Non-linear Lamb Waves for Locating Defects in Single-Lap Joints

A novel method based on Non-linear Lamb waves behavior and Local Defect Resonance (LDR) is proposed for locating and evaluating disbonds in Single-Lap Joints (SLJ) typically used in aerospace industry. The presence of damages/defects such as disbonds leads to the presence of sub- and super-harmonics components in the frequency response. The maximum acoustic wave-damage interaction is reached by particular excitation frequencies that enhance the Non-linear response causing LDR. The LDR frequency is experimentally evaluated through the appearance of a single subharmonic component in the frequency spectrum of signals received by piezoelectric transducer (PZT) bonded on the structure. The Non-linear properties of Lamb waves are exploited to make defects generate subharmonic waves at LDR frequency. An algorithm is implemented for damage/defect localization that is accurately obtained by knowing PZTs positions, Time of Flight (ToF) and propagation properties of subharmonics packet. Several disbonds with different dimensions are artificially reproduced on an aluminum SLJ: experimental and FE results show good accordance both in usual (single damage) and critical (multi-damage) scenario. The paper proposes a baseline-free method for the disbonds detection, characterization and localization in SLJs that uses the PZT signals without affecting adhesive interface, thus allowing for an active health monitoring

Effect of Obstacle Type and Cognitive Task on Situation Awareness and Takeover Performance in Conditionally Automated Driving

In conditionally automated driving, several factors can affect the driver’s situation awareness and ability to take over control. To better understand the influence of some of these factors, 88 participants spent 20 minutes in a conditionally automated driving simulator. They had to react to four obstacles that varied in danger and movement. Half of the participants were required to engage in a verbal cognitive non-driving-related task. Situation awareness, takeover performance and physiological responses were measured for each situation. The results suggest that obstacle movement influences obstacle danger perception, situation awareness, and response time, while the latter is also influenced by obstacle danger. The cognitive verbal task also had an effect on the takeover response time. These results imply that the driver’s cognitive state and the driving situation (e.g. the movement/danger of entities present around the vehicle) must be considered when conveying information to drivers through in-vehicle interfaces

PEGASO: a personalised and motivational ICT system to empower adolescents towards healthy lifestyles

Unhealthy alimentary behaviours and physical inactivity habits are key risk factors for major non communicable diseases. Several researches demonstrate that juvenile obesity can lead to serious medical conditions, pathologies and have important psycho-social consequences. PEGASO is a multidisciplinary project aimed at promoting healthy lifestyles among teenagers through assistive technology. The core of this project is represented by the ICT system, which allows providing tailored interventions to the users through their smartphones in order to motivate them. The novelty of this approach consists of developing a Virtual Individual Model (VIM) for user characterization, which is based on physical, functional and behavioural parameters opportunely selected by experts. These parameters are digitised and updated thanks to the user monitoring through smartphone; data mining algorithms are applied for the detection of activity and nutrition habits and this information is used to provide personalised feedback. The user interface will be developed using gamified approaches and integrating serious games to effectively promote health literacy and facilitate behaviour change

Tâche secondaire et conscience de l'environnement, une application mobile pour véhicule semi-autonome

National audienceAutonomous vehicles are developing rapidly and will lead to a significant change in the driver's role: he/she will have to move from the role of actor to the role of supervisor. Indeed, the driver will soon be able to perform a secondary task but he/she must be able to take over control in the event of a critical situation that is not managed by the autonomous system. This implies that the role of new interfaces and interactions within the vehicle is important to take into account. This article describes the design of an application that provides the driver with information about the environment perceived by his/her vehicle in the form of modules. This application is displayed as split screen on a tablet by which a secondary task can be performed. Initial tests were carried out with this application in a driving simulator. They made it possible to test the acceptance of the application and the clarity of the information transmitted. The results generally showed that the participants correctly identified some of the factors limiting the proper functioning of the autonomous pilot while performing a secondary task on a tablet.Les véhicules autonomes se développent rapidement et entraîneront un changement de rôle important chez le conducteur: ce dernier sera amené à passer du rôle d'acteur à celui de superviseur. En effet, le conducteur sera bientôt en mesure d'effectuer une tâche secondaire mais devra toutefois être capable de reprendre le contrôle dans le cas d'une situation critique non gérée par le système autonome. Ceci implique que le rôle des nouvelles interfaces et interactions au sein du véhicule est important à prendre en compte. Cet article décrit la conception d'une application transmettant au conducteur des informations relatives à l'environnement perçu par son véhicule sous forme de modules. Cette application s'affiche en partage d'écran sur une tablette grâce à laquelle une tâche secondaire peut être effectuée. De premiers tests ont été effectués avec cette application dans un simulateur de conduite. Ils ont permis de tester l'acceptation de l'application et la clarté des informations transmises. Les résultats ont globalement montré que les participants ont correctement identifié certains facteurs limitant le bon fonctionnement du pilote autonome tout en réalisant une tâche secondaire sur tablette

Post-operative acute urinary retention after greenlight laser. Analysis of risk factors from a multicentric database

Purpose: Greenlight laser is a mini-invasive technique used to treat Benign Prostatic Obstruction (BPO). Some of the advantages of GreenLight photoselective vaporization (PVP) are shorter catheterization time and hospital stay compared to TURP. Post-operative acute urinary retention (pAUR) leads to patients' discomfort, prolonged hospital stay and increased health care costs. We analyzed risk factors for urinary retention after GreenLight laser PVP. Materials and methods: In a multicenter experience, we retrospectively analyzed the onset of early and late post-operative acute urinary retention in patients undergoing standard or anatomical PVP. The pre-, intra- and post-operative characteristics were compared betweene patients who started to void and the patients who developed post-operative urinary retention. Results: The study included 434 patients suitable for the study. Post-operative acute urinary retention occurred in 39 (9%). Patients with a lower prostate volume (P < .001), an adenoma volume lower than 40 mL (P < .001), and lower lasing time (P = .013) had a higher probability to develop pAUR at the univariate analysis. The multivariate logistic regression confirmed that lower lasing time (95% CI: 0.86-0.99, OR = 0.93, P = .046) and adenoma volume (95% CI: 0.89-0.98, OR = 0.94, P = .006) are correlated to pAUR. Furthermore IPSS ≥ 19 (95% CI: 1.19- 10.75, OR = 2.27, P = .023) and treatment with 5-ARI (95% CI: 1.05-15.03, OR = 3.98, P = .042) are risk factors for pAUR. Conclusion: In our series, post-operative acute urinary retention was related to low adenoma volume and lasing time, pre-operative IPSS ≥ 19 and 5-ARI intake. These data should be considered in deciding the best timing for urethral catheters removal

Nonlinearities Associated with Impaired Sensors in a Typical SHM Experimental Set-Up

Structural Health Monitoring (SHM) gives a diagnosis of a structure assessing the structural integrity and predicting the residual life through appropriate data processing and interpretation. A structure must remain in the design domain, although it can be subjected to normal aging due to usage, action of the environment, and accidental events. SHM involves the integration of electronic devices in the inspected structure that sometimes are Piezoelectric Transducers (PZT). These are lightweight and small and can be produced in different geometries. They are used both in guided wave-based and electromechanical impedance-based methods. The PZT bonding requires essential steps such as preparation of the surfaces, application of the adhesive, and assembly that make the bonding process not so easy to be realised. Furthermore, adhesives are susceptible to environmental degradation. Transducer debonding or non-uniform distributed glue underneath the sensor causes the reduction of the performance and can affect the reliability of the SHM system. In this paper, a sensor diagnostic method for the monitoring of the PZT operational status is proposed in order to detect bonding defect/damage between a PZT patch and a host structure. The authors propose a method based on the nonlinear behaviour of the contact PZT/structure that allows the identification of the damaged PZT and the geometrical characterization of the debonding. The feasibility of the diagnostic procedure is demonstrated by numerical studies and experiments, where disbonds were created by inhibiting the adhesive action on a part of the interface through Teflon film. The proposed method can be used to evaluate the sensor functionality after an extreme loading event or over a long period of service time

Bending behaviour of sandwich panels with aluminium foam core

The bending behavior of hybrid sandwich panels, with aluminum foam core, and carbon fiber reinforced thermoset resin face sheets, have been investigated. The effect of core and face sheets thickness and span , on 3-point bending test, has been evaluated for the sandwich panels . Core yielding and indentation failure modes, influenced by the core properties, have been identified and analytical models to evaluate the maximum load have been applied. The failure mode map has been constructed, which illustrates the dominant failure mode for practical beam design. In order to simulate the different failure modes, FE analysis has been pointed out