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Plzeň, Czech Republic

Krutina A.,University of West Bohemia | Piclova P.,University of West Bohemia | Vostracky Z.,University of West Bohemia | Polivka J.,University of West Bohemia | And 3 more authors.
Proceedings of the 6th International Scientific Symposium on Electrical Power Engineering, ELEKTROENERGETIKA 2011 | Year: 2011

Transmission capacity of overhead lines is determined for the rated and for the short-circuit current. With a growing share of energy produced from renewable energy sources are found dynamically changing performance and requires a temporary increase in transmitted power. The article analyzes the current maximum value, higher than nominal, depending on the initial flow and ambient conditions. Determination of the dynamic load wire lines, unlike the steady load, to efficiently use the capacity of overhead lines for a temporary increase in transmitted power.( Possible Loading of the Transmission Chain). Technical University of Košice © 2011. Source

Mehrdad A.,Amirkabir University of Technology | Mahnaz S.,New Technologies Research Center | Hossein A.,Amirkabir University of Technology
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

Piezoelectric excited millimeter-sized cantilevers (PEMCs) have been used widely in different sensing applications. These sensors consist of a piezoelectric layer which is mounted on a non-piezoelectric elastic sub-layer. In this paper, performance of PEMC mass sensors whose cross-sectional area varies continuously with position along the length of the sensor, has been studied. For this purpose, Finite element method (FEM) has been used to explore the sensitivity of PEMC mass sensors with different types of surface profile. To validate the results achieved by FEM, sensors was designed, fabricated and tested through experimental setup. Operating principle of these sensors is based on electromechanical impedance measurments of piezoelectric layer attched to PEMC. Performance of sensors have been studied for different values of added masses from 1 mg to 5 mg. FEM results are in a good agreement with experimental ones in such an extent that absolute deviation of resonance frequencies obtained by FEM from experimental ones, are less than 5 percent. The results, show that sensitivity of PEMC mass sensors is highly affected by their surface profile. For 1 mg added mass, reducing the width of the cantilever tip from 3 (rectangular shape) to 0 mm (traingular shape), increases the sensitivity from 8 to 61KHz/gr. Source

Savkova J.,New Technologies Research Center | Choteborsky R.,CZU | Blahova O.,ZCU
METAL 2013 - 22nd International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2013

The effect of plastic deformation on microstructure of Fe-B alloys containing different boron and chromium concentrations has been investigated. A set of sample with different carbon, chromium, nickel and boron content has been prepared. The solidification microstructures of Fe-B cast alloy consist of the boride, pearlite, ferrite and martensite. Chemical composition (GDOES) and microstructure of the as-cast alloys have been investigated. Borides grow up along the grain boundary of austenite during the formation of eutectic. Results showed that the mechanical properties of high boron cast iron depend on alloying elements like chromium or nickel. Also we found that chromium and molybdenum were dissolved in the borides. © 2013 TANGER Ltd., Ostrava. Source

Smazalova E.,University of West Bohemia | Houdkova S.,New Technologies Research Center | Svantner M.,New Technologies Research Center
METAL 2014 - 23rd International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2014

In many research articles dealing with tribological characteristics of sliding couples measured by Block-on-Ring test, the discontinuous course of the test appears in order to evaluate cumulative mass loss during the test. According to the ASTM G-77-05, the wear rate is supposed to be determine after the end of the test without interrupting, by evaluation of volume loss based on the measurements of wear scars geometrical characteristics. The question of the influence of the discontinuity of the test remains usually unanswered. Therefore, this paper studies experimentally the effects of a discontinuous course test on the tribological properties of the material in comparison with continuous course test. Tests were carried out by a Block-on-Ring test according to ASTM G77-05 and according to modified testing methodology with discontinuities, using the tribometer CETR-UMT3 with equal settings of other test parameters. Furthermore, except of usually measured characteristic such as coefficient of friction and wear, the experimental evaluation of temperature characteristics of sample pairs: ring and block is presented in the paper. For determining of the thermal properties, a thermal camera με TIM was used. In these tests was captured the processes and maximum temperatures in the contact area, and the measured results was correlated with the results of friction measurements. Source

Maroufi M.,New Technologies Research Center | Maroufi M.,Amirkabir University of Technology | Shamshirsaz M.,New Technologies Research Center
Microsystem Technologies | Year: 2012

Resonant Piezoelectric-excited Millimetersized Cantilevers (PEMC), has attracted many researchers' interest in the applications such as liquid level and density sensing. As in these applications, the PEMC are partially immersed in liquid, an appropriate analytical model is needed to predict the dynamic behavior of these devices. In this work, a PEMC has been fabricated for liquid level sensing. An analytical model based on Euler-Bernoulli beam theory and energy method is developed and applied to evaluate the performance of this device with respect to different tip immersion depth. To validate the proposed model, the theoretical results are compared with the experimental results for the tip immersion depth from 5 to 15 mm in water. The simulation results are in almost good agreement with experimental data. Using the proposed model, the two key parameters of sensor performance: sensitivity and working range have been examined for different mode shapes of PEMC vibration. © Springer-Verlag 2012. Source

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