• Title/Summary/Keyword: Wavelet transform

Search Result 2,025, Processing Time 0.099 seconds

Active interface debonding detection of a Concrete Filled Tube (CFT) column by modal parameters and Continuous Wavelet Transform (CWT) technique

  • Younesi, Adel;Rezaifar, Omid;Gholhaki, Majid;Esfandiari, Akbar
    • Structural Monitoring and Maintenance
    • /
    • v.8 no.1
    • /
    • pp.69-90
    • /
    • 2021
  • In recent years, damage detection methods have been significantly increased in civil and mechanical structures. One of the most widely used and relatively new methods of signal processing is the method based on wavelet transform; with the help of this powerful tool, the damage in the structures can be detected in the early stages of damage formation, in order to prevent a larger damage event. In this paper, we have investigated the debonding damage of active surfaces in Concrete-Filled Tube (CFT) columns, which greatly reduces the effect of enclosure on concrete and decreases the bearing capacity of these tubes with the help of wavelet transformation (Discrete Wavelet Transform and Continuous Wavelet Transform). The debonding damage of the active surfaces was evaluated using wavelet types, and the occurrence and location of the damage were detected based on variations in frequency and mode shapes. The above studies have been done for the first six modes of the CFT column. The results of the analyzes indicate that the wavelet transform tool is very capable of detecting the occurrence and location of the damage and is able to detect high-level debonding damage in one side of the column that creates curvature and slight jump in the shape of the mode.

The Detection of Voltage Sag using Wavelet Transform (웨이브렛 변환을 이용한 Voltage Sag 검출)

  • Kim, Cheol-Hwan;Go, Yeong-Hun
    • The Transactions of the Korean Institute of Electrical Engineers A
    • /
    • v.49 no.9
    • /
    • pp.425-432
    • /
    • 2000
  • Wavelet transform is a new method fro electric power quality analysis. Several types of mother wavelets are compared using voltage sag data. Investigations on the use of some mother wavelets, namely Daubechies, Symlets, Coiflets, Biorthogonal, are carried out. On the basis of extensive investigations, optimal mother wavelets for the detection of voltage sag are chosen. The recommended mother wavelet is 'Daubechies 4(db4)' wavelet. 'db4', the most commonly applied mother wavelet in the power quality analysis, can be used most properly in disturbance phenomena which occurs rapidly for a short time. This paper presents a discrete wavelet transform approach for determining the beginning time and end time of voltage sags. The technique is based on utilising the maximum value of d1(at scale 1) coefficients in multiresolution analysis(MRA) based on the discrete wavelet transform. The procedure is fully described, and the results are compared with other methods for determining voltage sag duration, such as the RMS voltage and STFT(Short-Time Fourier Transform) methods. As a result, the voltage sag detection using wavelet transform appears to be a reliable method for detecting and measuring voltage sags in power quality disturbance analysis.

  • PDF

Structural time-varying damage detection using synchrosqueezing wavelet transform

  • Liu, Jing-Liang;Wang, Zuo-Cai;Ren, Wei-Xin;Li, Xing-Xin
    • Smart Structures and Systems
    • /
    • v.15 no.1
    • /
    • pp.119-133
    • /
    • 2015
  • This paper proposed a structural time-varying damage detection method by using synchrosqueezing wavelet transform. The instantaneous frequencies of a structure with time-varying damage are first extracted using the synchrosqueezing wavelet transform. Since the proposed synchrosqueezing wavelet transform is invertible, thus each individual component can be reconstructed and the modal participation factor ratio can be extracted based on the amplitude of the analytical signals of the reconstructed individual components. Then, the new time-varying damage index is defined based on the extracted instantaneous frequencies and modal participation factor ratio. Both free and forced vibrations of a classical Duffing nonlinear system and a simply supported beam structure with abrupt and linear time-varying damage are simulated. The proposed synchrosqueezing wavelet transform method can successfully extract the instantaneous frequencies of the damaged structures under free vibration or vibration due to earthquake excitation. The results also show that the defined time-varying damage index can effectively track structural time-varying damage.

A Study on Noise Removal Using Over-sampled Discrete Wavelet Transforms (과표본화 이산 웨이브렛 변환의 잡음제거에 관한 연구)

  • Jee, Innho
    • The Journal of the Institute of Internet, Broadcasting and Communication
    • /
    • v.19 no.1
    • /
    • pp.69-75
    • /
    • 2019
  • The standard application area of over-sampled discrete wavelet transform is noise removal technology for digital images. Comparing dual density discrete wavelet transform with dual tree discrete wavelet transform, we have almost similar characteristics. In this paper, several discrete wavelet transforms are accomplished on digital image existing with noise, noises are removed with threshold processing algorithm on subband, performance evaluation experiments of the reconstructed images are accomplished. If we decide appropriate threshold value, the effect noise removal is possible. In this paper, we can certified that the suggested algorithm of 3-direction separable processing with 2 dimension dual density discrete wavelet transform is superior to several experiment results.

A Development of Water Demand Forecasting Model Based on Wavelet Transform and Support Vector Machine (Wavelet Transform 방법과 SVM 모형을 활용한 상수도 수요량 예측기법 개발)

  • Kwon, Hyun-Han;Kim, Min-Ji;Kim, Oon Gi
    • Journal of Korea Water Resources Association
    • /
    • v.45 no.11
    • /
    • pp.1187-1199
    • /
    • 2012
  • A hybrid forecasting scheme based on wavelet decomposition coupled to a support vector machine model is presented for water demand series that exhibit nonlinear behavior. The use of wavelet transform followed by the SVM model of each leading component is explored as a model for water demand data. The proposed forecasting model yields better results than a traditional ARIMA time series forecasting model in terms of self-prediction problem as well as reproducing the properties of the observed water demand data by making use of the advantages of wavelet transform and SVM model. The proposed model can be used to substantially and significantly improve the water demand forecasting and utilized in a real operation.

The Applicability for Earth Surface Monitoring Based on 3D Wavelet Transform Using the Multi-temporal Satellite Imagery (다중시기 위성영상을 이용한 3차원 웨이블릿 변환의 지구모니터링 응용가능성 연구)

  • Yoo, Hee-Young;Lee, Ki-Won
    • Journal of the Korean earth science society
    • /
    • v.32 no.6
    • /
    • pp.560-574
    • /
    • 2011
  • Satellite images that have been obtained periodically and continuously are very effective data to monitor the changes of Earth's surface. Traditionally, the studies on change detection using satellite images have mainly focused on comparison between two results after analyzing two images respectively. However, the interests in researches to catch smooth trends and short duration events from continual multi-temporal images have been increased recently. In this study, we introduce and test an approach based on 3D wavelet transform to analyze the multi-temporal satellite images. 3D wavelet transform can reduce the dimensions of data conserving main trends. Also, it is possible to extract important patterns and to analyze spatial and temporal relations with neighboring pixels using 3D wavelet transform. As a result, 3D wavelet transform is useful to capture the long term trends and short-term events rapidly. In addition, we can expect to get new information through sub-bands of 3D wavelet transform which provide different information by decomposed direction.

Double Integration of Measured Acceleration Record using the Concept of Modified Wavelet Transform (수정된 웨이블릿 변환 개념을 이용한 계측 가속도 기록의 이중 적분법)

  • 이형진;박정식
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.7 no.5
    • /
    • pp.11-17
    • /
    • 2003
  • It is well known that the double integration of measured acceleration records is one of the most difficult signal processing, particularly in the measurements on civil engineering structures, The measured accelerations of civil engineering structures are usually non-stationary and contain non-gaussian low-frequency noises, which can be significant causes of numerical instabilities in double Integration, For the de-noising of this kind of signals, wavelet transform can be very effective because of its inherent processing features for non-stationary signals, In this paper, the de-noising algorithm for the double integration is proposed using the modified wavelet transform, which is extended version of ordinary wavelet transform to process non-gaussian and low-frequency noises, using the median filter concept, The example studies show that the integration can be improved by the proposed method.

Enhanced Wavelet Transform-based CELP Coder with Band Selection and Selective VQ (대역 선택 구조와 선택적 벡터 양자화를 이용한 개선된 웨이브릿 변화형 CELP 보호화기)

  • Chang, Dong-Il;Cho, Young-Kwon;Ann, Sou-Guil
    • The Journal of the Acoustical Society of Korea
    • /
    • v.14 no.1E
    • /
    • pp.46-55
    • /
    • 1995
  • In this paper, we present a new wavelet transform-based CELP coder, called band selection wavelet transform CELP (BS-WTCELP) operated at 4.8 kbps. The proposed algorithm uses a band selection scheme of frequency bands of wavelet transform and selective vector quantization (VQ). The band selection and selective VQ structure is implemented by using a classified VQ structure. The proposed algorithm has about 0.5-1.0 dB improvement in segmental SNR compared with the conventional CELP that uses the random codebook search, while is has significantly reduced computational and storage complexity. Many experimental results have shown that the proposed algorithm is more suitable for most real-applications than the conventional CELP and wavelet transform CELP.

  • PDF

Study on the Prediction of Daily TOC Data by Using Wavelet Transform and Artificial Neural Networks (웨이블렛 변환과 인공신경망을 이용한 일 TOC 자료의 예측에 관한 연구)

  • Gwak, Pil Jeong;Oh, Chang Ryol;Jin, Young Hoon;Park, Sung Chun
    • Journal of Korean Society on Water Environment
    • /
    • v.22 no.5
    • /
    • pp.952-957
    • /
    • 2006
  • The present study applied wavelet transform and artificial neural networks (ANNs) for the prediction of daily TOC data. TOC data were transformed into denoised data by the wavelet transform and the noise-reduced data were used for the prediction model by artificial neural networks. For the application of wavelet transform, Daubechies wavelet of order 10 ('db10') was used as a basis function and decomposed the TOC data up to fifth level with five detail components and one approximation component. ANNs were calibrated with the input data of the segregated TOC data corresponding to the details from second to fifth level and the approximation. Consequently, the ANNs model for the prediction of daily TOC data showed the best result when it had seventeen hidden nodes in its layer.

A Study on the EMI Signal Analysis and Denoising Using a Wavelet Transform (웨이브렛 변환을 이용한 EMI 신호해석 및 잡음제거에 관한 연구)

  • 윤기방;박제헌;김기두
    • Journal of the Korean Institute of Telematics and Electronics T
    • /
    • v.35T no.3
    • /
    • pp.37-45
    • /
    • 1998
  • In this paper, the different frequency component and time informations from an EMI signal are extracted simultaneously using a wavelet transform and the results of transform in the time and frequency domain are analyzed. Frequencies are extracted from the EMI signal by performing the multiresolution analysis using the Daubechies-4 filter coefficients and the time information through the results of wavelet transform. We have tried the correlation analysis to evaluate the results of wavelet transform. We have chosen the optimal wavelet function for an object signal by comparing the transformed results of various wavelet functions and verified the simulation examples of waveform and harmonic analysis using a wavelet transform. We have proved the denoising effect to the EMI signal using the soft thresholding technique.

  • PDF