• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.379-384
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• 2007

In this paper, a new method for detecting rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occurs. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element (FE) software packages, and treasuring the flux are made using search coils. In the FE analysis and experiment, the three-phase squirrel-gage induction motor with 380 [V], 7.5 [kW], 4 Poles, 1,768 [rpm] ratings is used. The simulation and experiment results can be useful for detecting rotor vibration of the induction motors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.502-508
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• 2000

In order to detect the partial discharge with the metallic particle in GIS the AE(Acoustic Emission) sensor was designed and simulated by ANSYS 5.5 and manufactured as the coupled vibration mode. The measured resonant frequency and the maximum sensitivity frequency of three coupled AE sensors were as follows ; 147.88 kHz in 8.1mm $\Phi$$\times$8.1mm 128.82 kHz and 58.8 kHz in 9.5 mm$\Phi$$\times$9.5mm, 85.22 kHz and 32.6 kHz in 14.3 mm$\Phi$$\times$14.3 mm, resonant frequency of the AE sensor. The AE sensor of 9.5 mm$\Phi$$\times$9.5mm responded higher than the other coupled vibration mode AE sensor at the partial discharge detection in GIS.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.243-245
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• 2005

Condition monitoring is desirable for increasing machinery availability, reducing consequential damage, and improving operational efficiency. In this paper, a model-based method using neural network modeling of induction noter in vibration spectra is proposed for machine fault detection and diagnosis. The short-time Fourier transform (STFT) is used to process the quasi-steady vibration signals to continuous spectra so that the neural network model can be trained with vibration spectra. And the faults are detected from changes in the expectation of vibration spectra modeling error. The effectiveness of the proposed method is demonstrated through experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.53-60
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• 1998

In this study, it is experimented to find factors effecting surface roughness using the system of experiments. in the mirror surface finishing system. (1) The film feed and oscillation frequency in $40{\mu}m$ abrasive film, grinding speed in $30{\mu}m$, and machining time in $15{\mu}m$15 are the main factors effecting the surface roughness. (2) Applying the optimal finishing condition to $40{\mu}m$, $30{\mu}m$, $15{\mu}m$ abrasive finishing film in sequence, it is possible to obtian about Ra 10 nm surface roughness on SM45C workpiece. (3) Application of the system of experments to the micro abrasive grain film finishing was very effective method in the extraction of main factor and optimal condition.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.701-702
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• 2000

The thiolated anti-Escherichia coli antibody prepared by thiolation with a thiolcleavable heterobifunctional cross-linker, sulfosuccinimidyl 6[3- (2-pyridyldithio) propionamido]hexanoate (sulfo-LC-SPDP) was chemisorped onto one gold electrode of the piezoelectric quartz crystal surface. In the QCM system employing a batch-type well holder, a steady-state frequency decrease was attained within 20 min when $100{\sim}200\;{\mu}L$ suspensions of Escherichia coli having viable cell counts of $10^5{\sim}10^6\;CFU/mL$ were added. The stability of sensor response was improved compared to the system with a batch-type dip holder.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.653-655
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• 1999

카메라 영상을 통하여 무인 헬리콥터 동작을 추정하기 위해 적응형 가중치를 사용한 새로운 Ego-Motion을 검출 기법을 제안하였다. 무인 헬리콥터 동적 특성은 비선형이며, 심한 진동 발생으로 영상 번짐(blur) 현상이 나타나기 때문에 상관 값만을 고려한 정합 방법으로는 빈번히 오차가 발생한다. 본 논문에서는 가속도, 각 가속도 및 제어입력 값에 의한 위치 추정 값과 상관 값 및 에지 강도를 가중치에 의해 융합하여 정확한 Ego-Motion을 계산할 수 있는 기법을 제안하였다. 또한 무인 헬리콥터의 가속도, 각 가속도, 상하 속도에 따라서 영상의 번짐 정도가 달라 이들 같이 크면 위치오차에 가중을 크게 주고, 작으면 상관 값에 가중치를 적게 주는 적응형 가중치 결정 알고리즘을 적용하였다. 제안한 적응형 가중치 기법을 무인 헬리콥터에 실험한 결과 카메라에 포착된 영상에 의해 무인헬기의 동작을 정확히 추정 할 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.1
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• pp.1-6
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• 1972

The ftatistica1 correlation method for estimating impulse response using maximum period null sequence as test signal was studied and in describing some preliminary experimental work, the author discussed the problms of mechanization supported by analytical considerations. Experiments were performed on the 2nd order oscillatory system and the results were in good coincidence with the theoretical values.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.179-184
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• 2013

In this article, we introduce the study case of technology that can automatically compensate the errors of these factors of a machine during processing on the machine tool's CNC(Computerized Numerical Controller) in real time. The biggest factors that lower the machining accuracy are thermal deformation and chatter vibration. This study is related to the detection and compensation of thermal deformation and chatter vibration that can compensate for faster and produce processed goods with more precision by autonomous compensation. In addition, this study is related to the active control of vibration during machining, monitoring of cutting force and auto recognition of machining axes origin. Thus, we attempt to introduce the related contents of the development we have made in this article.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.117-121
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• 1992

There have been many studies on chatter vibration in machining but there seems to be no regulations to decide the commencing point of chatter objectively. The development of an objective method which can estimate and detect chatter commencement is very much in need for automatic manufacturing systems, dynamic performance tests for machine tools, and so on. In this study, an approach for in-process monitoring and for deciding commencing point of the chatter vibration using the frequency band-energy method was proposed. From this method, in-process monitoring system for detection the chatter vibration was developed, and investigated its practical possibility. As a result, it is shown by experiments that the chatter vibtation can be detected accurately. Since the changing pattern of the signal energy in certain frequency band during chattering is seldom affected by the variation of cutting conditions, if adequate pre-measures are taken, this method can be widely used in most machining processes.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.47-54
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• 2009

Spin coaters are the essential instruments in micro-fabrication processes, which apply uniform thin films to flat substrates. In this research, a spin coater diagnosis system is developed to detect the abnormal operation of TFT-LCD process in real time. To facilitate the real-time data acquisition and analysis, the circular-buffered continuous data transfer and the short-time Fourier transform are applied to the fault diagnosis system. To determine whether the system condition is normal or not, a steady-state detection algorithm and a frequency spectrum comparison algorithm using confidence interval are newly devised. Since abnormal condition of a spin coater is rarely encountered, algorithm is tested on a CD-ROM drive and the developed program is verified by a function generator. Actual threshold values for the fault detection are tuned in a spin coater in process.