1,721,008 research outputs found
DERIVAZIONE DEI MODELLI PREVISIONALI PER LE ROTATORIE URBANE. UN CASO STUDIO,
No full textCome è noto, i modelli previsionali d’incidentalità (in campo internazionale conosciuti come Safety Performance Functions) vengono ormai da tempo impiegati nelle valutazioni di sicurezza; ad essi è affidato il compito di condensare le conoscenze pregresse sulla sicurezza di entità (tronchi stradali, intersezioni, etc.) simili a quelli in considerazione.
Quando integrati in una procedura di stima empirico-bayesiana, i modelli previsionali d’incidentalità concorrono alla correzione della distorsione dovuta alla regressione verso la media ed all’accrescimento della precisione della stima.
Nella presente memoria viene presentato un esempio di determinazione di tali modelli per il caso di rotatorie urbane.
Attraverso lo stesso esempio, si intende mostrare l’opportunità di prendere in considerazione la correlazione temporale dei dati, in conseguenza della quale l’ipotesi di indipendenza che autorizza l’impiego di modelli lineari generalizzati (GLM) cade in difetto.
Contemporaneamente, si intende mostrare come uno sforzo addizionale che tenga conto della vera struttura di correlazione dei dati possa essere compensato da una migliore precisione nella stima dei parametri del modello
Capacity-based calculation of passenger car equivalents using traffic simulation at double-lane roundabouts
No full textCalculation of passenger car equivalents for heavy vehicles represents the starting point for the operational analysis of road facilities and other traffic management applications. This paper introduces a criterion to find the passenger car equivalents that reflect traffic conditions at double-lane roundabouts, where the capacity is typically estimated for each entry lane. Based on the equivalence defined by the proportion of capacity used by vehicles of different classes, the criterion implies a comparison between the capacity that would occur with a traffic demand of passenger cars only and the capacity reached beginning from a demand with a certain percentage of heavy vehicles. A preliminary activity consisted of the comparison of the empirical capacity functions based on a meta-analytical estimation of critical and follow up headways, and simulation output data derived for a double-lane roundabout built in AIMSUN. The formulation of the calibration process as an optimisation problem enabled to minimize an objective function using the genetic algorithm tool in MATLAB®. A subroutine in Python implemented the automatic interaction with AIMSUN. Differently from methods that propose constant values for the passenger car equivalents, the results highlighted that the passenger car equivalents at double-lane roundabouts increased when the circulating flow increased, while a higher effect was expected when the traffic streams included a higher number of heavy vehicles
Estimating pollutant emissions based on speed profiles at urban roundabouts: A pilot study
No full textThe paper describes the pilot study conducted to assess the feasibility of the empirical approach utilizing vehicle trajectory data from a smartphone app and the Vehicle-Specific Power methodology to estimate pollutant emissions at urban roundabouts. The goal of this research phase is to acquire instantaneous speed data from a sample of six roundabouts located in the road network of the City of Palermo, Italy, and quantify emissions generated by the test vehicle through the examined roundabouts. For the case studies of roundabouts acceleration events in the circulating and exiting areas contributed to about 25% of the emissions for a given speed profile. More in general, the results from this research shed lights for further opportunities to examine infrastructural scenarios when decision makers require to assess changes in the design or operation of urban transportation systems
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
Speciation of organotin compounds in NaCl aqueous solution. Interaction of mono-, di- and triorganotin(IV) cations with nucleotides 5’ monophosphates
No full textFormation constants for complex species of mono-, di- and tri-alkyltin(IV) cations with somenucleotide 5-monophosphates (AMP, UMP, IMP and GMP) are reported, atT=25◦CandatI=0.16 mol l−1(NaCl). The investigation was performed in the light of speciation of organometalliccompounds in natural fluids in the presence of nucleotides whose biological importance is wellrecognized. The simple and mixed hydrolytic complex species formed in all the systems investigatedin the pH range 3–9 are (L=nucleotide; M=organotin cation RxSn(4−x)+, withx=1to3):ML+,ML(OH)0and ML(OH)2−for the system CH3Sn3+–L (L=AMP, IMP, UMP); ML0and ML(OH)−for the system (C2H5)2Sn2+–L (L=AMP, IMP, UMP); ML−, ML(OH)2−,MLH0and M2L(OH)−forthe system (C2H5)3Sn+–L (L=AMP); ML, ML(OH)2−and M2L0for the system (C2H5)3Sn+–L (L=IMP, UMP). As expected, owing to the strong tendency of organotin(IV) cations to hydrolysis inaqueous solution, the main species formed in the pH range of interest of natural fluids are the mixedhydrolytic ones
Linee guida per l'analisi di sicurezza stradale
No full textCircolazione & Sicurezza Stradale supplemento a Le Strad
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