Search results for " Mecca"

Controlled solution-based fabrication of perovskite thin films directly on conductive substrate

2021

Abstract Organometallic perovskites are one of the most investigated materials for high-efficiency thin-film devices to convert solar energy and supply energy. In particular, methylammonium lead iodide has been used to realize thin-film perovskite solar cells, achieving an efficiency higher than 20%. Different fabrication procedures based on the spin-coating technique have been proposed, which do not ensure homogenous morphologies. In this work, we present a scalable process to fabricate methylammonium lead iodide thin films directly on conductive substrates, consisting of electrodeposition and two subsequent chemical conversions. A thorough investigation of the morphological, structural an…

Improved FMECA for effective risk management decision making by failure modes classification under uncertainty

2022

Failure Mode, Effects, and Criticality Analysis (FMECA) is a proactive reliability and risk management technique extensively used in practice to ensure high system performance by prioritising failure modes. Owing to the limitations of traditional FMECA, multi-criteria decision-making methods have been employed over the past two decades to enhance its effectiveness. To consider the vagueness and uncertainty of the FMECA evaluation process, an interval-based extension of the Elimination et Choice Translating Reality (ELECTRE) TRI method is proposed in the present paper for the classification of failure modes into risk categories. Therefore, ratings of failure modes against risk parameters are…

Theoretical and Experimental Comparison between the Resistance Components of a fast Catamaran in different Configurations

2009

The investigation performed by the Authors represents the most recent development of a research presented in [1] and [2], in which the geometrical solutions of the hull have been obtained through an optimization process, made by using the CFD numerical methods. The most important result of this optimization was the wave resistance reduction, which arrived up to 20% of the total initial resistance. In this further process the hull catamaran model has been built and tested at the towing tanks of the Universities of Naples and Trieste. The results obtained in the numerical process have been compared with the experimental ones and the reliability of the numerical results will be proved. Then th…

Trattamento dell'incertezza epistemica nell'analisi affidabilistica

Epistemic uncertainty in fault tree analysis approached by the evidence theory

2012

Abstract Process plants may be subjected to dangerous events. Different methodologies are nowadays employed to identify failure events, that can lead to severe accidents, and to assess the relative probability of occurrence. As for rare events reliability data are generally poor, leading to a partial or incomplete knowledge of the process, the classical probabilistic approach can not be successfully used. Such an uncertainty, called epistemic uncertainty, can be treated by means of different methodologies, alternative to the probabilistic one. In this work, the Evidence Theory or Dempster–Shafer theory (DST) is proposed to deal with this kind of uncertainty. In particular, the classical Fau…

An analysis of interface delamination mechanisms in orthotropic and hybrid fiber-metal composite laminates

2007

Abstract The onset and propagation of interlaminar defects is one of the main damage mechanisms in composite materials. This is even more the case when considering layered materials comprising metallic laminae (typically Aluminium) and FRP laminae. Propagation of delamination mainly depends on the initial crack extension and its loading mode. This work presents some results of a combined analytical–numerical–experimental study on the onset and propagation mechanisms regarding interlaminar defects. Two cases have been analysed in particular, the first consisting of a glass-fibre reinforced epoxy resin laminate, and the second consisting of a hybrid laminate where a lamina of aluminium is lay…

Trajectory tracking for an Ultralight WIG

2007

In this paper we present our research about a particular ultralight WIG. We have carried out the design of a Flight Control System that has to fix the control variables trend through a non-linear mathematical model, because of the particular geometric and aerodynamic configuration of this WIG. So, the non-linear mathematical model design has to reproduce exactly the aircraft behaviour either OGE or IGE. In particular, through classical semi-empirical relations, analytical equations have been obtained in order to evaluate incidence variations, downwash and upwash angles due to the ground. In the present paper only longitudinal dynamic is considered, because of its peculiarity in WIG's aircra…

Control of hysteretic instability in rotating machinery by elastic suspension systems subject to dry and viscous friction

2010

Abstract Most of the undesired whirling motions of rotating machines can be efficiently reduced by supporting journal boxes elastically and controlling their movement by viscous dampers or by dry friction surfaces normal to the shaft axis, which rub against the frame. In the case of dry dampers, resonance ranges of the floating support configuration can be easily cut off by planning a motionless adhesive state of the friction surfaces. On the contrary, the dry friction contact must change automatically into sliding conditions when the fixed support resonances are to be feared. Moreover, the whirl amplitude can be restrained throughout the speed range by a proper choice of the suspension-to-…

An EKF Based Method for Path Following in Turbulent Air

2017

An innovative use of the Extended Kalman Filter (EKF) is proposed to perform both accurate path following and adequate disturbance rejection in turbulent air. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one estimates modified aircraft parameters. The first filter, by using measurements gathered in turbulent air, estimates both aircraft states and wind components. The second one, by using the estimated disturbances, obtains command laws that are able to reject disturbances. The predictor of the second EKF uses the estimated wind components to solve motion equations in turbulent air. Besides a set of unknown stability …

Automatic EKF tuning for UAS path following in turbulent air

2018

By using two simultaneously working Extended Kalman Filters, a procedure is implemented in order to perform in a fully autonomous way the path following in turbulent air. To guarantee the robustness of the proposed algorithm, an automatic tuning procedure is proposed to determine optimal values of Process and Measurement Noise statistics. Such a procedure is based on both the characteristics of the disturbances and the desired flight path; in particular, a specific performance index is applied to tune filters. In this way control laws are adapted to the flight condition and these lead to an optimal path-following. This research represents an upload of previous papers. It allows eliminating …