Wyniki wyszukiwania - BazTech

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A study of issues in extreme cases in a numerical solver for nonlinear fractional circuits

Sowa Marcin

Przegląd Elektrotechniczny

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2023

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R. 99, nr 8

212--218

EN

The study deals with the computations of nonlinear fractional circuit analyses in transient states. A numerical solver for FDAE (Fractional Differential-Algebraic Equations) is recalled, which bases on SubIval (acronym for “the subinterval-based method”). In the study, a nonlinear fractional problem was deliberately selected and tuned so as to cause issues occuring only in extreme cases, but motivating the further development of the numerical method. A development idea arises after observations of the error estimation, the influence of the time step adaptivity and the polynomial order.

PL

Praca dotyczy obliczen w analizach nieliniowych obwodów ułamkowych w stanach nieustalonych. Przywołano solwer numeryczny dla ułamkowych równan różniczkowo-algebraicznych, który opiera się na metodzie numerycznej SubIval (akronim od anglojęzycznej nazwy “the subinterval-based method”, czyli “metody podprzedziałów”). W badaniu celowo wybrano i dostrojono nieliniowe zagadnienie ułamkowe tak, aby wywołac komplikacje występujące jedynie w skrajnych przypadkach, ale motywujące do dalszego rozwoju wspomnianej metody numerycznej. Pomysł rozwoju metody pojawia sie po obserwacjach oszacowania błędu, wpływu automatycznego dostosowania kroku czasowego i rzędu wielomianów aproksymujących.

2

Exciter fractional model and its susceptibility on parameter changes

Majka Łukasz, Sowa Marcin

Poznan University of Technology Academic Journals. Electrical Engineering

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2020

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No. 104

87--98

EN

The paper concerns the application of fractional calculus in the modeling of a selected part of a power system generating unit, which is the high frequency AC exciter. The model’s fractional derivative-based generalization is recalled. The basis of the estimation process for the model consists of two sets of measurement waveforms. In order to solve the fractional and nonlinear problem – a numerical solver is applied. The solver and the estimation procedure have been both implemented in GNU Octave. The model parameter susceptibility is examined. The changes of each model parameter value is studied in a way that the influence on the model output is observed.

3

Modelling of examinations of artery wall thickness changes

Powałowski T., Wójcik J., Trawiński Z.

Archives of Acoustics

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2007

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Vol. 32, No. 4

851--857

EN

The developed solver of acoustic field was used for simulation of the artery wall thickness examination. It is capable of describing spatial and time-dependent distribution of an ultrasonic beam, that is emitted by a piezoelectric ring transducer and then backscattered on cylindrical surfaces of the walls in artery models. The electrical signal received corresponds closely with the actual RF signal that is obtained during measurements at the output of the ultrasonic VED apparatus. The theoretical model of the artery for creating the ultrasonic reflected echoes was used. The internal radius of the artery model was equal 3 mm for the diastolic pressure and 3.3 mm for the systolic pressure. The intima-media thickness (IMT) of the artery wall was changed from 0.48 mm to 0.44 mm respectively. The echoes-tracking solver based on the zero-crossing and correlation methods was used for detecting changes of the IMT.