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The detection of H₂ concentrations in concentrations undetectable by the conventional detection method of surface acoustic wave (SAW) sensors based on frequency shift, by correlating analyte presence with Fourier spectra components.

Fast Fourier Transform (FFT) and autocorrelation analysis of phase noise in a SnO2-coated SAW sensor was performed. Fourier spectra were obtained by FFT from the SAW sensor resonance frequency instability, in the absence of analyte, and for H₂ concentrations between 0.08 and 0.4 per cent.

All analyte concentrations are below the sensor limit of detection, which is 0.8 per cent for H₂. Although these analyte concentrations caused no significant change in the resonance frequency of the SAW resonator, the FFT spectra presented several modifications, namely, the appearance of a new peak and the decrease of randomness. The authors consider that the effect is because of the chaotic behavior of the temporal dependence of the SAW resonance frequency. This explanation is substantiated by the decrease observed in the SAW oscillator autocorrelation function, which is an indication for a chaotic behavior.

As chaotic systems are extremely sensitive to perturbation, measurement methods based on chaos diagnosis could potentially greatly improve the SAW detection.

Fourier spectra components were correlated with analyte presence in concentrations undetectable by the conventional SAW detection method based on frequency shift.

The aim of this paper is to address the value co-creation and co-production theories in public administration (P.A.) sector, particularly when public administration communicates with citizens during catastrophes, to provide a state of the art of the theoretical approach and its evolution.

Authors collected data between August and October 2017 from Scopus and Sciencedirect, looking for journals publications from 2010 to 2017, considering only articles containing in the abstract, title and keywords the following combinations: value co-creation AND P.A., value coproduction AND “P.A., crisis communication” AND “P.A.”.

By using three different keywords it appeared that the results of the individual topic contain results of all the other topics as well. It means that searching “value co-creation” AND “P.A.” appeared contributions of “value co-production” and “crisis communication” and vice-versa. The second reached result was to inscribe the theoretical approach of value co-creation into the interaction between citizens and public administration.

Firstly, concentrating the research only on most recent articles from peer reviewed journals tends to exclude conference paper and other eventual contributions. Secondly, because the SLR has been conducted by searching with the keywords, only articles, which appeared in relation to the keywords connection in those databases, have been selected, excluding those papers closed to the themes, but classified under other terms.

This work value consists of trying to contextualize crisis communication during natural disasters in a theoretical context different from that which literature usually considers, i.e. value co-creation between public administration and citizens.