• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.143-157
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• 1992

For the design of structural systems having the prescribed or optimum dynamic characteristics, some design changes of the initially designed system are required. In these cases, if the sensitivity analysis which can predict the changes of dynamic characteristics due to the changes of design variables is applied, the design changes can be carried out rationally and very efficiently. For many structural systems, it is well known that the analysis by the transfer matrix method(TMM) and the combined finite element-transfer matrix method(FETMM) is more efficient than the analysis by the finite element method. However, most known studies on the sensitivity analysis of structural systems premise using the finite element method. In this paper, the sensitivity analysis methods by the TMM and the FETMM are presented and some numerical investigations on the beam-column with elastically restrained ends and intermediate contraints and the stiffened plate having subsystems are carried out. The results of the numerical examples show good accuracy and computational efficiency of the presented methods, and show that the application of sensitivity analysis in the dynamic characteristic reanalysis give good results within the practically changeable range of design variables.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1099-1107
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• 2013

This study proposes a weight reduction design for urban transit, specifically, a Korean EMU carbody made of aluminum extrusion profiles, according to size optimization and useful material changes. First, the thickness of the under-frame, side-panels, and end-panels were optimized by the size optimization process, and then, the weight of the Korean EMU carbody could be reduced to approximately 14.8%. Second, the under-frame of the optimized carbody was substituted with a frame-type structure made of SMA 570, and then, the weight of the hybrid-type carbody was 3.8% lighter than that of the initial K-EMU. Finally, the under-frame and the roof-panel were substituted with a composite material sandwich to obtain an ultralight hybrid-type carbody. The weight of the ultralight hybrid-type carbody was 30% lighter than that of the initial K-EMU. All the resulting carbody models satisfied the design regulations of the domestic Performance Test Standard for Electrical Multiple Unit.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.135-140
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• 2012

Interior Permanent Magnet Synchronous motors (IPMSM) with concentrated winding are superior to distributed winding in the power density point of view. But it causes huge amount of eddy current losses on the permanent magnet. This paper presents the optimal permanent magnet V-shape on the rotor of an interior permanent magnet synchronous motor to reduce the core losses and improve the performance. Each eddy current loss on permanent magnet has been investigated in detail by using FEM (Finite Element Method) instead of equivalent magnetic circuit network method in order to consider saturation and non-linear magnetic property. Simulation-based design of experiment is also applied to avoid large number of analyses according to each design parameter and consider expected interactions among parameters. Consequently, the optimal design to reduce the core loss on the permanent magnet while maintaining or improving motor performance is proposed by an optimization algorithm using regression equation derived and lastly, it is verified by FEM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.799-806
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• 2004

This paper presents a scheme for finding an optimal combination of design parameters affecting on the handling performance of a large truck using design of experiments. The average of the sum of peak-to-peak roll angles at the first and second part of the double lane is used as an objective function for design of experiments. Six design parameters are selected from all possible parameters affecting on the handling performance. The table of orthogonal arrays is made by 27 times simulations. A computational model of a large truck is developed by MSC/NASTRAN and MSC/ADAMS, and verified the reliability of it with the results of vehicle tests performed in a double lane change course. It is used for the simulations. Analyses of variance and factor effect of the table of orthogonal arrays are performed. This paper proposes an optimal combination of those six design parameters for improving the handling performance of the large truck.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.117-133
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• 2002

열차운영계획은 수송수요 산정, 운행노선계획, 열차시간표 작성 기관차 및 인원의 할당 등 광범위한 내용을 포괄하고 있으나, 본 논문에서는 계획의 초기단계에서 결정 가능한 운행노선계획을 대상으로 범위를 설정하였다. 운영목표에 따른 전략은 사용자, 운영자, 사회전체의 입장에서 고려될 수 있는데, 이러한 전략에 의해 운행 될 수 있는 열차운행패턴을 운영비용의 최소화, 통행시간의 최소화. 운영자 수익의 최대화 모형으로 해결하고자 하였다. 2004년 이후에 운행이 예상되는 고속철도/기존철도는 운영계획의 변경이 예상되는 바, 상기의 목표에 따라 열차운영패턴을 작성하여 개발된 효과척도의 적용을 통해 정책적인 적용가능성을 평가하였으며 기존 계획된 철도청의 운영계획과도 아울러 비교, 최적대안을 선정하였다. 본 고에서는 수리계획모형인 비선형정수계획모형(MINLP)으로서 국내 철도망에 부합하는 운영계획을 작성하였으며, 이에 따른 열차-km는 수익최대화 모형, 인-km는 철도청의 열차운영계획이 가장 많은 것으로 나타났다. 인-hour는 수익 최대화 모형과 통행시간 최소화 모형이 가장 적은 것으로 나타났는데, 이는 장거리 노선의 편성이 증가된 것으로 사료된다. 이러한 결과를 산출함에 있어. 어려운 점은 각 구간의 기하급수적 증가, 결정변수의 초기값 선정 등이 있으나, 그동안 연구된 각종 경험적 기법의 적용과 실제 편성 가능한 변수의 적용을 통해 이를 해결하였다. 추후 설정된 모형의 비교에 적합한 효과척도의 개발과 전국적으로 사례구간의 확장 및 모형의 최적대안 선택 시 효과척도의 가중치에 대한 연구가 필요할 것으로 사료된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.345-352
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• 2014

In this paper, the CAD data for the optimal shape design obtained by isogeometric shape optimization is directly used to fabricate the specimen by using 3D printer for the experimental validation. In a conventional finite element method, the geometric approximation inherent in the mesh leads to the accuracy issue in response analysis and design sensitivity analysis. Furthermore, in the finite element based shape optimization, subsequent communication with CAD description is required in the design optimization process, which results in the loss of optimal design information during the communication. Isogeometric analysis method employs the same NURBS basis functions and control points used in CAD systems, which enables to use exact geometrical properties like normal vector and curvature information in the response analysis and design sensitivity analysis procedure. Also, it vastly simplify the design modification of complex geometries without communicating with the CAD description of geometry during design optimization process. Therefore, the information of optimal design and material volume is exactly reflected to fabricate the specimen for experimental validation. Through the design optimization examples of elasticity problem, it is experimentally shown that the optimal design has higher stiffness than the initial design. Also, the experimental results match very well with the numerical results. Using a non-contact optical 3D deformation measuring system for strain distribution, it is shown that the stress concentration is significantly alleviated in the optimal design compared with the initial design.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.153-162
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• 2013

This paper proposes the most simple method for optimal solution of the transshipment problem. Usually the transshipment problem is solved by direct linear programming or TSM (Transportation Simplex Method). The method using TSM has two steps. First it is to get a initial solution using NCM, LCM, or VAM, second to refine the initial solution using MOD or SSM. However the steps is complex and difficult. The proposed method applies the method that transforms transshipment problem to transportation problem. In the proposed method it simply selects the minimum cost of rows about transportation problem, and then it applies the method that assigns a transported volume as an ascending sort of the costs of rows about the selected costs. Our method makes to be very fast got the initial value. Also we uses the method that controls assignment volume, if a heavy item of cost is assigned to a transported volume and it has a condition to be able to transform to more lower cost. The proposed algorithm simply got the optimal solution with applying to 11 transshipment problem.

• The Journal of Information Systems
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• v.7 no.1
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• pp.23-36
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• 1998

본 연구는 특정 조직의 정보 인프라 개발을 위한 전략적 계획을 수립하기 위해 의 사결정 지원 도구로서 다수 목표 의사결정 모형 (Multiple Objective Decision-Making Model : MODEM), 구체적으로는 목표 계획법(Goal Programming : GP)의 응용을 제시하고 있다. 연구대상 조직은 3년 동안의 정보 인프라 개발 프로젝트를 추진하고 있다. 이러한 특 별 프로젝트는 조직 전체에 궁극적인 통합 정보 기술 서비스를 제공하기 위하여 최고 의사 결정자의 전략적 계획 측면에서 추진되고 있다. 본 연구는 총 8개의 목표가 수립되었고 현 조직 환경하에서 이들 목포들에 대한 우선 순위가 설정되었다. Micro Manager가 본 연구 모형의 실행을 위하여 활용되었고 분석결과 6개의 정보 인프라 프로젝트 중 첫 5개가 실행 되기 위하여 선택되어 졌으며 4개의 네트? 대안 중에서 첫 번째 대안이 최적 대안으로 선 택되었다. 초기 설정 목표들에 대한 우선 순위를 변경시킴으로써 연구 모형의 가변성을 검 토하기 위해 민감도 분석이 실행되었다. 변경된 목표와 우선 순위하에서는 6개의 정보 인프 라 프로젝트 중 3개만이 실행을 위하여 선택되었고 네트? 대안은 첫 번째 대안이 역시 최 적 대안으로 선택되었다. 본 연구 모형은 다수의 서로 상층하는 목표를 가지는 조직 및 이 와 유사한 경영환경에 직면해 있는 전략적 의사결정 수립에 효과적인 방안을 제시할 것이다.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.100-107
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• 2011

One of the important fields for heuristic algorithm is how to balance between Intensification and Diversification. In this paper, we deal with the performance improvement techniques through balance the intensification and diversification in Ant Colony System(ACS) which is one of Ant Colony Optimization(ACO). In this paper, we propose the hybrid searching method between intensification strategy and diversification strategy. First, the length of the global optimal path does not improved within the limited iterations, we evaluates this state that fall into the local optimum and selects the next node using changed parameters in the state transition rule. And then we consider the overlapping edge of the global best path of the previous and the current, and, to enhance the pheromone for the overlapping edges increases the probability that the optimal path is configured. Finally, the performance of Best and Average-Best of proposed algorithm outperforms ACS-3-opt, ACS-Subpath, ACS-Iter and ACS-Global-Ovelap algorithms.

• Journal of Navigation and Port Research
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• v.30 no.10 s.116
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• pp.869-875
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• 2006

This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP(sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using NURBS(Non-Uniform Rational B-Spline) surface patches. To verity the validity of the developed program the numerical calculations for Wigley hull and Series 60( $C_B=0.6$) hull have been performed and the results obtained by the numerical calculations have been compared with the original hulls.