Metastructures in a sensor-actuator configuration: the practical issues in bandgap generation

Undesired vibrations are one of the most significant sources of error in any type of mechatronic system or component. The emerging field of elastic (locally resonant) metamaterials offers a viable solution to successfully suppress these by generating bandgaps in both resonant and non-resonant regions. In this thesis, metamaterials in a sensor-actuator configuration using piezoelectric transducers are employed to generate vibration attenuation regions in beam-like structures. The main contribution of this thesis consists in studying the practical issues involved in the experimental implementation of such metamaterial architectures, often overlooked in the literature. To this aim, parasitic dynamics such as time delay and RC roll-off characteristics of piezoelectric transducers are considered, and their influence on controller choice is evaluated. The research was conducted using full model simulations in SPACAR and an experimental setup. The RC roll-off characteristic of piezoelectric transducers was found to be significant in limiting the bandgap generation capabilities of the system in non-resonant regions. The reason for this was the added phase caused by the parasitic effect, which required a reduction in controller gain for stability and ultimately reduced the bandgap performance. This was not the case for resonant bandgaps, where the phase lead was compensated by the increase in gain at the resonance. This ultimately allowed for optimal resonant bandgaps to be generated and observed. Methods to compensate for such parasitic effects are proposed and suggestions on how to implement these to attain non-resonant bandgaps are made.Mechanical Engineering | Mechatronic System Design (MSD

campocasoli.org: un archivio digitale per lo studio dei fascicoli personali di internati civili stranieri nell’Italia fascista

On January 27, 2017, the international Holocaust Remembrance Day, the website www.campocasoli.org was launched. The main purpose of the site is to establish a digital archive that provides open access to over 4500 documents. The documents are part of 215 personal files of foreign civil internees listed as “foreign jews” and political internees classified as “ex Jugoslavians” and “antifascists”. The files concern Casoli’s concentration camp in the Chieti province of Abruzzo and tackle the period between 1940 and 1944, the time in which the camp was active and used by fascist administrators. The documents were stored in Casoli’s municipal archive and were systematically recorded and catalogued only in 2000. They have now been arranged on the website in a series of themed and conceptual areas that allow a differentiated and sophisticated research of the materia