1,721,067 research outputs found
Vehicle routing: historical perspective and recent contributions
No full textThe vehicle routing problem requires the design of least cost delivery routes through a set of geographically scattered customers and is one of the most widely studied combinatorial optimization problems. We briefly summarize the main historical achievements and review some recent important contributions in this vivid research area
An Integer Linear Programming based heuristic for the Capacitated m-Ring-Star Problem
No full textWe address the Capacitated m-Ring-Star Problem in which the aim is to find m rings (simple cycles) visiting a central depot, a subset of customers and a subset of potential (Steiner) nodes, while customers not belonging to any ring must be "allocated" to a visited (customer or Steiner) node. Moreover, the rings must be node-disjoint and the number of customers allocated or visited in a ring cannot be greater than a given capacity Q. The objective is to minimize the total visiting and allocation costs. The Capacitated m-Ring-Star Problem is NP-hard, since it generalizes the Traveling Salesman Problem. In this paper we propose a new heuristic algorithm which combines both heuristic and exact ideas to solve the problem. Following the general Variable Neighborhood Search scheme, the algorithm incorporates an Integer Linear Programming based improvement method which is applied whenever the heuristic algorithm is not able to improve the quality of the current solution. Extensive computational experiments, on benchmark instances of the literature and on a new set of instances, have been performed to compare the proposed algorithm with the most effective methods from the literature. The results show that the proposed algorithm outperforms the other methods
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
Aircraft Sequencing Problems via a Rolling Horizon AlgorithmCombinatorial Optimization
No full textAircraft sequencing on the runway is a challenging optimization problem that aims to reduce the delays and the air traffic controllers workload in a scenario characterized by a continuous growth of the air transportation demand. In this paper we consider the problem of sequencing both arrivals and departures on a single runway airport. We formalize the problem using a Mixed Integer Programming Model and we propose a rolling horizon solution approach. Computational results on real-world air traffic instances from the Milano Linate Airport are reported. The results show that the proposed approach is able to significantly improve on the First Come First Served (FCFS) sequence
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
Guest editorial to the Special Issue "Routing and Logistics" (VeRoLog 2012)
No full textVehicle routing is one of the most active research areas in combinatorial optimization since more than 50 years. Starting from the seminal paper by Dantzig and Ramser in 1959, literally hundreds of papers introduced innovative exact and heuristic algorithms for the many variants of the Vehicle Routing Problem (VRP). The VRP is at the core of logistics and supply chain management, as well as of people transportation activities. Thus, the practical importance of optimization models and algorithms development for the VRP is evident from the impact of freight and people transportation in the modern world, both from an economic and an environmental point of view. Moreover, the field is not only related to terrestrial transportation of goods and people by means of vans, trucks and buses, but also to other modes of transport such as rail, naval and air transport and their interaction within intermodal networks
The Family of Vehicle Routing Problems
No full textA generic verbal definition of the family of vehicle routing problems can be the following:
Given: A set of transportation requests and a fleet of vehicles.
The problem is then to find a plan for the following:
Task: Determine a set of vehicle routes to perform all (or some) transportation requests with the given vehicle fleet at minimum cost; in particular, decide which vehicle handles which requests in which sequence so that all vehicle routes can be feasibly executed
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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