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    Wyświetlanie 1-11 z 11
    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
    Powiązania:
    https://bibliotekanauki.pl/articles/280431.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    damage
    plate
    continuous wavelet transform
    discrete wavelet transform
    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.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2019, 57, 2; 501-518
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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
    Powiązania:
    https://bibliotekanauki.pl/articles/2055029.pdf
    Data publikacji:
    2020
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    viscous damping formulation
    optimum frequencies
    continuous wavelet transform
    dominant frequency
    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.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2020, 58, 3; 585--598
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Deep Classifiers and Wavelet Transformation for Fake Image Detection
    Autorzy:
    Osowski, Stanislaw
    Golgowski, Maciej
    Powiązania:
    https://bibliotekanauki.pl/articles/27312950.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    continuous wavelet transform
    convolutional neural
    networks
    deep fake
    ensemble of classifiers
    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.
    Źródło:
    Journal of Telecommunications and Information Technology; 2023, 4; 1--8
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Are Stock Prices Hedge Against Inflation? A Revisit over Time and Frequencies in India
    Autorzy:
    Bhanja, Niyati
    Dar, Arif Billah
    Tiwari, Aviral Kumar
    Powiązania:
    https://bibliotekanauki.pl/articles/483267.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Stock prices
    inflation
    Fisher effect
    Indian stock markets
    continuous wavelet transform
    wavelet coherency
    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.
    Źródło:
    Central European Journal of Economic Modelling and Econometrics; 2012, 4, 3; 199-213
    2080-0886
    2080-119X
    Pojawia się w:
    Central European Journal of Economic Modelling and Econometrics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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
    Powiązania:
    https://bibliotekanauki.pl/articles/1841303.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
    Tematy:
    scalogram
    continuous wavelet transform
    discrete wavelet transform
    diagnostics
    skalogram
    przekształcenie Falkowe dyskretne
    przekształcenie Falkowe ciągłe
    diagnostyka
    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.
    Źródło:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2020, 10, 3; 52-55
    2083-0157
    2391-6761
    Pojawia się w:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Radial internal clearance analysis in ball bearings
    Autorzy:
    Ambrożkiewicz, Bartłomiej
    Syta, Arkadiusz
    Meier, Nicolas
    Litak, Grzegorz
    Georgiadis, Anthimos
    Powiązania:
    https://bibliotekanauki.pl/articles/1841795.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
    Tematy:
    ball bearings
    radial internal clearance
    statistical analysis
    recurrence
    fast fourier transform
    continuous wavelet transform
    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.
    Źródło:
    Eksploatacja i Niezawodność; 2021, 23, 1; 42-54
    1507-2711
    Pojawia się w:
    Eksploatacja i Niezawodność
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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
    Powiązania:
    https://bibliotekanauki.pl/articles/24200817.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
    Tematy:
    deep learning
    continuous wavelet transform
    improved channel attention mechanism
    multi-conditions
    convolutional neural network
    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.
    Źródło:
    Eksploatacja i Niezawodność; 2023, 25, 1; art. no. 16
    1507-2711
    Pojawia się w:
    Eksploatacja i Niezawodność
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Time invariant property of weighted circular convolution and its application to continuous wavelet transform
    Autorzy:
    Yi, Hua
    Ru, Yu-Le
    Dai, Yin-Yun
    Powiązania:
    https://bibliotekanauki.pl/articles/2086853.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    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
    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.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 4; e137726, 1--9
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An application of continuous wavelet transform and wavelet coherence for residential power consumer load profiles analysis
    Autorzy:
    Kapler, Piotr
    Powiązania:
    https://bibliotekanauki.pl/articles/2086818.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    residential power consumers
    load profiles
    power demand
    continuous wavelet transform
    wavelet coherence
    odbiorcy energii lokalni
    zapotrzebowanie na energię
    profil obciążenia
    ciągła transformata falkowa
    spójność falkowa
    Opis:
    Load profiles of residential consumers are very diverse. This paper proposes the usage of a continuous wavelet transform and wavelet coherence to perform analysis of residential power consumer load profiles. The importance of load profiles in power engineering and common shapes of profiles along with the factors that cause them are described. The continuous wavelet transform and wavelet coherence has been presented. In contrast with other studies, this research has been conducted using detailed (not averaged) load profiles. Presented load profiles were measured separately on working day and weekend during winter in two urban households. Results of applying the continuous wavelet transform for load profiles analysis are presented as coloured scalograms. Moreover, the wavelet coherence was used to detect potential relationships between two consumers in power usage patterns. Results of coherence analysis are also presented in a colourful plots. The conducted studies show that the Morlet wavelet is slightly better suitable for load profiles analysis than the Meyer’s wavelet. Research of this type may be valuable for a power system operator and companies selling electricity in order to match their offer to customers better or for people managing electricity consumption in buildings.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; art. no. e136216, 1--8
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An application of continuous wavelet transform and wavelet coherence for residential power consumer load profiles analysis
    Autorzy:
    Kapler, Piotr
    Powiązania:
    https://bibliotekanauki.pl/articles/2090695.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    residential power consumers
    load profiles
    power demand
    continuous wavelet transform
    wavelet coherence
    odbiorcy energii lokalni
    zapotrzebowanie na energię
    profil obciążenia
    transformata falkowa ciągła
    spójność falkowa
    Opis:
    Load profiles of residential consumers are very diverse. This paper proposes the usage of a continuous wavelet transform and wavelet coherence to perform analysis of residential power consumer load profiles. The importance of load profiles in power engineering and common shapes of profiles along with the factors that cause them are described. The continuous wavelet transform and wavelet coherence has been presented. In contrast with other studies, this research has been conducted using detailed (not averaged) load profiles. Presented load profiles were measured separately on working day and weekend during winter in two urban households. Results of applying the continuous wavelet transform for load profiles analysis are presented as coloured scalograms. Moreover, the wavelet coherence was used to detect potential relationships between two consumers in power usage patterns. Results of coherence analysis are also presented in a colourful plots. The conducted studies show that the Morlet wavelet is slightly better suitable for load profiles analysis than the Meyer’s wavelet. Research of this type may be valuable for a power system operator and companies selling electricity in order to match their offer to customers better or for people managing electricity consumption in buildings.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; e136216, 1--8
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The application of time-frequency methods of acoustic signal processing in the diagnostics of tram drive components
    Autorzy:
    Mokrzan, Daniel
    Nowakowski, Tomasz
    Szymański, Grzegorz M.
    Powiązania:
    https://bibliotekanauki.pl/articles/27322536.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    tram drive diagnostics
    time-frequency methods
    short-time fourier transform
    continuous wavelet transform
    acoustic pressure
    cepstrum
    diagnostyka napędu tramwajowego
    napęd tramwajowy
    metody czasowo-częstotliwościowe
    transformacja falkowa
    ciśnienie akustyczne
    Opis:
    The paper presents the course of investigations and the analysis of the possibility of applying selected methods of time frequency processing of non-stationary acoustic signals in the assessment of the technical condition of tram drive components, as well as a new combined method proposed by the authors. An experiment was performed in the form of a pass-by test of the acoustic pressure generated by a Solaris Tramino S105p tram. A comparative analysis has been carried out for an efficient case and a case with damage to the traction gear of the third bogie in the form of broken gear teeth. The recorded signal was analyzed using short-time Fourier transform (STFT) and continuous wavelet transform (CWT). It was found that the gear failure causes an increase in the sound level generated by a given bogie for frequencies within the range of characteristic frequencies of the tested device. Due to the limitations associated with the fixed window resolution in STFT and the inability to directly translate scales to frequencies in CWT, it was found that these methods can be helpful in determining suspected damage, but are too imprecise and prone to errors when the parameters of both transforms are poorly chosen. A new CWT-Cepstrum method was proposed as a solution, using the wavelet transform as a pre-filter before cepstrum signal processing. With a sampling rate of 8192 Hz, a db6 mother wavelet, and a scale range of 1:200, the new method was found to infer the occurrence of damage in an interpretation-free manner. The results were validated on an independent pair of trams of the same model with identical damage and as a reference on a pair of undamaged trams demonstrating that the method can be successfully replicated for different vehicles.
    Źródło:
    Archives of Transport; 2023, 68, 4; 55--75
    0866-9546
    2300-8830
    Pojawia się w:
    Archives of Transport
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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