1,721,120 research outputs found
Fixed point models for the estimation of O/D matrices using traffic counts on congested networks
No full textConnectivity carbon and noise levels in the airport neighbourhood
No full textMany airport connectivity measures have been studied and proposed in the literature to capture both the effects of increased/reduced airport connectivity and the quality level of the connections. This study focuses on the relationship between connectivity – measured by air links and number of flights – and airport carbon/noise local levels. Although airport connectivity evokes the perception of geographical distances covered by air services, on ground connectivity consequences affect directly airport neighbourhood. Increased airport connectivity generally generates increasing number of airport movements that, in turn, produce higher levels of environmental externalities, such as noise and carbon emissions, mainly on local communities. To quantify such relationship, the Viable Connectivity Index (VCI)is proposed, which combines connectivity and noise/carbon levels at the airport. The index could be used as a preliminary test of airport operator policy actions to identify suitable policies addressed to reduce their noise and carbon amount and keep at the same time good connectivity levels. The test case of Bologna airport - a large regional airport in Northern Italy - is also discussed
Impacts of connected autonomous vehicle platoon breakdown on highway
No full textConnected Autonomous Vehicles (CAVs) are seen as an opportunity to improve traffic efficiency and safety. However, further studies are needed to prove such positive effects. Particularly, there is a lack of quantitative research on the impacts of CAV breakdown in mixed traffic flow conditions (i.e., CAVs and Human Driven Vehicles, HDVs). The aim of this research is to explore the impacts generated by the breakdown of the leading vehicle of a CAV platoon in mixed traffic conditions, which in turn generates CAV platoon breakdown (i.e., platoon dispersion), by considering several CAV market penetration rates (MPRs) and platoon size. In this perspective, a control algorithm (“avoidance algorithm”) for modelling CAVs and HDVs behaviour to avoid obstacles (i.e., breakdown CAV platoon) has been developed and tested on some simulation scenarios in order to derive key traffic flow parameters. The dynamic characteristics of traffic flow with CAV platoon breakdown have been explored for both low and high traffic flow volumes. Finally, potential conflicts, congestions, as well as energy consumption and CO2 emissions resulting from the breakdown of CAV platoons in mixed traffic streams have been assessed and discussed. Results suggest that (1) CAV platoon breakdown can reduce the traffic capacity by about 20 %; (2) higher CAV MPRs are more suitable for enhancing highway safety even in breakdown conditions, decreasing energy consumption, and reducing CO2 emissions; (3) platoon size should be limited to 4, since larger sizes affect traffic safety, increases vehicle average delay time as well as energy consumption. The obtained results provide useful insights for transportation planners and transport infrastructure management companies to design and apply policies aimed at improving driving conditions, traffic quality, and safety on highways
Green airport investments to mitigate externalities: Procedural and technological strategies
No full textTransport systems are important pollution sources, mainly in terms of greenhouse gases, noise and land consumption. To mitigate the problem and safeguard airport development at the same time, the involved stakeholders are fixing goals, priorities and duties in order to promote the sustainable development of the air transport industry at global level and the wellness of local communities as well. It is desirable to estimate airport noise and carbon impacts in order to suitably manage them and identify strategies in line with the concept of green economy. In this chapter, a general framework to identify optimal procedures and methods to evaluate the effectiveness of policies addressed to reduce airport impacts on the airport surroundings is proposed. The case study of the airport of Bologna is presented as an example of Transport Company that effectively operates to minimize its noise and carbon impacts. According to the proposed general framework, impacts and estimated costs to achieve the status of green company have been computed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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