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Experimental study of the influence of using polyurethane cushion to reduce vibration received by a wheelchair user

Chwalik-Pilszyk Gabriela, Dziechciowski Zygmunt, Kromka-Szydek Magdalena, Kozień Marek S.

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 1

137--149

EN

The aim of this experimental study was to compare the ability of polyurethane cushions of three arbitrary selected thicknesses to minimize vibrations transmitted from the wheelchair to its user. Methods: Measurements were made during passive motion on five different surfaces often found in public spaces. Two tests were carried out during the measurements. In the first test, the sensor was located directly on the surface of the wheelchair seat. In the second test, a polyurethane cushion was placed on the seat, on which the measuring sensor was then placed. Results: The study showed that regardless of the surface on which the wheelchair user moves, the threshold defined in the ISO standard for frequencies in the range of 4–40 Hz was exceeded. However, thanks to the use of polyurethane cushions, vibration damping was visible for frequencies ranging from 10 to 40 Hz. The impact of the user’s weight on the magnitude of the perceived vibrations was also observed. Conclusions: Studies show that wheelchair users are exposed to whole body vibration that can negatively affect their health. Cushions made of polyurethane seem to be a promising solution to reduce whole body vibration in the frequency range that is burdensome and harmful to human health.

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Influence of the variability of the shape of short axisymmetric rods on the value of basic natural frequency of longitudinal vibrations

Kozień Marek S.

Vibrations in Physical Systems

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2021

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Vol. 32, nr 2

art. no. 2021212

EN

Rods with a relatively short length in relation to their transverse dimensions with a variable cross-section along the axis, subjected to longitudinal vibrations, have the character of stocky rods, for which the classic geometric principles used for rods are not fully met. For small engineering elements, the postulated design frequencies of natural vibrations in the very high cycle fatigue analyses reach the values of a dozen or so, small, several dozen kHz. In the article, the sensitivity of the value of the basic natural frequency to the change in the shape of the element is analysed and discussed. The analysis is conducted using finite element method.

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Ex-ante risk estimation in the production project

Kozień Ewa, Kozień Marek S.

System Safety : Human - Technical Facility - Environment

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2019

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Vol. 1, nr 1

708--715

EN

Identification and evaluation of risk in the production project in the preliminary phase of its realization has important influence on manager’s decision about the project continuation, the reduction of project realization or the stop of project realization. The method of the quantitative ex-ante risk estimation in the project is proposed in the paper. The aim of the paper is to blow the whistle on importance of the ex-ante identification and estimation of the risk in the production project, as the factor which has positive influence on the project realization and implementation. In the article the following thesis is proposed: the ex-ante identification and estimation of risk in the project contributes to its efficient realization and increase possibility of obtaining the originally defined results.