• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.18-24
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• 2003

The design cycle associated with large engineering systems requires an initial decomposition of the complex system into design processes which are coupled through the transference of output data. Some of these design processes may be grouped into iterative sybcycles. Previous researches predifined the numbers of design processes in groups, but these group sizes should be determined optimally to balance the computing time of each groups. This paper proposes adaptive decomposition method, which determines the group sizes and the order of processes simultaneously to raise design efficiency by expanding the chromosome of the genetic algorithm. Finally, two sample cases are presented to show the effects of optimizing the sequence of processes with the adaptive decomposition method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.201-213
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• 2005

The automotive door has a large finite element model in analysis and many design requirements such as stiffness, natural frequency, side intrusion, etc. Thus, various related governing equations should be solved for systematic analysis and design. Because each governing equation has different characteristics, it is almost impossible to solve them simultaneously. Instead, they are separately handled and the analysis results are incorporated into the design separately. Currently, the design is usually conducted by trials and errors with engineering intuition in design practice. In this research, MDO methods are proposed to solve the problems that share design variables in disciplines. The idea is from the Gauss-Seidel type method for multi-discipline analysis. The developed methods show stable convergence and the weight of the door is reduced by fifteen percent.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.822-827
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• 2005

Recently engineering systems problems become quite large and complicated. For those problems, design requirements are fairly complex. It is not easy to design such systems by considering only one discipline. Therefore, we need a design methodology that can consider various disciplines. Multidisciplinary Design Optimization (MDO) is an emerging optimization method to include multiple disciplines. So far, about seven MDO methodologies have been proposed for MDO. They are Multidisciplinary Feasible (MDF), Individual Feasible (IDF), All-at-Once (AAO), Concurrent Subspace Optimization (CSSO), Collaborative Optimization (CO), Bi-Level Integrated System Synthesis (BLISS) and Multidisciplinary Optimization Based on Independent Subspaces (MDOIS). In this research, the performances of the methods are evaluated and compared. Practical engineering problems may not be appropriate for fairness. Therefore, mathematical problems are developed for the comparison. Conditions for fair comparison are defined and the mathematical problems are defined based on the conditions. All the methods are coded and the performances of the methods are compared qualitatively as well as quantitatively.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.547-552
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• 2008

여러 분야를 고려해야 하는 항공기나 자동차와 같은 대형기기의 설계에서 순차적 설계는 효과에 비하여 시간과 비용이 비효율적이며, 이러한 비효율성을 해결하기 위해 다분야 최적설계(MDO) 기법이 필요 하게 되었다. 비행체 설계는 시간이 지날수록 그 중요성이 커지고 있고, 설계 시 설계 전 분야를 통합하며 분석 할 수 있는 통합 환경이 요구되고 있다. MDO 기법을 이용한 비행체 설계는 이기종 분산 컴퓨팅 능력을 제공해야하고 각 분야의 데이터 공유를 통한 효율적 관리 및, 설계 최적화 도출을 제공하며 이기종의 환경을 고려해야 하므로, 분산 컴퓨팅 기술을 요구한다. 그리드 환경은 그리드 미들웨어를 중심으로 많은 분산 컴퓨팅 자원을 효율적으로 활용하고 다양한 분야의 문제들을 풀기 위한 고성능 환경을 제공하는 기술이다. 본 논문에서는 각 설계자원을 통합하기 위해 Globus toolkit ver.4(GT4)를 그리드 미들웨어로 사용하였고, 이들을 쉽고 효율적으로 이용하기 위한 PSE포탈을 제시한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.3 s.234
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• pp.395-402
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• 2005

Recently Multidisciplinary Design Optimization Based on Independent Subspaces (MDOIS), an MDO (multidisciplinary design optimization) algorithm, has been proposed. In this research, an MDO problem is defined for design of a belt integrated seat considering crashworthiness, and MDOIS is applied to solve the problem. The crash model consists of an airbag, a belt integrated seat (BIS), an energy absorbing steering system, and a safety belt. It is found that the current design problem has two disciplines - structural nonlin- ear analysis and occupant analysis. The interdisciplinary relationship between the disciplines is identified and is addressed in the system analysis step in MDOIS. Interdisciplinary variables are belt load and stiffness of the seat, which are determined in system analysis step. The belt load is passed to the structural analysis subspace and stiffness of the seat back frame to the occupant analysis subspace. Determined design vari- ables in each subspace are passed to the system analysis step. In this way, the design process iterates until the convergence criterion is satisfied. As a result of the design, the weight of the BIS and Head Injury Crite- rion (HIC) of an occupant are reduced with specified constraints satisfied at the same time. Since the system analysis cannot be formulated in an explicit form in the current example, an optimization problem is formu - lated to solve the system analysis. The results from MDOIS are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.11-15
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• 2005

Compared with the conventional ground rocket launching, air-launching has many advantages. However, comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. The system design has been performed using two different approaches: the sequential optimization and the multidisciplinary feasible(MDF) optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. MDF optimization shows better result than sequential optimization. As a result of system optimization, a supersonic air launching rocket with total mass of 1244.91 kg, total length of 6.18 m, outer diameter of 0.60 m and the payload mass of 7.5 kg has been successfully designed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.26-32
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• 2005

Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. The system design has been performed using two different approaches: the sequential optimization and the multidisciplinary feasible(MDF) optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. MDF optimization shows better results than the sequential optimization. As a result of system optimization, a supersonic air launching rocket with total mass of 1244.91kg, total length of 6.36m, outer diameter of 0.60m and the payload mass of 7.5kg has been successfully designed.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.322-328
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• 2008

Recently, the rapid progress of Internet and Network affects engineering design environment as well as Business fields to utilize Web technologies to enhance it's competitively in the world. In product development, experts and organizations actually taking part in the design process are often geographically dispersed. Furthermore, different divisions and businesses often have heterogeneous CAD/CAE systems and methods for expressing product data, and addressing this heterogeneity creates additional costs and causes longer development periods. To ensure successful collaboration in the design process, it is therefore imperative that distributed CAD, CAE, and other related systems be managed in an organic and integrated manner from the initial stages of product development. Therefore, this study suggests Web-based MDO(Multidisciplinary Design Optimization) framework to support interfacing and the collective use of design and analysis tools.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.170-175
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• 2001

The design cycle associated with large engineering systems requires an initial decomposition of the complex system into design processes which are coupled through the transference of output data. Some of these design processes may be grouped into iterative subcycles. In analyzing or optimizing such a coupled system, it is essential to determine the best order of the processes within these subcycles to reduce design cycle time and cost. This is accomplished by decomposing large multidisciplinary problems into several multidisciplinary analysis subsystems (MDASS) and processing it in parallel. This paper proposes new strategy for parallel decomposition of multidisciplinary problems to improve design efficiency by using the multiple objective genetic algorithm (MOGA), and a sample test case is presented to show the effects of optimizing the sequence with MOGA.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.60.1-60.1
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• 2011

본 연구에서는 풍력 터빈 블레이드의 다분야 통합 최적 설계를 위하여, 진동하는 비정상 공력하중에 의한 작동 수명을 고려한 최적화 과정을 수행하였다. 최적화 대상으로는 NREL의 1.5MW 급 풍력터빈을 baseline 으로 하였고, NREL의 FAST 프로그램을 이용하여 발전기의 정격 출력 및 블레이드에 작용하는 비정상 공력 하중 특성을 분석하였다. 최적화 수행 시 블레이드 형상의 효율적인 구현을 위해 형상모델링 함수를 이용하여 코드 길이와 트위스트 분포를 모델링하였다. 그리고 상용 MDO Framework 인 Piano를 이용하여 블레이드 루트부의 비정상 공력하중 조건을 완화시키는 최적화 설계를 수행하였다. 정격출력을 유지하면서도 Out of Plain 방향의 하중 조건을 개선하여 보다 긴 작동 수명을 기대할 수 있는 블레이드 형상을 설계하였다.