Dual-hop transmissions with fixed-gain relays over Generalized-Gamma fading channels

In this paper, a study on the end-to-end performance of dual-hop wireless communication systems equipped with fixed-gain relays and operating over Generalized-Gamma (GG) fading channels is presented. A novel closed form expression for the moments of the end-to-end signal-to-noise ratio (SNR) is derived. The average bit error probability for coherent and non-coherent modulation schemes as well as the end-to-end outage probability of the considered system are also studied. Extensive numerically evaluated and computer simulations results are presented that verify the accuracy of the proposed mathematical analysis.\u

Underwater Optical Wireless Communication Systems: A Concise Review

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

Synchronization Phenomena in Coupled Birkhoff-Shaw Chaotic Systems Using Nonlinear Controllers

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

Research for a Teaching Approach: An Example of Addressing the High School Students’ Conceptual and Reasoning Difficulties in the Study of Direct Current Simple Electric Circuits

With this work we aim at presenting a research on high school students’ (ages 16-17, Greece 2015-2017) understanding into the study of basic direct current (DC) circuits. Studies on this subject in over the world have contributed to a rich research base. Students’ conceptual and reasoning difficulties are presented and analyzed, aiming at the development of methodologies and teaching approaches, accompanied by instructional material to resolve them. The difficulties experienced by these students indicate a significant discrepancy between their conceptions and the scientific view. To address these difficulties, the design and the development of two types of programs were chosen. The first is based on educational models in the laboratory and the second consists of auxiliary courses and educational material for its simultaneous use in classroom teachings. The conclusion is that the existing literature is confirmed and enriched with new findings, while a different teaching approach accompanied by appropriate educational material seems to help the address of the conceptual and reasoning difficulties

A Physics and Engineering Lab for Primary Teachers at CERN

Major international Research Centers run Continuous Professional Development Courses for Primary Teachers on Science, Technology, Engineering, and Mathematics activities and experiments. The projects and the hands-on workshops inspire teachers through cutting-edge science and technology to influence and spread the research culture to their students in return. The STEM lab in this paper was presented in a CERN program for Greek primary educators teaching Physics and IT. The research focuses on the teachers' electromagnetic lab and was tested by students in the classroom environment for two subsequent years. The results of both labs, of teachers and students, are examined regarding their basic understanding of Physics Laws and scientific research.