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Computational Modelling of Self- oscillations of the Human Vocal Folds
Hájek, Petr ; Šidlof,, Petr (referee) ; Radolf, Vojtěch (referee) ; Švancara, Pavel (advisor)
The presented dissertation thesis deals with a simulation of the human phonation in terms of latest theories. Phonation is considered here as a bi-directional fluid-structure-acoustic interaction, where the interaction between all three physical domains occurs due to the unsteady viscous compressible Navier-Stokes equations. There is a solid knowledge background in the first part of the thesis. It concerns the latest concepts in computational modeling of the human phonation, the most important and recent theories about the human voice production and some key aspects of the human anatomy, physiology and pathology. Also voice assessment is discussed. The second part of the thesis describes an in-depth analysis of a phonation simulation in a planar computational model. The basic concepts proceed from algorithms developed in the Institute of Solid Mechanics, Mechatronics and Biomechanics. Created models are able to reproduce sounds of all Czech vowels and the most common evaluated parameters very close to physiological ranges. The simulated pathology, Reinke's edema, is demonstrated in order to explore its influence on the vowel sound. The third part focuses on modeling of phonation in a spatial computational model. All Czech vowels are simulated also here and compared to the planar model and to actual measurement. The spatial model serves as the starting point to modeling of a longitudinal pretension incorporated in the vocal folds. In the last part of the thesis, a modeling of the phonation with vocal folds pretension is investigated. Although the models are tuned to a rather soft phonation, the results are in agreement with the relevant physiologic phenomena. While the spatial model is highly computationally expensive, a hybrid planar model with pretension is proposed. A special attention is paid to the analysis of self-sustained oscillation of the vocal folds. It is shown, the planar model cannot reproduce such kind of oscillation in the actual version, albeit time of oscillation was considerably extended. On the other hand, oscillation of the spatial vocal folds are stabilized without effects accompanying subduing of oscillation. It can be supposed that the spatial model is able to reproduce self-sustained oscillation as a basic principle present during the human phonation.
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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.
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Stress-strain analysis of dental implant inserted in maxilla
Dušková, Tereza ; Hájek, Petr (referee) ; Marcián, Petr (advisor)
Variety of problems can appear when introducing dental implants, especially to in the maxilla. Biggest problems are caused by insufficient quality and volume of the bone tissue of the alveolar process. This thesis focuses on stress-strain analysis of an implant introduced in the maxilla. Mechanical interaction between the implant and bone tissue is solved using computational modelling with the finite element method. From analysis of results, it was discovered that deformation and tension of the implant are influenced by the direction of the load, osseointegration and thickness of the cortical bone tissue. In the anterior region, it is necessary to work with other types of load than axial.
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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.
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Computational modelling of stress and strain of the human vocal folds during setting up to phonation position
Sádovská, Terézia ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This master‘s thesis deals with computational modelling of human vocal folds in phonation position using finite element method. There are described larynx anatomy, voice generation theories and overview of so far published computational models of vocal folds. Next part of the paper deals with a redesign of vocal folds and soft tissues‘ geometry, creation of finite element mesh and implementation of active stress in thyroarytenoid muscle. The problem was solved using Ansys 19.2 software. Computation of stress and deformation of soft tissues in phonation position has been made for 7 variations with different combination of active cartilages and muscles. Lastly, there was evaluated an effect of different cartilages and active muscle stress to final stress and deformation of soft tissues of vocal folds.
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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.
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Stress-strain analysis of internal plate fixator of distal radius fracture
Hussliková, Veronika ; Hájek, Petr (referee) ; Marcián, Petr (advisor)
Distal radius fractures are one of the most common fractures. In case of a complicated fracture, it is necessary to proceed with surgical treatment using an internal plate fixator. The aim of this thesis was to perform a stress-strain analysis of an internal plate fixator attached to the distal radius using bone screws. Computational modeling using finite element method was used to assess the mechanical interactions among the individual elements of this system. The stress-strain analysis was performed for three different types of fixation in geometry models including a distal radius fracture and a healed distal radius and for three different types of loads. In the evaluation of the results, the influence of the type of load and the influence of the healing of the bone tissue were assessed. For the bending load, which was the most critical, the yield strength was not exceeded in the plate or in the bone screws, and therefore irreversible plastic deformation of the material did not occur.
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Smart Materials for Medical Applications
Kaplán, Martin ; Hájek, Petr (referee) ; Florian, Zdeněk (advisor)
This thesis describes materials which react to external stimuli. These materials are know as Smart materials. The thesis provides an overview of these materials and their use in the field of medicine. A lot of attentions is paid to Nitinol as the most significant representative of Smart materials. The thesis brings a simulation of using shape memory effect of Nitinol staple for bone fracture fixation. This simulation use the method of finite elements for solving and it is done in ANSYS modeling software. The simulation has only demonstrational purpose.
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