• Journal of applied mathematics & informatics
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• 제22권1_2호
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• pp.1-20
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• 2006

This paper presents the interior penalty discontinuous Galerkin finite element methods (DGFEM) for solving the rotating disk electrode problems in electrochemistry. We present results for the simple E reaction mechanism (convection-diffusion equations), the EC' reaction mechanism (reaction-convection-diffusion equation) and the ECE and $EC_2E$ reaction mechanisms (linear and nonlinear systems of reaction-convection-diffusion equations, respectively). All problems will be in one dimension.

• Journal of the Korean Statistical Society
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• 제29권4호
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• pp.489-499
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• 2000

We propose a new instrumental variable estimator of the complex parameter of a class of univariate complex-valued diffusion processes defined by the possibly non-stationary and/or nonlinear stochastic differential equations. On the basis of the exact finite sample distribution of the pivotal quantity, we construct the exact confidence intervals and the exact tests for the parameter. Monte-Carlo simulation suggests that the new estimator seems to provide a viable alternative to the maximum likelihood estimator (MLE) for nonlinear and/or non-stationary processes.

• 대한수학회지
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• 제41권3호
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• pp.435-459
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• 2004

Identification problems for the system governed by abstract nonlinear damped second order evolution equations are studied. Since unknown parameters are included in the diffusion operator, we can not simply identify them by using the usual optimal control theories. In this paper we present how to solve our identification problems via the method of transposition.

• 대한수학회지
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• 제51권3호
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• pp.635-654
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• 2014

We consider the Cauchy problem for a Keller-Segel-fluid model with degenerate diffusion for cell density, which is mathematically formulated as a porus medium type of Keller-Segel equations coupled to viscous incompressible fluid equations. We establish the global-in-time existence of weak solutions and bounded weak solutions depending on some conditions of parameters such as chemotactic sensitivity and consumption rate of oxygen for certain range of diffusive exponents of cell density in two and three dimensions.

• 대한수학회지
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• 제31권4호
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• pp.545-558
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• 1994

In this paper, we will investigate the existence of positive solutions to the predator-prey interacting system $$ {-\varphi(x, u)\Delta u = uf(x, u, \upsilon) in \Omega {-\psi(x, \upsilon)\Delta\upsilon = \upsilon g(x, u, \upsilon) {\frac{\partial n}{\partial u} + ku = 0 on \partial\Omega {\frac{\partial n}{\partial\upsilon} + \sigma\upsilon = 0. $$ in a bound region $\Omega$ in $R^n$ with smooth boundary, where $\varphi$ and $\psi$ are strictly positive functions, serving as nonlinear diffusion rates, and $k, \sigma > 0$ are constants.

• 충청수학회지
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• 제10권1호
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• pp.87-95
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• 1997

In general, the positive solution to biological reaction-diffusion equations is not unique. In this paper, we state the sufficient and necessary conditions of the existence of positive solutions, and give and the proof for the uniqueness of positive solutions for a certain elliptic interacting system.

• 대한수학회보
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• 제47권6호
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• pp.1225-1234
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• 2010

Numerical solutions for the fractional differential dispersion equations with nonlinear forcing terms are considered. The backward Euler finite difference scheme is applied in order to obtain numerical solutions for the equation. Existence and stability of the approximate solutions are carried out by using the right shifted Grunwald formula for the fractional derivative term in the spatial direction. Error estimate of order $O({\Delta}x+{\Delta}t)$ is obtained in the discrete $L_2$ norm. The method is applied to a linear fractional dispersion equations in order to see the theoretical order of convergence. Numerical results for a nonlinear problem show that the numerical solution approach the solution of classical diffusion equation as fractional order approaches 2.

• East Asian mathematical journal
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• 제24권4호
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• pp.407-414
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• 2008

Finite difference schemes are considered for a $Ca^{2+}$ diffusion equations with damping and convection terms, which describe $Ca^{2+}$ buffering by using stationary and mobile buffers. Stability and $L^{\infty}$ error estimates of approximate solutions for the corresponding schemes are obtained using the extended Lax-Richtmyer equivalence theorem.

• Korean Journal of Mathematics
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• 제13권2호
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• pp.149-159
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• 2005

We study an age-dependent s-i-s epidemic model with spatial diffusion. The model equations are described by a nonlinear and nonlocal system of integro-differential equations. Finite difference methods along the characteristics in age-time domain combined with finite elements in the spatial variable are applied to approximate the solution of the model. Stability of the discrete periodic solution is investigated.

• Structural Engineering and Mechanics
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• 제75권1호
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• pp.59-69
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• 2020

The purpose of this study is to develop practical tools for the mechanical design of cylindrical porous media subjected to a broad gap in a hygrothermal environment. The planar axisymmetrical and transient hygrothermoelastic field in a porous hollow cylinder that is exposed to a broad gap of temperature and dissolved moisture content and is free from mechanical constraint on all surfaces is investigated considering the nonlinear coupling between heat and binary moisture and the diffusive properties of both phases of moisture. The system of hygrothermal governing equations is derived for the cylindrical case and solved to illustrate the distributions of hygrothermal-field quantities and the effect of diffusive properties on the distributions. The distribution of the resulting stress is theoretically analyzed based on the fundamental equations for hygrothermoelasticity. The safety hazard because of the analysis disregarding the nonlinear coupling underestimating the stress is illustrated. By comparing the cylinder with an infinitesimal curvature with the straight strip, the significance to consider the existence of curvature, even if it is infinitesimally small, is demonstrated qualitatively and quantitatively. Moreover, by investigating the bending moment, the necessities to consider an actual finite curvature and to perform the transient analysis are illustrated.