1,720,973 research outputs found
Automazione e sicurezza nelle ferrovie metropolitane
No full textIl lavoro illustra i principi funzionali dei sistemi automatici ferroviari con la descrizione dei principali componenti. Si riportano alcuni esempi di variabilità di alcune componenti del tempo giro, evidenziando come un sistema automatico possa contribuire alla loro eliminazione. Si delineano, infine, gli aspetti positivi e negativi dell'automazione. Parole chiave: automazione, principi funzionali, aspetti positivi e negativ
Effects of passengers flows on regularity of metro services: case studies of Rome lines A and B
No full textThe regularity is a key performance in the operation of a metro service, because it is normally affecting a large set of secondary performances: e.g. punctuality, energy efficiency, economic efficiency and vehicles availability. Human behaviours are affecting the regularity, by introducing deviations between panned and actual times in various operational phases of metro services: e.g. dwelling times, acceleration/deceleration times, inversion times at terminus, headways themselves. The variability in passengers’ flows is one of the most relevant parameters affecting mainly dwelling times and finally headways themselves. In this framework, this paper is specifically presenting the results of experimental surveys on metro services operated in Rome (Lines A and B).
On these lines, it has been performed a systematic counting of passengers boarding and alighting in the most crowded stations, combined with simultaneous measurement of actual dwelling times and headways. The collected results have been analysed, cleaned by inconsistent data and statistically interrelated looking for significant trends to compare with the most consolidated theoretical models and to quantify the effects in line with the literature developments, including those by the authors themselves. Finally, the focus is on the most relevant quantitative outputs and the main identified and outlined
further research needs
La verifica delle stazioni terminali nelle linee di ferrovia metropolitana.
No full textLa gestione operativa di treni e dei relativi itinerari nelle stazioni di testa costituisce
problema di notevole complessim in virtU delIa lunga durata dei tempi di inversione
del senso di marcia e deIl'elevato numero di itinerari incompatibili, che
riduce drasticamente la possibilim di movimenti contemporanei.
Lo studio tratta specificatamente il problema delIa valutazione delIa capacim di
un terminale in funzione delle caratteristiche del servizio (frequenze, cadenzamenti,
tipologie di convogli, etc.), delIa tipologia e dell'estensione dell'impianto.
In questi ambito sono stati esaminati alcuni terminali della Linea C delIa metropolitana
di Roma, due terminali per il servizio regionale (Perugia Sant' Anna e
Napoli Garibaldi) e, infine, un grande nodo interessato anche da traffico a lunga
percorrenza: Firenze Santa Maria Novella
Pyrolyzed tannery sludge as adsorbent of volatile organic compounds from tannery air emissions
No full textThe tanning industry has a great impact on the environment for the large consumption of water, the huge amount of waste generated, and the high emissions of volatile organic compounds (VOCs), used in leather finishing operations. In this study, pyrolyzed tannery sludge (PTS) was investigated, after further pyrolysis at high temperature, as a sorbent of VOCs. Pyrolysis experiments were performed at various temperatures (750–850 °C) and times (6–60 min) to evaluate the optimal operating conditions in terms of developed BET specific surface area. Fixed bed adsorption experiments were performed to determine the breakthrough curves at room temperature using an air stream containing n-butyl acetate, a VOC largely used in leather finishing products. By pyrolysis at 850 °C for 6 min the BET of PTS increased from 72 to 127 m2/g, improving its sorption capacity. The effects of superficial velocity, inlet VOC concentration, and bed height on the sorption behaviour of PTS after further pyrolysis (PPTS) were investigated. Breakthrough curves were well fitted by the Bohart-Adams model (R2 = 0.92) and the adsorption isotherms with Freundlich equation (R2 = 0.97). Preliminary sorbent desorption tests were carried out by hot air in the temperature range 100–180 °C, demonstrating the feasibility of thermally regenerating this material. Multiple adsorption/desorption cycles on the PPTS will be performed on lab scale in a future study to investigate the real sorbent recyclability
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A study on the effect of flow unsteadiness on the yield of a chemical reaction in a t micro-reactor
Full text linkDespite the very simple geometry and the laminar flow, T-shaped microreactors have been found to be characterized by different and complex steady and unsteady flow regimes, depending on the Reynolds number. In particular, flow unsteadiness modifies strongly the mixing process; however, little is known on how this change may affect the yield of a chemical reaction. In the present work, experiments and 3-dimensional numerical simulations are carried out jointly to analyze mixing and reaction in a T-shaped microreactor with the ultimate goal to investigate how flow unsteadiness affects the reaction yield. The onset of the unsteady asymmetric regime enhances the reaction yield by more than 30%; however, a strong decrease of the yield back to values typical of the vortex regime is observed when the flow undergoes a transition to the unsteady symmetric regime
Effects of flow unsteadiness and chemical kinetics on the reaction yield in a T-microreactor
Full text linkExperimental flow visualizations and velocity measurements are used jointly with numerical simulations to investigate the mixing and monitor the reaction progress in the periodic flow regimes occurring in a T-shaped microreactor. We considered the effects of different kinetic constants, with very different characteristic chemical time scales resulting in a wide range of Damköhler numbers. A remarkable agreement between experiments and simulations is found both in terms of flow pattern and reaction progress. Two different flow regimes are present for increasing Reynolds number. The first is the periodic asymmetric regime, characterized by the shedding of vorticity-blobs along the mixing channel leading to a further increase of the mixing performance compared to the steady engulfment regime. The second regime is the periodic asymmetric one, which is mainly a poorly mixed segregated regime with periodic oscillation at the interface between the two reactants. The mixing degree significantly increases in the unsteady asymmetric regime, whereas it predictably drops down in the unsteady symmetric regime. In the periodic asymmetric regime the reaction yield follows the same function of the Damköhler number, describing the residence to chemical time-scale ratio, and of a non-dimensional kinetic constant, taking into account also fluid properties, previously proposed for the steady vortex and engulfment regimes. In the periodic symmetric regime, the reaction yield is found to depend only on the Damköhler number, with the same dependence previously highlighted for the steady segregated regime
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