• Proceedings of the KIEE Conference
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• summer
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• pp.860-862
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• 2004

본 논문에서는 유전알고리즘과 유한요소법을 이용하여 BLDC 전동기의 코깅 토크를 최소화하기 위한 최적화 설계 방법을 제안하였다. 먼저 유전알고리즘을 이용하여 BLDC 전동기의 설계 변수를 추론하고, 유한요소법으로 코깅 토크를 구하였다. 유전알고리즘과 유한요소법을 사용함으로써 BLDC 전동기의 코깅 토크가 최소화 되는 영구자석의 형상을 전 영역에서 빠른 시간내에 구할 수 있었다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.191-196
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• 2015

해상 pedestal 크레인은 각종 운송물을 선박에 싣거나 내리는 해상 운송에 필수적인 장비이다. 따라서 구조적 안전성을 가지는 크레인 설계가 요구된다. 그의 일환으로 수행된 '해상 pedestal 크레인의 설계 개선을 위한 연구'에서는 기존 크레인의 기초 설계에 대해서 구조적 안전성올 평가하여 개선 방안을 제시하였다. 또한 좌굴 안정성 향상을 위한 보강재 설계를 수행하였다. 하지만 상세설계 관점에서 미비한 점이 있어 이를 보완할 필요성이 있다. 안전성 평가를 위해 필요한 응력을 계산하기 위해 EDISON-CSD프로그램을 통해 유한요소모델 해석을 활용한 구조해석을 수행하였다. 효율적인 해석을 위해 상세설계에 필요한 부분영역을 선택하여 모델링 하였으며 전체영역에서의 해석 결과 값을 등가 힘, 등가 모멘트로 환산하여 경계조건으로 부여하였다. 보강재간의 교차점 형상이 안전성에 미치는 영향을 보기위해 stiffener와 diaphragm의 교차점 형상(반원, 정사각형, 사다리꼴)에 따라 안전성 평가를 수행하였고, 안전 여유의 유효한 차이를 보이지 않음을 확인하였다. 평가에 필요한 응력계산을 위해 또한 Diaphragm의 좌굴에 대한 영향을 고려하기 위해 설계 규격 DNV-RP-201 8장(Buckling of girders)을 분석하였고, 안전성 평가에 반영하였다. 또한 실제 현장에서 보편적으로 사용되는 angle 형상 stiffener의 치수 도출을 위해 최적설계를 수행하였고, 모든 설계 제한조건을 만족하면서 최소의 무게를 가지는 합리적인 치수를 도출하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.169-173
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• 2019

In this paper, SAR payload operation mode design method, results and performance analysis results are suggested. To SAR payload design, pramary parameter should be identified and designed. It is designed considering the small satellite of less than 100kg operated in low earth orbit. Also, an antenna structure for small size and light weight is proposed. Performance analysis is performed by applying the design values.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.10
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• pp.68-74
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• 2005

Optimal shape of a typical ramjet intake is examined numerically to maximize the total pressure recovery. A response surface method is introduced to approximately predict its performance with respect to the design parameters over the each design domain. The first deflection angle of ramp, the area of inlet throat, and the diffuser angle are chosen as a design parameter. ANOVA is used to verify the trustability of the achieved response surface. The total pressure recovery of the optimum model, compared to that of the base model, is increased by 36%. The loss of viscosity through the diffuser is estimated less than 5%.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1198-1203
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• 2008

An efficient sequential optimization approach for metamodel was presented by Choi et al [6]. This paper describes a new approach of the multilevel optimization method studied in Refs. [5] and [21-25]. The basic idea is concerned with multilevel iterative methods which combine a descent scheme with a hierarchy of auxiliary problems in lower dimensional subspaces. After fitting a metamodel based on an initial space filling design, this model is sequentially refined by the expected improvement criterion. The advantages of the method are that it does not require optimum sensitivities, nonlinear equality constraints are not needed, and the method is relatively easy to understand and use. As a check on effectiveness, the proposed method is applied to a classical cantilever beam.

• Korean Journal of Optics and Photonics
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• v.9 no.6
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• pp.373-379
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• 1998

A new method is proposed for the design of the dichroic mirrors in 3-LCD projection systems for color separation/composition. Rather than simply basing the color performance cirterion on luminance or chromatic saturation only, the optimum design parameters can be found by maximizing the volume of the perceived color gamut in RLAB color space and related color appearance model and used the linearly approximated spectrum of dichroic mirrors for simplicity and vector space description. By this method, we found optimal half-power wavelengths in dichroic mirrors which maximized our performance criterion.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.251-254
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• 2006

마이크로 흐름센서는 종래의 반도체 집적회로 공정기술을 이용하여 소형으로 제작이 가능하며, 빠른 응답특성을 가지는 장점이 있어 다양한 응용이 기대되고 있다. 본 연구에서는 넓은 흐름의 세기영역에서 정밀한 감도를 가지는 2차원 마이크로 흐름센서를 실리콘 기판위에 설계하여 왔다. 이러한 흐름센서의 정확한 온도특성을 분석하고 이 결과로부터 최적을 온도 감지막 위치를 결정할 필요가 있다. 설계방법으로서 표계산 소프트웨어 Excel을 이용하여 열운송방정식의 차분 방정식을 매크로 기능을 이용하여 적용하고 워크시트 내에서 셀 참조방식을 활용하여 자동 계산을 수행하도록 구현하였다. 본 연구에서는 Excel을 활용한 효율적인 설계방법을 제시하고 하나의 히터와 양측에 한 쌍의 온도 감지막을 가진 마이크로 흐름센서에 대해서 열전달 특성을 계산하고 이로부터 최적을 온도 감지막 위치를 결정할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.45-52
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• 2005

A general approximate optimization technique by sequential design domain(SDD) did not save response values for getting an approximate function in each step. It has a disadvantage at aspect of an expense. In this paper, previous response values are recycled for constructing an approximate function. For this reason, approximation function is more accurate. Accordingly, even if we did not determine move limit, a system is converged to the optimal design. Size and shape optimization using approximate optimization technique is carried out with SDD. Algorithm executing Pro/Engineer and ANSYS are automatically adopted in the approximate optimization program by SDD. Convergence criterion is defined such that optimal point must be located within SDD during the three steps. The PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm is used to solve approximate optimization problems. This algorithm uses the second-order information in the direction finding problem and uses the active set strategy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.155-164
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• 2002

The journal bearings use in machine parts which move relative to each other and those reduce friction and wear of journals. The journal bearings are designed to operate in the hydyodynamic lubrication regime, but elastohydrodynamic lubrication nay occur if the pressures are too high or the running speeds are too low at machine elements. It is the phenomenon that the lubricant film is broken and some parts of surfaces are in rolling contact, so that wear will increase in mixed lubrication regime. The purpose of this study is to minimize the wear rate of journal bearings for extending machine life. The wear mate in mixed lubricated regime is selected as objective function because most of wear of the journal bearings develops in elastohydrodynamic lubrication. The journal bearings we represented by a bearing radius, shaft radius, and bearing width, but the bearing radius only is selected as design variables due to a bearing radius has an influence on friction loss, stability limit velocity, and film parameter, which are used as constraints. For numerical calculation, PLBA, that is a class of the RQP algorithm, is used.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.70-77
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• 1998

A new method is proposed for the design of the dichroic mirrors in 3-LCD projection systems for color separation/composition. Rather than simply basing the color performance criterion on luminance or chromatic saturation only, the optimum design parameters can be found by maximizing the perceived color gamut in a 3-D uniform color space. In this method, the half-power wavelengths were optimized by maximizing the volume of the reproducible color gamut in a CIELUV uniform color space for 2 typical viewing conditions, with proper colorimetric analysis of color reproduction in 3-LCD projection systems.