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Abstract

The present paper is comparing the results of research studies carried out for three road acoustic screens of different design and different number of damping layers. For the tests, we selected timber or steel screens with a traditional multilayer structure and also one innovative type of simplified design. With respect to particular panels, their sound absorption properties were investigated in the reverberation chamber after they had been subjected to simulated weathering. In the process, two screens were subjected to the aging tests of 50–500 cycles in a special climatic chamber, and the innovative screens were subjected to 1000 cycles. The procedure was repeated every 50 or 100 cycles in order to obtain the changes of acoustic characteristics. The changes taking place in the absorbing material were also investigated with the use of scanning electron microscopy method (SEM). Basing on the obtained results and on the statistical analysis, the capability to maintain acoustic properties by the panels during their service life in natural conditions was estimated. For that purpose, linear statistical models were worked out, which were then applied to estimate the value of the single number sound absorption coefficient after successive aging cycles as well as the predicted time periods of acoustic class changes.
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Authors and Affiliations

Artur Nowoświat
Jerzy Bochen
Leszek Dulak
Rafał Żuchowski
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Abstract

Samples of CdTe single crystals which are used as radiation detectors were periodically measured during a long time interval with different values of an applied voltage. The samples were also periodically exposed during long time periods to high temperatures of 390 K and to rapid changes of temperature from 300 K to 390 K. After 1.5 years of measurements we observed ageing of the samples which resulted in deterioration of their transport characteristics. The resistance of the samples increased significantly and current-voltage characteristics were unstable in time. Noise spectroscopy showed that low frequency noise can be used for detection of CdTe sample ageing as its spectral density increases significantly comparing to the 1/f noise of a high quality sample

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Authors and Affiliations

Lubomír Grmela
Ondřej Šik
Alexey Andreev
Josef Sikula
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Abstract

In the paper, the assessment of safety of the pipelines elements from the heat and power generating plants of Ukraine made of l 2Kh I MF steel has been presented. The SINT AP procedures for failure assessment have been performed assuming two shapes of hypothetical cracks along the straight segments of pipeline. The thermal stresses during the cooling process have been taken into account in the analysis. The analysis has been performed at the first level of SINT AP procedures. Two stages: a) before pipeline operation and b) after 156000 hours of service work have been analyzed. The comparison of results obtained by other assessment method has been made.
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Authors and Affiliations

Ihor Dzioba

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