1,720,967 research outputs found
Routing one million customers in a handful of minutes
Full text linkThis paper proposes a new dataset of Capacitated Vehicle Routing Problem instances, up to two orders of magnitude larger than those in the currently used benchmarks. Although these sizes might not have an immediate application to real -world logistic scenarios, we believe they could foster fresh new research efforts on the design of effective and efficient algorithmic components for routing problems. We provide computational results for such instances by running FILO2, an adaptation of the FILO algorithm proposed in Accorsi and Vigo (2021), designed to handle extremely large-scale CVRP instances. Solutions for such instances are obtained using a standard personal computer in a considerably short computing time, thus showing the effectiveness of the acceleration and pruning techniques already proposed in FILO. Finally, results of FILO2 on well-known literature instances show that the newly introduced changes improve the overall scalability of the approach with respect to the previous FILO design
Guidelines for the computational testing of machine learning approaches to vehicle routing problems
No full textDespite the extensive research efforts and the promising results obtained by the ML community on Vehicle Routing Problems, most of the proposed techniques are still seldom employed by the OR community. With the current work, we highlight a number of challenges arising during the computational evaluation of heuristics for VRPs. The resulting guidelines aim at defining a common testing setup for the approaches designed by the two communities, thus promoting and strengthening the collaboration between them
A Measuring Instrument for In-Line and Real-Time Measurement of Blood- pCO2in Extracorporeal-Circulation
No full textSince the late 1950s, blood CO2 can be measured by using electrodes and, more recently, also by using point-of-care instruments such as blood gas and chemistry analyzers. Nevertheless, nowadays no measurement method has succeeded in providing an economic, reliable, and accurate estimate of the blood- CO2 to be routinely used for the monitoring of extracorporeal (blood) circulation (ECC) treatments. Indeed, blood is a very complex biological matrix composed of several different constituents, thus apart from a limited maximum-admitted measurement error (about some mmHg) and a quite wide measuring interval (about [20, 100] mmHg), the measuring systems have to provide significant selectivity taking hemocompatibility and safety for the patient as a primary concern. In this article, we propose and demonstrate a measuring instrument consisting of a low-cost and disposable fluorescent pco-sensor that can be inserted in series with the bloodline, and a nondisposable optical head that contactless reads the sensor. The proposed measuring system is intrinsically safe for the patient, has adequate metrological performance, avoids blood sampling and the related issues, and may allow to comply with cost requirements. Preliminary tests, conducted simulating a 6-h ECC treatment by using bovine blood, revealed deviations from the reference measuring instrument of less than ±4 mmHg, while the blood- CO2 was varied in the range [20, 100] mmHg
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
An efficient heuristic for very large-scale vehicle routing problems with simultaneous pickup and delivery
No full textThe paper discusses two variants of the Capacitated Vehicle Routing Problem (CVRP), in which each customer to be visited can require both pickup and delivery, or only either pickup and delivery but not both. These problems are referred to, respectively, as the Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) and as the Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD). Both VRPSPD and VRPMPD are particularly relevant in practical logistics distribution scenarios, especially when dealing with a substantial number of pickup and delivery locations. The aim of this work is to provide an algorithm which extends, through a variety of specializations, the FILO framework, originally proposed and specifically designed for the CVRP. This variant, called FSPD, has been developed to accomplish two objectives: first, being competitive with the state-of-the-art algorithms for the VRPSPD and VRPMPD; second, efficiently solving new benchmark instances for these problems with a very large number of customers, while maintaining linear scalability of the computing time with respect to the problem size. The extensive computational study and detailed analysis of the algorithm components conducted in this paper demonstrate the successful achievement of both objectives
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
- …
