Hector Nistazakis

By K.P. Peppas, H.E. Nistazakis and G.S. Tombras

Part of the book: Advanced Trends in Wireless Communications

By M.P. Hanias, H.E. Nistazakis and G.S. Tombras

Part of the book: Optoelectronic Devices and Properties

By Kostas Peppas, Hector E. Nistazakis, Vasiliki D. Assimakopoulos and George S. Tombras

Part of the book: Optical Communication

By Christos K. Volos, Hector E. Nistazakis, Ioannis M. Kyprianidis, Ioannis N. Stouboulos and George S. Tombras

In this chapter, the well-known non-autonomous chaotic system, the Birkhoff-Shaw, which exhibits the structure of beaks and wings, typically observed in chaotic neuronal models, is used in a coupling scheme. The Birkhoff-Shaw system is a second-order non-autonomous dynamical system with rich dynamical behaviour, which has not been sufficiently studied. Furthermore, the master-slave (unidirectional) coupling scheme, which is used, is designed by using the nonlinear controllers to target synchronization states, such as complete synchronization and antisynchronization, with amplification or attenuation in chaotic oscillators. It is the first time that the specific method has been used in coupled non-autonomous chaotic systems. The stability of synchronization is ensured by using Lyapunov function stability theorem in the unidirectional mode of coupling. The simulation results from system’s numerical integration confirm the appearance of complete synchronization and antisynchronization phenomena depending on the signs of the parameters of the error functions. Electronic circuitry that models the coupling scheme is also reported to verify its feasibility.

Part of the book: Nonlinear Systems

By Lydia K. Gkoura, George D. Roumelas, Hector E. Nistazakis, Harilaos G. Sandalidis, Alexander Vavoulas, Andreas D. Tsigopoulos and George S. Tombras

Underwater optical wireless communications (UOWC) have gained a considerable interest during the last years as an alternative means for broadband inexpensive submarine communications. UOWC present numerous similarities compared to free space optical (FSO) communications or laser satellite links mainly due to the fact that they employ optical wavelengths to transfer secure information between dedicated point‐to‐point links. By using suitable wavelengths, high data rates can be attained. Some recent works showed that broadband links can be achieved over moderate ranges. Transmissions of several Mbps have been realized in laboratory experiments by employing a simulated aquatic medium with scattering characteristics similar to oceanic waters. It was also demonstrated that UOWC networks are feasible to operate at high data rates for medium distances up to a hundred meters. However, it is not currently available as an industrial product and mainly test‐bed measurements in water test tanks have been reported so far. Therefore, extensive research is expected in the near future, which is necessary in order to further reveal the “hidden” abilities of optical spectrum to transfer broadband signals at higher distances. The present work summarizes the recent advances in channel modeling and system analysis and design in the area of UOWC.

Part of the book: Turbulence Modelling Approaches