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Uncertainty and compatibility of direct frequency measurement
Zikmund, Ondřej ; Zavřel, Jiří (referee) ; Havlíková, Marie (advisor)
This thesis is focused on evaluation of direct measurement of frequency with the calculation of the standard uncertainty. The part of this thesis is comparison of frequency measurement through the different digital measuring instrument with reference measuring instrument – the scaler HP 53131A. The main aim in thesis is to master the methodology of uncertainty calculation and the evaluation of compatibility of measurement. The result of this thesis is comparison of results of frequency measurement through HP 53131A, GFC-8131H, HP 34401A, M-3890D including the graphic interpretation.
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Characterization of lead-free piezoelectric ceramics
Šťastná, Magdaléna ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This project is focused on lead-free piezoelectric ceramics which are meda in CEITEC. Behaviour of these ceramics is quite different from the lead one. The first part is dedicated to dielectrics and its polarisation techniques. These techniques also include the piezoelectric effect which occurs only in crystals without central symmetry. The following part is focused on piezoelectric materials, piezoelectric polymers and piezoelectric ceramics respectively. The next section of the project is dedicated to the design of an experimental workplace for direct measurement of the piezoelectric charge coefficient đť‘‘33. The experimental part of the work is focused on electric characterisation of lead-free piezoceramics.
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The improvement of efficiency of three-phase induction motors
Vinkler, Stanislav ; Ondrůšek, Čestmír (referee) ; Vítek, Ondřej (advisor)
This work is dedicated to increasing the effectiveness of a particular draft induction motor, which was before the change and subjected to laboratory measurements according to EN60034 - 2-1, an analytical calculation of the losses and the overall efficiency and analysis program RMxprt. The first part focuses on the analysis of measurement data, measurement of partial loss in the machine and overall efficiency. In the second chapter, losses and efficiency calculated analytically, in the first case using the links in the professional literature dealing with the design of electric motors and in the second case by a program for the rapid design of rotating electrical machines, RMxprt program. At the end of this chapter all parameters are obtained measurements and calculations are compared. The third chapter is devoted to the calculation of losses and the resulting efficiency machines in a computer program, in which I gradually adopted changes to increase the efficiency of electrical machines. It also shows the calculation of the new dimensions of the stator and rotor slots. In the fourth chapter, the preparation of documentation for the production of a new two-layer winding for the current machine, while preserving the original dimensions of stator slots. The last part is devoted to the analysis of measurement data on the supplied asynchronous motor with a newly designed stator winding. In conclusion then discussed the results of work.
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Magnetocaloric properties of rare-earth compounds
Kaštil, Jiří ; Javorský, Pavel (advisor) ; Kolomiets, Alexander (referee) ; Solzi, Massimo (referee)
This work presents study of magnetocaloric properties of compounds exhibiting unusual magnetic characteristics. Several systems were studied: TbNiAl, (Tb,Y)NiAl, TbNi(Al,In), TbFeAl, GdFeAl, Ni2MnGa based compounds and amorphous metallic alloy Gd-Co-Al-Y. Influence of magneto-crystalline anisotropy on magnetocaloric effect was studied on singlecrystalline sample of TbNiAl compound. The maximum of entropy change was measured with orientation of magnetic field along c axis and compared to polycrystalline sample a 100% increase was observed. Substitutions of Y and In in TbNiAl led to a change of magnetic ordering. Both substitution led to increase of RCP values of studied material. TbFeAl and GdFeAl compounds, characterized by partial disorder of Fe and Al atoms, showed magnetocaloric effect in wide temperature region which led to interesting values of RCP~350 J kg-1 . Very broad region of magnetocaloric effect was also observed on amorphous metallic material of Gd-Co-Al-Y. The effect of Er substitution in Ni2MnGa based compound on its magneto-structural transition, connected with inverse magnetocaloric effect, was studied. The direct measurement method of adiabatic temperature change is described and instrument for such measurement, developed in collaboration with FZU AVČR, v.v.i., is presented.
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Characterization of lead-free piezoelectric ceramics
Šťastná, Magdaléna ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This project is focused on lead-free piezoelectric ceramics which are meda in CEITEC. Behaviour of these ceramics is quite different from the lead one. The first part is dedicated to dielectrics and its polarisation techniques. These techniques also include the piezoelectric effect which occurs only in crystals without central symmetry. The following part is focused on piezoelectric materials, piezoelectric polymers and piezoelectric ceramics respectively. The next section of the project is dedicated to the design of an experimental workplace for direct measurement of the piezoelectric charge coefficient đť‘‘33. The experimental part of the work is focused on electric characterisation of lead-free piezoceramics.
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|
|
Magnetocaloric properties of rare-earth compounds
Kaštil, Jiří ; Javorský, Pavel (advisor) ; Kolomiets, Alexander (referee) ; Solzi, Massimo (referee)
This work presents study of magnetocaloric properties of compounds exhibiting unusual magnetic characteristics. Several systems were studied: TbNiAl, (Tb,Y)NiAl, TbNi(Al,In), TbFeAl, GdFeAl, Ni2MnGa based compounds and amorphous metallic alloy Gd-Co-Al-Y. Influence of magneto-crystalline anisotropy on magnetocaloric effect was studied on singlecrystalline sample of TbNiAl compound. The maximum of entropy change was measured with orientation of magnetic field along c axis and compared to polycrystalline sample a 100% increase was observed. Substitutions of Y and In in TbNiAl led to a change of magnetic ordering. Both substitution led to increase of RCP values of studied material. TbFeAl and GdFeAl compounds, characterized by partial disorder of Fe and Al atoms, showed magnetocaloric effect in wide temperature region which led to interesting values of RCP~350 J kg-1 . Very broad region of magnetocaloric effect was also observed on amorphous metallic material of Gd-Co-Al-Y. The effect of Er substitution in Ni2MnGa based compound on its magneto-structural transition, connected with inverse magnetocaloric effect, was studied. The direct measurement method of adiabatic temperature change is described and instrument for such measurement, developed in collaboration with FZU AVČR, v.v.i., is presented.
|
|
|
Uncertainty and compatibility of direct frequency measurement
Zikmund, Ondřej ; Zavřel, Jiří (referee) ; Havlíková, Marie (advisor)
This thesis is focused on evaluation of direct measurement of frequency with the calculation of the standard uncertainty. The part of this thesis is comparison of frequency measurement through the different digital measuring instrument with reference measuring instrument – the scaler HP 53131A. The main aim in thesis is to master the methodology of uncertainty calculation and the evaluation of compatibility of measurement. The result of this thesis is comparison of results of frequency measurement through HP 53131A, GFC-8131H, HP 34401A, M-3890D including the graphic interpretation.
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The improvement of efficiency of three-phase induction motors
Vinkler, Stanislav ; Ondrůšek, Čestmír (referee) ; Vítek, Ondřej (advisor)
This work is dedicated to increasing the effectiveness of a particular draft induction motor, which was before the change and subjected to laboratory measurements according to EN60034 - 2-1, an analytical calculation of the losses and the overall efficiency and analysis program RMxprt. The first part focuses on the analysis of measurement data, measurement of partial loss in the machine and overall efficiency. In the second chapter, losses and efficiency calculated analytically, in the first case using the links in the professional literature dealing with the design of electric motors and in the second case by a program for the rapid design of rotating electrical machines, RMxprt program. At the end of this chapter all parameters are obtained measurements and calculations are compared. The third chapter is devoted to the calculation of losses and the resulting efficiency machines in a computer program, in which I gradually adopted changes to increase the efficiency of electrical machines. It also shows the calculation of the new dimensions of the stator and rotor slots. In the fourth chapter, the preparation of documentation for the production of a new two-layer winding for the current machine, while preserving the original dimensions of stator slots. The last part is devoted to the analysis of measurement data on the supplied asynchronous motor with a newly designed stator winding. In conclusion then discussed the results of work.
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