• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.13.2-13
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• 2003

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.309-312
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• 2002

For the purpose of more effective simulation of the utility interactive WPGS(Wind Power Generation System) the SWRW (Simulation method for WPGS using Real Weather condition) is used in this paper, in which those of three topics for the WPGS simulation. user-friendly method, applicability to grid-connection and the utilization of the real weather conditions, are satisfied. The simulation of the WPGS using the real weather condition including components modeling of wind turbine system is achieved by introducing the interface method of a non-linear external parameter and FORTRAN using PSCAD/EMTDC. The simulations of steady-state and transient-state are performed effectively by the introduced simulation method. The generator output and current supplied into utility can be obtained by the steady-state simulation, and THD can be achieved by analyzing the results as well. The transient - state of the WPGS can be analyzed by the simulation results of over cut-out wind speed.

• Korean Chemical Engineering Research
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• 제59권1호
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• pp.138-151
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• 2021

The effect of a reactant ratio on the growth of a buoyancy-driven instability in an irreversible A+B→C reaction system is analyzed theoretically and numerically. Taking a non-stoichiometric reactant ratio into account, new linear stability equations are derived without the quasi-steady state assumption (QSSA) and solved analytically. It is found that the main parameters to explain the present system are the Damköhler number, the dimensionless density difference of chemical species and the ratio of reactants. The present initial grow rate analysis without QSSA shows that the system is initially unconditionally stable regardless of the parameter values; however, the previous initial growth rate analysis based on the QSSA predicted the system is unstable if the system is physically unstable. For time evolving cases, the present growth rates obtained from the spectral analysis and pseudo-spectral method support each other, but quite differently from that obtained under the conventional QSSA. Adopting the result of the linear stability analysis as an initial condition, fully nonlinear direct numerical simulations are conducted. Both the linear analysis and the nonlinear simulation show that the reactant ratio plays an important role in the onset and the growth of the instability motion.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.257-261
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• 2005

The helicopter system is non-linear and complex. Futhermore, because of absence of accurate mathematical model, it is difficult accurately to control its attitude. therefore, we propose a WAVENET control technique to control efficiently its elevation angle and azimuth one. Wavelet neural network(WAVENET) can construct systematically initial neural network as applying wavelet theory to feedforward network. It is proved through computer simulation that WAVENET has more excellent approximation capability than existing neural network. The simulation results using MATLAB are introduced.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.358-364
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• 1999

A wheel/rail contact module for dynamics analysis of railway vehicles is developed. The developed module is based on non-linear contact and FASTSIM algorithm which calculates contact forces. And the module is incorporated into the general purpose program DADS using user-defined subroutines. The simulation results of this developed program is compared to those of the railway vehicle dynamics analysis program AGEM. Since the module is based on DADS, various simulation environments can be considered.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2142-2153
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• 2014

Linearization of transducer characteristic plays a vital role in electronic instrumentation because all transducers have outputs nonlinearly related to the physical variables they sense. If the transducer output is nonlinear, it will produce a whole assortment of problems. Transducers rarely possess a perfectly linear transfer characteristic, but always have some degree of non-linearity over their range of operation. Attempts have been made by many researchers to increase the range of linearity of transducers. This paper presents a method to compensate nonlinearity of Linear Variable Displacement Transducer (LVDT) based on Extreme Learning Machine (ELM) method, Differential Evolution (DE) algorithm and Artificial Neural Network (ANN) trained by Genetic Algorithm (GA). Because of the mechanism structure, LVDT often exhibit inherent nonlinear input-output characteristics. The best approximation capability of optimized ANN technique is beneficial to this. The use of this proposed method is demonstrated through computer simulation with the experimental data of two different LVDTs. The results reveal that the proposed method compensated the presence of nonlinearity in the displacement transducer with very low training time, lowest Mean Square Error (MSE) value and better linearity. This research work involves less computational complexity and it behaves a good performance for nonlinearity compensation for LVDT and has good application prospect.

• 산업경영시스템학회지
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• 제45권3호
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• pp.40-48
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• 2022

An automated material handling system (AMHS) has been emerging as an important factor in the semiconductor wafer manufacturing industry. In general, an automated guided vehicle (AGV) in the Fab's AMHS travels hundreds of miles on guided paths to transport a lot through hundreds of operations. The AMHS aims to transfer wafers while ensuring a short delivery time and high operational reliability. Many linear and analytic approaches have evaluated and improved the performance of the AMHS under a deterministic environment. However, the analytic approaches cannot consider a non-linear, non-convex, and black-box performance measurement of the AMHS owing to the AMHS's complexity and uncertainty. Unexpected vehicle congestion increases the delivery time and deteriorates the Fab's production efficiency. In this study, we propose a Q-Learning based dynamic routing algorithm considering vehicle congestion to reduce the delivery time. The proposed algorithm captures time-variant vehicle traffic and decreases vehicle congestion. Through simulation experiments, we confirm that the proposed algorithm finds an efficient path for the vehicles compared to benchmark algorithms with a reduced mean and decreased standard deviation of the delivery time in the Fab's AMHS.

• 한국통신학회논문지
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• 제36권3A호
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• pp.189-197
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• 2011

무선 광 통신 시스템에서 고속의 데이터를 전송하기 위한 방법으로 대역 효율이 높은 OFDM(orthogonal frequency division multiplexing) 시스템이 연구되고 있다. OFDM 시스템은 PAPR(peak to average power ratio)이 높고 비선형 에러와 디바이스의 불균형으로 발생하는 ICI(inter channel interference)가 발생한다. 무선 광통신 시스템에서 LED(light emission diode)의 구동 전류에 의하여 구동되는 광 출력 파워는 비선형이며 전송 신호는 왜곡된다. 그러므로 비선형 LED 전달함수와 OFDM 신호에 의한 방사된 광 출력의 수신 성능에 대한 연구가 진행되었다. 비선형 왜곡에 의해 발생하는 효과는 기존의 무선 통신에서 사용되는 OFDM의 비선형 특성과 다르며 BER 성능을 저감시킨다. 본 연구에서는 최근 연구된 LED의 비선형성 전달함수를 적용하며, 비선형 왜곡과 Back-off에 의하여 수신기의 주파수영역에서 진폭 감쇄와 ICI를 발생시키므로, BER 성능을 개선시키기 위한 방법을 제안한다. 먼저 LED의 비선형 왜곡을 감소시키기 위한 새로운 PAPR저감 기법을 제안하며, 또한 수산 성능을 향상시키기 위하여 적응형 채널 추정 방식과 전송된 신호를 사용하여 SNR(signal to power ratio)을 개선하여 BER(bit error rate)을 개선하였다. 제안된 방법들을 시뮬레이션 결과를 통하여 확인한다.

• 한국음향학회지
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• 제40권2호
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• pp.109-120
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• 2021

본 논문은 고밀도 클러터 환경 비선형 표적에 대해서 수동소나 자동표적추적 자료결합 게이트를 강인하게 적용하기 위한 H∞ 놈 기반의 자료결합 게이트 기법을 제안한다. 표적추적을 위한 자료결합 기법은 유효 측정 범위인 유효 게이트 내에 있는 측정치를 자료결합의 후보대상으로 선택한다. 자료결합에서의 유효 게이트 범위가 적정하지 않거나 고밀도 클러터 환경에서 자료결합이 수행되면, 클러터 측정치의 간섭을 더욱 받게 되어 표적추적의 강인성을 유지하기 어렵다. 이러한 문제를 해결하기 위해서, 본 논문은 가우시안 분포 가정 및 추적 오차 공분산 기반의 기존 3-σ 게이트 기법에 H∞ 놈 기반의 이분법 알고리즘을 결합하여 적용한 새로운 게이팅 기법을 제안한다. 제안 기법은 클러터의 간섭을 완화시키고, 비선형 기동표적을 견실하게 추적하게 한다. 해석적인 분석 방법과 수평방위 및 수직방위의 측정치를 모의한 신호를 활용한 시뮬레이션을 통해 자료결합의 강인함이 기존 기법에 대비하여 향상됨을 확인하였다.

• Structural Engineering and Mechanics
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• 제85권4호
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• pp.485-500
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• 2023

The non-linear static analysis of reinforced concrete (RC) structures using the three-dimensional (3D) finite element method is a time-consuming and challenging task. Moreover, this type of analysis encounters numerical problems such as the lack of convergence of results in the stages of growth and propagation of cracks in the structure. The time integration analysis along with the mass scaling (MS) technique is usually used to overcome these limitations. Despite the use of this method in the 3D finite element analysis of RC structures, a comprehensive study has not been conducted so far to assess the effects of the MS method on the accuracy of results. This study aims to evaluate the accuracy of the MS method in the non-linear quasi-static finite element analysis of RC structures. To this aim, different types of RC structures were simulated using the finite element approach based on the implicit time integration method and the mass scaling technique. The influences of effective parameters of the MS method (i.e., the allowable values of increase in the mass of the RC structure, the relationship between the duration of the applied load and fundamental vibration period of the RC structure, and the pattern of applied loads) on the accuracy of the simulated results were investigated. The accuracy of numerical simulation results has been evaluated through comparison with existing experimental data. The results of this study show that the achievement of accurate structural responses in the implicit time integration analyses using the MS method involves the appropriate selection of the effective parameters of the MS method.