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Message Embedded Synchronization for the Generalized Lorenz System and Its Use for Chaotic Masking
Čelikovský, Sergej; Lynnyk, Volodymyr
2013 - anglický
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.
Klíčová slova:
chaos synchronization; secury encryption
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Characteristics of the Chen Attractor
Augustová, Petra; Beran, Zdeněk
2013 - anglický
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.
Klíčová slova:
chaotic dynamical system; Lorenz system; Chen system
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Odhalování kopií pomocí matematického zpracování obrazu, část I: teoretická východiska a princip metody
Blažek, Jan; Hradilová, J.; Zitová, Barbara; Kamenický, Jan
2012 - český
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.
Klíčová slova:
Perspective transformation; perspective; image difference; graphical software
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Rima Glottidis Segmentation by Thresholding Using Graph Cuts
Novozámský, Adam
2012 - anglický
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.
Klíčová slova:
video imaging; vocal chords; videokymography
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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.
Source Camera Identification Based on PRNU Invariant to Zoom
Novozámský, Adam
2011 - anglický
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.
Klíčová slova:
image forensics; PRNU; source camera identification
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Modeling multivariate volatility using wavelet-based realized covariance estimator
Baruník, Jozef; Vácha, Lukáš
2011 - anglický
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.
Klíčová slova:
multivariate realized volatility; covariation; jumps; wavelets
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Using indicators of ecological stability in stochastic programming
Houda, Michal
2011 - anglický
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.
Klíčová slova:
EIA process; indicator of ecological stability; stochastic programming; value-at-risk model
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Comparison of Nonlinear Observers for Underactuated Mechanical Systems
Anderle, Milan; Čelikovský, Sergej
2010 - anglický
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.
Klíčová slova:
observer; Underactuated mechanical systems; Walking robots
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
A generalization of Takens’ Theorem
Augustová, Petra; Beran, Zdeněk
2010 - anglický
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.
Klíčová slova:
Takens' Theorem; continuous flows; symbolic dynamics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
What does the wavelet analysis tell us about the Central European stock markets behavior during the crisis?
Vácha, Lukáš; Baruník, Jozef
2009 - anglický
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
Klíčová slova:
wavelet analysis; multiresolution analysis; Central European stock markets; financial crisis
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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, ...
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