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Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
Radolf, Vojtěch; Horáček, Jaromír; Košina, Jan
2020 - English
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.
Keywords:
biomechanics of voice; vocal tract acoustics; acoustic-structural interaction.
Available at various institutes of the ASCR
Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
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 ...
Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder
Pech, Jan
2020 - English
This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution to the Navier-Stokes and Navier-Stokes-Fourier system. Reynolds numbers are considered in range 100-20000, ratio of cylinder-wall and upstream temperature is up to 1.5. Curves representing evolution of separation positions in time provide novel insight to vortex formation. Various regimes are recognized and some of them can be assigned to phenomena described formerly in experiment.
Keywords:
transition to turbulence; heated flow; cylinder flow; separation angle; Navier-Stokes- Fourier; spectral/hp element method
Fulltext is available at external website.
Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder
This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution ...
Comparison of power control method for B4 converter connected to unbalanced grid
Šimek, Petr; Valouch, Viktor
2020 - English
The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power control with a finite set of control values, the results obtained using a modified direct power control strategy, and the results obtained using a generalized predictive control are compared and discussed.\n
Keywords:
power control; B4 converter; unbalanced grid
Available at various institutes of the ASCR
Comparison of power control method for B4 converter connected to unbalanced grid
The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power ...
Dependence of signal strangth on the radial distance and different types of magnets
Procházka, Pavel; Voronova, Evgeniya; Maturkanič, Dušan
2020 - English
The paper describes dependence of signal strength on the radial distance between the sensor and the measured object and dependence of signal strength on the different types of magnets. The measurements were performed in the laboratory of the rotational laser vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Keywords:
vibration; diagnostics; sensor; laser; blade; turbine
Available at various institutes of the ASCR
Dependence of signal strangth on the radial distance and different types of magnets
The paper describes dependence of signal strength on the radial distance between the sensor and the measured object and dependence of signal strength on the different types of magnets. The ...
Inverse mass matrix for higher-order finite element method in linear free-vibration problems
Kolman, Radek; González, J.G.; Cimrman, Robert; Kopačka, Ján; Cho, S.S.; Park, B.G.
2020 - English
In the paper, we present adirect inverse mass matrix in the higher-orderfinite element method forsolid mechanics. The direct inverse mass matrix is sparse, has the same structure as the consistent mass matrixand preserves the total mass. The core of derivation of the semi-discrete mixed form is based on the Hamilton’s principle of leastaction. The cardinal issue is finding the relationship between discretized velocities and discretized linear momentum. Finally, the simple formula for the direct inversemass matrix is presented as well as thechoice of density-weighted dual shape functions for linear momentum with respect to the displacement shape functionwith achoice of the lumping mass method for obtaining the correct and positive definitive velocity-linear momentum operator. The application of Dirichlet boundaryconditions into the direct inversemass matrix forafloating system is achieved usingthe projection operator. The suggested methodology is tested on a free-vibration problem of heterogeneous bar for different ordersof shape functions.
Keywords:
higher-order finite element method; direct inverse mass matrix; consistent and lumped massmatrix; free vibration problem; heterogeneous bar
Available at various institutes of the ASCR
Inverse mass matrix for higher-order finite element method in linear free-vibration problems
In the paper, we present adirect inverse mass matrix in the higher-orderfinite element method forsolid mechanics. The direct inverse mass matrix is sparse, has the same structure as the ...
Anomalies detection in time-series data for the internal diagnostics of autonomous mobile robot
Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
2020 - English
Autonomous mobile robots are complex mechatronic machines which consists of numerous hardware and software modules working asynchronously to achieve desired behaviour. As there are many frameworks which helps to overcome the flat learning curve the problem of internal diagnostics arises. While users and developers are able to focus only on solving the high level problem algorithm or methods the internal states of the system is hidden. This helps to separate the users from solving hardware issues, which is helping until everything works properly. We present an algorithm which is able to detect anomalies in time based behaviour of the robot to improve the users confidence that the internal robot framework works correctly and as desired. The algorithm is based on probabilistic patterns detection based on Bayesian probabilistic theory.
Keywords:
anomalies detection; system diagnostic; robot operating system
Available at various institutes of the ASCR
Anomalies detection in time-series data for the internal diagnostics of autonomous mobile robot
Autonomous mobile robots are complex mechatronic machines which consists of numerous hardware and software modules working asynchronously to achieve desired behaviour. As there are many frameworks ...
Stress and Deformation of the Filter Press
Fuis, Vladimír; Kašuba, D.
2020 - English
The paper presents the stress and deformation analyses of the new design of the filter press made by Envites spol. s r. o. The analyses are solved in system ANSYS and there are nonlinear - due to the modelling by the contact elements and due to the material nonlinearities.
Keywords:
filter press; envites; finite element method; large deformation
Available at various institutes of the ASCR
Stress and Deformation of the Filter Press
The paper presents the stress and deformation analyses of the new design of the filter press made by Envites spol. s r. o. The analyses are solved in system ANSYS and there are nonlinear - due to the ...
On Harmonic Content of the Wake Behind a Circular Cylinder
Uruba, Václav; Procházka, Pavel P.
2020 - English
The wake behind cylinder of circular cross-section is subjected to detailed analysis from the point of view harmonic content. The basic, fundamental frequency could be linked to well-known Bénard-von Kámán vortex street, it is called Strouhal frequency very often. However higher harmonics of 2nd and 3rd order have been detected, as well as important inharmonic partials. The topologies of the velocity flow-field corresponding to the harmonic is to be shown.
Keywords:
circular cylinder; wake; Strouhal number; higher harmonics; oscillation pattern decomposition
Fulltext is available at external website.
On Harmonic Content of the Wake Behind a Circular Cylinder
The wake behind cylinder of circular cross-section is subjected to detailed analysis from the point of view harmonic content. The basic, fundamental frequency could be linked to well-known Bénard-von ...
POD-DEIM-based model order reduction for four-way coupled fluid-solid flows
Isoz, Martin; Šourek, M.
2020 - English
Proper orthogonal decomposition (POD) and discrete empirical interpolation method (DEIM) have become established tools for model order reduction in simulations of fluid flows. However, including moving solid bodies in the computational domain poses additional issues with respect to the fluid-solid coupling and to the solution of the movement of the solids. Still, it seems that if the hybrid ctitious domain-immersed boundary method is used to include the solids in the flow domain, POD-DEIM based approaches may be extended for four-way coupled particleladen flows. The present work focuses on the construction of POD-DEIM based reduced order models for the aforementioned flows.
Keywords:
CFD; POD; DEIM; HFDIB-DEM; OpenFOAM
Fulltext is available at external website.
POD-DEIM-based model order reduction for four-way coupled fluid-solid flows
Proper orthogonal decomposition (POD) and discrete empirical interpolation method (DEIM) have become established tools for model order reduction in simulations of fluid flows. However, including ...
An experimental investigation of yield surfaces anisotropies
Štefan, Jan; Parma, Slavomír; Marek, René; Plešek, Jiří; Feigenbaum, H. P.; Ciocanel, C.
2020 - English
This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular specimens to identify individual yield points of the material under arbitrary combinations of axial load and torque. A yield point is identified on the basis of a prescribed threshold for the effective plastic strain that is being continuously and fully automatically evaluated throughout the test. The experimental results generated with this tracing method are promising, leading to shapes of the yield surfaces conform with the von Mises criterion. The proposed methodology can effectively capture the YS shape.
Keywords:
experimental mechanics; yield surface; directional distortional hardening; metallic materials
Available at various institutes of the ASCR
An experimental investigation of yield surfaces anisotropies
This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular ...
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