Frequency response function identification using fused filament fabrication-3D-printed embedded ArUco markers

The assessment of modal components is a fundamental step in structural dynamics. While experimental investigations are generally performed through full-contact techniques, using accelerometers or modal hammers, this research proposes a non-contact Frequency Response Function identification measurement technique based on ArUco square fiducial markers displacement detection. A video of the phenomenon to be analyzed is acquired, and the displacement is measured through markers, using a dedicated tracking algorithm. The proposed method is presented using a harmonically excited fused filament fabrication-3D-printed flexible structure, equipped with multiple embedded-printed markers, whose displacement is measured with an industrial camera. Comparison with numerical simulation and an established experimental approach is finally provided for the results validation

Performance assessment of medical and non-medical CPAP interfaces used during the COVID-19 pandemic

Background: At the beginning of 2020, a high number of COVID-19 cases affected Italy in a short period, causing a difficult supply of medical equipment. To deal with the problem, many healthcare operators readapted different masks to medical devices, but no experiment was conducted to evaluate their performance. The aims of our study were: to assess the performances of three masks and a CPAP helmet in their original configuration and after modifications, in the maintenance of mean pressure and half-amplitude variations using different PEEP valves and to analyse the impact of antibacterial (AB) or antibacterial-viral (ABV) pre-valve PEEP filters on the effective PEEP delivered to the patients. Four pressure ports were installed on each mask (three on helmet), mean values and half amplitudes of pressure were recorded. Tests were performed with any, AB, ABV filter before the PEEP valve. CPAP helmet was the most efficient interface producing more stable mean pressure and less prominent half-amplitude variations but the non-medical masks, especially after the modifications, maintained a stable mean pressure value with only a moderate increase of half-amplitude. The use of AB and ABV filters, produced respectively an increase of 2,23% and 16.5% in mean pressure, compared to no filter condition. CPAP helmet is the most reliable interface in terms of detected performance, but readapted masks can assure almost a similar performance. The use of ABV filters before the PEEP valve significantly increases the detected mean pressure while the AB filters have almost a neutral effect