The electricity market experiences pronounced short term volatility due to its peculiarities, first of all continuos load variations associated to the impossibility to profitably store electric energy. Electricity price forecast is extremely important for all market players and in particular for generating companies, that must manage their units, and the associated economic risk, in the short, medium and long term. In general, price volatility depends on a large number of parameters such as: fuel prices (often related to currency exchange rates), availability of generating units, hydro generation production, demand elasticity and variations, network congestion and management rules of any specific electricity market. This study provides an analysis of day-ahead spot market price volatility in Spain, California, UK and PJM markets. Electricity prices for the years 1999 and 2000 have been used for the study. The analysis has been carried out on the basis of an original definition of price volatility.

This paper presents the application of the Synthetic Aperture Radar (SAR) localization method for indoor positioning of UHF-RFID tags when the robot-mounted reader antenna moves alongside multiple trajectories. By properly combining the phase data associated to a set of multiple paths, the synthetic apertures along the main directions enlarge and then the localization accuracy may improve. Besides, during consecutive inventory rounds, several tag position estimates are available and they can be profitably combined to minimize the localization uncertainty. Different combination approaches are investigated to determine the best choice to improve the localization performance. The method capabilities are discussed through a numerical analysis, by considering different configurations of the multiple apertures and different sources of measurement uncertainty. Finally, the proposed localization method is validated through an experimental analysis carried out with commercial RFID hardware and a robotic wheeled walker, in an indoor scenario, by employing different types of tags. The knowledge of the reader/robot trajectory required by the SAR method is here achieved with an optical system.

This paper deals with the characterization of magnetic iron oxide nanoparticles. Pure magnetite (Fe3O4) and noble metal doped magnetite were synthesized following a new sustainable microwave-assisted method. Furthermore, an experimental analysis was carried out to investigate the chemical and magnetic properties of these new nanopowders. Morphological and chemical characteristics of the pure magnetite and magnetite modified by noble metals such as palladium, platinum and ruthenium are provided together with the relevant B-H magnetic curve. Among the adopted measurement techniques, the purity of magnetite phase was analyzed via Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD), while a Vibrating Sample Magnetometer (VSM) characterized the magnetic behavior of the nanopowder samples

In this paper, we propose the use of the electrochemical impedance spectroscopy technique for state diagnosis of electric double-layer ultracapacitors. Ultracapacitors under investigation are Maxwell BCAP 0350 and they were stressed in several ways for our study. The analyzed stress conditions include accelerated aging tests, overvoltage, and over temperature tests. Chemical and physical effects on supercapacitor materials are pointed out through a morphologic analysis implemented by means of an environmental scanning electron microscope and a chemical composition analysis obtained by means of an energy dispersive spectrometer. Consequent degradation effects are described in terms of frequency behavior of equivalent circuital parameters

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