1,720,965 research outputs found
Bilevel programming and price setting problems
No full textThis paper is devoted to pricing optimization problems which can be modeled as bilevel programs. We present the main concepts, models and solution methods for this class of optimization problems.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
A Network Pricing Formulation for the revenue maximization of European Air Navigation Service Providers
No full textIn Europe, all Air Navigation Service Providers (ANSPs) finance their activities by charging airlines to use their airspace. These ‘en route charges’ usually account for a significant fraction of the cost of a flight, and they can therefore influence the route choice: airlines may decide to fly longer routes to avoid countries with higher charges. Then ANSPs’ traffic and revenue do depend on the charge they impose on their own airspace. It follows that if ANSPs look for the maximization of their revenues, they must choose an optimal charge to impose on their airspace. We show that this optimal charge can be identified through a Network Pricing Problem formulation in the form of Bilevel Programming where the leader (i.e. the ANSP) owns a set of arcs (the airways in its national airspace) and charges the commodities (i.e. the flights) passing through them. As the en route charges are proportional to a Unit Rate value fixed by the ANSP, by exploiting the structure of the problem we propose an exact algorithm to compute the optimal Unit Rate and apply it to a case study
Sociodemographic Groups and Mode Choice in a middle-sized European City
No full textIn this paper the transport mode choice behaviour of different socio-demographic groups has been studied in a middle size European city. Data have been extracted from an extensive origin-destination survey (10,029 individuals and 28,225 trips) conducted in Trieste in 2002-03. Gender, age, employment and vehicle availability are important variables in mode choice.
These variables have been explicitly introduced within the utility function of a Random Utility Model (Multinomial Logit Model). The proposed model allows to evaluate the effects of different transportation planning initiatives on different socio-demographic groups.
In particular the improvement of transit performances would benefit more elderly, women especially housewives and retired than young people, men and workers. On the contrary any car network level-of-service worsening would negatively impact on non elderly and workers and on mothers with children much more than on non-workers or single individuals because they could respectively use busses or motorcycles.
The effects of any transportation initiatives do not impact on the population as a whole, but on the contrary their effects are quite different for different socio-demographic groups. These differences should be considered within the assessment of any transportation planning process, at least for two reasons: on one hand they allow to better perform the policy design phase and, on the other hand, they allows to better predict the effects of any transportation scenario.
The introduction of socio-demographic variables within a mode choice model should be aimed not only to improve the statistical evaluation of the model but also to increase its descriptive potentialities
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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