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Number of results: 66
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Abstract

Electric energy meters are designed to account energy under sinusoidal and nonsinusoidal conditions, because both, old and new standards for energy meters require testing their accuracy under different conditions. The latest EN 50470 standard increases the range of meter testing under nonsinusoidal conditions, introducing new shapes of test signals such as the phase fired waveform or the burst fired waveform. This paper discusses calibration problems of electronic revenue energy meters for direct connection and for connection through current transformers, and it proposes a new calibration procedure which reproduces normal operating conditions better: three-phase configurations of measurement systems, load range during meter testing or shapes of test signals. Recently, modern Electrical Power Standards, also known as Power Calibrators, enable automatic testing of various types of electrical devices, including electricity meters in their normal operating conditions. This article presents examples of single and multi position fully automatic test systems, which employ Power/Energy Calibrator from Poland as the precision source with programmed waveforms of three phase voltages up to 560 V and currents up to 120 A conforming to EN 50470, or with random waveforms generated by PC software random wave generator. Measurement uncertainty of the energy meters under different nonsinusoidal conditions using a test system with reference to accuracy of the power calibrator or to the reference meter, are discussed. Comparative analysis of test results for different shapes of voltage and current signals is presented in the conclusions of this paper.
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Abstract

Władysław Łuszczkiewicz was an art historian, artist, pedagogue, an outstanding personality of nineteenth-century Krakow, active in many fields. He was a professor at the Cracow School of Fine Arts, and in the years 1857–1873 and 1893–1895 he was the headmaster of this school. He was a teacher of many artists, of which it is enough to mention only the greatest — Jan Matejko, Stanisław Wyspiański, Józef Mehoffer and Artur Grottger. In 1883, Łuszczkiewicz was appointed the director of the National Museum in Krakow. He managed this institution until his death, that is until 1900. Among the oldest source materials belonging to the Archive of the National Museum in Krakow, we can find the correspondence of former students of the School of Fine Arts addressed directly to their former teacher — Professor Łuszczkiewicz, who was at this time the director of the National Museum in Krakow. Based on selected letters, the article presents their interesting subject matter and presents the issues in which the students wrote to their Master. The attempt to describe the relation between former students and their master revealed in letters will be made.
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Abstract

The paper presents the results of the experimental tests of Mg/Al bimetallic bars rolling process in classic and multi-radial modified round-oval-round passes. The bimetallic bar consist of magnesium core, grade AZ31 and aluminium outer layer, grade 1050A. The stocks were round bars with diameter 22.5 mm with an aluminium layer share of 28%. As a result of rolling in four passes, bars of a diameter of about 17 mm were obtained. A bimetallic feedstock was manufactured using an explosive welding method. The use of the designed arrangement of multi-radial modified stretching passes resulted in obtaining Mg/Al bimetallic bars with an uniform distribution of the cladding layer over the bar perimeter and high quality of shear strength between individual layers compared to Mg/Al bars obtained in the classic passes.
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Abstract

The paper presents an analysis of factors influencing the accuracy of reproduction of geometry of the vertebrae and the intervertebral disc of the lumbar motion segment for the purpose of designing of an intervertebral disc endoprosthesis. In order to increase the functionality of the new type of endoprostheses by a better adjustment of their structure to the patient’s anatomical features, specialist software was used allowing the processing of the projections of the diagnosed structures. Recommended minimum values of projection features were determined in order to ensure an effective processing of the scanned structures as well as other factors affecting the quality of the reproduction of 3D model geometries. Also, there were generated 3D models of the L4-L5 section. For the final development of geometric models for disc and vertebrae L4 and L5 there has been used smoothing procedure by cubic free curves with the NURBS technique. This allows accurate reproduction of the geometry for the purposes of identification of a spatial shape of the surface of the vertebrae and the vertebral disc and use of the model for designing of a new endoprosthesis, as well as conducting strength tests with the use of finite elements method.
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Abstract

The paper presents results of a study concerning an AlSi7Mg alloy and the effect of subjecting the liquid metal to four different processes: conventional refining with hexachloroethane; the same refining followed by modification with titanium, boron, and sodium; refining by purging with argon carried out in parallel with modification with titanium and boron salts and strontium; and parallel refining with argon and modification with titanium, boron, and sodium salts. The effect of these four processes on compactness of the material, parameters of microstructure, and fatigue strength of AlSi7Mg alloy after heat treatment. It has been found that the highest compactness (the lowest porosity ratio value) and the most favorable values of the examined parameters of microstructure were demonstrated by the alloy obtained with the use of the process including parallel purging with argon and modification with salts of titanium, boron, and sodium. It has been found that in the fatigue cracking process observed in all the four variants of the liquid metal treatment, the crucial role in initiation of fatigue cracks was played by porosity. Application of the process consisting in refining by purging with argon parallel to modification with Ti, B, and Na salts allowed to refine the microstructure and reduce significantly porosity of the alloy extending thus the time of initiation and propagation of fatigue cracks. The ultimate effect consisted in a distinct increase of the fatigue limit value.
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Abstract

The study was carried out on 50 human lower legs obtained during autopsies (KBET: 122.6120.315.2016). The anatomy of the joint was studied using classical anatomical description methods. Based also on literature we have reviewed the current knowledge on the inferior tibiofibular joint blood supply considering the important clinically aspect - vascular density. Authors of this paper postulate relatively low vascular density of the region described and potential worse condition for healing in case of injury or after surgical procedures performed. We also postulate that ligament screws should be positioned with special respect to time limit which enables proper healing of the syndesmosis.
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Abstract

Biocompatible coatings produced on the basis of the chemically extracted natural hydroxyapatite (HAp) from the animal bones were deposited using multiplex method comprising glow discharge nitriding (GDN) of the titanium alloy substrate and pulsed laser deposition (PLD) of HAp on the formerly fabricated titanium nitride layer (TiN). The TiN interlayer plays an important role improving adhesion of HAp to substrate and preserves the direct contact of the tissue with metallic substrate in the case of possible cracking of HAp coating. Surface morphology of deposited layers, crystallographic texture and residual stress were studied in relation to the type of laser applied to ablation (Nd:YAG or ArF excimer), laser repetition, temperature of substrate and atmosphere in the reactive chamber.
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Abstract

Boron nitride thin layers were produced by means of the pulsed laser deposition technique from hexagonal boron nitride target. Two types of laser i.e. Nd:YAG with Q-switch as well as KrF coupled with RF generator were used. Influence of deposition parameters on surface morphology, phase composition as well as mechanical properties is discussed. Results obtained using Fourier Transformed Infrared Spectroscopy, Transmission and Scanning Electron Microscopy, Atomic Force Microscopy are presented. Micromechanical properties measured during microindentation, scratch and wear tests are also shown.
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