• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.332-336
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• 2001

The new RST is recently developed by the product expansion of the scattering functions in the field of acoustics. The new formulation suggests that the scattering coefficients consist of resonance, non-resonance, and their interactional components. In the scattering problems of acoustic waves, the moduli and phase of the resonance coefficient are obtained the appropriate results through the new RST. In our recent works the new RST was successfully applied to the scattering problem of electromagnetic waves for coated conducting cylinder and sphere. In this paper, the new RST is applied to the 2-dimensional scattering problem of electromagnetic waves for a homogeneous dielectric cylinder, and the numerical results are compared with the previous RST.

• Nonlinear Functional Analysis and Applications
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• v.28 no.2
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• pp.439-448
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• 2023

In this article, we are interested in studying the fractional Sadik Transform and a combination of the method of steps that will be applied together to find accurate solutions or approximations to homogeneous and non-homogeneous delayed fractional differential equations with constant-coefficient and possible extension to time-dependent delays. The results show that the process is correct, exact, and easy to do for solving delayed fractional differential equations near the origin. Finally, we provide several examples to illustrate the applicability of this method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.219-222
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• 2005

The temperature difference between die and workpiece has frequently caused various surface defects. The non-homogeneous temperature distribution of forged part should be analyzed to prevent the generation of various defects related with the temperature. The surface temperatures were mainly affected by the coefficient of thermal contact conductance. The precise coefficient is necessary to predict accurately the temperature changes of die and workpiece. The experiment is preformed to measure the temperature distribution of die and workpiece in closed die upsetting. And then, the coefficient is classified into function of pressure and confirmed by the comparison between experiments and FE analyses using the other model. The FE analysis to predict the temperature distribution is performed by commercial software $DEFORM-3D^{TM}$. However, it might be impossible to measure directly the temperature distribution of forged part. Therefore, the comparisons between measured temperature and predicted values are performed with the hardness of Al6061-forged part.

• Korean Journal of Environment and Ecology
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• v.31 no.5
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• pp.433-443
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• 2017

Securing the species compositional integrity (typicalness and representativeness) is the essential prerequisite for an integrated management of vegetation resources using the phytosociological $relev\acute{e}s$ and plant communities of the Z.-M. school. This study is intended to develop a tool for qualitative and quantitative evaluation of species compositional homotoneity of a set of $relev\acute{e}s$ per syntaxon. The new homotoneities, actual homotoneity ($H_{act}$), and optimal homotoneity ($H_{opt}$) taking into account the heterogeneous factors of $relev\acute{e}s$ are proposed. The correlations between the floristic variables such as the vegetation type, the new homotoneities, and the previously studied homogeneous measures (e.g. Pfeiffer's homogeneity, basic homotoneity-coefficient, corrected homotoneity-coefficient, and mean floristic similarity) are analyzed by using Spearman's rank correlation coefficient. $H_{act}$ and $H_{opt}$ are effective in determining the difference of inter-synthesized units and of inter-$relev\acute{e}s$, respectively. $H_{act}$ is the homotoneity that is the most independent of the number of $relev\acute{e}s$. On actual vegetation with long-term human impact in the Korean Peninsula, $H_{opt}$ has become an aid to the more precise understanding of $H_{act}$ as substantive homogeneousness of species composition of syntaxa. It is expected that $H_{act}$ and $H_{opt}$ can be used for the selection of a sort of homogeneous vegetation data to build a phytosociological $relev\acute{e}$-database with consistency and objectiveness for national vegetation resources.

• Communications of the Korean Mathematical Society
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• v.15 no.1
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• pp.173-181
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• 2000

The objective of this paper is to study two dimensional steady gravitational waves on the interface between two immiscible, inviscid and incompressible fluids bounded above by a horizontal rigid boundary and below by a rigid step. A KdV equation for the first order perturbation in an asymptotic expansion can appear. However the coefficient of the KdV theory fails in that case. By a unified asymptotic method, we overcome this difficulty and derive a modified KdV equation with forcing. We find homogeneous steady solutions and present numerical solutions.

• Bulletin of the Korean Mathematical Society
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• v.47 no.2
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• pp.251-261
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• 2010

This paper deals with a predator-prey model with Holling type III response function and cross-diffusion subject to the homogeneous Neumann boundary condition. We first give a priori estimates (positive upper and lower bounds) of positive steady states. Then the non-existence and existence results of non-constant positive steady states are given as the cross-diffusion coefficient is varied, which means that stationary patterns arise from cross-diffusion.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.167-185
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• 1999

A series of model tests was performed to find the characteristics of lateral behavior of single rigid pile. This paper shows the results of model tests on the lateral behavior of single rigid driven pile in non-homogeneous(two layered) Nak-Dong River sands. The purpose of this paper is to investigate the effect of the ratio of lower layer thickness to embedded pile length, the coefficient ratio of the subgrade reaction and the pile construction conditions(driven & embedded piles) on the characteristics of lateral behavior of single pile. The results of model tests show that the lateral behavior in non-homogeneous soil depends upon drop energy considerably, that is, in the case of H/L=0.75, as the drop energy increases three times the decrease percentage increases about 2.12 times. In the driven pile with non-homogeneous soil of $E_{h1}/E_{h2}=5.56$, the effect of upper layer with large stiffness on the decrease of lateral deflection is remarkably smaller than embedded pile. In non-homogeneous soil, the maximum bending moment of driven pile is in the range of 100 132% in comparison with embedded pile. The reason is that the stiffness of soil around pile increases with drop vibration and so the pile behavior is similar to the flexible pile behavior by means of the increase of relative stiffness of pile, In this paper, the experimental equations for lateral load and H/L on $y_D/y_E \; & \; MBM_D/MBM_E$ are suggested from model tests.

• Structural Engineering and Mechanics
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• v.66 no.5
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• pp.649-663
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• 2018

The scaled boundary finite element method is extended to evaluate the dynamic stress intensity factors and T-stress with a numerical procedure based on the improved continued-fraction. The improved continued-fraction approach for the dynamic stiffness matrix is introduced to represent the inertial effect at high frequencies, which leads to numerically better conditioned matrices. After separating the singular stress term from other high order terms, the internal displacements can be obtained by numerical integration and no mesh refinement is needed around the crack tip. The condition numbers of coefficient matrix of the improved method are much smaller than that of the original method, which shows that the improved algorithm can obtain well-conditioned coefficient matrices, and the efficiency of the solution process and its stability can be significantly improved. Several numerical examples are presented to demonstrate the increased robustness and efficiency of the proposed method in both homogeneous and bimaterial crack problems.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.159-165
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• 2003

Most engineers interested in stress singularities have focused mainly on the research of power stress singularities for v-notched cracks in dissimilar materials. The logarithmic stress singularity was discussed a little in Bogy's paper. The power-logarithmic stress singularity was reported by Dempsey and Sinclair. It was indicated that the logarithmic singularity is only a special case of power-logarithmic stress singularities. Then, Dempsey reported specific cases which have power-logarithmic singularities even fur homogeneous boundary conditions. It was known that logarithmic stress singularities for v-notched cracks in dissimilar materials occurs when the surfaces of a v-notched crack have constant tractions. In this paper, using the complex potential method, the stresses and displacements having logarithmic stress singularities were obtained and the coefficients vectors were calculated by a numerical program code: Mathematica. It was shown that our analysis models don't have logarithmic stress singularities under the constant tractions, although the coefficient vectors are existing.

• Coupled systems mechanics
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• v.6 no.3
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• pp.317-333
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• 2017

The present paper is concerned with the investigation of Rayleigh waves in a homogeneous transversely isotropic magnetothermoelastic medium with two temperature, in the presence of Hall current and rotation. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of Type-II and Type-III. Secular equations are derived mathematically at the stress free and thermally insulated boundaries. The values of Determinant of secular equations, phase velocity and Attenuation coefficient with respect to wave number are computed numerically. Cobalt material has been chosen for transversely isotropic medium and magnesium material is chosen for isotropic solid. The effects of rotation, magnetic field and phase velocity on the resulting quantities and on particular case of isotropic solid are depicted graphically. Some special cases are also deduced from the present investigation.