200 research outputs found
Risk based, multi objective vehicle routing problem for hazardous materials: a test case in downstream fuel logistics
Abstract The paper analyses a practical case of study related to the distribution of fuels for the Total Erg Oil Company to the service stations located in the Province of Rome (Italy). The problem is formulated as a capacitated vehicle routing problem with time windows, where several heuristic procedures have been tested, considering both static and dynamic travel times. With respect to the standard operational costs used typically, a multivariable objective function has been proposed which takes into account also a new risk index. The risk index proposed is function of the population density of the zones covered by each path and of the estimated number of road accidents on each road link. In such a way, we take into account the population's exposure to the risk associated with an incidental event involving a fuel tank. The obtained output is the set of planned routes with minimum service cost and minimum risk. Results demonstrate how an accurate planning of the service saves up to 3 hours and 30 km on a daily basis compared to a benchmark. Moreover, the distribution company can parameterize the configuration of the service, by varying the weight adopted in order to include the risk index. Including the risk index may bring to a higher safety route planning, with an increase of the operating costs of only 2%
Advanced Model for Fast Assessment of Piezoelectric Micro Energy Harvesters
The purpose of this work is to present recent advances in modeling and design of piezoelectric energy harvesters, in the framework of micro-electro-mechanical systems (MEMS). More specifically, the case of inertial energy harvesting is considered, in the sense that the kinetic energy due to environmental vibration is transformed into electrical energy by means of piezoelectric transduction. The execution of numerical analyses is greatly important in order to predict the actual behavior of MEMS devices and to carry out the optimization process. In the common practice, the results are obtained by means of burdensome 3D finite element analyses (FEA). The case of beams could be treated by applying 1D models, which can enormously reduce the computational burden with obvious benefits in the case of repeated analyses. Unfortunately, the presence of piezoelectric coupling may entail some serious issues in view of its intrinsically three-dimensional behavior. In this paper, a refined, yet simple, model is proposed with the objective of retaining the Euler-Bernoulli beam model, with the inclusion of effects connected to the actual three-dimensional shape of the device. The proposed model is adopted to evaluate the performances of realistic harvesters, both in the case of harmonic excitation and for impulsive loads
Serum uric acid, creatinine, and the assessment of antioxidant capacity in critical illness
No Abstract - The letter addresses the issue of low plasma urate as a marker of impaired antioxidant capacity in critical illness
Parenteral Nutrition in Liver Resection
Albeit a very large number of experiments have assessed the impact of various substrates on liver regeneration after partial hepatectomy, a limited number of clinical studies have evaluated artificial nutrition in liver resection patients. This is a peculiar topic because many patients do not need artificial nutrition, while several patients need it because of malnutrition and/or prolonged inability to feeding caused by complications. The optimal nutritional regimen to support liver regeneration, within other postoperative problems or complications, is not yet exactly defined. This short review addresses relevant aspects and potential developments in the issue of postoperative parenteral nutrition after liver resection
Esiti di salute e performance del Servizio Sanitario Nazionale
Capitolo del Rapporto OASI incentrato sugli esiti di salute e performance del Servizio Sanitario Nazionale
Deep space orbit determination via Delta-DOR using VLBI antennas
The growing number of deep space exploration missions operating simultaneously in the solar system triggers an increasing demand for large ground antennas capable of tracking distant spacecraft. Several space agencies have their own deep space tracking networks, where each antenna belonging to a ground station complex is meant to be shared among different deep space missions in flight, significantly constraining the tracking schedule. A typical ranging and Doppler radio tracking session requires long tracking passes and a single ground antenna, while angular (Delta-DOR) observations require at least two antennas but usually for much shorter tracking sessions. However, during Delta-DOR observations, the baseline between the two receiving antennas should be kept as large as possible, thus reducing the time windows in which Delta-DOR observations are actually feasible. This leaves little room for adaptation of the tracking schedules of these antennas and calls for the need for possible alternatives for the receiving stations. The antennas belonging to the very long baseline interferometry (VLBI) network worldwide meet the requirements to carry out Delta-DOR tracking sessions. Here, we present an experimental activity carried out tracking ESA’s GAIA spacecraft using a mixed deep space antenna configuration involving an ESA ESTRACK antenna at New Norcia (Australia) and a VLBI antenna at Medicina (Italy). This baseline was used to form Delta-DOR observables with the aim of demonstrating that VLBI antennas offer the capability to track deep space missions, thus increasing the number of possible baselines and observation time windows
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