• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.371-374
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• 2012

본 연구는 "사이클론과 관성충돌 및 백필터의 제진원리를 일체화한 고효율 멀티 제진시스템의 최적화 설계를 위한 수치 해석적 연구(I) : 집진기 입구 최적화 설계"에 이은 일련의 연구로서 앞선 연구에서 도출된 사이클론부 하단 벤츄리(Venturi)에서의 강한 하향 기류의 가속에 따른 분진 재비산 가능성에 대한 추가적 검토를 위한 연구이다. 사이클론부를 통과한 기류가 상향 흐름으로 방향을 전환할때 좀 더 가속시켜 빠르게 곡률반경을 형성하여 조대 입자의 분리를 극대화시키기 위한 목적으로 사이클론부 하단을 벤츄리 형상으로 설계하였으나, 유동장 분석 결과 벤츄리를 통과한 처리가스 흐름이 가속되면서 호퍼 하단까지 약 4~5 m/s의 강한 하향 흐름을 형성하고 호퍼 하부의 말단 부근에서 상향 흐름으로 방향 전환을 하고 있는 것으로 예측됨에 따라 설계 의도와는 달리 벤츄리 설치시 호퍼 하단에 포집된 분진의 재비산을 예방하는데는 크게 역할을 하지 못하는 것으로 나타났다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.135-142
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• 2008

This study is concerned with the optimum design of LB-Deck plate girder bridge. The optimizing problems of the composite bridge are formulated with objective functions and constraints. The objective functions are formulated as the total cost of the concrete deck and steel girder construction and the constraints are derived by criteria with respect to the Korean Highway bridge design. The optimizing algorithm using SUMT for optimum design of the Simple span, 2-Span, 3-span LB-deck plate and general RC-steel composite girder bridges (L=60m) which act live load(DB24). And their optimum numerical results are compares and analyzed to examine the possibility of optimization, the application and convergency of this optimizing algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.975-981
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• 2013

A robust optimization is only one of the ways to minimize the effects of variances in design variables on the objective functions at the preliminary design stage. To predict the variances and to formulate the probabilistic constraints are the most important procedures for the robust optimization formulation. Though several methods such as the process capability index and the six sigma technique were proposed for the prediction and formulation of the variances and probabilistic constraints, respectively, there are few attempts using a percent defective which has been widely applied in the quality control of the manufacturing process for probabilistic constraints. In this study, the robust optimization for a lower control arm of automobile vehicle was carried out, in which the design space showing the mean and variance sensitivity of weight and stress was explored before robust optimization for a lower control arm. The 2nd order Taylor expansion for calculating the standard deviation was used to improve the numerical accuracy for predicting the variances. Simplex algorithm which does not use the gradient information in optimization was used to convert constrained optimization into unconstrained one in robust optimization.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.729-740
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• 1994

In the shape optimal design based on h-version of FEM, the ideal mesh for the initial geometry most probably will not be suitable for the final analysis. Thus, it is necessary to remesh the geometry of the model at each stage of optimization. However, the p-version of FEM appears to be a very attractive alternative for use in shape optimization. The main advantages are as follows; firstly, the elements are not sensitive to distortion for interpolation polynomials of order $p{\geq}3$; secondly, even singular problems can be solved more efficiently with p-version than with the h-version by proper mesh design; thirdly, the initial mesh design are identical. The 2-D p-version model for shape optimization is presented on the basis of Bezier's curve fitting, gradient projection method, and integrals of Legendre polynomials. The numerical results are performed by p-version software RASNA.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.495-503
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• 2001

In a functionally graded materials(FGM), two constituent material particles are mixed up according to a specific volume fraction distribution so that its thermoelastic behavior is definitely characterized by such a material composition distribution. Therefore, the designer should determine the most suitable volume fraction distribution in order to design a FGM that optimally meets the desired performance against the given constraints. In this paper, we address a numerical optimization procedure, with employing interior penalty function method(IPFM) and FDM, for optimizing 2D volume fractions of heat-resisting FGMs composed of metal and ceramic. We discretize a FGM domain into finite number of homogenized rectangular cells of single design variable in order for the optimization efficiency. However, after the optimization process, we interpolate the discontinuous volume fraction with globally continuous bilinear function in order to enforce the continuity of volume fraction distributions.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.23-23
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• 2020

하구 관측은 조사 방법 및 주기에 따라 크게 두 가지로 구분되는데, 첫째는 현장에서 직접 주기적으로 자료를 수집하는 정기 현장관측과 다른 하나는 고정된 지점에 관측소를 설치하여 실시간으로 연속된 자료를 수집하는 실시간 관측으로 분류된다. 본 연구는 하구 관측망 체계를 확립하기 위한 기초 연구로서 금강하구역을 대상으로 모의된 수치 모델 자료를 이용하여 관측망을 설계하기 위한 대표 모니터링 지표를 선정하고, 이를 기반으로 관측 지점을 설계하기 위한 전략을 제시하였다. 대표 모니터링 지표는 실제 현장에서 일반적으로 취득할 수 있는 6가지 항목(수온, 염분, 용존산소, 클로로필a, 총질소, 총인)을 대상으로 EOF 분석을 실시하여 해역의 시공간 분포를 대표할 수 있다고 판단되는 2개의 항목을 선정하였다. 대표 모니터링 지점은 2개의 대표 모니터링 지표에 대한 고유 벡터 사이의 각도를 벡터의 내적으로 계산하고 이를 설계변수로 활용하여 도식최적화 기법을 통해 각 모니터링 항목들에 대한 공간 분포를 가장 잘 재현해 낼 수 있는 지점의 개수와 위치를 선정하였다. 선정된 모니터링 지점들을 이용하여 재구성된 공간 분포를 참값(수치모델)과 비교하여 통계적 적정성 여부를 평가하였으며, 이를 통해 금강하구의 대표 모니터링 지점들을 도출 해 내었다. 금강하구의 정기 현장 관측에 대한 대표 모니터링 지점은 7개로 선정되었으며, 이들은 6가지 관측 항목들에 대해서 매우 높은 공간분포 재현율을 확보할 수 있음을 확인하였다. 또한, 담수가 비정기적으로 방류되는 금강하구 시스템의 지역적 특성에 대한 시계열 정보를 연속적으로 가장 잘 취득할 수 있는 실시간 관측소 설치 영역을 결정하기 위하여, 7개의 대표 모니터링 지점에서의 시계열 정보를 금강하구둑 전면과 외해의 시계열 정보와 비교분석하여 설치가능 지점을 영역으로 제언하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.27-37
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• 1993

An efficient method to solve the minimum weight design problem for frame structures subjected to stress and displacement constraints is presented. The different cross-sectional shapes are conside red in order to apply engineering design in which usually required custom fabrication. To increase the efficiency of the optimization process, the structural response quantities(nodal forces, displacements) are linearized with respect to cross-sectional properties or their reciprocal, based on first order Taylor series expansion, while cross-sectional dimensions are considered as design variables. Numerical examples are performed and compared with other methods to demonstrate the efficiency and reliability of approximation method for frame structural optimization with different cross-sectional shapes. It is shown that the number of finite element analysis is greatly reduced and it leads to a highly efficient method of optimization of frame structures.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.442-445
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• 2004

본 논문은 유전자 기반 퍼지다항식 뉴럴네트워크(Genetic based fuzzy polynomial neural networks： gFPNN)를 제안한다. gFPNN 구조는 퍼지집합을 기반으로 설계되며, 유전자 알고리즘에 의해 구조 및 파라미터를 최적화한 구조이다. 퍼지집합을 기반으로 설계되어진 퍼지뉴럴네트워크는 간략추론 구조와 선형추론 구조로 설계된다. 본 논문에서는 간략추론 및 선형추론 구조를 통합 및 확장한 퍼지다항식 뉴럴네트워크를 설계한다. 이 구조는 연결가중치를 이용하여 회귀다항식을 네트워크 구조로 표현하며, 간략추론(Type 0), 선형추론(Type 1), 회귀다항식추론(Type 2)을 모두 포함한다. 또한 퍼지규칙 후반부의 다항식 차수를 각 규칙에 대해 다르게 선택할 수 있으며, 일률적인 형식의 구조를 벗어나 주어진 시스템의 특성에 따라 유연한 구조를 설계할 수 있도록 한다. 여기에 더하여, 네트워크 구조와 파라미터 동조에 유전자 알고리즘을 적용하며, 구조와 파라미터 동정에 대한 효율적인 방법을 논의한다. 제안된 모델의 평가를 위해 수치예제를 이용한다.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.467-474
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• 2014

Preliminary design in chemical process furnishes economic feasibility through calculation of both mass balance and energy balance and makes it possible to produce a desired product under the given conditions. Through this design stage, the process possesses unchangeable characteristics, since the materials, reactions, unit configuration, and operating conditions were determined. Unique characteristics could be very economic, but it also implies various potential risk factors as well. Therefore, it becomes extremely important to design process considering both economics and safety by integrating process simulation and quantitative risk analysis during preliminary design stage. The target of this study is LNG liquefaction process. By the simulation using Aspen HYSYS and quantitative risk analysis, the design variables of the process were determined in the way to minimize the inherent explosion risks and operating cost. Instead of the optimization tool of Aspen HYSYS, the optimization was performed by using stochastic optimization algorithm (Covariance Matrix Adaptation-Evolution Strategy, CMA-ES) which was implemented through automation between Aspen HYSYS and Matlab. The research obtained that the important variable to enhance inherent safety was the operation pressure of mixed refrigerant. The inherent risk was able to be reduced about 4~18% by increasing the operating cost about 0.5~10%. As the operating cost increases, the absolute value of risk was decreased as expected, but cost-effectiveness of risk reduction had decreased. Integration of process simulation and quantitative risk analysis made it possible to design inherently safe process, and it is expected to be useful in designing the less risky process since risk factors in the process can be numerically monitored during preliminary process design stage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.7-17
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• 1990

The objective of this paper is to provide a method of optimizing are as of the members as well as shape of both truss and arch structures. The design process includes satisfaction of stress and Euler buckling stress constraints for truss and combined stress constraints for arch structures. In order to reduce the number of detailed finite element analysis, the Force Approximation Method is used. A finite element analysis of the initial structure is performed and the gradients of the member end forces are calculated with respect to the areas and nodal coordinates. The gradients are used to form an approximate structural analysis based on first order Taylor series expansions of the member end forces. Using move limits, a numerical optimizer minimizes the volume of the structure with information from the approximate structural analysis. Numerical examples are performed and compared with other methods to demonstrate the efficiency and reliability of the Force Approximation Method for shape optimization. It is shown that the number of finite element analysis is greatly reduced and that it leads to a highly efficient method of shape optimization of structures.