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Search Results: 1 - 10 of 223668 matches for " R. Hudec "
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The Role of Ground-Based Robotic Observatories in Satellite Projects
R. Hudec
Advances in Astronomy , 2010, DOI: 10.1155/2010/594854
Abstract: We discuss the role of robotic telescopes in satellite projects, as well as related strategies. Most satellite projects in space astrophysics focus on high-energy astrophysics from X-rays to gamma-rays. A large fraction of objects of high-energy astrophysics emit also optical light, which is, in many cases, variable. The observation of these sources at optical wavelengths can provide valuable inputs for multispectral analysis of various categories of celestial high-energy (HE) sources. As the magnitudes of numerous objects are bright and can be hence accessed by robotic ground-based observatories, these observations can contribute to investigations and analyses of HE sources. We discuss in detail this possible contribution, with emphasis on the ESA INTEGRAL mission. In addition to this, there are also satellite projects outside the high-energy astronomy, in which the robotic telescopes can also play an important role. We will illustrate this on the example of the ESA satellite Gaia. In this project, robotic telescopes are expected not only to verify the triggers detected by satellite (such as transients and flares) but also to provide additional (mostly photometric) data for better scientific cases. 1. Introduction Most satellite projects in space astrophysics focus on high energy astrophysics from X-rays to gamma-rays. A large fraction of objects of high-energy astrophysics emit also optical light, which is, in many cases, variable (Figure 1). The observation of these sources at optical wavelengths can provide valuable inputs for multispectral analysis of various categories of celestial high-energy (HE) sources. As the magnitudes of numerous objects are bright and can be hence accessed by (even small) robotic telescopes, these devices can effectively contribute to investigations and analyses of HE sources. Figure 1: The distribution of optical magnitudes of optically identified INTEGRAL gamma-ray sources. Most are brighter than mag?20, and more than half are brighter than mag?15. Legend dark blue mag?2–6, orange mag?5–10, yellow mag?10–14, green mag?14–18, purple mag?18–22, light blue mag?22–26. The numbers in the plot indicate number of objects with optical magnitude within the indicated range. In addition to this, the robotic telescopes can also play an important role in satellite projects outside high-energy astrophysics. The astrometry mission Gaia of European Space Agency ESA can serve here as an example. As it will be shown later, very common is the situation when we have satellite (e.g., HE) monitoring data covering up to years, but we do not
Mixed Noise Suppression in Color Images by Signal-Dependent LMS L-Filters
R. Hudec
Radioengineering , 2003,
Abstract: The paper is devoted to the signal-dependent (SD) design of adaptiveLMS L-filters with marginal data ordering for color images. The samestem of SD processing of noised grayscale images was applied on noisycolor images. Component-wise and multichannel modifications of SD LMSL-filter in R'G'B' (gamma corrected RGB signals) color space weredeveloped. Both modifications for filtering two-dimensional staticcolor images degraded by mixed noise consisting of additive Gaussianwhite noise and impulsive noise were used. Moreover, single-channelspatial impulse detectors as detectors of impulses and details wereused, too. Considering experimental results, SD modifications ofL-filters for noisy color images can be concluded to yield the bestresults.
Novel Method for Color Textures Features Extraction Based on GLCM
M. Benco,R. Hudec
Radioengineering , 2007,
Abstract: Texture is one of most popular features for image classification and retrieval. Forasmuch as grayscale textures provide enough information to solve many tasks, the color information was not utilized. But in the recent years, many researchers have begun to take color information into consideration. In the texture analysis field, many algorithms have been enhanced to process color textures and new ones have been researched. In this paper the new method for color GLCM textures and comparing with other good known methods is presented.
Adaptive Order-Statistic LMS Filters
R. Hudec,S. Marchevsky
Radioengineering , 2001,
Abstract: The LMS-based adaptive order-statistic filters are presented in thispaper. The adaptive Ll-filters as extension of the adaptive L-filterfor two-dimensional filtering of noisy greyscale images is studied too.Their adaptation properties are studied by three types of noise, theadditive white Gaussian noise, the impulsive noise or both,respectively. Moreover, the impulsive noise has the fixed noise value(Salt & Pepper noise). The problem of pixel value multiplicity anddetermination its position in the ordered input vector for adaptiveLl-filter is shown in this article. The two types of images withdifferent of image complexity are used to demonstration of the power oftime-spatial ordering.
Extension of Impulse Detectors to Spatial Dimension and their Utilization as Switch in the LMS L-SD Filter
R. Hudec,S. Marchevsky
Radioengineering , 2001,
Abstract: In this paper, one kind of adaptive LMS filters based on orderstatistics is used for two-dimensional filtration of noisy greyscaleimages degraded by mixed noise. The signal-dependent adaptive LMSL-filter (L-SD) consists of two normalized constrained adaptive LMSL-filters, because they have better convergence properties than simpleLMS algorithm. Moreover, first filter suppresses the noise inhomogeneous regions and second filter preserves the high components offiltered image. Some versions of spatial order statistic detectors weredeveloped from the impulse detectors and were employed as switchbetween output these filters.
Suppression of Mixed Noise in the Similar Images by Using Adaptive LMS L-filters
D. Kocur,R. Hudec,S. Marchevsky
Radioengineering , 2000,
Abstract: In this paper, several adaptive least mean squares (LMS)location-invariant filter (L-filter) modifications will be described.These filters are based on linear combination of order statistics. Theadaptive L-filters are able to adapt well to variety of noiseprobability distribution, including impulsive noise. They also performwell in the case of nonstationary signals and, therefore, they aresuitable for image processing, too. Following this L-filter property,applications of the adaptive LMS L-filters for filteringtwo-dimensional static images degraded by mixed noise consisting ofadditive Gaussian white noise and impulsive noise will be presented inthis paper. Based on conveniently selected experiments intent on imagefiltering, the properties of a several adaptive L-filters modificationswill be demonstrated and compared. It will follow from experimentresults, that the L-filter modification called signal-dependent LMSL-filter yields the best results.
Róbert Mazur,Kamila Kovalovská,Jozef Hudec
Journal of Microbiology, Biotechnology and Food Sciences , 2011, DOI: 13385178
Abstract: In this study we observe the effect of fermentation conditions and resources of microorganisms for production of γ-aminobutyric acid (GABA). The content of produced GABA depends on various conditions such as the amount of precursor, an addition of salt, enzyme and the effect of pH. The highest selectivity of GABA (74.0 %) from the precursor (L-monosodium glutamate) has been determinate in the follow conditions: in the presence of pre-cultured microorganisms from Encián cheese in amount 1.66 % (w/v) the source of microorganisms/volume of the fermentation mixture, after the addition of 0.028 % (w/v) of CaCl2/volume of the fermentation mixture, 100 μM of pyridoxal-5-phosphate (P-5-P) and the GABA precursor concentration in the fermentation mixture 2.6 mg ml-1 in an atmosphere of gas nitrogen. Pure cultures of lactic acid bacteria increased the selectivity of GABA by an average of 20 % compared with bacteria from the path of Encián.
A Novel Approach to Face Recognition using Image Segmentation based on SPCA-KNN Method
P. Kamencay,M. Zachariasova,R. Hudec,R. Jarina
Radioengineering , 2013,
Abstract: In this paper we propose a novel method for face recognition using hybrid SPCA-KNN (SIFT-PCA-KNN) approach. The proposed method consists of three parts. The first part is based on preprocessing face images using Graph Based algorithm and SIFT (Scale Invariant Feature Transform) descriptor. Graph Based topology is used for matching two face images. In the second part eigen values and eigen vectors are extracted from each input face images. The goal is to extract the important information from the face data, to represent it as a set of new orthogonal variables called principal components. In the final part a nearest neighbor classifier is designed for classifying the face images based on the SPCA-KNN algorithm. The algorithm has been tested on 100 different subjects (15 images for each class). The experimental result shows that the proposed method has a positive effect on overall face recognition performance and outperforms other examined methods.
Complicated variations of early optical afterglow of GRB 090726
V. Simon,C. Polasek,M. Jelinek,R. Hudec,J. Strobl
Physics , 2009, DOI: 10.1051/0004-6361/200913393
Abstract: We report on a detection of an early rising phase of optical afterglow (OA) of a long GRB 090726. We resolve a complicated profile of the optical light curve. We also investigate the relation of the optical and X-ray emission of this event. We make use of the optical photometry of this OA obtained by the 0.5 m telescope of AI AS CR, supplemented by the data obtained by other observers, and the X-ray Swift/XRT data. The optical emission peaked at ~ 17.5 mag (R) at t-T0 ~ 500 s. We find a complex profile of the light curve during the early phase of this OA: an approximately power-law rise, a rapid transition to a plateau, a weak flare superimposed on the center of this plateau, and a slowly steepening early decline followed by a power-law decay. We discuss several possibilities to explain the short flare on the flat top of the optical light curve at t-T0 ~ 500 s; activity of the central engine is favored although reverse shock cannot be ruled out. We show that power-law outflow with Theta_obs/Theta_c > 2.5 is the best case for OA of GRB 090726. The initial Lorentz factor is Gamma_0 ~ 230-530 in case of propagation of the blast wave in a homogeneous medium, while propagation of this wave in a wind environment gives Gamma_0 ~ 80-300. The value of Gamma_0 in GRB 090726 thus falls into the lower half of the range observed in GRBs and it may even lie on the lower end. We also show that both the optical and X-ray emission decayed simultaneously and that the spectral profile from X-ray to the optical band did not vary. This OA belongs to the least luminous ones in the phase of its power-law decay corresponding to that observed for the ensemble of OAs of long GRBs.
Gamma-Ray Burst Classes Found in the RHESSI Data Sample
J. Ripa,C. Wigger,D. Huja,R. Hudec
Physics , 2010,
Abstract: A sample of 427 gamma-ray bursts (GRBs), measured by the RHESSI satellite, is studied statistically to determine the number of GRB groups. Previous studies based on the BATSE Catalog and recently on the Swift data claim the existence of an intermediate GRB group, besides the long and short groups. Using only the GRB durations T90 and chi^2 or F-test, we have not found any statistically significant intermediate group. However, the maximum likelihood ratio test, one-dimensional as well as two-dimensional hardness vs. T90 plane, reveal the reality of an intermediate group. Hence, the existence of this group follows not only from the BATSE and Swift datasets, but also from the RHESSI results.
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