Temat: Wavelet Transform - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Experimental damage assessment of support condition for plate structures using wavelet transform
Autorzy:: Abdulkareem, Muyideen
Bakhary, Norhisham
Vafaei, Mohammadreza
Md Noor, Norhazilan
Abd Samat, Roslida
Tematy:: damage
plate
continuous wavelet transform
discrete wavelet transform; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/280431.pdf Link otwiera się w nowym oknie
Opis:: Wavelet transforms (WTs) have gained popularity due to their ability to identify singularities by decomposing mode shapes of structures. In VBDD, the support condition of a structure influences structural responses and modal properties. In fact, the structural responses and modal properties are a lot more sensitive to changing boundary conditions than to crack and fatigue damage, resulting in inaccurate damage detection results. Therefore, in this study, sensitivity tests to estimate a suitable distance range which allows damage detection by imposing single support damage are carried out. The estimated appropriate distance is then applied to detect damage at multiple supports. This involved the applicability of response acceleration of plate structures to support assessment by applying continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The damage cases have been introduced by releasing bolts at specified fixed supports of the plate to simulate the damage. The response accelerations of the rectangular plate at points close to the supports were measured and decomposed using CWT and DWT to assess the structural integrity of each support. The results showed that an appropriate distance range was necessary for accurate damage detection, and both, CWT and DWT could provide reliable outputs. However, the first- and fourth-level detail coefficients of DWT failed to indicate damage in some cases. A more detailed investigation of the effect of different wavelet scale ranges on damage detection using CWT demonstrated that the accuracy of damage detection increased as the scale decreased.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Selected aspects in the analysis of the combustion process using wavelet transform
Wybrane aspekty w analizie procesu spalania z wykorzystaniem przekształceń falkowych
Autorzy:: Grądz, Żaklin
Tematy:: scalogram
continuous wavelet transform
discrete wavelet transform
diagnostics
skalogram
przekształcenie Falkowe dyskretne
przekształcenie Falkowe ciągłe
diagnostyka; Pokaż więcej
Wydawca:: Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Powiązania:: https://bibliotekanauki.pl/articles/1841303.pdf Link otwiera się w nowym oknie
Opis:: The complexity of changes occurring in the flame during the combustion process has a direct influence on the quantity and qualityof the combustion products. The presented measurement data pertaining to the changes in flame luminosity were recorded using a specialized monitoring system. These signals from the combustion ofsuch fuels as pulverized coal and mazoutwere recorded with high sampling rate. The paper presented the analysis of changes in flame luminosity for different fuels using continuous and discrete wavelet transform. The main aim of the studies was to determine the scale values, which enable differentiating between the type of combusted fuel. The results of studies were presented in the form of scalograms.
Złożoność zmian zachodzących w płomieniu w trakcie procesu spalania różnych paliw ma bezpośredni wpływ na ilość i jakość powstałych produktów spalania. Przedstawione w pracy dane pomiarowe zmian intensywności świecenia płomienia zostały zarejestrowaneprzy użyciu specjalistycznego systemu monitorującego. Sygnały te,dla procesu spalania,zostały zarejestrowane z wysoką częstotliwością próbkowania. W artykule przedstawiono analizę zmian intensywności świecenia płomienia dla różnych paliw przy zastosowaniu ciągłego i dyskretnego przekształcenia falkowego. Podstawowym celem badań było określenie wartości skali, na podstawie których możliwe będzie rozróżnienie rodzaju spalanego paliwa. Wyniki badań zostały zaprezentowane w postaci skalogramów.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Are Stock Prices Hedge Against Inflation? A Revisit over Time and Frequencies in India
Autorzy:: Bhanja, Niyati
Dar, Arif Billah
Tiwari, Aviral Kumar
Tematy:: Stock prices
inflation
Fisher effect
Indian stock markets
continuous wavelet transform
wavelet coherency; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/483267.pdf Link otwiera się w nowym oknie
Opis:: In this paper, the stock price-inflation nexus is investigated using the tools of wavelet power spectrum, cross-wavelet power spectrum and cross-wavelet coherency to unravel time and frequency dependent relationships between stock prices and inflation. Our results suggest that for a frequency band between sixteen and thirty two months, there is some evidence of the fisher effect. For rest of the frequencies and time periods however there is no evidence of the fisher effect and it seems stock prices have not played any role as an inflation hedge.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Selection of viscous damping coefficients using the continuous wavelet transform method for a gear system
Autorzy:: Yousfi, Nourhaine
Zghal, Bacem
Akrout, Ali
Walha, Lassaad
Haddar, Mohamed
Tematy:: viscous damping formulation
optimum frequencies
continuous wavelet transform
dominant frequency; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/2055029.pdf Link otwiera się w nowym oknie
Opis:: Viscous damping is frequently used in the equation of motion to present the dissipation mechanism of a mechanical system. The orders of frequencies can be easily selected to determine viscous damping coefficients (VDCs) when the degree of freedom of the structure is low. For complex structures, difficulties in selecting the orders of reference frequencies to obtain reasonable VSCs are encountered. This paper mainly discusses the capability of the CWT method to select optimum frequencies of viscous damping formulation. The proposed procedure considers both the classical Rayleigh, modal and the proposed full model modal damping. The method is validated using a numerical time domain response of a two-stage gear system.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Radial internal clearance analysis in ball bearings
Autorzy:: Ambrożkiewicz, Bartłomiej
Syta, Arkadiusz
Meier, Nicolas
Litak, Grzegorz
Georgiadis, Anthimos
Tematy:: ball bearings
radial internal clearance
statistical analysis
recurrence
fast fourier transform
continuous wavelet transform; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Powiązania:: https://bibliotekanauki.pl/articles/1841795.pdf Link otwiera się w nowym oknie
Opis:: Radial internal clearance (RIC) is one of the most important parameters influencing on rolling bearing exploitation in mechanical systems. Lifetime of rotary machines strongly depends on a condition of applied rolling elements, thus a study on applied clearance is very important in terms of maintenance and reliability. This paper proposes, a novel approach of studying RIC, based on a nonlinear dynamics method called recurrences. The results are confronted with standard analyses, i.e. statistical condition indicators, Fast Fourier Transform and Continuous Wavelet Transform. The application of the mentioned methods allowed us to find the optimal radial clearance for operating bearings. To ensure precise measurements of the clearance, an automated setup for RIC measurements is applied and next mounted in a plummer block and tested to finally measure vibration acceleration. The proposed methods are useful for a condition monitoring and lifetime prediction of bearings or bearing-based systems in which a proper value of radial clearance is crucial.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Deep Classifiers and Wavelet Transformation for Fake Image Detection
Autorzy:: Osowski, Stanislaw
Golgowski, Maciej
Tematy:: continuous wavelet transform
convolutional neural
networks
deep fake
ensemble of classifiers; Pokaż więcej
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/27312950.pdf Link otwiera się w nowym oknie
Opis:: The paper presents a computer system for detecting deep fake images in videos. The system is based on continuous wavelet transformation combined with a set of classifiers composed of a few convolutional neural networks of diversified architectures. Three different forms of forged images taken from the FaceForensics++ database are considered in numerical experiments. The results of experiments involving the proposed system have shown good performance in comparison to other current approaches to this particular problem.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Intelligent fault diagnosis of rolling bearings based on continuous wavelet transform-multiscale feature fusion and improved channel attention mechanism
Autorzy:: Zhang, Jiqiang
Kong, Xiangwei
Cheng, Liu
Qi, Haochen
Yu, Mingzhu
Tematy:: deep learning
continuous wavelet transform
improved channel attention mechanism
multi-conditions
convolutional neural network; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Powiązania:: https://bibliotekanauki.pl/articles/24200817.pdf Link otwiera się w nowym oknie
Opis:: Accurate fault diagnosis is critical to operating rotating machinery safely and efficiently. Traditional fault information description methods rely on experts to extract statistical features, which inevitably leads to the problem of information loss. As a result, this paper proposes an intelligent fault diagnosis of rolling bearings based on a continuous wavelet transform(CWT)-multiscale feature fusion and an improved channel attention mechanism. Different from traditional CNNs, CWT can convert the 1-D signals into 2-D images, and extract the wavelet power spectrum, which is conducive to model recognition. In this case, the multiscale feature fusion was implemented by the parallel 2-D convolutional neural networks to accomplish deeper feature fusion. Meanwhile, the channel attention mechanism is improved by converting from compressed to extended ways in the excitation block to better obtain the evaluation score of the channel. The proposed model has been validated using two bearing datasets, and the results show that it has excellent accuracy compared to existing methods.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Condition Monitoring and Fault Diagnosis of Permanent Magnet Synchronous Motor Stator Winding Using the Continuous Wavelet Transform and Machine Learning
Autorzy:: Pietrzak, Przemysław
Wolkiewicz, Marcin
Tematy:: fault diagnosis
interturn short circuits
continuous wavelet transform
machine learning
permanent magnet synchronous motor; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/58970751.pdf Link otwiera się w nowym oknie
Opis:: Applying the condition monitoring technology to industrial processes can help detect faults in time, minimise their impact and reduce the cost of unplanned downtime. Since the introduction of the Industry 4.0 paradigm, many companies have been investing in the development of such technology for drive systems. Permanent magnet synchronous motors (PMSMs) have recently been used in many industries. Therefore, the issues of condition monitoring of PMSM drives are important. This study proposes and compares diagnostic schemes based on the stator phase currents (SPCSCs) signal for condition monitoring and fault diagnosis of PMSM stator winding faults. The continuous wavelet transform (CWT) is used for the extraction of the symptoms of interturn short circuits in PMSM stator winding. Machine learning algorithms are applied to automate the detection and classification of the faults. The concept for an original and intelligent PMSM stator winding condition monitoring system is proposed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Determination of rail vehicle speed with acoustic signal processed using continuous wavelet transform
Autorzy:: Mokrzan, Daniel
Nowakowski, Tomasz
Szymański, Grzegorz M.
Tematy:: continuous wavelet transform
acoustics
rail vehicle
speed detection
ciągła transformata falkowa
akustyka
pojazd szynowy
wykrywanie prędkości; Pokaż więcej
Wydawca:: Politechnika Poznańska. Instytut Mechaniki Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/58908053.pdf Link otwiera się w nowym oknie
Opis:: The paper presents the course of research and analysis on the possibility of using time-frequency methods of acoustic signal processing to determine the speed of moving rail vehicles. An experiment was conducted in the form of a trackside pass-by test of the acoustic pressure emitted by passing trams representing the rolling stock of the Municipal Transport Company in Poznan. The recorded signal was then processed using the Continuous Wavelet Transform (CWT), resulting in a scalogram that is a variation of the time-frequency characteristics. This made it possible to identify in the signal the travel time of individual bogies and their wheelsets, as well as the most sensitive value of the scale parameter. The waveform of the scalogram fragment for the selected value of the scale parameter was processed using the RMS envelope, and then the peak values were identified. Juxtaposing the obtained results with the knowledge of the structural dimensions of the tested vehicle, it was possible to determine its moving speed. To validate the results of the experiment, photocells located on both sides of the measurement track were used, which generated voltage when the test vehicle passed between them, allowing the determination of its average moving speed. The result of the study was the formulation of a method that can be used to determine the speed of a vehicle based on the time elapsed between the identification in the signal of the components corresponding to the passage of successive sets of wheels.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Time invariant property of weighted circular convolution and its application to continuous wavelet transform
Autorzy:: Yi, Hua
Ru, Yu-Le
Dai, Yin-Yun
Tematy:: continuous wavelet transform
linear convolution
weighted circular convolution
generalized discrete Fourier transform
ciągła transformata falkowa
splot liniowy
splot kołowy ważony
transformata Fouriera uogólniona dyskretna; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/2086853.pdf Link otwiera się w nowym oknie
Opis:: Time invariant linear operators are the building blocks of signal processing. Weighted circular convolution and signal processing framework in a generalized Fourier domain are introduced by Jorge Martinez. In this paper, we prove that under this new signal processing framework, weighted circular convolution also has a generalized time invariant property. We also give an application of this property to algorithm of continuous wavelet transform (CWT). Specifically, we have previously studied the algorithm of CWT based on generalized Fourier transform with parameter 1. In this paper, we prove that the parameter can take any complex number. Numerical experiments are presented to further demonstrate our analyses.
Dostawca treści:: Biblioteka Nauki

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