National Repository of Grey Literature 106 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
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.
Napjatostně deformační analýza silničního mostu přes řeku Orlici
Adamec, Tomáš ; Hájek, Petr (referee) ; Fuis, Vladimír (advisor)
The main topic of this thesis is stress and strain analysis of road bridge over the river Orlice in Třebechovice pod Orebem. First point of the thesis is theoretical introduction to trusses and solid mechanics. Second point is describing the geometry of the bridge. Third point is creation of a 2D truss model, load of the model and description of computational algorithm. Fourth part is calculation and interpretation of results. Fifth point is verification of the fourth part. Sixth point is description of 3D truss calculation.
Influence of tissue changes in superficial lamina propria on production of Czech vowels
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J.
Superficial lamina propria (SLP) is a water-like vocal fold (VF) layer located directly under overlying epithelium. Its material properties affect VF motion and thus resulting spectrum of produced sound. Influence of stiffness and damping of the SLP on sound spectrum of Czech vowels is examined using a two-dimensional (2D) finite element (FE) model of a human phonation system. The model consists of the VF (structure model) connected with an idealized trachea and vocal tract (VT) (fluid models). Five VTs for all Czech vowels [a:], [e:], [i:], [o:] and [u:] were used and their geometry were based on MRI data. Fluid flow in the trachea and VT was modelled by unsteady viscous compressible Navier-Stokes equations. Such a formulation enabled numerical simulation of a fluid-structure-acoustic interaction (FSAI). Self-sustained oscillations of the VF were described by a momentum equation including large deformations and a homogeneous linear elastic model of material was used. Fluid and structure solvers exchange displacements and boundary forces in each iteration. During closed phase VFs are in contact and fluid flow is separated. We can observe that both the damping and the stiffness of the SLP substantially influence the amplitude and frequency of VFs vibration as well as the open time of the glottis.\n
Involvement of selected churches in České Budějovice in social work and conception of social work of the churches
HÁJEK, Petr
The aim of my own bachelor thesis is to outline the historical evolution (genesis) of charity activity of individual pre-selected churches on the basis of study of professional literature, to analyze the meaning and meaning of charity activity within the society and the particular church organization. To find out the current scope, meaning and perspectives of specific forms of social work in selected churches or churches. I want to achieve goals through qualitative and semi-structured interviews with communication partners. I will have prepared questions and, if a new and interesting topic is discovered, there will be room for him to devote himself fully to having space for him. From individual interviews, I expect a detailed insight into the issue of the influence of churches on social work in the city of České Budějovice, enriched by opinions of volunteer participants in the research. The identities of people and names of the organizations where the communication partners work will remain confidential. I have an agreement with them to keep anonymity. Records of conversations made on a mobile phone must be deleted by written request. The contribution of my bachelor thesis is the mapping of the content and forms of charity work of selected churches in historical development in connection with the needs of the given society on the one hand and the possibilities of the churches on the other. With the help of semi-structured interviews with selected church / church members, I want to find out what forms of the present Church are using in practical social work, how effective they are from their point of view and how they have a perspective in today's society at a given stage of social development and the status of the Church or churches.
Computational modelling of voice propagation around the human head using finite element method
Ryšavý, Antonín ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
In the first part of this master's thesis there is briefly presented the biomechanics of the human voice creation and an overview of the hitherto published computational models of the vocal tract and dissemination of the acoustic waves around the human head. The second part of the thesis deals with the creation of the computational model of a dissemination of the acoustic waves through vocal tract and further into a space around the head during the pronouncing of the Czech vowel /a:/. The vocal tract is excited by a harmonic signal in the place of vocal chords. On the surface of the vocal tract and the part of the head including hair and skin there is defined an acoustic absorption. The dissemination of the acoustic waves in the vocal tract, in the near field around the mouth, in the area around the head and in the points on the cheeks is detailed mapped. The dissemination of the acoustic waves is analyzed in the points where the speech microphones are placed. Acoustic pressure dependence on frequency, transmission functions between defined points and the acoustic pressure amplitudes depending on the distance from the mouth are obtained. In particular, the frequency distortion of the spectra is observed at the points indicated. Furthermore, the radiation impedance in the mouth area is evaluated. The results obtained are compared with the results of the hitherto published experimental measurements and can be used for the exact measurement of human voice or for the frequency correction of the microphones during the scann of the speech and sing placced in the analyzed points.
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.
Analysis of forces acting on the mandible during chewing
Thomková, Barbora ; Hájek, Petr (referee) ; Marcián, Petr (advisor)
The bachelor thesis deals with cranio-maxillo-facial biomechanics by analysing the force of the lower jaw during chewing. In the thesis, research study of literary sources dealing with the force of the lower jaw is carried out, from which the information obtained was used for subsequent analysis of the force effect on the lower jaw during chewing. The solution is made referring to computational modelling, analytical methods and also numerical by using FEM. The analytical solution was made on the assumption that the lower jaw is a rigid body and solved the magnitude of the contact forces in the bonds and the bite force that was considered at different positions using equations of equilibrium. The numerical solution was computed by using the ANSYS Workbench software. Two types of kinematic bonds (spherical and fixed support) in the condyle areas were solved and compared. The first type was identical with the analytical solution. Spherical bonds were prescribed at the place of the condyles. The second type of bonds was chosen on the basis of literature. Fixed support bonds were selected in both condyles. The results were compared for both approaches related to solution and the biting forces were compared with the experimentally determined values reported by the literature.
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.
Soustava těles s pasivním účinkem s brzdou
Genco, Ondřej ; Hájek, Petr (referee) ; Fuis, Vladimír (advisor)
This thesis deals with the solution of the body system using NNTP static theory model. The introductory part defines the basic magnitudes and concepts, describes the constraints and the types of passive effects. In the practical part, the influence of passive effects on different moving states in the particular system of the towed trolley is determined. Furthermore, two variants of mechanical friction brakes are designed and compared. The numerical values of unknown parameters are determined by solving the system of linear equations in Matlab.
Computational modeling of the influence of geometry and material model on vibration of human vocal folds
Michálek, Mojmír Cyril ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This theses focuses on a research of existing material and geometry models. Its effort is to gather and organize gathered information thus so that overview of geometries and material models was created. Furthermore an influence of Young’s modulus in tension of particular vocal fold layers was investigated using modal analysis. This was made for one three-dimensional (3D) and two two-dimensional (2D) geometry models.

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