Wyniki wyszukiwania - BazTech

1

Dwuwymiarowa analiza korelacyjna

Czarnecki Mirosław Antoni

Wiadomości Chemiczne

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2023

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[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.

2

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

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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.

3

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

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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.

4

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

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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.

5

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

Hwang Guenbo, Moon Byungsoo

Opuscula Mathematica

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2022

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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.

6

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

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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.

7

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

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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.

8

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.

9

Analysis of the backlash in the single stage cycloidal gearbox

Król Roman

Archive of Mechanical Engineering

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2022

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LXIX, nr 4

693--711

EN

In this paper the analysis of backlash influence on the spectrum of torque at the output shaft of a cycloidal gearbox has been performed. The model of the single stage cycloidal gearbox was designed in the MSC Adams. The analysis for the excitation with the torque and the analysis with constant angular velocity of the input shaft were performed. For these analyses, the amplitude spectrums of the output torque for different backlashes was solved using FFT algorithm. The amplitude spectrums of the combined sine functions composed of the impact to impact times between the cycloidal wheel and the external sleeves were computed for verification. The performed studies show, that the backlash has significant influence on the output torque amplitude spectrum. Unfortunately the dependencies between the components of the spectrum and the backlash could not be expressed by linear equations, when vibrations of the output torque in the range of (350 Hz – 600 Hz) are considered. The gradual dependence can be found in the spectrum determined for the combined sine functions with half-periods equal impact-to-impact times. The spectrum is narrower for high values of backlash.

10

Intelligent system of noise control of the technical condition of railroad tracks

Aliev Telman, Babayev Tofig, Alizada Tahir, Alibayli Elnur, Ahmedov Heybatulla

Transport Problems

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2021

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T. 16, z. 1

65--73

EN

It is shown that modern geometry cars, flaw detector cars and other track test cars provide reliable control of the technical condition of all hauls of the railroad track at “certain intervals of time”. Their number is limited and therefore “continuous monitoring” of all hauls is almost impossible. At the same time, in real life, due to the impact of various factors, such as seismic processes, certain changes take place even a day after control. The authors consider one option for continuous monitoring of the beginning of changes in the technical condition of the track using intelligent tools, which allow one, by analyzing the useful signal and the noise from the soil vibrations caused by the rolling stock, to create informative attributes for identifying the technical condition of the track. The application of traditional technologies of correlation and spectral analysis and other methods for this purpose does not allow ensuring adequacy of the control results. This paper proposes a technology for extracting and analyzing useful vibration signals, the noise of vibration signals and the relationship between them. The estimates of both correlation and spectral characteristics of the useful signal and the noise are used as the main carriers of diagnostic information. Due to the simplicity and the reliability of implementation of the proposed technical tools, they can be easily installed in one of the cars of all rolling stocks, providing control of the beginning of changes in the technical condition of the track during their movement in all hauls

11

Rotor faults diagnosis by adjustable window function

Koura Mohamed Boudiaf, Boudinar Ahmed Hamida, Bendiabdellah Azeddine, Aimer Ameur Fethi, Gherabi Zakaria

Przegląd Elektrotechniczny

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2021

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R. 97, nr 3

123--129

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.

12

Spectral response of stationary jack-up platforms loaded by sea waves and wind using perturbation method

Rozmarynowski Bogdan, Jesien Wojciech

Polish Maritime Research

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2021

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nr 4

53--62

EN

The paper addresses non-linear vibrations of offshore jack-up drilling platforms loaded by sea waves and wind in their stationary condition using the perturbation method. Non-linearity of dynamic equations of motion for fixed offshore platforms yields from two factors. The first is load excitation generating non-linear velocity coupling in a dynamic system. This coupling is inherent in the modified Morison equation, involving the excitation function in the form of the sum of the inertial and velocity forces of sea waves, taking into account relative wave–structure kinematics. Moreover, the wind acting on the exciting side causes similar effects. The second source is the subsoil‒structure interaction problem, modelled by a system of springs and dashpots that yields stochastic non-linearity of the dynamic system. The matrix equations of structural motion in FEM terms are set up. The perturbation method is adopted to determine the mechanical response of the system, making it possible to determine response spectra of the first and the second approximations for displacements and internal forces of the platform. The paper is the continuation of research detailed in the paper [1]. It is assumed, that the fluctuation parts of the dynamic loading forces are in line with the direction of sea wave propagation. Sea current and lift forces effects are neglected in this study. A numerical example refers to structural data of the Baltic drilling platform in the stationary configuration, i.e. when three legs support the deck above the seawater level.

13

Nowoczesne uniwersalne zabezpieczenia cyfrowe wyposażone w algorytmy do diagnostyki stanu klatki silników indukcyjnych

Duda Arkadiusz, Sułowicz Maciej, Tulicki Jarosław, Węgiel Tomasz, Iwiński Marcin

Napędy i Sterowanie

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2021

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R. 23, nr 12

48--55

PL

Zabezpieczenia cyfrowe dedykowane dla silników indukcyjnych mogą realizować różne i nawet bardzo złożone algorytmy ochrony silnika przed skutkami nieprzewidzianych zakłóceń jego bezawaryjnej pracy. Moc obliczeniowa aktualnie stosowanych cyfrowych urządzeń zabezpieczeniowych jest bardzo duża, a pamięci do składowania rejestrowanych informacji przez te urządzenia mogą być dowolnie rozszerzane. Pozwala to producentom zabezpieczeń poszerzyć w łatwy sposób ich funkcjonalności o nowe wybrane funkcje np. do diagnostyki stanu silnika. W artykule skupiono się nad opisem algorytmów do diagnostyki stanu klatki wirnika silników indukcyjnych podczas ustalonego stanu pracy i rozruchu zaimplementowanego w zabezpieczeniu cyfrowym silnika BEL_plus. Przedstawiono wyniki testów zabezpieczenia z zastosowanym algorytmem oraz propozycje wskaźnika diagnostycznego świadczącego o uszkodzeniu dla przykładowego silnika małej mocy z różnymi uszkodzeniami wirnika oraz wyniki testów dla silnika dużej mocy. Udowodniono, że zaproponowane algorytmy działają poprawnie i pozwalają na skuteczną ocenę stanu klatki nadzorowanych silników indukcyjnych.

EN

Digital protections dedicated to induction motors can implement various, even very complex, algorithms to protect the motor against the effects of unforeseen disturbances in its failure-free operation. The computational power of the currently used digital protection devices is very high. Also, the recorded information storage space used by these devices can be freely extended. This allows security manufacturers to easily extend their functionality with new diagnostic functions. The article describes the algorithms for diagnostics of the rotor cage condition of induction motors during steady-state and start-up. The tests’ results of the implemented algorithms and diagnostic indicators of digital protection BEL_plus for a low-power motor with various rotor damage and test results for a high-power motor are presented. The algorithms work correctly and allows for an effective assessment of the condition of the monitored motors given that the required operating conditions are met.

14

Skuteczne algorytmy diagnostyki stanu klatki silników indukcyjnych zaimplementowane w nowoczesnym uniwersalnym zabezpieczeniu cyfrowym

Duda Arkadiusz, Sułowicz Maciej, Tulicki Jarosław, Węgiel Tomasz, Iwiński Marcin

Maszyny Elektryczne : zeszyty problemowe

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2021

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Nr 2 (126)

137--142

PL

Zabezpieczenia cyfrowe dedykowane dla silników indukcyjnych mogą realizować różne i nawet bardzo złożone, algorytmy ochrony silnika przed skutkami nieprzewidzianych zakłóceń jego bezawaryjnej pracy. Moc obliczeniowa aktualnie stosowanych cyfrowych urządzeń zabezpieczeniowych jest bardzo duża a pamięci do składowania rejestrowanych informacji przez te urządzenia może być dowolnie rozszerzana. Pozwala to producentom zabezpieczeń poszerzyć w łatwy sposób ich funkcjonalności o nowe wybrane funkcje np. do diagnostyki stanu silnika. W artykule skupiono się nad opisem algorytm do diagnostyki stanu klatki wirnika silników indukcyjnych podczas ustalonego stanu pracy zaimplementowanego w zabezpieczeniu cyfrowym silnika BEL_plus. Przedstawiono wyniki testów zabezpieczenia z zastosowanym algorytmem oraz propozycje wskaźnika diagnostycznego świadczącego o uszkodzeniu dla przykładowego silnika małej mocy z różnymi uszkodzeniami wirnika oraz wyniki testów dla silnika dużej mocy. Udowodniono, że zaproponowany algorytm działa poprawnie i pozwala na skuteczną ocenę stanu klatki nadzorowanych silników indukcyjnych.

EN

Digital protections dedicated to induction motors can implement various, even very complex, algorithms to protect the motor against the effects of unforeseen disturbances in its failure-free operation. The computational power of the currently used digital protection devices is very high. Also, the recorded information storage space used by these devices can be freely extended. This allows security manufacturers to easily extend their functionality with new diagnostic functions. The article describes an algorithm for diagnostics of the rotor cage condition of induction motors during steady-state. The tests’ results of the implemented algorithm and diagnostic indicator of digital protection BEL_plus for a low-power motor with various rotor damage and test results for a high-power motor are presented. The algorithm works correctly and allows for an effective assessment of the condition of the monitored motors given that the required operating conditions are met.

15

A new optimization method based on Perry's idea through the use of the matrix power

Hafaidia Imane, Benrabia Noureddine, Ghiat Mourad, Guebbai Hamza

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 4

29--41

EN

The purpose of this paper is to present a new conjugate gradient method for solving unconstrained nonlinear optimization problems, based on Perry’s idea. An accelerated adaptive algorithm is proposed, where our search direction satisfies the sufficient descent condition. The global convergence is analyzed using the spectral analysis. The numerical results are described for a set of standard test problems, and it is shown that the performance of the proposed method is better than that of the CG-DESCENT, the mBFGS and the SPDOC.

16

Vibroacoustic analysis in the assessment of the technical condition of the aircraft airframe composite elements

Mokrzan Daniel, Milewicz Julia, Szymański Grzegorz M., Szrama Sławomir

Diagnostyka

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2021

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Vol. 22, No. 2

11--20

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.

17

Detection of partial rotor bar rupture of a cage induction motor using least square support vector machine approach

Birame M’hamed, Bessedik Sid Ahmed, Benkhoris Mohamed Fouad

Diagnostyka

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2021

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Vol. 22, No. 1

57--63

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.

18

Evaluation of GGMs based on the terrestrial gravity disturbance and Moho depth in Afar, Ethiopia

Alemu Eyasu

Artificial Satellites : Journal of Planetary Geodesy

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2021

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Vol. 56, No. 3

78--100

EN

To estimate Moho depth, geoid, gravity anomaly, and other geopotential functionals, gravity data is needed. But, gravity survey was not collected in equal distribution in Ethiopia, as the data forming part of the survey were mainly collected on accessible roads. To determine accurate Moho depth using Global Gravity Models (GGMs) for the study area, evaluation of GGMs is needed based on the available terrestrial gravity data. Moho depth lies between 28 km and 32 km in Afar. Gravity disturbances (GDs) were calculated for the terrestrial gravity data and the recent GGMs for the study area. The model-based GDs were compared with the corresponding GD obtained from the terrestrial gravity data and their differences in terms of statistical comparison parameters for determining the best fit GGM at a local scale in Afar. The largest standard deviation (SD) (36.10 mGal) and root mean square error (RMSE) (39.00 mGal) for residual GD and the lowest correlation with the terrestrial gravity (0.61 mGal) were obtained by the satellite-only model (GO_CONS_GCF_2_DIR_R6). The next largest SD (21.27 mGal) and RMSE (25.65 mGal) for residual GD were obtained by the combined gravity model (XGM2019e_2159), which indicates that it is not the best fit model for the study area as compared with the other two GGMs. In general, the result showed that the combined models are more useful tools for modeling the gravity field in Afar than the satellite-only GGMs. But, the study clearly revealed that for the study area, the best model in comparison with the others is the EGM2008, while the second best model is the EIGEN6C4.

19

On the Audibility of Electric Guitar Tonewood

Jasiński Jan, Oleś Stanisław, Tokarczyk Daniel, Pluta Marek

Archives of Acoustics

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2021

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Vol. 46, No. 4

571--578

EN

Electric guitar manufacturers have used tropical woods in guitar production for decades claiming it as beneficiary to the quality of the instruments. These claims have often been questioned by guitarists but now, with many voices raising concerns regarding the ecological sustainability of such practices, the topic becomes even more important. Efforts to find alternatives must begin with a greater understanding of how tonewood affects the timbre of an electric guitar. The presented study examined how the sound of a simplified electric guitar changes with the use of various wood species. Multiple sounds were recorded using a specially designed test setup and their analysis showed differences in both spectral envelope and the generated signal level. The differences between the acoustic characteristics of tones produced by the tonewood samples explored in the study were larger than the just noticeable differences reported for the respective characteristics in the literature. To verify these findings an informal listening test was conducted which showed that sounds produced with different tonewoods were distinguishable to the average listener.

20

Noise control of the beginning and development dynamics of faults in the running gear of the rolling stock

Aliev Telman, Babayev Tofig, Alizada Tahir, Rzayeva Narmin

Transport Problems

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2020

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T. 15, z. 2

83--91

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.