• 대한수학회지
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• 제55권1호
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• pp.43-58
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• 2018

In this paper, we study a delayed predator-prey system with Holling type IV functional response incorporating the effect of habitat complexity. The results show that there exist stability switches and Hopf bifurcation occurs while the delay crosses a set of critical values. The explicit formulas which determine the direction and stability of Hopf bifurcation are obtained by the normal form theory and the center manifold theorem.

• 한국소음진동공학회논문집
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• 제24권4호
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• pp.310-316
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• 2014

The location template matching(LTM) method is a technique of identifying an impact location on a structure, and requires a certain measure of similarity between two time signals. In general, the correlation coefficient is widely used as the measure of similarity, while the group delay based method is recently proposed to improve the accuracy of the impact localization. Another possible measure is the frequency response assurance criterion(FRAC), though this has not been applied yet. In this paper, these three different measures of similarity are examined comparatively by using experimental data in order to understand the properties of these measures of similarity. The comparative study shows that the correlation coefficient and the FRAC give almost the same information while the group delay based method gives the shape oriented information that is best suitable for the location template matching method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.506-511
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• 2014

The location template matching (LTM) method is a technique of identifying an impact location on a structure, and requires a certain measure of similarity between two time signals. In general, the correlation coefficient is widely used as the measure of similarity, while the group delay based method is recently proposed to improve the accuracy of the impact localization. Another possible measure is the frequency response assurance criterion (FRAC), though this has not been applied yet. In this paper, these three different measures of similarity are examined comparatively by using experimental data in order to understand the properties of these measures of similarity. The comparative study shows that the correlation coefficient and the FRAC give almost the same information while the group delay based method gives the shape oriented information that is best suitable for the location template matching method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.221-225
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• 2005

This paper proposes a gain scheduled control technique using time-delay for the nonlinear system with plant uncertainties and unexpected disturbances. The time delay-based gain scheduled control depends on a direct estimation of a function representing the effect of uncertainties. The information from the estimation is used to cancel the unknown dynamics and the unexpected disturbances simultaneously. The proposed estimation scheme with a finite convergence time is formulated in order to estimate the unborn scheduling variable variation. In other words, the time delay-based gain scheduled control uses the past observation of the system's response and the control input to directly modify the control actions rather than to adjust the controller gains or to identify system parameters. It has a simple structure so as to minimize the computational burden. The benefits of this proposed scheme are demonstrated in the simulation of an electromagnetic suspension system with plant uncertainties and external disturbances, and the proposed controller is compared with the conventional state feedback controller.

• Structural Engineering and Mechanics
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• 제40권2호
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• pp.233-243
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• 2011

This paper presents a theoretical study of a model predictive control (MPC) strategy employed in semi-active control system with magnetorheological (MR) dampers to reduce the responses of seismically excited structures. The MPC scheme is based on a prediction model of the system response to obtain the control actions by minimizing an objective function, which can compensate for the effect of time delay that occurred in real application. As an example, a 5-story building frame equipped with two 20 kN MR dampers is presented to demonstrate the performance of the proposed MPC scheme for addressing time delay and reducing the structural responses under different earthquakes, in which the predictive length l = 5 and the delayed time step d = 10, 20, 40, 60, 100 are considered. Comparison with passive-off, passive-on, and linear quadratic Gaussian (LQG) control strategy indicates that MPC scheme exhibits good control performance similar to the LQG control strategy, both have better control effectiveness than two passive control methods for most cases, and the MPC scheme used in semi-active control system show more effectiveness and robustness for addressing time delay and protecting structures during earthquakes.

• 한국통신학회논문지
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• 제17권7호
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• pp.758-766
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• 1992

본 논문에서는 표준망 관리 프로토콜인 CMIS/CMIP에서 M-Cancel-Get 서비스를 이용한 트래픽 제어방안을 제시하고 성능분석을 하였다. 복수응답 기능단위를 허용하는 M-Get 서비스는 피 관리시스템의 속성을 검색하는 서비스로서 관리 특성상 일상적이고 대량의 응답을 요구하는 서비스이다. 이때 관리응답은피관리시스템이 네트워크의 상황이나 관리시스템의 상황과 무관하게 전송하게 된다. 이에 대해 관리시스템은 자신이 발생시킨 M-Get 서비스의 취소를 알리는 M-Cancel-Get 서비스를 요청할 수 있다.M-Cancel-Get 서비스를 트래픽 제어를 위해 사용하는 경우, 복수응답 패킷수를 증가시키면서 관리응답 시간에 대해 시뮬레이션을 하여 적정 트래픽 제어 시점을 제안하였다. 그리고 그 결과를 백뷴율로 적용하면서 네트워크 부하에 따른 처리율과 일반 패킷의 평균 지연시간에 대해 분석하였다. 그 결과 본 논문에서 제시한 트래픽 제어변수가 처리율과 평균 지연시간에 있어서 우수함을 알 수 있으며, 특히 일반 트래픽이 차지하는 기본 트래픽 밀도가 증가할수록 성능이 향상 됨을 알 수 있다.

• 대한기계학회논문집B
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• 제27권3호
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• pp.326-333
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• 2003

In the measurement using DMA and CPC in series, there is some time delay for particles classified in DMA to detect in CPC. During this time, the DMA time-response changes due to the velocity profile of sampling tube and the diffusion of particles in the volume that exists between the DMA exit and the detector of ultra-fine CPC. This is called mixing effect. In the accelerated measurement methods like the TSI -SMPS, the size distribution is obtained from the correlation between the time-varying electrical potential of the DMA and the corresponding particle concentrations sampled in DMA. If the DMA time -response changes during this delay time, this can cause the error of a size distribution measured by this accelerated technique. The kernel function considering this mixing effect using the residence time distribution is proposed by Russell et al. In this study, we obtained a size distribution using this kernel to compare to the result obtained by the commercial accelerated measurement system, TSI -SMPS for verification and considered the errors that result from the mixing effect with the geometric mean diameters of originally sampled particles, using virtually calculated responses obtained with this kernel as input data.

• 한국추진공학회지
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• 제17권2호
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• pp.1-8
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• 2013

모형 연소실에서 충돌형 분사기의 연소 안정성 평가를 위해 시간지연(time lag)과 간섭인자(interaction index)의 관계를 연구하였다. 산화제 분사 속도의 5%에 해당하는 섭동을 공진주파수로 인위적으로 가진하여 이에 대한 화염의 응답특성을 분석하였다. 연료와 산화제의 혼합지점인 충돌점들, 즉, 특성길이 위치에서 속도섭동과 열방출율 섭동간의 관계를 시간지연 모델을 이용하여 나타내었다. 시간지연을 정량화하는 개선된 방법으로서, 수치해석을 통해 얻은 결과로부터 분사기 출구면으로부터 충돌점까지 평균속도를 이용하는 방법을 제안하였다. 축방향의 평균속도가 증가할수록 시간지연이 짧아지는 경향성을 확인할 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.740-743
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• 1997

Reference models are used in many control algorithms for improvement of transient response characteristics. They provide desired trajectories that the plant should follow. Most control systems have bounded control inputs to avoid saturation of the plant. If we design reference models that do not account for limits of control inputs, control performance of the system may be deteriorated. In this paper, therefore, the way of determining variable reference models for TDC(time delay control) technique is proposed. The variable reference model is determined based on the information of bounded control inputs and reference inputs. This proposed method is also verified by application to the position control experiment using the BLDC motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.981-983
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• 1998

In this paper, we present theoretical designs for a beam steering phased array antenna that uses a true time delay optical feeder. A variable true time delay is achieved by employing one tunable laser source and high dispersion fibers with different length. The wavelength tunable optical carrier propagation in a high-dipersion fiber realizes a true time delay, with the steering direction set by a single voltage controlling the wavelength. Beamsteering of a phased array antenna is obtained by controlling the tunable laser source. An employment of a high dispersion fiber response shows wide-band operation of beem steering antenna system.