Ne (2654)
Použitá omezení
(3)
Počet nalezených dokumentů:
2654
Publikováno od
do
Excitation of wheel blades by axial electromagnet at different regimes
Voronova, Evgeniya; Maturkanič, Dušan
2019 - anglický
The paper describes the natural frequency identification experiment and results of measuring of blade vibration characteristics excitate by one axial electromagnet at different regimes. The measurements were performed in the laboratory of the rotational laser vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Klíčová slova:
vibration; blade; magnet; frequency
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Excitation of wheel blades by axial electromagnet at different regimes
The paper describes the natural frequency identification experiment and results of measuring of blade vibration characteristics excitate by one axial electromagnet at different regimes. The ...
Příčina mechanického chvění těžních synchronních motorů Palašer a jeho odstranění
Pavelka, J.; Šimek, J.; Kobrle, P.; Kokeš, Petr
2019 - český
Příspěvek popisuje postup a výsledek analýzy mechanického rozkmitávání těžních strojů na dole Palašer v Ruské federaci. Jako příčina byla určena změna velikosti magnetického toku ve vzduchové mezeře vlivem drážkování statorů. Provedené simulace prokázaly možnost odstranění změny magnetického toku injektáží vhodných napětí statorového vinutí. V dalším je popsána realizace této injektáže pomocí přímovazební kompenzace střídavé složky momentu. Na závěr jsou uvedeny oscilografické záznamy před a po injektáži. The paper describes the procedure and the result of analysis of mechanical vibrations of mining machines at the Palašer mine in the Russian Federation. The cause of these vibrations was the change in the magnitude of the magnetic flux in the air gap. The simulations showed the possibility of eliminating these changes in\nmagnetic flux by injecting suitable voltages into the stator windings. The implementation of this injection is further described by torque variable component feed-direct compensation. Finally, oscillography records are presented before and after injection.
Klíčová slova:
mining machine; synchronous motor; indirect frequency converter; Maxwell force; resonant frequency; feed-direct compensation; injected voltage
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Příčina mechanického chvění těžních synchronních motorů Palašer a jeho odstranění
Příspěvek popisuje postup a výsledek analýzy mechanického rozkmitávání těžních strojů na dole Palašer v Ruské federaci. Jako příčina byla určena změna velikosti magnetického toku ve vzduchové mezeře ...
Utilization of Convolution Neural Network Based Road Detection in Mobile Robot Localization
Krejsa, Jiří; Věchet, Stanislav
2019 - anglický
Mobile robot on-road navigation requires fusion of both global and local sensory information with an emphasis on the road detection processing. The paper deals with the road detection based on convolution neural networks (CNN) using commonly available tools such as TensorFlow and Keras. The road is defined by its linear boundaries. Network output is formed by the road definition together with classification parameters and serves as a local sensor in Kalman filter based localization. CNN based road detection is currently capable to successfully detect about 90% of images.
Klíčová slova:
convolution neural network; localization; road detection
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Utilization of Convolution Neural Network Based Road Detection in Mobile Robot Localization
Mobile robot on-road navigation requires fusion of both global and local sensory information with an emphasis on the road detection processing. The paper deals with the road detection based on ...
Real-time diagnostics for ROS running systems based on probabilistic patterns identification
Věchet, Stanislav; Krejsa, Jiří
2019 - anglický
Autonomous mobile robots consists of various software modules to achieve given goal, including solving complex navigation tasks as localization, mapping or path planning. These tasks are highly dependent on the quality of data measured and gathered from hardware subsystems. Using Robot Operating System (ROS) as integration basis reduces the development effort and time to market. While ROS framework itself is considered as reliable and stable to run even soft real-time tasks, in case of any internal failures on data misreadings can be problematic to debug or even identify the problem for common user. Due to this unpleasant situations we develop a virtual assistant, internally represented as diagnostic expert system, to help users to identify and possibly fix the problem.
Klíčová slova:
diagnostic expert system; bayesian network; system diagnostic
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Real-time diagnostics for ROS running systems based on probabilistic patterns identification
Autonomous mobile robots consists of various software modules to achieve given goal, including solving complex navigation tasks as localization, mapping or path planning. These tasks are highly ...
Finite element implementation of creep constitutive model including transient effects
Gabriel, Dušan; Masák, Jan; Plešek, Jiří; Kloc, Luboš; Dymáček, Petr
2019 - anglický
A complex creep constitutive model including transient effects was implemented in the finite element code PMD (Package for Machine Design). The material model for P-91-type creep-resistant steel together with computer implementation was verified by means of uniaxial stress loadings. Testing bar was discretized by the finite element method (FEM) and loaded with uniaxial stresses and constant temperatures that were used to demonstrate the analytical solutions in original paper.
Klíčová slova:
creep; transient effects; FEM
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Finite element implementation of creep constitutive model including transient effects
A complex creep constitutive model including transient effects was implemented in the finite element code PMD (Package for Machine Design). The material model for P-91-type creep-resistant steel ...
Preliminary identification of damping properties of tonewood
Povolný, J.; Kozánek, Jan; Zapoměl, Jaroslav
2019 - anglický
Besides elasticity parameters, damping of the material is the crucial parameter of the function of a violin and also of other stringed instruments with a wooden soundboard. Assuming tonewood as an orthotropic linear elastic continuum, our aim is to contribute to hypothesis, that each orthotropic elastic constant has its appropriate loss factor - partial dampings. Dynamic experiments are based on the impulse excitation and the steady state harmonic response is calculated by Fourier transform of time-sampled measured signals (excitation and response). Frequency transfer function fitting identification method can determine complex modal and spectral eigen-parameters, mainly eigenfrequencies and eigendampings.
Klíčová slova:
vibrating thin plate; modal analysis; identification of eigenfrequencies and eigendampings; damping; violin
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Preliminary identification of damping properties of tonewood
Besides elasticity parameters, damping of the material is the crucial parameter of the function of a violin and also of other stringed instruments with a wooden soundboard. Assuming tonewood as an ...
Influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox
Šulc, Petr; Pešek, Luděk; Maturkanič, Dušan
2019 - anglický
This contribution is continuation of the work of above mentioned authors to whom this paper is dedicated. Their latest work dealt with numerical modelling of dynamics of planetary gearboxes with four satellites on flexible pins. They programmed the gear-box model in SIMULINK and now the model is an object of numerical investigations. This contribution describes the numerical model of the planetary gearbox. The numerical simulations are aimed to study an influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox.
Klíčová slova:
planetary gear box; dynamics; tooth stiffness influence
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox
This contribution is continuation of the work of above mentioned authors to whom this paper is dedicated. Their latest work dealt with numerical modelling of dynamics of planetary gearboxes with four ...
Odtržení proudu při nenávrhovém provozu lopatkových mříží
Šafařík, Pavel
2019 - český
V příspěvku jsou uvedeny dílčí výsledky experimentálního aerodynamického výzkumu lopatkových mříží při extrémních úhlech náběhu proudu. Ze zjednodušených představ o parametrech proudu v průtočné části turbostrojů jsou odvozeny podklady pro modelování nenávrhového provozu strojů. Simulace těchto podmínek v aerodynamickém tunelu umožnila pozorovat a měřit významné proudové struktury a jejich vývoj. V podmínkách extrémních úhlů náběhu proudu do lopatkových mříží je jedním z významných aerodynamických jevů rozsáhlé odtržení proudu. Výsledky výzkumu ukazují, jak při výskytu odtržení citelně narůstá součinitel ztráty kinetické energie. V oboru vysokých rychlostí proudu může nastat transsonická nestabilita. Nestacionární jevy byly pozorovány zvláště v podmínkách při extrémních úhlech náběhu odpovídajících provozu strojů značně odchýlenému od návrhového. Particular results from experimental aerodynamic investigation of blade cascades at extreme angle of incidence are presented. Data for modelling of off-design performance of machines are derived from simplified concepts on flow parameters in flow parts of turbomachines. Simulation of these complex conditions in the wind tunnel enables to observe and measure important flow structures and their development. An extensive flow separation is one of significant aerodynamic phenomena at extreme incidence angles of flow into blade cascades. Results of investigation prove considerable increase of coefficient kinetic energy losses at occurrence of flow separation. At high speed flows, transonic instability can set in. Unsteady phenomena are observed namely at extreme flow incidence conditions corresponding to considerable off-design performance of turbomachines.
Klíčová slova:
blade cascades; off-design performance; separation of flow; experimental modelling
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Odtržení proudu při nenávrhovém provozu lopatkových mříží
V příspěvku jsou uvedeny dílčí výsledky experimentálního aerodynamického výzkumu lopatkových mříží při extrémních úhlech náběhu proudu. Ze zjednodušených představ o parametrech proudu v průtočné části ...
Influence of tissue changes in superficial lamina propria on production of Czech vowels
Hájek, P.; Švancara, P.; Horáček, Jaromír; Švec, J.
2019 - anglický
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
Klíčová slova:
simulation of phonation; fluid-structure-acoustic interaction; czech vowels; finite element method; biomechanics of voice
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of tissue changes in superficial lamina propria on production of Czech vowels
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 ...
Experimental and computer modelling study of glottal closing velocity during phonation
Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Šidlof, P.; Geneid, A.; Laukkanen, A. M.
2019 - anglický
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
Klíčová slova:
impact stress; maximum glottal area delination rate (MADR); High speed imaging
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental and computer modelling study of glottal closing velocity during phonation
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 ...
NUŠL poskytuje centrální přístup k informacím o šedé literatuře vznikající v ČR v oblastech vědy, výzkumu a vzdělávání. Více informací o šedé literatuře a NUŠL najdete na webu služby.
Vaše náměty a připomínky posílejte na email nusl@techlib.cz
Provozovatel
Zahraniční báze