• Biotechnology and Bioprocess Engineering:BBE
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• 제7권4호
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• pp.225-230
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• 2002

Experiments on deactivation kinetics of immobilized lipase enzyme from Candida cyl-indracea were performed in stirred bath reactor using rice bran oil as the substrate and temperature as the deactivation parameter. The data were fitted In first order deactivation model. The effect of temperature on deactivation rate was represented by Arrhenius equation. Theoretical equations were developed based on pseudo-steady state approximation and Michaelis -Menten rate expression to predict the time course of conversion due to enzyme deactivation and apparent half-life of the immobilized enzyme activity in PFR and CSTH under constant feed rate polity for no diffusion limitation and diffusion limitation of first order. Stability of enzyme in these continuous reactors was predicted and factors affecting the stability were analyzed.

• 경영과학
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• 제13권1호
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• pp.71-95
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• 1996

Many researchers have studied the theme on CASE technology. However, there are no many researches which lightened the diffusion of CASE technology and organizational change. The purpose of this study is to investigate the factors that influence on the diffusion of CASE technology and the way how IS organization changes as a result of the diffusion. We exploited a case study research as a methodology. We selected five software development firms which possessed the leading IS technology abilities as the case companies. We realized that the diffusion of CASE technology proceeded under the three context variables - managerial context of information systems, the intent and behavior of key players and implementation strategy of organization - to enhance the performance of information systems. The contribution of this study is to clarify the change of IS organization as a result of CASE technology diffusion. This study has the limitation that tried to analyze the organizational change only in a direction.

• 산업공학
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• 제23권4호
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• pp.337-348
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• 2010

The Bass model is the most widely used model in research of new product diffusion because it presents a nice explanation on the diffusion process of new products. However, it has a limitation that its performance of fitness is lower as the available data become less and also, the diffusion curve is bell-shape and so, it can not represent the various diffusion patterns. Recently, a two-pieces Bass model is developed and applied to analyze diffusion of 10 products. The results are encouraging in terms of fitness. However, diffusion pattern is not dealt with in the paper. In this paper, analysis of diffusion pattern is in depth addressed in two-pieces Bass model. It is shown that the diffusion curves are divided into 3 types with respect to the peak adoption rate and each type is divided into 2 types further. Takeoff time of a diffusion process is analyzed by using the inflection point and regime-change time where it represents the point that imitation and innovation parameters change. Empirical studies for 68 products(28 domestic products and 40 USA products) are performed to analyze the diffusion pattern. Findings are that diffusion patterns of all products except 1 USA product show type I and regime-change time becomes shorter as the introduction time of the product is later in domestic products and regime-change time can be regarded as a takeoff time in 47% of total 68 products.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.315-322
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• 2016

Room acoustic properties of coupled rooms connected by an aperture has been analyzed using statistical acoustic model based on the diffused sound field assumption, which has limitation in dealing with the parameters such an room geometries and non uniform absorptivity of the boundary surfaces. In order to overcome these difficulties the acoustic diffusion model has been introduced, by which distribution of the acoustic energy density can be analyzed for various shapes and wall absorptivity. In this study acoustic properties of coupled rooms connected by an aperture(e.g. door) is analyzed using acoustic diffusion equation, which is solved numerically. The mean energy densities of two rooms obtained by the diffusion model are compared with those from the statistical model. The results show good agreement for various coupling aperture sizes and absorption coefficients. For a limiting case when the partition wall is substituted by an aperture and the two rooms eventually forms a single room, results of coupled room analysis using diffusion model show good agreement with those of a single room.

• Investigative Magnetic Resonance Imaging
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• 제23권1호
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• pp.26-33
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• 2019

Purpose: Diffusion tensor imaging (DTI) data must be analyzed by an analyzer after data processing. Hence, the analyzed data of DTI might depend on the analyzer, making it a major limitation. This paper reviewed previous DTI studies reporting the repeatability and reproducibility of data from the corticospinal tract (CST), one of the most actively researched neural tracts on this topic. Materials and Methods: Relevant studies published between January 1990 and December 2018 were identified by searching PubMed, Google Scholar, and MEDLINE electronic databases using the following keywords: DTI, diffusion tensor tractography, reliability, repeatability, reproducibility, and CST. As a result, 15 studies were selected. Results: Measurements of the CSTs using region of interest methods on 2-dimensional DTI images generally showed excellent repeatability and reproducibility of more than 0.8 but high variability (0.29 to 1.00) between studies. In contrast, measurements of the CST using the 3-dimensional DTT method not only revealed excellent repeatability and reproducibility of more than 0.9 but also low variability (repeatability, 0.88 to 1.00; reproducibility, 0.82 to 0.99) between studies. Conclusion: Both 2-dimensional DTI and 3-dimensional DTT methods appeared to be reliable for measuring the CST but the 3-dimensional DTT method appeared to be more reliable.

• 한국콘텐츠학회논문지
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• 제7권10호
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• pp.202-210
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• 2007

요인분석은 실증분석을 위한 사전 연구 분석 방법으로 많이 활용하고 있다. 따라서 요인분석은 매우 중요한 연구 방법의 하나이다. 또한 요인분석에 대한 연구자의 욕구도 높아서 요인분석 결과가 제공하지 못하는 정보를 요구하기도 한다. 이를 요인분석의 한계점으로 인식하고, 이를 해결하기 위한 연구 방법론을 제시하였다. 본 연구에서 통계적 방법을 통하여 연구되는 사회과학 분야의 요인분석에 대한 한계점을 극복하기 위한 방법론을 결합적 연구방법론이라고 하였으며, 기존의 통계분석 방식인 요인분석, AHP분석, 확산이론, 그리고 인과관계를 설명할 수 있는 시스템다이내믹스를 결합한 것이다.

• 한국콘텐츠학회논문지
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• 제12권9호
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• pp.348-356
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• 2012

본 연구는 SNS와 같은 관계네트워크의 구성원 중에서 혁신자와 허브가 정보 확산 초기 발생하는 이른 도약(early takeoff)과 도약시점의 확산크기에 어떠한 영향을 미치는 지를 파악하는 것을 목적으로 한다. 이를 위해 본 연구는 다음과 같이 가설을 설정하였다-가설 1은 네트워크에서 혁신자 와 허브는 이른 도약(early takeoff)에 영향을 미칠 것이다, 가설 2는 네트워크에서 혁신자와 허브는 도약시점의 확산크기에 영향을 미칠 것이다. 가설을 검증하기 위해 우리나라 SNS중에서 C사이트를 대상으로 로그데이터를 수집하여 혁신자와 허브를 추출하고 이들의 정보 수용행동을 다항로짓분석 및 회귀분석하였다. 그 결과, 네트워크에서 허브는 이른 도약과 도약시점의 확산크기에 모두 긍정적인 영향을 미치며, 혁신자는 확산크기에만 긍정적인 영향을 미치는 것으로 나타났다. 또한 허브는 혁신자 보다 이른 도약과 도약시점의 확산크기에 있어 상대적인 영향이 더 큰 것으로 나타났다. 이러한 결과는 네트워크에서 허브는 높은 연결성을 통해 자신의 정보수용행동을 빠른 시간에 관계네트워크내 구성원들에게 확산시킬 수 있기 때문인 것으로 보인다. 이러한 결과를 바탕으로 몇 가지 시사점과 한계점을 토의하였다.

• CRM연구
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• 제1권1호
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• pp.49-69
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• 2006

기존의 초기 기술 수용 모델(TAM)과 후기 기술 수용 모델(PAM)을 사용한 연구에서는 설문 조사를 통해 어느 한 시점의 상황만을 분석할 수 있어 제품 수명 주기에 따른 수요의 변화를 시계열적으로 나타낼 수 없는 한계점이 있었다. 이러한 문제를 해결하고자 본 연구에서는 시스템 다이내믹스 방법론을 활용하여 TAM과 TAM2에 대한 시뮬레이션 모델을 구축하여 개선 방안을 알아보고, 기존의 연구를 바탕으로 초기 수용부터 재구매에 이르는 수요의 변화를 시간의 흐름에 따라 동태적으로 분석하는 시뮬레이션 모델을 수립하였다. 특히 본 모델은 현재 국내의 실제 휴대 전화 시장을 고려하여 설계되었는데, 본 모델을 이용한 시뮬레이션 결과, 현재 우리나라의 휴대 전화 확산 패턴과 유사하게 나옴으로써 본 모델의 타당성을 확인할 수 있었다. 본 시뮬레이션 모델은 시간에 따른 소비자의 제품 수요 변화를 시각적인 그래프 형태로 제공하기 때문에 시장 상황에 따른 수요 변화에 대한 탁월한 학습 도구의 역할을 수행할 수 있으며, 따라서 IT 기업들의 시장 수요 예측 등에 활용될 수 있을 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제40권5호
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• pp.352-362
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• 2012

Mass transfer behavior in wood was estimated through its microscopic structure. The diffusion coefficients which were decided by theoretical equations are influenced by different anatomical properties of wood. From the experiment, the moisture flux was linear to the square root of time. The diffusion coefficients had a regular tendency during the time elapse. During the modeling, it is necessary to understand the limitation of parameters and consider the particular situation to be simulated. In hardwood, because the apertures were not considered, tangential mass transfer simulation was totally different from experiment. As a result, a hardwood model design should consider the apertures which are even on the fiber walls.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.737-741
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• 2004

We presents new results for transport properties of dumbbell fluids by equilibrium molecular dynamics (EMD) simulations using Green-Kubo and Einstein formulas. It is evident that the interaction between dumbbell molecules is less attractive than that between spherical molecules which leads to higher diffusion and to lower friction. The calculated viscosity, however, is almost independent on the molecular elongation within statistical error bar, which is contradicted to the Stokes' law. The calculated thermal conductivity increases and then decreases as molecular elongation increases. These results of viscosity and thermal conductivity for dumbbell molecules by EMD simulations are inconsistent with the earlier results of those by non-equilibrium molecular dynamics (NEMD) simulations. The possible limitation of the Green-Kubo and Einstein formulas with regard to the calculations of viscosity and thermal conductivity for molecular fluids such as the missing rotational degree of freedom is pointed out.