National Repository of Grey Literature 40 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
Radolf, Vojtěch ; Horáček, Jaromír ; Košina, Jan
Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of the human vocal tract. The paper presents the studied acoustic-structural interaction of the vocal tract cavities with a dynamical system originated in vibration of the soft tissue. The experimental results are in qualitative agreement with the results of mathematical modelling. Compliant walls of acoustic cavities generate additional low frequency acoustical-mechanical resonances of the system and increase acoustic resonance frequencies.
Modelling and simulation of self-balanced vertical rigid rotors
Zapoměl, Jaroslav ; Kozánek, Jan ; Košina, Jan ; Cibulka, Jan
Unbalance of rotors of rotating machines is mostly caused by the manufacturing and assembling inaccuracies. In some cases it can be induced by the rotor operation or can be variable during the rotor running. In these cases the classical approach based on attaching the balancing weights to the rotor surface is not efficient. The technological solution is offered by application of a self-balancing device. This paper deals with its design, modelling, and investigation of its functionality in dependence of the rotor operation parameters.
Design of experiment for temperature dependence of rubber samples under torsional harmonic load
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Košina, Jan ; Cibulka, Jan
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a scheme of temperature measurement under torsional dynamic stress. The reason for these measurements is to determine the temperature dependence and sensitivity of the parameters of the thermal outputs.
Human vocal tract models with yielding walls – preliminary experimental results
Radolf, Vojtěch ; Horáček, Jaromír ; Košina, Jan
Yielding walls of acoustic cavities cause an additional low frequency acoustical – mechanical resonance of the system. This resonance changes also the higher acoustic resonance frequencies. Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of human vocal tract. The unique experimental set-up has been assembled to study in detail acoustic-structural interaction of the vocal tract cavities with a dynamical system originated in vibration of the soft tissue. The experimental results are in qualitative agreement with the results of mathematical modelling.
Analysis of muscle shortening and range of upper body movement and their relation to selected golf swing parameters in junior age players
Kosina, Jan ; Gryc, Tomáš (advisor) ; Hráský, Pavel (referee)
Title: Muscle tightness and range of motion analysis of selected upper body segments an its connection to selected parametres of experienced junior golf players swing. Objectives: The aim of this work is to assess muscle tightness, range of motion and golf swing kinematics of experienced junior golf players and to evaluate possible connections between muscle tightness, range of movement and golf swing kinematics Methods: Golf swing kinematics was observed by kinematic analyzer CODA Motion System. Selected parametres of golf swing were: shoulder rotation; pelvis rotation; X - factor; angle between shoulders and left arm. Parametres were measured in key moments of a goflf swing: end of backswing; impakt. Muscle tightness was measured by clinical test of muscle tightness according to Janda for selected muscles: m. triceps surae; m. iliopsoas; m. rectus femoris; m. tensor fascies latae; knee flexors; hip adductors; m. piriformis; m. quadratus lumborum; paravertebral muscles; m. pectoralis major; m. trapezius - upper part; m. levator scapulae and m. sternocleidomastoideus. Clinical test of range of motion according to Janda and standart two - arm goniometer was used for range of motion evaluation of selected body segments: hip joint - internal and external rotatio, flexion, extension; shoulder joint -...
Theoretical Description of Measured Signals for Blade Tip Timing Method and Inaccuracy Definition
Maturkanič, Dušan ; Procházka, Pavel ; Košina, Jan ; Voronova, Evgeniya ; Hodboď, Robert
The report describes the results of fluctuating speeds measurements for the blade tip timing method. The complications, occured during signal processing, lead to a detailed analysis of the recorded data. Thus, a theoretical description of the signal characteristics was elaborated. The measuremnts include four regimes in two different conditions. In connection with previous report, this report contains an assessment of a verification measurements with software upgrade.
Deformation energy of Yeoh hyperelastic model and constant hyperelastic proportional damping
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Košina, Jan ; Cibulka, Jan
The paper deals with a proposal of the dissipated energy of hard rubbers as a function of the deformation energy expressed by the Yeoh hyperelastic model. Then the deformation energy may be dependent only on the first invariant of deformation. Based on the experiment, a “hyperelastic proportional damping” (HPD) is proposed for hard rubbers under finite strains. It is analogical to the model of proportional damping in the elastic theory, i.e. the dissipated energy is proportional to the deformation energy multiplied by the frequency of dynamic harmonic loading. The Yeoh model is chosen since the deformation function is dependent only on the first strain invariant for a description of the simple shear of a surface cylinder. The constants are used to an enumeration of the deformation energy of the Yeoh model for the specific cases of tested rubbers. The coefficients of hyperelastic proportional damping are evaluated on the basis of experimental results,too.
Acoustic characteristics of 3D human vocal tract model with nasal cavities – preliminary experimental results
Radolf, Vojtěch ; Horáček, Jaromír ; Košina, Jan ; Vampola, T.
Acoustic resonance characteristics of 3D human vocal tract model with nasal and paranasal cavities were measured in three different ways: The excitation was realized by (1) self-oscillating vocal folds replica, (2) by a swept harmonic signal from an earphone placed instead of the vocal folds and (3) by a white noise signal from a loudspeaker located in front of the open mouth of the model. Resulting resonance frequencies are comparable for all excitation signals. These experiments were carried out to verify a complex mathematical model.
Experimental investigation of acoustic characteristics of 3D human vocal tract model with nasal cavities
Radolf, Vojtěch ; Horáček, Jaromír ; Košina, Jan ; Vampola, T.
The following experiments were carried out to be later used in the verification of a complex\nmathematical model of human voice production. Acoustic resonance characteristics of a 3D human voca tract model without and with nasal and paranasal cavities were measured in two different ways: The excitation was realized by (1) self-oscillating vocal folds replica and (2) by sine-tone sweeps from an earphone placed instead of the vocal folds. The resulting resonance and antiresonance frequencies were found to be comparable for both excitation signals.
Analysis of the turbine wheel model vibration
Voronova, Evgeniya ; Maturkanič, Dušan ; Procházka, Pavel ; Hodboď, Robert ; Košina, Jan
The paper describes the verification tests which were performed for 2000 rpm. Determined effects of vacuum on wheel vibration at 100 rpm and at \n500 rpm. Compare measurements at different speeds, with free oscillation or forced oscillation.\n

National Repository of Grey Literature : 40 records found   previous11 - 20nextend  jump to record:
See also: similar author names
2 KOŠINA, Jiří
10 Kosina, Jan
2 Kosina, Jiří
Interested in being notified about new results for this query?
Subscribe to the RSS feed.