• Journal of Advanced Marine Engineering and Technology
• /
• v.27 no.2
• /
• pp.289-298
• /
• 2003

Meshfree approximations exhibit significant Potential to solve partial differential equations. Meshfree methods have been successfully applied to various problems which the traditional finite element methods have difficulties to handle including the quasi-static and dynamic fracture, large deformation problems, contact problems, and strain localization problems. Reproducing Kernel Particle Method (RKPM) is used in this research fur to its built-in feature of multi-resolution. the sound mathematical foundation and good numerical performance. A formulation of RKPM is reviewed and numerical examples are given to verify the accuracy of the proposed meshfree method for largely deformed elasto-plastic material.

• Interaction and multiscale mechanics
• /
• v.2 no.1
• /
• pp.15-30
• /
• 2009

The theoretical framework of the interaction fields for multiple scales based on field theory is applied to one-dimensional problem mimicking dislocation substructure sensitive intra-granular inhomogeneity evolution under fatigue of Cu-added steels. Three distinct scale levels corresponding respectively to the orders of (A)dislocation substructures, (B)grain size and (C)grain aggregates are set-up based on FE-RKPM (reproducing kernel particle method) based interpolated strain distribution to obtain the incompatibility term in the interaction field. Comparisons between analytical conditions with and without the interaction, and that among different cell size in the scale A are simulated. The effect of interaction field on the B-scale field evolution is extensively examined. Finer and larger fluctuation is demonstrated to be obtained by taking account of the field interactions. Finer cell size exhibits larger field fluctuation whereas the coarse cell size yields negligible interaction effects.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.680-685
• /
• 2001

In this paper, RKPM is extended for solving moderately thick and thin structures. General Timoshenko beam and Mindlin plate theory are used far formulation. Shear locking is the main difficulty in analysis of these kinds of structures. Shear relaxation factor, which is formulated using the difference between bending and shear strain energy, is introduced to overcome shear locking. Analysis results obtained reveal that RKPM using introduced method is free of locking and very effectively applicable to deeply as well as shallowly beams and plates.

• Communications for Statistical Applications and Methods
• /
• v.10 no.1
• /
• pp.225-232
• /
• 2003

The support vector machine (SVM) is becoming increasingly popular in classification. The import vector machine (IVM) has been introduced for its advantages over SMV. This paper tries to improve the IVM. The proposed method, which is referred to as the polychotomous machine (PM), uses the Newton-Raphson method to find estimates of coefficients, and the Rao and Wald tests, respectively, for addition and deletion of import points. Because the PM basically follows the same addition step and adopts the deletion step, it uses, typically, less import vectors than the IVM without loosing accuracy. Simulated and real data sets are used to illustrate the performance of the proposed method.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.12 no.5
• /
• pp.73-79
• /
• 2003

In this paper, RKPM is extended for solving moderately thick and thin beams. General Timoshenko beam theory is used for formulation. Shear locking is the main difficulty in analysis of these kinds of structures. Shear relaxation factor, which is formulated using the difference between bending and shear strain energy, and corrected shear rigidity are introduced to overcome shear locking. Analysis results obtained reveal that RKPM using introduced methods is free of locking and very effectively applicable to deep beams as well as shallow beams.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.4
• /
• pp.681-690
• /
• 1999

본 논문에서는 요소를 사용하지 않은 수치해석기법인 무요소법 중에서 다중해상도(multi-resolution)특성이 내재되어 있는 Reproducing Kernel Particle Method (RKPM)의 이중스케일 분해기법을 사용하여 RKPM의 형상함수를 상단성분과 하단성분으로 분리하고 이를 3차원 선형탄성해석과정에 적용하여 von Mises 응력장의 상·하단성분을 유도하였다. 유도된 응력장의 상단성분을 이용하여 후처리과정을 거치지 않고도 응력의 고변화도 부위를 손쉽게 파악할 수 있는 기법을 개발하였으며 이를 이용한 효율적인 적응적 세분화기법의 적용가능성을 연구하였다. 대표적인 2차원 및 3차원 응력집중 문제에 적용하여 응력집중부위를 파악하고 간단한 적응적 세분화과정에 따른 절점추가를 통하여 해의 정도 향상을 파악해 본 결과, 본 연구에서 개발된 기법이 응력집중부위를 정확히 판정할 수 있었으며 효율적인 적응적 세분화기법의 유용한 도구로서 활용될 수 있음을 검증하였다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.1
• /
• pp.1-8
• /
• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.

• Journal of Korea Water Resources Association
• /
• v.49 no.4
• /
• pp.315-325
• /
• 2016

Generally, a natural river discharge is highly regulated by the hydraulic structures, and the regulated flow is substantially different from natural inflow characteristics for the use of water resources planning. The natural inflow data are necessarily required for hydrologic analysis and water resources planning. This study aimed to develop an integrated model for more reliable simulation of daily dam inflow. First, a piecewise Kernel-Pareto distribution was used for rainfall simulation model, which can more effectively reproduce the low order moments (e.g. mean and median) as well as the extremes. Second, a Bayesian Markov Chain Monte Carlo scheme was applied for the SAC-SMA rainfall-runoff model that is able to quantitatively assess uncertainties associated with model parameters. It was confirmed that the proposed modeling scheme is capable of reproducing the underlying statistical properties of discharge, and can be further used to provide a set of plausible scenarios for water budget analysis in water resources planning.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.9
• /
• pp.1376-1383
• /
• 2001

Meshless methods, developed in various ways over the past decade, have been attractive as new computational methods in that they do not need mesh generation in analyzing procedure. But most of these methods were not truly meshless methods because background meshes were required for the spatial integration of a weak form. Accordingly, in this paper, nodal integration for truly meshless methods has been studied, and an improvement scheme is proposed. To improve stabilization and accuracy, which are the weak points in previous nodal integration methods, the integration area is transformed to circle and then numerically integrated. This method does not need any adding term for stabilization in the variational formulation and then simplifies the integration procedure. Numerical test results show that the proposed method is more accurate, stable, and reasonable than the existed nodal integration methods.

• Korean Journal of Optics and Photonics
• /
• v.14 no.2
• /
• pp.194-199
• /
• 2003

The analysis of operation characteristics of a miniaturized electrostatic electron lens system called an Einzel lens was performed using a simulation tool of FCM method. The potential distributions of Einzel lenses operated both in retarding and accelerating modes show similar features. But the electric fields determined from the potential distributions show opposite directions, which results in different features in the electron beam trajectory in each mode of operation. For the same working distance, focusing voltage in the accelerating mode is higher than that in the retarding mode.