Christos Volos

Aristotle University of Thessaloniki | AUTH · Laboratory of Nonlinear Systems - Circuits & Complexity (LaNSCom), Department of Applied and Environmental Physics

Chaotic systems are nonlinear dynamical systemswhich are very sensitive to even small changes in the initial conditions. The control of chaotic systems is to design state feedback control laws that stabilize the chaotic systems around the unstable equilibrium points. This work derives a general result for the global chaos control of novel chaotic s...

A new memristive system is presented in this paper. The peculiarity of the model is that it does not display any equilibria and exhibits periodic, chaotic, and also hyperchaotic dynamics in a particular range of the parameters space. The behavior of the proposed system is investigated through numerical simulations, such as phase portraits, Lyapunov...

In this paper a new no-equilibrium hyperchaotic system is proposed by adding a tiny perturbation to a known hyperchaotic system with a line equilibrium. The fundamental dynamical properties of the new system are discovered including Lyapunov exponents, bifurcation diagram, Poincaré map and limit cycles. In addition, an electronic circuit emulating...

This paper introduces a new no-equilibrium chaotic system that is constructed by adding a tiny perturbation to a simple chaotic flow having a line equilibrium. The dynamics of the proposed system are investigated through Lyapunov exponents, bifurcation diagram, Poincaré map and period-doubling route to chaos. A circuit realization is also represent...

Antimonotonicity, i.e. forward period-doubling bifurcation sequences followed by reverse period-doubling sequences, as a parameter is varied in a monotone way, is observed in a FitzHugh – Nagumo type circuit, with a nonlinear resistor, which has a smooth cubic characteristic. The FitzHugh – Nagumo type electrical nonlinear oscillators simulate neur...

https://www.mdpi.com/journal/electronics/special_issues/1U9840AGGS The aim of this Special Issue is to advance the developments on security-related applications of chaotic systems. The topics span any research related to addressing the use of chaotic systems in information masking, encryption, cryptanalysis, secure communications, as well as hard...

https://dergipark.org.tr/en/pub/chaos/issue/77246

The Journal of Innovative Applied Mathematics and Computational Sciences (JIAMCS) is an online open access, peer-reviewed semiannual international journal published by the University Center Abdelhafid Boussouf, Mila, Algeria. The journal publishes high-quality original research and review papers from various fields related to applied mathematics, s...

In this work, a family of piecewise chaotic maps is proposed. This family of maps is parameterized by the nonlinear functions used for each piece of the mapping, which can be either symmetric or non-symmetric. Applying a constraint on the shape of each piece, the generated maps have no equilibria and can showcase chaotic behavior. This family thus...

http://danoc.physics.auth.gr/ Days of Applied NOnlinearity and Complexity (DANOC) is a two days online conference that intends to advance the discussion about the recent developments in nonlinearity and complexity, to creatively link applications and theory, tο explore the edge between different nonlinear scientific fields.

In this work, the design and implementation of an autonomous mobile robot that can cover given workspaces, is presented. The motion commands are produced by a bit sequence, which is created from the combination, through an XOR function, of two separate chaotic random bitstreams. The implementation of the proposed method is performed by a robotic pl...

https://www.youtube.com/@lanscom7572

https://dergipark.org.tr/en/pub/chaos/issue/75756

The discrete system serves an important role in mimicking collective dynamics found in continuous dynamical systems, which are relevant to many realistic natural and artificial systems. To investigate the dynamical transition of a discrete system, we employ three-dimensional sinusoidal discrete maps with an additional self feedback factor. Specific...

In this work, a chaotification technique is proposed for increasing the complexity of chaotic maps. The technique consists of adding the remainder of multiple scalings of the map’s value for the next iteration, so that the most- and least-significant digits are combined. By appropriate parameter tuning, the resulting map can achieve a higher Lyapun...

Over the last decade the use of chaos theory has been expanding to a plethora of applications related to engineering, physics, economics, lasers and communications. From the above, chaos based encryption and secure communications are among the most prominent ones. In these fields, chaotic systems are used as a deterministic source of entropy, in or...

A key challenge for drug dosing schedules is the ability to learn an optimal control policy even when there is a paucity of accurate information about the systems. Artificial intelligence has great potential for shaping a smart control policy for the dosage of drugs for any treatment. Motivated by this issue, in the present research paper a Caputo–...

In this chapter, the construction of an efficient method for a fast and complete scanning of a given area is presented. An additional aspect is the insertion of FitzHugh–Nagumo chaotic system in order to create random-like motions. Then, a modulo operator was used in the production of the necessary motion commands. For further improvement of the pr...

In this paper, a new chaotic memristor system is developed based on a well-known nonlinear circuit. By replacing the nonlinear positive conductance of Shinriki's circuit with a memristor emulator, the new simple chaotic circuit can reduce the number of active elements and reduce power consumption. An analysis of equilibria and stability, dissipativ...

The discipline of Deep Learning has been recognized for its strong computational tools, which have been extensively used in data and signal processing, with innumerable promising results. Among the many commercial applications of Deep Learning, Music Signal Processing has received an increasing amount of attention over the last decade. This work re...

https://dergipark.org.tr/en/pub/chaos/issue/73767

Many drawbacks in chaos-based applications emerge from the chaotic maps' poor dynamic properties. To address this problem, in this paper a chaotification model based on modulo operator and secant functions to augment the dynamic properties of existing chaotic maps is proposed. It is demonstrated that by selecting appropriate parameters, the resulti...

A chaotic navigation algorithm is designed for an autonomous agent, that has the objective of exploring a given area, whilst moving unpredictably. The algorithm uses the Renyi map as a randomness source to generate the orientation of the robot and the direction it can move. There are eight possible directions, but the motion is limited to only thre...

This topical issue collects contributions of recent achievements and scientific progress related to the collective behavior of nonlinear dynamical oscillators. The individual papers focus on different questions of present-day interest in this topic.

In 1971, Chua suggested that there should be a fourth electrical component in addition to resistor, capacitor and inductor. This new component was proposed to be called “memristor”. Due to lack of commercially available memristors many emulators are mainly used in nonlinear circuits. Also, the memristance functions are used in many dynamical system...

https://dergipark.org.tr/en/pub/chaos/issue/73033

In this work, we consider polynomial approximations of the sine map, which is known to be chaotic. The dynamics of the maps obtained for different orders of approximations are studied using classical tools. Comparison of the behavior is made through common bifurcation diagrams, 0–1 test results, Lyapunov exponent diagrams and approximate entropy di...

Currently, chaotic cryptography is mainly concentrated on image encryption. Once-popular stream-encryption algorithms, e.g., textual data, are now rarely considered. This article studies how chaotic image-encryption algorithms can be used to encrypt text. The proposed approach to this problem consists of two stages: in the first stage, the text mes...

This Issue is dedicated to some selected papers of the International Conference on Mathematics and Applications (ICMA'2021), held on December 7-8, 2021, at Blida 1 University, Algeria. Guest Editor: Mohammed Hachama Associet Editors: - Benbachir Maamar -Redouane Boudjemaa ARK: https://n2t.net/ark:/49935/jiamcs.v2i2 Published: 10-09-2022

This paper proposes a new one-dimensional chaotic map. The map consists of a coupling between two hyperbolic tangent terms, where the second term is delayed, to avoid dynamical degradation. The map is studied through computation of its bifurcation diagrams and Lyapunov exponent diagrams and is shown to have constant chaotic behavior for almost all...

Today, one of the most studied phenomena of nonlinear dynamical systems is Chaos [...]

In this work, a chaotification technique is proposed that can be used to enhance the complexity of any one-dimensional map by adding the remainder operator to it. It is shown that by an appropriate parameter choice, the resulting map can achieve a higher Lyapunov exponent compared to its seed map, and all periodic orbits of any period will be unsta...

Chaos theory is currently one of the most fascinating fields in modern science, revolutionizing our understanding of organization and patterns in nature [...]

This issue is dedicated to the memory of Prof. Tenreiro Machado. https://dergipark.org.tr/en/pub/chaos/issue/64884

A novel approach to the physical memristor’s behavior of the KNOWM is presented in this work. The KNOWM’s memristor’s intrinsic feature encourages its use as a nonlinear resistor in chaotic circuits. Furthermore, this memristor has been shown to act like a static nonlinear resistor under certain situations. Consequently, for the first time, the KNO...

In 1976, Prof. Leon Chua proposed that a physical thermistor can be modeled as a memristive device, which can be used as a nonlinear element in chaotic circuits. In this direction, an autonomous circuit with two passive elements (inductor and capacitor), a nonlinear resistor, and a thermistor, which plays the role of a nonlinear locally active memr...

This work introduces a novel chaotic map defined by composition of the quantum logistic map and the sine map. The dynamic behavior of this map is thoroughly investigated and is shown to be more complex than that of the original quantum logistic map. Sequentially, a PRBG is defined using the values of the introduced map, the validity of which is det...

During the fall semester of 2021-2022 academic year, a seminar series on ’Chaotic Cryptography’ was delivered at the Department of Computer Aided Design (CAD), St. Petersburg Electrotechnical University ’LETI’, Russia. The seminar aimed at introducing students to state of the art research topics that connect chaos theory to various applications rel...

This paper investigates the issue of chaos-based image encryption. A new one-dimensional piecewise chaotic map based on the z-shaped fuzzy number is proposed and investigated, exhibiting regions of constant chaos and high Lyapunov exponent values. A pseudorandom bit generator based on the novel chaotic map is designed and successfully passes the Na...

In this paper, a novel approach of the KNOWM’s physical memristor behavior is introduced. It has been experimentally observed that this memristor, under certain conditions, can behave as a static nonlinear resistor. This inherent property of the KNOWM’s memristor prompts its use as a nonlinear reistor in chaotic circuits. Therefore, in this work, f...

In the present study, the simulation of an immunotherapy effect for a known dynamical system, that describes the process for avascular, vascular, and metastasis tumor growth based on a chemical network model, has been presented. To this end, square signals of various amplitudes have been used, to model the effect of external therapy control, in ord...

Chaos-based secure communications is a broadly studied field in nonlinear dynamics. Such technique is traditionally based on chaotic synchronization between master and slave systems implemented as the transmitter and receiver. A common way to encode the message is switching the bifurcation parameters of the master system, which leads to perturbatio...

In the research on chaotic systems, which are used for cryptography and secure communication schemes, a key characteristic is the introduction of novel chaotic systems, usually by adding complexity to the existing ones in order to ensure security. In this direction, this chapter proposes novel chaotic systems, which are the composition of fuzzy num...

As shown by Leon Chua in 1976 a physical thermistor can be modeled as a memristive device. Later, Ginoux et al. designed a circuit with four elements, an inductor, a capacitor, a nonlinear resistor, and a thermistor, which plays the role of a nonlinear locally active memristor. In this work, the aforementioned autonomous circuit is modified to a no...

A novel memristive oscillator with infinite equilibria is proposed in this paper. The oscillator has six lines of equilibria, which make it different from known ones. Interestingly, the oscillator displays chaos and attractive features. Implementation of the oscillator via analog components is presented to verify its feasibility.

This work addresses the problem of adaptive observer design for nonlinear systems satisfying incremental quadratic constraints. The output of the system includes nonlinear terms, which puts an additional strain on the design and feasibility of the observer, which is guaranteed under the satisfaction of an LMI, and a set of algebraic constraints. A...

This work studies the problem of chaos-based image encryption. First, a generalization of the 1D chaotic map proposed by (Talhaoui et al. in The Visual Computer, pp 1–11, 2020) [8] is constructed and studied. The generalized map showcases regions of constant chaotic behaviour, similar to the original map. Based on the new map, a statistically secur...

Chaos Theory and Applications (March 2022 - Volume 4 - Issue 1) https://dergipark.org.tr/en/pub/chaos/issue/63571 ----------- 1) Jun MA. "Chaos Theory and Applications：The Physical Evidence, Mechanism are Important in Chaotic Systems. " 2) Burak ARICIOĞLU, Sezgin KAÇAR. "Circuit Implementation and PRNG Applications of Time Delayed Lorenz System....

As applications of chaotic systems span numerous fields in engineering, physics, encryption, communications, and robotics, there is a continuing need to introduce novel chaotic systems and study their applicability in the aforementioned fields. In this chapter, a four-dimensional hyperchaotic system is introduced and analyzed through calculation of...

The study of the chaotic dynamics in fractional-order discrete-time systems has received great attention over the last years. Some efforts have been also devoted to analyze fractional maps with special features. This paper makes a contribution to the topic by introducing a new fractional map that is characterized by both particular dynamic behavior...

In this paper, a new 4D hyperchaotic nonlinear dynamical system with two positive Lyapunov exponents is presented. Exhaustive dynamic analyses of the novel hyperchaotic model using several dynamical studies are described. The dynamics of the system considered are first investigated analytically and numerically to explore phenomena and the selection...

The article discusses the possibility of synchronizing adaptive discrete chaotic maps through the control of the symmetry coefficient. Since a change in the symmetry coefficient in symmetric chaotic maps possesses a much less influence on the system oscillation mode than a change in nonlinearity parameters, we assume that the synchronization of suc...

Since the variable-order fractional systems show more complex characteristics and more degrees of freedom due to time-varying fractional derivatives, we introduce a variable-order fractional Hopfield-like neural network in this paper. First, the properties and dynamical behavior of the system are studied. The variable-order derivative’s effects on...

This work studies the problem of chaos-based text encryption. A novel 1-D chaotic map is proposed and studied that exhibits regions of constant chaos, and high values of Lyapunov exponent. Based on the new chaotic map, a pseudorandom bit generator is designed that passes all the National Institute of Standards and Technology (NIST) statistical test...

Recent intensive simulations have uncovered remarkable phenomena in stability diagrams of classical oscillators, for instance, quint points, parameter rings, and chiral structures of non-quantum origin. So far, their experimental observation has remained elusive. Here, using a simple electronic circuit, we report the experimental detection of five...

It has been proved that the permanent-magnet synchronous generator system displays a variety of chaotic phenomenon when its parameters or external inputs satisfy a certain condition, and it would degrade the efficiency of the PMSG system dramatically. This paper studies the problem of control and synchronization of the chaotic PMSG system which con...

In the last decades, chaotic systems and their applications have received significant attention [1–13]. When discovering chaotic systems, equilibrium points are studied seriously because of their important role [12, 14–16]. Conventional chaotic systems, especially 3-D chaotic systems, like Lorenz system [17], Rössler system [18], Arneodo system [19...

Chaotic cryptography is a promising area for the safe and fast transmission, processing, and storage of data. However, many developed chaos-based cryptographic primitives do not meet the size and composition of the keyspace and computational complexity. Another common problem of such algorithms is dynamic degradation caused by computer simulation w...

Over the last years, distributed consensus tracking control has received a lot of attention due to its benefits, such as low operational costs, high resilience, flexible scalability, and so on. However , control methods that do not consider faults in actuators and control agents are impractical in most systems. There is no research in the literatur...