Number of found documents: 557
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Message Embedded Synchronization for the Generalized Lorenz System and Its Use for Chaotic Masking
Čelikovský, Sergej; Lynnyk, Volodymyr
2013 - English
This paper implements and analyzes the well-known message embedded synchronization scheme for the case of the generalized Lorenz system. Such a synchronization may be used for chaotic masking scheme using a single channel only. This method was already discussed in the earlier literature for the particular classes of systems. In this paper, a more general class wheremessage embedded synchronization is possible is described. Then, it is shown that the generalized Lorenz system falls within that class. Furthermore, using the resulting synchronization, the novel secure encryption scheme is proposed. It requires very reasonable amount of data to encrypt and time to decrypt one bit. Basically, to encrypt one bit, only one iteration (i.e. only one real number of 6 valid digits) is needed. At the same time, 100 percent of the carrying chaotic signal can be used. The method is also demonstrated by numerical simulations of a digital data encryption and decryption. Keywords: chaos synchronization; secury encryption Available at various institutes of the ASCR
Message Embedded Synchronization for the Generalized Lorenz System and Its Use for Chaotic Masking

This paper implements and analyzes the well-known message embedded synchronization scheme for the case of the generalized Lorenz system. Such a synchronization may be used for chaotic masking scheme ...

Čelikovský, Sergej; Lynnyk, Volodymyr
Ústav teorie informace a automatizace, 2013

Characteristics of the Chen Attractor
Augustová, Petra; Beran, Zdeněk
2013 - English
Within the paper a mathematical representation of the so-called Chen model is described as a particular parametric three-dimensional chaotic dynamical system, i.e. a system of three nonlinear differential equations evolving in time. The main aim of this paper is to find for the Chen system the properties that are known for the Lorenz system and its famous Lorenz attractor. First, the integrals of motion are derived for some parameters of the Chen system. The integrals of motions play an important role in physics, e.g. for conservation laws. Next, the shape of the global attractor of this system is approximated by volumes that contain the attractor. The shape predicts the future behavior of the system. To obtain these results, the already proved fact that the Chen system is a continued transition of the Lorenz system is used. According to our knowledge, the same approach of shifting the known facts about the Lorenz system to a newdynamical system, the Chen system in this context, has not been presented yet. Keywords: chaotic dynamical system; Lorenz system; Chen system Available at various institutes of the ASCR
Characteristics of the Chen Attractor

Within the paper a mathematical representation of the so-called Chen model is described as a particular parametric three-dimensional chaotic dynamical system, i.e. a system of three nonlinear ...

Augustová, Petra; Beran, Zdeněk
Ústav teorie informace a automatizace, 2013

Odhalování kopií pomocí matematického zpracování obrazu, část I: teoretická východiska a princip metody
Blažek, Jan; Hradilová, J.; Zitová, Barbara; Kamenický, Jan
2012 - Czech
Navrhujeme poloautomatické metody pro geometrické sesazení (dále jen registraci) a pro komparaci digitálních snímků uměleckých děl. Algoritmus registrace je založen na odhadu perspektivní transformace pomocí kontrolních bodů. Porovnání snímků je založeno na statistické analýze snímků, normalizaci jasu a absolutní odchylce. Vhodnost různých metod porovnání je demonstrována na příkladech. Výstupem algoritmů jsou srozumitelné rozdílové mapy. Navrhované metody jsou implementovány ve veřejně dostupné aplikaci Fresco. We propose semi-automatic methods for registration and comparison digital images of fine art. Registration algorithm is based on estimation of perspective transformation parameters according to control points. Image comparison is based on statistical analysis of images, normalization of brightness and absolute deviation. Suitability of comparing algorithms is demonstrated on examples. As an output of comparing algorithms are used intelligible differential maps. Keywords: Perspective transformation; perspective; image difference; graphical software Available at various institutes of the ASCR
Odhalování kopií pomocí matematického zpracování obrazu, část I: teoretická východiska a princip metody

Navrhujeme poloautomatické metody pro geometrické sesazení (dále jen registraci) a pro komparaci digitálních snímků uměleckých děl. Algoritmus registrace je založen na odhadu perspektivní transformace ...

Blažek, Jan; Hradilová, J.; Zitová, Barbara; Kamenický, Jan
Ústav teorie informace a automatizace, 2012

Rima Glottidis Segmentation by Thresholding Using Graph Cuts
Novozámský, Adam
2012 - English
We proposed a new segmentation method base on thresholding for detection rima glottidis. A proper search for glottis is very important for further analysis of the features. Keywords: video imaging; vocal chords; videokymography Available at various institutes of the ASCR
Rima Glottidis Segmentation by Thresholding Using Graph Cuts

We proposed a new segmentation method base on thresholding for detection rima glottidis. A proper search for glottis is very important for further analysis of the features.

Novozámský, Adam
Ústav teorie informace a automatizace, 2012

Source Camera Identification Based on PRNU Invariant to Zoom
Novozámský, Adam
2011 - English
In experiments with compact cameras, we found that the resulting PRNU is changing when we used the zoom in camera. The aim of this paper is analyze these changes and propose a methodology of the detection PRNU of compact cameras with zoom. Keywords: image forensics; PRNU; source camera identification Available at various institutes of the ASCR
Source Camera Identification Based on PRNU Invariant to Zoom

In experiments with compact cameras, we found that the resulting PRNU is changing when we used the zoom in camera. The aim of this paper is analyze these changes and propose a methodology of the ...

Novozámský, Adam
Ústav teorie informace a automatizace, 2011

Modeling multivariate volatility using wavelet-based realized covariance estimator
Baruník, Jozef; Vácha, Lukáš
2011 - English
Abstract. Study of the covariation have become one of the most active and successful areas of research in the time series econometrics and economic forecasting during the recent decades. Our work brings complete theory for the realized covariation estimation generalizing current knowledge and bringing the estimation to the time-frequency domain for the first time. The results generalize the popular realized volatility framework by bringing the robustness to noise as well jumps and ability to measure the realized covariance not only in time but also in frequency domain. Noticeable contribution is brought also by the application of the presented theory. Our time-frequency estimators bring not only more efficient estimates, but decomposes the realized covariation into arbitrarily chosen investment horizons. Results thus bring better understanding of the dynamics of dependence between the stock markets. Keywords: multivariate realized volatility; covariation; jumps; wavelets Available at various institutes of the ASCR
Modeling multivariate volatility using wavelet-based realized covariance estimator

Abstract. Study of the covariation have become one of the most active and successful areas of research in the time series econometrics and economic forecasting during the recent decades. Our work ...

Baruník, Jozef; Vácha, Lukáš
Ústav teorie informace a automatizace, 2011

Using indicators of ecological stability in stochastic programming
Houda, Michal
2011 - English
When building bigger construction the EU law impose the so-called EIA process - evaluation of possible influences of the construction on the environment and population health, grouped into several categories. Outputs of the EIA process are recommendations to the investors compensating the negative impacts of the constructions by additional arrangements. In our contribution we develop an innovative approach to model the expenses devoted to obey the EIA rules by stochastic programming tools: especially, we represent uncertainty in parameters by their probabilistic distributions, and subjective utility function representing the ecological demands is modelled via so-called indicators of ecological stability. The model takes into account budget limitations, several legislative obligations, and other ecological aspects; the goal is to help choose the optimal compensating constructions and arrangements. The resulting stochastic programming model is seen as parallel to V@R problem. Keywords: EIA process; indicator of ecological stability; stochastic programming; value-at-risk model Available at various institutes of the ASCR
Using indicators of ecological stability in stochastic programming

When building bigger construction the EU law impose the so-called EIA process - evaluation of possible influences of the construction on the environment and population health, grouped into several ...

Houda, Michal
Ústav teorie informace a automatizace, 2011

Comparison of Nonlinear Observers for Underactuated Mechanical Systems
Anderle, Milan; Čelikovský, Sergej
2010 - English
This paper provides the comparison of nonlinear observers for underactuated mechanical systems with aplication to Acrobot walking. Namely, it aims to compare a reduced observer for the Acrobot angular velocities based on the respective angles measurements with a observer for the Acrobot angular velocity and angle based on the other angular velocity and angle measurement and then to combine this observers with the earlier developed full state feedback controllers. For the Acrobot it is not possible to measure the angle between its stance leg and the surface directly because this angle is underactuated. One possibility of measuring this angle is using laser beam sensor and then computation the stance angle from that distance. Main disadvantage of this approach is the high price of the laser beam sensor. The other observer is based on angular velocity of stance leg measurement using the digital gyroscope. Keywords: observer; Underactuated mechanical systems; Walking robots Available at various institutes of the ASCR
Comparison of Nonlinear Observers for Underactuated Mechanical Systems

This paper provides the comparison of nonlinear observers for underactuated mechanical systems with aplication to Acrobot walking. Namely, it aims to compare a reduced observer for the Acrobot ...

Anderle, Milan; Čelikovský, Sergej
Ústav teorie informace a automatizace, 2010

A generalization of Takens’ Theorem
Augustová, Petra; Beran, Zdeněk
2010 - English
We give a partial generalization of the Takens’ Embedding Theorem in the case of time-irregular samples and we derive properties of the sampling function. Moreover the result is applied to the problem of embedding of a homeo/diffeomorphism into symbolic dynamical system with chaotic behavior. Příspěvek zobecňuje Takensovu větu o vložení pro nestejnoměrné časové kroky a odvozuje vlastnosti samplovací funkce. Výsledek je poté aplikován na problém vložení homeo/difeomorfismu do symbolického dynamického systému s chaotickým chováním. Keywords: Takens' Theorem; continuous flows; symbolic dynamics Available at various institutes of the ASCR
A generalization of Takens’ Theorem

We give a partial generalization of the Takens’ Embedding Theorem in the case of time-irregular samples and we derive properties of the sampling function. Moreover the result is applied to the ...

Augustová, Petra; Beran, Zdeněk
Ústav teorie informace a automatizace, 2010

What does the wavelet analysis tell us about the Central European stock markets behavior during the crisis?
Vácha, Lukáš; Baruník, Jozef
2009 - English
In the proposed paper we would like to test for the different reactions of the stock markets to current financial crisis. We will focus on the Central European stock markets, namely Czech, Polish, Hungarian and compare them to German and U.S. benchmark stock markets. V článku testujeme rozdílné reakce středoevropských trhů na finanční krizi pomocí waveletové analýzy Keywords: wavelet analysis; multiresolution analysis; Central European stock markets; financial crisis Available at various institutes of the ASCR
What does the wavelet analysis tell us about the Central European stock markets behavior during the crisis?

In the proposed paper we would like to test for the different reactions of the stock markets to current financial crisis. We will focus on the Central European stock markets, namely Czech, Polish, ...

Vácha, Lukáš; Baruník, Jozef
Ústav teorie informace a automatizace, 2009

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