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Number of results: 30
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Abstract

The paper addresses the problem of experimental studies of miniature tilt sensors based on low-range accelerometers belonging to Microelectromechanical Systems (MEMS). A custom computer controlled test rig is proposed, whose kinematics allows an arbitrary tilt angle to be applied (i.e. its two components: pitch and roll over the full angular range). The related geometrical relationships are presented along with the respective uncertainties resulting from their application. Metrological features of the test rig are carefully evaluated and briefly discussed. Accuracy of the test rig is expressed in terms of the respective uncertainties, as recommended by ISO; its scope of application as well as the related limitations are indicated. Even though the test rig is mostly composed of standard devices, like rotation stages and incremental angle encoder, its performance can be compared with specialized certified machines that are very expensive. Exemplary results of experimental studies of MEMS accelerometers realized by means of the test rig are presented and briefly discussed. Few ways of improving performance of the test rig are proposed.

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Authors and Affiliations

Sergiusz Łuczak
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Abstract

This article examines some aspects of a broader theme indicated in the title with respect to the diptych Tyrtaeus: A Tragedy and Behind the Scenes: A Fantastic Tale. While the present analysis is based on the fi ndings of earlier critics, it develops various parallels suggested by the use of musical motifs in Norwid’s twin dramas. Those associations act as an aid to a better understanding of the differences between the attitudes and ideas presented in the plays. Moreover, by indirectly marking the contrasts of truth and falsehood, they hold the key to the moral interpretation of the plays. The overall pattern of the musical references and associations in Tyrtaeus and Behind the Scenes appears to refl ect Norwid’s organic philosophy and his idea of creative originality. Finally, the purported pushing of Tyrtaeus off a cliff, an episode symbolizing the rejection of the right path, is analyzed along two similar poetic images of Norwid’s, Aesop’s fall into an abyss (On Freedom of Speech) and the hurling of Chopin’s piano out of the window (‘Chopin’s Piano’).
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Authors and Affiliations

Bartłomiej Łuczak
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Abstract

It is assumed in the paper that the signals in the enclosure in a transient period are similar to a noise induced by vehicles, tracks, cars, etc. passing by. The components of such signals usually points out specific dynamic processes running during the observation or measurements. In order to choose the best method of analysis of these phenomena, an acoustic field in a closed space with a sound source inside is created. Acoustic modes of this space influence the sound field. Analytically, the modal analyses describe the above mentioned phenomena. The experimental measurements were conducted in the room that might comprise the closed space with known boundary conditions and the sound source Brüel & Kjær Omni-directional type 4292 inside. To record sound signals before the field's steady state was reached, the microphone type 4349 and the 4-channel frontend 3590 had been used. The obtained signals have been analysed by using two approaches, i.e. Fourier and the wavelet analysis, with the emphasis on their efficiency and the capability to recognise important details of the signal. The results obtained for the enclosure might lead to the formulation of a methodology for an extended investigation of a rail track or vehicles dynamics.
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Authors and Affiliations

Andrzej Błażejewski
Piotr Kozioł
Maciej Łuczak
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Abstract

The article presents the results concerning the use of clustering methods to identify signals of acoustic emission (AE) generated by partial discharge (PD) in oil-paper insulation. The conducted testing featured qualitative analysis of the following clustering methods: single linkage, complete linkage, average linkage, centroid linkage and Ward linkage. The purpose of the analysis was to search the tested series of AE signal measurements, deriving from three various PD forms, for elements of grouping (clusters), which are most similar to one another and maximally different than in other groups in terms of a specific feature or adopted criteria. Then, the conducted clustering was used as a basis for attempting to assess the effectiveness of identification of particular PD forms that modelled exemplary defects of the power transformer’s oil-paper insulation system. The relevant analyses and simulations were conducted using the Matlab estimation environment and the clustering procedures available in it. The conducted tests featured analyses of the results of the series of measurements of acoustic emissions generated by the basic PD forms, which were obtained in laboratory conditions using spark gap systems that modelled the defects of the power transformer’s oil-paper insulation.
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Authors and Affiliations

Sebastian Borucki
Jacek Łuczak
Dariusz Zmarzły
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Abstract

The paper presents the results of the application of the hierarchical clustering methods for the classification of the acoustic emission (AE) signals generated by eight basic forms of partial discharges (PD), which can occur in paper-oil insulation of power transformers. Based on the registered AE signals from the particular PD forms, using a frequency descriptor in the form of the power spectral density (PSD) of the signal, their representation in the form of the set of points on plane XY was created. Next, these sets were subjected to analysis using research algorithms consisting of selected clustering methods. Based on the suggested numeric performance indicators, the analysis of the degree of reproduction of the actual distribution of points showing the particular time waveforms of the AE signals from eight adopted PD forms (PD classes) in the obtained clusters was carried out. As a result of the analyses carried out, the clustering algorithms of the highest effectiveness in the identification of all eight PD classes, classified simultaneously, where indicated. Within the research carried out, an attempt to draw general conclusions as to the selection of the most effective hierarchical clustering method studied and the similarity function to be used for classification of the selected basic PD forms.
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Bibliography

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Authors and Affiliations

Sebastian Borucki
1
Jacek Łuczak
1
Marcin Lorenc
1

  1. Opole University of Technology, Opole, Poland
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Abstract

This paper presents the results of a fi eld study on using mineral materials (fine-grained sand and medium-grained gravel) to reduce the concentration of readily soluble salts in a roadside environment. The investigated soils were Rendzic Sceletic Leptosols from an urban area characterized by a shallow humus horizon with a high content of skeletal parts, as well as a lack of homogeneity of the material in the soil profile. All soil samples were taken from five plots located along the main streets in the city of Opole (Southern Poland). It was revealed that the use of fine-grained sand and medium-grained gravel improved the structure of the surface soil layer, and thus favoured the migration of Na+ and Cl- ions into the soil profile. In comparison to control surfaces readily soluble salts were reduced with gravel and sand application. Furthermore, the mineral materials introduced on the soil surface for salinity neutralization did not affect the quality of the tested roadside calcareous soils. The results indicate that the use of mineral materials reduces soil salinity caused by NaCl. They also show the need to find new methods of salt neutralization, especially of roadside soils in order to improve and protect the quality of the environment.

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Authors and Affiliations

Katarzyna Łuczak
1
Izabella Pisarek
1
Grzegorz Kusza
1

  1. Department of Land Protection, Faculty of Natural Sciences and Technology, University of Opole, Poland

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