• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.773-777
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• 2011

본 논문에서는 국부적으로 비선형 거동을 보이는 고전적인 $J_2$ 소성흐름 이론에 근거한 탄소성 문제의 해를 효율적으로 구하기 위해 전체-국부 확장함수를 지닌 일반유한요소법을 제안한다. 제안된 기법은 비선형 거동을 보이는 영역을 포함하는 국부 문제의 비선형 해를 구하고 이를 일반유한요소법의 단위 오목 분할의 개념을 통해 전체 문제의 해 공간을 확장하는데 이용한다. 이는 적은 계산량으로 복잡한 탄소성문제의 정확한 해를 얻는 것을 가능하게 하며 기법의 강건성과 정확성을 입증하기 위한 수치해석 예제가 다루어진다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.768-772
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• 2011

본 논문에서는 켤레구배법을 이용해 전체-국부 확장함수를 지닌 일반유한요소법을 해석하는 방식을 제안한다. 이 기법은 편미분방정식의 해에 대한 정보가 충분하지 않은 경우에도 수치해석적인 방법으로 일반 유한요소법의 확장함수를 구성할 수 있으며 해석 과정 중 추가의 계산 없이 좋은 성능을 지닌 전처리값 및 초기 추측치를 활용할 수 있어 국부적으로 복잡한 거동을 보이는 문제의 해석에 유리하다. 본 논문에 포함된 수치해석 예제의 결과는 제안된 기법이 가우스 소거법과 같은 직접 솔버를 이용하는 경우보다 수치 해석적으로 더 효율적임을 보여준다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.405-412
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• 2011

This paper introduces the generalized finite element method with global-local enrichment functions using the preconditioned conjugate gradient method. The proposed methodology is able to generate enrichment functions for problems where limited a-priori knowledge on the solution is available and to utilize a preconditioner and initial guess of good quality with only small addition of computational cost. Thus, it is very effective to analyze problems where a complex behavior is locally exhibited. Several numerical experiments are performed to confirm its effectiveness and show that it is computationally more efficient than the analysis utilizing direct solvers such as Gauss elimination method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.477-480
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• 2006

To represent the accurate feature of signal and system, many researches have been done in many fields of basic and engineering science which led a great development of modem society. Even until currently, in order to acquire useful information from signals at high speed, many methods and transforms have been processed. In these methods, the Fourier transform which represents signal as the combination of the frequency component has been applied to the most fields. But as transform not to consider time information, the Fourier transform does not provide time information of the time and presents only overall features of signals. The wavelet transform, which is proposed to overcome this problem and recently expands the range of the application, presents time-frequency localization and many kinds of the wavelet can be applied according to the environment of application. In this paper, we detect the features of signals using the function which is considered as the wavelet and do research for filtering locally in the wavelet plane.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.630-648
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• 1992

The minimum weight design for simply-supported isotropic or symmetrically laminated stiffened cylindrical shells subjected to various loads (axial compression or combined loads) is studied by a nonlinear mathematical search algorithm. The minimum weight design in accomplished with the CONMIN optimizer by Vanderplaats. Several types of buckling modes with maximum allowable stresses and strains are included as constraints in the minimum weight design process, such as general buckling, panel buckling with either stingers or rings smeared out, local skin buckling, local crippling of stiffener segments, and general, panel and local skin buckling including stiffener rolling. The approach allows the consideration of various shapes of stiffening members. Rectangular, I, or T type stringers and rectangular rings are used for stiffened cylindrical shells. Several design examples are analyzed and compared with those in the previous literatures. The unstiffened glass/epoxy, graphite/epoxy(T300/5208), and graphite/epoxy aluminum honeycomb cylindrical shells and stiffened graphite/epoxy cyindrical shells under axial compression are analyzed through the present approach.