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1
Content available remote Rotor faults diagnosis by adjustable window function
EN
Several recent studies dealing with new diagnosis methods criticize the classical method of Power Spectral Density by periodogram technique for its drawbacks related to frequency resolution. This is reflected by the appearance of a smoothing and a negative effect following the selected window function. Indeed, this technique is less efficient in the detection of frequency signatures of faults close to a high amplitude harmonic. In addition, it is unable to detect an incipient fault. However, this method has several advantages such as a low computation time and easy programming. To avoid these drawbacks while considering the method advantages, this paper proposes a simple procedure to define precisely the shape parameters of a new window belonging to the raised-cosine family. This procedure uses the characteristics of the stator current spectrum to ensure reliable diagnosis in the case of an incipient fault, while maintaining a quick processing time. The experimental tests carried out prove the effectiveness of the suggested approach in the diagnosis of incipient fault affecting an induction motor.
PL
Kilka ostatnich badań dotyczących nowych metod diagnostycznych krytykuje klasyczną metodę gęstości widmowej mocy techniką periodogramu ze względu na jej wady związane z rozdzielczością częstotliwości. Rzeczywiście, ta technika jest mniej skuteczna w wykrywaniu sygnatur częstotliwości uszkodzeń blisko harmonicznej o dużejj amplitudzie. Ponadto nie jest w stanie wykryć początkowej usterki. Jednak ta metoda ma kilka zalet, takich jak krótki czas obliczeń i łatwe programowanie. Aby uniknąć tych wad, biorąc pod uwagę zalety metody, w niniejszym artykule zaproponowano prostą procedurę precyzyjnego zdefiniowania parametrów kształtu nowego okna należącego do rodziny podniesionych cosinusów. Ta procedura wykorzystuje właściwości widma prądu stojana, aby zapewnić niezawodną diagnozę w przypadku początkowej fazy uszkodzenia, przy jednoczesnym zachowaniu szybkiego czasu przetwarzania. Przeprowadzone testy eksperymentalne dowodzą skuteczności sugerowanego podejścia w diagnozowaniu początkowej fazy uszkodzenia występującej w silnik indukcyjny.
EN
The paper presents the method of assessment of the technical condition of the leading edge of the horizontal stabilizer of an F-16 Block C aircraft made from composite materials. The described method was an experimental measurement of the acoustic pressures generated by the technically operational element and the element with the distorted structural continuity and then a comparison of these pressures in the curves of time and frequency in order to assess how the damage impacts the parameters of the acoustic wave. The test was performed in a dual-channel system, the pressure was induced through impacts on the investigated element with an impact hammer and then, based on the measured induction parameters and the generated acoustic wave, the function of frequency response was calculated, based on which the authors assessed how the structural damage influenced the curve characteristics of the acoustic pressure in the domain of frequency. The described method may be used as an efficient method of non-destructive diagnostics of the airframe elements of an aircraft.
PL
Artykuł przedstawia metodę oceny stanu technicznego krawędzi natarcia statecznika poziomego statku powietrznego F-16 Block C wykonanej z materiałów kompozytowych. Opisywaną metodę stanowił eksperymentalny pomiar ciśnienia akustycznego emitowanego przez element sprawny technicznie oraz element z naruszoną ciągłością struktury, a następnie porównanie ich przebiegu w domenie czasu oraz częstotliwości celem ustalenia w jaki sposób uszkodzenia wpływają na parametry emitowanej fali akustycznej. Badanie dokonywane było dwukanałowo, ciśnienie akustyczne wzbudzane było za pomocą uderzeń w badany element za pomocą młotka modalnego, następnie na podstawie zmierzonych parametrów wzbudzania oraz wywołanego nim fali akustycznej obliczono funkcję odpowiedzi częstotliwości, na podstawie której określono jak uszkodzenie struktury wpływa na przebieg charakterystyki ciśnienia akustycznego w dziedzinie częstotliwości. Opisywana metoda może służyć za skuteczną metodę diagnostyki nieniszczącej elementów płatowca statku powietrznego.
EN
Squirrel cage induction motors suffer from numerous faults, for example cracks in the rotor bars. This paper aims to present a novel algorithm based on Least Squares Support Vector Machine (LS-SVM) for detection partial rupture rotor bar of the squirrel cage asynchronous machine. The stator current spectral analysis based on FFT method is applied in order to extract the fault frequencies related to rotor bar partial rupture. Afterward the LS-SVM approach is established as monitoring system to detect the degree of rupture rotor bar. The training and testing data sets used are derived from the spectral analysis of one stator phase current, containing information about characteristic harmonics related to the partial rupture rotor bar. Satisfactory and more accurate results are obtained by applying LS-SVM to fault diagnosis of rotor bar.
EN
In contrast to traditional systems for monitoring fault of the running gear of the rolling stock, this paper proposes a technology of noise control at the onset of defects. The authors consider the possibility of creating an intelligent system that can perform noise diagnostics with the indication of the beginning of the latent period of the initiation of typical defects preceding faults. To this end, using the noise technology, sets of reference informative attributes are created in the training process. The reference sets, in turn, are used to determine the condition of the object at the beginning of the development of defects by comparing them with current noise estimates. It also allows controlling the dynamics of the development of defects.
EN
Strontium formate dihydrate single crystals have been grown by the slow solvent evaporation method and subjected to 8 MeV electron beam (EB) irradiation at different doses, viz. 1 kGy, 10 kGy, 50 kGy and 100 kGy. The irradiated crystals have been studied by various techniques such as FT-IR, Raman, and UV-Vis-NIR spectral analyses, powder, and high resolution X-ray diffraction, thermogravimetric analysis (TG/DTA) and second harmonic generation (SHG) measurements. The morphological features of the non-irradiated and irradiated crystals were analyzed by SEM and optical microscopy studies. It has been noticed that the SHG efficiency increases while the crystalline perfection and thermal stability of the irradiated crystals decrease with the increase of EB irradiation dose. The results indicate a significant overall tuning of physical properties of strontium formate dihydrate crystals due to irradiation.
EN
The article presents the issue of corporate social responsibility as an instrument of stabilising the macroeconomic situation of a company based on building increased trust and attachment of society to a given company. Developing relationships in a proper way with stakeholders should be a guarantee to make a business an important element of the social structure, thus contributing to mitigating the impact of economic changes on the company's situations. The aim of this work is to examine the impact of selected macroeconomic variables related to the activities of enterprises (in particular. socially responsible enterprises), illustrated in the form of changes in the value of stock market indices (including listed social responsibility indexes). The cross-spectral analysis tool was used to analyse the causality of macroeconomic changes. Changes in the spectral density values of individual variables, as well as the coherence square and phase spectrum values of variables, were analysed. An additional tool was used in the study to create an index of changes in exchange values in order to conduct a comparative analysis of the development of time series relating to individual indices. The data analysed was related to changes in the value of social responsibility indexes, as well as macroeconomic data, for the period from January 2001 to the end of April 2019.
7
Content available remote Stator current spectrum analysis applied on short-circuit fault diagnosis of SRM
EN
Thanks to power electronics innovation, switched reluctance machine are taking place on industrial applications. In this paper we present the short-circuit fault diagnosis between stator turns of the switched reluctance machine by the use of stator current spectral analysis. To do this, we modeled our switched reluctance machine by permeance networks method to which we have associated the of the teeth contour permeance for the calculation of the airgap. The simulation results show the interest and efficiency of the proposed model as well as the stator current spectral analysis technique for the short circuit fault diagnosis of the switched reluctance machine.
PL
W artykule zaprezentowano metodę wykrywania zwarć w silniku reluktancyjnym. Metoda ta bazuje na analizie widmowej prądu stojana.
EN
Position time series from permanent Global Navigation Satellite System (GNSS) stations are commonly used for estimating secular velocities of discrete points on the Earth’s surface. An understanding of background noise in the GNSS position time series is essential to obtain realistic estimates of velocity uncertainties. The current study focuses on the investigation of background noise in position time series obtained from thirteen permanent GNSS stations located in Nepal Himalaya using the spectral analysis method. The power spectrum of the GNSS position time series has been estimated using the Lomb–Scargle method. The iterative nonlinear Levenberg–Marquardt (LM) algorithm has been applied to estimate the spectral index of the power spectrum. The power spectrum can be described by white noise in the high frequency zone and power law noise in the lower frequency zone. The mean and the standard deviation of the estimated spectral indices are […] for north, east and vertical components, respectively. On average, the power law noise extends up to a period of ca. 21 days. For a shorter period, i.e. less than ca. 21 days, the spectra are white. The spectral index corresponding to random walk noise (ca. –2) is obtained for a site located above the base of a seismogenic zone which can be due to the combined effect of tectonic and nontectonic factors rather than a spurious monumental motion. Overall, the usefulness of investigating the background noise in the GNSS position time series is discussed.
EN
In the presented study multi-year time series of changes in the L1 pseudo-range multipath are analysed. Data from 8 stations of the EUREF Permanent Network (EPN) were used in the study. Periodic components present in the signal and their stability over time were analysed. Also, the type of background noise was determined, based on the spectral index. In some cases, the presence of weak components with a 1/2 and 1/3 of the Chandler period has also been found. Time-frequency analysis shows that periodic signals are not stationary in most of the examined cases, and particular signal components occur only temporarily. The analysed signals were char-acterised by pink noise in the lower frequency range and by white noise for higher frequencies, which is also characteristic for time series of coordinates obtained from GNSS measurements.
PL
Zaletami metody HR CS MAS są wysoka czułość, niskie granice wykrywalności, szeroki zakres liniowości oraz ograniczenie przygotowania próbki di minimum, a także odporność na interferencje. Z tego powodu można przypuszczać, że wysokorozdzielcza absorpcyjna spektrometria cząsteczkowa z ciągłym źródłem promieniowania może stać się coraz powszechniej stosowaną techniką oznaczania fluoru w laboratoriach analitycznych.
PL
Elektroencefalografia jest techniką powszechnie stosowaną w diagnostyce medycznej oraz w badaniach. W artykule opisano zasadę pomiarów EEG i scharakteryzowano aparaturę pomiarową oraz metody rejestracji. Artykuł podzielony jest na dwie części. W pierwszej przedstawiono metody rejestracji sygnałów EEG oraz ich zastosowania kliniczne, a w drugiej narzędzia analizy widmowej. W pracy zostały użyte rzeczywiste sekwencje sygnałów EEG określone przez lekarza jako sygnały prawidłowe oraz wskazujące na chorobę (napadowe). Ich analiza została wykonana za pomocą szybkiej transformaty Fouriera oraz dyskretnej transformaty falkowej. Obliczano widmo mocy, a uzyskane średnie wartości mocy spektralnej stanowiły podstawę wskazania stanu patologicznego.
EN
Electroencephalography, as an electrophysiological method to record electrical activity of the brain, is commonly used in medicine and research areas. This article presents theoretical basics of EEG measurement. This method is still being developed. The greatest emphasis is put on improvement of the measuring equipment and recording methods. The solutions to improve hardware and software are still sought. This article is divided into two main parts. The first part explains EEG recording and its clinical applications. Epilepsy is the most common neurological disorder. The future trends in the development of EEG are pointed out. In the second part spectral analysis tools are presented. The EEG signal has nonlinear and nonstationary properties In the paper, real EEG sequences described by a doctor as normal and epileptic (ictal) are used. The analysis is performed using fast Fourier transform and discrete wavelet transform. The power spectrum in each frequency band is calculated. The obtained average power spectral values allow to distinguish epileptic sequences. Spectral analysis is considered to be a potential tool that may aid in the diagnosis of neurological diseases.
EN
The presence of deposits on heat exchange surfaces in condensers and regenerative exchangers of ship and land steam power plants is always connected with the increase of the wall temperature on the water vapor side due to additional thermal resistances resulting from accumulated deposits. This increase always results in an increase in the condensing pressure, which results in the deterioration of the condensation process of the water vapor, leading to thermal degradation of a given heat exchanger. In addition, the resulting deposits form unevenness with a diversified, often stochastic, geometric structure of the surface layer surface, whose measure is most often the roughness parameters, describing the geometric structure of the surface. In addition, the increase in surface roughness of the heat transfer surface on the water vapor side promotes the formation of a thicker layer of condensate, thus worsening the organization of condensate runoff, which results in interference of the thermal degradation phenomenon of a given heat exchange apparatus. As a result, these phenomena lead to a reduction in the efficiency of a given thermal system, and thus entail an increase in the costs of energy conversion and consequently cause an increased degradation of the natural environment. In the article, based on the results of the author’s own experimental research, the types of pollution accumulating on heat exchange surfaces on the water vapor side of heat exchange apparatus in marine and land steam power plants and quantitative measures of the unevenness of the surface layer of these sediments are presented.
EN
In this study, the temperature influence on the spectral responsivity of a Light Emitting Diode (LED) used as a photoreceptor, combined to light source spectrum is correlated to electrical characteristics in order to propose an alternative method to estimate LED junction temperature, regardless of the absolute illumination intensity and based on the direct correlation between the integral of the product of two optical spectra and the photo-generated currents. A laboratory test bench for experimental optical measurements has been set in order to enable any characterizing of photoelectric devices in terms of spectral behaviour, in a wavelength range placed between 400–1000 nm, and of current-voltage characteristics as function of temperature by using two different illumination sources. The temperature is analysed in a range from 5°C up to 85°C, so as to evaluate thermal variation effects on the sensor performance. The photo-generated current of two LEDs with different peak wavelengths has been studied. Research has observed and mathematically analysed what follows: since the photo-generated current strictly depends on the combination between the spectral response of the photoreceptor and the lighting source response, it becomes possible to estimate indirectly the junction temperature of the LEDs by considering the ratio between the photogenerated currents obtained by using two different illumination sources. Such results may for one thing increase knowledge in the fields where LEDs are used as photo-detectors for many applications and for another, they could be extended to generic photodetectors, thus providing useful information in photovoltaic field, for instance.
15
Content available remote Polarization of the longitudinal Pochhammer-Chree waves
EN
The exact solutions of the linear Pochhammer-Chree equation for propagating harmonicwaves in a cylindrical rod, are analyzed. Spectral analysis of the matrix dispersionequation for longitudinal axially symmetric modes is performed. Analytical expressionsfor displacement fields are obtained. Variation of wave polarization on the free surfacedue to variation of Poisson's ratio and circular frequency is analyzed. It is observed thatat the phase speed coinciding with the bulk shear wave speed all the components of thedisplacement eld vanish, meaning that no longitudinal axisymmetric Pochhammer-Chree wave can propagate at this phase speed.
PL
Azotowanie jarzeniowe tytanu i jego stopów jest jedną z obróbek powierzchniowych umożliwiających wytworzenie warstw o wysokich twardościach. Celem pracy było dokonanie analizy porównawczej składu jakościowego widma procesowego uzyskanego na tytanowym ekranie aktywnym, z widmem wzorcowym w rurkach spektralnych. Plazmę procesową tworzyły gazy Ar, N2, H2 wprowadzane w przestrzeń wylądowania jarzeniowego. Analizowano widmo spektralne w trzech etapach technologii azotowania jarzeniowego tytanu którymi były: przygotowanie komory próżniowej i oprzyrządowania do procesu, aktywacja powierzchni tytanu w wyładowaniu jarzeniowym, azotowanie jarzeniowe tytanu. Przedstawiono badania oceny wpływu temperatury azotowania jarzeniowego na zmianę sygnału spektralnego plazmy H2, N2, Ar oraz analizowano oddziaływanie zmiany proporcji reaktywnych gazów H2, N2 na sygnał spektralny plazmy. Badania te doprowadziły do próby zdefiniowania nowego parametru sterującego składem mieszanki gazowej wprowadzanej w obszar wyładowania jarzeniowego. Do realizacji celów pracy wykorzystano analizator spektralny plazmy oraz stanowisko badawcze — komorę próżniową pozwalającą naprowadzenie procesu azotowania jarzeniowego na potencjale katody, plazmy oraz potencjale uzupełniającym.
EN
The glow discharge nitriding of titanium and its alloys is one of the surface treatments enabling the formation of high hardness layers. The aim of the paper was to perform a comparative analysis of the qualitative composition of the process spectrum obtained on the titanium active screen with the reference spectrum in the spectral tubes. The process plasma was formed by the gases: Ar, N2 H2 introduced into the glow discharge space. The spectral spectrum was analyzed in three stages of the technology of glow discharge nitriding of titanium, which were: preparation of the vacuum chamber and process instrumentation, activation of the titanium surface in glow discharge, glow discharge nitriding of titanium. The paper presents the studies on the evaluation of the influence of the glow discharge nitriding temperature on the change in the plasma spectral signal H2,N2, Ar and analyzes the influence of the change in the proportions of reactive gases H2,N2 on the spectral signal of the plasma. These studies led to an attempt to define a new parameter controlling the composition of the gas mixture introduced into the glow discharge area. To achieve the goals of the paper, a plasma spectral analyzer and a test stand were used - a vacuum chamber allowing the glow discharge nitriding process to be carried out at the cathode, plasma and complementary potential.
EN
The article is devoted to the problem of voice signals recognition means introduction in the system of distance learning. The results of the conducted research determine the prospects of neural network means of phoneme recognition. It is also shown that the main difficulties of creation of the neural network model, intended for recognition of phonemes in the system of distance learning, are connected with the uncertain duration of a phoneme-like element. Due to this reason for recognition of phonemes, it is impossible to use the most effective type of neural network model on the basis of a multilayered perceptron, at which the number of input parameters is a fixed value. To mitigate this shortcoming, the procedure, allowing to transform the non-stationary digitized voice signal to the fixed quantity of mel-cepstral coefficients, which are the basis for calculation of input parameters of the neural network model, is developed. In contrast to the known ones, the possibility of linear scaling of phoneme-like elements is available in the procedure. The number of computer experiments confirmed expediency of the fact that the use of the offered coding procedure of input parameters provides the acceptable accuracy of neural network recognition of phonemes under near-natural conditions of the distance learning system. Moreover, the prospects of further research in the field of development of neural network means of phoneme recognition of a voice signal in the system of distance learning is connected with an increase in admissible noise level. Besides, the adaptation of the offered procedure to various natural languages, as well as to other applied tasks, for instance, a problem of biometric authentication in the banking sector, is also of great interest.
PL
Celem artykułu jest przedstawienie wyników analizy czasowo-częstotliwościowej sygnałów fonokardiograficznych. Powodem podjęcia działań dotyczących badania tego typu sygnałów są statystyki Światowej Organizacji Zdrowia, które od lat wskazują, iż pierwszą przyczyną zgonów na świecie są choroby układu sercowo-naczyniowego [1]. Powodem dominacji tego typu schorzeń w statystykach jest rosnący stres psychospołeczny oraz malejąca aktywność fizyczna społeczeństwa. Badanie tonów serca i detekcja schorzeń w oparciu o sygnał fonokardiograficzny na wczesnym etapie badań lekarskich może skutecznie przyczynić się do zmniejszenia wysokich statystyk umieralności. W artykule przedstawiono wyniki opracowanego algorytmu, który dla 15 osobowego zbioru przypadków charakteryzuje się czułością na poziomie 100% i specyficznością równą 87,50%, co z medycznego punktu widzenia jest wynikiem satysfakcjonującym.
EN
The aim of this article is to present the results of time-frequency analysis of phonocardiographic signals. The reason for undertaking such studies is the World Health Organization (WHO) statistics, which for years have shown that cardiovascular disease is the leading cause of death in the world [1]. The reason for the dominance of this type of illness in statistics is the increasing psychosocial stress and decreasing physical activity of the population. Heart rate and disease detection based on phonocardiographic data at an early stage of medical examination can effectively contribute to the reduction of high mortality statistics. The paper presents the results of the developed algorithm, which for the 15-person case collection is characterized by a sensitivity of 100% and a specificity of 87.50%, which is a satisfactory result from the medical point of view.
PL
Zakres zastosowań metody obserwacji magnetycznego szumu Barkhausena (BN) do nieniszczącego badania stanu lub właściwości materiałów magnetycznych stale rośnie. Z uwagi na stochastyczną naturę efektu Barkhausena niezbędne staje się użycie zaawansowanych metod analizy w celu ilościowej oceny obserwowanych zależności. Wiele czynników może wpływać na różne właściwości sygnałów BN wyrażanych w dziedzinie czasu i częstotliwości. Dlatego też obserwacja zmian dynamiki tego zjawiska wymaga analizy obu reprezentacji podczas procesu ekstrakcji cech. Z tego powodu korzystne staje się stosowanie metod transformacji czasowo-częstotliwościowych (tf) sygnałów. W tym artykule, w celu połączenia informacji dostarczonych w czasie i częstotliwości, zastosowano krótkoczasową transformatę Fouriera (ST FT). Przeprowadzono analizę uzyskanych reprezentacji tf sygnałów BN otrzymanych dla próbek stalowych o różnym stopniu zniszczenia i przedstawiono wyniki.
EN
The scope of applications of the magnetic Barkhausen noise observation (BN) method for non-destructive testing of the state or properties of magnetic materials is constantly increasing. Due to the stochastic nature of the Barkhausen effect, it is necessary to use advanced methods of analysis in order to quantify the observed relationships. Many factors can affect the various properties of BN signals expressed in the domain of time and frequency. Therefore, observation of changes in the dynamics of this phenomenon requires the analysis of both representations during the process of extraction of features. For this reason, it is preferable to use methods for transforming signals into time-frequency (tf) representation. In this article, a Short-Time Fourier Transform (ST FT) was used to combine information provided in time and frequency. The analysis of tf representations of BN signals obtained for steel samples representing various degrees of damage was performed and the results were presented.
EN
Azimuthally averaged power spectra are widely used in the Curie point depth (CPD) estimation with the implicit assumption that the magnetization distribution is random and uncorrelated. However, the marine magnetic anomalies are caused by bands of normal and reverse magnetization and show obvious trends. To investigate the effects of the anisotropy of marine magnetic anomalies on the CPD estimates, we develop 3D fractal striped magnetization models to produce lineated marine magnetic anomalies for the first time. We analyze the spectra anisotropy of the lineated magnetic anomalies of the synthetic fractal striped magnetization models and investigate its effects on the CPD estimates. The synthetic models and actual data show that the spectra of the lineated marine magnetic anomalies are directionally anisotropic. The amplitude response is strong and the slope of the logarithmic spectrum is large in a direction perpendicular to the stripes of magnetic anomalies, whereas the amplitude response is weak and the slope of the logarithmic spectrum is small in a direction parallel to the stripes of magnetic anomalies. The depth estimates in the perpendicular direction are close to the actual values, whereas the depths estimates in the parallel direction are significantly lower than the actual values. The actual marine magnetic anomalies of the South China Sea exhibit an anisotropic power spectrum that is consistent with the spectral anisotropy of magnetic anomalies of the synthetic fractal striped magnetization models.
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