• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1977-1983
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• 2009

This paper described partial discharge(PD) patterns depending on types of insulation defects in CNCO-W cable(Concentric Neutral Closs-linked Polyethylene Insulated Polyolefin-Water Proof Sheathed Power Cable). The PD measurement system consists of a coupling network, a detection impedance, and a low noise amplifier. A 16 bit, 250 MS/s data acquisition system was used to analyze PD patterns. To simulate insulation defects in a power cable, a needle with the curvature radius of $10{\mu}m$ was inserted into the insulation part. We measured phase ($\Phi$), magnitude (q), and counts (n) of PD pulse for the defects, and classified PD patterns using the PRPD (phase Resolved Partial Discharge) method. From the analysis of acquired PD signals, we could find that a unique PD pattern is formed according to the types of defect.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.516-528
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• 2009

Form the application of long rail system the non-ballast steel plate bridges, fatigue strength increase and rail noise reduction can be expected. This is mainly form the reduction of the rail impact at the rail joint locations which already made to behave together from welds. In the high speed rail, application of long rail system is essential because without long rail system, the required serviceability level can not be achieved. But even with this long rail systems, the thermal expansion from the girder can not be absorbed in the normal bearing systems, and these expansion cause between girder and rail. Also unexpected rail buckling and fracture through rail thermal tension may happen. It was found through numerical analysis and field measurement that these problems can be avoided by semi-fixed bearing system. In this study, the benefits of non-ballast plate bridge through long rail system, especially at the point of girder stability, girder stiffness increase and bearing maintenance will be reviewed.

• The Journal of the Acoustical Society of Korea
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• v.2 no.1
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• pp.11-19
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• 1983

An irregulary formed chamber was designed and constructed to recognize the direct sound radiated from the sound source and the reflected sound from the walls of the chamber. The sound signal used was tone burst in the frequency response characteristics with the signal detection after transient effect. The direct wave, transient phenomena and the primary reflected sound could be asiily distinguished each other by measurements of the arrival time of the time difference. And also noise could be easily distinguished by the same method. The result obtained can be used in industries for automatic measurement of the sound pressure reponse characteristics with respect to frequencies.

• Journal of the Optical Society of Korea
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• v.20 no.3
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• pp.435-440
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• 2016

We developed a simple and real-time readout autocorrelator for several tens and sub-10fs pulses, based on the two photon absorption phenomena of a commercial GaP photodetector including a transimpedance amplifier. With a suitable gain adjustment, we demonstrated that the interferometric autocorrelation for sub-nJ pulses delivered as a high output voltage as to resolve all fringes in an autocorrelation trace with features of low noise and a low offset voltage. By fitting the measured quadratic power dependence of output voltages, we obtained the quantum efficiency of TPA for the GaP detector comparable with those of a GaAsP diode and an SHG with a thin BBO crystal. The autocorrelator of a TPA based GaP photodetector is highly suitable for sensitively measuring a few cycle pulses with a broad spectral distribution from 600 nm to 1100 nm.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.186-191
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• 2008

A phase retrieval method using an error reduction algorithm is developed for reconstructing a wavefront aberration of an 100-TW Ti:sapphire laser pulse from the measurement of a focal spot. The phase retrieval method can successfully reconstruct a wavefront aberration of a 100-TW Ti:sapphire laser pulse, and the reconstructed wavefront aberration shows a good agreement with the wavefront aberration measured with a wavefront sensor. The effect of the dynamic range and the intensity noise on the reconstruction is also investigated in reconstructing a wavefront aberration of an 100-TW Ti:sapphire laser pulse.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1611-1620
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• 2005

This paper shows the use of wavelet transformation combined with inverse acoustics to reconstruct the surface velocity of a noise source. This approach uses the boundary element analysis based on the measured sound pressure at a set of field points, the Helmholtz integral equations and wavelet transformation for reconstructing the normal surface velocity field. The reconstructed field can be diverged due to the small measurement errors in the case of nearfield acoustic holography (NAH) using an inverse boundary element method. In order to avoid this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the order of an optimal truncation is difficult to determine. In this paper, a wavelet transformation is applied to reduce the computation time for inverse acoustics and to enhance the reconstructed vibration field. The computational speed-up is achieved, with solution time being reduced to $14.5\%$.

• Annual Conference of KIPS
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• 2017.11a
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• pp.602-605
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• 2017

본 논문에서 우리는 최근 심각한 사회문제로 떠오르고 있는 '층간소음'을 공학기술과 접목하여 이를 저감 시킬 수 있는 방안을 제시한다. 현재 4차산업혁명시대를 맞이하여 인공지능, AR(Augmented Reality), VR(Virtual Reality), IOT(Internet Of Things), 빅 데이터(Big Data) 등이 등장하고 있다. 우리는 '층간소음' 저감효과를 이끌어 낼 수 있는 방안으로 아두이노를 활용해 홈 IOT와 결합한 형태를 제안한다. 우리는 먼저 기존의 '층간소음' 해결절차를 설명하고 이를 보완한 시스템을 설계하고 이를 구현한다. 우리는 본 논문에서 제시된 방안인 '아두이노를 이용한 홈 IOT 층간소음 측정 어플리케이션'을 통해 더 나은 주거 환경을 조성할 수 있을 것이라 기대한다.

• ETRI Journal
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• v.33 no.3
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• pp.393-400
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• 2011

A systematic approach for the design of two-stage class AB CMOS unity-gain buffers is proposed. It is based on the inclusion of a class AB operation to class A Miller amplifier topologies in unity-gain negative feedback by a simple technique that does not modify quiescent currents, supply requirements, noise performance, or static power. Three design examples are fabricated in a 0.5 ${\mu}m$ CMOS process. Measurement results show slew rate improvement factors of approximately 100 for the class AB buffers versus their class A counterparts for the same quiescent power consumption (< 200 ${\mu}W$).

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.1
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• pp.18-24
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• 2010

In this paper, we address an active ranging system based on laser structured light image for mobile robot application. Since the burdensome correspondence problem is avoidable, the structured light image processing has efficient computation in comparison with the conventional stereo image processing. By using a cylindrical lens in the laser generation, it is possible to convert a point laser into a stripe laser without motorized scan in the proposed system. In order to achieve robustness against environmental illumination noise, we propose an efficient integro-differential image processing algorithm. The proposed system has embedded image processing module and transmits distance data to reduce the computational burden in main control system.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.4
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• pp.37-43
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• 1997

Damages and public complaints are increased due to construction noise and vibration from several sources. It is urgently needed to develop the easy and practical method to estimate the vibration effect. In this study, to predict the vibration effect, the method using the response spectrum with amplification factor concepts prroposed by Newmark and Hall is used. Also the applicability of the method is examined. Vibration measurement on subway structure, foundation and building structures are performed and the results show that the provided method is practical and can be used to predict the vibration effect.