• 조명전기설비학회논문지
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• 제25권5호
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• pp.73-78
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• 2011

We developed a noise reduction algorithm for the measurement accuracy improvement of a fiber-optic distributed temperaure sensor system. The denoising technique is based on the wavelet transform. The proposed algorithm was applied to a FBG sensor output with the Gaussian line-fitting algorithm to minimize the output noise which originated from the intensity noise of the laser light source and the instability of signal porcessing. We confirmed the feasibility of the denoising algorithm by comparing the measurement results with those obtained with the Gaussian line-fitting algorithm only.

• Nuclear Engineering and Technology
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• 제32권5호
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• pp.485-494
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• 2000

In this work, a fuzzy neural network is used to estimate the relevant sensor signal using other sensor signals. Noise components in input signals into the fuzzy neural network are removed through the wavelet denoising technique . Principal component analysis (PCA) is used to reduce the dimension of an input space without losing a significant amount of information. A lower dimensional input space will also usually reduce the time necessary to train a fuzzy-neural network. Also, the principal component analysis makes easy the selection of the input signals into the fuzzy neural network. The fuzzy neural network parameters are optimized by two learning methods. A genetic algorithm is used to optimize the antecedent parameters of the fuzzy neural network and a least-squares algorithm is used to solve the consequent parameters. The proposed algorithm was verified through the application to the pressurizer water level and the hot-leg flowrate measurements in pressurized water reactors.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.698-708
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• 2018

This article introduces a methodology of designing a wavelet operator suitable for multiscale modeling. The operator matrix transforms states of a multivariable system onto projection space. In addition, it imposes a specific structure on the system matrix in a multiscale environment. To be specific, the article deals with a diagonalizing transform that is useful for decoupled control of a system. It establishes that there exists a definite relationship between the model in the measurement space and that in the projection space. Methodology for deriving the multirate perfect reconstruction filter bank, associated with the wavelet operator, is presented. The efficacy of the proposed technique is demonstrated by modeling the point kinetics nuclear reactor. The outcome of the multiscale modeling approach is compared with that in the single-scale approach to bring out the advantage of the proposed method.

• Smart Structures and Systems
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• 제16권1호
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• pp.213-222
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• 2015

Early detection and precise location of leakage is of great importance for life-cycle maintenance and management of municipal pipeline system. In the past few years, acoustic emission (AE) techniques have demonstrated to be an excellent tool for on-line leakage detection. Regarding the multi-mode and frequency dispersion characteristics of AE signals propagating along a pipeline, the direct cross-correlation technique that assumes the constant AE propagation velocity does not perform well in practice for acoustic leak location. This paper presents an improved cross-correlation method based on wavelet transform, with due consideration of the frequency dispersion characteristics of AE wave and the contribution of different mode. Laboratory experiments conducted to simulate pipeline gas leakage and investigate the frequency spectrum signatures of AE leak signals. By comparing with the other methods for leak location identification, the feasibility and superiority of the proposed method are verified.

• Geomechanics and Engineering
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• 제7권2호
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• pp.149-164
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• 2014

One of the most advanced classes of techniques for ground response analysis is based on the use of Transfer Functions. They represent the ratio of Fourier spectrum of amplitude motion at the free surface to the corresponding spectrum of the bedrock motion and they are applied in frequency domain usually by FFT method. However, Fourier spectrum only shows the dominant frequency in each time step and is unable to represent all frequency contents in every time step and this drawback leads to inaccurate results. In this research, this process is optimized by decomposing the input motion into different frequency sub-bands using Wavelet Multi-level Decomposition. Each component is then processed with transfer Function relating to the corresponding component frequency. Taking inverse FFT from all components, the ground motion can be recovered by summing up the results. The nonlinear behavior is approximated using an iterative procedure with nonlinear soil properties. The results of this procedure show better accuracy with respect to field observations than does the Conventional method. The proposed method can also be applied to other engineering disciplines with similar procedure.

• Journal of the Optical Society of Korea
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• 제15권1호
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• pp.103-108
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• 2011

Recently reported asynchronous-optical-sampling terahertz (THz) time-domain spectroscopy enables high-resolution spectroscopy due to a long time-delay window. However, a long-lasting tail signal following the main pulse is often measured in a time-domain waveform, resulting in spectral fluctuation above a background noise level on a high-resolution THz amplitude spectrum. Here, we adopt the wavelet power spectrum estimation technique (WPSET) to effectively remove the spectral fluctuation without sacrificing spectral features. Effectiveness of the WPSET is verified by investigating a transmission spectrum of water vapor.

• 한국음향학회지
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• 제16권4호
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• pp.64-70
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• 1997

본 논문은 MPEG의 서브밴드 필터링을 웨이블렛 변환으로 대체하였을 때 얼마만큼의 계산량이 감소하는 가를 연구하였다. MPEG 오디오에서는 16비트 PCM 오디오 데이타를 입력으로 받아 서브밴드 필터링후 서브밴드 샘플을 양자화하여 전송하는 것을 기본으로 한다. MPEG의 서브밴드 필터링의 경우 32 대역의 등간격으로 분할한다. 이 경우 32개의 필터가 필요하고 각 필터는 512의 길이를 갖는 필터를 사용한다. 본 연구에서는 분할 대역을 6개로 하고 웨이블렛 필터중 가장 짧은 Haar 필터를 사용하였다. 제안된 시스템은 256kbps 이상의 전송율에서는 MPEG 오디오와 비슷한 수준의 CD 음질을 유지하였으며, 계산량 비교결과 부호화기는 약 40%, 복호화기는 약 70%의 감소를 보였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1098-1101
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• 2004

The ordinary stereo image of an object consists of data of left and right views. Therefore, the left and right image pairs have to be transmitted simultaneously in order to display 3-dimentional video at the remote site. However, due to the twice data in comparing with a monoscopic image of the same object, it needs to be compressed for fast transmission and resource saving. Hence, it needs an effective coding algorithm for compressing stereo image. It was found previously that compressing left and right frames independently will achieve the compression ratio lower than compressing by utilizing the spatial redundancy between both frames. Therefore, in this paper, we study the stereo image compression technique based on the multiresolution wavelet transform using varied disparity-block size for estimation and compensation. The size of disparity-block in the stereo pair subbands are scaling on a coarse-to-fine wavelet coefficients strategy. Finally, the reference left image and residual right image after disparity estimation and compensation are coded by using SPIHT coding. The considered method demonstrates good performance in both PSNR measures and visual quality for stereo image.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.179-182
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• 2001

This paper has been studied a wavelet based still image transmission over the wireless channel. EZW(Embedded Zerotree Wavelet) is an efficient and scalable wavelet based image coding technique, which provides progressive transfer of signal resulted in multi-resolution representation. It reduces therefore the reduce cost of storage media. Although EZW has many advantages, it is very sensitive on error. Because coding are performed in subband by subband, and it uses arithmetic coding which is a kind of variable length coding. Therefore only 1∼2bit error may degrade quality of the entire image. So study of error localization and recovery are required. This paper investigates the use of reversible variable length codes(RVLC) and data partitioning. RVLC are known to have a superior error recovery property due to their two-way decoding capability and data partitioning is essential to applying RVLC. In this work, we show that appropriate data partitioning length for each SNR(Signal-to-Noise Power Ratio) and error localization in wireless channel.

• Journal of Information Processing Systems
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• 제12권1호
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• pp.35-45
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• 2016

To resolve the problems of Poisson/impulse noise, blurriness, and sharpness in degraded X-ray images, a novel and efficient enhancement algorithm based on X-ray image fusion using a discrete wavelet transform is proposed in this paper. The proposed algorithm consists of two basics. First, it applies the techniques of boundary division to detect Poisson and impulse noise corrupted pixels and then uses the Wiener filter approach to restore those corrupted pixels. Second, it applies the sharpening technique to the same degraded X-ray image. Thus, it has two source X-ray images, which individually preserve the enhancement effects. The details and approximations of these sources X-ray images are fused via different fusion rules in the wavelet domain. The results of the experiment show that the proposed algorithm successfully combines the merits of the Wiener filter and sharpening and achieves a significant proficiency in the enhancement of degraded X-ray images exhibiting Poisson noise, blurriness, and edge details.