• 대한기계학회논문집A
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• 제24권1호
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• pp.190-195
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• 2000

It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure. Nikolakopoulos et. al. used the intersection point of the superposed contours that correspond to the eigenfrequency caused by the crack presence. However the intersecting point of the superposed contours is not only difficult to find but also incorrect to calculate. A method is presented in this paper which uses optimization technique for the location and depth of the crack. The basic idea is to find parameters which use the structural eigenfrequencies on crack depth and location and optimization algorithm. With finite element model of the structure to calculate eigenfrequencies, it is possible to formulate the inverse problem in optimization format. Method of optimization is augmented lagrange multiplier method and search direction method is BFGS variable metric method and one dimensional search method is polynomial interpolation.

• 한국광학회지
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• 제20권6호
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• pp.319-327
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• 2009

본 논문에서는 다음과 같은 관점의 광각 2군 줌 렌즈 설계를 소개한다. 먼저전역최적화의 개념을 기초설계단계에서 도입하고, 이를 통해 현대의 수많은 데이터들을 체계적으로 계통화하고 단순화할 수 있는 설계방안을 제안한다. 구체적인 방안으로 전역설 계를 위해 전역구조함수라는 새로운 개념의 함수를 도입하였고 단순화시켰으며, 나아가 약간의 대수적인 혹은 수치적인 계산을 통해 전역 해 영역을 구하였다. 전역 해 영역은 전역최적화에 대응되는 개념이고 상용화된 설계프로그램들 보다 더 체계적이고 통찰적인 설계방향을 제시한다.

• 한국정보과학회논문지:시스템및이론
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• 제31권10호
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• pp.543-552
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• 2004

이 논문은 지연 시간 및 화질 제약이 있는 비디오 응용을 위한 에너지 최적화 기법을 제안한다. 이는 두 가지 핵심 기법 - 프레임 생략 기법 및 버퍼링 기법 - 으로 구성되어있다. 버퍼링은 운영 체제 수준에서 유휴 시간 이용률을 증가시키고, 프레임 생략은 응용 수준에서 유휴 시간 자체를 증가시키며, 양쪽 모두 동적 전압 조절 기법의 효과를 향상시킨다. 이 논문에서는 제안한 기법을 적용하기 위해 H.263 부호기 응용을 사용한다. 실험에서는 제안한 기법이 주어진 지연 시간 및 화질 제약을 만족하면서 괄목할 만한 에너지 절감을 얻을 수 있음을 보인다.

• International Journal of Ocean System Engineering
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• 제3권1호
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• pp.1-9
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• 2013

A design procedure for a ship with minimum resistance had been developed using a numerical optimization method called SQP (Sequential Quadratic Programming) combined with computational fluid dynamics (CFD) technique. The frictional resistance coefficient was estimated by the ITTC 1957 model-ship correlation line formula and the wave-making resistance coefficient was evaluated by the potential-flow panel method with the nonlinear free surface boundary conditions. The geometry of the hull surface was represented and modified by B-spline surface modeling technique during the optimization process. The Series 60 ($C_B$=0.60) hull was selected as a parent hull to obtain an optimized hull that produces minimum resistance. The models of the parent and optimized hull forms were tested at calm water condition in order to demonstrate the validity of the proposed methodolgy.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2262-2267
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• 2018

In electric machine design, there is a large computation cost for finite element analyses (FEA) when analyzing nonlinear characteristics in the machine Therefore, for the optimal design of an electric machine, designers commonly use an optimization algorithm capable of excellent convergence performance. However, robustness consideration, as this factor can guarantee machine performances capabilities within design uncertainties such as the manufacturing tolerance or external perturbations, is essential during the machine design process. Moreover, additional FEA is required to search robust optimum. To address this issue, this paper proposes a computationally efficient robust optimization algorithm. To reduce the computational burden of the FEA, the proposed algorithm employs a useful technique which termed static analysis assisted technique (SAAT). The proposed method is verified via the effective robust optimal design of electric machine to reduce cogging torque at a reasonable computational cost.

• The Journal of the Acoustical Society of Korea
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• 제21권2E호
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• pp.63-70
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• 2002

In this paper, an optimization technique for thin walled beams of vehicle body structure is proposed. Stiffness of thin walled beam structure is characterized by the thickness and typical section shape of the beam structure. Approximate functions for the section properties such as area, area moment of inertia, and torsional constant are derived by using the response surface method. The approximate functions can be used for the optimal design of the vehicle body that consists of complicated thin walled beams. A passenger car body structure is optimized to demonstrate the proposed technique.

• 전기학회논문지
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• 제66권7호
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• pp.1078-1082
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• 2017

This paper presents an L1 optimization based filtering technique which effectively eliminates the optical misalignment effects encountered in the squint guidance mode with strapdown seekers. We formulated a series of L1 optimization problems in order to separate the bias and the gradient components from the measured data, and solved them via the alternating direction method of multipliers (ADMM) and sparse matrix decomposition techniques. The proposed technique was able to rapidly detect arbitrary discontinuities and gradient changes from the measured signals, and was shown to effectively cancel the undesirable effects coming from the seeker misalignment angles. The technique was implemented on embedded flight computers and the real-time operational performance was verified via the hardware-in-the-loop simulation (HILS) tests in parallel with the automatic target recognition algorithms and the intra-red synthetic target images.

• 한국안전학회지
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• 제26권4호
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• pp.80-86
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• 2011

Structural optimization algorithm of steel box girder bridges using improved higher-order approximate reanalysis technique is proposed in this paper. The proposed approximation method is a generalization of the convex approximation method. The order of the approximate reanalysis for each function is analytically adjusted in the optimization process. This self-adjusted capability makes the approximate structural analysis values conservative enough to maintain the optimum design point of the approximate problem. The efficiency of proposed optimazation algorithm, compared with conventional algorithm, is successfully demonstrated in the steel box girder bridges. The efficiency and robustness of proposed algorithm is also demonstrated in practical steel box girder bridges.

• Structural Engineering and Mechanics
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• 제62권3호
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• pp.259-272
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• 2017

In this study, recently developed swarm intelligence algorithm called Social Spider Optimization (SSO) approach and its enhanced version of SSO algorithm with spider jump techniques is used to develop a structural optimization technique for steel space structures. The improved version of SSO uses adaptive randomness probability in generating new solutions. The objective function of the design optimization problem is taken as the weight of a steel space structure. Constraints' functions are implemented from American Institute of Steel Construction-Load Resistance factor design (AISC-LRFD) and Ad Hoc Committee report and practice which cover strength, serviceability and geometric requirements. Three steel space structures are optimized using both standard SSO and SSO with spider jump (SSO_SJ) algorithms and the results are compared with those available in the literature in order to investigate the performance of the proposed algorithms.

• 정보처리학회논문지B
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• 제17B권2호
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• pp.115-124
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• 2010

최근 스테레오 정합 기술은 정합하고자 하는 픽셀을 포함한 국부적인(local) 영상의 정합 비용과 시차의 변화 비용을 누적하는 전역적(global)인 방법을 많이 사용하고 있다. 특히 전역적 스테레오 정합에서도 비용누적 (cost accumulation)의 방향을 일반적인 수평방향이 아닌 다수의 방향을 사용하는 연구가 늘고 있다. 본 논문에서는 기존의 스테레오 정합 기술을 다중 방향성 정합 기술로 확장하는 방법을 제안한다. 픽셀의 국부적인 정합 비용은 단순한 NCC (Normalized Cross Correlation)를 사용하였고 전역적 정합 기술의 하나인 정합선 최적화(Scan-line Optimization) 방법을 다중 방향으로 확장하는 기술을 제안하였다. 우선 정합선 최적화를 다중 방향으로 실행한 후 이들 결과를 이용하여 신뢰도가 높은 시차영상 (disparity image)을 획득한다. 반복적인 다중 방향 정합선 최적화 시행 후, 시차영상에서 남은 공백은 홀 복원 방법으로 계산한다. 시차가 구해진 픽셀에 대해서는 신뢰도 점수를 매긴 다음 이 점수를 확산하여 신뢰도 점수 테이블에서 가장 높은 값을 가지는 시차값으로 홀을 복원하였다. 제안하는 기술을 미들버리(Middlebury)의 스테레오 영상을 사용하여 오차를 분석하였다. 기존의 전역적 방법과 제안 기술을 이용하여 시차영상을 계산하고 그 오차를 비교하였다.