• The Korean Journal of Applied Statistics
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• v.18 no.1
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• pp.57-66
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• 2005

In this paper, we propose a method to evaluate the solutions of the renewal equations related to SPRT for Erlang distribution. In SPRT, the Average Sample Number(ASN) and type I or type II error probabilities are shown in Fredholm type integral equations. The integral equations are generally solved by the approximation method using Gaussian quadrature. For Erlang distribution, it has been known that the exact solutions of the equations exist. We propose the algorithm to solve the equations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.375-382
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• 2008

The particular integral formulation for two(2D) and three(3D) dimensional inelastic transient dynamic stress analysis is presented. The elastostatic equation is used for the complementary solution. Using the concept of global shape function, the particular integrals for displacement and traction rates are obtained to approximate acceleration of the inhomogeneous equation. The Houbolt time integration scheme is used for the time-marching process. The Newton-Raphson algorithm for plastic multiplier is used to solve the system equation. Numerical results of four example problems are given to demonstrate the validity and accuracy of the present formulation.

• Journal of Korea Game Society
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• v.18 no.5
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• pp.123-132
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• 2018

Various methods have been proposed to efficiently animate the motion of soft objects in realtime. In order to maintain the topology between the elements of the objects, it is required to employ constraint forces, which limit the size of the time steps for the numerical integration and reduce the efficiency. To tackle this, an implicit method with larger steps was proposed. However, the method is, in essence, a linear system with a large matrix, of which solution requires heavy computations. Several approximate methods have been proposed, but the approximation is obtained with an increased damping and the loss of accuracy. In this paper, new integration method based on harmonic oscillation with better stability was proposed, and it was further stabilized with the hybridization with approximate implicit method. GPU parallelism can be easily implemented for the method, and large-scale soft objects can be simulated in realtime.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.163-168
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• 2011

Robust optimization or reliability-based design optimization are some of the methodologies that are employed to take into account the uncertainties of a system at the design stage. For applying such methodologies to solve industrial problems, accurate and efficient methods for estimating statistical moments and failure probability are required, and further, the results of sensitivity analysis, which is needed for searching direction during the optimization process, should also be accurate. The aim of this study is to employ the function approximation moment method into the sensitivity analysis formulation, which is expressed as an integral form, to verify the accuracy of the sensitivity results, and to solve a typical problem of reliability-based design optimization. These results are compared with those of other moment methods, and the feasibility of the function approximation moment method is verified. The sensitivity analysis formula with integral form is the efficient formulation for evaluating sensitivity because any additional function calculation is not needed provided the failure probability or statistical moments are calculated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.12-22
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• 1994

Time evolution of linear water waves on a constant depth generated by a disturbance is analyzed by asymptotic methods; stationary phase, steepest descents and leading wave approximation. In order to verify the derived formulae of surface displacements for 1-D and 2-D waves. surface displacements are calculated and plotted from both the formulae and a numerical integration. The existing results for surface displacements are verified in which the leading amplitude of 1-D waves during the evolution decays as f- T/B, the rest of the wavetrain as t$^{-1}$ 2/ and the rest of the wavetrain of 2-D waves as t-1. But it is shown that the leading amplitude of 2-D waves decays as t 5/6 which is different from Kajiura's result t$^{-4}$ 3/.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.555-559
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• 2009

난류응력은 순간속도성분을 시간평균성분과 편차성분의 합으로 보고 Navier-Stokes 방정식으로부터 Reynolds 방정식을 유도할 때 나타나게 된다. Reynolds 방정식으로부터 수심 적분된 천수방정식을 유도하는 과정에서 시간 평균된 유속성분을 수심 적분된 유속성분과 편차성분의 합으로 본다면, 분산응력 (dispersion stress)이라고 하는 추가적인 새로운 항이 잔류하게 된다. 점성응력, 난류응력, 그리고 분산응력을 통칭하여 유효응력 (effective stress)이라고 한다. 일반적으로 수심에 비해 수로 폭이 넓은 개수로에서는 유효응력이 흐름특성의 수치 근사해에 큰 영향을 미치지 못한다고 가정하여 2차원 수심적분 모형에서 유효응력을 생략하기도 한다. 또한 유효응력을 적용하더라도, 점성응력이 난류응력에 비해 무시할 만큼 작다고 가정하여 난류응력만을 적용하며, 분산응력은 무시된다. 하지만 만곡부에서는 원심력과 편수위로 인한 횡방향 압력의 불균형이 발생하기 때문에, 만곡부의 이차류가 발생되며, 유속의 연직방향 분포도 일정하지 않게 된다. 따라서 본 연구의 목적은 만곡부의 이차류 특성을 수심적분 2차원 모형에 반영하기 위해 분산응력을 고려한 모형의 개발 및 검증이다. 불규칙한 모의영역을 원활히 나타낼 수 있도록 곡선좌표계를 사용하는 여타 모형들과 달리 유한유소법을 이용하여 수치해를 구하며, 따라서 x, y 좌표축을 사용하는 데카르트 좌표계를 사용하여 지배방정식을 나타낸다. 분산응력의 유 무에 따른 수치결과를 Rozovskii의 $180^{\circ}$ 만곡수로 실내실험 자료와 비교하여 개발 모형을 검증한다.

• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.58-62
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• 1995

Integral equations of self-radiation impedance of a rectangular piston in a rigid infinite baffle are derived using by polar coordinate. The self-radiation impedance is separated by two parts ; self-radiation resistance and self-radiation reactance. Derived integral equations are simulated by numerical method. Based on the numerical results, self-radiation impedance can be obtained in the low and high frequency ranges without any limited conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.6
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• pp.571-579
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• 1987

The integral equations used in electromagnetic fields theory can be used for scattering problems. We can obtain various characteristics of scatterer. Ie, power pattern, scattered field, by finding current distribution on the scatterer. In this paper, current distribution on polygonal cylinder is obtained using integral equations in 2 dimension. For numerical aualysis, the moment method is used with pulse function as a basis function and integral equation is used with extrapolation method, which saves cpu time.

• Proceedings of the Korean Statistical Society Conference
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• 2005.05a
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• pp.31-36
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• 2005

EDF에 근거한 Cramer-von Mises 형태의 통계량을 합교원리를 이용하여 다변량으로 일반화한다. 그리고 제안된 통계량의 귀무가설에서의 극한분포를 적절한 공분산함수를 가진 가우스 과정의 적분의 형태로 표현하고 통계량의 근사적인 계산방법을 고려한다.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.3
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• pp.56-63
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• 1983

강성체로된 견인물체가 탄성무한경면으로 지지된 점탄성층 위를 미끄러져 갈 때 접촉구간에서의 압력분포와 마찰 특성을 고찰하였다. 즉, 접촉구간에서의 강성체의 모양과 압력분포에 관한 적분 방정식을 구하고, 점탄성층의 두께가 접촉구간에 비하여 충분히 두꺼울 때 압력분포와 마찰계 수의 근사해를 구하였다. 압력분포의 모양은 점탄성층의 물성을 표시하는 지수값, 즉 .alpha.<1/2, .alpha.=1/2, .alpha.>1/2에 따라서 크게 다르다. 한편, 수치해석에 의하면 마찰 계수에 대한 근 사해는 강성체의 미끄럼 속도, 점탄성 층의 두께, 탄성체의 영율 (E$_{o}$ )과 점탄성층의 시효 성탄성계수 (E$_{v}$ )의 차, 즉 E$_{o}$ /E$_{v}$ 에 따라 변화함을 알 수 있다. 즉, 탄성체가 점탄성층에 비하여 딱딱하면 할수록, 또 강성체 속도가 느리면 느릴수록 마찰계수는 작아진다. 그리고 불성의 지수(.alpha.)가 커지면 커질수록 근사해의 수렵 속도는 느려지게 되고 지 수(.alpha.)가 1에 가까워지면 점탄성층의 탄성효과는 점성효과에 비하여 거의 무시할 수 있으며 근사해는 의미가 없어지게 된다.