Number of found documents: 14761
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Neglected gravitational redshift in detections of gravitational waves
Křížek, Michal; Somer, L.
2018 - English
In 2016, the letter [1] about the first detection of gravitational waves was published. They were generated by two merging black holes that had approximately 36 and 29 Sun’s masses. However, the authors have not taken into account a large gravitational redshift of this binary system, which is a direct consequence of time dilation in a strong gravitational field. Thus the proposed masses are overestimated. In our paper we also give other arguments for this statement. Keywords: gravitational redshift; time dilatation; black holes; wavelets Available in digital repository of the ASCR
Neglected gravitational redshift in detections of gravitational waves

In 2016, the letter [1] about the first detection of gravitational waves was published. They were generated by two merging black holes that had approximately 36 and 29 Sun’s masses. However, the ...

Křížek, Michal; Somer, L.
Matematický ústav, 2018

How to down-weight observations in robust regression: A metalearning study
Kalina, Jan; Pitra, Zbyněk
2018 - English
Metalearning is becoming an increasingly important methodology for extracting knowledge from a data base of available training data sets to a new (independent) data set. The concept of metalearning is becoming popular in statistical learning and there is an increasing number of metalearning applications also in the analysis of economic data sets. Still, not much attention has been paid to its limitations and disadvantages. For this purpose, we use various linear regression estimators (including highly robust ones) over a set of 30 data sets with economic background and perform a metalearning study over them as well as over the same data sets after an artificial contamination. We focus on comparing the prediction performance of the least weighted squares estimator with various weighting schemes. A broader spectrum of classification methods is applied and a support vector machine turns out to yield the best results. While results of a leave-1-out cross validation are very different from results of autovalidation, we realize that metalearning is highly unstable and its results should be interpreted with care. We also focus on discussing all possible limitations of the metalearning methodology in general. Keywords: metalearning; robust statistics; linear regression; outliers Available at various institutes of the ASCR
How to down-weight observations in robust regression: A metalearning study

Metalearning is becoming an increasingly important methodology for extracting knowledge from a data base of available training data sets to a new (independent) data set. The concept of metalearning is ...

Kalina, Jan; Pitra, Zbyněk
Ústav informatiky, 2018

Dalekohledy typu Dall-Kirkham
Rail, Zdeněk; Ulrichová, Iva; Kuryshev, V.; Vápenka, David
2018 - Czech
Referát se zabývá optickými vadami dvojzrcadlových dalekohledů s elipsoidálními primárními a sférickými sekundárními zrcadly. Systém byl objeven na konci dvacátých let minulého století Horacem Dallem a Alanem Kirkhamem. Jeho optické prvky jsou snadno vyrobitelné a měřitelné. Tyto dalekohledy lze vybavit korektory a vytvořit z nich víceúčelové přístroje jak pro planetární pozorování, tak pro fotografování širokých zorných polí. Několik takových přístrojů bylo vyrobeno i v dílně Centra Toptec v Turnově. The paper deals with the optical aberrations of the two-mirror telescopes composed of the ellipsoidal primary and the spherical secondary mirrors. The system was discovered by Horace Dall and Alan Kirkham at the end of the Twenties of the 20th Century. Its optical elements are easy to manufacture and measure. These telescopes can be equipped by lens correctors and turned into multipurpose devices both for planetary observation and wide field photography. Several telescopes were manufactured in workshop of the Toptec Center in Turnov. Keywords: Two-mirror telescope; field corrector; optical aberrations; spherochromatic aberration; koma; astigmatism Available at various institutes of the ASCR
Dalekohledy typu Dall-Kirkham

Referát se zabývá optickými vadami dvojzrcadlových dalekohledů s elipsoidálními primárními a sférickými sekundárními zrcadly. Systém byl objeven na konci dvacátých let minulého století Horacem Dallem ...

Rail, Zdeněk; Ulrichová, Iva; Kuryshev, V.; Vápenka, David
Ústav fyziky plazmatu, 2018

Optický prvek 2G20 6x8x mm
Pintr, Pavel
2018 - Czech
Optický prvek 2G20 6x8 mm je určen pro proměnné dopravní značení (PDZ) v dopravě. Zajišťuje promíchání RGB diod na bílé světlo a jeho usměrnění do směru dle normy ČSN EN 12966 třídy B6. Optical element 2G20 6x8 mm is designed for a variable traffic marking. It assures the mixing of RGB diodes in white light and its direction in accordance with the specification ČSN EN 12966 class B6. Keywords: optical element; 2G20 6x8 mm; PDZ Available at various institutes of the ASCR
Optický prvek 2G20 6x8x mm

Optický prvek 2G20 6x8 mm je určen pro proměnné dopravní značení (PDZ) v dopravě. Zajišťuje promíchání RGB diod na bílé světlo a jeho usměrnění do směru dle normy ČSN EN 12966 třídy B6....

Pintr, Pavel
Ústav fyziky plazmatu, 2018

The Influence of Different Geometries of Human Vocal Tract Model on Resonant Frequencies
Valášek, Jan; Sváček, Petr; Horáček, Jaromír
2018 - English
This paper presents the transfer function approach in order to determine the acoustic resonant frequencies of a human vocal tract model. The transfer function is introduced here as an acoustic pressure ratio between input amplitude at glottis position and output amplitude at mouth opening given by the solution of Helmholtz equation. This equation is numerically approximated by finite element method. The influence of different boundary conditions are studied and also different locations of excitation and microphone. \nFour different vocal tract geometries motivated by vocal tract geometry for vowel [u:] are investigated. Its acoustic resonance frequencies in range 100 - 2500 Hz are computed and compared with published results.\nFurther, the transient acoustic computation with different acoustic analogies are performed. The frequency spectra of Lighthill analogy, acoustic wave equation and perturbed convective wave equation are compared, where the vocal tract model with best frequency agreement with published results was chosen. The dominant frequencies correspond with predicted frequencies of transfer function approach.\n Keywords: wave equation; transfer function; aeroacoustic analogies; perfectly matched layer Available at various institutes of the ASCR
The Influence of Different Geometries of Human Vocal Tract Model on Resonant Frequencies

This paper presents the transfer function approach in order to determine the acoustic resonant frequencies of a human vocal tract model. The transfer function is introduced here as an acoustic ...

Valášek, Jan; Sváček, Petr; Horáček, Jaromír
Ústav termomechaniky, 2018

Numerical investigation of acoustic characteristics of 3D human vocal tract model with nasal cavities
Vampola, T.; Štorkán, J.; Horáček, Jaromír; Radolf, Vojtěch
2018 - English
Acoustic resonance characteristics of 3D human vocal tract model without and with nasal and\nparanasal cavities were computed. Nasal cavities (NC) form the side branches of the human vocal tract and exhibit antiresonance and resonance properties which influence the produced voice quality. Developed FE models of acoustic spaces of nasal and vocal tract for vowel /a:/ are used to study the influence of (NC) on phonation. Acoustics frequency-modal characteristics are studied by modal analysis and numerical simulation of acoustic signals in time domain is performed by transient analysis of the FE models. Keywords: formant frequencies; modelling of phonation; biomechanics of voice Available at various institutes of the ASCR
Numerical investigation of acoustic characteristics of 3D human vocal tract model with nasal cavities

Acoustic resonance characteristics of 3D human vocal tract model without and with nasal and\nparanasal cavities were computed. Nasal cavities (NC) form the side branches of the human vocal tract and ...

Vampola, T.; Štorkán, J.; Horáček, Jaromír; Radolf, Vojtěch
Ústav termomechaniky, 2018

Comparison of Shenoy’s Expectation Operator with Probabilistic Transforms and Perez’ Barycenter
Jiroušek, R.; Kratochvíl, Václav
2018 - English
Shenoy’s paper published in this Proceedings of WUPES 2018 introduces an operator that gives instructions how to compute an expected value in the Dempster-Shafer theory of evidence. Up to now, there was no direct way to get the expected value of a utility function in D-S theory. If eeded, one had to find a probability mass function corresponding to the considered belief function, and then - using this probability mass function - to compute the classical probabilistic expectation. In this paper, we take four different approaches to defining probabilistic representatives of a belief function and compare which one yields to the best approximations of Shenoy’s expected values of various utility functions. The achieved results support our conjecture that there does not exist a probabilistic representative of a belief function that would yield the same expectations as the Shenoy’s new operator. Keywords: expected utility; Dempster-Shafer theory; Shenoy's operator Fulltext is available at external website.
Comparison of Shenoy’s Expectation Operator with Probabilistic Transforms and Perez’ Barycenter

Shenoy’s paper published in this Proceedings of WUPES 2018 introduces an operator that gives instructions how to compute an expected value in the Dempster-Shafer theory of evidence. Up to now, there ...

Jiroušek, R.; Kratochvíl, Václav
Ústav teorie informace a automatizace, 2018

Metodika měření poklesu rychlosti letících projektilů při průniku různými hmotami pomocí digitálního optomechanického zařízení
Šperl, Martin; Gajdoš, Lubomír; Wolf, Benjamin
2018 - Czech
Metodika popisuje postupy, použitá zařízení a software potřebná k měření průběhu poklesu rychlosti letících projektilů skrz různé sypké i pevné hmoty. Výhoda a unikátnost této metodiky spočívá v schopnosti měření útlumových charakteristik různých materiálů při impaktu projektilem o vysoké rychlosti. Metodika je založena na systému tenkých desek s optickým vláknem, které fungují při průletu střely jako světelné časové brány s definovanou vzájemnou roztečí. This methodology describes the procedures, the equipment and software used for measurement of the speed decrease of flying projectile through different bulk, silicate and solid masses. The advantage and uniqueness of this methodology consists in ability to measure the attenuation characteristics of various materials during the impact by high speed projectile. The methodology is based on a system of thin plates with optic fibers that function as a light-time gate with a defined pitch. Keywords: optical cable; projectile; speed measurement Available at various institutes of the ASCR
Metodika měření poklesu rychlosti letících projektilů při průniku různými hmotami pomocí digitálního optomechanického zařízení

Metodika popisuje postupy, použitá zařízení a software potřebná k měření průběhu poklesu rychlosti letících projektilů skrz různé sypké i pevné hmoty. Výhoda a unikátnost této metodiky spočívá v ...

Šperl, Martin; Gajdoš, Lubomír; Wolf, Benjamin
Ústav teoretické a aplikované mechaniky, 2018

Modelling of non-monotonous course of shear viscosity
Filip, Petr
2018 - English
A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting non-monotonous behaviour of flow curves this range (2-5) is no longer tenable and more additional parameters are required for a proper description of the flow curves. An 8-parameter model is presented and testified. Keywords: viscosity; flow curve; constitutive equation; empirical modelling Available at various institutes of the ASCR
Modelling of non-monotonous course of shear viscosity

A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting ...

Filip, Petr
Ústav pro hydrodynamiku, 2018

Redukce šumu z experimentálních časových řad
Chára, Zdeněk; Kysela, Bohuš
2018 - Czech
Příspěvek se zabývá redukcí šumu z časových řad. Pozornost je zaměřena především na časové řady získané metodou PIV. Metoda redukce šumu je testována pro PIV data získaná při měření rychlostních polí v míchané nádobě. Available at various institutes of the ASCR
Redukce šumu z experimentálních časových řad

Příspěvek se zabývá redukcí šumu z časových řad. Pozornost je zaměřena především na časové řady získané metodou PIV. Metoda redukce šumu je testována pro PIV data získaná při měření rychlostních polí ...

Chára, Zdeněk; Kysela, Bohuš
Ústav pro hydrodynamiku, 2018

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