• Smart Structures and Systems
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• 제11권6호
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• pp.589-604
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• 2013

Identification of damage has become an evolving area of research over the last few decades with increasing the need of online health monitoring of the large structures. The visual damage detection can be impractical, expensive and ineffective in case of large structures, e.g., offshore platforms, offshore pipelines, multi-storied buildings and bridges. Damage in a system causes a change in the dynamic properties of the system. The structural damage is typically a local phenomenon, which tends to be captured by higher frequency signals. Most of vibration-based damage detection methods require modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties such as natural frequencies and mode shapes are not such good sensitive indication of structural damage. Identification of damaged jacket type offshore platform members, based on wavelet packet transform is presented in this paper. The jacket platform is excited by simple wave load. Response of actual jacket needs to be measured. Dynamic signals are measured by finite element analysis result. It is assumed that this is actual response of the platform measured in the field. The dynamic signals first decomposed into wavelet packet components. Then eliminating some of the component signals (eliminate approximation component of wavelet packet decomposition), component energies of remained signal (detail components) are calculated and used for damage assessment. This method is called Detail Signal Energy Rate Index (DSERI). The results show that reduced wavelet packet component energies are good candidate indices which are sensitive to structural damage. These component energies can be used for damage assessment including identifying damage occurrence and are applicable for finding damages' location.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1880-1884
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• 2004

The wavelet packet transform has been applied for QRS detection with squaring, window integration, and impulse filter techniques to cut down the false detection of QRS complex. This real time QRS detection has been performed on Simulink and Matlab. The correct QRS detection rates have reached to 99.75% in the experiment with 15 sets of ECG data from European ST-T database which are kept in Physionet.

• 전기학회논문지
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• 제57권8호
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• pp.1478-1483
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• 2008

In this paper, a digital watermarking method using the WPT (Wavelet Packet Transform) is proposed. The proposed algorithm transforms the input image by using the WPT and inserts the watermark by using the quad-tree algorithm and Cox's algorithm. The experiments for evaluating the performances of the proposed algorithm is carried out by inserting a watermark in each wavelet packet transform step and by inserting a watermark into the lowest frequency domain (LL). As a simulation result, the performance of the insertion of the watermark into the 6 levels of WPT is better than that of other cases. In addition, about $30{\sim}60%$ of all watermarks are inserted into the LL band, the correlation value is improved though the PSNR performance decreases $1{\sim}2dB$.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권3호
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• pp.124-130
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• 2006

A wavelet-based image compression system allowing both lossless and lossy image compression is proposed in this paper. The proposed algorithm consists of the two stages. The first stage uses the wavelet packet transform and the quad-tree coding scheme for the lossy compression. In the second stage, the residue image taken between the original image and the lossy reconstruction image is coded for the lossless image compression by using the integer wavelet transform and the context based predictive technique with feedback error. The proposed wavelet-based algorithm, allowing an optional lossless reconstruction of a given image, transmits progressively image materials and chooses an appropriate wavelet filter in each stage. The lossy compression result of the proposed algorithm improves up to the maximum 1 dB PSNR performance of the high frequency image, compared to that of JPEG-2000 algorithm and that of S+P algorithm. In addition, the lossless compression result of the proposed algorithm improves up to the maximum 0.39 compression rates of the high frequency image, compared to that of the existing algorithm.

• Structural Engineering and Mechanics
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• 제37권6호
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• pp.575-592
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• 2011

For seismic resistant design of critical structures, a dynamic analysis, either response spectrum or time history is frequently required. Owing to the lack of recorded data and the randomness of earthquake ground motion that may be experienced by structure in the future, usually it is difficult to obtain recorded data which fit the requirements (site type, epicenteral distance, etc.) well. Therefore, the artificial seismic records are widely used in seismic designs, verification of seismic capacity and seismic assessment of structures. The purpose of this paper is to develop a numerical method using Artificial Neural Network (ANN) and wavelet packet transform in best basis method which is presented for the decomposition of artificial earthquake records consistent with any arbitrarily specified target response spectra requirements. The ground motion has been modeled as a non-stationary process using wavelet packet. This study shows that the procedure using ANN-based models and wavelet packets in best-basis method are applicable to generate artificial earthquakes compatible with any response spectra. Several numerical examples are given to verify the developed model.

• 한국음향학회지
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• 제25권7호
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• pp.325-332
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• 2006

본 논문은 인지 모델과 웨이블릿 패킷 변환을 이용하여 단일 채널에서 유색잡음 또는 비정지적 성격의 잡음을 제거하는데 목적을 두고 있다. 이러한 잡음은 부대역을 나누어 접근해야하며, 잔여잡음과 음성의 왜곡으로 인한 문제를 해결하기 위해 웨이블릿 패킷 변환 후 웨이블릿 계수 문턱값을 적절히 개선해야 한다. 본 논문에서 부대역은 웨이블릿 패킷변환 후에 스케일과 임계대역을 매칭하여 설계하였으며, 웨이블릿 계수 문턱값은 세그멘탈 신호대잡음비 (seg_SNR)와 노이즈마스킹 임계값 (Noise Masking Threshold W)을 이용하여 적응적으로 계산했다. 결과적으로 TTA 표준인 EVRC 잡음 제거기와 유사한 성능을 가졌으며, 웨이블릿 변환 후 웨이블릿 계수에 Universal 문턱값을 적용하는 것보다 PESQ-MOS 값이 0.29 높았다. 인코딩과 디코딩 후 PESQ-MOS 값은 EVRC 잡음 제거기보다 0.23 정도 우수한 성능을 가졌다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.594-596
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• 1999

It is extremely important to compress a very large multimedia data under the currently used communication networks because of the forthcoming high fast multimedia informations. Wavelets are very popular and useful mathematical tool in the field of signal processing recently. In this paper, signal compression methods using the wavelet packet transform are compared with the other compression method under same threshold condition. As the result, the compression of using the wavelet packet transform is much more effective than the other compressing methods.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.733-736
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• 2003

본 논문은 웨이블릿 패킷과 노이즈 분산에 의한 영상의 복원에 관한 연구이다. 영상을 노이즈제거 하기 위해 웨이블릿 패킷변환하고 임계값 설정은 노이즈의 분산에 기반한 절대평균값을 적용하였다. 실험결과 단순 웨이블릿 변환을 적용한 영상복원 결과보다 10%, 웨이블릿 패킷 기반의 노이즈 제거 기법보다 5％ 이상 개선되었다.

• 한국컴퓨터정보학회논문지
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• 제8권3호
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• pp.61-65
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• 2003

디지털 영상의 저작권 보호를 위해 PIM을 이용한 웨이블릿 패킷 기반의 새로운 워터마킹 방법을 제안한다. 웨이블릿 패킷 계수를 블록으로 나누고 PIM을 이용하여 각 블록의 복잡도를 계산한다. 인간의 시각 특성은 복잡한 영역에서는 변화에 둔감하므로 복잡도를 나타내는 PIM에 의해 선택된 계수에 워터마크를 삽입하여 비가시성을 높인다. 실험결과는 제안된 알고리즘을 이용한 워터마킹이 JPEG, SPIHT와 같은 손실 영상 압축, 미디언 필터링 등의 일반적인 영상처리에도 견고함을 보여준다. 특히 고주파 성분이 많이 포함되어 있는 영상을 고압축하는 경우에 좋은 성능을 보여준다.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권11호
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• pp.673-679
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• 2005

This Paper presents the 3D wavelet transformation based video compression system, which possesses the capability of progressive transmission by increasing resolution and increasing rate for multimedia applications. The 3D wavelet packet based video compression system removes the temporal correlation of the input sequences using the motion compensation filter and decomposes the spatio-temporal subband using the spatial wavelet packet transformation. The proposed system allocates the higher bit rate to the low frequency image of the 3D wavelet sequences and improves the 0.49dB PSNR performance of the reconstructed image in comparison with that of H.263. In addition to the limitation on the propagation of the motion compensation error by the 3D wavelet transformation, the proposed system progressively transmits the input sequence according to the resolution and rate scalability.