1,721,025 research outputs found
Progetti stradali
No full textCostituisce la parte dedicata alla progettazione geometrica funzionale delle strade del Manuale Cremonese per Geometr
Study of the impact of the vehicles against the concrete barriers delimiting the area of approach to narrower carriageways in function of the barrier's features
No full textThis paper examines the influence of the different factors that affect the problem of the collisions against the concrete safety barriers used to narrower the carriageways. In particular we studied both the influenece of the damage of the vehicles and the shear strength necessary in teh joints between the barriere elements. Moreover we pointed out some caracteristic aspects of this accident. For this pourpose we developed a specific software to simulate these collisions.
The study showed that the most important factor is the angle formed between the inclined barriers with the longitudinal direction. The analysis also pointed out that this collisions can be very dangerous both for the first vehicle contacting the barrier and the following on
Mixed analysis-synthesis approach for estimating airport noise from civil air traffic
No full textThis paper presents an important upgrade of a modelling tool devised by the authors for estimating aircraft noise around civil airports, which is based on a best-practice noise computation method and flight tracking data collected from the Internet and complemented by datasets of aircraft models, runways, and terrain elevation. Targeting more accurate noise predictions, the upgraded model introduces reasoned degrees of freedom in the standard flight procedures, and the tracked altitudes and speeds of each flight event are used to fit these modified procedures, which leads to an original mixed analysis-synthesis approach. Additional improvements include better runway assignment and consideration of actual weather conditions. Comparison of July 2019 results with official data for Heathrow, Gatwick and Schiphol airports shows an improved noise prediction, with an average underestimation lowered to 1.5 dB(A) for exposure-based metrics. Therefore, this upgraded modelling tool can be a reliable support to civil aviation authorities and policy-makers
Parte 4: Criteri di Impiego delle Barriere di Sicurezza in Presenza di Cantieri Stradali
No full textA phenomenological model for predicting the early development of the flame kernel in spark-ignition engines
Full text linkThis work presents a simple and effective phenomenological model for the prediction of the early growth of the flame kernel in SI engines, including its initiation as a result of the electrical breakdown of the fuel/air mixture between the spark plug electrodes. The present model aims to provide an improved description of the ignition-affected early phases of flame kernel development compared to the majority of models currently available in literature. In particular, these models focus on electrical energy supply and turbulence, whereas the stretch-induced kernel growth slowdown is quantified with linear models that are inconsistent with the small kernel radius. For the flame kernel initiation, this model replaces the current methods that rely on 1D heat diffusion within a plasma column with a more consistent analysis of post-breakdown conditions. Concerning the kernel growth, the present model couples the mass and energy conservation equations of a spherical kernel with the species and temperature profiles outside of it. This combination leads to a non-linear description of the flame stretch, according to which the kernel development is controlled by the Lewis-number-dependent balance between the heat gained via combustion and the heat lost via thermal diffusion. As a result, the kernel temperature differs from the adiabatic flame temperature, causing the laminar flame speed to change from its adiabatic value and ultimately affecting the overall kernel development. Kernel growth predictions are conducted for laminar flames and compared to literature data, showing a satisfactory agreement and highlighting the ability to describe the stretch-induced kernel slowdown, up to its possible extinction. A good agreement with literature data is also obtained for kernel expansions under moderately turbulent conditions, typical of internal combustion engines. The simple formulation of the present model enables swift integration into phenomenological combustion models for spark-ignition engines, while simultaneously offering useful insight into the early kernel development even for CFD-based approaches
Valutazione delle temperature della sovrastruttura ferroviaria per l’Alta Velocità attraverso una sperimentazione di laboratorio
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Impiego di un modello di combustione stocastico per la predizione delle emissioni di motori Diesel
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