• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.16 no.4
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• pp.249-256
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• 2012

In this work, we analyze the spatial patterns of a predator-prey system with cross diffusion. First we get the critical lines of Hopf and Turing bifurcations in a spatial domain by using mathematical theory. More specifically, the exact Turing region is given in a two parameter space. Our results reveal that cross diffusion can induce stationary patterns which may be useful in understanding the dynamics of the real ecosystems better.

• Journal of Digital Convergence
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• v.12 no.3
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• pp.141-147
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• 2014

Diffusion model is popular research topic in marketing and economy particularly for the areas of model specification and market size forecasting. In particular, Bass model can explain Roger's innovation diffusion and product life cycle through easy mathematical representation and hence the model has been widely used for the explanation of adopting innovative new products and technologies. Nonetheless, there're only a couple of pioneering researches about semiconductor market, using diffusion models. Consequently, we'd utilise NLS approach diffusion model to estimate the market potential of MOSFET, major switching device for power management of system, and explain the process to industry stakeholders and policy makers for delivery of managerial implication with pragmatic purpose.

• Atmosphere
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• v.14 no.3
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• pp.29-40
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• 2004

It is well known that convections and fronts are the most effective weather systems for the vertical transport of pollutants. I used a two dimensional front model in order to investigate the mechanism of the vertical transport of atmospheric pollutants between planetary boundary layer(PBL) and free atmosphere by fronts. The main dynamic processes which contribute the vertical transport of pollutants are advection and diffusion. The transported amount of pollutant from the boundary layer to the free atmosphere increases dramatically during the developing stage of the front. 46% of pollutants are transported vertically within 12 hour and 54% are transported within 24 hour. In the meantime, compared to the total amount of pollutants transported by both advection and diffusion, about 25% (30%) less pollutants are transported when only advection (diffusion) process in included in the model. The most important mechanism for the vertical transport is vertical advection, while the vertical diffusion process plays an important role in the redistribution of pollutants in the PBL.

• Korean Management Science Review
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• v.32 no.1
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• pp.133-145
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• 2015

Motion picture industry in Korea has been growing constantly and aroused various kinds of research attention. Particularly, the introduction of official box-office database service brought quantitative studies. However, approaches based on diffusion models have been rarely found with domestic film markets. In addition to the fundamental statistical review on Korea and US film markets, we applied a diffusion model to daily box-office revenue. Unlike conventional preference of Gamma distribution on the film markets, estimation results proved that BMIC can also explain the trend of daily revenue successfully. The comparison with BMIC showed that there is a distinctive difference in diffusion patterns of Korea and US film markets. Generally, word-of-mouth effect appeared more significant in Korea.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.261-271
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• 2018

In this study, a hydraulic model test, to which Particle Image Velocimetry (PIV) system applied, was used to determine the hydrodynamic characteristics of the advection-diffusion of saltwater according to bottom conditions (impermeable/permeability, diameter, and inclination) and the difference of the initial salt. Considering quantitative and qualitative results from the experiment, the characteristics of the density current were discussed. As an experimental result, the advection-diffusion mechanism of salinity was examined by the shape of saltwater wedge and the flow structure of density currents with various bottom conditions. The vertical salt concentration obtained from the experiment was used as quantitative data to calculate the diffusion coefficient that was used in the numerical model of the advection-diffusion of saltwater.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1073-1075
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• 1998

This paper presents the method of parameter estimation of diffusion model for monitoring Demand-Side Management Program. Bass diffusion model was applied in this paper, which has different values according to parameters ; coefficients of innovation, imitation and potential adopters. Though it is very important to estimate three parameter, there are no empirical results in practice. Thus, this paper presents the method of parameter estimation in case of few data with constraints to reduce the possibility of bad estimation. The constraints are empirical results or expert's decision. Case studies show the diffusion curves of high-efficient lighting and also forecasting of the peak value for power demand considering diffusion of high-efficient lighting, the feedback and least-square parameter estimation method used in this paper enable us to evaluate the status and forecasting of the effect of DSM program.

• Journal of Powder Materials
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• v.7 no.3
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• pp.137-142
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• 2000

In order to analyze the densification behaviour of stainless steel powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model, as well. The power-law creep model in conjunction with various diffusion models was applied to the HIP process of 316L stainless steel powder compacts under 50 and 100 MPa at $1125^{\circ}C$. The results of the calculations were verified using literature data. It could be found that the contribution of the diffusional mechanisms is not significant under the current process conditions.

• Journal of Korean Institute of Industrial Engineers
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• v.40 no.4
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• pp.415-423
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• 2014

In recent decades, RFID (Radio Frequency IDentification) technology has been recognized as one of the most core competencies in implementing ubiquitous society. However, Korea has not seen good success in diffusion of RFID even though Korean government continues funding many projects to diffuse the technology in industries. Most previous researches overestimate the growth of Korean RFID market in contrary to real market situation. This study aims to analyze the Korean RFID market and find a reasonable forecasting model for it. Our experimental results show that Bass forecasting model provides the more realistic estimates than any other models and the analyses of forecasting error provide useful information for the better forecasting. We also observed that government policy plays a crucial role in the diffusion of RFID technology in Korea.

• Computers and Concrete
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• v.17 no.1
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• pp.53-66
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• 2016

Currently, most of the investigations on chloride diffusion were based on the experiments and simulations concerning single cation type chlorides. Chloride diffusion associated with dual or multi cation types was rarely studied. In this paper, several groups of diffusion experiments are conducted using chloride solutions containing single, dual and multi cation types. A multi-ionic model is also proposed to simulate the chloride diffusion behavior in the experimental tests. The MATLAB software is used to numerically solve the nonlinear PDEs in the multi-ionic model. The experimental and simulated results show that the chloride diffusion behavior associated with different cation types is significantly different. When the single cation type chlorides are adopted, it is found that the bound rates of chloride ions combined with divalent cations are greater than those combined with monovalent cations. When the dual/multi cation type chlorides are adopted, the chloride bound rates increase with the $Ca^{2+}/Mg^{2+}$ percentage in the source solutions. This evidence indicates that the divalent cations would markedly enhance the chloride binding capacity and reduce the chloride diffusivity. Moreover, on the basis of the analysis, it is also found that the complicated cation types in source solutions are beneficial to reducing the chloride diffusivity.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.3
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• pp.46-56
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• 1998

The objective of this study was to investigate the relationship between water vapor diffusion properties and the pore structure of paper. Gas-phase molecular diffusivity of water vapor through pores was determined based on the kinetic theory of gas. A mathematical model was derived to characterize the dimensional changes of the pore caused by the fiber-swelling mechanism. A modified-Fickean diffusion model was designed to simulate the water-vapor diffusion phenomena in porous paper web. Structural characterisocs of paper pores including the tortuosity and the shape factor was studied on a theoretical basis of Knudsen flow diffusion. Results are summarized as follows: 1. The theoretical water vapor diffusivity in gas-phase was 0.092$cm^2$ /min, 2. Porosity was inversely proportional to the degree of wet-swelling of paper, 3. Solid-phase water-diffusivity of fiber was 1.2 $ \times 10^{-5}cm^2/min$, 4. Modified diffusion model was fairly consistent to the experimental data (from part I), and 5. The Fickean pore tortuosity, ranging from 1,000 to 2,500, was in inverse proportion to the porosity of paper, and the Knudsen shape factor and length-angle factor for micro-pores in paper were 0.5~3.5 and about 340, respectively.