Institute of Information Technologies

Sofia, Bulgaria

Institute of Information Technologies

Sofia, Bulgaria
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Adamczyk M.,University of Silesia | Kozielski L.,University of Silesia | Bochenek D.,University of Silesia | Radoszewska D.,University of Silesia | And 2 more authors.
European Physical Journal B | Year: 2016

In recent years a wide range of Aurivillius layered materials have been introduced. These novel materials are produced in many various forms such as fibers, thin films as well as bulk by using a number of processing routes. As advanced materials they are they have many interesting properties which include a number of useful electrical properties related to separated grain and grain boundary conductivity, impedance, activation energies, etc. In this paper these properties are described and discussed in detail. The electrical properties of the vanadium doped BaBi2Nb2O9 ceramic was measured over a wide range of temperatures by impedance spectroscopy (IS). The separated grain activation energy, calculated from Arrhenius characteristics at temperatures between room temperature and 600 °C, was 1 eV for 0 at.% of vanadium dopant and 1.2 eV for 10 at.%, whereas the activation energies in the grain boundary region were 0.97 and 1.15 eV, respectively. The obtained results suggest the significant role of vanadium dopant, causing ordering the crystalline structure. © 2016, The Author(s).


Adamczyk M.,University of Silesia | Kozielski L.,University of Silesia | Pilch M.,University of Silesia | Pawelczyk M.,Institute of Information Technologies | Soszynski A.,University of Silesia
Ceramics International | Year: 2013

The article reports the successful preparation of single-phase vanadium doped BaBi2Nb2O9 ceramics. In the first part of the paper we would like to present the results of the XRD measurements, which allows us to determine the lattice parameters. The parameters do not change, which implies that the vanadium ions ordering of the crystal structure causes the decreasing number of defects. The conclusion stays consistent with the results of dielectric and thermal stimulated depolarization currents measurements, described in the second part of the paper. The pure BBN ceramics, as well as the ones modified by vanadium, show the frequency dependence of the dielectric response typical for relaxor ferroelectrics i.e. the significant reduction of SYMBOL 101 f "Symbol" s 12e'max and shift of the corresponding temperature (Tm) towards higher values with the frequency increase. However the vanadium substitution causes a reduction of the value of parameters describing the relaxor properties. © 2012 Elsevier Ltd and Techna Group S.r.l.


Behar V.,Bulgarian Academy of Science | Kabakchiev C.,Sofia University | Kyovtorov V.,Institute of Information Technologies
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

In this paper, the Space-Time Array Processing (STAP) approach is applied to sound source localization using adaptive microphone arrays. Two beamforming methods, conventional and MVDR are used for estimating the direction-of arrival (DOA) of sound signals arrived at the microphone array from different sensors in the observation area. The simulation scenario describes a situation where three sensors generating three different sound signals (warning, alarm and emergency) and one source of natural noise (car) are located at various points in the observation area. The results obtained demonstrate that in contrast to the conventional method of beamforming the MVDR gives accurate estimates of The DOA of all sound signals generated by sensors in the observation area. © 2010 SPIE.


Kyovtorov V.,Institute of Information Technologies | Kabakchiev H.,Sofia University | Behar V.,Bulgarian Academy of Science
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

This paper studies the influence of non-uniform sampling on the power line flicker estimation. A digital non-uniform sampling MATLAB flickermeter model is considered. The model is fully compliant with the CEI/IEC 61000-4-15 standard and is tested within mains frequency variations 50Hz +/- 2.5Hz. The normalized flickermeter response and the flickermeter classifier are tested according to the IEC standard recommendations. The results indicate that the most sensitive point 8.8Hz is influenced within the standard error +/- 0.05 and only the last testing point exceeds the prescribed standard error. © 2010 SPIE.


Kabakchiev Chr.,Sofia University | Behar V.,Institute for Parallel Processing | Rohling H.,TU Hamburg - Harburg | Garvanov I.,Institute of Information Technologies | And 2 more authors.
IEEE National Radar Conference - Proceedings | Year: 2010

This paper describes in details the performance of an advanced detecting algorithm for multi-sensor target Track Before Detection (TBD) through the Hough Transform (HT). The detection algorithm employs the idea of using the Hough Transform for joint detection of linear trajectory targets. The polar modification of the TBD-HT approach is applied to a multi-sensor Polar Hough detector for multi-sensor target/trajectory detection in ECM environment with a Stand-off-Jammer (SOJ). A CFAR detector is proposed for signal detection in the (r-t) space instead of fixed thresholding in order to enhance the target detectability in ECM environment. In this paper a centralized structure of a multi-sensor Polar Hough detector is considered. The expressions calculating the probability characteristics, i.e. the probability of target/trajectory detection and the false alarm probability, are analytically derived. The multi-channel TBD-HT detector probability characteristics are compared with those for the conventional signal processing. © 2010 IEEE.


Chizh A.,B. I. Stepanov Institute of Physics | Malyshev S.,B. I. Stepanov Institute of Physics | Tepteev A.,Minsk Research Institute of Radiomaterials | Andrievski V.,Institute of Information Technologies | And 2 more authors.
2012 IEEE International Topical Meeting on Microwave Photonics, MWP 2012 - Proceedings | Year: 2012

A new high-speed high-power photodiode design based on beam-lead technology to reduce thermal resistance and series contact resistance, which limit the saturation photocurrent of photodiodes with small active area, has been presented. © 2012 IEEE.


Ruzhentsev V.,Institute of Information Technologies | Oliynykov R.,Institute of Information Technologies | Stupak V.,Institute of Information Technologies
Modern Problems of Radio Engineering, Telecommunications and Computer Science - Proceedings of the 10th International Conference, TCSET'2010 | Year: 2010

The analysis of existing requirements for MDS matrices that are used in block ciphers is performed, the most important requirements are selected, and matrix corresponding to the selected requirements is constructed.


Oliynykov R.,Kharkiv National University of Radioelectronics | Oliynykov R.,Institute of Information Technologies | Gorbenko I.,Kharkiv National University of Radioelectronics | Gorbenko I.,Institute of Information Technologies | And 2 more authors.
Proceedings of the 6th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications, IDAACS'2011 | Year: 2011

An exact value of round functions collision probability for 3-round Feistel network is derived. The upper bound of algorithm execution complexity for distinguishing Feistel network from a random permutation is given. © 2011 IEEE.

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