• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.273-277
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• 2012

The vacuum drying process for drying of paper in current transformers was modeled with an aim to develop an understanding of the drying mechanism involved and also to predict the water collection rates. A molecular as well as macroscopic approach was adopted for the prediction of drying rate. Ficks law of diffusion was adopted for the prediction of drying rates at macroscopic levels. A steady state and dynamic mass transfer simulation was performed. The bulk diffusion coefficient was calculated using weight loss experiments. The accuracy of the solution was a strong function of the relation developed to determine the equilibrium moisture content. The actually observed diffusion constant was also important to predict the plant water removal rate. Thermo gravimetric studies helped in calculating the diffusion constant. In addition, simulation studies revealed the formation of perpetual moisture traps (loops) inside the CT. These loops can only be broken by changing the temperature or pressure of the system. The change in temperature or pressure changes the kinetic or potential energy of the effusing vapor resulting in breaking of the loop. The cycle was developed based on this mechanism. Additionally, simulation studies also revealed that the actual mechanism of moisture diffusion in CT's is by surface jumps initiated by surface diffusion balanced against the surrounding pressure. Every subsequent step in the cycle was to break such loops. The effect of change in drying time on the electrical properties of the insulation was also assessed. The measurement of capacitance at the rated voltage and one third of the rated voltage demonstrated that the capacitance change is within the acceptance limit. Hence, the new cycle does not affect the electrical performance of the CT.

• Bulletin of the Korean Mathematical Society
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• v.50 no.6
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• pp.1827-1840
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• 2013

This paper is concerned with the positive steady states of a diffusive Holling type II predator-prey system, in which two predators and one prey are involved. Under homogeneous Neumann boundary conditions, the local and global asymptotic stability of the spatially homogeneous positive steady state are discussed. Moreover, the large diffusion of predator is considered by proving the nonexistence of non-constant positive steady states, which gives some descriptions of the effect of diffusion on the pattern formation.

• Journal of the Korean Mathematical Society
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• v.43 no.3
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• pp.659-676
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• 2006

In this paper, we consider three-component reaction-diffusion system. With an integral condition and a global coupling, this system gives us an interesting free boundary problem. We shall examine the occurrence of a Hopf bifurcation and the stability of solutions as the global coupling constant varies. The main result is that a Hopf bifurcation occurs for global coupling and this motion is transferred to the stable motion for strong global coupling.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.673-678
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• 2002

There are various methods for the electrochemical techniques to estimate diffusion coefficient of chloride ions in concrete, such as ASTM C 1202 test method, Andrade's method, Dhir's method, Tang's method, and etc. In the case of estimating diffusion coefficient of chloride ions in concrete by using these methods, applied voltage and resistivity nay exercise some influence on the characteristics of chloride ions diffusion. Thus. in this study, effect of applied voltage and resistivity on the characteristics of chloride ions diffusion in concrete were researched by applying voltage in 12V, 30V, and 60V, and by using resistivity in 0.2Ω and 1.0Ω, respectively. It can be concluded that diffusion coefficient of chloride ions are found to be increasing as the individual applied voltage and resistivity decrease, when water-cement ratio is constant.

• 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.

• The Pure and Applied Mathematics
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• v.24 no.4
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• pp.201-209
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• 2017

We prove convergence properties of the global solutions to the cooperative cross-diffusion system with the intra-specific cooperative pressures dominated by the inter-specific competition pressures and the inter-specific cooperative pressures dominated by intra-specific competition pressures. Under these conditions the $W^1_2-bound$ and the time global existence of the solution for the cooperative cross-diffusion system have been obtained in [10]. In the present paper the convergence of the global solution is established for the cooperative cross-diffusion system with large diffusion coefficients.

• Journal of the Korean Chemical Society
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• v.41 no.8
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• pp.385-391
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• 1997

Diffusion Coefficient$(D_0)$ and electrode reaction rate Constant$(K_0)$ of Co$(dimethyl bipyridine)_3(ClO_4)_2$ were determined by cyclic voltammetry and chronoamperometry. It was also investigated that the effects of solvent, concentration, and scan rate, etc. on the diffusion coefficient and the temperature effect on the rate constant. The peak currents and diffusion coefficients were dcreased as increasing the viscosity of solvent. Diffusion coefficient was $5.54{\times}10^{-6 }cm^2/sec$ and the reaction rate constant was $2.39{\times}10^{-3 }/s$ at 25$^{\circ}C$. The thermodynamic parameters such as ${\Delta}G^{\neq},\;{\Delta}H^{\neq},\;and\;{\Delta}S$ were calculated from plotting the reaction rate constants versus the solution temperatures. This compound was shown the catalytic effect on the oxygen reduction that the reduction peak current of oxygen was greatly enhanced and the peak potential was shifted to +0.2 volt.

• Journal of Environmental Science International
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• v.33 no.8
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• pp.583-589
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• 2024

Seawater movement analyses and dye diffusion experiments were conducted to understand the characteristics of eddy diffusion in the southwest coastal zone of Korea. The findings indicate that pollutants entering the study area were most influenced by tidal currents and showed temporal and spatial variations according to the turbulent characteristics of the tidal current. Pollutants entering the study area are likely to travel a distance of approximately 2 km (within 1 h) following the direction of the tidal currents and show a spreading distance (diameter of the diffusion area) of within 10% of the travel distance (within 200 m). The dispersion of the diffusion area is expected to increase in proportion to the elapsed time raised to a power of 1.19 to 1.23. The results are expected to provide a basis for using the eddy diffusion coefficient as a temporally variable value (previously assumed to be a constant based on empirical data), thereby contributing to improving the predictive accuracy of ocean diffusion models.

• Journal of the Korean Chemical Society
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• v.52 no.3
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• pp.217-222
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• 2008

We investigate the kinetics of diffusion-influenced catalytic reactions occurring in small reaction volume. From a simple exact model study, we find that the reaction rate coefficient decreases with the size of reaction volume. The explicit expression for the average reaction rate constant is presented, which can be regarded as a generalization of well-known Collins-Kimball rate constant into the reactions occurring in a small reaction volume. It turns out that the traditional diffusion influenced reaction dynamics is followed by a single exponential relaxation phase with a rate constant dependent on the reaction volume for the catalytic reactions occurring in small reaction volumes.

• Fisheries and Aquatic Sciences
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• v.7 no.2
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• pp.90-95
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• 2004

An analytical model for predicting the convection-diffusion of solute dumped in a homogeneous open sea of constant water depth has been developed in a time-integral form. The model incorporates spatially uniform, uni-directional, mean and oscillatory currents for horizontal convection, the settling velocity for the vertical convection, and the anisotropic turbulent diffusion. Two transformations were introduced to reduce the convection-diffusion equation to the Fickian type diffusion equation, and then the Galerkin method was then applied via the expansion of eigenfunctions over the water column derived from the Sturm-Liouville problem. A series of calculations has been performed to demonstrate the applicability of the model.