• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.151-154
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• 2009

본 연구에서는 Proper Orthogonal Decomposition (POD)를 이용하여 공력축소모델을 구축하였다. 일반적으로 Euler equations과 같은 높은 정확도를 가지는 공력해석을 수행할 경우 많은 계산 비용이 발생하게 된다. 특히 공탄성 해석과 같이 수차례의 공력해석이 필요한 경우 그 비용은 더 증가하게 된다. 이러한 문제를 줄이기 위해서 축소모델(Reduced Order Model; ROM)의 개발은 반드시 필요하다. 공력축소모델을 구하는 방법 중 하나인 POD는 snapshot 데이터로부터 기저벡터를 구하고, 이들의 선형결합을 통하여 축소된 공간에서 해를 찾는 방법이다. 본 연구에서는 POD 기저벡터를 이용한 공력축소모델을 구축하고, 이를 전투기 날개문제에 적용하여 구하여진 정상상태 해와 Euler 해석 결과를 비교해 보았다. 또한 진동하는 익형문제에 적용하여 봄으로써 공탄성 해석에 적용 가능성 여부를 확인하였다.

• The Korean Journal of Applied Statistics
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• v.19 no.2
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• pp.331-338
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• 2006

Quantification method III is designed by C. Hayashi as visualizing technique for two-way cross-classified tables. Specially in Japan, its usefulness is timely proven in social and marketing surveys. In several instances, relatively large quantification scores are assigned to low-frequency categories. Thus, they lead to unreliable data interpretation. The aim of this study is to develop stable solution to overcome such traits of quantification method III. The solution is of shrinkage type induced by small perturbations and is applied to a multiple response data obtained in a Korean social survey.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.139-152
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• 2010

This study presents graphic-user interface computer program for optimal compensation of differential column shortening with high field applicability. The implemented system can perform both relative and mixed compensation while satisfying both performance and construction constraints. In the proposed system the shape of the structure before and after compensation can be checked graphically, and the results of compensation of each stories can be printed in drawings which can be directly used as the report of column shortening. The field-applicability of the implemented system was verified by applying it to the four reinforced concrete residental buildings of 61, 42, 49 and 53 stories where compensation of differential column shortening had already been performed. Using the implemented system, compensation can be performed easily with the various constraint conditions and was able to acquire rational compensation results for the cases where conventional method was not successful.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.628-630
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• 2004

정렬되지 않은 3차원 측정 점들로부터 이들을 근사하는 표면을 재구성하는 방법을 제안하였다. 제안된 방법은 경계면 축소포장 방식에 의한 표면 재구성 방법 (shrink-wrapped boundary face : SWBF)으로, 측정 점으로부터 경계셀과 경계면을 구해 초기 메쉬를 생성하고 이를 연속적으로 축소하는 방식에 의해 표면을 재구성한다 제안된 방법은 기존의 표면 축소포장 방식의 메쉬 생성 방법의 문제점인 물체의 토폴로지에 대한 제악이 없이 어떠한 형태의 표면 재구성에도 적용이 가능하며, 기존 방법이 축소 단계에서 각 메쉬 정점에 대한 최단거리 측정점을 찾는 전역 탐색을 해야 하는데 비해 지역 탐색만으로 최적의 측정 점을 찾을 수 있으므로 처리 시간 측면에서도 우월하다. 실험을 통해 제안된 표면 재구성 알고리즘이 측정 점들간의 관계를 알 수 없는 정렬되지 않은 3차원 정들에 대한 표면 재구성에 매우 안정적이고 효과적임을 확인할 수 있었다.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.279-280
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• 2015

본 논문에서는 연근해 파력발전 시스템을 제안한다. 바다에는 부력체와 동력전달부만을 설치하고, 나머지 시스템은 육상에 설치하여, 기존의 원해 파력발전 시스템에 비해 초비 투자 비용이 저감된다. 연근해 파력발전 시스템의 축소 모형을 제작하였으며, 이를 통해, 연근해 파력발전 시스템의 출력 특성을 분석하였다. 제안된 시스템의 출력 특성이 풍력발전 시스템의 특성과 비슷하게 나타남을 확인할 수 있으며, 실현 가능성이 충분하다고 판단할 수 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.65-73
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• 2007

In the inverse perturbation method, enormous computational resource was required to obtain reliable results, because all unspecified DOFs were considered as unknown variables. Thus, in the present study, a reduced system method is used to condense the unspecified DOFs by using the specified DOFs, and to improve the computational efficiency as well as the solution accuracy. In most of the conventional reduction methods, transformation errors occur in the transformation matrix between the unspecified DOFs and the specified DOFs. Thus it is hard to obtain reliable and accurate solution of inverse perturbation problems by reduction methods due to the error in the transformation matrix. This numerical trouble is resolved in the present study by adopting iterative improved reduced system(IIRS) as well as by updating the transformation matrix at every step. In this reduction method, system accuracy is related to the selection of the primary DOFs and Iteration time. And both are dependent to each other So, the two level condensation method (TLCS) is selected as Selection method of primary DOFs for increasing accuracy and reducing iteration time. Finally, numerical verification results of the present iterative inverse perturbation method (IIPM) are presented.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.281-285
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• 2008

Eigenvalue reduction schemes approximate the lower eigenmodes that represent the global behavior of the structures. In the previous study, we proposed a two-level condensation scheme (TLCS) for the construction of a reduced system. And we have improved previous TLCS with combination of the iterated improved reduced system method (IIRS) to increase accuracy of the higher modes intermediate range. In this study, we apply previous improved TLCS to multi-level sub-structuring scheme. In the first step, the global system is recursively partitioned into a hierarchy of sub-domain. In second step, each uncoupled sub-domain is condensed by the improved TLCS. After assembly process of each reduced sub-eigenvalue problem, eigen-solution is calculated by Lanczos method (ARPACK). Finally, Numerical examples demonstrate performance of proposed method.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.939-946
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• 2005

The stiffness properties of heterogeneous concrete materials and their degradation were investigated at different-levels of observations with aids of the opportunities and limitations of multi-resolution wavelet analysis. The successive Haw transformations lead to a recursive separation of the stiffness properties and the response into coarse-and fine-scale features. In the limit, this recursive process results in a homogenization parameter which is an average measure of stiffness and strain energy capacity at the coarse scale. The basic concept of multi-resolution analysis is illustrated with one and two-dimensional model problems of a two-phase particulate composite representative of the morphology of concrete materials. The computational studies include the meso-structural features of concrete in the form of a hi-material system of aggregate particles which are immersed in a hardened cement paste taking due to account of the mismatch of the two elastic constituents.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.68-74
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• 1998

This paper deals with a model reduction problem for the linear systems with state delay. After defining the controllability/observability Gramians, the concept of a balanced model for the linear systems with state delay is introduced. Based on solutions of linear matrix inequalities, the model reduction method with guaranteed error bounds is developed. In order to demonstrate the efficacy of teh suggested method, a numerical example is also performed.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.2
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• pp.29-36
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• 2004

This paper deals with a fractional model reduction for linear systems with time varying delayed states. A contractive coprime factorization of linear time delayed systems is defined and obtained by solving linear matrix inequalities. Using generalize controllability and observability gramians of tile contractive coprime factor, a balanced state space realization of the system is derived. The reduced model will be obtained by truncating states in the balanced realization and an upper bound of model approximation error is also presented. In order to demonstrate efficacy of the suggested method, a numerical example is illustrated.