National Repository of Grey Literature 139 records found  1 - 10nextend  jump to record: Search took 0.02 seconds. 
Computational modelling of blood flow in the carotid artery with serial stenosis
Lukáš, Petr ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
The aim of this bachelor's thesis is to analyse the effect of double stenosis on flow and stress characteristics in the carotid artery. First, based on the stated literature, a literature search is conducted regarding blood flow in the arterial system. Then, the procedure of creating idealized models of an artery with double stenosis and the procedure of mesh creation and numerical solution are described. The models have different size of the stenosis and different distance between stenosis. In the final stage, the results are analysed first for stationary flow, then one model is selected on which is performed the analysis for pulsating flow. Analytical calculation of pressure drop and comparison with numerical calculation is also part of this work.
Analysis of specific systems of bodies with neutral bonds
Grúz, Jan ; Hájek, Petr (referee) ; Majer, Zdeněk (advisor)
This thesis deals with analytical and graphical solution of three specific systems of bodies that are in static equilibrium. These systems of bodies contain neutral bonds. The opening part dedicates to theory and principles of solution of contact forces in bonds, which are further used for calculations and graphical solutions. The first system of bodies is a demonstrative tappet mechanism which was created for demonstration of some methods of graphical solution. The second system is inspired by lifting mechanisms in production lines. The aim is to find out the magnitude of contact forces for different positions of the lifted weight and a minimal torque of the propulsion. For solving the third system of bodies, principles of statics and hydrostatics are used. The aim is to find out the minimal magnitude of force for activating the mechanism. All systems of equations are solved in Matlab.
Modal analysis of vocal folds models with descrete parameters
Lekeš, Filip ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
Bachelor’s thesis deals with modal analysis of computed models of human vocal folds. It’s about finite element and analytical model where values first eigenfrequencies come under male vocal folds. Research part applies to biomechanics of vocal the human voice, which is followed by an overview of computational models. Finite element model is completely created and solved by ANSYS Workbench commercial program, which uses the finite element method to simulate a problem. Solution of analytical model uses freely available Python programming language. Analysis of the results and comparison of approaches belong to main objectives of the presented work. The proposed analytical model can serve future students for detailed understanding of human vocal oscillations.
Noise and vibrations of roots blowers
Smrček, Martin ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This thesis is concerned with the spread of noise in the housing sets blowers, blower vibration, due to the shape of the geometry of the individual parts of the blower and the design of a suitable discharge muffler in order to achieve the highest possible attenuation. Analysis blower and silencer discharge was conducted using the finite element simulation ANSYS 15.0
Computational modelling of aerodynamic noise caused by the car’s side mirror
Vobejda, Radek ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
The master’sthesis deals with numerical modelling of aerodynamic noisewhich arisesinside of the carcabin. In the first part ofthe thesis simplified model of geometry of the car and of the inside acoustic pressure arecreated. After that numerical analysis of created models of geometry are doneandvarious models of turbulenceare discussed. The results of these CFD simulationswhere then used for changing the model of geometry of the wing mirror. Outputs of these simulations were used for solving the numerical analysis of noise in the car cabin.
Computational modelling of function of the human vocal tract
Ryšavý, Antonín ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
In the first part of this bachelor's thesis is a brief summary of the biomechanics of the creation of the human voice and an overview of the published computational models of the vocal tract and the area around the head. The second part deals with the computational models of the human vocal tract set to the pronouncing the Czech vowels /a:/ and /i:/ with using the method of transfer matrices and the finite element method. By these methods is perform modal and harmonic analysis. Are investigated the natural frequencies and own vibration shapes of both vowels and course of sound pressure in a specific areas of the vocal tract. The method of transfer matrices is highly depend on the geometry of the tract, particularly on the density of the reference sections and its results in this thesis do not completely agree with the results in the literature. Finite element method is more accurate and its results agree well with results reported in the literature, but the opposite of the transfer matrices method is significantly time consuming. Method of the transfer matrices is more suitable for a large number of calculations or tuning certain parameters. Models created in this bachelor's thesis can serve for the analyse of pathology of voice production, eventually for prediction of surgical procedures in the area of the vocal tract.
Influence of Glottal Shape of Human Vocal Fold on its Modal Characteristics
Zelinka, Martin ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The main goal of the bachelor thesis is to create a parametric model with a variable angle of the human vocal fold and to determine the first two frequencies of vocal fold oscillations for all angles from -40 ° to + 40 °. The result is supported by a review of the anatomy of the human vocal system, the creation and modification of the voice, and current models of the human vocal fold. The model used for this work is created in the 3D CAD Inventor model software. Modal analysis is solved in the computer program ANSYS Workbench, solved using finite element methods.
Creating a computational model of the human vocal tract
Freiwald, Michal ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
The research part of this bachelor’s thesis consists of a brief introduction to the human respiratory system and its subsidiary vocal subsystem along with a summary of basic phonation theories, voice disorders and published computational models of the human vocal tract. The experimental part engages in the making of the computational model itself, set to pronunciation of the vowel /a:/ in a woman vocal tract, on which, using finite element method, some of the basic acoustic analyses are performed, such as modal analysis or harmonic analysis. Calculated formants correspond with the values published in literature. Several different methods were analyzed while computing harmonic response. The most complex and the most time-consuming method, using infinite elements, also proved to be the most precise one. Thesis gives a decent comparison of the precision and complexity between the used methods.
Numerical simulation of of human voice propagation through the vocal tract and in the space around the body
Batelka, Jiří ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This master's thesis handles description of the source-filter theory of voice production, anatomy of larynx, possible approaches to voice production modelling and selected works using these approaches in first chapter. Brief description of selected quantities used in acoustics and model creation follows. Models of only the head and head with female and male torso are created, including mesh testing to determine suitable element size. Models created in this thesis focus on description of voice propagation primarily in front of body and on influence of torso on sound propagation. Inclusion of torso results in fluctuations in frequency domain in range from 1 000 Hz to 8 000 Hz, more pronounced near lower frquencies. In transverse plane the presence of torso manifests in lower SPL in front of mouth and higher SPL on the sides for several frequencies. Regions with decrease of SPL in front of mouth are coindicent with frequencies, where higher SPL on sides in comparision with direction in front of the mouth is evident. These observations are in agreement with other works. No significant differences were observed between models with different torsos in the transverse plane. Below the transverse plane differences between models with different torsos can be observed, for example for some frequencies decrease in SPL isn't observed in front of mouth in directivity diagrams for model with male torso.
Using of Transfer Matrix Method for Modal Characteristics of Vocal Tract
Meisner, Patrik ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The first part of the bachelor thesis describes anatomy of the vocal tract, voice creation and its modification. Some pathologies are listed at the end of the first part. The contents of second part are previously published computational models of the vocal tract followed by the method of transfer matrices for the Czech vowel [u:]. Modal analysis is performed by the transfer matrix method. The output are first three natural frequencies. Obtained frequencies are compared to values in the literature and to values calculated by the finite element method.

National Repository of Grey Literature : 139 records found   1 - 10nextend  jump to record:
See also: similar author names
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58 HÁJEK, Petr
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