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Rosný bod spalin: teoretické modelování a předběžné měření
Krejčí, A. Petr ; Hrubý, Jan ; Ždímal, V. ; Trávníček, Zdeněk
Based on industrial needs, the dew point temperature of flue gases is re-examined, both theoretically and experimentally, with mixture of sulphuric acid and water vapors as a flue gas model. This work is motivated by inconsistency and unsufficient accuracy of previous works, which differ significantly in data on sulphuric acid saturation pressure. Experimental setup based on the Laminar co-flow tube is used to express saturation pressure of sulphuric acid via measurements of binary homogeneous nucleation rate.
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Energeticky konjugované míry napětí a deformace v mechanice kontinua
Hrubý, Zbyněk ; Plešek, Jiří
The energy conjugate measures of stress and strain enter any constitutive relation for the material behaviour description. There are many strain measures in common use, several of them discussed in the text. The main aim of the contribution is to focus on the derivation of a general energy conjugate stress tensor corresponding with a general Lagrangean strain tensor.
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Vazba kmitajícího systému a zdroje energie
Půst, Ladislav
Majority of publications on mechanical vibrations are based on the assumption that the external excitation is produced by an ideal source of power with prescribed frequency. But in reality, the excitation sources are non-ideal with limited power, limited inertia and their frequency fluctuates according the instantaneous state of oscillating system. The paper presents on overview of systems and results gained during the several dozens of years on this interaction problem. The most characteristic properties of systems excited by source of limited power and limited inertia are variation of revolution, distortion of harmonic motion, instability and non-uniform passage through resonance zone.
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Modelování vibračních vlastností lidských hlasivek
Vampola, T. ; Horáček, Jaromír ; Klepáček, I.
A 3D finite element model of the human larynx including the vocal folds was developed. The model enables to take into account phonation position (tinsion and adduction) of the vocal folds by positioning of the arythenoid and thyroid cartilages. Anisotropic properties of the three layers of the vocal fold living tissue (epitel, ligament and muscle) are modelled respecting the material nonlinearities with increasing prolongation of the tissue in longitudinal direction. The motion of the vocal folds is numerically simulated for a prescribed subglottal pressure loading the vocal folds by a periodic function in the time domain. the generated motion of the vocal folds seems to be qualitatively similar to a vibration mode known from clinical measurements.
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Výpočet dynamických vlastností aerostatických ložisek
Skarolek, A. ; Kozánek, Jan
This contribution deals with computation of stiffness and damping coefficients of aerostatic bearings. Model of bearings is based on Reynolds equation for compressible medium supplemented by descrition of mass flow through feeding system. Time-series of displacements and internal forces are obtained by numerical solution. Linear stiffness and damping coefficients are obtained by means of least squares regression.
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Možnosti ladění a optimalizace akustických rezonančních vlastností vokálního traktu člověka
Radolf, Vojtěch ; Vampola, T.
The paper deals with optimization process finding such geometrical form of acoustical cavities of the human supraglottal spaces which leads to excitation of predefined acousic resonance, especially between a domain of the third and the fifth formant. The problem is solved by the transfer matrix method using conic acoustic elements for the vocal tract modelling and numerical method of searching a minimum of a goal function of several variables. The results should help to obtain a physical background for voice rehabilitation, for teaching of opera singers at musical facuoties and for better understanding of biomechanics of voice production.
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Pohyb rotoru uloženého v aerodynamických ložiskách
Půst, Ladislav ; Šimek, J. ; Kozánek, Jan
The tilting pad bearings are very often applied in high speed rotating machines. The exact solution of bearing characteristics, including the motion of tilting pads, is very difficult and not yet completely elaborated. an approximate method for calculattion of rigid rotor motion with large amplitudes limited only by the bearing clearance is presented. The models of stiffness and damping forces valid for the entire area of journal motion in the aerodynamic bearingś clearance are based on the transformation of linear stiffness and damping characteristics calculated for two cases of stationary state and extended to the whole bearing field by using the correction function fc(r). Differential equations of motion of rigid rotor supported on two aerodynamic bearings with proposed nonlinear characteristics are numerically solved and resulting time histories of journal motion, their plane trajectories will be presented.
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Výpočtové modelování vztahů mezi časovou změnou glotální plochy a úrovní vyzařovaného zvuku z vibrujících hlasivek
Horáček, Jaromír ; Laukkanen, A. M. ; Šidlof, Petr
The radiated sound pressure level (SPL) during phonation is known to be mainly regulated by lung pressure and glottal resistance (adduction), at the glottal level. Few results of glottal area variation in SPL control have been presented. The present study investigated the interrelations between sound pressure level at the glottis (SPL source) and lung pressure, maximum amplitude of vocal fold vibration and maximum glottal area declinatin rate for different fundamental frequencies and prephonatory glottal widths. These data were generated by an aeroelastic model used for numerical simmulations of vocal fold self-oscillations including the vocal folds collisions. The relations of SPL source to the parameters studied were in general non-linear.
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