Hydrogen is a promising energy carrier to allow the reach of the zero-emission targets established for the next years. Polymeric Electrolyte Membrane FC are studied inside the HI-SEA laboratory of the University of Genoa, to assess the opportunities of this technology on marine applications. Here, 8 PEMFC stacks, sized 30 kW each for a total power installation of 240 kW, have been tested to draw guidelines for the best system design onboard ships and to deepen the know-how on the experimental management of the technology. During the tests, it was possible to observe the reciprocal influence of some parameters, which may influence the system efficiency. In this work, a statistical investigation is developed to quantify the cell voltage variation correlated to the values of temperature and current. This has been possible thanks to Design Expert (DE), a software developed by Stat-EASE, Inc. Through the Design of Experiment approach, it is possible to evaluate the significance of variables in the FC system, called factors. The experiment under consideration is also characterized by non-controllable factors, cause of disturbances that induce further variability in the response. Eventually, it was possible to analyse the significance of the parameters involved, to build a regression model by performing the analysis of variance with which the significant values are identified, and to assess the presence of outliers.
In this work, a response surface-designed experiment approach was used to determine the optimal settings of laser treatment as a method of surface preparation for CFRP prior to bonding. A nanosecond pulsed Ytterbium-doped-fiber laser source was used in combination with a scanning system. A Face-centered Central Composite Design was used to model the tensile shear strength (TSS) of adhesive bonded joints and investigate the effects of varying three parameters, namely, power, pitch, and lateral overlap. The analysis was carried out considering different focal distances. For each set of joints, shear strength values were modeled using Response Surface Methodology (RSM) to identify the set-up parameters that gave the best performance, determining any equivalent conditions from a statistical point of view. The regression models also allow the prediction of the behavior of the joints for not experimentally tested parameter settings, within the operating domain of investigation. This aspect is particularly important in consideration of the process optimization of the manufacturing cycle since it allows the maximization of joint efficiency by limiting the energy consumption for treatment.
Optimization of maintenance services of a company working in the gas metering sector is investigated. In particular, daily tasks of operators are optimized by exploiting the paradigm of vehicle routing problems with a set of predefined time windows that overlap one with the others and four competing objectives to take into account. First, an exact integer formulation is presented that can be solved only for a reduced number of customer sites to visit. Then, a heuristic approach is proposed to find approximate solutions with huge savings on the computational effort, also for high‐dimensional instances. Numerical results on both real and synthetic scenarios showcase the effectiveness of the approach.
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