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We investigate the transition between oscillatory and amplitude death (AD) states and the existence of death islands in intrinsic time-delayed chaotic oscillators under the simultaneous presence of diffusive (direct) and environmental (indirect) coupling. Studies in two-parameter space reveal that depending upon parameters and intrinsic time delays the coupling can bring the oscillators to the AD state and again can revive the system to oscillatory states, thus creating death islands in parameter space; this observation is in sharp contrast to the death scenario of non-delayed oscillators under the same coupling scheme where no death islands are formed. Using a linear stability analysis, we derive the explicit conditions for different transition scenarios. We use a continuation package for the time-delay systems to precisely identify the zone of AD and its islands and their origin. We also extend our study to the network of oscillators and show that the observed results are general for a large number of oscillators, too. Finally, we demonstrate our results experimentally to verify the analytical and numerical findings.

We investigate analytically and numerically coupled lattices of chaotic maps where the interaction is non-local, i.e., each site is coupled to all the other sites but the interaction strength decreases exponentially with the lattice distance. This kind of coupling models an assembly of pointlike chaotic oscillators in which the coupling is mediated by a rapidly diffusing chemical substance. We consider a case of a lattice of Bernoulli maps, for which the Lyapunov spectrum can be analytically computed and also the completely synchronized state of chaotic Ulam maps, for which we derive analytically the Lyapunov spectrum.

A class of non-diffusively coupled complex networks consisting of nodes of different dimensions is studied, in which the internal time delays are different from the coupling delays. Proper adaptive controllers are proposed for the stabilization and function matrix projective synchronization of such complex networks, respectively. The symmetric or diffusive conditions for the coupling matrices are not required. Finally, the results are applied to complex networks of chaotic oscillators showing the effectiveness of the proposed controllers.

Akgul, Akif/0000-0001-9151-3052; istanbullu, ayhan/0000-0002-7066-4238 WOS: 000372543600003 There has recently been an increase in the number of new chaotic system designs and chaos-based engineering applications. In this study, since homoclinic and heteroclinic orbits did not exist and analyses like Shilnikov method could not be used, a 3D chaotic system without equilibrium points was included and thus different engineering applications especially for encryption studies were realized. The 3D chaotic system without equilibrium points represents a new different phenomenon and an almost unexplored field of research. First of all, chaotic system without equilibrium points was examined as the basis and electronic circuit application of the chaotic system was realized and oscilloscope outputs of phase portraits were obtained. Later, chaotic system without equilibrium points was modelled on Labview Field Programmable Gate Array (FPGA) and then FPGA chip statistics, phase portraits and oscilloscope outputs were derived. With another study, VHDL and RK-4 algorithm were used and a new FPGA-based chaotic oscillators design was achieved. Results of Labview-based design on FPGA- and VHDL-based design were compared. Results of chaotic oscillator units designed here were gained via Xilinx ISE Simulator. Finally, a new chaos-based RNG design was achieved and internationally accepted FIPS-140-1 and NIST-800-22 randomness tests were run. Furthermore, video encryption application and security analyses were carried out with the RNG designed here.

The hardware realization of a chaotic communication system from the description of continuous-time multi-scroll chaotic oscillators is introduced herein by using field-programmable gate arrays (FPGA). That way, two multi-scroll chaotic oscillators generating 2 and 6 scrolls are synchronized by applying Hamiltonian forms and observer approach. The synchronized master-slave topology is used to implement a secure communication system by adding chaos to an image at the transmission stage and by subtracting chaos at the recover stage. The FPGA realization begins by applying numerical methods to solve the system of equations describing the whole chaotic communication system. Further, the replacement of multipliers by single constant multiplication blocks reduces the use of hardware resources and accelerates the processing time as well. Using chaotic oscillators with 2 and 6 scrolls, three kinds of images are processed: one in black and white and two in gray tones. Finally, the experimental results confirm the appropriateness on realizing chaotic communication systems for image processing by using FPGAs.

The effect of parameter mismatch (diversity) taken from two-point distribution is studied numerically and theoretically in globally coupled Rossler chaotic systems. Two cases including mixed populations consisting of elements with different timescales and attractors are considered. In these two cases, the probability p of two-point distribution, which acts as an asymmetrical coupling on the system, plays a crucial role in determining the evolution of systems, and the rich dynamical phenomena are observed, especially for amplitude death (AD). The relationships between various dynamics are also discussed.

When two different chaotic oscillators are coupled, generalized synchronization can occur. It may imply a very complicated relation between the states of drive and response systems. We propose a method that can be used to detect and characterize the generalized synchronization in modulated time-delayed systems. Using Krasovskii–Lyapunov theory, sufficient condition for generalized synchronization is derived. The proposed technique has been applied to synchronize prototype and Ikeda models by numerical simulation.