• 한국항공우주학회지
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• 제30권6호
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• pp.78-83
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• 2002

고속 열차가 터널을 통과할 때 열차 주위와 터널 내부에 발생하는 비정상 유통장을 규명하기 위해서 향상된 겹침 격자기법과 Roe의 FDS를 사용한 축대칭 Euler Solver를 개발하였다. 혼합차원기법이라는 새로운 영역기법을 개발하여 열차와 터널의 상호작용을 해석하는데 적용하였으며, 이 기법은 공간 차원의 최소 가정을 통해서 수치 계산의 효율성을 극대화하는 것에 목적을 두고 있다. 향상된 겹침 격자기법에 개발된 혼합차원기법을 추가하면 완전한 축대칭 방법과 거의 동일한 수준의 수치 정확도를 얻을 수 있다. 혼합차원기법은 특히 긴 터널에서 열차와의 상호작용을 해석할 때 높은 수치적 이득을 얻을 수 있다.

• 소성∙가공
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• 제13권6호
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• pp.484-489
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• 2004

This paper employed a systematic analysis using a 2-D hybrid special finite element containing an edge crack in order to describe the fracture behavior of spot-welds in automotive structures. The 2-D hybrid special finite element is derived form a mixed formulation with a complex potential function with the description of the singularity of a stress field. The hybrid special finite element containing an edge crack can give a better description of its singularity with only one hybrid element surrounding one crack. The advantage of this special element is that it can greatly simplify the numerical modeling of the spot welds. Some numerical examples demonstrate the validity and versatility of the present analysis method. The lap-shear, lap-tension and angle-clip specimens are analyzed and some useful fracture parameters such as the stress intensity factor and the initial direction of crack growth are obtained simultaneously.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.401-408
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• 2006

An optimum design method for hybrid control systems is proposed in this study. By considering both active and passive control systems as a combined or a hybrid system, the optimization of the hybrid system can be achieved simultaneously. In the proposed approach, we consider design parameters of active control devices and the elements of the feedback gain matrix as design variables for the active control system. Required quantity of the added dampers are also treated as design variables for the passive control system. In the proposed method, the cost of both active and passive control devices, the required control efforts and dynamic responses of a target structure are selected as objective functions to be minimized. To effectively address the multi-objective optimization problem, we adopt a preference-based optimization model and apply a genetic algorithm as a numerical searching technique. As an example to verify the validity of the proposed optimization technique, a wind-excited 20-storey building with hybrid control systems is used and the results are presented.

• 한국지진공학회논문집
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• 제12권6호
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• pp.13-23
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• 2008

본 논문에서는 거더교 형식을 갖는 교량구조물의 격자 유한요소모델에 대한 모델개선을 위해 하이브리드 유전자 알고리즘에 기초한 유한요소 모델개선기법을 제안하였다. 하이브리드 유전자 알고리즘은 유전자 알고리즘과 심플렉스 최적화방법에 기초한 직접탐색기법으로 구성하였다. 제안된 기법에 적용할 수 있도록 고유진동수, 모드형상 및 정적 처짐에 대한 계측값과 유한요소해석 결과를 사용한 적합함수를 제시하고, 강성과 질량을 동시에 개선할 수 있도록 이들 세 가지 적합함수의 선형 조합 형태를 갖는 다중목적함수를 제시하였다. 제안된 방법은 2경간 연속 격자 유한요소모델의 수치예제와 단경간 플레이트 거더교에 대하여 검증하였다. 수치예제의 경우, 랜덤 노이즈를 고려한 계측오차의 영향을 수치해석적으로 평가하였다. 수치해석과 실험적 검증을 통해, 제안된 방법이 거더교 형식의 교량에 대한 유한요소 모델개선에 적합하고 효과적임을 검증하였다.

• Communications for Statistical Applications and Methods
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• 제23권1호
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• pp.85-91
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• 2016

Aggregate claim amounts with a large claim frequency represent a major concern to automobile insurance companies. In this paper, we show that a new hybrid method to combine the analytical saddlepoint approximation and Monte Carlo simulation can be an efficient computational method. We provide numerical comparisons between the hybrid method and the usual Monte Carlo simulation.

• Geosystem Engineering
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• 제21권6호
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• pp.309-317
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• 2018

We employ a three-dimensional indirect boundary element method (BEM) to simulate temperature change around an underground liquefied natural gas storage cavern. The indirect BEM (IBEM) uses fictitious heat source strength on boundary elements as basic variables which are solved from equations of boundary conditions and then used to compute the temperature change at other points in the considered problem domain. The IBEM requires evaluation of singular integration for temperature change due to heat conduction from a constant heat source on a planar (triangular) region. The singularity can be eliminated by a semi-analytical integration scheme. However, it is found that the semi-analytical integration scheme yields sharp temperature gradient for points close to vertices of triangle. This affects the accuracy of heat flux, if they are evaluated by finite difference method at these points. This difficulty can be overcome by a combination of using a direct numerical integration for these points and the semi-analytical scheme for other points distance away from the vertices. The IBEM and the hybrid integration scheme have been verified with an analytic solution and then used to the application of the underground storage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.379-382
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• 1997

We present a hybrid self-tuning method using hyper elliptic Gaussian membership function. The proposed method applies a GA to identify the structure and the parameters of a fuzzy inference system. The parameters obtained by a GA, however, are near optimal solutions. So we solve this problem through a backpropagation-type gradient method. It is called GA hybrid self-tuning method in this paper. We provide a numerical example to evaluate the advantage and effectiveness of the proposed approach and compare with the conventional method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.1096-1099
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• 2000

A method to analyze the high speed inter-connects that are composed of frequency dependent lossy distributed lines is presented. Network modeling of hybrid systems is implemented by using the modified nodal admittance matrix in the Laplace transformation domain. The network response is computed by different two methods. One method Is the asymptotic waveform evaluation (AWE) method and other is numerical Laplace inversion method. The merits and demerits of two methods are discussed by applying to several concrete illustrative networks.

• Smart Structures and Systems
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• 제32권6호
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• pp.349-358
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• 2023

Real-Time Hybrid Testing (RTHT) requires the numerical substructure calculations to be completed within the defined integration time interval due to its real-time loading demands. For solving the problem, A Real-Time Hybrid Testing based on Restart-Loading Technology (RTHT-RLT) is proposed in this paper. In the proposed method, in case of the numerical substructure calculations cannot be completed within the defined integration time interval, the experimental substructure was returned back to the initial state statically. When the newest loading commands were calculated by the numerical substructure, the experimental substructure was restarted loading from the initial state to the newest loading commands so as to precisely disclosing the dynamic performance of the experimental substructure. Firstly, the methodology of the RTHT-RLT is proposed. Furthermore, the numerical simulations and experimental tests on one frame structure with a viscous damper are conducted for evaluating the feasibility and effectiveness of the proposed RTHT-RLT. It is shown that the proposed RTHT-RLT innovatively renders the nonreal-time refined calculation of the numerical substructure feasible for the RTHT. The numerical and experimental results show that the proposed RTHT-RLT exhibits excellent performance in terms of stability and accuracy. The proposed RTHT-RLT may have broad application prospects for precisely investigating the dynamic behavior of large and complex engineering structures with specific experimental substructure where a restarting procedure does not affect the relevant hysteretic response.

• 대한수학회논문집
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• 제30권3호
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• pp.297-311
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• 2015

We present a robust and accurate boundary condition for pricing financial options that is a hybrid combination of the payoff-consistent extrapolation and the Dirichlet boundary conditions. The payoff-consistent extrapolation is an extrapolation which is based on the payoff profile. We apply the new hybrid boundary condition to the multi-dimensional Black-Scholes equations with a high correlation. Correlation terms in mixed derivatives make it more difficult to get stable numerical solutions. However, the proposed new boundary treatments guarantee the stability of the numerical solution with high correlation. To verify the excellence of the new boundary condition, we have several numerical tests such as higher dimensional problem and exotic option with nonlinear payoff. The numerical results demonstrate the robustness and accuracy of the proposed numerical scheme.