Ústav výkonové elektrotechniky a elektroniky
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- ItemTopology Optimization of Rotor Bars Geometry and Arrangement for a Line-Start Permanent Magnet Synchronous Machine(IEEE, 2021-08-13) Bárta, Jan; Knebl, Ladislav; Bramerdorfer, Gerd; Lolová, Iveta; Silber, Siegfried; Vítek, OndřejAn optimally designed line-start permanent magnet synchronous machine may require a different squirrel-cage design than traditional induction machines. The objective of this paper is to apply topology optimization based on the normalized Gaussian network in order to find the optimal shape of the rotor bars for a line-start permanent magnet synchronous machine. This approach facilitates optimizing the shape of the bar, without the limitation of a predefined bar geometry and arrangement, as is usually considered for classic induction machine design. For this study, a previously designed four-pole line-start permanent magnet synchronous machine with a rated power of 1.5kW is used as an initial design. To verify the accuracy of performance evaluation by utilizing finite-element methods, a prototype of this machine was built and tested. Then, verified model of line-start permanent magnet machine is used for topology optimization of its rotor cage area. The outcome of the optimization is the Pareto front, from which three optimized designs are selected. Finally, these designs are analyzed and proved to have better steady-state performance than the initial machine. The results provide new insights for the design of squirrel-cage bars for line-start permanent magnet synchronous machines.
- ItemSynthesis of Ag and Cu nanoparticles by plasma discharge in inorganic salt solutions(De Gruyter, 2023-06-30) Horák, Jakub; Nikiforov, Anton; Krčma, František; Březina, Matěj; Kozáková, Zdenka; Dostál, Lukáš; Kalina, Michal; Kalina, LukášIn recent years, nanoparticles have emerged as an important player in a broad range of applications, especially thanks to recent advances in their synthesis. The silver and copper nanoparticles are often used due to their antibacterial and fungicidal activities, and this article presents the results of the nanoparticle synthesis using electrical glow discharge generated directly in a volume of their salt solutions. Therefore, there is no influence of air (i.e. reactive nitrogen species) as it is usual in other commonly used approaches. Nanoparticles were prepared under various experimental conditions, and they were characterized by ultraviolet/visible spectrometry, dynamic light scattering, X-ray photoelectron spectroscopy, and high-resolution scanning electron microscopy. Particles were produced without any surfactant or stabilizing agent, and some of them showed higher resistance against agglomeration during their short-term (days) storage. The nanoparticle formation mechanism was confirmed by the fast camera imaging. Thus, the developed approach can be applied for simple environmentally friendly nanoparticle production for various applications.
- ItemInfluence of metal vapours on radiation characteristics of air arc plasmas(ČVUT, 2020-11-18) Bartlová, Milada; Kloc, Petr; Aubrecht, Vladimír; Bogatyreva, NaděždaThis paper deals with the evaluation of radiation properties of air arc plasma with various admixtures of Cu, Ag, and Fe, respectively. Under assumption of isothermal plasma cylinder, the net emission coefficients were calculated for various arc radii as a function of the plasma temperature up to 30 000 K. For plasma with prescribed temperature profile, the equation of radiation transfer was solved in the P1 approximation, and the radiation flux and its divergence were calculated.
- ItemTRIZ already 35 years in the Czech Republic(Elsevier B.V., 2016-02-10) Bušov, Bohuslav; Žídek, Jan; Bartlová, MiladaIn this paper the authors summarize the experience of teaching and implementation TRIZ at technical universities and findings from teaching and applications in companies in the Czech Republic and Slovakia for the last 35 years.
- ItemExperimental model of occluded biliary metal stent recanalization using irreversible electroporation via a tubular catheter(Taylor & Francis, 2021-03-07) Rohan, Tomáš; Andrašína, Tomáš; Jůza, Tomáš; Matkulčík, Peter; Novotná, Veronika; Červinka, Dalibor; Bernard, Vladan; Válek, Vlastimil; Nahum Goldberg, ShragaPurpose To demonstrate the feasibility of irreversible electroporation (IRE) for treating biliary metal stent occlusion in an experimental liver model. Methods and materials IRE was performed using an expandable tubular IRE-catheter placed in nitinol stents in the porcine liver. A 3-electrode IRE-catheter was connected to an IRE-generator and one hundred 100 mu s pulses of constant voltage (300, 650, 1000, and 1300 V) were applied. Stent occlusion was simulated by insertion of liver tissue both ex vivo (n = 94) and in vivo in 3 pigs (n = 14). Three scenarios of the relationship between the stent, electrodes, and inserted tissue (double contact, single contact, and stent mesh contact) were studied. Electric current was measured and resistance and power calculated. Pigs were sacrificed 72 h post-procedure. Harvested samples (14 experimental, 13 controls) underwent histopathological analysis. Results IRE application was feasible at 300 and 650 V for the single and double contact setup in both ex vivo and in vivo studies. Significant differences in calculated resistance between double contact and single contact settings were observed (ex-vivo p < 0.0001, in-vivo p = 0.02; Mann-Whitney). A mild temperature increase of the surrounding liver parenchyma was noted with increasing voltage (0.9-5.9 degrees C for 300-1000 V). The extent of necrotic changes in experimental samples in vivo correlated with the measured electric current (r (2) = 0.39, p = 0.01). No complications were observed during or after the in-vivo procedure. Conclusion Endoluminal IRE using an expandable tubular catheter in simulated metal stent occlusion is feasible. The relationship of active catheter electrodes to stent ingrowth tissue can be estimated based on resistance values.