• Journal of applied mathematics & informatics
• /
• 제13권1_2호
• /
• pp.165-182
• /
• 2003

Sufficient conditions for oscillation of all solutions of a class of second-order quasilinear delay differential equations with fixed moments of impulse effect are found.

• 한국농공학회논문집
• /
• 제61권4호
• /
• pp.87-96
• /
• 2019

The objective of this study was to develop a general inundation modeling technique considering the effect of drainage delay in the paddy field districts. In most studies, farmland inundation simulations have been conducted using previously developed watershed models. However, the water cycle in the paddy fields has a different structure from that of the general watershed, and the effect of the drainage delay should be considered. In this study, the drainage delay algorithm was developed using water balance equation, and the inundation modeling was performed for inundation-prone paddy fields located near Doowol stream. As a result, the depth of inundation was 43.1 cm and 45.2 cm, respectively, due to the 100-year and 200-year frequency rainfall. With the operation of drainage pump ($0.1m^3/s$), inundation depths decreased by 5.8 cm and 6.0 cm, respectively, and inundation time reduced by 20 hours and 21 hours, respectively for the 100-year and 200-year frequency rainfall. The result showed that the general inundation modeling technique developed in this study could reflect the effect of drainage delay due to the rise of external water level and the flooding reduction effect by operation of drainage pump. The results of this study are expected to be useful to establish measures for damage caused by farmland inundation.

• Structural Engineering and Mechanics
• /
• 제58권6호
• /
• pp.1127-1143
• /
• 2016

The pounding phenomenon in adjacent structures happens in severing earthquakes that can cause great damages. Connecting neighboring structures with active and semi-active control devices is an effective method to avoid mutual colliding between neighboring buildings. One of the most important issues in control systems is applying online control force. There will be a time delay if the prose of producing control force does not perform on time. This paper proposed a time-delay compensation method in coupled structures control, with semi-active Magnetorheological (MR) damper. This method based on Newmark's integration is adopted to mitigate the time-delay effect. In this study, Lyapunov's direct approach is employed to compute demanded voltage for MR dampers. Using Lyapunov's direct algorithm guarantees the system stability to design a controller based on feedback. Because of the strong nonlinearity of MR dampers, the equation of motion of coupled structures becomes an involved equation, and it is impossible to solve it with the common time step methods. In present paper modified Newmark-Beta integration based on the instantaneous optimal control algorithm, used to solve the involved equation. In this method, the response of a coupled system estimated base on optimal control force. Two MDOF structures with different degrees of freedom are finally considered as a numeric example. The numerical results show, the Newmark compensation is an efficient method to decrease the negative effect of time delay in coupled systems; furthermore, instantaneous optimal control algorithm can estimate the response of structures suitable.

• Transactions on Control, Automation and Systems Engineering
• /
• 제2권4호
• /
• pp.274-284
• /
• 2000

In this paper, the design methodology of digital fuzzy controller(DFC) for the systems with time-delay is presented and the qualitative effects of the quantizers in digital implementation of a fuzzy controllers are investigated. We propose the fuzzy feed-back controller whose output is delayed with unit sampling period and period and predicted. the analysis and the design problem considering time-delay become very easy because the proposed controller is syncronized with the sampling time. The stabilization problem of the digital fuzzy system with time-delay is solved by linear matrix inequality(LMI) theory. Furthermore, we analyze the stability of the quantized fuzzy system. Our results prove that when quantization os taken into account, one only has convergence to some small neighborhood about origin. We develop a fuzzy control system for backing up a computer-simulated truck-trailer with the consideration of time-delay and quantization effect. By using the proposed method, we analyze the quantization effect to the system and design a DFC which guarantees the stability of the control system in the presence of time-delay.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2001년도 춘계종합학술대회
• /
• pp.236-239
• /
• 2001

본 논문은 적응 전송시스템의 시간지연에 대한 영향을 고려한다. 적응 시스템은 채널의 조건들에 의해 데이터 전송을 적응적으로 수행하는 시스템을 말한다. 다시말해 심볼당 전송한 비트 수를 순간 채널특성을 조사하여 대역폭 효율을 증대시킬 수 있도록 제어한다. 개발된 시뮬레이터를 이용하여 3GPP에서 제안된 채널모델을 포함한 많은 채널 전파환경을 시뮬레이터에 적용하여 SNR 및 시간지연 요소에 대해 성능을 평가하였다. 성능 평가결과는 채널의 시간 지연성분에 대해 성능은 아주 민감하며 어떤 경우는 SNR 값과 상관없이 성능이 더 이상 줄어들지 않는 현상도 나타났다. 따라서 페이딩율과 시간지연의 정도에 따라 적응 시스템의 성능은 크게 영향을 받게 된다.

• 한국정보통신학회논문지
• /
• 제5권2호
• /
• pp.337-342
• /
• 2001

본 논문은 적응 전송시스템의 시간지연에 대한 영향을 고려한다. 적응 시스템은 채널의 조건들에 의해 데이터 전송을 적응적으로 수행하는 시스템을 말한다. 다시 말해 심볼당 전송한 비트 수를 순간 채널 특성을 조사하여 대역폭 효율을 증대시킬 수 있도록 제어한다. 개발된 시뮬레이터를 이용하여 3GPP에서 제안된 채널모델을 포함한 많은 채널 전파환경을 시뮬레이터에 적용하여 SNR 및 시간지연 요소에 대해 성능을 평가하였다. 성능 평가결과는 채널의 시간 지연성분에 대해 성능은 아주 민감하며 어떤 경우는 SNR 값과 상관없이 성능이 더 이상 줄어들지 않는 현상도 나타났다. 따라서 페이딩율과 시간지연의 정도에 따라 적응 시스템의 성능은 크게 영향을 받게 된다.

• 한국전자파학회논문지
• /
• 제15권3호
• /
• pp.265-270
• /
• 2004

본 논문에서는 group delay가 위성 통신 시스템에 미치는 영향을 분석한다. 일정한 상수가 아닌 group delay에서는 신호의 위상 왜곡이 발생한다. Group delay는 특성에 따라 linear, parabolic, cubic으로 모델링할 수 있다. 각각의 group delay 특성을 위성통신 시스템에 적용하여 BER(bit error rate)을 분석한다. Group delay는 신호의 대역폭이 커질수록 신호에 미치는 영향이 커지는 특성을 갖고 있으며, 위성 통신 시스템의 정보 전송속도가 1Mbps, 4Mbps, 8Mbps 의 세 가지인 경우에 대하여 BER을 분석한다. 이때 channel coding으로는 구속장이 7이고, code rate 1/2인 convolution coding과 7/8 punctured convolution coding 를 이용한다. BER = $10^{-5}$을 만족하는 요구 SNR을 관찰하였을 때, group delay의 영향을 받는 데이터는 group delay의 영향을 받지 않은 데이터에 비해 요구 SNR은 최소 0.3㏈에서 최대 4.4㏈으로 증가한다. 이들 중 group delay에 의한 영향이 가장 큰 경우는 group delay의 특성이 linear 특성이고 channel coding이 7/8 puncture convolution coding, 전송속도가 8 Mbps인 경우로서 이때 요구 SNR은 4.4㏈증가한다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
• /
• pp.113-116
• /
• 2000

The effect due to group delay and non linear characteristics in high speed data satellite channel was represented in this paper. Based on the modeling of group delay and non linear characteristics the performance was analyzed in ka band satellite channel. The group delay and non-linear characteristics in high speed data transmission severely affect the system performance. The more Eb/No is required to satisfy the required system performance. The optimum operating points of HDR satellite transmission system are implemented by considering analyzed results for channel characteristics

• 천문학회보
• /
• 제40권1호
• /
• pp.82.1-82.1
• /
• 2015

We investigate the long-term spatial drift of the center and the temporal variation of the shutter delay time map of Y4KCam mounted on the CTIO 1.0m telescope. We have collected shutter delay time maps for over 7 years as a part of long-term survey program. We find that the center of the shutter delay time map can drift up to $450{\mu}m$ on the CCD. This effect can result in a small amount of error unless the proper shutter delay time correction, but it does not appear to cause any significant problems in photometric measurements. We obtain the mean value of the shutter delay time of $69.1{\pm}0.9$ msec and find no temporal variation of the shutter delay time of Y4KCam for over 7 years, indicative of the mechanical stability of the shutter. We suggest that using a master shutter delay time correction frame would be sufficient to achieve high precision photometry and this does not add up errors more than ~ 2.5 mmag across the CCD frame with exposure times longer than 1 sec.

• Transactions on Control, Automation and Systems Engineering
• /
• 제2권2호
• /
• pp.98-103
• /
• 2000

This paper is concerned with a delay-dependent sliding mode scheme for the robust stabilization of input-delay systems with bounded unknown uncertainties. A sliding surface based ona predictor is proposed to minimize the effect of the input delay. Then, a robust control law is derived to ensure the existence of a sliding mode on the surface. In input-delay systems, uncertainties given during te delayed time are not directly controlled by the switching control because of causality prolem of them. They can influence the stability of the system in the sliding mode. Hence, a delay-dependent stability analysis for reduced order dynamics is employed to estimate maximum delay bound such that the system is globally asymptotically stable in the sliding mode. A numerical example is given to illustrate the design procedure.