• 대한기계학회논문집
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• 제17권10호
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• pp.2457-2466
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• 1993

A simple method is presented for determining transient responses of locally nonlinear structures using substructure eigenproperties and Lagrange multiplier technique. Although the method is based upon the mode synthesis formulation procedure, the equations of the combined whole structure are not constructed compared with the conventional methods. Lagrange multi-pliers are used to enforce the conditions of geometric compatibility between the substructure interfaces and they are treated as external forces on each substructure itself. Substructure eigenvalue problem is defined with the substructure interface free of fixed. The transient analysis is based upon the recurrence discrete-time state equations and offers the simplicity of the Euler integration method without requiring small time increment and iterative solution procedure. Numerical examples reveal that the method is very accurated and efficient in calculating transient responses compared with the direct numerical integration method.

• 한국광학회지
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• 제2권4호
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• pp.209-213
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• 1991

최근들어 극초단 광학펄스를 생성하고 증폭하는 기술의 발달로 인하여 시분해 레이저 분광학에 많은 영향을 끼치게 되었다. 그 중에서도 응용성이 넓은 순간흡수분광학장치를 본 연구실에서 개발하였다. 이 기술은 고출력 레이저 펄스를 이용하여 white light continuum pulse를 생성시켜 이를 조사빔으로 이용하고, pump pulse는 원래 상태의 레이저를 이용하는 것이다. 순간흡수율 변화를 여러 파장에서 측정가능하도록 photodiode array를 이용하였으며, pump와 probe pulse의 시간차이에 의한 순간흡수율 변화를 색소의 일종인 DDI를 이용하여 측정하였다.

• 한국공작기계학회논문집
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• 제14권3호
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• pp.96-102
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• 2005

Acoustic Emission(AE) technique has been applied to not only material characterization evaluation but also on-line monitoring of the structural integrity. The AE source location technique is very important to identify the source, such as crack, leak detection. Since the AE waveforms obtained from sensors are very difficult to distinguish the defect signals, therefore, it is necessary to consider the signal analysis of the transient wave-form. In this study, we have divided the region of interest into a set finite elements, and calculated the arrival time differences between sensors by using the velocities at every degree from 0 to 90. A new technique for the source location of acoustic emission in fiberboard plates has been studied by introducing Wavelet Transform(WT) do-noising technique. WT is a powerful tool for processing transient signals with temporally varying spectra. If the WT de-noising was employed, we could successfully filter out the errors of source location in fiberboard plates by arrival time difference method. The accuracy of source location appeared to be significantly improved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.306-309
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• 1993

Digital redesign techniques are to derive a digital controller fred the existing continuous controller and its plant so that the performance of the digitally controlled system is matched as closely as possible to that of the original continuous system at the sampling instants. Recently a new digital redesign technique, was developed to use the generalized sampled-data hold function(GSHF) based on the the grammian matrix. With this new technique the digitally redesigned system showed several good features compared with any existing technique in terms of the state match at the sampling instants, the large sampling period, and the transient reponses. This paper concerns a further improvement of the new digital redesign technique by employing the discrete grammian matrix instead of the continuous grammian matrix in defining GSHF. With this modification, it was observed by simulation that the transient response of the modified digital system shows far better performance than the digital system based on the continuous grammian matrix.

• 전력전자학회논문지
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• 제4권6호
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• pp.491-499
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• 1999

본 논문은 새로운 제어기법의 고성능 전동차 추진용 IGBT VVVF 인버터에 관한 것이다. 현차 적용 전에 견인력 제어성의 우수함과 안정성을 검증하기 위해, 현차 조건에서 발생될 수 있는 경우에 대한 모의 주행시험을 실시하고 그 결과를 보인다. 모의 주행시험은 160톤의 차량을 등가화한 관성부하장치를 이용하여 정상상태는 물론 전압변동 등 각종 과도상태에 대해서도 실시하였다. 본 논문에서는 4병렬 접속된 견인전동기의 토오크 제어성 향상을 위한 벡터제어기법 적용과 공간벡터 변조기법에 동기방식을 적용하여 500Hz이하의 저주파 스위칭으로써 6스텝까지 연속 과변조 제어가 가능한 최적의 PWM방법을 제시한다.

• 전기학회논문지
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• 제62권5호
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• pp.723-729
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• 2013

This paper presents an parallel type Linear Induction Motor with ununiform airgap for a shallow-depth underground train with 100‰ grade and 15 m curvature. This parallel type LIM has enough gradability but has inherently ununiform airgap between center and end parts. Consequently, performance when the train passes curved section should be considered with transient analysis. Moreover, general parallel operation, 1C2M which is usually used for train operation, deteriorates LIM performance because of different line velocity between inner and outer LIMs. Transient analysis has many problems such as huge model, lots of meshes, very long calculation time, truncation error and so on. This paper has presented a novel technique using equivalent linear rotating model in order to solve these problems and has analyzed parallel type LIM by using the proposed technique. Finally, LIM performance according to independent operating control has been investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.530-532
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• 2005

Actually, it's very difficult to discriminate the transient on underground power cable system because of the reflected signal including many noises. Therefore, in this paper, a solution based on multiple scales correlation of the transient using SWT(Stationary Wavelet Transform) is presented. It's quick and straightforward. For applying all algorithms, we just use the signal captured in single end.

• 전산구조공학
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• 제8권2호
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• pp.141-145
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• 1995

이 논문은, 선형점탄성체가 과도온도상태에 있을때의 거동을 시간영역 경계요소법에 의해 해석하고 있다. 점탄성체에 대해서 '열유동단순'거동을 가정하였다. 경계요소 공식화과정을 설명한 후, 예제문제에 대한 수치해석 결과를 보여주었다.

• 천문학회보
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• 제42권2호
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• pp.64.3-64.3
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• 2017

For the detection of transient sources in optical wide field surveys like KMTNet Supernova Project, difference imaging technique is commonly used. As this method produces a fair amount of false positives, it is also common to utilize machine learning algorithms to screen likely true positives. While deep learning methods such as a convolutional neural network has been successfully applied recently, its application can be limited if the size of the training sample is small. I will discuss a variation of more conventional method that adopts the wavelet transform for feature engineering and its performance.

• 대한전기학회논문지
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• 제37권6호
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• pp.368-375
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• 1988

This paper is concerned with the design of the optimal gains of the controller in the speed control system for the induction motor controlled by the microprocessor. The system is modelled with the discrete-time state equation, considering the time delay, for the facility of the optimization techniques. Introducing the conjugate gradient descent method, as the optimization technique, are derived the optimal gains, the gains which give the best transient characteristics. At the optimal gains obtained, the theoretcal transient responses are verified by experimental ones on a 5HP induction motor drive system.