1,721,720 research outputs found
Les Cahiers du GERAD A Tutorial on Variable Neighborhood Search A Tutorial on Variable Neighborhood Search
No full textLes textes publiés dans la série des rapports de recherche HEC n'engagent que la responsabilité de leurs auteurs. La publication de ces rapports de recherche bénéficie d'une subvention du Fonds québécois de la recherche sur la nature et les technologies. A Tutorial on Variable Neighborhood Search Pierre Hansen GERAD and HEC Montreal Nenad Mladenović GERAD and Mathematical Institute, SANU, Belgrade July, 2003 Les Cahiers du GERAD G-2003-46 Copyright c 2003 GERAD Abstract Variable Neighborhood Search (VNS) is a recent metaheuristic, or framework for building heuristics, which exploits systematically the idea of neighborhood change, both in the descent to local minima and in the escape from the valleys which contain them. In this tutorial we first present the ingredients of VNS, i.e., Variable Neighborhood Descent (VND) and Reduced VNS (RVNS) followed by the basic and then the general scheme of VNS itself which contain both of them. Extensions are presented, in particular Skewed VNS (SVNS) which enhances exploration of far away valleys and Variable Neighborhood Decomposition Search (VNDS), a two-level scheme for solution of large instances of various problems. In each case, we present the scheme, some illustrative examples and questions to be addressed in order to obtain an efficient implementation. Keywords: metaheuristics, heuristics, descent, valley, Variable Neighborhood Search, decomposition. Résumé La Rechercheà Voisinage Variable (RVV) est une métaheuristique récente, ou cadre général pour bâtir des heuristiques, qui exploite systématiquement l'idée de changement de voisinage tant dans la descente vers des optimas locaux que dans la sortie des vallées qui les contiennent. Dans cet article introductif nous présentons d'abord les ingrédients de la RVV, c'est-à-dire la Descenteà Voisinage Variable (DVV) et la Rechercheà Voisinage Variable Réduite (RVVR) suivis des schémas de base et général de la RVV. Des extensions sont ensuites présentées, en particulier la Rechercheà Voisinage Variable Biaisée (RVVB) qui améliore l'exploration de valléeséloignées et la Rechercheà Voisinage Variable avec Décomposition (RVVD), un schémaà deux niveaux pour la résolution d'instances de grande taille de divers problèmes. Dans chaque cas, on présente le schéma, un exemple et des questionsà considérer pour une implémentation efficace
Wilson, K G (Kenneth Gerad), WX6877
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/426641Surname: WILSON. Given Name(s) or Initials: K G (KENNETH GERAD). Military Service Number or Last Known Location: WX6877. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 42083.254182
Item: [2016.0049.58902] "Wilson, K G (Kenneth Gerad), WX6877
Spectral Reconstruction and Isomorphism of graphs using variable neighbourhood search
No full textThe Euclidean distance between the eigenvalue sequences of graphs G and H, on the same number of vertices, is called the spectral distance between G and H. This notion is the basis of a heuristic algorithm for reconstructing a graph with prescribed spectrum. By using a graph Γ constructed from cospectral graphs G and H, we can ensure that G and H are isomorphic if and only if the spectral distance between Γ and G+K2 is zero. This construction is exploited to design a heuristic algorithm for testing graph isomorphism. We present preliminary experimental results obtained by implementing these algorithms in conjunction with a meta-heuristic known as a variable neighbourhood search
Arnošt Gerad - doplňky k životu a dílu
No full textČlánek přináší další informace k životu a dílu českého slavisty Arnošta Gerada (1916–1942). Jsou zde představeny a krátce komentovány jeho texty k otázce židovství i odborné texty jazykovědné.The paper brings out additional information regarding the life and work of Czech scholar Arnošt Gerad (1916–1942). His papers on Judaism and his linguistic contributions are presented and briefly commented.Článek přináší další informace k životu a dílu českého slavisty Arnošta Gerada (1916–1942). Jsou zde představeny a krátce komentovány jeho texty k otázce židovství i odborné texty jazykovědné
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Improvements and comparison of heuristics for solving the uncapacitated multisource Weber problem
No full textCopyright @ 2000 INFORMSThe multisource Weber problem is to locate simultaneously m facilities in the Euclidean plane to minimize the total transportation cost for satisfying the demand of n fixed users, each supplied from its closest facility. Many heuristics have been proposed for this problem, as well as a few exact algorithms. Heuristics are needed to solve quickly large problems and to provide good initial solutions for exact algorithms. We compare various heuristics, i.e., alternative location-allocation (Cooper 1964), projection (Bongartz et al. 1994), Tabu search (Brimberg and Mladenovic 1996a), p-Median plus Weber (Hansen ct al. 1996), Genetic search and several versions of Variable Neighbourhood search. Based on empirical tests that are reported, it is found that most traditional and some recent heuristics give poor results when the number of facilities to locate is large and that Variable Neighbourhood search gives consistently best results, on average, in moderate computing time.This study was supported by the Department
of National Defence (Canada) Academic Research; Office of Naval Research Grant N00014-92-J-1194, Natural Sciences and Engineering Research Council of Canada Grant GPO 105574 and Fonds pour la Formation des Chercheurs et l’Aide a la Recherche Grant 32EQ 1048; and by an International Postdoctoral Fellowship of the Natural Sciences and Engineering Research Council
of Canada, Grant OGPOO 39682
Variations on the Author
No full text“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
No full textWe 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
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