• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.2
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• pp.141-148
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• 1999

변위 근거 유한요소해석을 사용하는 대부분의 위상 최적화 기법은 요소의 안정성 부족으로 인하여 체스판 무늬가 주기적 형태로 반복하여 설계영역 내부에 나타난다. 본 연구에서는 선형요소를 이용하면서 최적화 알고리즘의 안정성에 영향을 주지 않고 간단하게 모든 최적화 알고리즘에 이용 가능한 체스판무늬 형성 방지책을 개발하였다. 본 연구의 체스판무늬 형성 방치책에서는 먼저 각 선형요소를 구성하는 절점들의 부치분율을 설계변수로 선정하고, 요소내부의 부피분율을 설계변수로 표현하기 위한 선형 보간함수로 선형요소들의 형상함수를 선정하였다. 그리고, 설계변수와 등가 재료상수와의 상관 관계식은 평균장 근사이론을 이용하여 균질화된 재료에 벌칙인자가 도입된 관계식을 이용하였다. 또한, 본 연구에서는 순차이차계획법인 PLBA 알고리즘을 이용하여 위상 최적화문제를 해석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.5
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• pp.415-427
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• 1987

This paper presents an experimental model-based vision system which can identify and locate objects in scenes containing multiple occluded parts. The objects are assumed to be rigid and planar parts. In any recognition system the-type of objects that might appear in the image dictates the type of knowledge that is needed to recognize the object. The data is reduced to a sequential list of points or pixels that appear on the boundary of the objects. Next the boundary of the objects is smoothed using a polygonal approximation algorithm. Recognition cosists in finding the prototype that matches model to image. Now the hidden edge is reconstructed by transition model objects into occluded objects. The best match is obtained by optimising some similarity measure.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.304-308
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• 2014

Accurate prediction of peak bloom dates (PBD) of flowering cherry trees is critical for organizing local cherry festivals and other associated cultural and economic activities. A two-step phenology model is commonly used for predicting flowering time depending on local temperatures as a result of two consecutive steps followed by chill and heat accumulations. However, an extensive computation requirement for parameter estimation has been a limitation for its practical use. We propose a sequential parameterization method by exploiting previously unused records of development stages. With an extra constraint formed by heat accumulation between two intervening stages, each parameter can then be solved sequentially in much shorter time than the brute-force method. The result was found to be almost identical to the previous solution known for cherry trees (Prunus ${\times}$ yedoensis) in the Tidal Basin, Washington D.C.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.2
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• pp.135-141
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• 2001

차량 충돌시 자동차의 시트는 승객 및 운전자를 보호해야 한다. 따라서 자동차시트는 충분한 강도를 가져야 하며 이것은 여러 가지 법규에 의해서 제재되고 있다. 물리적 실험 결과가 법규에 정한 규정치를 만족시키기 위해 과대설계 될 수 있다. 그러나 이것은 연비를 줄이기 위한 경량화의 만족이라는 설계요구에 상충한다. 본 논문에서는 헤드레스트 강도시험을 시뮬레이션하고 과대 설계되어 있다고 판단되는 어퍼암을 최적화 모델로 최적설계를 수행하였다. 순차 이차 계획법인 PLBA 알고리즘과 민감도 해석을 위하여 직접근사해석법을 사용하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1151-1157
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• 2009

Ensuring both product quality and reducing material cost are important issue for the design of the piping system of an air conditioner outdoor unit. This paper describes a shape optimization that achieves mass reduction of an air conditioner piping system while satisfying two design constraints on resonance avoidance and the maximum stress in the pipes. In order to obtain optimized design results with various analysis fields considered simultaneously, an automated multidisciplinary analysis system was constructed using PIAnO v.2.4, a commercial process integration and design optimization(PIDO) tool. As the first step of the automated analysis system, a finite element model is automatically generated corresponding to the specified shape of the pipes using a morphing technique included in HyperMesh. Then, the performance indices representing various design requirements (e.g. natural frequency, maximum stress and pipe mass) are obtained from the finite element analyses using appropriate computer-aided engineering(CAE) tools. A sequential approximate optimization(SAO) method was employed to effectively obtain the optimum design. As a result, the pipe mass was reduced by 18 % compared with that of an initial design while all the constraints were satisfied.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.317-324
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• 2008

Optimum design for general or complex structures are required to the need of many numbers of structural analyses. However, current computational environment with single processor is not capable of generating a high-level efficiency in structural analysis and design process for complex structures. In this paper, a virtual parallel computing system communicated by an internet of personal computers and workstation is constructed. In addition, a routine executing Pro/E, ANSYS and optimization algorithm automatically are adopted in the distributed process technique of sequential approximate optimization for the purpose of enhancing the flexibility of application to general structures. By employing the distributed processing technique during structural analysis using commercial application, total calculation time could be reduced, which will enhance the applicability of the proposed technique to the general complex structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.284-290
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• 2014

To successfully explore the moon by lunar lander, it is essential to guarantee the safe landing of lunar lander. Therefore, efficient shock absorption system of lunar lander should be designed in order to reduce landing impact force. Also, for more practical design of lunar lander, it is important to consider the effect of lunar regolith. In the line of thought, finite element model of lunar lander considering the effect of lunar regolith is developed. To reduce landing impact force, optimization of shock absorption system for lunar lander has been carried out. In optimization, sequential approximate optimization method based on meta-model is used. Through the result of optimization, it is verified that landing impact force on lunar lander can be efficiently reduced by the present optimization procedure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.105-111
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• 2003

Wheel for passenger car support the car weight with tires, and they transmit rolling and braking power into the ground. Whittling away at wheel weight is more effective to boost fuel economy than lighting vehicle body structure. A shape of hole in disk is optimized for minimizing the weight of steel wheel. Pro/ENGINEER program is used for formulating the design model, and ANSYS package is selected for analyzing the design model. It has difficulties to interface these commercial software directly. For Combining both programs, response surface methodology is applied to construct approximation functions for maximum stresses and maximum displacements are obtained by full factorial design of five levels. This steel wheel is modeled in 14-inch diameter of rim, and wide parameter of hole in disk is only selected as design variable for reducing the weight of steel whee. PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm, which used the second-order information in the direction finding problem and uses the active set strategy, is used for solving optimization problems.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.58-63
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• 2005

In order to minimize weight of vehicle seat, an optimum design of aluminum seat is presented while satisfying stress and fatigue life constraints. In this study, the analysis model is validated by comparing it's stress with that of test. Then, two-level orthogonal array is used to estimate the design sensitivity for 7 design variables. Finally, the sequential approximate optimization (SAO) is performed using the constructed RSM models. The approximate RSM models are sequentially updated using the analysis results corresponding to the approximate optimum obtained during the SAO. After 14 analyses, the SAO gives an optimal design that can reduce 16.7$\%$ of weight while increasing 369$\%$ of fatigue life and satisfying stress constraint.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.107-108
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• 2006

This paper shows the design optimization of the paper feeding mechanism under dynamic behavior by using commercial codes of RecurDyn/MTT2D and RecurDyn/AutoDesign which are developed by functionBay, Inc. A virtual mockup for dynamics analysis of the paper feeding mechanism is build on RecurDyn/MTT2D and is simulated. Flexible paper is represented as a series of rigid bars connected by revolute joints and rotational spring dampers. Paper is fed by a contact and friction mechanism on rollers or guides. The slip of the paper and nip force of rollers are measured to estimate the system performance. After a simulation, these performances are automatically send to RecurDyn/AutoDesign which is a sequential approximate optimization tool based on the response surface modeling. RecurDyn/AutoDesign makes the approximate objective function and computes the optimized design points of the design variables and gives them to analysis tool. And then the simulation is repeated with the updated design variables. These processes are repeated until finding a tolerable design optimization. In this paper, a paper feeding mechanism is introduced and it is optimized with the proposed algorithms.