• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.651-659
• /
• 2002

Component Mode Synthesis (CMS) is a dynamic substructuring technique to get an approximate eigensolutions of large degree-of-freedom structures divisible into several components. But, In practice. most of large structures are modeled by different teams of engineers. and their respective finite element models often require different mesh resolutions. As a result, the finite element substructure models can be non-conforming and/or incompatible. In this work, A hybrid version of component mode synthesis using a localized lagrange multiplier to treat the non-conforming mesh problem was derived. Evolution Strategies (ESs) is a stochastic numerical optimization technique and has shown a robust performance for solving deterministic problems. An ESs conducts its search by processing a population of solutions for an optimization problem based on principles from natural evolution. An optimization example for raising the first natural frequency of a plate structure using beam stiffeners was presented using hybrid component mode synthesis and robust evolution strategies (RES) optimization technique. In the example. the design variables are the positions and lengths of beam stiffeners.

• Journal of Power Electronics
• /
• 제18권4호
• /
• pp.1037-1050
• /
• 2018

This paper presents a novel reconfigurable selective harmonic elimination technique to control harmonics over a wide range of Modulation Indexes (MI) in Multi-Level Inverter (MLI). In the proposed method, the region of the MI is divided into various sectors and expressions are formulated with different switching patterns for each of the sectors. A memetic BBO-MAS (Biogeography Based Optimization - Mesh Adaptive direct Search) optimization algorithm is proposed for solving the Selective Harmonic Elimination - Pulse Width Modulation (SHE-PWM) technique. An experimental prototype is developed using a Field Programmable Gate Array (FPGA) and their FFT spectrums are analyzed over a wide range of MI using a fluke power logger. Simulation and experimental results have validated the performance of the proposed optimization algorithms and the reconfigurable SHE-PWM technique. Further, the sensitivity of the harmonics has been analyzed considering non-integer variations in the magnitude of the input DC sources.

• 전기학회논문지
• /
• 제58권11호
• /
• pp.2286-2291
• /
• 2009

We propose a phase optimization technique for sidelobe suppression in OFDM system. The technique is based on idea that phase shift to some of the transmit symbols within the symbol constellation plane can lead to significant sidelobe suppression. The sidelobes are reduced by optimizing using iterative method the phases of some subcarriers on the left and right hand side of the used OFDM spectrum. The proposed technique requires a small amount of side information that needs to be transmitted. Simulation results show that the proposed technique can reduce the sidelobes by significant amount.

• 한국자동차공학회논문집
• /
• 제12권3호
• /
• pp.51-58
• /
• 2004

Optimization of engine desist and operation parameters using a genetic algorithm was demonstrated for direct injection diesel engine combustion. A micro genetic algorithm and a modified KIVA-3V code were used for the analysis and optimization of the engine combustion. At each generation of the optimization step the micro genetic algorithm generated five groups of parameter sets, and the five cases of KIVA-3V analysis were to be performed either in series or in parallel. The micro genetic algorithm code was also parallelized by using MPI programming, and a multi-CPU parallel supercomputer was used to speed up the optimization process by four times. An example case for a fixed engine speed was performed with six parameters of intake swirl ratio, compression ratio, fuel injection included angle, injector hole number, SOI, and injection duration. A simultaneous optimization technique for the whole range of engine speeds would be suggested for further studies.

• 전기학회논문지
• /
• 제57권5호
• /
• pp.748-754
• /
• 2008

The general capacitor placement problem is a combinatorial optimization problem having an objective function composed of power losses and capacitor installation costs subject to bus voltage constraints. In this paper, a global optimization technique, which employing the chaos search algorithm, is applied to solve optimal capacitor placement problem with reducing computational effort and enhancing global optimality of the solution. Chaos method in optimization problem searches the global optimal solution on the regularity of chaotic motions and easily escapes from local or near optimal solution than stochastic optimization algorithms. The chaos optimization method is tested on 9 buses and 69 buses system to illustrate the effectiveness of the proposed method.

• 한국전산구조공학회논문집
• /
• 제14권4호
• /
• pp.505-513
• /
• 2001

본 연구에서는 지진하중을 받는 철근콘크리트(Reinforced Concrete : RC) 교각의 효율적인 최적설계 알고리즘을 제안하였다. 제안한 RC 교각 최적설계 알고리즘은 효율적인 강도재해석 기법을 기초로 하고 있다. 또한 RC 교각의 특성을 고려하여 제약조건 소거기법과 같은 근사화 기법을 도입 하였다. 기존의 최적설계 방법 비교를 통해 제안한 RC 교각의 최적설계 방법의 효율성과 신뢰성을 비교하였다. 그리고 시방서의 내진 규정에 따른 수치예제를 통하여 제안한 강도재해석기법에 의한 새로운 알고리즘이 기존의 최적설계 방법에 비해 효율성과 신뢰도가 우수하다는 것을 입증하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제37회 추계학술대회논문집
• /
• pp.325-330
• /
• 2011

동익 오버랩은 축류 터빈의 성능향상을 위해 적용되며, 동익의 익단과 익근에 추가적인 높이를 적용함으로써 충분한 유로를 확보할 수 있다. 특히, 초음속 터빈에서는 동익 유로에서 의 질식 가능성을 줄이며, 설계 압력비를 구현할 수 있도록 한다. 하지만 동익 오버랩을 적용하면, 펌핑손실, 확산손실 등의 추가적인 손실이 동반된다. 따라서 터빈 성능향상을 최대화하기 위해 최적화 기법을 적용하였으며, 최적화 과정의 효율성을 위해 근사 최적화 기법을 사용하였다. 설계변수는 동익 오버랩의 형상변수이다. 연구결과를 통해, 최적화된 동익 오버랩에 의한 상당한 터빈 성능향상을 확인할 수 있었다.

• 한국군사과학기술학회지
• /
• 제21권2호
• /
• pp.211-216
• /
• 2018

This paper presents a numerical optimization technique and switching phase control technique aiming at improvement of efficiency of the low voltage BLDC motor. The optimization technique is performed using the generalized sensitivity technique, response surface method(RSM) and sampling minimization technique. In order to minimize current consumption of the BLDC motor, the switching method of the driving device is optimized using RSM with finite element analysis. The ratings of BLDC motor are 50 W, 24 V, 1200 rpm. As optimizing results, the input current is reduced from 2.78 to 2.51 [A] when the switching phase is shifted by -2.65 [DEG_ELC] at the rated driving speed of 1200 [rpm]. It is confirmed that the proposed method reduces the consuming current of the low voltage BLDC motor through switching phase control method using the numerical optimization method.

• 한국지능시스템학회논문지
• /
• 제26권1호
• /
• pp.87-92
• /
• 2016

본 논문에서는 일반적인 신경회로망의 단점인 느린 학습속도를 획기적으로 개선한 네트워크인 Extreme Learning Machine과 전문가들의 언어적 정보들을 기술 할 수 있는 퍼지 이론을 접목한 퍼지 Extreme Learning Machine을 최적화하기 위하여 Particle Swarm Optimization 알고리즘을 이용하였다. 퍼지 Extreme Learning Machine의 활성화 함수를 일반적인 시그모이드 함수를 사용하지 않고, 퍼지 C-Means 클러스터링 알고리즘의 활성화 레벨 함수를 이용하였다. Particle Swarm Optimization 알고리즘과 같은 최적화 알고리즘을 통하여 퍼지 Extreme Learning Machine의 활성화 함수의 파라미터들을 최적화 한다. Particle Swarm Optimization과 같은 최적화 알고리즘을 통한 제안된 모델의 최적화 하고 최적화된 모델의 분류성능을 평가하기 위하여 다양한 머신 러닝 데이터 집합을 사용하여 평가한다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.331-334
• /
• 2003

In the finite element simulation of hot forging processes using hexahedron, remeshing of a flash is very difficult. The mesh compression method is a remeshing technique to construct an effective hexahedral mesh. However, because mesh is distorted during the compression procedure or the mesh compression method, mesh smoothing is necessary to improve the mesh Qualify. in this study, several geometric mesh smoothing techniques and a matrix norm optimization technique are applied and compared which is more adaptive to the mesh compression method.