Number of found documents: 213
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Variace geoidu detekované z družicové mise GRACE
Kostelecký, J.; Bezděk, Aleš; Klokočník, Jaroslav
2014 - Czech
Časově proměnné gravitační pole, získané z pozorování mise GRACE od roku 2002, je v tomto příspěvku založené na transformaci měsíčních gravitačních polích na výšku geoidu. Ukážeme gravitační změny působené globálním hydrologickým cyklem a hydrologií na pevninách. Time variability of the gravity field, provided by the GRACE mission since 2002, presented here is based on the transformation of monthly gravity field models to the geoid. We show the changes caused by the global water cycle and land hydrology. Keywords: GRACE mission; geoid; gravimetry Available at various institutes of the ASCR
Variace geoidu detekované z družicové mise GRACE

Časově proměnné gravitační pole, získané z pozorování mise GRACE od roku 2002, je v tomto příspěvku založené na transformaci měsíčních gravitačních polích na výšku geoidu. Ukážeme gravitační změny ...

Kostelecký, J.; Bezděk, Aleš; Klokočník, Jaroslav
Astronomický ústav, 2014

Revealing general relativity effects from accretion events near a supermassive black hole
Karas, Vladimír; Dovčiak, Michal; Eckart, A.; Kunneriath, Devaky; Zamaninasab, M.
2014 - English
The authors discuss the general relativity effects acting on the radiationmsignal from the inner accretion flow. Keywords: black holes; galactic center; relativity Available at various institutes of the ASCR
Revealing general relativity effects from accretion events near a supermassive black hole

The authors discuss the general relativity effects acting on the radiationmsignal from the inner accretion flow.

Karas, Vladimír; Dovčiak, Michal; Eckart, A.; Kunneriath, Devaky; Zamaninasab, M.
Astronomický ústav, 2014

Application of a sympletic integrator in a non-integrable relativistic system
Kopáček, Ondřej; Karas, Vladimír; Kovář, J.; Stuchlík, Z.
2014 - English
The authors present a detailed comparison of several integration schemes applied to the dynamic system consisting of a charged particle on the Kerr background endowed with the axisymmetric electromagnetic test field. Keywords: black hole physics; test particle dynamics; magnetic fields Available at various institutes of the ASCR
Application of a sympletic integrator in a non-integrable relativistic system

The authors present a detailed comparison of several integration schemes applied to the dynamic system consisting of a charged particle on the Kerr background endowed with the axisymmetric ...

Kopáček, Ondřej; Karas, Vladimír; Kovář, J.; Stuchlík, Z.
Astronomický ústav, 2014

Compton scattering in strong gravity
Bursa, Michal; Adámek, K.
2014 - English
The authors present new numerical code for radiation transport in strong gravity regime that includes arbitrary emission and absorption mechanisms and also electron scattering. Keywords: radiation transport; relativity; Compton scattering Available at various institutes of the ASCR
Compton scattering in strong gravity

The authors present new numerical code for radiation transport in strong gravity regime that includes arbitrary emission and absorption mechanisms and also electron scattering.

Bursa, Michal; Adámek, K.
Astronomický ústav, 2014

Upcoming Features of SPLAT-VO in Astroinformatics
Šaloun, P.; Andrešič, D.; Škoda, Petr; Zelinka, I.
2013 - English
During last decade was developed fully automatized (robotic) class of telescopes, that produce huge amount of data per each night. Amount of recorded data is usually in the scale of petabytes. To process properly all data and select an important events it is needed to use sophisticated software methods and algorithms. It caused an appearance of a new field of science - astroinformatics. In this paper we introduce a small part of our contribution to the astroinformatics field - a specialized software SPLAT-VO. It is used for processing and visualization of astrophysical data generated by nonlinear, complex or even chaotic processes in the space. Overview of new features so far prepared for new version of SPLAT-VO. The overview is focused on enhancements of user experience, work with SAMP protocol and other interoperability that improves work with global list of spectra, plot window and analysis menu. Keywords: SPLAT-VO; spectrum analysis; SAMP Available at various institutes of the ASCR
Upcoming Features of SPLAT-VO in Astroinformatics

During last decade was developed fully automatized (robotic) class of telescopes, that produce huge amount of data per each night. Amount of recorded data is usually in the scale of petabytes. To ...

Šaloun, P.; Andrešič, D.; Škoda, Petr; Zelinka, I.
Astronomický ústav, 2013

Classification on Be stars using feature extraction based on discrete wavelet transform
Bromová, P.; Bařina, D.; Škoda, Petr; Vážný, Jaroslav; Zendulka, J.
2013 - English
We describe the initial experiments in the field of automated classification of spectal line profiles of emission line stars. Keywords: Be star; stellar spectrum; feature extraction Available at various institutes of the ASCR
Classification on Be stars using feature extraction based on discrete wavelet transform

We describe the initial experiments in the field of automated classification of spectal line profiles of emission line stars.

Bromová, P.; Bařina, D.; Škoda, Petr; Vážný, Jaroslav; Zendulka, J.
Astronomický ústav, 2013

Wavelet Based Feature Extraction for Clustering of Be Stars
Bromová, P.; Škoda, Petr; Zendulka, J.
2013 - English
The goal of our work is to create a feature extraction method for classification of Be stars. Be stars are characterized by prominent emission lines in their spectrum. We focus on the automated classification of Be stars based on typical shapes of their emission lines. We aim to design a reduced, specific set of features characterizing and discriminating the shapes of Be lines. In this paper, we present a feature extraction method based on the wavelet transform and its power spectrum. Both the discrete and continuous wavelet transform are used. Different feature vectors are created and compared on clustering of Be stars spectra from the archive of the Astronomical Institute of the Academy of Sciences of the Czech Republic. The clustering is performed using the kmeans algorithm. The results of our method are promising and encouraging to more detailed analysis. Keywords: feature extraction; stellar spectra; wavelet transform Available at various institutes of the ASCR
Wavelet Based Feature Extraction for Clustering of Be Stars

The goal of our work is to create a feature extraction method for classification of Be stars. Be stars are characterized by prominent emission lines in their spectrum. We focus on the automated ...

Bromová, P.; Škoda, Petr; Zendulka, J.
Astronomický ústav, 2013

On transfer of mass and angular momentum from accretion disk onto black hole
Hamerský, Jaroslav; Karas, Vladimír
2012 - English
We study the properties of accretion tori orbiting Kerr black hole. Our approach to this problem comes from the solving of general relativistic magnetohydrodynamic equations, which follow from conservation of the energy-momentum tensor, the particle number and from Maxwell's equations. We solve these equations by numerical methods. We are interested in tori with constant density of angular momentum and those with radially increasing angular momentum density. We study accretion rates in these tori when the mass of black hole is increased suddenly and so the equilibrium in the torus is perturbed. We also study the influence of the presence of toroidal magnetic field on accretion rates. Keywords: accretion disk; relativity; MHD Available at various institutes of the ASCR
On transfer of mass and angular momentum from accretion disk onto black hole

We study the properties of accretion tori orbiting Kerr black hole. Our approach to this problem comes from the solving of general relativistic magnetohydrodynamic equations, which follow from ...

Hamerský, Jaroslav; Karas, Vladimír
Astronomický ústav, 2012

Feature extraction using wavelet power spectrum for stellar spectra clustering
Škoda, Petr; Bromová, P.; Zendulka, J.
2012 - English
This paper analyses the capabilities of using wavelet power spectrum for clustering of Be-type stars spectra. We propose a method using discrete wavelet transform for feature extraction and the wavelet power spectrum as a feature vector. Keywords: Be star; stellar spectrum; feature extraction Available at various institutes of the ASCR
Feature extraction using wavelet power spectrum for stellar spectra clustering

This paper analyses the capabilities of using wavelet power spectrum for clustering of Be-type stars spectra. We propose a method using discrete wavelet transform for feature extraction and the ...

Škoda, Petr; Bromová, P.; Zendulka, J.
Astronomický ústav, 2012

Analysis and Suppression of Noise in Astronomical Video
Švihlík, J.; Fliegel, K.; Koten, Pavel; Jerhotova, E.; Vítek, S.; Páta, P.
2011 - English
This paper is devoted to noise suppression in systems for double station observation of meteors, nowadays known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis based on acquisition of testing video sequences at different lighting conditions and their statistical evaluation were described in our previous paper The measurement showed that the type of noise generated by the system is signal-independent in a certain illumination range. The noise and image models in the wavelet domain are based on the Generalized Laplacian Model (GLM) and it is the most convenient to estimate the model parameters using the moment method. Furthermore, the noise component may be modeled by the GLM also in the space domain. Overall, we verified that the GLM allows for modeling various types of probability density functions. In the final section of this paper, the performance of the proposed advanced de noising algorithm is verified on the real data, which were acquired in the Astronomical Institute. Keywords: MAIA; meteor; noise analysis Available at various institutes of the ASCR
Analysis and Suppression of Noise in Astronomical Video

This paper is devoted to noise suppression in systems for double station observation of meteors, nowadays known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis based on acquisition ...

Švihlík, J.; Fliegel, K.; Koten, Pavel; Jerhotova, E.; Vítek, S.; Páta, P.
Astronomický ústav, 2011

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