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Methods for testing of questionnaires and the possibility of utilization of MTMM studies results.
Straka, Pavel ; Vinopal, Jiří (advisor) ; Remr, Jiří (referee)
Na proces evaluace otázek se dá pohlížet ze dvou úhlů. První se zabývá otázkami, jako je pochopení otázek a použitých pojmů, znění otázek, zátěž respondenta, problémy získání požadované informace z paměti, proces vytvoření odpovědi atd. Druhý se zabývá tím, jak se tyto problémy projevují kvantitativně, tzn. zabývají se odhadem chyby měření. Prvním úhlem pohledu a jeho kritickým zhodnocením jejich aplikací se zabývá první kapitola práce. Druhá kapitola se zabývá možnostmi, které nabízí druhý přístup. Statistické přístupy se v kvalitě otázek zabývají reliabilitou, validitou nebo obojím současně. Možnost vyhodnocení těchto indikátorů kvality ovšem přináší jisté nároky na realizaci a design šetření. K odhadům kvality měření se využívá několik přístupů. V české literatuře o nich pojednal Řehák (Řehák 1998) a z toho důvodu se jim tato práce věnuje pouze krátce. Naopak je pozornost zaměřena na další rozpracování MTMM designu, které dosud v české literatuře probráno není. Následné meta analýzy, pracující s výsledky MTMM experimentů se pokouší stanovit míru vlivu designu dotazu (a tedy i některých rozhodnutí výzkumníka o tom, jak daný dotaz koncipovat) na kvalitu dotazu (validitu a reliabilitu) a využít takto získané poznatky pro predikci. Předpokladem samotné predikce je jednak realizace dostatečného počtu...
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Simulation of flow through the tip-section turbine blade cascade for various inlet conditions
Straka, P. ; Příhoda, Jaromír
The contribution deals with the numerical simulation of 2D compressible flow through a tip-section of the turbine blade cascade using the EARSM turbulence model completed by the algebraic transition model. Predictions were carried out at the Reynolds number Re2is = 1.85E+06 for Mach numbers M2is = 1.77 and 1.92. The study was focused on the effect of small changes of flow inlet angle and changes of free-stream turbulence on flow structure in the blade cascade, especially on the shock wave/boundary layer interaction.
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Ultrasound desintegrator of concrements
Straka, Petr ; Čížek, Martin (referee) ; Rozman, Jiří (advisor)
This thesis is focused on the methodes of crushing kidney’s concrements with continual wave for the frequency 27 kHz and the intensity of ultrasound 10 W/cm2. The main aim is design of the ultrasound head with layer converter and design circuitry. First part of this work describes physical principle of ultrasound, ultrasound waves and methods by which could be remove kidney’s concretions. Practical part of this work is focused on compreshive design of ultrasound crushing system. In the introdiction is analyzed the proposal of applicator and the next step decscribing proposal excitation generator. The work contains results of simulation which was done on proposal curcuit, drawings of scheme, list of components and drawing of PCB.
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Modelling of compressible flow through turbine blade cascade with various wall roughness
Příhoda, Jaromír ; Straka, P.
The contribution deals with the numerical simulation of 2D compressible flow through a turbine cascade with smooth and rough blades using the EARSM turbulence model of Hellsten. Predictions were carried out at the Reynolds number Re2is = 850000 for various Mach numbers. The algebraic bypass transition model was applied for comparison in case of smooth blades. Predicted values of the loss coefficient and the flow outlet angle were compared with experimental data for the turbine cascade VS33 with smooth and rough blades of wall roughness.
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Numerical Simulation of Compressible Transitional Flow Through High-Loaded Turbine Blade Cascade
Straka, P. ; Příhoda, Jaromír
The contribution deals with the numerical simulation of compressible transitional flow through the high-loaded turbine blade cascade. The mathematical model is based on the solution of the averaged Navier-Stokes equations closed by the explicit algebraic Reynolds stress model completed by the algebraic transition model taking into account the effect of free-stream turbulence and pressure gradient. The transition model is based on empirical correlations for the onset and the length of the transition region covering a wide range of free-stream turbulence. Various boundary conditions with the transition in attached and separated flows were tested and compared with experimental data.
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Modelling of natural and bypass transition in aerodynamics
Fürst, J. ; Straka, P. ; Příhoda, Jaromír
The paper deals with modification of the transition model with the algebraic equation for the intermittency coefficient proposed originally by Straka and Příhoda (2010) for the bypass transition for modelling of the transition at low free-stream turbulence. The modification is carried out using accessible experimental data for the flat-plate flow. Further, the three-equation k-kL-omega model proposed by Walters and Cokljat (2008) was used for the modelling of the transition at low free-stream turbulence. Both models were tested by means of the incompressible flow around airfoils at moderate and very low free-stream turbulence.
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