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136
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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 ...
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 ...
The study of magnetic clouds: expansion and discontinuities
Lynnyk, A.; Vandas, Marek
2009 - anglický
Magnetic clouds observed during the 1995-2003 years are fitted using force-free cylindrical flux rope models. The cloud parameters yielded by a static model are compared with those obtained from a modified model that includes magnetic cloud expansion.
Klíčová slova:
magnetic field; magnetic cloud; solar wind
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The study of magnetic clouds: expansion and discontinuities
Magnetic clouds observed during the 1995-2003 years are fitted using force-free cylindrical flux rope models. The cloud parameters yielded by a static model are compared with those obtained from a ...
Shell-Like Structures in the ISM: Observation Versus Simulations
Sidorin, Vojtěch; Palouš, Jan
2009 - anglický
The interstellar medium in galaxies is a turbulent environment with a plethora of holes, bubbles and shells. All these shell-like structures are thought to be closely related to the formation, evolution and death of stars. In most cases, they are likely created by the winds of OB stars and supernovae. The material collected along the borders of shells may fragment, become unstable under its own gravity, and create a new generation of stars. This is a variant of triggered star formation referred to as the collect-and-collapse scenario. The aim of our research is to compare numerical simulations of shell-like structures to observations and to search for and investigate regions of triggered star formation in the Milky Way.
Klíčová slova:
shells; ism; triggered star formation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Shell-Like Structures in the ISM: Observation Versus Simulations
The interstellar medium in galaxies is a turbulent environment with a plethora of holes, bubbles and shells. All these shell-like structures are thought to be closely related to the formation, ...
Comparison of relativistic iron line models
Svoboda, Jiří; Dovčiak, Michal; Goosmann, René; Karas, Vladimír
2008 - anglický
The analysis of the broad iron line profile in the X-ray spectra of active galactic nuclei and black hole X-ray binaries allows us to constrain the spin parameter of the black hole. We compare the constraints on the spin value for two X-ray sources, MCG-6-30-15 and GX 339-4, with a broad iron line using present relativistic line models in XSPEC - LAOR and KYRLINE. Analýza profilu široké čáry železa v rentgenových spektrech aktivních galaxií a mikrokvasarů nám umožňuje určit spin černé díry. Porovnávame výsledky pro dva rentgenové zdroje, MCG-6-30-15 a GX 339-4, se širokou čárou železa pomocí současných modelů relativistické čáry v programu XSPEC - LAOR a KYRLINE.
Klíčová slova:
accretion; accretion disks; black holes
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Comparison of relativistic iron line models
The analysis of the broad iron line profile in the X-ray spectra of active galactic nuclei and black hole X-ray binaries allows us to constrain the spin parameter of the black hole. We compare the ...
Statistical study of the fitting of the magnetic clouds
Lynnyk, A.; Vandas, Marek
2008 - anglický
The paper is a statictical study on comparisons between a model of an expanding magnetic cloud and observations. Práce je statistickou studií o srovnání modelu expandujícího magnetického oblaku s pozorováními.
Klíčová slova:
magnetic clouds; solar wind; interplanetary magnetic field
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Statistical study of the fitting of the magnetic clouds
The paper is a statictical study on comparisons between a model of an expanding magnetic cloud and observations....
Modelling the polarization dichotomy of active galactic nuclei
Goosmann, René
2007 - anglický
I present polarization modelling of Active Galactic Nuclei in the optical/UV range. The modelling is conducted using the Monte-Carlo radiative transfer code Stokes, which self-consistently models the polarization signature of a complex model arrangement for an active nucleus. Prezentuji modelování polarizace záření aktivních galaktických jader v optické a UV oblasti. Při modelování je použit kód Stokes pro Monte Carlo simulace přenosu záření, který selfkonzistentně modeluje polarizaci geometricky komplexního uspořádání aktivního jádra.
Klíčová slova:
active galaxies; radiative transfer; polarization
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling the polarization dichotomy of active galactic nuclei
I present polarization modelling of Active Galactic Nuclei in the optical/UV range. The modelling is conducted using the Monte-Carlo radiative transfer code Stokes, which self-consistently models the ...
Magnetic clouds and their expansion
Lynnyk, A.; Vandas, Marek
2007 - anglický
Magnetic clouds for the years 1995-1998 are analyzed using a model of a force-free cylindrical flux rope which may include cloud expansion. Clearly pronounced expansion was found in 80% cases. It was found that including the expansion makes comparison between model and experimental data better in 75% of these cases. Analyzovali jsme magnetická oblaka pro roky 1995-1998 s použitím modelu bezsilové magnetické válcové silotrubice, jež může zahrnovat expanzi. Zřetelná expanze oblaků byla zjištěna v 80%.Zahrnutí expanze zlepšuje srovnání modelu s měřeními u 75% z těchto případů.
Klíčová slova:
magnetic clouds; solar wind; magnetic field
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Magnetic clouds and their expansion
Magnetic clouds for the years 1995-1998 are analyzed using a model of a force-free cylindrical flux rope which may include cloud expansion. Clearly pronounced expansion was found in 80% cases. It ...
Flares from spiral waves by lensing and time-delay amplification?
Karas, Vladimír; Dovčiak, Michal; Eckart, A.; Meyer, L.
2007 - anglický
We examine physics of flares from spiral waves by lensing and time-delay amplification. Zabýváme se fyzikou záblesků ze spirálních vln ovlivněných efektem čočkování a časového zpoždění.
Klíčová slova:
black holes
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Flares from spiral waves by lensing and time-delay amplification?
We examine physics of flares from spiral waves by lensing and time-delay amplification.
Zabýváme se fyzikou záblesků ze spirálních vln ovlivněných efektem čočkování a časového zpoždění.
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