• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.341-343
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• 2005

This paper introduces a compression algorithm for power quality disturbance signal via the discrete wavelet transform, DWT. Algorithm to estimate a time delay from the power quality disturbance signal is proposed. Pseudo-stationary signal is constructed from the estimated time delay. A difference signal or nonstationary signal is obtained by removing a pseudo-stationary signal from a disturbance signal. DWT is applied to a difference signal. The threshold is applied to reduce a number of coefficients. Simulation results show the resonable compression ratio while keep low signal distortion.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2017년도 추계학술대회
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• pp.51-53
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• 2017

본 논문은 프레임 율 향상을 위한 움직임 추정 알고리듬을 제안한다. 양방향 움직임 추정은 중첩 영역이나 홀 (hole) 영역이 발생하지 않지만 물체의 실제 움직임을 찾는 데에 어려움이 있다. 이중 움직임 추정 방법은 이를 어느정도 해결하였지만 여전히 실제 물체의 이동과는 다른 움직임 벡터들이 남아있다. 움직임 벡터의 정확도를 향상시키기 위해 기존의 이중 움직임 추정 알고리듬을 토대로 SMD (side matching distortion)를 움직임 추정 매칭 식에 결합한 새로운 매칭 기준 식을 제안한다. 결과적으로 제안하는 알고리듬은 기존의 이중움직임 추정 방법에 비해 정량적으로 PSNR (peark signal-to-noise ratio)이 크게 향상되었으며 주관적으로도 뛰어난 결과를 보여주었다.

• 대한음성학회지:말소리
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• 제59호
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• pp.13-25
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• 2006

In previous study, the linlog(linear log) RASTA(J-RASTA) approach based on PLP was proposed to deal with both the channel effect and the additive noise. The extraction of PLP required generally more steps and computation than the extraction of widely used MFCC. Thus, in this paper, we apply the linlog function to the MFCC for investigating the possibility of simple compensation method that removes both distortion. With the experimental results, the proposed method shows the similar tendency to the linlog RASTA-PLP_ When the J value is set to le-6, the best ERR(Error Reduction Rate) of 33% is obtained. For applying the linlog function to the feature extraction process, the J value plays a very important role in compensating the corruption. Thus, the study for the adaptive J or noise dependent J estimation is further required.

• 소음진동
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• 제8권5호
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• pp.887-899
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• 1998

It has been resulted that Lagrange multiplier method with statistical approach was superior to traditional harmonic balance method in identifying the nonlinear loudspeaker parameters when output signals were contaminated with Gaussian random noise. We have known that the displacement-dependent characteristic values of nonlinear parameters identified by traditional harmonic balance method were estimated less than original values by the increase of output noise and the stiffness coefficients were very sensitive to output noise. Also, by the sensitivity analysis we have verified that the harmonic distortions in acoustic radiation was mainly due to nonlinearity of force factor caused by uneven magnetic fields and that reducing the nonlinearity of damping coefficients were very effective for improving second harmonic distrotion of acoustic radiation.

• The Journal of the Acoustical Society of Korea
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• 제27권1E호
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• pp.1-10
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• 2008

A noise suppression algorithm is proposed for nonstationary noisy environments. The proposed algorithm is different from the conventional approaches such as the spectral subtraction algorithm and the minimum statistics noise estimation algorithm in that it classifies speech and noise signals in time-frequency bins. It calculates the ratio of the variance of the noisy power spectrum in time-frequency bins to its normalized time-frequency average. If the ratio is greater than an adaptive threshold, speech is considered to be present. Our adaptive algorithm tracks the threshold and controls the trade-off between residual noise and distortion. The estimated clean speech power spectrum is obtained by a modified gain function and the updated noisy power spectrum of the time-frequency bin. This new algorithm has the advantages of simplicity and light computational load for estimating the noise. This algorithm reduces the residual noise significantly, and is superior to the conventional methods.

• 제어로봇시스템학회논문지
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• 제13권3호
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• pp.224-229
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• 2007

This paper presents a camera calibration method using several images for three dimensional measurement applications such as stereo systems, mobile robots, and visual inspection systems in factories. Conventional calibration methods that use single image suffer from errors related to reference point extraction in image, lens distortion, and numerical analysis of nonlinear optimization. The camera parameter values obtained from images of same camera is not same even though we use same calibration method. The camera parameters that are obtained from several images of different view for a calibration target is usaully not same with large error values and we can not assume a special probabilistic distribution when we estimate the parameter values. In this paper, the median value of camera parameters from several images is used to improve estimation of the camera values in an iterative step with nonlinear optimization. The proposed method is proved by experiments using real images.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.20-22
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• 2007

The H.264/AVC standard developed by the joint Video Team (JVT) provides better coding efficiency than previous standards. The new emerging H.264/AVC employs variable block size motion estimation using multiple reference frame with 1/4-pel MV(Motion Vector) accuracy. These techniques are a important feature to accomplish higher coding efficiency. However, these techniques are increased overall computational complexity. To overcome this problem, this paper proposes advanced fast mode decision suited for variable block size by classifying inter mode based on Rate Distortion Optimization(RDO) technique. Proposed algorithm is going to use to implement H/W structure for fast mode decision. The experimental results shows that the proposed algorithm provides significant reduction computational complexity without any noticeable coding loss and additional computation. Entire computational complexity is decreased about 30%.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2250-2257
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• 2004

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine's hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the TaeKwanRyung test site are presented using three-month wind data from a reference meteorological mast and the other mast temporarily installed at the site of wind turbine. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.

• 방송공학회논문지
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• 제18권2호
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• pp.140-148
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• 2013

Median Dark Channel Prior를 이용하여 안개를 제거하는 방법은 비교적 빠르고 정확한 전달량 맵을 만들어 안개를 제거한다. 그러나 기존의 안개 제거 알고리즘은 RGB 색 공간에서 수행되기 때문에 색상의 왜곡 오류가 생긴다. 본 논문에서는 HSI 색 공간에서 안개 영상의 색상의 정확도를 측정하여 색상의 왜곡을 보정하는 방법을 제안한다. 실험을 통해 제안된 방법은 기존 방법으로 안개 제거 시 색상이 왜곡 되는 현상을 현저히 감소시켰다.

• 음성과학
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• 제10권3호
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• pp.263-277
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• 2003

One of major problems in speech recognition is performance degradation due to the mismatch between the training and test environments. Recently, Stereo-based Piecewise LInear Compensation for Environments (SPLICE), which is frame-based bias removal algorithm for cepstral enhancement using stereo training data and noisy speech model as a mixture of Gaussians, was proposed and showed good performance in noisy environments. In this paper, we propose several methods to improve the conventional SPLICE. First we apply Cepstral Mean Subtraction (CMS) as a preprocessor to SPLICE, instead of applying it as a postprocessor. Secondly, to compensate residual distortion after SPLICE processing, two-stage SPLICE is proposed. Thirdly we employ phonetic information for training SPLICE model. According to experiments on the Aurora 2 database, proposed method outperformed the conventional SPLICE and we achieved a 50% decrease in word error rate over the Aurora baseline system.