• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.581-586
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1110-1118
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff' s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• 대한기계학회논문집A
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• 제31권3호
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• pp.355-364
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• 2007

Multidisciplinary design optimization based on independent subspaces (MDOIS) is a simple and practical method that can be applied to the practical engineering MDO problems. However, the current version of MDOIS does not handle the common design variables. A new version of MDOIS is proposed and named as MDOIS/2006. It is a two-level MDO method while the original MDOIS is a single-level method. At first, system analysis is performed to solve the coupling in the analysis. If the termination criteria are not satisfied, each discipline solves its own design problem. Each discipline in the lower level solves the problem with common design variables while they are constrained by equality constraints. In the upper level, the common design variables of related disciplines are determined by using the optimum sensitivity of the objective function. To validate MDOIS/2006, mathematical problem and NASA test bed problem are solved. The results are compared with those from other MDO methods. Finally, MDOIS/2006 is applied to flow patterner design and shows that it can be successfully applied to the practical engineering MDO problem.

• 대한전기학회논문지
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• 제38권11호
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• pp.861-869
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• 1989

본 논문에서는 폰트라이긴의 최대원리를 이용한 가압경수형 원자로(PWR)의 부하추종 운전시 제논진동 최적화 문제가 제시되었다. 최적화 모델은 2차 목적함수를 갖고 있는 최적 추적제어문제로 정식화 하였으며, 1군 확산방정식과 제논-아이오다인 동특성 방정식을 등호 제약조건으로 고려하였다. 최적화 모델에 최대원리를 적용하므로서, 문제는 제약조건이 없는 단일시간 문제로 분리되었으며, 분리된 부 문제는 공액 경사법을 이용하여 최적화 하였다. 계산결과는 제논진동이 최소화되어 원자로가 규정된 출력분포를 유지하면서 전력계총에서 요구하는 출력을 잘 추종 하였다.

• 한국항공우주학회지
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• 제41권4호
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• pp.268-274
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• 2013

항공기 날개 앞전의 레이더흡수구조 최적화를 위한 목적함수를 정의하였으며, 유전체로 구성된 단층형 레이더흡수구조를 설계하였다. 설계변수는 흡수체의 복소유전율이며 반사계수와 레이더반사면적을 각각 목적함수로 사용하였다. 반사계수는 계산이 간단하여 최적화에 효과적으로 사용될 수 있지만 대상물을 평판형태로 가정하기 때문에 구조물의 형상을 충분히 반영하기 어렵다. 반면 레이더반사면적은 형상을 충분히 반영할 수 있지만 계산에 많은 시간이 요구된다. 반사계수는 전송선로이론을 통하여 계산하였으며, 레이더반사면적은 형상조건을 반영하기 위하여 날개 앞전 부분모델에 대해 물리광학법을 사용하여 평가하였다. 최적설계는 유전자알고리즘을 사용하였고, 설계된 레이더흡수구조를 날개 앞전에 적용하여 레이더반사면적을 계산함으로써 레이더흡수 성능을 확인하였다.

• 지식경영연구
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• 제21권1호
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• pp.27-40
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• 2020

Response surface methodology (RSM) empirically studies the relationship between a response variable and input variables in the product or process development phase. The ultimate goal of RSM is to find an optimal condition of the input variables that optimizes (maximizes or minimizes) the response variable. RSM can be seen as a knowledge management tool in terms of creating and utilizing data, information, and knowledge about a product production and service operations. In the field of product or process development, most real-world problems often involve a simultaneous consideration of multiple response variables. This is called a multiple response surface (MRS) problem. Various approaches have been proposed for MRS optimization, which can be classified into loss function approach, priority-based approach, desirability function approach, process capability approach, and probability-based approach. In particular, the loss function approach is divided into univariate and multivariate approaches at large. This paper focuses on the univariate approach. The univariate approach first obtains the mean square error (MSE) for individual response variables. Then, it aggregates the MSE's into a single objective function. It is common to employ the weighted sum or the Tchebycheff metric for aggregation. Finally, it finds an optimal condition of the input variables that minimizes the objective function. When aggregating, the relative weights on the MSE's should be taken into account. However, there are few studies on how to determine the weights systematically. In this study, we propose an interactive procedure to determine the weights through considering a decision maker's preference. The proposed method is illustrated by the 'colloidal gas aphrons' problem, which is a typical MRS problem. We also discuss the extension of the proposed method to the weighted MSE (WMSE).

• 융합신호처리학회논문지
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• 제9권1호
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• pp.39-45
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• 2008

WDM 네트워크는 높은 전송속도와 낮은 지연시간으로 메트로폴리탄 네트워크뿐만 아니라 최근 기가비트 이더넷 등을 이용하여 근거리 망에서도 많은 연구가 진행되어 왔다. 네트워크의 성능은 네트워크 구조의 파라미터 값들과 사용되는 Medium Access Control 프로토콜의 파라미터 값들에 많이 의존한다. 또한 네트워크 효율성과 지연시간은 주로 상반된 관계를 보여 한쪽의 희생이 불가피 하였다. 네트워크를 효율적으로 운용하기 위해서는 효율성과 지연시간이라는 성능의 최적값을 찾아야 상황에 맞게 운용할 수 있다. 본 논문에서는 Arrayed Waveguide Grating (AWG) 기반의 성형 WDM 네트워크상에서 효율성의 최대화와 지연시간의 최소화라는 두 개의 서로 상반된 목적 함수를 유전자 알고리즘 기반의 방법론을 이용하여 파레토 최적화 곡선이라는 최적의 값들을 찾아내었다. 이를 이용하여 구한 최적의 네트워크 구성을 위한 파라미터 값들과 MAC 프로토콜의 파라미터 값들을 이용하여 상황에 따른 최적의 네트워크 성능을 유추할 수 있게 되었다. 본 논문에 사용된 유전자 알고리즘을 이용한 최적화 방법은 이와 유사한 상반된 목적 함수를 갖는 네트워크의 성능을 최적화하는데 사용필 수 있을 것이다.

• Korean Chemical Engineering Research
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• 제56권1호
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• pp.29-41
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• 2018

공비점이 존재하거나 상대휘발도 차이가 적은 2성분 혼합물은 단일 증류탑으로 분리하기 어렵다. 이때 혼합물에서 분리가 어려운 영역을 투과증발막을 사용하여 분리하면 효율적인 공정을 설계할 수 있다. 본 연구에서는 물-유기용매 혼합물을 분리하기 위한 증류-투과증발막 혼성공정을 제시하고, 물-초산 혼합물과 물-에탄올 혼합물의 분리공정을 각각 모사하였다. 증류탑 상부 흐름이 친수성 막을 통과하여 물을 높은 순도로 분리하는 공정을 모사하였다. 실험과 문헌에서 얻은 친수성 막의 투과도를 토대로 막 모델을 만들어 막 면적을 계산하였다. 제시한 공정의 최적화를 위해, 목적함수를 연간 총 비용으로 정하고 주요 설계 변수들을 최적화 변수로 하여 최적화 문제를 구성하였다. 또한, 혼성공정의 각 최적화 변수의 변화에 따른 목적함수 값의 변화 추세를 나타내고 최적화 변수를 최적점에 가까운 값으로 쉽게 추측할 수 있는 방법을 제안하였다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.179-190
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• 2010

This paper describes a new stochastic heuristic algorithm in engineering problem optimization especially in power system applications. An improved particle swarm optimization (PSO) called adaptive particle swarm optimization (APSO), mixed with simulated annealing (SA), is introduced and referred to as APSO-SA. This algorithm uses a novel PSO algorithm (APSO) to increase the convergence rate and incorporate the ability of SA to avoid being trapped in a local optimum. The APSO-SA algorithm efficiency is verified using some benchmark functions. This paper presents the application of APSO-SA to find the optimal location, type and size of flexible AC transmission system devices. Two types of FACTS devices, the thyristor controlled series capacitor (TCSC) and the static VAR compensator (SVC), are considered. The main objectives of the presented method are increasing the voltage stability index and over load factor, decreasing the cost of investment and total real power losses in the power system. In this regard, two cases are considered: single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC). Using the proposed method, the locations, type and sizes of FACTS devices are obtained to reach the optimal objective function. The APSO-SA is used to solve the above non.linear programming optimization problem for better accuracy and fast convergence and its results are compared with results of conventional PSO. The presented method expands the search space, improves performance and accelerates to the speed convergence, in comparison with the conventional PSO algorithm. The optimization results are compared with the standard PSO method. This comparison confirms the efficiency and validity of the proposed method. The proposed approach is examined and tested on IEEE 14 bus systems by MATLAB software. Numerical results demonstrate that the APSO-SA is fast and has a much lower computational cost.

• 대한전기학회논문지
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• 제37권5호
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• pp.272-281
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• 1988

The problem of optimal transmission system planning is to find the most economical locations and time of transmission line construction under the various constraints such as available rights-of-way, finances, the technical characteristics of power system, and the reliability criterion of power supply, and so on. In this paper the constraint of right-of-way is represented as a finite set of available rights-of-way. And the constructed for a unit period. The electrical constraints are represented in terms of line overload and steady state stability margin. And the reliability criterion is dealt with the suppression of failure cost and with single-contingency analysis. In general, the transmission planning problem requires integer solutions and its objective function is nonlinear. In this paper the objective function is defined as a sum of the present values of construction cost and the minimum operating cost of power system. The latter is represented as a sum of generation cost and failure cost considering the change of yearly load, economic dispatch, and the line contingency. For the calculation of operating cost linear programming is adopted on the base of DC load flow calculation, and for the optimization of main objective function nonlinear Branch-and-Bound algorithm is used. Finally, for improving the efficiency of B & B algorithm a new sensitivity analysis algorithm is proposed.