• Computers and Concrete
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• 제22권5호
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• pp.493-500
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• 2018

Due to the fact that the ratio of their height to their openings is very large compared to normal beams, there are difficulties in the design and analysis of deep beams, which differ in behavior. In this study, the optimum horizontal and vertical reinforcement diameters of 5 different beams were determined by using genetic algorithms (GA) due to the openness/height ratio (L/h), loading condition and the presence of spaces in the body. In this study, the effect of different mutation operators and improved double times sensitive mutation (DTM) operator on GA's performance was investigated. In the study following random mutation (RM), boundary mutation (BM), non-uniform random mutation (NRM), Makinen, Periaux and Toivanen (MPT) mutation, power mutation (PM), polynomial mutation (PNM), and developed DTM mutation operators were applied to five deep beam problems were used to determine the minimum reinforcement diameter. The fitness values obtained using developed DTM mutation operator was higher than obtained from existing mutation operators. Moreover; obtained reinforcement weight of the deep beams using the developed DTM mutation operator lower than obtained from the existing mutation operators. As a result of the analyzes, the highest fitness value was obtained from the applied double times sensitive mutation (DTM) operator. In addition, it was found that this study, which was carried out using GAs, contributed to the solution of the problems experienced in the design of deep beams.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.115-122
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• 2014

Injection pressure is one of factors that influence part quality. In this paper, injection pressure was minimized by optimizing valve gate locations. In order to perform design optimization, MAPS-3DTM (Mold Analysis and Plastic Solution-3D) was used for injection mold analysis and PIAnOTM (Process Integration, Automation and Optimization) was used as process integration and design optimization. Also we adapted meta models based on design of experiments for efficiency. By using introduced methodology, we were able to obtain a result so that maximum injection pressure reduced by 28% compared to the initial design. And the validity of the proposed method could also be demonstrated.

• 소음진동
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• 제3권4호
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• pp.341-352
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• 1993

Although a frequency analysis by FFT algorithm has been widely used in the vibration community, this approach has somewhat limited features when an analysist want to see the details of frequency trends because FFT shows only energy contents along frequencies. So the concept of instantaneous frequency that represents the dominant frequency component at each time needs to be introduced. In this paper, to get the instantaneous frequency, two methods are used. Methods using Hilbert transform and evolutionary spectrum are those. One of the problems of estimating instantaneous frequency using Hilbert transform is that it is normally very sensitive to signal to noise ratio(SNR) because of the differentiation. Moving window is applied on the estimation of instantaneous frequency, and instantaneous frequency histogram are used to handle this problem and proved to be very effective. Computer simulations for various signals have been done to understand the characteristics of instantaneous frequency. The usefulness of signal analysis using instantaneous frequency was tested by three simple experiments, which were engine experiment, beam experiment, and car door experiment. The instantaneous frequency analysis is found to be a useful technique to analyze the signals that have time varying frequencies.

• 한국항공우주학회지
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• 제32권9호
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• pp.80-87
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• 2004

향후 인공위성의 정밀 자세지향 요구가 매우 높아짐에 따라 궤도상의 위성에서 발생하는 고주파 진동인 지터 (Jitter) 의 능동적인 재어가 중요한 문제로 대두되고 있다 . 지터는 탑재체의 성능을 저하시키는 주요 요인이다. 지난 10년간 수동식 및 능동식의 지터 제어 방법이 연구되어 왔다. 본 연구에서는 모텔 장치에 대한 능동식의 지터 분리에 대한 기법을 소개하기로 한다. 모델 장치는 피드백 제어의 원리를 기반으로 3 자유도의 운동을 통해 능동적인 제어가 가능하게 해준다. 이를 위해 시스템의 수학적 모델링을 수행하고 확보된 모델은 기본적인 제어기 설계에 이용된다. 설계된 제어법칙은 시뮬레이션을 통해 그 성능을 검증하도록 한다.

• 한국유체기계학회 논문집
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• 제16권6호
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• pp.32-39
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• 2013

In the present study, three-dimensional aerodynamic optimization of high pressure turbine nozzle for turbofan engine was performed. For this, Kriging surrogate model was built and refined iteratively by supplying additional experimental points until the surrogate model and CFX result has effective difference on objective function. When the surrogate model satisfied this reliability condition and developed enough, optimum point was investigated. Commercial program PIAnO was used for optimization process and evolutionary algorithm was used for searching optimum point. As a result, difference between estimated value from Kriging surrogate model and CFD result converges within 0.01% and the optimized nozzle shape has 0.83% improved aerodynamic efficiency.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 춘계학술대회 학술발표 논문집
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• pp.126-130
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• 2001

In this paper, we propose the design methodology of target tracking system using fuzzy basis function expansion (FBFE) based on virus evolutionary genetic algorithm(VEGA). In general, the objective of target tracking is to estimate the future trajectory of the target based on the past position of the target obtained from the sensor. In the conventional and mathematical nonlinear filtering method such as extended Kalman filter (EKF), the performance of the system may be deteriorated in highly nonlinear situation. To resolve these problems of nonlinear filtering technique, by appling artificial intelligent technique to the tracking control of moving targets, we combine the advantages of both traditional and intelligent control technique. In the proposed method, after composing training datum from the parameters of extended Kalman filter, by combining FBFE, which has the strong ability for the approximation, with VEGA, which prevent GA from converging prematurely in the case of lack of genetic diversity of population, and by identifying the parameters and rule numbers of fuzzy basis function simultaneously, we can reduce the tracking error of EKF. Finally, the proposed method is applied to three dimensional tracking problem, and the simulation results shows that the tracking performance is improved by the proposed method.

• 천문학회보
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• 제39권1호
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• pp.33.2-33.2
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• 2014

Halo merger trees are essential backbones of semi-analytic models for galaxy formation and evolution. Recent studies have pointed out that extracting merger trees from numerical simulations of structure formation is non-trivial; different algorithm can give differing merger histories. Thus they should be carefully understood before being used as input for models of galaxy formation. As one of the projects proposed in the SUSSING MERGER TREES Workshop, we investigate the impact of different halo merger trees on a semi-analytic model. We find that the z = 0 global galaxy properties in our model show differences between trees when using a common parameter set, but that these differences are not very significant. However, the star formation history of the Universe and the properties of satellite galaxies can show marked differences between trees with different methods for constructing a tree. Calibrating the SAM for each tree individually to the empirical data can reduce the discrepancies between the z = 0 global galaxy properties, however this is at cost of increasing the differences in evolutionary histories of galaxies. Furthermore, the underlying physics implied can vary, resulting in key quantities such as the supernova feedback efficiency differing by factors of 2. Such a change alters the regimes where star formation is primarily suppressed by supernovae. Therefore, halo merger trees extracted from a common halo catalogue using different, but reliable, algorithms can result in a difference in the semi-analytic model, however, given the enormous uncertainties in galaxy formation physics, these are not necessarily significant.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.11-24
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• 2017

The present work focuses multi-objective optimization of blade sweep for a Wells turbine. The blade-sweep parameters at the mid and the tip sections are selected as design variables. The peak-torque coefficient and the corresponding efficiency are the objective functions, which are maximized. The numerical analysis has been carried out by solving 3D RANS equations based on k-w SST turbulence model. Nine design points are selected within a design space and the simulations are run. Based on the computational results, surrogate-based weighted average models are constructed and the population based multi-objective evolutionary algorithm gave Pareto optimal solutions. The peak-torque coefficient and the corresponding efficiency are enhanced, and the results are analysed using CFD simulations. Two extreme designs in the Pareto solutions show that the peak-torque-coefficient is increased by 28.28% and the corresponding efficiency is decreased by 13.5%. A detailed flow analysis shows the separation phenomena change the turbine performance.

• 한국컴퓨터그래픽스학회논문지
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• 제15권4호
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• pp.13-21
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• 2009

레벨디자인은 게임 개발에 있어 가장 중요한 부분 중 하나이지만, 많은 게임 내 구성 요소가 복합적으로 영향을 미치어 최적의 조합을 찾기가 어려운 문제이다. 본 논문에서는 유전자 알고리즘을 사용하여 범용적인 게임 레벨 생성을 위한 방법을 새로이 제안한다. 제안된 시스템을 통해 게임 디자이너는 단순화된 목표 수치 입력만으로도 다양한 게임 구성 요소로 이루어진 레벨을 근사화시켜 생성할 수 있게 된다. 이는 게임 레벨 디자인 업무 프로세스 상에서 원하는 최적의 레벨을 구성하는데 걸리는 시행 착오 시간을 단축시키는데 도움이 될 수 있다.

• Journal of Power Electronics
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• 제15권1호
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• pp.160-176
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• 2015

This paper presents a method of designing optimal integer- and fractional-order proportional-integral-derivative (FOPID) controllers for a boost converter to gain a set of favorable characteristics at various operating points. A Pareto-based multi-objective optimization approach called strength Pareto evolutionary algorithm (SPEA) is used to obtain fast and low overshoot start-up and dynamic responses and switching stability. The optimization approach generates a set of optimal gains called Pareto set, which corresponds to a Pareto front. The Pareto front is a set of optimal results for objective functions. These results provide designers with a trade-off look-up table, in which they can easily choose any of the optimal gains based on design requirements. The SPEA also overcomes the difficulties of tuning the FOPID controller, which is an extension to the classic integer-order PID controllers and potentially promises better results. The proposed optimized FOPID controller provides an excellent start-up response and the desired dynamic response. This paper presents a detailed comparison of the optimum integer- and the fractional-order PID controllers. Extensive simulation and experimental results prove the superiority of the proposed design methodology to achieve a wide set of desired technical goals.