• 한국전자파학회논문지
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• 제13권9호
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• pp.937-946
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• 2002

본 논문에서는 도체로부터의 안정된 전자기 산란 응답을 계산하는 새로운 해법을 제안한다. 이 방법은 기존의 MOT (marching-on in time) 기법을 이용하지 않고, 가중 라게르 (Laguerre) 다항식으로 유기전류의 과도 응답을 표현하여 시간 영역의 적분방정식을 푼다. 이 시간 영역의 기저함수를 사용함으로써 적분식의 미분항을 해석적으로 처리하여 과도 응답을 구할 수 있다. 또한 적용되는 이 기저함수는 시간이 진행함에 따라 영으로 수렴하는 특성 때문에, 유기전류의 과도응답도 후기 진동을 가지지 않고 영으로 수렴한다. 제안되는 방법의 타당성을 보이기 위하여 시간 영역 전장 적분방정식의 해를 MOT 및 해석해와 주파수 영역으로부터 구한 해의 이산 푸리에 역변환 (inverse discrete Fourier transform, IDFT)과도 비교한다.

• 자원환경지질
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• 제34권5호
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• pp.499-506
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• 2001

연안지역에서 해수의 지하 유동현상을 효과적이고 경제적으로 파악하기 위하여 등위치 송수신루프배열의 시간영역 전자탐사법(Time-domain Electromagnetic :TEM)을 이용한 지구물리모니터링을 적용하였다. TEM 모니터링은 전기 비저항 모니터링과 비교하여 해수유동에 대한 TEM반응의 민감도는 떨어진다. 그러나, 광범위한 조사지역에 대한 담수-해수 전이대의 공간적인 분포를 파악하는데 있어서는 측정시간을 포함한 탐사경비 그리고 현장에서 자료처리 측면에서 볼 때 매우 효율적이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.720-725
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• 1991

In this thesis, the lead-lag compensator is designed to improve output characteristics of flyback zero voltage switching quasi-resonant converters. The switch and the diode are assumed ideally. And the SMPS is modelled by state equations with four operation modes. And the model for controller design is also achived by using a state space averaging method, which is continuous time average of state variables every period. The lag, the lead and the lead-lag compensator is designed the SMPS respectively. The time domain analysis and the frequency domain analysis are done for each compensated circuit. It is possible increasing the phase margin and improving the transient response by the compensators. The phase lag compensator has small overshoot comparatively. But the bandwidth is narrower than the others, so it has longest settling time. For the phase lead compensator, the response come to steady-state within short period. But the overshoot is the largest due to its large peak gain. Finally, the phase lead-lag compensator has medium characteristics in the overshoot and the settling time.

• 한국정밀공학회지
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• 제21권5호
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• pp.73-82
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• 2004

This paper presents the study on damage diagnosis of an intelligent cantilevered beams using PZT actuator and PVDF sensor This study provides the theoretical and experimental verification to examine structural damage. Time domain analysis for the non-destructive detection of damage is presented by parameterized partial differential equations and Galerkin approximation techniques. The time histories of the vibration response of structure were used to identify the presence of damage. Furthermore, this systematic approach permits one to use the piezomaterials to both excite and sense the vibration of structures. We also carried out the experimental verification about reliability of theoretical methods fur detecting the damage of a composite beam with PZT actuator and PVDF sensor. Experimental results are presented from tests on cantilevered composite beams which is damaged at different location and different dimensions. The results were compared with the simulation results. Good agreement between the results was found for the time shifts and amplitude difference in transients response of the cantilevered beam.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.23-27
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• 2007

Many trials have been used to model room impulse responses, all attempting to provide efficient representations of room acoustics. The traditional model designs for room impulse response seem to fail in accuracy, controllability, or computational efficiency. In time domain, a room impulse response is generally considered as the combination of three parts having different acoustic characteristics, initial time delay, early reflection, and late reverberation. This paper introduces new learning hybrid model for the room impulse response. In this proposed model, those three parts are modeled using different models with learning algorithms that determine the length or boundary of each model in the hybrid model. By the simulation with measured room impulse responses, it was examined that the performance of proposed model shows the best efficiency in views of both the parameter numbers and modeling error.

• 제어로봇시스템학회논문지
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• 제9권4호
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• pp.259-269
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• 2003

This paper considers the problem of determining a set of PI, PD and PID controller gains, for a given linear time invariant plant, that meets or exceeds the closed loop step response specifications. The proposed method utilizes two recent results: for a given system, (1) finding a set of stabilizing PI, PD and PID gains and (2) the relationship between time response (overshoot and speed) and the coefficients of the characteristic polynomial. The method allows us to extract a subset of PI, PD and PID gains that meets stability as well as time domain performance requirements. The intersections of two dimensional sets described by linear and quadratic inequalities in the controller design space are need to be Identified through numerical computation. The procedure is illustrated by examples.

• 한국전기전자재료학회논문지
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• 제17권5호
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• pp.536-540
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• 2004

A novel nematic liquid crystal (LC) cell with splay structure exhibiting wide viewing angle, fast response time and high transmittance at the same time has been developed. With rubbed homeotropic alignment in parallel directions, the device shows bend alignment in the absence of vertical electric field. However, with applied high voltage in a pulse form, the LC shows a optically compensated splay (OCS) orientation such that the mid-director is parallel to a substrate and at both surfaces the LCs are aligned vertically in parallel direction. In the device, the birefringence of the cell becomes tunable with applying voltage, i.e., the amount of light passed through the cell can be controlled by controlling the orientation of the LC. Since the OCS cell has a self-compensation structure such that the LC has a mirror symmetry along the mid-director, the device shows a wide viewing angle with only a single domain and a fast response time.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권1호
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• pp.1-13
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• 2006

This paper presents the problems of designing low-order controller for a linear time-invariant(LTI) system in parameter space, wherein both transient response requirements and stability shall be considered in the same space. For a LTI system, we, (1) develop a method determining the existence of low-order stabilizers of the first-order and PID structures, (2) develop an algorithm of finding such a stabilizing region. (3) Both procedures are carried out by means of a parametric approach in the same frame work. This leads to easily obtain a subset of controller gains from the stabilizing set, that meet good time response requirements. It is illustrated by examples.

• Wind and Structures
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• 제5권1호
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• pp.49-60
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• 2002

This paper describes a simple method for evaluating the design wind loads for the structural frames of circular flat roofs with long spans. The dynamic response of several roof models were numerically analyzed in the time domain as well as in the frequency domain by using wind pressure data obtained from a wind tunnel experiment. The instantaneous displacement and bending moment of the roof were computed, and the maximum load effects were evaluated. The results indicate that the wind-induced oscillation of the roof is generally dominated by the first mode and the gust effect factor approach can be applied to the evaluation of the maximum load effects. That is, the design wind load can be represented by the time-averaged wind pressure multiplied by the gust effect factor for the first mode. Based on the experimental results for the first modal force, an empirical formula for the gust effect factor is provided as a function of the geometric and structural parameters of the roof and the turbulence intensity of the approach flow. The equivalent design pressure coefficients, which reproduce the maximum load effects, are also discussed. A simplified model of the pressure coefficient distribution is presented.

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.347-362
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• 2005

The input energy to a base-isolated (BI) building during an earthquake is considered and formulated in the frequency domain. The frequency-domain approach for input energy computation has some notable advantages over the conventional time-domain approach. Sensitivities of the input energy to the BI building are derived with respect to uncertain parameters in the base-isolation system. It is demonstrated that the input energy can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum of acceleration) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for deriving the sensitivities of the input energy to the BI building with respect to uncertain parameters. The sensitivity expressions provide us with information on the most unfavorable combination of the uncertain parameters which leads to the maximum energy input.