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This paper presents an online diagnosis method for supercapacitors' aging problem. State-of-Health (SoH) estimation is an important feature since aging introduces degradation in supercapacitors' performance, which might eventually lead to their failure. SoH is usually measured by Electrochemical Impedance Spectroscopy (EIS). But, this has to be performed offline and requires interruption of the system's operation. Unlike this method, this paper presents an online diagnosis technique for supercapacitors using an extended Kalman observer as a well-known tool for its particularities and performances to study nonlinear parameters estimation. The main objective of this paper is the online State-of-Health diagnosis based on the supercapacitors aging indicators estimation. Moreover, the proposed online estimation strategy requires only voltage and current measurements, which reduces the number of sensors with respect to other methods. The effectiveness of the proposed online observer is shown through experimental results and robustness to noise is also studied. S 0018-9545 (c)

The aim of this study is to obtain high-quality zinc oxide thin films at room temperature by reactive radiofrequency (rf) magnetron sputtering in an oxygen environment. The films were deposited on glass and silicon substrates at several temperatures, ranging from ambient temperature to 400 °C. In order to have the best results at room temperature we adjusted several deposition parameters such as the O 2 /Ar gas pressure, target-substrate distance, rf power, and gas flow rate. The ZnO samples were characterized by several methods. From XRD measurements it was confirmed that ZnO films are c-axis oriented, the line width and intensity are sensitive to the variation of the growth temperature, and the best results were found at room temperature for our growth conditions. From AFM pictures it is seen that the grain size decreases when the temperature is increased to 400 °C and the surface roughness of the as-deposited films increases with the deposition temperature. All films exhibited excellent transmission (in excess of 90%) in the visible range with a steep fall off in transmission at 375 nm for the samples grown at room temperature. From the absorbance measurements the optical band-gap energy was extrapolated at about 3.25 eV, which closely agrees with the ZnO single-crystal value. Raman backscattering is used to probe the zone center phonons and evaluate the residual stress in the as-grown ZnO thin films from the position of the E 2 high mode.

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