• 대한수학회보
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• 제35권2호
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• pp.345-362
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• 1998

We introduce and anlyze a naturally parallelizable frequency-domain method for parabolic problems with a Neumann boundary condition. After taking the Fourier transformation of given equations in the space-time domain into the space-frequency domain, we solve an indefinite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution of the original problem in the space-time domain. Existence and uniqueness of a solution of the transformed problem corresponding to each frequency is established. Fourier invertibility of the solution in the frequency-domain is also examined. Error estimates for a finite element approximation to solutions fo transformed problems and full error estimates for solving the given problem using a discrete Fourier inverse transform are given.

• 한국공간구조학회논문집
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• 제3권4호
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• pp.59-67
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• 2003

Genetic algorithm is one of the best ways to solve a discrete variable optimization problem. Genetic algorithm tends to thrive in an environment in which the search space is uneven and has many hills and valleys. In this study, genetic algorithm is used for solving the design problem of gable structure. The design problem of frame structure has some special features(complicate design space, many nonlinear constrants, integer design variables, termination conditions, special information for frame members, etc.), and these features must be considered in the formulation of optimization problem and the application of genetic algorithm. So, 'FRAME operator', a new genetic operator for solving the frame optimization problem effectively, is developed and applied to the design problem of gable structure. This example shows that the new opreator has the possibility to be an effective frame design operator and genetic algorithm is suitable for the frame optimization problem.

• 한국콘텐츠학회논문지
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• 제20권11호
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• pp.636-643
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• 2020

차분 진화 알고리즘은 연속적인 문제 공간인 실수 최적화 문제를 해결하기 위해 개발된 메타휴리스틱 기법 중에 하나이다. 본 연구에서는 차분 진화 알고리즘을 불연속적인 문제 공간인 외판원 문제 해결에 사용하기 위하여 차분 진화 알고리즘에 난수 키 표현법을 적용하였다. 차분 진화 알고리즘은 실수 공간을 탐색하고 오름 차순으로 정렬된 해의 인덱스의 순서를 도시 방문 순서로 하여 적합도를 구한다. TSPLIB에서 제공하는 표준 외판원 문제에 적용하여 실험한 결과 제안한 난수 키 표현법 기반 차분 진화 알고리즘이 외판원 문제 해결에 가능성을 가지고 있음을 확인하였다.

• 대한수학회보
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• 제42권2호
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• pp.397-404
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• 2005

In this note, we characterize the limiting diffusion of a diploid model by defining the discrete generator for the resealed Markov chain. We conclude that this limiting diffusion model is with uncountable state space and mutation selection and special 'mutation or gene conversion rate'.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.123-131
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• 2006

The majority of pedestrian fatalities and injuries are caused by vehicle-pedestrian accidents. Recently, it has been recognized as a serious problem. Injuries of occupants in a vehicle have been decreased considerably. However, efforts for protection of pedestrians are still insufficient. These days, many advanced industries are striving for a better protection of pedestrians by using an active hood lift system, rather than reforming the existing structure. In this research, the active hood lift system is designed to enhance the performance for protection. The active hood lift system is analyzed by using the nonlinear finite element method. An optimization problem is formulated by incorporation of the analysis results. Orthogonal arrays are utilized to solve the formulated problem. An iterative optimization algothrithm using orthogonal arrays is utilized for design in the discrete space. It is found that the method can remarkably decrease the number of function evaluations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.708-713
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• 2000

The design of experiment(DOE) is getting more attention in the engineering community since it is easy to understand and apply. Recently, engineering designers are adopting DOE with orthogonal arrays when they want to design products in a discrete design space. In this research, a design flow with orthogonal arrays is defined fur structural design according to the general DOE. The design problem is defined as a general structural optimization problem. Sensitivity information is evaluated by the analysis of variance(ANOVA), and an optimum design is determined from analysis of means(ANOM). Interactions between design variables are investigated to achieve additivity which should be valid in DOE. When strong interactions exit, a method is proposed. Some methods to consider the problem are suggested.

• 한국전산구조공학회논문집
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• 제34권4호
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• pp.221-230
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• 2021

전역 최적화 문제의 해를 유전 알고리즘을 사용하여 얻어 완전파형역산을 수행하고 층상 반무한체의 물성치를 추정하는 기법을 제안한다. 조화 수직 하중이 작용하는 층상 반무한체의 동적 응답을 측정하고, 이를 추정 물성치를 사용하여 계산된 응답과 비교한다. 응답의 추정치는 mid-point integrated finite element와 perfectly matched discrete layer를 사용하여 구성된 thin-layer model로부터 얻는다. 전역 최적화 문제의 목적 함수는 응답의 관측치와 추정치의 차이에 대한 L2-norm으로 계산된다. 유전 알고리즘을 사용하여 전역 최적화 문제의 해를 구하여 완전파형역산을 수행한다. 제안된 기법을 기본 진동 모드 뿐만이 아니라 고차 진동 모드도 우세한 다양한 층상 반무한 매질에 적용하여, 측정치가 잡음을 포함하지 않는 경우와 포함하는 경우 모두에 대해서 제안된 완전파형역산 기법은 층상 반무한체의 재료 특성을 추정하는데 적합함을 확인할 수 있다.

• International Journal of Aeronautical and Space Sciences
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• 제7권2호
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• pp.121-127
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• 2006

An analysis procedure for the combined problem of control algorithm and aeroelastic system which is based on the computational fluid dynamics(CFD) technique has been developed. The aerodynamic forces in the transonic region are calculated from the transonic small disturbance(TSD) theory. An linear quadratic regulator(LQR) controller is designed to suppress the transonic flutter. The optimal control gain is estimated by solving the discrete-time Riccati equation. The system identification technique rebuilds the CFD-based aeroelstic system in order to form an adequate system matrix which involved in the discrete-time Riccati equation. Finally the controller, that is constructed on the basis of system identification technique, is used to suppress the flutter phenomenon of the airfoil with attached store. This approach, that is, the CFD-based aeroservoelasticity design, can be utilized for the development of effective flutter controller design in the transonic region.

• 한국공간구조학회논문집
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• 제2권3호
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• pp.61-70
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• 2002

The objective of this study is the development of a size and shape discrete optimum design algorithms, which is based on the genetic algorithms and the fuzzy theory. This algorithms can perform both size and shape optimum designs of plane and space trusses. The developed fuzzy shape-GAs (FS-GAs) was implemented in a computer program. For the optimum design, the objective function is the weight of structures and the constraints are limits on loads and serviceability. This study solves the problem by introducing the FS-GAs operators into the genetic.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2150-2158
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• 2002

A recent research and development has the requirement for the optimization to shorten design time of modified or new product model and to obtain more precise engineering solution. General optimization problem must consider many conflicted objective functions simultaneously. Multi-objective optimization treats the multiple objective functions and constraints with design change. But, real engineering problem doesn't describe accurate constraint and objective function owing to the limit of representation. Therefore this study applies variance analysis on the basis of structure analysis and DOE to the vertical roller mill fur portland cement and proposed statistical design model to evaluate the effect of structural modification with design change by performing practical multi-objective optimization considering mass, stress and deflection.