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Compton scattering in strong gravity
Bursa, Michal; Adámek, K.
2014 - anglický
The authors present new numerical code for radiation transport in strong gravity regime that includes arbitrary emission and absorption mechanisms and also electron scattering.
Klíčová slova:
radiation transport; relativity; Compton scattering
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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.
Upcoming Features of SPLAT-VO in Astroinformatics
Šaloun, P.; Andrešič, D.; Škoda, Petr; Zelinka, I.
2013 - anglický
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.
Klíčová slova:
SPLAT-VO; spectrum analysis; SAMP
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Classification on Be stars using feature extraction based on discrete wavelet transform
Bromová, P.; Bařina, D.; Škoda, Petr; Vážný, Jaroslav; Zendulka, J.
2013 - anglický
We describe the initial experiments in the field of automated classification of spectal line profiles of emission line stars.
Klíčová slova:
Be star; stellar spectrum; feature extraction
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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.
Wavelet Based Feature Extraction for Clustering of Be Stars
Bromová, P.; Škoda, Petr; Zendulka, J.
2013 - anglický
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.
Klíčová slova:
feature extraction; stellar spectra; wavelet transform
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
On transfer of mass and angular momentum from accretion disk onto black hole
Hamerský, Jaroslav; Karas, Vladimír
2012 - anglický
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.
Klíčová slova:
accretion disk; relativity; MHD
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
New model of precession, valid in time interval 400 thousand years
Vondrák, Jan
2012 - anglický
New model of precession, expressed in terms of long-periodic trigonometric functions of time is developed, based on numerical integration of motions of the Solar system bodies. Its validity is +/- 200 thousand years from the basic epoch J2000, with the accuracy below one milliarcsecond in the central part and gradually decreasing to a few arcminutes towards both ends of the interval of validity.
Klíčová slova:
reference systems; precession
Dokument je dostupný na externích webových stránkách.
New model of precession, valid in time interval 400 thousand years
New model of precession, expressed in terms of long-periodic trigonometric functions of time is developed, based on numerical integration of motions of the Solar system bodies. Its validity is +/- 200 ...
Feature extraction using wavelet power spectrum for stellar spectra clustering
Škoda, Petr; Bromová, P.; Zendulka, J.
2012 - anglický
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.
Klíčová slova:
Be star; stellar spectrum; feature extraction
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Analysis and Suppression of Noise in Astronomical Video
Švihlík, J.; Fliegel, K.; Koten, Pavel; Jerhotova, E.; Vítek, S.; Páta, P.
2011 - anglický
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.
Klíčová slova:
MAIA; meteor; noise analysis
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Kosmologie, čísla a Platonova duše světa
Rajchl, Jaroslav
2011 - český
Současná kosmologie se vyznačuje velkým množstvím nejrůznějších modelů. Bližší pohled ukazuje, že všechny oplývají určitým typem dualnosti, a sice propojením dynamické a formativní podoby, jejichž společným zdrojem je známý Velký třesk (BB). Abychom zpřehlednili onen složitý obraz, vybrali jsme jako určitý sjednocující symbol tzv. Platonův model duše světa (PDS), který vychází z Pythagorova postřehu, že analogickou dualností se vyznačují i čísla. The present status of cosmology is characterized by a variety of many different models. Nevertheless, it shows that some type of duality of both dynamical and the structural nature is typical. Its common source is the Big Bang (BB). To reconcile this very rich manifold we use the Plato’s model „of the World Soul”. Its main idea is the Pythagoras’ one of the role of numbers as fundamental elements of all the things in the World.
Klíčová slova:
cosmology models; numbers; Plato's model
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Kosmologie, čísla a Platonova duše světa
Současná kosmologie se vyznačuje velkým množstvím nejrůznějších modelů. Bližší pohled ukazuje, že všechny oplývají určitým typem dualnosti, a sice propojením dynamické a formativní podoby, jejichž ...
Extremal energy shifts of radiation from a ring near a rotating black hole
Sochora, Vjačeslav; Karas, Vladimír
2010 - anglický
We present a semi-analytical solution to the problem of finding minimal and maximal energy shifts of radiation originating from an accretion ring near a black hole. The solution is given implicitly in terms of a set of two coupled equations for two unknowns – the constants of photon motion.
Klíčová slova:
black holes; accretion
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Extremal energy shifts of radiation from a ring near a rotating black hole
We present a semi-analytical solution to the problem of finding minimal and maximal energy shifts of radiation originating from an accretion ring near a black hole. The solution is given implicitly in ...
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