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The importance of various habitats for fish in reservoirs
Šmejkal, Marek ; Vašek, Mojmír (referee) ; Prchalová, Marie (advisor)
Fish distribution in reservoirs is not homogeneous. Fish usually occur in upper parts of reservoirs on the longitudinal axis, where is also the greatest concentration of nutrients. Fish abundance and biomass as well as the trophy are declining towards the dam part. On the vertical axis, most fish occur above the thermocline, where temperature and concentration of dissolved oxygen reach the highest values. Fish community is changing also in time. Shortly after impoundment, the riverine species are dominating the community and later, generalist species prevail. Generally, we can distinguish pelagic and bentic habitats within the reservoir. There are species in reservoirs that occur almost strictly in pelagic habitat like asp and bleak and benthic species like ruffe and perch. Most species occur in both types of habitats (bream, roach, pikeperch, European catfish, white bream). Migrations between habitats occur on daily and on seasonal basis. On daily basis, we distinguish diel horizontal migration, in which fish shift between pelagic and benthic habitats. Diel vertical migration, when fish change depths, is not so significant in Czech reservoirs. Motivations for these diel migrations are food aviability, predation pressure and water temperature. Seasonal migrations comprise spawning migrations and winter...
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Ichthyological surveys of the Nýrsko and Karhov reservoirs and investigations of abundance, age composition and spawning dynamics of asp population in the Želivka Reservoir in 2015.
Vašek, Mojmír ; Soukalová, Kateřina ; Kočvara, Luboš ; Blabolil, Petr ; Baran, Roman ; Frouzová, Jaroslava ; Koliada, Ievgen ; Muška, Milan ; Šmejkal, Marek ; Draštík, Vladislav ; Kolařík, T. ; Prachař, Zdeněk ; Sajdlová, Zuzana ; Vebrová, L. ; Vejřík, Lukáš ; Kubečka, Jan
The species composition and the relative abundance and biomass of fish communities in the Nýrsko and Karhov reservoirs were evaluated by means of standardised multimesh gillnets. The spawning stock of asp in the Želivka Reservoir was individually marked using PIT tags and the density and behaviour of tagged fish at the main spawning grounds were examined through the whole spawning season. The total number of reproducing individuals in the asp population was estimated. The sex-specific length and weight growth rates of adult asp in the Želivka Reservoir were also calculated. \n\n
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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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Computational modelling of function of human vocal folds
Klíma, Jaromír ; Vašek, Martin (referee) ; Švancara, Pavel (advisor)
Master thesis deals with creating of the numerical model of the human vocal folds. Calculation algorithm is designed to include vocal chordsinteraction with the air flow. Analysis of the results achieved by the numerical simulations and calculations are focused on the pressure and velocity conditions in the areas under vocal folds, between vocal folds and above vocal folds. Movement and stress analysis of individual layers of vocal folds has been made. This analysis is limited only for physiological health vocal folds without pathology and disease. Modal analysis of structural and acoustic environment, backround research of vocal folds function and summary of some published overviews of numerical models is part of this work.
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Analysis of czech vowels to be generated aloud and in a whisper
Matug, Michal ; Vašek, Martin (referee) ; Mišun, Vojtěch (advisor)
The modal and spectral characteristic belongs among important human acoustic spaces of vocal tract. They occur at generating vowels and other acoustic aspects of human speech. We can observe the resonant phenomena of acoustic cavity of vocal tract in the human speech spectrum, primary however at vowels generation. However near vocal tract occurs series of frequency tops in the spectrum of vowels, which necessarily may not be resonant origin. That is why sometimes quite difficult assign is right frequency tops to resonant tops of acoustic cavity. It consist in operate of acoustic excitation of vocal tracts. The pronounced of vowels loudly and in a whisper has different excitation of vocal tract. At generating vowels loudly is excited by scheme of harmonic components outspread to fundamental frequency of glottis. At talking in a whisper is vocal tract excited by continuous spectrum generated by turbulent fluxion of exhaled flatus over glottis. We give a name "formant" to a frequency, at which happens to resonance of acoustic space. Aim of this work is analysis of Czech vowels formants generated loudly and in a whisper. Experimental metering of these formants was performed on human vocalic tract for all vowels. Further then on artificially created vocalic tracts for vowels A, I. Then were modal characteristics of vocal cavity for vowels A, I, tested by method of final elements with the help of computing program ANSYS. In this work were surveyed courses of acoustic pressures for individual formants, influence sizes vocal tract and influence of correct mouth opening on formants. Also has been effected computational simulation of harmonic excitation on tract by side of glottis.
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A new tool for improvement the quality of water ecosystems
Blabolil, Petr ; Říha, Milan ; Peterka, Jiří ; Prchalová, Marie ; Vašek, Mojmír ; Frouzová, Jaroslava ; Jůza, Tomáš ; Muška, Milan ; Tušer, Michal ; Draštík, Vladislav ; Ricard, Daniel ; Sajdlová, Zuzana ; Šmejkal, Marek ; Vejřík, Lukáš ; Matěna, Josef ; Borovec, Jakub ; Kubečka, Jan
The Czech multimetric fish based index (CZ-FBI) was developed recently. The aim of CZ-FBI is to assess the ecological potential of heavily modified and artificial water bodies and to detect ecosystems, particularly their specific components, in unsatisfactory conditions. This article describes steps of CZ-FBI development. Since the philosophy used, particular events presenting the results, to recent stage. CZ-FBI is a part of certified methodology of the Ministry of the Environment of the Czech Republic and the comparison with other assessment methodologies within a geographical intercalibration group is in process.
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