1,721,418 research outputs found
Vehicle routing problems over time: a survey
Full text linkIn vehicle routing problems (VRPs) the decisions to be taken concern the assignment of customers to vehicles and the sequencing of the customers assigned to each vehicle. Additional decisions may need to be jointly taken, depending on the specific problem setting. In this paper, after discussing the different kinds of decisions taken in different classes of VRPs, the class where the decision about when the routes start from the depot has to be taken is considered and the related literature is reviewed. This class of problems, that we call VRPs over time, includes the periodic routing problems, the inventory routing problems, the vehicle routing problems with release dates, and the multi-trip vehicle routing problems
Vehicle routing problems over time: a survey
Full text linkIn vehicle routing problems (VRPs) the decisions to be taken concern the assignment of customers to vehicles and the sequencing of the customers assigned to each vehicle. Additional decisions may need to be jointly taken, depending on the specific problem setting. In this paper, after discussing the different kinds of decisions taken in different classes of VRPs, the class where the decision about when the routes start from the depot has to be taken is considered and the related literature is reviewed. This class of problems, that we call VRPs over time, includes the periodic routing problems, the inventory routing problems, the vehicle routing problems with release dates, and the multi-trip vehicle routing problems
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
The one-station bike repositioning problem
Full text linkIn bike sharing systems the quality of the service to the users strongly depends on the strategy adopted to reposition the bikes. The bike repositioning problem is in general very complex as it involves different interrelated decisions: the routing of the repositioning vehicles, the scheduling of their visits to the stations, the number of bikes to load or unload for each station and for each vehicle that visits the station. In this paper we study the problem of optimally loading/unloading vehicles that visit the same station at given time instants of a finite time horizon. The goal is to minimize the total lost demand of bikes and free stands in the station. We model the problem as a mixed integer linear programming problem and present an optimal algorithm that runs in linear time in the size of the time horizon
Design of a Partial Discharge Test Platform
No full textDesign of a Partial Discharge Test Platform author: Daniel Harmsen thesis advisor (mentor): Dr. Armando Rodrigo Mor abstract: Partial discharge (PD) measurements are an effective tool for insulation diagnostics and assessment. Therefore, a good understanding of these PD measurements is an essential part of an electrical engineer’s background knowledge. During this research project a PD test platform was designed and build for electrical PD detection. The setup included artificially created defects for six different types of PDs, with origins in positive and negative corona, internal discharge, floating electrodes, free-moving particles and surface discharge. These defects were designed to have a partial discharge inception voltage (PDIV) of around 10kV, and could easily be connected or disconnected from the setup. Therefore, it was possible to measure individual defects or a combination of them. This PD test platform was used during this research project to characterize the different PD types (single and multiple), and as a check for testing new clustering and pattern recognition techniques. In addition, the platform could also be used as a test platform for educational purposes and to train people and test equipment. In this thesis research project, the “initial step” towards PD defect origin recognition for AC voltage without any phase dependency was conducted with the use of time-resolved partial discharge (TRPD) analysis. This thesis shows that it is possible to conduct the time analysis and recognition for AC voltage for the artificially created defects. From the analysis in this thesis, it can be concluded that the TRPD analysis for PD recognition under AC voltage is as good as, or even better than, phase-resolved partial discharge (PRPD) analysis. For most of the data analysed, the TRPD analysis provides the same results compared to the PRPD analysis. However, further checking is needed, such as validating the findings with mathematical models. The thesis goals are to build a setup suitable for the research, determining the optimal combination of hardware/software to discriminate among different types of defects, and to realize experiments to validate the design.Electrical Engineering, Mathematics and Computer ScienceDC&E
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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