• Korean Management Science Review
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• v.12 no.3
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• pp.163-175
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• 1995

The future demand of the satellite broadcasting service is analyzed through the competitive diffusion model. Diffusion rates of the satellite broadcasting service in the case that the decreasing effect due to the cable TV service is considered are smaller than those in the independent case. Diffusion rates of the satellite broadcasting service are shown to become different according to environmental conditions.

• Journal of applied mathematics & informatics
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• v.11 no.1_2
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• pp.125-141
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• 2003

This paper treats the conditions for the existence and stability properties of stationary solutions of reaction-diffusion equations of Gierer-Meinhardt type, subject to Neumann boundary data. The domains in which diffusion takes place are of three types: a regular hexagon, a rectangle and an isosceles rectangular triangle. Considering one of the relevant features of the domains as a bifurcation parameter it will be shown that at a certain critical value a diffusion driven instability occurs and Turing bifurcation takes place: a pattern emerges.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.185-186
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• 2022

In this study, a numerical analysis was conducted using a two-dimensional diffusion-wave analysis model to analyze the validity about the application of eco-friendly prefabricated rainwater detention system in grit chamber and permanent pond. As a result of the analysis, it is confirmed that the flood prevention effect, such as a decrease in peak flow rate and a delay in peak time, is excellent, so it is considered reasonable to apply eco-friendly prefabricated rainwater detention system in grit chamber and permanent pond.

• Computers and Concrete
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• v.20 no.2
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• pp.185-196
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• 2017

Durability problems initiated from steel corrosion are unseen but critical issues, so that many researches are focused on chloride penetration evaluation. Even if RC (Reinforced Concrete) structures are exposed to normal environment, chloride ingress varies with concrete surface conditions and exposed period. This paper presents an analysis technique for chloride behavior evaluation considering time effect on diffusion and surface conditions assumed as double-layered system. For evaluation of deteriorated surface condition, field investigation was performed for concrete pavement exposed to deicing agent for 18 years. In order to consider enhanced surface concrete, chloride profiles in surface-impregnated concretes exposed to chloride attack for 2 years from previous research were investigated. Through reverse analysis, effectively deteriorated/enhanced depth of surface and the related reduced/enlarged diffusion coefficient in the depth are simulated. The proposed analysis technique was evaluated to handle the chloride behavior more accurately considering changes of chloride ingress within surface layer and decreased diffusion coefficient with time. For the concrete surface exposed to deicing agent, the deteriorated depth and enlarged diffusion coefficient are evaluated to be 12.5~15.0 mm and 200% increasing diffusion coefficient, respectively. The results in concrete containing enhanced cover show 10.0~12.5 mm of impregnated depth and 85% reduction of chloride diffusion in tidal and submerged conditions.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.114-122
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• 2016

Concrete is cost-benefit and high-durable construction material, however durability problem can be caused due to steel corrosion under chloride attack. Recently deicing salt has been widely spread in snowing season, which accelerates micro-cracks and scaling in surface concrete and the melted deicing salt causes corrosion in embedded steel. The previous governing equation of Fick's 2nd Law cannot evaluate the deteriorated surface concrete so that another technique is needed for the surface effect. This paper presents chloride penetration analysis technique for concrete subjected to deicing salt utilizing multi-layer diffusion model and time-dependent diffusion behavior. For the work, field investigation results of concrete pavement exposed deicing salt for 18 years are adopted. Through reverse analysis, deteriorated depth and increased diffusion coefficient in the depth are evaluated, which shows 12.5~15.0mm of deteriorated depth and increased diffusion coefficient by 2.0 times. The proposed technique can be effectively applied to concrete with two different diffusion coefficients considering enhanced or deteriorated surface conditions.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.51-57
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• 2009

The purpose of this study would evaluate if having clinical effects on diffusion image with quantitative analysis through ADC values of brain's normal tissue and lesions before and after contrast injections using a 3.0T. From November in 2007 until December in 2008, a total of 32 patient was performed on 3.0T(Signa Excite, GE Medical System, USA) with the normal or lesions in the patient who requests diffusion weighted image with 8channel head coil. The pulse sequence was used with spin echo EPI(TR: 10000msec, TE: 72.2 msec, Matrix: 128*128, FOV: 240 mm, NEX: 1, diffusion direction: 3, b-value: 1000). Measurement results of ADC values on lesions, CSF, white matter, gray matter, lesions after contrast injection were measured less 75% than before contrast injection, infarction: 100%, CSF: 78%(high), white matter: 71.4%(low), gray matter: 50%(high, low). The results of paired t-test on the deference of ADC values which statically is significant in three(lesions, CSF, white matter)regions except for white matter(p<0.05). Quantitative analysis of lesions, CSF, white matter, gray matter have difference on all regions. ADC values were low in lesions and white matter, normal CSF after contrast injection commonly is high than before contrast injection, ADC values which white matter were high and low (50:50) after contrast injection. 3.0T diffusion weighted image clinically supposed that performing DWI examination after contrast injection was not desirable because of having effects on brain tissue.

• Knowledge Management Research
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• v.9 no.3
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• pp.77-105
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• 2008

This study primarily aims at identifying what factors significantly affect the diffusion of knowledge management systems(KMS) and finding out how these identified factors can be effectively managed, especially for Korean companies. The research model is derived based on previous researches on innovation diffusion, information systems implementation, and KMS. The model is used to examine the role of determinants in influencing the extent to which KMS is diffused within organizations. Independent variables of this research are composed of technical characteristics, organizational characteristics and environmental characteristics. 'Breadth of diffusion' and 'depth of diffusion' concept are used to measure the extent of KMS diffusion which is the dependent variable of this model. The 101 companies of total 1,000 samples responded to the survey. To analyze tile results of this empirical study, we performed the multiple regression analysis. As a result, it was shown that the relative advantage, complexity, information system maturity, size, top management support, champion, competitive pressure have influences on both the breadth and the depth diffusions. On the other hand, the organizational culture, valuation and compensation, and uncertainty of environmental factors were not verified to be significant. This empirical study will provide Korean companies with insights into effective ways to diffuse the KMS and succeed in business competition.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1127-1134
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• 1994

The analytical model for the induced Hall field in the magnetotransistor considering the diffusion of carriers has been proposed and verified by experiment and simulation. Previous models for the induced Hall field in the magnetotransistor do not consider the influence of the diffusion carrier transport. However, the carrier diffusion in the base region of magnetotransistors cannot be neglected and should be considered to evaluated the Hall field in the magnetotransistors accurately. We have measured the Hall voltage in the base region of the fabricated magnetotransistors. The measured values have been compared with the numerical results evaluated from our diffusion model as well as the calculated results from the conventional model. The evaluated Hall voltage from the diffusion model agrees well with the measured values while the sign of the Hall voltage calculated by the conventional model is opposite to that of the measured values in the saturation region. This discrepancy is due to the fact that the diffusion model considers the carrier diffusion while the conventional one does not. The Hall field model including the influence of carrier diffusion may be an important tool to optimize the device structure and to understand the operating principle of the magnetotransistor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1671-1678
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• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.5
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• pp.412-421
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• 2013

Motion picture industry is one of the most representative fields in the cultural industry and has experienced constant growth both worldwide and within domestic markets. However, little research has been undertaken for diffusion patterns of motion pictures, whereas various issues such as demand forecasting and success factor analysis have been widely explored. To analyze diffusion patterns, we adopted extended Bass model to reflect the potential demand of movies. Four clusters of selected movies were derived by k-means clustering method with criteria of opening strength and profitability and then compared by their diffusion patterns. Results indicated that movies with high profitability and medium opening strength are most significantly influenced by word of mouth effect, while low profitability movies display nearly monotonic decreasing diffusion patterns with noticeable initial adoption rates and relatively early peak points in their runs.