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Dive into the research topics where Nair Maria Maia de Abreu is active.

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Featured researches published by Nair Maria Maia de Abreu.


European Journal of Operational Research | 2007

A survey for the quadratic assignment problem

Eliane Maria Loiola; Nair Maria Maia de Abreu; Paulo Oswaldo Boaventura-Netto; Peter M. Hahn; Tania Querido

The quadratic assignment problem (QAP), one of the most difficult problems in the NP-hard class, models many real-life problems in several areas such as facilities location, parallel and distributed computing, and combinatorial data analysis. Combinatorial optimization problems, such as the traveling salesman problem, maximal clique and graph partitioning can be formulated as a QAP. In this paper, we present some of the most important QAP formulations and classify them according to their mathematical sources. We also present a discussion on the theoretical resources used to define lower bounds for exact and heuristic algorithms. We then give a detailed discussion of the progress made in both exact and heuristic solution methods, including those formulated according to metaheuristic strategies. Finally, we analyze the contributions brought about by the study of different approaches.


Discrete Applied Mathematics | 2010

Bounds on the index of the signless Laplacian of a graph

Carla Silva Oliveira; Leonardo Silva de Lima; Nair Maria Maia de Abreu; Pierre Hansen

A shock absorber apparatus connected in series relationship respective to the polished rod and bridle of a pumpjack unit. The shock absorber includes a housing within which there is supported a plurality of resilient packer members stacked in sandwiched relationship. The packer members have an axial passageway formed therethrough, with the passageway of each packer member being aligned with one another, so that the polished rod is telescopingly received therethrough. The bottom of the housing is supported by the bridle, while the polished rod is supported by a plate member which bears against the uppermost packer member. This places all of the resilient packer members in compression, with the force of the compression being proportional to the weight of the sucker rod.


Linear Algebra and its Applications | 2002

The characteristic polynomial of the Laplacian of graphs in (a,b)-linear classes

Carla Silva Oliveira; Nair Maria Maia de Abreu; Samuel Jurkiewicz

In this work we deal with the characteristic polynomial of the Laplacian of a graph. We present some general results about the coefficients of this polynomial. We present families of graphs, for which the number of edges m is given by a linear function of the number of vertices n. In some of these graphs we can find certain coefficients of the above-named polynomial as functions just of n.


Applied Mathematics Letters | 2008

Constructing pairs of equienergetic and non-cospectral graphs

Andréa S. Bonifácio; Cybele T. M. Vinagre; Nair Maria Maia de Abreu

Abstract The energy of a simple graph G is the sum of the absolute values of the eigenvalues of its adjacency matrix. Two graphs of the same order are said to be equienergetic if they have the same energy. Several ways to construct equienergetic non-cospectral graphs of very large size can be found in the literature. The aim of this work is to construct equienergetic non-cospectral graphs of small size. In this way, we first construct several special families of such graphs, using the product and the cartesian product of complete graphs. Afterwards, we show how one can obtain new pairs of equienergetic non-cospectral graphs from the starting ones. More specifically, we characterize the connected graphs G for which the product and the cartesian product of G and K 2 are equienergetic non-cospectral graphs and we extend Balakrishnan’s result: For a non-trivial graph G , G ⊗ C 4 and G ⊗ K 2 ⊗ K 2 are equienergetic non-cospectral graphs, given in [R. Balakrishnan, The energy of a graph, Linear Algebra Appl. 387 (2004) 287–295].


Discrete Applied Mathematics | 2002

Classes of quadratic assignment problem instances: isomorphism and difficulty measure using a statistical approach

Nair Maria Maia de Abreu; Paulo Oswaldo Boaventura Netto; Tania Querido; Elizabeth Ferreira Gouvea

In this work, we introduce the variance expression for quadratic assignment problem (QAP) costs. We also define classes of QAP instances, described by a common linear relaxation form. The use of the variance in these classes leads to the study of isomorphism and allows for a definition of a new difficulty index for QAP instances. This index is then compared to a classical measure found in the literature.


Archive | 2005

Variable Neighborhood Search for Extremal Graphs. XI. Bounds on Algebraic Connectivity

Slim Belhaiza; Nair Maria Maia de Abreu; Pierre Hansen; Carla Silva Oliveira

The algebraic connectivity a(G) of a graph G = (V, E) is the second smallest eigenvalue of its Laplacian matrix. Using the AutoGraphiX (AGX) system, extremal graphs for algebraic connectivity of G in function of its order n = |V| and size m = |E| are studied. Several conjectures on the structure of those graphs, and implied bounds on the algebraic connectivity, are obtained. Some of them are proved, e.g., if G ≠ K n


Electronic Journal of Linear Algebra | 2013

Maxima of the Q-index:graphs with bounded clique number

Nair Maria Maia de Abreu; Vladimir Nikiforov


Electronic Journal of Linear Algebra | 2010

EXTREMAL ALGEBRAIC CONNECTIVITIES OF CERTAIN CATERPILLAR CLASSES AND SYMMETRIC CATERPILLARS

Oscar Rojo; Luis A. Medina; Nair Maria Maia de Abreu; Claudia Justel

a\left( G \right) \leqslant \left\lfloor { - 1 + \sqrt {1 + 2m} } \right\rfloor


Pesquisa Operacional | 2000

GRASP para o PQA: um limite de aceitação para soluções iniciais

Maria Cristina Range; Nair Maria Maia de Abreu; Paulo Oswaldo Boaventura-Netto


Pesquisa Operacional | 2004

Uma revisão comentada das abordagens do problema quadrático de alocação

Eliane Maria Loiola; Nair Maria Maia de Abreu; Paulo Oswaldo Boaventura Netto

which is sharp for all m ≥ 2.

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Carla Silva Oliveira

Brazilian Institute of Geography and Statistics

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Leonardo Silva de Lima

Centro Federal de Educação Tecnológica de Minas Gerais

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Maria Aguieiras A. de Freitas

Federal University of Rio de Janeiro

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Oscar Rojo

Catholic University of the North

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Claudia Justel

Instituto Militar de Engenharia

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Lilian Markenzon

Federal University of Rio de Janeiro

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Maria Cristina Rangel

Federal University of Rio de Janeiro

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Renata R. Del-Vecchio

Federal Fluminense University

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