• Communications of the Korean Mathematical Society
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• v.10 no.2
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• pp.419-438
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• 1995

We investigate a tansient diffusion approximation of queue size distribution in $M^{X}/G^{Y}/c$ system using the diffusion process with elementary return boundary. We choose an appropriate diffusion process which approxiamtes the queue size in the system and derive the transient solution of Kolmogorov forward equation of the diffusion process. We derive an approximation formula for the transient queue size distribution and mean queue size, and then obtain the stationary solution from the transient solution. Accuracy evalution is presented by comparing approximation results for the mean queue size with the exact results or simulation results numerically.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.39-45
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• 2017

We present a Brownian dynamics simulation study on the diffusion of a neutral tracer particle confined in a regularly crosslinked polymer network, especially, when the tracer size is comparable to the mesh size of the network. Polymer networks with different mesh sizes are prepared and compressed to the extent that the total polymer densities become the same. Irrespective of the network mesh size, the tracer diffusion in the networks is slowed down, showing the subdiffusion on intermediate time scales followed by the normal diffusion at long times. However, the confinement effect on the tracer diffusion becomes more significant when network strands are tightly stretched with smaller mesh size. The time scales of dynamic transitions are analyzed in terms of the probability distribution of time-correlated particle displacements.

• The Journal of the Korea Contents Association
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• v.12 no.9
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• pp.348-356
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• 2012

This study is identifying early takeoff phenomenon in relational network like SNS and investigates influence of innovator or hub at early takeoff and diffusion size at takeoff point. The major finding of this study are as follows. First, multinominal-logit analysis conducted to explore the impact of innovator and hub at early stage of information diffusion and early takeoff. Hub in early stage of information diffusion impact early takeoff. Second, our study shows that innovator and hub at early stage of information diffusion impact diffusion size at takeoff point. Third, hub is more impact early takeoff and diffusion size at takeoff point then innovator. This study provides implication for professionals by confirming hub's influence in study of successful information diffusion by early takeoff. The limitation and future direction are discussed.

• Computers and Concrete
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• v.4 no.2
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• pp.157-166
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• 2007

The paper considers a theoretical model to study sulfate ion diffusion in saturated porous media - cement based mineral composites, accounting for simultaneous effects, such as filling micro-capillaries (pores) with ions and chemical products and liquid push out of them. Pore volume change and its effect on the distribution of ion concentration within the specimen are investigated. Relations for the distribution of the capillary relative radius and volume within the composite under consideration are found. The numerical algorithm used is further completed to consider capillary size change and the effects accompanying sulfate ion diffusion. Ion distribution within the cross section and volume of specimens fabricated from mineral composites is numerically studied, accounting for the change of material capillary size and volume. Characteristic cases of 2D and 3D diffusion are analyzed. The results found can be used to both assess the sulfate corrosion in saturated systems and predict changes occurring in the pore structure of the composite as a result of sulfate ion diffusion.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.219-233
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• 2010

Understanding the Nano size particles is of great interest due to their chemical and physical behaviors such as compositions, size distributions, and number concentrations. Therefore, accurate measurements of size distributions and number concentrations in ultrafine particles are getting required because expected losses such as diffusion for the instrument system from ambient inlet to detector are a significant challenge. In this study, the data using the computed settling losses, impaction losses, diffusion losses for the sampling lines (explored different sampling line diameters, horizontal length, number of bending, line angles, flow rates with and without a bypass), and diffusion losses for the Scanning Mobility Particle Sizers are examined. As expected, the settling losses and impaction losses are very minor under 100 nm, however, diffusion loss corrections for the sampling lines and the size instrument make a large difference for any measurement conditions with high numbers of particles smaller mobility size. Both with and without the loss corrections, which can affect to size distributions and number concentrations are described. First, 80% or more of the smallest particles (less than 10 nm) can be lost in the condition of a flow rate of 0.3 liter per minute and the length of sampling line of 1.0 m, second, total number concentrations of measurements are quite significantly affected, and the mode structure of the size distribution changes dramatically after the loss corrections applied. With compared to the different measurements, statistically diffusion loss corrections yield a required process of the ambient particle concentrations. Based on the current study, as an implication, a possibility of establishing direct revelation mechanisms is suggested.

• The Journal of Information Systems
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• v.7 no.1
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• pp.77-98
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• 1998

Electronic Data Interchange(EDI) is a relatively new technique around the world and enables the firm more competitive because of transmitting computer-generated documents directly to a firm's trading partner's computer across a telecommunication network. This study investigates the relationship among the organizational characteristics and information systems(IS) maturity, and the extent of internal and external diffusion of Electronic Data Interchange (EDI) in Korean firms. The data for this study were collected from 131 firms that have implemented EDI. The results of t-test show that subgroups classified by industry, the extent of decentralization and formalization, and IS maturity, except the size of organization, are not different in the extent EDI diffusion. Also, the results of multiple regression analysis show that the size of organization is the major predictor of internal diffusion, and IS maturity and the size of organization are the major predictors in external diffusion of EDI. This study implies that the size of organization among organization characteristics and IS maturity should be considered as important variables for the diffusion of EDI system.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.332-340
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• 2003

Crosslinked poly(methyl methacrylate) particles from 2.4 to $8.1{\mu}m$ in diameter were prepared by homogenized suspension polymerization. The effect of polymerization parameters such as homogenizing speed, homogenizing time and stabilizer concentration on the particle size were examined. Optical diffusion films were prepared with the crosslinked poly(methyl methacrylate) particles. The effect of film thickness, particle size, and particle size distribution on transmittance and haze of optical diffusion film was examined. Transmittance of optical diffusion film increased with increasing particle size and decreasing film thickness. Haze increased with increasing film thickness and decreasing particle size. We also found the existence of an optimum ratio for optical performance when the mixture of small particle and large particle was used.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.492-497
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• 2009

Computer-Generated Hologram (CGH) is made for three dimensional image of a virtual object. Error diffusion method is used for the phase quantization of CGH, and it is known to be effective to the image quality improvement of the reconstructed image. However, the image quality of the reconstructed image from the CGH using error diffusion method depends on the selection of error diffusion coefficient. In this paper, we derived the relational expression to obtain the error diffusion coefficient from the position of the input object and size of the input object for CGH. As a result, the method of this thesis was able to obtain an excellent reconstructed image compared with the case to derive the error diffusion coefficient from only the position of the input image.

• Journal of Soil and Groundwater Environment
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• v.18 no.3
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• pp.65-72
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• 2013

Adsorption of melamine was examined using columns packed with granular activated carbon (GAC). Raw GAC was sieved with 20, 40, 60 and 80 mesh to determine the influence of adsorbent particle size on reaction and diffusion. The mass ratio of the adsorption capacity of GAC for melamine ranged from 9.19 to 11.06%, and adsorption rates increased with decreasing particle size within this range. Rate constants between 3.295 ~ 4.799 $min^{-1}$ were obtained using a pseudofirst-order equation that was used to determine adsorption kinetics. A surface diffusion model was adapted to take into account the unsteady-state equation of a spherical adsorbent by converting the surface concentration from a constant to a variable governed by a dispersion equation. The calculated values were fit with the experimental results by using the diffusion coefficients as regression parameters. The modified equation exhibited a more precise agreement with respect to the sum of the absolute error (SAE).

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.74-81
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• 2001

A direct numerical simulation (DNS) was applied to nonpremixed counter-flow diffusion flames between oxidizer and fuel ducts. The objective of this study is to evaluate the numerical method for simulation of axisymmetric counterflow diffusion flames. Effects of computational domain size and grid size were scrutinized, and then the method was applied to air-methane diffusion flames. The results at zero gravity conditions were in good agreement with those obtained by the one-dimension flame code OPPDIF. It was confirmed thai the numerical method is applicable to the diffusion flames at the normal gravity conditions since the results clearly showed the effects of buoyancy and velocity ratio.