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Modeling of airflow through the human vocal tract during voice production
Kučera, Marek ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This bachelor's thesis deals with computational modeling of air flow through the human vocal tract during voice production. In the theoretical part, the anatomy of the respiratory system, the function of the human vocal folds, the biomechanics of the human voice and the flow theory are briefly described. Subsequently, an overview of approaches to computational modeling of voice production is presented. The practical part describes the creation of 2D models of the trachea and vocal tract with different settings of the vocal folds. A suitable mesh of finite volumes was created. Stationary flow was solved and analyzed in the ANSYS Fluent program. A suitable time step was determined for non-stationary flow and the results were subsequently analyzed. At the end, the non-stationary flow with the prescribed movement of the vocal folds is solved.
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Analysis of Modal Shapes and Natural Frequencies of Real-Shaped Vocal Fold
Horčic, Václav ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
This bachelor's thesis deals with the modal analysis of a model based on a 3D scan of the human vocal cords. This is a model solved by the finite element method, where the value of the first natural frequency roughly corresponds to the value of the fundamental frequency of female vocal folds. The research part of the thesis is devoted to an overview of finite element models of the geometry of the vocal cords, which is followed by a brief description of the anatomy and physiology of the human speech system together with the theory of the formation of the human voice. The finite element model is created using a 3D scan of the vocal folds in the commercial program ANSYS Workbench, in which it is solved by the finite element method.
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A review study of abutments in dental implantology
Palkovič, Patrik ; Hájek, Petr (referee) ; Thomková, Barbora (advisor)
This bachelor thesis deals with the analysis of the influence of different types of abutments on the stress-strain states of the mandible with an inserted dental implant. The thesis focuses on two types of abutments, namely straight abutments and angled abutments. Furthermore, the thesis discusses the influence of bone tissue quality on the stress-strain states in the mandible with an inserted dental implant. Computational modelling using the finite element method (FEM) was used to assess the stress-strain states, specifically ANSYS Workbench software was used. Computational models of the mandible with dental implant were created with three abutment variations with different angles. Additionally, stress-strain states were determined for different bone tissue qualities. Analysis of the results showed that angled abutments lead to greater strain of the bone tissue and greater implant stresses compared to straight abutments. The influence of bone tissue quality on the stress-strain states was significant in terms of bone tissue strain. Bone tissue quality did not significantly affect the stress on the implant.
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Modeling of Interaction between Lumped Element Model of the Vocal Fold and Fluid Flow
Řeřuchová, Ivana ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The thesis belongs to the branch of biomechanics of human voice and bioacoustics. It deals with the modelling of the vocal cords in interaction with the air flow and the vocal tract. Specifically, it involves two-mass and three-mass body-cover models. The interaction is solved using the finite-difference method, the vocal cord oscillation is represented by the equations of motion, the flow is simulated by Bernoulli's equation, and the acoustics is implemented using an electro-acoustic analogy as an acoustic circuit. The thesis also includes the basics of laryngeal anatomy, the physiology of the human voice, and a review of previously published material models of the vocal cords, i.e., models with a low number of degrees of freedom.
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Mechanical analysis of the front wipers mechanism of a Škoda car
Košinová, Laura ; Hájek, Petr (referee) ; Fuis, Vladimír (advisor)
This bachelor’s thesis deals with the mechanical analysis of the front wipers mechanism of a Škoda Felicia and Škoda Octavia cars. Firstly, the explanation of necessary terms of mechanics needed for the solution to the problem is provided, followed by a brief history of windshield wipers. The aim of the practical part was to find the driving moment and contact forces in the links and further analyze the behavior of the mechanism after overcoming the static stability limit. The creation of mechanism models in Solidworks was also included. The unknown parameters were determined using Matlab. The dynamic analysis was solved numerically using Ansys software.
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Modal Analysis of the Classical Guitar Bridge
Ondečko, Adam ; Votava, Tomáš (referee) ; Hájek, Petr (advisor)
The bachelor thesis deals with the determination of the natural freqvencies and mode shapes of a classical guitar bridge and their influence on the function of the guitar. The function of the guitar is described by the oscillations of the individual oscillators: the strings, the air in the cavity of the guitar, the top and bottom plates, and then by their oscilation as a system. In the bachelor's thesis the roles of the guitar bridge are discussed and the different types of guitar bridges are presented. In the thesis, the guitar bridge is considered as a separate component and as part of the guitar's top plate. The mode shapes and natural freqvencies are obtained using modal analysis with the use of computational modelling using the finite element method. The natural freqvencies are determined for 2 types of guitar bridges, the effect of the guitar bridge on the mode shapes and natural freqvencies of the guitar top plate is further evaluated. The natural freqvencies of the classical guitar bridge affect the tone quality and the duration of oscilation of the string. Tones close to the natural freqvencies of the guitar bridge sound louder and last shorter amount of time than the others. The guitar bridge changes the stiffness of the top plate and thus influences its mode shapes and freqvencies.
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Determination of Material Properties of Silicone Used for Experimental Modeling of the Human Vocal Folds
Podkalský, Stanislav ; Hrubanová, Anna (referee) ; Hájek, Petr (advisor)
The presented bachelor thesis focuses on a comprehensive analysis of the material properties of silicone models used in experimental vocal fold models. This thesis includes analysis of the literature in which the authors have addressed this issue and appropriately follows up with an own experiment in the form of a tensile test resulting in constitutive models for the accurate determination of the Young's modulus for arbitrary elongation. Models such as the Neo-Hooke model will be used for the hyperelastic nature of the material. At the same time, this work focuses on the statistical treatment of phenomena acting on the silicone material such as material thinning and aging.
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A review study of standards for strength analysis of total knee arthroplasty
Štaffová, Markéta ; Hájek, Petr (referee) ; Marcián, Petr (advisor)
This bachelor thesis is focused on the study of standards for strain and stress analysis of TKR (total knee replacement) - especially of the femoral component. In the first part of the thesis is a research of the knee replacement. This part beggins with anatomy, movements and loading of the knee joint, and continues to medical indications for replacement, the various parts and types of knee arthroplasty, and the materials used in TKR, including the durability of the knee arthroplasty. The next section of the thesis describes the standards, that are used for the knee arthroplasty, detailing standards for pre-clinical evaluation and standards for testing components of knee replacement using computer software with FEA. Finally, the thesis presents the application of the standard for femoral component testing using FEA. This standard is used to the comparison of two femoral components and their strain-stress analysis.
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Harmonic Analysis of the Double Bass Bridge
Čalkovský, Lukáš ; Votava, Tomáš (referee) ; Hájek, Petr (advisor)
This bachelor's thesis focuses on the research of string instruments and their mechanical properties. It explores the double bass bridge and its importance. On a model created in the SolidWorks program, modal analysis was performed using the ANSYS software, which determined the frequencies and shapes of the individual modes. Harmonic analysis was also performed and analysed. Part of the investigation was to analyze the possible cause of the formation of so-called wolf tones. The double bass bridge does not exhibit any special characteristics in the double bass range, so it is not the cause of this anomaly.
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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.
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