Abstract. In the last years disturbances in VLF/LF radio signals related to seismic activity have been presented. The radio data were collected by receivers located on the ground or on satellites. The ground-based research implies systematic data collection by a network of receivers. Since 2000 the "Pacific VLF network", conducted by Japanese researchers, has been in operation. During 2008 a radio receiver was developed by the Italian factory Elettronika (Palo del Colle, Bari). The receiver is equipment working in VLF and LF bands. It can monitor 10 frequencies distributed in these bands and, for each of them, it saves the power level. At the beginning of 2009, five receivers were made for the realization of the "European VLF/LF Network"; two were planned for Italy and one for Greece, Turkey and Romania, respectively. In 2010 the network was enlarged to include a new receiver installed in Portugal. In this work, first the receiver and its setting up in the different places are described. Then, several disturbances in the radio signals related to the transmitters, receivers, meteorological/geomagnetic conditions are presented and described.

Extraordinary wave transmission is demonstrated through a double-negative composite comprised of a negative-permeability array of double split ring resonators and a negative-permittivity array of plasma discharge tubes at microwave frequencies. A transmission peak emerges in a double-negative band and controlling the electron density inside the plasma tubes dynamically regulates the transmission properties. By performing experiments and theoretical calculations, we verify that the composite permits wave propagation with negative permeability and controllable permittivity, which indicates that a tunable negative-refractive-index device is achieved.

This paper presents an optimization procedure for the definition of the gas turbine load profile during the hot start-up of Combined Cycle Power Plants (CCPP). First a dynamic model of CCPP is briefly described, together with its implementation in the Modelica language. Then, an identification procedure is developed to determine a simplified model to be implemented in Matlab/Simulink and to be used for the solution of the optimization problem. This simplified model is built by interpolating a number of linear estimated models with local validity. The load profile is assumed to be described by a suitable function, whose parameters are optimized by solving a minimum time problem subject to the plant (simulator) dynamics and to a number of constraints to be imposed on the main plant variables, such as temperatures, pressures, thermal and mechanical stresses. A number of simulation experiments is reported to witness the performance of the proposed approach.

We describe the experimental generation of a deep attenuation band in a finite size (7 × 7) two-dimensional photonic crystal constructed from an array of gaseous plasma columns. The attenuation band, centered at approximately 6 GHz, is due to the lattice resonance between the localized surface plasmon modes at the edge of the plasma columns and the internal Bragg fields of the photonic crystal. The attenuation band has a nearly 40 dB floor with Q ≈ 1. Enhancements are seen in the extinction of normal incidence transverse electric waves when the localized surface plasmon modes of the plasma columns are shifted into the vicinity of the photonic crystal Bragg resonances. Simulations and experiments are in reasonable agreement and confirm the appearance of a Fano-like profile with deep and broad extinction bands. The broadening of the spectra as surface plasmon modes come into coincidence with Bragg gaps suggests that the Bragg fields couple strongly into the radiating dipoles to drive enhanced damping of the photonic crystal resonance.

Since 2009 a network of VLF (20 -60 kHz) and LF (150 -300 kHz) radio receivers is operating in Europe in order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 the network was formed by nine receivers, of which three are located in Italy and one is in