National Repository of Grey Literature 398 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
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
Experimental and computer modelling study of glottal closing velocity during phonation
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Šidlof, P. ; Geneid, A. ; Laukkanen, A. M.
This preliminary study shows that the impact stress between the colliding vocal folds during phonation should not be evaluated from the maximum velocity of the glottal closing because the velocity of the closing diminishes just before the glottal closure. This phenomenon, which can be caused by a pressure cushion effect in the fast narrowing glottal gap, is demonstrated with measurements from high speed camera images recorded from human and on a physical laboratory model for vowel [u:] phonation and on a three-mass computer model employing a Hertz model of impact force. For a more detailed future study of this phenomenon a faster camera has to be used. \n
Plasma Heat Flux to Solid Structures in Tokamaks
Vondráček, Petr ; Horáček, Jan (advisor) ; Gunn, James P. (referee) ; Svoboda, Vojtěch (referee)
Plasma Heat Flux to Solid Structures in Tokamaks Petr Vondráček Energy and particle exhaust is the key issue for future fusion reactors based on magnetic plasma confinement, namely for tokamaks. Good understanding of processes controlling plasma heat fluxes impinging the first wall of tokamaks is of a main concern for fusion research. This doctoral thesis is focused on experimental investigation of plasma heat fluxes in different locations of the COMPASS tokamak. A new infrared thermography system was built for this purpose as a part of this PhD research. There are four main topics studied using the system. First of all, a narrow near-SOL heat flux channel with a very steep radial profile is characterised in HFS limited discharges. It is shown that the near-SOL heat flux decay length is consistent with the drift-based model of the SOL heat transport. Secondly, heat loading of leading edges of misaligned limiters is broadly studied. The optical approximation of the heat flux distribution around a poloidal leading edge is confirmed as a valid approach. Heat loading of a magnetically shadowed side of a toroidal limiter gap is observed experimentally for the first time confirming predictions of particle-in-cell code simulations. Thirdly, localised hot-spots caused by the impact of runaway electrons as well as...
Aerodynamic transfer of energy to vibrating vocal folds for different driving mechanisms
Valášek, J. ; Sváček, P. ; Horáček, Jaromír
This paper studies the mutual energy transfer between the fluid flow, described by incompressible Navier-Stokes equations, and the elastic body represented by vocal folds. The aerodynamic energy transfer function describes the amount and more importantly the sign of the energy exchange. It determines if the vocal fold vibrations are self-excited or prescribed.The energy transfer function is studied for three different driving mechanisms introduced by different inlet boundary conditions (BC). The most frequently used inlet BCs for incompressible model of fluid flow approximated by the finite element method are either Dirichlet BC giving the inlet velocity or do-nothing type of BC prescribing the pressure difference between the inlet and the outlet. Since the numerical simulations with both aforementioned BCs do not provide results observed experimentally the newly introduced BC based on the penalization approach seems as remedy. The numerical model consists of strongly coupled partitioned scheme based on the stabilized finite element method.\n\n
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
Seidl, Jakub ; Jiráková, Kateřina ; Adámek, Jiří ; Grover, Ondřej ; Horáček, Jan ; Hron, Martin ; Vondráček, Petr
We have identified two distinct types of turbulent fluctuations in COMPASS plasmas, the high-frequency edge oscillations and low-frequency SOL blobs. The transition region is localized in the near SOL, where both types spatially overlap and interact and the radial particle transport gradually transfers from high to low frequencies. Even though skewness of isat fluctuations is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL. This supports, together with turbulence spreading rate being positive in the near SOL but negative in the edge, the picture presented in [3] that most of the fluctuations that form a positive skewness in the edge region disappear around LCFS and new blobs are formed in the near SOL. Further, we cannot confirm the assumption that the blobs are generated randomly according to a Poisson process. Oscillations of all measured quantities, incl. radial particle flux, in the near SOL are peaked around ∼13 kHz. This seems to correspond to a poloidally rotating structure with a rather large poloidal wave-length ∼ 15 − 20 cm, that at least partly modulates blob generation. Nevertheless, we note that time separation of blobs becomes more random further in the SOL, possibly due to differences in their individual propagation. These observations hold for diverted plasmas, but the situation may be different in limited low-elongation plasmas where the radius of zero skewness was observed to be shifted significantly (several cm) inwards, compared to diverted configuration, and Gamma-like PDF is detected even inside the LCFS. Study of these plasmas is ongoing.
Diagnostic markers in patients in early stage of multiple sclerosis
Hynčicová, Eva ; Laczó, Jan (advisor) ; Horáček, Jiří (referee) ; Taláb, Radomír (referee)
The aims of the thesis were to assess diagnostic markers for monitoring of the disease progression in patients with clinically isolated syndrome (CIS) and laboratory markers of efficacy of the interferon beta (IFNß) therapy. This thesis includes 4 studies. The first study was focused on evaluation of cognitive impairment and its structural correlates in patients with CIS. Using comprehensive neuropsychological testing and brain magnetic resonance imaging (MRI) with volumetric analyses we found cognitive impairment in 18-37 % of CIS patients in almost all cognitive domains. Brain volume was reduced predominantly in fronto- temporal regions and the thalamus. Next, visuo-spatial impairment was associated with lower white matter volume in patients with CIS. The two other studies evaluated neuropsychiatric symptoms, life satisfaction, health-related quality of life and their mutual relationships. In addition, one of these two studies evaluated structural correlates of neuropsychiatric symptoms on brain MRI. Using a battery of specific questionnaires, we demonstrated depressive symptoms and anxiety in patients with CIS, lower life satisfaction, lower health-related quality of life and close mutual relationships. The quality of life was associated more with cognitive functioning than with disability in...
Application of Branch and Bound Approach to Parametric Interval Linear Systems
Szabó, Adam ; Horáček, Jaroslav (advisor) ; Rada, Miroslav (referee)
This work is focused on parametric interval linear systems. By using branch and bound method and various pruning conditions, we first obtained their solution and then described it more precisely with n-dimensional boxes. We were acquainted with the basic concepts of intervals and linear systems. Subsequently, we processed the boxes obtained by multiple methods to opti- mize their number. Part of the work is also a comparison of various pruning conditions on parametric systems with the different number of parameters. Finally, our algorithms were implemented into the Lime interval package with the possibility of simple visualization of the obtained solutions. 1
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
Seidl, Jakub ; Jiráková, Kateřina ; Adámek, Jiří ; Grover, Ondřej ; Horáček, Jan ; Hron, Martin ; Vondráček, Petr
In this work we study properties of turbulent structures in the scrape-off layer (SOL) and edge plasma of the COMPASS tokamak. Two distinct types of coherent oscillations are observed: a) broadband high frequency branch rotating in the electron diamagnetic direction, appearing mainly in the confined region but protruding also to the SOL b) low-frequency blobs rotating in an opposite poloidal direction, formed in the vicinity of the radius of zero electric field. The transition region is localized in the near SOL, where both types spatially overlap and interact and the radial particle transport gradually transfers from high to low frequencies. Even though skewness of fluctuations of the ion saturation current is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL and most of the fluctuations that form a positive skewness in the edge region disappear around LCFS.
Local sharpness prediction and image segmentation
Kopál, Jakub ; Šikudová, Elena (advisor) ; Horáček, Jan (referee)
The problem of automatic segmentation turned out to be complicated andtothisday, notcompletelysolved.Sinceitisacomplexproblem,thispaperis not- tryingtosolveitinitsmostgeneralform. Instead,itisfocusedonautomatic, bina- rypicturesegmentation,withtheoptiontochooseattributes, basedonwhich the seg- mentation should operate. Among these attributes are the focus and color of the picture. The results of the segmentation based on the assumption "focused object, blurry background" turned out to be very similar to the groundtruth in pictures, which fulfill this assumption. 1

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See also: similar author names
6 HORÁČEK, Jakub
6 Horáček, Jakub
13 Horáček, Jan
66 Horáček, Jaromír
6 Horáček, Jaroslav
23 Horáček, Jiří
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