National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Effect of synovial fluid composition and surface topography modification on lubrication of joint replacements
Hekrle, Pavel ; Vampola, Tomáš (referee) ; Vrbka, Martin (advisor)
The main objective of this diploma thesis is to determine the influence of synovial fluid compodition and the influence of surface microtextures on lubrication of hip join replacements. For all experiments, hip joint simulator based on the pendulum principle was utilized. Metal heads (CoCrMo) manufactured by B Braun company and and tailor made acetabular cups from optical glass were used as contact couples. Acetabulum dimensions were fabricated according to dimensions of real implants. Experiments with surface microtextures simulated walking cycle for 210 s and development of lubrication film over time was observed.Results have shown that all types of tested structures improved lubrication of contact area, where the best results were obtained for square and triangle shapes respectively. Second set of experiments was based on the fact, that the composition of synovial fluid of healthy people differs from the composition of patients with various stages of osteoarthritis. Therefore, experiments with different model fluids were compared, which in their composition correspond to different groups of patients. For the model fluid that corresponds to the largest number of cases, experiments with individual components and combinations thereof were subsequently performed to provide a more detailed description of how these components affect the film-forming mechanism. The results show, that a change in fluid composition of patients with osteoarthritis can have a major negative effect on fluid formation process within the pair.
Compensatory Vocal Folds for Source Voice Generation: Computational Modeling of Vocal Folds Function
Matug, Michal ; Vampola, Tomáš (referee) ; Horáček, Jaromír (referee) ; Švancara, Pavel (advisor)
This doctoral thesis focuses on computational modelling of human vocal folds and vocal tract functions using finite element method (FEM). Human voice is crucial in human communication. Therefore one of the main targets of current medicine is creation of artificial vocal folds, which would substitute the original vocal folds. The computational modelling can be used to understand principles of voice production, determination of parameters that the artificial vocal folds have to meet and verification of their functionality. First part of this thesis focuses on modelling of human voice creation by whisper. Influence of intraglottal gap on eigenvalues distribution for individual vowels was analysed using FEM vocal tract and trachea model. Further there is presented two-dimensional (2D) finite element model of the flow-induced self-oscillation of the human vocal folds in interaction with acoustic spaces of the vocal tract. The 2D vocal tract model was created on the basis of converting the data from magnetic resonance images (MRI). Explicit coupling scheme with separated solvers for structure and fluid domain was used for modelling of the fluid-structure interaction. Created computational model comprises: large deformations of the vocal folds tissue, contact between vocal folds, fluid-structure interaction, morphing the fluid mesh according to the vocal-fold motion (Arbitrary Lagrangian-Eulerian approach), unsteady viscous compressible or incompressible airflow described by the Navier-Stokes equations and airflow separation during glottis closure. This model is used to analyse the influence of stiffness and damping changes in individual vocal fold tissue layers (in particular in superficial lamina propria). Part of this computational analysis is also comparison of vocal folds behaviour for compressible and incompressible flow model. Videokymograms (VKG) are subsequently created from obtained results of FEM calculations which enable to compare individual variants between themselves and with motion of real human vocal folds. In next part of this thesis is presented three-dimensional (3D) finite element model of the flow-induced self-oscillation of the human vocal folds. This 3D model was created from a previous 2D model by extrude to the third direction. Using this model was again compared influence of compressible and incompressible flow model on vocal folds motion and generated sound by using videokymograms and acoustic spectra. The last part of this thesis focuses on the possibility to replace missing natural source voice in form reed-based element. Behaviour of reed-based element was analysed using computational modelling and using measurements on experimental physical model. The physical model enables changes in setting gap between reed and reed stop and performing acoustical and optical measurements.
Artificial Vocal Folds for Source Voice Generation
Vašek, Martin ; Vampola, Tomáš (referee) ; Kamenický, Ján (referee) ; Mišun, Vojtěch (advisor)
The first part of this work focuses on ways to replace missing source voice in case of patients after total laryngectomy. The commonly used methods of voice rehabilitation are mentioned. Simple computational models are used to explore several principles of generating artificial source voice. Based on the knowledge of how a healthy human voice is generated, one of the ways to generate artificial source voice was chosen – a reed-based element in the configuration (-, +). The function of the reed-based element is based on a periodic bending of the reed and in the airflow cutoff created by this motion. The (-,+) configuration of the reed-based element causes a different behaviour, when compared to healthy vocal folds, important is, however, whether the generated acoustic signal has the right spectral characteristics, which enable the generation of voiced vowels of the human speech. Both experimental and computational models are used to study the behaviour of the reed-based element. The design of the experimental model is based on the preliminary experiments with simple reed-based elements, which were carried out at the beginning of my studies. The new experimental model is designed in such a way, that it enables changes to the reed geometry and its position towards the reed stop. The measurements carried out on the experimental model are mainly acoustical (measurements of the generated acoustical signal), but optical measurements of the reed´s movement and position are possible and used as well. Because of the nature of the reed-based element´s behavior, the fluid structure interaction must be taken into consideration in the computational model. A two-way model of fluid structure interaction is used between the fluid part of the computational model and the structural one. A partitioned solution is used to solve the fluid-structure interaction. The effect of specific input parameters on the function of both models (experimental and computational) is monitored. The influences of input parameters on the basic frequency of the generated signal (source voice), on the stability of the function and on other important characteristics are evaluated. The final chapters focus on the design of voice prosthesis in general. Some specific issues, which need to be solved when designing voice prosthesis, are highlighted.

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15 Vampola, T.
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