Programa de Pós-graduação em Ciência da Computação em Rede
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Navegando Programa de Pós-graduação em Ciência da Computação em Rede por Por Orientador "Barbosa, Rommel Melgaço"
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Item Sobre grafos com r tamanhos diferentes de conjuntos independentes maximais e algumas extensões(Universidade Federal de Goiás, 2014-10-01) Cappelle, Márcia Rodrigues; Barbosa, Rommel Melgaço; http://lattes.cnpq.br/6228227125338610; Barbosa, Rommel Melgaço; Abreu, Nair Maria Maia de; Santos, José Plínio de Oliveira; Longo, Humberto José; Silva, Hebert Coelho daIn this thesis, we present some results concerning about the sizes of maximal independent sets in graphs. We prove that for integers r and D with r 2 and D 3, there are only finitely many connected graphs of minimum degree at least 2, maximum degree at most D, and girth at least 7 that have maximal independent sets of at most r different sizes. Furthermore, we prove several results restricting the degrees of such graphs. These contributions generalize known results on well-covered graphs. We study the structure and recognition of the well-covered graphs G with order n(G) without an isolated vertex that have independence number n(G)k 2 for some non-negative integer k. For k = 1, we give a complete structural description of these graphs, and for a general but fixed k, we describe a polynomial time recognition algorithm. We consider graphs G without an isolated vertex for which the independence number a(G) and the independent domination number i(G) satisfy a(G) i(G) k for some non-negative integer k. We obtain a upper bound on the independence number in these graphs. We present a polynomial algorithm to recognize some complementary products, which includes all complementary prisms. Also, we present results on well-covered complementary prisms. We show that if G is not well-covered and its complementary prism is well-covered, then G has only two consecutive sizes of maximal independent sets. We present an upper bound for the quantity of sizes of maximal independent sets in complementary prisms and other wellcovered concerning results. We present a lower bound for the quantity of different sizes of maximal independent sets in Cartesian products of paths and cycles.Item Sobre convexidade em prismas complementares(Universidade Federal de Goiás, 2015-04-10) Duarte, Márcio Antônio; Szwarcfiter, Jayme L.; http://lattes.cnpq.br/2002515486942024; Barbosa, Rommel Melgaço; http://lattes.cnpq.br/6228227125338610; Barbosa, Rommel Melgaço; Yanasse, Horacio Hideki; Oliveira, Carla Silva; Coelho, Erika Morais Martins; Silva, Hebert Coelho daIn this work, we present some related results, especially the properties algoritimics and of complexity of a product of graphs called complementary prism. Answering some questions left open by Haynes, Slater and van der Merwe, we show that the problem of click, independent set and k-dominant set is NP-Complete for complementary prisms in general. Furthermore, we show NP-completeness results regarding the calculation of some parameters of the P3-convexity for the complementary prism graphs in general, as the P3-geodetic number, P3-hull number and P3-Carathéodory number. We show that the calculation of P3-geodetic number is NP-complete for complementary prism graphs in general. As for the P3-hull number, we can show that the same can be efficiently computed in polynomial time. For the P3-Carathéodory number, we show that it is NPcomplete complementary to prisms bipartite graphs, but for trees, this may be calculated in polynomial time and, for class of cografos, calculating the P3-Carathéodory number of complementary prism of these is 3. We also found a relationship between the cardinality Carathéodory set of a graph and a any Carathéodory set of complementary prism. Finally, we established an upper limit calculation the parameters: geodetic number, hull number and Carathéodory number to operations complementary prism of path, cycles and complete graphs considering the convexities P3 and geodesic.Item Mínimos quadrados para problemas de múltiplas classes envolvendo twin support vector machine e aplicações de mineração de dados(Universidade Federal de Goiás, 2018-12-07) Lima, Márcio Dias de; Barbosa, Rommel Melgaço; http://lattes.cnpq.br/6228227125338610; Barbosa, Rommel Melgaço; Santos, Helton Saulo Bezerra dos; Lozano, Kátia Kelvis Cassiano; Costa, Ronaldo Martins da; Rosa, Thierson CoutoData mining is an emerging area due to the increasing amount of data available in a variety of fields. In this context twin support vector machine (TWSVM) has attracted the attention of several researchers. In this thesis, we developed a feature selector algorithm and an algorithm for multi-class problems based on TWSVM. This learning algorithm with ternary outputs {- 1,0,+1 } is based on the Vapnik support vector theory, and evaluates all training samples with a 1-×-1-×-rest structure during the decomposition phase. One of the main advantages of the proposed algorithm is the use of the least squares version for multi-class problems, where it is necessary to solve two systems of linear equations instead of two quadratic programming problems in TWSVM. We also implemented the principle of minimization of structural risk in order to improve the generalizability. The Sherman-Morisson-Woodbury formula is applied to reduce the complexity of the non-linear formulation of the algorithm. We also apply data mining techniques that combine the use of analytical technique with data mining algorithms in the classification of several samples. The developed framework could be an excellent tool for detecting different types of fraud, verifying if products were grown in organic or conventional systems, as well as tracing the region of origin of wine made from a given type of grape.Item Balanceamento de dados com base em oversampling em dados transformados(Universidade Federal de Goiás, 2020-08-17) Maione, Camila; Barbosa, Rommel Melgaço; http://lattes.cnpq.br/6228227125338610; Barbosa, Rommel Melgaço; Leitão Júnior, Plínio; Costa, Ronaldo Martins da; Costa, Ana Paula Cabral Seixas; Lozano, Kátia Kelvis CassianoIntroduction: The efficiency and reliability of data analyses depends heavily on the quality of the analyzed data. The fundamental process of preparing databases in order to make them cleaner, more representative and improve their quality is called data preprocessing, during which data balancing is also performed. The importance of data balancing lies in the fact that several classification models commonly employed in enterprises and academic projects are designed to work with balanced data sets, and there are several factors which hinder classification performance which are associated to data imbalance. Objective: A new approach for data balancing based on data transformation combined with resampling of transformed data is proposed. The proposed approach transforms the original data set by transforming its input variables into new ones, therefore altering the data samples' position in the dimensional plane and consequently the choice that SMOTE-based resampling algorithms make over the initial samples, their nearest neighbours and where to place the generated synthetic samples. Methods: An initial implementation based on Principal Component Analysis (PCA) and SMOTE is presented, called PCA-SMOTE. In order to test the quality of the balancing performed by PCA-SMOTE, twelve test data sets were balanced through PCA-SMOTE and three other popular data balancing methods, and the performance of three classification models trained on these balanced sets are assessed and compared. Results: Several classification models trained on data sets which were balanced using the proposed method presented higher or similar performance measures in comparison to the same models trained on data sets that were balanced through the other evaluated algorithms, such as Borderline-SMOTE, Safe-Level-SMOTE and ADASYN. Conclusion: The satisfactory results obtained prove the potential of the proposed algorithm to improve learning of classifiers on imbalanced data sets.