• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.179-189
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• 2005

Corrosion of steel due to chloride attack is a major concern in reinforced concrete structures which are located in the marine environments. In this case, Fick's 2nd law has been used for the prediction of chloride diffusion related with service life of concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation to chloride attack in concrete structures and to investigate the validity of Fick's law to chloride attack combined carbonation. The test results indicate that the chloride ion profiles from Fick's law using the diffusion coefficient of immersion tests is not reflected the effect of separation of chloride ions in carbonation region but valid in sound region in case of combined action. On the other hand, the chloride ion profiles from Fick's law using the diffusion coefficient of Tang and Nilsson's method coincide with test results under dry-wet condition but not under combined condition. The results of present study may Imply that the new method for the measurement of diffusion coefficient is required to predict the chloride ion profiles in case of combined action at early.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.102-108
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• 2017

The phenomenon of technological discontinuity which occurs during technological diffusion and substitution between incumbents and new technology is important to understand the behavior of technology diffusion and substitution of single and multiple technologies. Our research defined the concept of technological discontinuity and developed a model capable of measuring the region of technological discontinuity. Based on a literature review and a model development, we proposed a definition and a model regarding technological discontinuity.The accuracy of the model is verified by applying it on a semiconductor industry case. The technological discontinuity is defined as the region in which both the incumbent and new technology co-exist and the performance of the incumbent technology is better than that of the new technology. In addition, we can model the technological discontinuity using discontinuous time and discontinuous performance. This research will be very useful to understand not only technological discontinuity but also technology diffusion or substitution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.679-688
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• 2010

The major objective of the present study is to extend the applications of inverse analysis to more realistic engineering fields with a complex combustion process rather than the traditional simple heat-transfer problems. In order to do this, the unknown initial mass fractions of $CH_4/O_2$ are estimated from the temperature measurement data by inverse analysis in the practical diffusion-controlled turbulent combustion problem. In order to ensure efficient inverse analysis, the repulsive particle swarm optimization (RPSO) method, which belongs to the class of stochastic evolutionary global optimization methods, is implemented as an inverse solver. Based on this study, it is expected that useful information can be obtained when inverse analysis is used in the diagnosis, design, or optimization of real combustion systems involving unknown parameters.

• Journal of the Korean Vacuum Society
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• v.3 no.1
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• pp.51-58
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• 1994

확산 현상은 박막성장 과정 및 박막의 기계, 전기, 자기적 성질 이해에 중요한 역할을 한다. 열 처리에 의한 상호확산 때문에 생긴 Pd/Cu 다층박막의 조성변화를 AES depth-profiling 방법을 이용해 서 조사하였다. 열처리전 시료에서의 각형의 초기 조성분포가 여러온도에서의 열처리에 의해 정현파 모 양의조성분포로 변화되었다. 조성의존성을 고려하지 않은 상호확산 계수를 정현파 분포의 진폭으로부터 구하였으며, 1.66 eV의 값을 갖는 활성화에너지는 Arrhenius plot으로부터 산출하였다. 또한 Boltzmann-Matano 방법을 사용해서 15$0^{\circ}C$에서의 조성의존 상호확산계수도 구하였다. 열처리에 의해 조 성균일화가 되는 것으로만 알려졌던 본물질계에서도 상분리가 생성됨을 관찰하였고, 그 열처리 조건은 $180^{\circ}C$에서 150분 보다 짧아야함을 밝혔다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.510-515
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• 2005

Doppler spread can occur due to the relative movement of transmitter and receiver. The Doppler frequency shift varies as the relative location and the velocity of transceivers change. This Doppler spread may seriously degrade the performance of OFDM system which is considered to be very efficient for multimedia wireless communication. Therefore, applying the method of receiver diversity, we analyze the degree of BER improvement in Doppler spread environments to investigate the effectiveness of the chosen methods according to various wireless channels.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.895-906
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• 2015

Diffusion is a mathematical tool to explain the fluctuation of financial assets and the movement of particles in a micro time scale. There are ongoing statistical trials to develop an estimation method for diffusion models based on likelihood. When we estimate diffusion models by applying the maximum likelihood estimation method on data observed at discrete time points, we need to know the transition density of the diffusion. In order to approximate the transition densities of diffusion models, we suggests the method to approximate the path integral of the random process with normal random variables, and compare the numerical properties of the method with other approximation methods.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1994.05a
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• pp.20-33
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• 1994

우리나라에 있어서 양액재배는 지금으로부터 40년전으로 거슬러 올라간다. 그러나 현재의 발전수준은 양액재배가 발전된 나라들에 비하면 특히 그 수준이 저조한 상태에 머물고 있다. 그러나 최근에 들어 그러한 현상은 농민을 에워싼 환경의 변화에 따라 크게 자극을 받고 있다. 시설원예의 일부가 양액재배로 전환되어 가는 일이 전국적으로 확산되어가고 있다. 이러한 현상은 마치 사람이 깊은 잠을 자고 난 후에 다시 활발한 활동을 시작하는 것처럼 지구상의 생물의 주기적인 활동현상과 유사해서 장래의 발전에 기대가 된다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.123-124
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• 2003

산업의 발달로 인한 대기오염의 심각화 현상은 국지적인 현상을 뛰어넘어 지역적인 문제로까지 확산되고 있다. 황사 현상의 경우만 하더라도 이제는 한국, 중국, 일본 만의 문제가 아닌 미국 서부해안까지도 그 영향을 받는 것으로 보고 되고 있다. 이처럼 국가간 장거리 이동오염물질의 관측 및 평가에 즈음하여 우리나라에서도 중국 및 일본과 함께 동북아시아 지역에서의 장거리 이동오염물질에 대한 연구를 활발히 진행하고 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.87-88
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• 2001

대기오염물질 제거에 중요한 역할을 하는 침적 현상은 크게 건성침적(dry deposition)과 습성침적(wet deposition)으로 구분된다. 건성침적은 오염물질이 중력이나 분자 확산에 의해 지면이나 그 부근에 침강ㆍ흡착하는 현상이며, 습성침적은 구름 속의 에어로졸이 응결핵으로 제거되는 성우제거(rainout)와 구름 이하의 고도에서 강수에 의해 제거되는 세척제거(washout)와 같은 현상을 일컫는다. 습성침적은 강수 및 구름 물리와 관련하여 대기 중 오염물질 제거에 큰 비중을 차지함에도 불구하고 건성침적에 비해 그 연구가 미흡한 실정이며, 침적 모형을 이용한 연구는 더욱 찾아보기 어렵다. (중략)

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.608-614
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• 1999

The counter-diffusion of aromatic compounds such as coronene and tetra-phenylporphine by injection of acetone or tetra-phenylporphine solution was studied on aluminas and silica-alumina used widely as catalysts support. The counter-diffusivity was determined from simulation results by using the counter-diffusion model employing ideal adsorbed solution theory. The counter-diffusivities of aromatic compounds in the catalyst supports were ranged in ${\sim}10^{-15}m^2/sec$ in the desorption process by the injection of excess acetone. In the counter-diffusion process with tetra-phenylporphine solution which have similar concentration with adsorption solution, the counter-diffusivities of coronene were also ${\sim}10^{-15}m^2/sec$, and that of tetra-phenylporphine into pores were determined as ${\sim}10^{-11}m^2/sec$. The counter-diffusivities of coronene desobed from the adsorbent were significantly redyced in comparison with the effective diffusivities when there is counter-diffusion flux. The values mainly depended on the existence of counter-diffusion flux, but not concerned with the species and amount of desorbates.