Wyniki wyszukiwania - BazTech

1

Condition diagnostics of marine centrifugal pumps based on blade-passing frequency harmonics with analytical DFT leakage compensation

Varbanets Roman, Kyrnats Vladyslav, Kholdenko Volodymyr, Minchev Dmytro, Bilousov Ievgen, Maulevych Vladyslav, Kucherenko Volodymyr, Aleksandrovska Nadiia

Polish Maritime Research

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2026

|

nr 2

122--133

EN

The reliable operation of high-power marine centrifugal pumps is critical for the safety and efficiency of ballast and fire-fighting systems, as well as for the functioning of a wide range of power and auxiliary installations on large ocean-going vessels. This paper presents a vibrodiagnostic method for the condition monitoring of a vertical in-line marine centrifugal pump manufactured by DESMI, based on the frequency-domain analysis of vibration signals measured in the impeller zone. The paper focuses on the study of discrete amplitude spectra obtained under steadystate operating conditions at a rotational speed close to 900 rpm. Particular attention is paid to the distortion of diagnostic features caused by spectral leakage of the fundamental rotational harmonic, which significantly affects the identification of key diagnostic parameters. An analytical procedure for compensating the power leakage of the central harmonic is proposed, enabling accurate reconstruction of the true spectral energy distribution without increasing the measurement record length or applying complex windowing techniques. The proposed approach improves the resolution and interpretability of vibration spectra within the operating frequency range of the pump. The method enhances the reliability of vibration-based condition monitoring for marine centrifugal pumps operating under real shipboard conditions and can be implemented in existing condition-based maintenance systems without additional hardware modification. Moreover, a procedure for a continuous vibration monitoring system for a high-power centrifugal pump, suitable for integration into modern controllers with FFT functionality, is developed. The results demonstrate that the proposed analytical compensation of spectral leakage is an effective tool for improving the vibrodiagnostic reliability of high-power shipboard pumps and supports the early detection of hydraulic and mechanical degradation in critical auxiliary marine machinery.

2

Experimental results of inverter faults impact on the performances of SPWM and SVPWM control techniques

Horri Noureddine, Boudinar Ahmed Hamida, Aimer Ameur Fethi, Khodja Mohamed Amine

Przegląd Elektrotechniczny

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2025

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R. 101, nr 9

117--126

EN

Induction motors are widely used in industry due to the development of electronic power switch technology used in variable speed drives and controls. Indeed, several control strategies have been developed to control the speed of these motors such as sinusoidal PWM control and space vector PWM control techniques. Several studies have shown that space vector PWM control is more efficient than sinusoidal PWM technique based on the low THD obtained. However, this advantage can be affected by the failure of electronic switches such as IGBTs. In this paper, a time and spectral analysis are applied on experimental signals in order to investigate the impact of the IGBT open circuit (OC) fault on the performance of these control strategies.

PL

Silniki indukcyjne są szeroko stosowane w przemyśle ze względu na rozwój technologii elektronicznego przełącznika mocy stosowanej w napędach o zmiennej prędkości i układach sterowania. Rzeczywiście, opracowano kilka strategii sterowania w celu kontrolowania prędkości tych silników, takich jak sinusoidalne sterowanie PWM i techniki sterowania PWM wektorem przestrzennym. Kilka badań wykazało, że sterowanie PWM wektorem przestrzennym jest bardziej wydajne niż technika sinusoidalnego PWM w oparciu o uzyskane niskie THD (Total Harmonic Distortion, Współczynnik Zawartości Harmonicznych). Jednak ta zaleta może zostać naruszona przez awarię przełączników elektronicznych, takich jak IGBT. W niniejszym artykule, zastosowano analizę czasową i widmową sygnałów eksperymentalnych w celu zbadania wpływu awarii obwodu otwartego IGBT (OC) na wydajność tych strategii sterowania.

3

Basic magnetization curve fitting function based on spectral analysis

Xu Gang, Wang Shiwei, Zhang Long, Wu Long

Polimery

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2025

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Vol. 70, nr 2

103--112

EN

The current fitting function of the basic magnetization curve does not provide the exact fit necessary for the simulation modeling of electromechanical devices containing conductive materials, including polymers. Therefore, an odd polynomial fitting function based on the spectral analysis of the fitting results of the basic magnetization curve under sinusoidal excitation is proposed, and the effect of the odd polynomial fitting is studied by comparative analysis. The results show that the odd polynomial provides a better fit and has a simple expression, and the method of obtaining the fitting function based on the spectral analysis provides a new idea for the selection of the basic magnetization curve fitting function.

PL

Obecna funkcja dopasowania podstawowej krzywej namagnesowania nie zapewnia dokładnego dopasowania niezbędnego do modelowania symulacyjnego urządzeń elektromechanicznych zawierających materiały przewodzące, w tym polimery. Dlatego zaproponowano funkcję dopasowania wielomianu nieparzystego opartą na analizie widmowej wyników dopasowania podstawowej krzywej namagnesowania przy wzbudzeniu sinusoidalnym, a wpływ dopasowania wielomianu nieparzystego zbadano za pomocą analizy porównawczej. Wyniki pokazują, że wielomian nieparzysty zapewnia lepsze dopasowanie i ma proste wyrażenie, a metoda uzyskiwania funkcji dopasowania oparta na analizie widmowej dostarcza nowego pomysłu na wybór funkcji dopasowania podstawowej krzywej namagnesowania.

4

Integration of artificial intelligence into industrial cooling and water purification systems

Agayev Farid H., Mehdiyeva Almaz M., Aghamatov Stanislav E.

Nafta-Gaz

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2025

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R. 81, nr 4

280--288

EN

This paper explores advanced methods for integrating artificial intelligence into industrial systems specifically designed for water purification within cooling processes. By utilizing data collected from a wide range of sensors and spectral analyzers, we developed an intelligent system powered by neural networks. This system is capable of accurately identifying the presence of petroleum products in water and predicting potential contamination with a high degree of precision. The system was subjected to rigorous testing and optimization through the application of machine learning techniques, which significantly enhanced its ability to monitor water quality in real time. Furthermore, these optimizations improved the system’s overall efficiency in detecting and preventing leaks, thereby playing a critical role in safeguarding industrial processes from potential disruptions. The results of extensive testing show that the proposed AI-driven approach is highly accurate and reliable, demonstrating its practical viability for deployment in real-world industrial settings. These findings underscore the value of integrating such advanced systems into existing industrial infrastructures, as they not only improve operational efficiency but also contribute to enhanced environmental protection and safety measures. As industries continue to face increasing challenges related to water quality and environmental compliance, the implementation of intelligent AI systems like the one proposed in this paper may prove invaluable. Their ability to optimize both performance and safety makes them an essential tool in modern industrial environments, ensuring that both productivity and sustainability are successfully achieved. The performance of the proposed model confirms its readiness for integration into real spectral analysis workflows, where accuracy and reliability are of paramount importance.

PL

W artykule zbadano zaawansowane metody integracji sztucznej inteligencji z systemami przemysłowymi zaprojektowanymi specjalnie do oczyszczania wody w procesach chłodzenia. Wykorzystując dane zebrane z różnorakich czujników i analizatorów spektralnych, opracowano inteligentny system oparty na sieciach neuronowych. System ten jest w stanie precyzyjnie identyfikować obecność produktów ropopochodnych w wodzie oraz przewidywać potencjalne zanieczyszczenia z wysokim poziomem dokładności. System został poddany rygorystycznym testom i optymalizacji poprzez zastosowanie technik uczenia maszynowego, co znacznie zwiększyło jego zdolność do monitorowania jakości wody w czasie rzeczywistym. Ponadto wprowadzone usprawnienia zwiększyły ogólną skuteczność systemu w wykrywaniu wycieków i zapobieganiu im, przez co odgrywają one kluczową rolę w ochronie procesów przemysłowych przed potencjalnymi zakłóceniami. Wyniki szeroko zakrojonych testów wykazały, że proponowane podejście oparte na sztucznej inteligencji jest bardzo dokładne i niezawodne, co dowodzi jego praktycznej przydatności do wdrożenia w rzeczywistych warunkach przemysłowych. Uzyskane wyniki podkreślają wartość integracji zaawansowanych systemów tego typu z istniejącą infrastrukturą przemysłową, ponieważ nie tylko zwiększają one wydajność operacyjną, ale także przyczyniają się do poprawy ochrony środowiska i środków bezpieczeństwa. W obliczu rosnących wyzwań związanych z jakością wody i przestrzegania norm środowiskowych, wdrażanie inteligentnych systemów AI, takich jak ten przedstawiony w niniejszej publikacji, może okazać się niezwykle cenne. Ich zdolność do optymalizacji zarówno wydajności, jak i bezpieczeństwa czyni je nieodzownym narzędziem we współczesnym przemyśle, zapewniając równoczesną realizację celów produktywności i zrównoważonego rozwoju. Wydajność proponowanego modelu potwierdza jego gotowość do integracji z rzeczywistymi przepływami pracy analizy spektralnej, gdzie dokładność i niezawodność są kluczowymi czynnikami.

5

Estimation of Curie-point depth, heat flow and geothermal gradients in Shelleng area and environs, northeastern Nigeria from aeromagnetic data

Yassah Hassan Nelson, Onuoha Kalu Mosto, Mode Ayonma Wilfred, Ezekiel Kamureyina, Okoro Eze Martins

Acta Geophysica

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2025

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Vol. 73, no. 1

203--220

EN

Regional estimation of Curie-point depth (CPD), subsurface heat flow and geothermal gradients variations in the Shelleng area and environs of northeastern Nigeria was carried out in this study using spectral analysis of high-resolution aeromagnetic (HRAM) data. The HRAM data were divided into nine (9) overlapping blocks and each of the blocks was analyzed to obtain the 2D radially averaged power spectrum which enabled the computation of depths to the top and centroid of magnetic sources. The obtained values were then used to determine the depth to the bottom of magnetic bodies or the CPD, geothermal gradients and crustal heat flow changes in the study area. Results showed that CPD varies from 7.56 ± 0.122 to 18.01 ± 0.324 km, with an average of 11.72 ± 0.166 km; geothermal gradient values vary between 32.20 and 76.72 °C/ km, with an average of 52.76 °C/km, while heat flow variations range from 80.51 to 191.80 mW/m2, with an average of 131.85 mW/m2. Shallow CPD zones identified in the northeastern, western and southwestern portions of the study area correspond to zones of high geothermal gradient values and high subsurface heat flow distributions. These areas signify zones associated with anomalous subsurface thermal conditions and were therefore recommended for further detailed geothermal energy exploration studies.

6

Identification of railway track damage using vibration signal characteristics

Łomżyńska Adrianna, Strugarek Klaudia, Nowak Malwina, Ludwiczak Aleksander, Klekowicki Mikołaj, Szymański Grzegorz M.

Pojazdy Szynowe

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2024

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Nr 3-4

64--72

EN

The study focuses on the identification of railway track damage using vibration signal characteristics. It presents the identification of vibration signals generated by the bogie system during passage over selected track sections in two different technical conditions. A literature review on rail infrastructure and its maintenance is provided, along with a description of modern diagnostic systems employed by companies responsible for track maintenance. The research involved analyzing vibration signals in both the time and frequency domains. Based on the obtained results, the feasibility of detecting damage using vibration signals recorded from a vehicle was confirmed, allowing for the assessment of the impact of infrastructure damage on passenger comfort.

7

Mapping of morphological coastline changes based on aerial photographs and Discrete Fourier Transform, Hel Peninsula, Poland

Stachurska Barbara

Oceanologia

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2024

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No. 66 (3)

art. no. 66301

EN

The coast is a dynamic zone where constantly occurring hydrodynamic and morphodynamic processes affect the shape of the shore. The paper presents a method based on spatial and spectral analysis of changes in the coastline position based on data obtained from aerial photographs interpretation and Fourier analysis, on the example of the Hel Peninsula. The Hel Peninsula is one of the most interesting accumulation forms of the Polish Baltic coast, where dynamic changes of the seashore cause the occurrence of time-varying sections of accumulation-abrasion of the coastline. For the purpose of detecting the coastline changes, historical aerial photographs from the years 1947, 1957, 1963, 1991 were used. It was assumed that the over-40-year research period, which includes the obtained series of aerial photographs, would allow for a sufficient study of the long-term shoreline changes, which allow for distinguishing the length of characteristic coastline undulations. The quasi-wave signal of the shoreline changes obtained from the aerial photographs interpretation, after using Fourier analysis, enabled an effective and precise identification of the coastline undulation. The spatial analyses, showed that the Hel Peninsula is clearly divided into a part subjected to accumulation processes and an abraded one. Furthermore, the dynamics of coastline changes was determined, showing that the abrasive processes were intensifying. Moreover, spectral Fourier analysis allowed for the precise identification of coastline undulations with dominant lengths. The obtained results of spatial and spectral analysis indicate that abrasive-accumulation sections with a length of about 0.3–4.5 km dominate on the Hel Peninsula shoreline.

8

Spectral analysis in assessment of multispot projection welding

Karpiński Maciej, Kustroń Paweł, Pikuła Janusz, Jopek Wojciech, Mikno Zygmunt

Materials Science and Welding Technologies / Technologie Materiałowe i Spawalnicze

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2024

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Vol. 68, No. 2

art. no. 4

EN

The article presents the possibility of an innovative use of spectral analysis to control the quality of joints welded using the multispot projection welding method. The tests discussed in the article included the analysis of welding machine and welding fixtures frequency. The analysis consisted in the impulse-based excitation of vibrations in the entire system (including the welding machine and elements subjected to welding) and the recording of the object response using an acceleration sensor. The results were afterwards subjected to spectral analysis using the Fourier transform. As a result, it was possible to identify the effect of the lack of a weld on the free vibration frequencies of the entire system. Related quality control was performed by comparing the free vibration frequency spectrum of reference elements with that of elements not containing a metallic joint between them. The acquisition and analysis of measurement data were carried out in the LabView environment. The test results confirmed the possibility of using spectral analysis to control the quality of the projection welding process.

PL

W artykule przedstawiono możliwość nowatorskiego zastosowania analizy widmowej do kontroli jakości złączy zgrzewanych metodą garbową wielopunktową. Przeprowadzone badania obejmowały analizę częstotliwości drgań własnych zgrzewarki wraz z przyrządem zgrzewalniczym, w którym były zamocowane elementy zgrzewane. Analiza polegała na wzbudzeniu drgań całego układu, obejmującego przyrząd zgrzewalniczy oraz elementy zgrzewane, przez impulsowe wymuszenie oraz rejestrację odpowiedzi obiektu za pomocą czujnika przyspieszenia. Wyniki zostały następnie poddane analizie widmowej z zastosowaniem transformaty Fouriera, co pozwoliło wyznaczyć wpływ braku zgrzeiny na częstotliwości drgań własnych całego układu. Kontrolę jakości zrealizowano przez porównanie spektrum częstotliwości drgań własnych dla detali wzorcowych z detalami, w których nie wystąpiło połączenie metaliczne pomiędzy komponentami. Akwizycję oraz analizę danych pomiarowych prowadzono w środowisku LabView. Uzyskane wyniki badań potwierdziły możliwość zastosowania analizy widmowej do przeprowadzenia kontroli jakości procesu zgrzewania garbowego.

9

Spectral Analysis of MRI Sound Signal

Arawade Swapnil, Piechowicz Janusz

International Journal of Electronics and Telecommunications

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2024

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Vol. 70, No. 4

839-847

EN

Magnetic Resonance Imaging (MRI) is a very versatile diagnostic tool for non-invasive analysis of human organ functions, without use of ionizing radiations. Loud operating sound is the major challenge associated with the MRI technology, reaching up to 130dB. This paper analyses and compares the spectral properties of acoustic noise produced in the examination room of the mobile imaging trailer based 1.5 Tesla MRI system, during different scanning sequences of image acquisition. The analysis is useful in understanding the dynamic behavior of the sound generated inside the examination room to develop the noise reduction strategy.

10

Exact controllability for nonlinear thermoviscoelastic plate problem

Moulahi Taoufik, Aouadi Moncef, Althobaiti Saad

Demonstratio Mathematica

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2024

|

Vol. 57, nr 1

art. no. 20240071

EN

In this article, we consider a problem of exact controllability in the processes described by a nonlinear damped thermoviscoelastic plate. First, we prove the global well-posedness result for the nonlinear functions that are continuous with respect to time and globally Lipschitz with respect to space variable. Next, we perform a spectral analysis of the linear and uncontrolled problem. Then, we prove that the corresponding solutions decay exponentially to zero at a rate determined explicitly by the physical constants. Finally, we prove the exact controllability of the linear and the nonlinear problems by proving that the corresponding controllability mappings are surjective.

11

Verification of the AIS service availability model based on dynamic data streams recorded from three receiving stations in the Polish coastal area

Jaskólski Krzysztof, Czapliński Wojciech

Archives of Transport

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2024

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Vol. 70, iss. 2

159--180

EN

The reliability aspects of the operation of radio navigation systems constitute a crucial element for the safety of maritime navigation.. Technological progress in ship traffic monitoring is achieved through the design of ship systems and shore infrastructure equipped with Automatic Identification System (AIS) devices. One of the issues with AIS operation is the limited availability of the service in the form of data streams with an extended data age recorded on the receiving side. Another problem is the emission and reception by ships of incomplete positional reports without navigational parameters. Such situations render the system operationally unfit in terms of processed information. Therefore, it is essential to investigate the operational characteristics of radio navigation systems and develop tools to monitor the AIS service status on the receiving side. This article presents the development of a model for the availability of an AIS for vessels based on the determined mean time of the occurrence of incomplete navigation parameter values in AIS messages and the results of research in the domain of time and frequency using a mathematical method of the Fast Fourier Transform (FFT). The study results refer to six basic navigation parameters and show a varying service availability factor for the navigation parameters under study, i.e. the latitude (LAT), longitude (LON), speed over ground (SOG), course over ground (COG), heading (HDT), and the rate of turn (ROT). The data recorded by three receiving AIS stations on the Polish coast, i.e. PLKOL, PLSZZ, and PLSWI, were used as a key source of practical knowledge on the limitations of the AIS service availability. The experiment observed interruptions in the regular transmission of data from navigation equipment in the AIS service operational zone. As a result, the functional relationship was described based on the spectral analysis of the frequency of occurrence of times between the service repair (Time To Repair, TTR), and the model was proposed to be applied to the study of other variables. The presented model is a tool that allows for improving the monitoring of vessel traffic in terms of reliability, which directly affects the improvement of maritime traffic safety.

12

Algorithms for time-frequency imaging and analysis: introduction to mixed-model spectral decomposition

Pant Animesh, Ghosal Dibakar, Puryear Charles, Verma Shashank Narayan

Acta Geophysica

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2024

|

Vol. 72, no. 2

637--653

EN

Time-frequency algorithms help discern and filter hidden information from signals but their growing abundance induces non-uniqueness thus, complicating selection. Classification of these algorithms into approaches can bring simplification and structure to improve our selection and estimates. This study focuses on algorithms we classify here as fixed windowbased projection approach, wavelet-based projection approach, greedy-based approach and combinational-based approach while omitting heuristic-based approach and numerical-autoregressive-based approach classes. It describes the basic theory of transforms under the classes and compares them for effective stability, effective localization and resolution capabilities of time-frequency spectra for wavelet estimation and interfering beds with results demonstrating subtle advantages for each depending on nature of signal and model behind the algorithm. The combinational-based mixed-model approach wavelet-assisted constrained least squares spectral analysis concatenates a wavelet-based approach with a fixed windowbased approach and effectively functions to reassign complex amplitude coefficients from their apparent positions to their true positions. A comparison of the results suggests that it demonstrates good scope as an effective alternative general tool for hydrocarbon detection and resolution of thin beds.

13

Dwuwymiarowa analiza korelacyjna

Czarnecki Mirosław Antoni

Wiadomości Chemiczne

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2023

|

[Z] 77, 7-8

775--800

EN

This review provides fundamental information on theoretical and practical aspects of two-dimensional correlation spectroscopy (2DCOS). At first, is shown a brief development of this method since its introduction by Isao Noda in 1986. In the next part is explained the general idea of 2DCOS, and details of determination of the synchronous and asynchronous spectra from the experimental data. Next section includes comprehensive description of the properties and the rules for interpretation of the 2D correlation spectra. The most common problems with interpretation of 2DCOS spectra, and the ways of improving results of correlation analysis by a proper data pre-treatment are widely discussed. In addition, some of the most important modifications of this method like moving-window analysis and PCMW2D are described. Finally, the usefulness of the power spectra is presented. It has been shown that 2D correlation analysis is a versatile and powerful tool for data analysis and provides information not readily accessible from the original data set.

14

Diagnosis of ITSC fault in the electrical vehicle powertrain system through signal processing analysis

Ouamara Dehbia, Boukhnifer Moussa, Chaibet Ahmed, Maidi Ahmed

Diagnostyka

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2023

|

Vol. 24, No. 1

art. no. 2023113

EN

The three-phase induction motor is well suited for a wide range of mobile drives, specifically for electric vehicle powertrain. During the entire life cycle of the electric motor, some types of failures can occur, with stator winding failure being the most common. The impact of this failure must be considered from the incipient as it can affect the performance of the motor, especially for electrically powered vehicle application. In this paper, the intern turn short circuit of the stator winding was studied using Fast Fourier transform (FFT) and Shor-Time Fourier transform (STFT) approaches. The residuals current between the estimated currents provided by the extended Kalman filter (EKF) and the actual ones are used for fault diagnosis and identification. Through FFT, the residual spectrum is sensitive to faults and gives the extraction of inter-turn short circuit (ITSC) related frequencies in the phase winding. In addition, the FFT is used to obtain information about when and where the ITSC appears in the phase winding. Indeed, the results allow to know the faulty phase, to estimate the fault rate and the fault occurrence frequency as well as their appearance time.

15

Characteristic Features of Structure and Analysis of Friction Behavior of Electric-Spark Coatings from Powder Wires

Holubets Volodymyr, Pashechko Mykhaylo, Borc Jarosław, Shpuliar Yuriy, Hasiy Oleksandr, Honchar Ivan

Advances in Science and Technology. Research Journal

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2023

|

Vol. 17, no. 2

299--306

EN

The structure, phase and chemical composition of electric-spark coatings (ESC) obtained on the Elitron installation from powder electrode wires were investigated using a Neophot-2 optical computer microscope, an EVO-40XVP (Carl Zeiss) scanning electron microscope, DRON-3.0 X-ray diffractometer, EXPERT 02L elemental composition analyzer. The structure of the ESC is an austenitic matrix with boride inclusions (Fe,Cr)B, iron boride Fe2B, chromium borides of iron Cr1.65Fe0.35B0.96. The distribution of Cr, Fe and C in these coatings is uneven and varies in wide range. The micromechanical characteristics of the modified surface layer of steel 45 were analyzed using Ultra Nano Hardness Tester and Nan Scratch Tester. The article provides an analysis of the frictional behavior of the ESC under conditions of dry friction and boundary lubrication according to the finger-disc scheme. Frictional stability of such coatings indicates the expediency of using electric-spark alloying (ESA) technology with powder wires (PW) and powder wires with graphite (PWG) to increase the service life of both machine parts and cutting tools.

16

Comparison of calculating algorithms for logarithmic decrements applied to welded joints assessments

Szeleziński Adam, Muc Adam, Murawski Lech, Muchowski Tomasz, Kluczyk Marcin, Jasiński Krzysztof, Antczak-Jarząbska Romana

Scientific Journal of Gdynia Maritime University

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2022

|

nr 124

7--19

EN

There are numerous non-destructive methods in welded joints investigation, but the most promising, especially in applications with steady monitoring of the structure, is the vibro-diagnostic approach. In the course of the research work, the responses were obtained and detected by accelerometers, providing valuable diagnostic information, which later was mathematically processed in the field of time or frequency. The mathematical processing aimed to distinguish significant characteristics embedded in the processes typical of the investigated joints and allow an assessment of how they were made. For this purpose, two methods were proposed, based on determining the logarithmic decrement as a function of time. Due to the complicated course of the impact responses, the method of calculating the logarithmic decrement has been suggested, involving the approximation of responses with various functions. According to the research, the analysis of changes in the logarithmic decrement as a function of time applied to welded plates was proposed, as it enables the initial assessment of joint quality.

17

The d-bar formalism for the modified Veselov-Novikov equation on the half-plane

Hwang Guenbo, Moon Byungsoo

Opuscula Mathematica

|

2022

|

Vol. 42, no. 2

179--217

EN

We study the modified Veselov–Novikov equation (mVN) posed on the half-plane via the Fokas method, considered as an extension of the inverse scattering transform for boundary value problems. The mVN equation is one of the most natural (2+1)-dimensional generalization of the (1+1)-dimensional modified Korteweg-de Vries equation in the sense as to how the Novikov–Veselov equation is related to the Korteweg–de Vries equation. In this paper, by means of the Fokas method, we present the so-called global relation for the mVN equation, which is an algebraic equation coupled with the spectral functions, and the d-bar formalism, also known as Pompieu’s formula. In addition, we characterize the d-bar derivatives and the relevant jumps across certain domains of the complex plane in terms of the spectral functions.

18

Bedforms evolution in the Vistula River mouth during extreme flood event, southern Baltic Sea

Lisimenka Aliaksandr, Kubicki Adam, Kałas Maciej

Oceanologia

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2022

|

No. 64 (1)

212--226

EN

Results of bathymetric surveys conducted to examine changes of sand dunes geometry in the Vistula River mouth before, during and after the extreme flood event are presented. A total of 2076 dunes were analysed based on a series of bed elevation profiles obtained along the centreline of about 3.3 km length. Low-steepness dunes characterized by the mean lee-side slopes milder than β<10° are fully dominant at low flows. In contrast, at high hydrology, nearly 50% of dunes indicate β>10°. Dune height and length are substantially out of phase with progressive changes of water discharge exposing a well-pronounced anti-clockwise hysteresis. Distinct behaviour of dune dimensions reflected in increasing of dune steepness H/λ of about 3-fold and decreasing of about 4-fold were observed during rising and falling discharges, respectively. The bed roughness due to dunes presence showed changes of about 10-fold during the both of limbs and is found to be in range of about kdunes=(1/5÷3/5)Hmean. At the mesoscale region, spectra followed sufficiently by the ‘–3 power law’ for low hydrology, with steeper spectrum slopes close to ‘–4’ during moderate and high water discharges. With the development of the flood, potential of flow separation phenomena was increased of about 9-fold, from 2.2% at the flood beginning phase up to 20% at the flood peak. The obtained results could be used for the improvement of the hydraulic numerical models in sand-bed rivers to predict bedforms evolution, flow resistance and turbulence as well as water levels for proper river system management during flood events.

19

System diagnostyczny do bezinwazyjnej oceny stanu klatki wirnika silników indukcyjnych

Sułowicz Maciej, Duda Arkadiusz, Zielonka Jakub, Tulicki Jarosław, Cholewa Dariusz, Czechowski Mirosław

Maszyny Elektryczne : zeszyty problemowe

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2022

|

Nr 1 (127)

229--236

PL

Ocena stanu klatki silników indukcyjnych jest ciągle aktualnym problemem diagnostyki stanu tych maszyn. Na rynku zasadniczo nie ma urządzeń, które mogły by w sposób kompleksowy automatycznie diagnozować uszkodzenia klatek silników zarówno podczas stanu ustalonego w oparciu o metodę MCSA jak i podczas rozruchu wykorzystując analizę przetworzonego przebiegu prądu rozruchowego. Na podstawie wieloletnich doświadczeń, autorów artykułu, w prowadzeniu badań stanu klatek wirnika dla wielu maszyn w różnych gałęziach przemysłu, opracowano urządzenie pomiarowe i specjalistyczne oprogramowanie pozwalające diagnozować rożne typy silników indukcyjnych klatkowych podczas rozruchu jak i stanu ustalonego. W artykule przedstawiono sposób pomiaru sygnału diagnostycznego, którym jest prąd stojan. Odwołano się do wiarygodności pomiarów diagnostycznych. Przedstawiono funkcjonalność oprogramowania do pomiarów diagnostycznych i analiz podczas stanu ustalonego i rozruchu. Przedstawiono wyniki wybranych pomiarów diagnostycznych, formy prezentacji wyników oceny stanu oraz przedstawiono przykłady zastosowania opracowanego systemu w badaniach przemysłowych w różnych gałęziach przemysłu.

EN

The assessment of the cage condition of induction motors is still a current problem in diagnosing the condition of these machines. There are basically no devices on the market that could comprehensively and automatically diagnose damage to motor frames, both during the steady state based on the MCSA method and during start-up using the analysis of the processed inrush current waveform. Based on many years of experience of the authors of the article, in conducting research on the condition of rotor cages for many machines in various industries, a measuring device and specialized software were developed to diagnose various types of squirrelcage induction motors during start-up and in the steady state. The article presents the method of measuring the diagnostic signal, which is the stator current. The reliability of the diagnostic measurements was referred to. The functionality of the software for diagnostic measurements and analyzes during steady state and start-up is presented. The results of selected diagnostic measurements, forms of presentation of the results of condition assessment and examples of the application of the developed system in industrial research in various branches of industry are presented.

20

The Influence of a Low-Frequency Musical Fragment on the Neural Oscillations

Drozdenko Kateryna, Naida Sergey, Drozdenko Oleksandr, Damarad Anastasiia, Pareniuk Dmytro, Vakulenko Liudmyla, Adaricheva Zhanna

Archives of Acoustics

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2022

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Vol. 47, No. 2

169--179

EN

Study of musical-acoustic influences, which are used to improve the functional state of a person, as well as her/his neurophysiological or psychological rehabilitation, is very relevant nowadays. It is related with a large number of conflict situations, significant psychological and informational overloads of modern human, permanent stress due to the pandemic, economic crisis, natural and man-made disasters. This work examines the effect of listening to low-frequency music on the percentage of alpha, beta, delta, and theta waves in the total spectral power of the electroencephalogram in the frequency band 0.5–30 Hz. To obtain rhythms of the brain the spectral analysis of filtered native electroencephalogram was used. For statistical analysis of neural oscillations the Student’s t-test and the sign test were implemented with usage of the Lilliefors normality criterion and the Shapiro-Wilk test. Statistically significant differences were identified in alpha, theta and delta oscillations. For the beta rhythm presented music did not play any significant role. An increase in the activity of the alpha rhythm in the temporal (for 2.20 percentage point), central (for 1.51 percentage point), parietal (for 2.70 percentage point), occipital (for 2.22 percentage point) leads of the right hemisphere and the parietal (for 1.74 percentage point) and occipital (for 2.46 percentage point) leads of the left hemisphere and also of the theta rhythm in the temporal leads of the left hemisphere (for 1.13 percentage point) were observed. The downfall of delta rhythm in the frontal lead of the left hemisphere (for 1.51 percentage point) and occipital in both hemispheres (for 1.64 and 1.33 percentage points respectively in the left and right hemispheres) was detected. These may indicate that listening to low-frequency compositions helps to restore the brain in physiological conditions at different functional overload levels, decrease the level of emotional tone, and promote relaxation.