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Revisione del volume "Annotated Bibliographies in Combinatorial Optimization" (Dell'Amico, Maffioli, Martello Eds.)
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The stack loading and unloading problem
No full textWhen piling a set of items in a single stack, one often does not pay attention to the order. Real-life experience suggests that, whenever a specific item is suddenly requested, we need to dig very deep into the stack to extract it.In this paper we investigate stack reordering strategies aiming at minimizing the number of "pop" and "push" operations. In particular we focus on three versions of the problem in which reordering can take place in different phases: when unloading the stack, when loading it or in both phases.We show that the first two variants can be solved in linear time, while for the third one we devise a dynamic programming method with quadratic complexity
A new algorithm to find the shortest paths between all pairs of nodes
No full textAbstractA new algorithm to find the shortest paths between all pairs of nodes is presented. This algorithm makes use of a dual cost transformation and of a particular data structure. Its worst case time complexity is of the order of the third power of the number of nodes, and its space complexity is linear with the number of arcs. A comparison with existing algorithms is presented
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
Regional Mass Transit Assignment with Resource Constraints
No full textThis paper considers a mass transit system in a regional area. The problem of improving the quality of the service by decreasing the total passenger waiting time is studied. A model to improve the effectiveness of the system without worsening the cost (vehicles and duties) and the passenger assignment is proposed, along with a new definition of passenger assignment to support the proposed model
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