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1

A discrete model for nonlinear vibrations of a simply supported cracked beams resting on elastic foundations

Khnaijar A., Benamar R.

Diagnostyka

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2017

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Vol. 18, No. 3

39--46

EN

The present paper introduces a discrete physical model to approach the problem of nonlinear vibrations of cracked beams resting on elastic foundations. It consists of a beam made of several small bars, evenly spaced, connected by spiral springs, presenting the beam bending stiffness. The crack is modeled by a spiral spring with a reduced stiffness and the Winkler soil stiffness is modeled using linear vertical springs. Concentrated masses, presenting the inertia of the beam, are located at the bar ends. The nonlinear effect, due to the axial forces in the bars resulting from the change in their length, is presented by longitudinal springs. This model has the advantage of simplifying parametric studies, because of its discrete nature, allowing any modification in the mass and the stiffness matrices, and in the nonlinearity tensor, to be made separately. After establishing the model, various practical applications are performed without the need of going through all the formulation again. Numerical linear and nonlinear results are given, corresponding to a cracked simply supported beam.

2

Cellular automata to describe seismicity: a review

Jiménez A.

Acta Geophysica

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2013

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Vol. 61, no. 6

1325--1350

EN

Cellular Automata have been used in the literature to describe seismicity. We first historically introduce Cellular Automata and provide some important definitions. Then we proceed to review the most important models, most of them being variations of the spring-block model proposed by Burridge and Knopoff, and describe the most important results obtained from them. We discuss the relation with criticality and also describe some models that try to reproduce real data.

3

Evaluation of the QRS complex wavelet based detection algorithm

Jóśko A.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 5

66-70

EN

The article concerns the problem of computer aided electrocardiography signals analysis. Automatic analysis of these signals starts with QRS-complex detection which is the principal task. Reliability rate achieved at this stage affects all ECG signal parameters determined at the following steps of automated analysis process. This fact proves that the first stage of ECG signals analysis is of high importance. Detailed discussion of obtained results plays the main role of the article.

PL

Artykuł dotyczy problematyki występującej we wspomaganej komputerowo analizie sygnałów elektrokardiograficznych. Podstawowym zadaniem, które rozpoczyna analizę jest detekcja zespołów QRS. Wiarygodność wyników otrzymanych na tym etapie, bezpośrednio wpływa na jakość parametrów wyznaczanych na etapach kolejnych. W artykule rzeprowadzono dyskusję i szczegółowy opis wyników.

4

Analiza transformaty falkowej w aspekcie zdolności klasyfikacyjnych odmiennych postaci morfologicznych zespołów QRS

Jóśko A.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 9a

8-11

PL

Przekształcenie falkowe stanowi bardzo efektywne narzędzie do analizy sygnałów elektrokardiograficznych. Cecha ta znakomicie kompensuje relatywnie większy nakład obliczeniowy, jeśli by ją porównać z wieloma odmiennymi technikami stosowanymi na tym polu. Dodatkowo, jak pokazują eksperymenty, własności współczynników przekształcenia falkowego mogą stanowić użyteczny zbiór danych wejściowych w zastosowaniu do klasyfikacji zespołów QRS, pod względem postaci morfologicznych.

EN

Wavelet transform has become a very useful and effective tool for the analysis of electrocardiographic signals. This property redresses remarkably, relatively higher computational effort, as compared to many other approaches used in the field. What is more, performed experiments clearly manifest that the wavelet transform coefficients can be used as a valuable input data set for the QRS complexes classification in terms of their morphology.