Shumen, Bulgaria
Shumen, Bulgaria

The Constantine of Preslav University of Shumen in Bulgaria is named after one of the most well-educated and talented students of Saints Cyril and Methodius, Constantine of Preslav. He was a writer, a religious figure and a significant person in Old Bulgarian culture. Wikipedia.


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Petkova P.,University of Shumen | Boubaker K.,University of Tunis
Journal of Alloys and Compounds | Year: 2013

In this study, we try to give an explanation to the spectacular Urbach tailing associated to some nano-scale lattice disordering which has been recorded in (BSO) and germanates (BGO) compounds. Some experimental and theoretical items are presented in order to give a possible understanding to the controversial Urbach tailing: the Lattice Compatibility Theory (LCT). © 2012 Elsevier B.V. All rights reserved.


Stoyanov B.P.,University of Shumen
AIP Conference Proceedings | Year: 2012

We propose a new cryptographic scheme based on the Lorenz chaos attractor and 32 bit bent Boolean function. We evaluated the keystream generated by the scheme with batteries of the NIST statistical tests. We also applied a number of statistical analysis techniques, such as calculating histograms, correlations between two adjacent pixels, information entropy, and differential resistance, all refer to images encrypted by the proposed system. The results of the analysis show that the new cryptographic scheme ensures a secure way for sending digital data with potential applications in real-time image encryption. © 2012 American Institute of Physics.


Yankov N.,University of Shumen
IEEE Transactions on Information Theory | Year: 2012

In this paper, we prove that there does not exist a binary self-dual doubly even $[72, 36, 16]$ code with an automorphism of order 9. To do so, we apply a method for constructing binary self-dual codes possessing an automorphism of order $p2$ for an odd prime $p$. © 2006 IEEE.


Dimitrov D.P.,Bulgarian Academy of Science | Kjurkchieva D.P.,University of Shumen
Monthly Notices of the Royal Astronomical Society | Year: 2010

CCD photometric observations in VRI colours and spectroscopic observations of the newly discovered eclipsing binary GSC 2314-0530 (NSVS 6550671) with dMe components and a very short period of P = 0.192 636 d are presented. The simultaneous light-curve solution and radial velocity solution allow us to determine the global parameters of GSC 2314-0530: T1 = 3735 K; T2 = 3106 K; pc. The chromospheric activity of its components is revealed by strong emission in the Hα line (with mean EW = 5 Å) and several observed flares. Empirical relations for mass-, mass-radius and mass-temperature are derived on the basis of the parameters of known binaries with low-mass dM components. © 2010 The Authors. Journal compilation © 2010 RAS.


Georgiev G.H.,University of Shumen
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

We discuss geometric conditions for a planar rational curve to be a spiral. The main used tool for characterizing a spiral is the so-called shape curvature which is a differential-geometric invariant of planar curves with respect to the group of orientation-preserving similarities. Different formulas for computation of shape curvature are given. Rational curves representing spirals and circular arcs possess a natural description in terms of the shape curvature. This description is applied to a complete classification of quadratic Bézier spirals. © 2012 Springer-Verlag.


Stoyanov B.P.,University of Shumen
AIP Conference Proceedings | Year: 2013

In this paper, we study a pseudo-random bit generator based on two Chebyshev polynomial maps. The novel derivative algorithm shows perfect statistical properties established by number of statistical tests. © 2013 AIP Publishing LLC.


Nedzhibov G.H.,University of Shumen
Computers and Mathematics with Applications | Year: 2012

A new two-point iterative method for solving nonlinear equations is presented. This is a derivative-free method for the simultaneous determination of several or all of the simple zeros. It is proved that the proposed method possesses a quadratic convergence locally. Numerical examples are given to illustrate the efficiency and performance of the method presented. © 2011 Elsevier Ltd. All rights reserved.


Stoyanov B.,University of Shumen
Advanced Studies in Theoretical Physics | Year: 2014

In this paper, we design a self-shrinking scheme which combines a feedback with carry shift register and the self-shrinking generator, based on A. Kanso PhD study. We calculated the period of the designed algorithm. The key gamma is statistically tested with NIST test suite. The result of the analysis shows that the properties of the output bits are like randomly generated physical phenomena. © 2014 Borislav Stoyanov.


Stoyanov B.P.,University of Shumen
AIP Conference Proceedings | Year: 2014

We propose a novel Circle map based pseudorandom bit generation scheme. We evaluated the output streams by the NIST, DIEHARD and ENT statistical packages. The results of the tests show that the new generator provides an exclusive level of randomness of the bit sequences. © 2014 AIP Publishing LLC.


Kordov K.M.,University of Shumen
AIP Conference Proceedings | Year: 2014

In this paper we use Chebyshev polynomials of the first kind to generate pseudo-random binary sequences. The modified generator use a new scheme of bit extraction applied to four Chebyshev maps. The properties of the generated sequence is analysed by speed test and statistical NIST, ENT and DIEHARD packages. © 2014 AIP Publishing LLC.

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