• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.124-132
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• 2003

The goal of this paper is to propose a virtual instrumentation system based on three dimensional current coordinates for monitoring power quality A developed system with various experimental graphic screens and numerical results is made up 586-PC and DSP(digital signal processor) board, power quality analyzing and evaluating software for windows. Power parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis. results are visualized by 3-D current coordinates, and it Is compared and evaluated with conventional time / frequency domain. To verify the validity of the proposed system, power and harmonic parameters of single phase induction motor drives is analyzed and verified.

• The Journal of the Acoustical Society of Korea
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• 제27권3E호
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• pp.84-94
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• 2008

Displacement estimation is a crucial step in ultrasonic strain imaging. The displacement between a pre- and postcompression signal in the current data window is estimated by first shifting the postcompression signal by the displacement obtained in the previous data window to reduce their decorrelation and then determining the remaining part of the displacement through autocorrelation and conversion of phase difference into time delay. However, since strain image quality tends to vary with the amount of compression applied, we propose two new methods for enhancing strain image quality, i.e., displacement normalization and adaptive persistence. Both in vitro and in vivo experiments are carried out to acquire ultrasound data and produce strain images in real time under the application of quasi static compression. The experimental results demonstrate that the methods are quite effective in improving strain image quality and thus can be applied to implementing an ultrasound elasticity imaging system that operates in real time.

• International Journal of Korean Welding Society
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• 제1권1호
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• pp.7-12
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• 2001

Real time monitoring has become critical as the use of laser welding increases. Plasma and spatter are measured and used as the signal for estimating weld quality. The estimating algorithm was made using the fuzzy pattern recognition with the area of data that is beyond the tolerance boundary. Also, an algorithm that detects the spatter and the localized defect was created in order to kd the partially produced pit and the sudden loss of weld penetration. These algorithms were used in quality monitoring of the $CO_2$ laser tailored blank weld. Statistical program that can display the laser weld quality result and the signal transition was made for the first stage of the remote control system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.603-612
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• 2009

The bogie hunting sensor detects accelerations of a bogie. It transmits those accelerations using frequency modulated signal to the TCMS(Train Control and Management System) electronics for functional processing. TCMS decide undesirable bogie hunting and high speed instability with frequency modulated signal. The bogie hunting sensor is essential component for safety driving of high speed train. The bogie hunting sensor's quality inspection before sensor is installed on bogie is very important. Therefore it is required equipment for exact inspection of train bogie hunting sensor. This study is about development of Bogie Hunting sensor's inspection equipment that we can improve Bogie Hunting sensor's quality. Accordingly, I suppose that this thesis will be utilized to improve the bogie hunting sensor's quality thru exact inspection.

• 전자공학회논문지
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• 제50권4호
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• pp.155-162
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• 2013

기존의 블록 기반 압축 센싱은 고정 블록 크기를 사용하여 신호를 복원하며, 영역별 신호의 특성에 적합한 블록 크기를 사용하지 못하여 복원 성능이 저하된다. 본 논문에서는 이 문제를 해결하기 위하여 블록 기반 압축 센싱에서 신호의 특성에 따라 블록 크기를 가변적으로 결정하여 복원 신호의 품질을 향상시키는 가변 블록 크기 기술을 제안한다. 제안한 방법은 여러 블록 크기로 신호를 복원하고, 프레임별로 각 복원한 신호의 자기 상관도를 측정하여 신호의 특성을 확인하고, 프레임의 블록 크기를 결정한다. 동일한 측정 데이터에 대하여 제안한 가변 블록 크기 방법이 기존의 고정 블록 크기 방법에 비하여 향상된 품질의 신호를 복원하는 것을 확인하였다.

• 전자공학회논문지B
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• 제33B권11호
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• pp.72-82
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• 1996

In this paper, newly developed algorithm for enhancing images corrupted by white gaussian noise is proposed. In the method proposed here, image is subdivided into a number of subblocks, and each block is separated into cimponents corresponding to signal and noise subspaces, respectively through the signal subspace method. A clean signal is then estimated form the signal subspace by the adaptive wiener filtering. The decomposition of noisy signal into noise and signal subspaces in is implemented by eigendecomposition of covariance matrix for noisy image, and by performing blockwise KLT (karhunen loeve transformation) using eigenvector. To reduce the perceptual noise level and distortion, wiener filtering is implementd by adaptively adjusting noise level according to activity characteristics of given block. Simulation results show the effectiveness of proposed method. In particular, edge bluring effects are reduced compared to the previous methods.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.872-875
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• 2002

A digital watermarking technique applying psychoacoustic model for audio signal is proposed in this paper. In the watermarking scheme, the pseudo-random bit stream used as a watermark signal is embedded into the audio signal in both speech and music. The strength of the embedded signal is subject to the human auditory system in such a way that the disturbances on host audio signal are beyond the sensing of human ears. The experimental results show that the quality of the watermarked audio signal, in term of signal to noise ratio, can be improved up to 3.2 dB.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.919-924
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• 1994

The use of adaptive feedback cancellation to prevent howling requires a reference signal that is correlated with the feedback signal by is not correlated with the input signal. Such a signal is hard to obtain in hearing aids. In this paper, the use fo frequency compression to decorrelate the output signal with input signal for use as reference is presented. Performance evaluation results indicate that with the proper choice of system parameters, the use of this system can provide a significant increase in howling margin with minimal deterioration in output signal quality.

• The Journal of the Acoustical Society of Korea
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• 제14권1E호
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• pp.30-38
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• 1995

본 논문에서는 이동통신망에서 신호 가산방식을 이용한 삼자회의에서의 음성 부호화기 성능을 평가하였다. 두 사람의 섞인 목소리가 다른 회의 참가자에게 전달되는 신호 가산방식은 가장 자연스러운 삼자회의 방식이지만, 아직까지 두 사람의 섞인 목소리를 부호화할 수 있는 유용한 방법은 없다. 본 논문에서는 삼자회의에 신호 가산방식을 적용하기 위해 QCELP, VSELP, RPE-LTP 보코도를 구현하여 평가를 수행하였다. 또한 두 화자의 목소리가 섞인 음성신호에 대한 부호화기의 성능평가를 위해 기존의 음질 평가법을 그대로 사용할 수 없으므로, 본 논문에서는 두 가지 주관적 평가법을 제안하였다. 제안된 방법은 문장 식별법(SD)과 수정된 DMOS(MDOMS) 방법이다. 실험결과에 의하면 VSELP 보코더의 출력음질이 다른 두 보코더에 비해 좋게 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제39권2호
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• pp.179-186
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• 2015

In the indoor location estimation system, which has recently been actively studied, the received signal strength indicator contains a high level of noise when measuring the signal strength in the range between two nodes consisting of a receiver and a transceiver. To minimize the noise level, this paper proposes an improved adaptive smoothing filter that provides different exponential weights to the current value and previous averaged one of the data that were obtained from the nodes, because the characteristic signal attenuation of the received signal strength indicator generally has a log distribution. The proposed method can effectively decrease the noise level by using a feedback filter that can provide different weights according to the noise level of the obtained data and thus increase the accuracy in the distance and location without an additional filter such as the link quality indicator, which can verify the communication quality state to decrease the range errors in the indoor location recognition using ZigBee based on IEEE 802.15.4. For verifying the performance of the proposed improved adaptive smoothing filter, actual experiments are conducted in three indoor locations of different spatial sections. From the experimental results, it is verified that the proposed technique is superior to other techniques in range measurement.