1,721,037 research outputs found
Studio delle interazioni ruota-rotaia ai fini della sicurezza dell’esercizio e della manutenzione sviluppo di un sistema di misura sperimentale per il monitoraggio dei carichi trasversali
Full text linkIl presente lavoro, esaminando la situazione del settore ferroviario europeo in relazione alla sicurezza della circolazione ed alla manutenzione dei veicoli, affronta lo studio della misura delle forze di contatto, su base teorica e sperimentale, ai fini dello sviluppo di un sistema di misura sperimentale per il monitoraggio dei carichi trasversali (Y), lato infrastruttura. Attraverso una prima convenzione di ricerca con Rete Ferroviaria Italiana (RFI), è stato effettuato uno studio di fattibilità preliminare, confrontando tra loro due metodologie di misura differenti; successivamente la ricerca è proseguita a livello accademico approfondendo le potenzialità applicative di uno dei due metodi precedentemente analizzati. Infine, attraverso una seconda convenzione di ricerca, sempre con Rete Ferroviaria Italiana (RFI), si è sviluppato il sistema di misura a livello prototipale conducendo ulteriori prove sperimentali di laboratorio ed installando l’apparato direttamente in linea durante il normale esercizio
One, no one, and one hundred thousand: The paradigm of the Z–R relationship
No full textThe Z–R relationship is a scaling-law formulation, Z 5 ARb, connecting the radar reflectivity Z to the rain rate R. However, more than 100 Z–R relationships, with different values of the parameters, have been reported in literature. This abundance of relationships is in itself a strong indication that no one ‘‘physical’’ relationship exists, a state of affairs that we find similar to that of the protagonist of Luigi Pirandello’s novel One, No One and One Hundred Thousand. Nevertheless the ‘‘elevation’’ of a simple linear fit in the (logR, logZ) space to the role of ‘‘scaling law’’ is such a widespread tenet in literature that it eclipses the simple realization that the abundance of different intercepts and slopes reflects the inhomogeneous nature of rain, and, in ultimate analysis, the statistical variability existing between the number of drops and drop size dis-tribution. Here, we ‘‘eliminate’’ the contribution of the number of drops by rescaling both reflectivity and rainfall rate to per unit drop variables, (Z, R) → (z, r), so that the remaining variability is due only to the variability of the drop size distribution. We use a worldwide database of disdrometer data to show that for the rescaled variables (z, r) only ‘‘one,’’ albeit approximate, scaling law exists
A point based Eulerian definition of rain event based on statistical properties of inter drop time intervals: An application to Chilbolton data
No full textSpecial Issue on Improving the Environmental Performances of Maritime Transport and Ports
No full textSporadic randomness: The transition from the stationary to the nonstationary condition
No full textWe address the study of sporadic randomness by means of the Manneville map. We point out that the Manneville map is the generator of fluctuations yielding the Levy processes, and that these processes are currently regarded by some authors as statistical manifestations of a nonextensive form of thermodynamics. For this reason we study the sensitivity to initial conditions with the help of a nonextensive form of the Lyapunov coefficient. The purpose of this research is twofold. The former is to assess whether a finite diffusion coefficient might emerge from the nonextensive approach. This property, at first sight, seems to be plausible in the nonstationary case, where conventional Kolmogorov-Sinai analysis predicts a vanishing Lyapunov coefficient. The latter purpose is to confirm or reject conjectures about the nonextensive nature of Levy processes. We find that the adoption of a nonextensive approach does not serve any predictive purpose: It does not even signal a transition from a stationary to a nonstationary regime. These conclusions are reached by means of both numerical and analytical calculations that shed light on why the Levy processes do not imply any need to depart from the adoption of traditional complexity measures
Using multiple correspondence analysis to improve safety in interaction between road transit and public spaces
No full textMultiple Correspondence Analysis (MCA) is a statistical technique used to present the relative closeness of the categorical variables from any dataset by analyzing data in the form of numerical frequencies and represent them graphically. Since pedestrian accidents data can be represented as transactions of multiple categorical variables, MCA can be a considered a good methodology to analyze the relationship among such variables. This paper is the study of application of MCA to analyze safety in the interaction among urban road transit and pedestrians. MCA is applied to a Bus Rapid Transit (BRT) line in the city of Catania, operating since 2013; during those years there were no accidents, but a series of traffic conflicts have happened; that’s the reason why authors proceed with the application of the methodology taking into account the occurrence of the so called “near misses”
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