• International Journal of Precision Engineering and Manufacturing
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• v.5 no.2
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• pp.53-59
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• 2004

The pseudospectral method is applied to the analysis of out-of$.$plane free vibration of circularly curved Timoshenko beams. The analysis is based on the Chebyshev polynomials and the basis functions are chosen to satisfy the boundary conditions. Natural frequencies are calculated for curved beams of circular cross sections under hinged-hinged, clamped-clamped and hinged-clamped end conditions. The present method gives good accuracy with only a limited number of collocation points.

• Korean Journal of Mathematics
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• v.13 no.2
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• pp.161-176
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• 2005

We consider a model of population dynamics whose mortality function is unbounded. We note that the regularity of the solution depends on the growth rate of the mortality near the maximum age. We propose Gauss-Legendre methods along the characteristics to approximate the solution when the solution is smooth enough. It is proven that the scheme is convergent at fourth-order rate in the maximum norm. We also propose discontinuous Galerkin finite element methods to approximate the solution which is not smooth enough. The stability of the method is discussed. Several numerical examples are presented.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.190-192
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• 2008

This paper shows the formulation of fast moving least square reproducing kernel method (FMLSRKM) which is a kind of meshfree methods. FMLSRKM has some advantages compared to conventional numerical techniques such as finite element method. For simple analysis on a rectangular waveguide, point collocation scheme is introduced and applied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1752-1761
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• 2000

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Journal of the Chungcheong Mathematical Society
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• v.7 no.1
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• pp.141-152
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• 1994

We consider a numerical scheme for solving a nonlinear boundary integral equation (BIE) obtained by reformulation the nonlinear boundary value problem (BVP). We give a simple alternative to the standard collocation method for the nonlinear BIE. This method consists of one conventional linear system and another coupled linear system resulting from an auxiliary BIE which is obtained by differentiating both side of the nonlinear interior integral equations. We obtain an analogue BIE through the perturbation of the fundamental solution of Laplace's equation. We procure the super-convergence of approximate solutions.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.6
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• pp.1-10
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• 1997

By using the boundary element method, the cahracterization and the circuit modelling of the coplanar waveguide (CPW) discontinuities are performed bvia quasi-static approximation. The capacitive equivalent circuits are obtained by developing the 3-D boundary element method with collocation method. On the triangular patch, the numerical scheme employed the linear basis functions and the analytic solutions of the integrals on the singular points. The capacitive discontinuities of gaps, end-gaps, and open-ends are characterized and the results compared with the conductor backed coplanar waveguides.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.103-110
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• 1987

When a crack in the plate with a circular hole approaches to the hole, the large stress concentration phenomenon appears at the boundary of the circular hole and the crack tip. As a numerical analysis method for the stress concentration in a structure, the Finite Element Method has been used. In this paper, however, the Boundary Element Method is employed, which may reduce the numbers of input data and the calculating time when compared with the Finite Element Method. A finite flat plate having a crack between the two circular holes is chosen as a model in this study. The results by the Boundary Element Method are compared with those of the Boundary collocation Method by Newman, which are already well established. And the structural behavior near the circular hole and at the crack tip is also investigated.

• Structural Engineering and Mechanics
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• v.8 no.5
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• pp.439-452
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• 1999

A simple numerical scheme suitable for tracing the fracture propagation path for structures idealized by means of Hillerborg's classical cohesive crack model is presented. A direct collocation, multidomain boundary element method is adopted for the required space discretization. The algorithm proposed is necessarily iterative in nature since the crack itinerary is a priori unknown. The fracture process is assumed to be governed by a path-dependent generally nonlinear softening law. The potentialities of the method are illustrated through two examples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.25-31
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• 1995

본 연구는 방음벽의 성능예측을 위해 BEM의 접근 방법을 시도하였으며 범용 음향 소프트웨어인 Sys-noise 5.2의 direct collocation bem을 사용하여 반무한 평면 방음벽에 대한 해석을 수행하였으며, 그 결과를 검증하기 위해 Maekawa에 의한 근사해와 해석적 점근해에 비교하였다. 또한, 수음점이 방음벽으로부터 떨어진 거리, 방음벽의 폭, 방음벽의 높이에 따른 삽입손실을 계산하였고, 방음벽에 흡음처리를 한 경우와 방음벽상단의 형상변화에 따른 삽입손실의 변화를 계산하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.7
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• pp.684-692
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• 2010

Based on the planar restricted three body problem formulation, optimized trajectories for the Earth-Moon transfer are obtained. Mixed impulsive and continuous thrust are assumed to be used, respectively, during the Earth departure and Earth-Moon transfer/Moon capture phases. The continuous, dynamic trajectory optimization problem is reformulated in the form of discrete optimization problem by using the method of direct transcription and collocation, and then is solved using the nonlinear programming software. Representative results show that the shape of optimized trajectory near the Earth departure and the Moon capture phases is dependent upon the relative weight between the impulsive and the continuous thrust.