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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.
2
Content available remote Diagnostics of transformer insulation by frequency domain spectroscopy
EN
The paper deals with the diagnostics of insulation oil-paper in high-voltage transformers by frequency diagnostic spectroscopy. The first part of paper deals with the base information about diagnostics of power transformers. In this part are presented differently insulating methods, for example method of recovery voltage method (RVM), method of polarization and depolarization currents (PDC) and chromatographic analysis. The second part of paper deals use of method of frequency domain spectroscopy (FDS) for high-voltage transformers with insulation oil-paper. This method is used in analysis insulating condition of power transformer with system of oil-paper. It was found, that the results of these tests are highly impacted by the operating temperature during the experimental measurement. Moisture and conductivity between insulating paper and oil in an insulating system are highly dependent from temperature. In the other part, the paper presents experimental results of the frequency diagnostic measurement for a real single-phase high-voltage transformer at different operating temperatures and states (with oil and without). Finally in the last part, the paper presents comparing frequency insulating measurements among several the same single-phase high-voltage transformers.
PL
W artykule przedstawiono metody diagnostyki izolacji olejowo-papierowej w transformatorach wysokiego napięcia. Zastosowano metodę spektroskopii częstotliwościowej. Wyniki analizy znacząco zależały od temperatury pracy. Porównano wyniki dla różnych warunków pracy kilku transformatorów.
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.
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.
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.
7
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.
PL
W pracy przedstawiono analizę widmową składowej promieniowania słonecznego odbitego od przeciwległej zabudowy i docierającego do elewacji budynku. Przeanalizowano dwie orientacje fasady, wschodnią i zachodnią, zlokalizowane w środowisku zurbanizowanym. Charakterystykę spektralną promieniowania wykonano dla promieniowania widzialnego oraz bliskiej podczerwieni. Obrazy cyfrowe wykonano z wykorzystaniem filtrów fotograficznych o znanej przepuszczalności promieniowania słonecznego. Analiza została przeprowadzona na podstawie pomiarów wykonanych od sierpnia do marca, dla wytypowanych dni charakteryzujących się nieboskłonem zachmurzonym lub bezchmurnym. Otrzymane wyniki pokazują istotną różnicę w udziale promieniowania o różnych długościach fali w całkowitym promieniowaniu docierającym do fasad, w zależności od warunków nieboskłonu, środowiska zewnętrznego i otaczającej zabudowy.
EN
The paper presents spectral analysis of solar radiation component reflected from opposite buildings and reaching the facades of the building. Two façade orientations were analyzed, eastern and western, located in the urban environment. Spectral characteristics of radiation were made for visible and near infrared radiation. Digital images were made using photographic filters with known solar transmittance. The analysis was based on measurements from August to March, for selected days with clear and overcast skies. The obtained results show a significant difference in the proportion of different wavelengths in the radiation reaching the façades depending on the conditions of the sky, the environment and the surrounding buildings.
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.
EN
Analysis of rainfall data from the island of Crete, Greece was performed to identify key hydrological years and return periods as well as to analyze the inter-annual behavior of the rainfall variability during the period 1981–2014. The rainfall spatial distribution was also examined in detail to identify vulnerable areas of the island. Data analysis using statistical tools and spectral analysis were applied to investigate and interpret the temporal course of the available rainfall data set. In addition, spatial analysis techniques were applied and compared to determine the rainfall spatial distribution on the island of Crete. The analysis presented that in contrast to Regional Climate Model estimations, rainfall rates have not decreased, while return periods vary depending on seasonality and geographic location. A small but statistical significant increasing trend was detected in the inter-annual rainfall variations as well as a significant rainfall cycle almost every 8 years. In addition, statistically significant correlation of the island’s rainfall variability with the North Atlantic Oscillation is identified for the examined period. On the other hand, regression kriging method combining surface elevation as secondary information improved the estimation of the annual rainfall spatial variability on the island of Crete by 70% compared to ordinary kriging. The rainfall spatial and temporal trends on the island of Crete have variable characteristics that depend on the geographical area and on the hydrological period.
13
Content available remote Wieloaspektowa analiza spektralna sygnałów fonokardiograficznych
PL
W artykule przedstawiono koncepcję analizy spektralnej sygnałów fonokardiograficznych. Zaprezentowano wyniki analizy sygnałów zawierających od kilku do kilkunastu uderzeń serca oraz sygnałów krótkich zawierających pojedyncze uderzenie serca. Przedstawiono propozycje kilkudziesięciu widmowych cech dystynktywnych oraz ocenę ich przydatności w diagnostyce schorzeń kardiologicznych.
EN
The article presents the idea of spectral analysis of phonocardiographic signals. The results of analysis of signals containing from several to over a dozen heartbeats and short signals containing only one heartbeat. Proposals dozens of spectral distinctive features and evaluate their usefulness in the diagnosis of cardiac diseases.
EN
The special features of taking into account the basic defects of brushed direct current machines influence on the vibration component of electromagnetic nature are scientifically substantiated. It is based on the use of the modern methods for magnetic field calculation. The efficiency of the use of the developed field model and the method for its parameters calculation in the analysis of the structural units typical breakages influence on the magnetic induction vector components distribution is confirmed. The dynamic eccentricity influence on the spectral distribution of forces of magnetic nature acting on the brushed direct current machine basic pole is analyzed. It enables identification of this defect in the future.
PL
Wzięcie pod uwagę wpływu efektów bazowych w szczotkowych silnikach prądu stałego na elektromagnetycznej natury składnik drgań jest naukowo uzasadniony. Opiera się to na użyciu nowoczesnych metod obliczania pola magnetycznego. Efektywność użycia rozwiniętego modelu polowego oraz metody obliczania parametrów w analizie uszkodzeń konstrukcyjnych wpływają na rozkład składowych wektora indukcji magnetycznej została potwierdzona. Przeanalizowano wpływ dynamicznej ekscentryczności na spektralny rozkład sił natury magnetycznej, działających na podstawowy biegun szczotkowej maszyny prądu stałego. Technika ta umożliwia identyfikację defektu w przyszłości.
EN
The properties of business cycles in Poland and its major trading partners have been examined. The business cycle synchronization (BCS) between Poland and other countries was studied in order to assess the impact of international trade on BCS. The author applies a modification of the Fourier analysis to the estimation of cycle amplitudes and frequencies. This allows more precise estimation of the cycle characteristics than the traditional approach. Cross-spectral analysis of the cyclical components of GDP for Poland and its major trading partners enables us to study the relationships between business cycles in these countries. Comparing the international structure of Polish trade with that of EU members with the cross-spectral characteristics of GDP series allows us to investigate the links between international trade and business cycle synchronization.
EN
This article deals with a method of how to acquire approximate displacement vibration functions. Input values are discrete, experimentally obtained mode shapes. A new improved approximation method based on the modal vibrations of the deck is derived using the least-squares method. An alternative approach to be employed in this paper is to approximate the displacement vibration function by a sum of sine functions whose periodicity is determined by spectral analysis adapted for non-uniformly sampled data and where the parameters of scale and phase are estimated as usual by the least-squares method. Moreover, this periodic component is supplemented by a cubic regression spline (fitted on its residuals) that captures individual displacements between piers. The statistical evaluation of the stiffness parameter is performed using more vertical modes obtained from experimental results. The previous method (Sokol and Flesch, 2005), which was derived for near the pier areas, has been enhanced to the whole length of the bridge. The experimental data describing the mode shapes are not appropriate for direct use. Especially the higher derivatives calculated from these data are very sensitive to data precision.
PL
W referacie przedstawiono sposoby uwzględniania odpowiedzi modalnej konstrukcji na działanie wstrząsów sejsmicznych posługując się spektralną analizą modalną. Omówiono metodę spektrum odpowiedzi uwzględniając najważniejsze zalecenia dotyczące jej stosowania. Opisano najczęściej stosowaną metodę sumowania odpowiedzi modalnej – CQC oraz jej modyfikacje – metody CQC3 i GCQC3, które pozwalają uwzględnienie kierunków działania wstrząsu. Odniesiono się również do przepisów zawartych w normie Eurocode 8 dotyczących wytycznych sumowania odpowiedzi z różnych kierunków. Na przykładach numerycznych dokonano porównania zaprezentowanych metod z użyciem spektralnej analizy modalnej oraz obliczono odpowiedź wybranych sił przekrojowych.
EN
The paper presents calculation methods of modal response during the earthquake motions and some remarks of dynamic and spectral analysis. The most often methods used to combine effects of natural vibration modes and earthquake directions are considered. Authors presented well known Complete Quadratic Combination (CQC) and its newest modifications CQC3 for planar variability and General Complete Quadratic Combination (GCQC3) for spatial variability of earthquake directions. All calculation approaches are supported with two examples of steel frame structures submitted to earthquake effects according to Eurocode 8.
EN
Optimization of the fuel combustion process in a self-ignition engine with the multi-stage HPCR injection system sets the main trends in research on the thermodynamic stability of fuels, and the mechanisms of PM formation. The stages were indicated of the multifaceted diagnostic inference on the causes of failures of a turbocharger with variable geometry (VTG) which occur as a result of PM sedimentation in the nozzle area. An evaluation of the engine performance was conducted using a dedicated tester and an additional recording of the injector coil current characteristics with parallel readings of the fuel pressure variation in the reservoir. The indicated procedure established the underlying cause of the VTG compressor failure despite the absence of a recorded error code.
EN
Spectral analysis for global navigation satellite system (GNSS) coordinate time series provides a principal tool to understand the intrinsic mechanism that affects tectonic movements. Spectral analysis methods such as the fast Fourier transform, Lomb–Scargle spectrum, evolutionary power spectrum, wavelet power spectrum, etc. are used to find periodic characteristics in time series. Among spectral analysis methods, the chirp Fourier transform (CFT) with less stringent requirements is tested with synthetic and actual GNSS coordinate time series, which proves the accuracy and efficiency of the method. With the length of series only limited to even numbers, CFT provides a convenient tool for windowed spectral analysis. The results of ideal synthetic data prove CFT accurate and efficient, while the results of actual data show that CFT is usable to derive periodic information from GNSS coordinate time series.
EN
Prevention and early diagnosis of imminent preterm labor are considered to be the most important perinatal challenge nowadays. Significant progress has been observed on postnatal care of premature infants, but without reducing the prevalence of preterm delivery. Our study was focused on comparison of three methods of spectral analysis of electro-hysterographic (EHG) signals: fast Fourier transform (FFT), wavelet transform (WT) and autoregressive modeling (AR). Complexity of the electrohysterographic signals was analyzed by using: the approximate entropy (ApEn), Lempel–Ziv complexity measure (L–Z). Additionally, the work evaluated the applicability of EHG in diagnosing imminent premature labor. EHG signals were recorded among 60 patients with threatened preterm labor symptoms between the 24th and 34th week of pregnancy. Patients included to the study had a shortened cervix (less than 20 mm) without regular uterine contractions recorded on regular cardiotocography (CTG). The women were divided into two groups: those delivering within 7 days – group A (n = 15) and women delivering after 7 days – group B (n = 45). The study confirmed differences in bioelectrical activity of uterus between patients delivering prematurely within 7 days and after from the EHG registration for all analyzed methods.
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