용 시 연체율 감소와 수익 증가에 큰 기여를 할 수 있을것으로 예상된다.

• 한국세라믹학회지
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• 제18권2호
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• pp.79-82
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• 1981

SiC powder was heated in air over the temperature range of 1100-135$0^{\circ}C$. $\beta$-cristobalite was formed to cover the surfaces of SiC particles by the reaction: $SiC(s)+20_2(g)=SiO_2(s)+CO_2(g)$. It is assumed that the diffusion of oxygen ion through the formed surface layer of $\beta$-cristobalite controls the oxidation of the SiC particles. The diffusion coefficient of oxygen ion through the $\beta$-cristobalite layer was obtained as the following equation: $D=3.84{\times}10^{-17}$exp(-14.7/RT)

• International Journal of Automotive Technology
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• 제8권6호
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• pp.761-769
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• 2007

The configuration of the flow channel on a bipolar plate of a proton exchange membrane fuel cell(PEMFC) for efficient reactant supply has great influence on the performance of the fuel cell. Recent demand for higher energy density fuel cells requires an increase in current density at mid voltage range and a decrease in concentration overvoltage at high current density. Therefore, an interdigitated flow channel where mass transfer rate by convection through a gas diffusion layer is greater than the mass transfer by a diffusion mechanism through a gas diffusion layer was recently proposed. This study attempts to analyze the i-V performance, mass transfer and pressure drop in interdigitated flow channels by developing a fully three dimensional simulation model for PEMFC that can deal with anode and cathode flow together. The results indicate that the trade off between performance and pressure loss should be considered for efficient design of flow channels. Although the performance of the fuel cell with interdigitated flow is better than that with conventional flow channels due to a strong mass transfer rate by convection across a gas diffusion layer, there is also an increase in friction due to the strong convection through the porous diffusion layer accompanied by a larger pressure drop along the flow channel. It was evident that the proper selection of the ratio of channel and rib width under counter flow conditions in the fuel cell with interdigitated flow are necessary to optimize the interdigitated flow field design.

• 한국수소및신에너지학회논문집
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• 제25권4호
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• pp.386-392
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• 2014

The effective water management in a polymer electrolyte membrane fuel cell (PEMFC) is one of the key strategies for improving cell performance and durability. In this work, an ex situ measurement was carried out to understand the water droplet behavior on the surface of gas diffusion layer (GDL) as a fundamental study for establishing novel water management. For that purpose, simplified cell including one rib and two flow channels was designed and fabricated. Using this ex situ device, the water droplet emergence through the GDL of the PEMFC was emulated to understand liquid water transport through the porous diffusion medium. Through the visualization experiment, the emergence and growth of water droplets at the channel/GDL interface are mainly observed with the surface characteristics of GDL (SGL 10BA, 24BA) and rib when the liquid water passes through the GDL and is expelled to the flow channel. It is expected that the results obtained from this study can contribute to the better understanding on the water droplet behavior (emergence and removal) in the flow channels of PEMFC.