Luciano da Fontoura Costa
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View article: A Systematic Approach for Studying How Topological Measurements Respond to Complex Networks Modifications
A Systematic Approach for Studying How Topological Measurements Respond to Complex Networks Modifications Open
Different types of graphs and complex networks have been characterized, analyzed, and modeled based on measurements of their respective topology. However, the available networks may constitute approximations of the original structure as a …
View article: An Analytical Approach to the Jaccard Similarity Index
An Analytical Approach to the Jaccard Similarity Index Open
The Jaccard similarity index has often been employed in science and technology as a means to quantify the similarity between two sets. When modified to operate on real-valued values, the Jaccard similarity index can be applied to compare v…
View article: Normalization in Proportional Feature Spaces
Normalization in Proportional Feature Spaces Open
The subject of features normalization plays an important central role in data representation, characterization, visualization, analysis, comparison, classification, and modeling, as it can substantially influence and be influenced by all o…
View article: Supervised Pattern Recognition Involving Skewed Feature Densities
Supervised Pattern Recognition Involving Skewed Feature Densities Open
Pattern recognition constitutes a particularly important task underlying a great deal of scientific and technologica activities. At the same time, pattern recognition involves several challenges, including the choice of features to represe…
View article: Agglomerative Clustering in Uniform and Proportional Feature Spaces
Agglomerative Clustering in Uniform and Proportional Feature Spaces Open
Pattern comparison represents a fundamental and crucial aspect of scientific modeling, artificial intelligence, and pattern recognition. Three main approaches have typically been applied for pattern comparison: (i) distances; (ii) statisti…
View article: Simple Games on Complex Networks
Simple Games on Complex Networks Open
The relationship between topology and dynamics of complex systems has motivated continuing interest from the scientific community. In the present work, we address this interesting topic from the perspective of simple games, involving two t…
View article: Subsuming Complex Networks by Node Walks
Subsuming Complex Networks by Node Walks Open
The concept of node walk in graphs and complex networks has been addressed, consisting of one or more nodes that move into adjacent nodes, henceforth incorporating the respective connections. This type of dynamics is then applied to subsum…
View article: Node Accessibility Characterization of Radially-Grown Structures
Node Accessibility Characterization of Radially-Grown Structures Open
Complex systems have motivated continuing interest from the scientific community, leading to new concepts and methods. Growing systems represent a case of particular interest, as their topological, geometrical, and also dynamical propertie…
View article: Using full-text content to characterize and identify best seller books: A study of early 20th-century literature
Using full-text content to characterize and identify best seller books: A study of early 20th-century literature Open
Artistic pieces can be studied from several perspectives, one example being their reception among readers over time. In the present work, we approach this interesting topic from the standpoint of literary works, particularly assessing the …
View article: Hierarchical Cutting of Complex Networks Performed by Random Walks
Hierarchical Cutting of Complex Networks Performed by Random Walks Open
Several interesting approaches have been reported in the literature on complex networks, random walks, and hierarchy of graphs. While many of these works perform random walks on stable, fixed networks, in the present work we address the si…
View article: Detecting Groups in Directed and Non-Directed Bipartite Networks
Detecting Groups in Directed and Non-Directed Bipartite Networks Open
Bipartite networks provide an effective resource for representing, characterizing, and modeling several abstract and real-world systems and structures involving binary relations, which include food webs, social interactions, and customer-p…
View article: Random Walks Performed by Topologically-Specific Agents on Complex Networks
Random Walks Performed by Topologically-Specific Agents on Complex Networks Open
Random walks by single-node agents have been systematically conducted on various types of complex networks in order to investigate how their topologies can affect the dynamics of the agents. However, by fitting any network node, these agen…
View article: Quantifying the hierarchical adherence of modular documents
Quantifying the hierarchical adherence of modular documents Open
Several natural and artificial structures are characterized by an intrinsic hierarchical organization. The present work describes a methodology for quantifying the degree of adherence between a given hierarchical template and a respective …
View article: Parallel and Sequential Resources Networks
Parallel and Sequential Resources Networks Open
A large number of real and abstract systems involve the transformation of some basic resource into respective products under the action of multiple processing agents, which can be understood as multiple-agent production systems (MAP). At e…
View article: Simple Bundles of Complex Networks
Simple Bundles of Complex Networks Open
Complex networks can be used to represent and model an ample diversity of abstract and real-world systems and structures. A good deal of the research on these structures has focused on specific topological properties, including node degree…
View article: Multilayer Multiset Neuronal Networks -- MMNNs
Multilayer Multiset Neuronal Networks -- MMNNs Open
The coincidence similarity index, based on a combination of the Jaccard and overlap similarity indices, has noticeable properties in comparing and classifying data, including enhanced selectivity and sensitivity, intrinsic normalization, a…
View article: Astroglial Hmgb1 regulates postnatal astrocyte morphogenesis and cerebrovascular maturation
Astroglial Hmgb1 regulates postnatal astrocyte morphogenesis and cerebrovascular maturation Open
Astrocytes are intimately linked with brain blood vessels, an essential relationship for neuronal function. However, astroglial factors driving these physical and functional associations during postnatal brain development have yet to be id…
View article: Two Approaches to Supervised Image Segmentation
Two Approaches to Supervised Image Segmentation Open
Though performed almost effortlessly by humans, segmenting 2D gray-scale or color images into respective regions of interest (e.g.~background, objects, or portions of objects) constitutes one of the greatest challenges in science and techn…
View article: Análise e visualização do processo de regionalização do Sistema Único de Saúde (SUS): Uma perspectiva em sistemas complexos
Análise e visualização do processo de regionalização do Sistema Único de Saúde (SUS): Uma perspectiva em sistemas complexos Open
O processo de regionalização de saúde no Brasil tem o objetivo de garantir o direito à saúde da população, reduzindo as desigualdades sociais e territoriais. Uma região de saúde é composta por uma coleção de municípios adjacentes, organiza…
View article: Cross-Relation Characterization of Knowledge Networks
Cross-Relation Characterization of Knowledge Networks Open
Knowledge networks have become increasingly important as a changing repository of data which can be represented, studied and modeled by using complex networks concepts and methodologies. Here we report a study of knowledge networks corresp…
View article: Astroglial<i>Hmgb1</i>regulates postnatal astrocyte morphogenesis and cerebrovascular maturation
Astroglial<i>Hmgb1</i>regulates postnatal astrocyte morphogenesis and cerebrovascular maturation Open
Astrocytes are intimately linked with brain vessels, a relationship that is critical for neuronal health and function. However, astroglial factors driving these physical and functional associations during postnatal brain development have y…
View article: On the Transient and Equilibrium Features of Growing Fractal Complex Networks
On the Transient and Equilibrium Features of Growing Fractal Complex Networks Open
Complex networks have certain properties that distinguish them from their respective uniform or regular counterparts. One of these properties is the variation of topological properties along different hierarchical levels. In this work, we …
View article: A Global Approach to Local Approximations
A Global Approach to Local Approximations Open
Space and shape have special importance in science and technology, as they underly an impressive range of realworld structures and phenomena. Thanks to concepts and methods from calculus, it becomes possible to approximate functions, curve…
View article: Calculus of Variations: Nature's Parsimonious Self-Computation
Calculus of Variations: Nature's Parsimonious Self-Computation Open
In addition to being intrinsically interesting, calculus of variations constitutes an area that has been extensively considered in both theoretic and applied areas, underlying a large number of structures and phenomena, including the stati…
View article: A Journey into the Multifaceted Universe of Coordinates Change, Basis Transformation, Dual Spaces, and Invariance
A Journey into the Multifaceted Universe of Coordinates Change, Basis Transformation, Dual Spaces, and Invariance Open
The present work aims as developing, in a progressive manner, several concepts from linear and multilinear algebra that are progressively integrated from basic operations up to rudiments of tensors. The covered subjects include brief histo…
View article: Single Point Particle Motion: Mass, Force, Momenta, Impulse, Work
Single Point Particle Motion: Mass, Force, Momenta, Impulse, Work Open
In this work, which mostly constitutes a sequence of a previous work (Point Motion in Flat Spaces: An Ample Starting Point), we approach the interesting problem of representing and studying the position, velocity, acceleration and forces o…
View article: Autorrelation and cross-relation of graphs and networks
Autorrelation and cross-relation of graphs and networks Open
The concepts of auto- and cross-correlation play a key role in several areas, including signal processing and analysis, pattern recognition, multivariate statistics, as well as physics in general, as these operations underlie several real-…
View article: Point Motion in Flat Spaces: An Ample Starting Point
Point Motion in Flat Spaces: An Ample Starting Point Open
In this work, we approach the interesting problem of representing and studying the position, velocity, acceleration and arc-length of trajectories of points defined in a two-dimensional geometrical space, which has been chosen for being si…
View article: The Exponential Function: A Mathemagical Hub
The Exponential Function: A Mathemagical Hub Open
The exponential function, including its real-and complex-values forms, constitutes one of the most important concepts in mathematics. In this work, the exponential function is approached in a progressive manner. After some brief historical…
View article: Identification of city motifs: a method based on modularity and similarity between hierarchical features of urban networks
Identification of city motifs: a method based on modularity and similarity between hierarchical features of urban networks Open
Several natural and theoretical networks can be broken down into smaller portions, henceforth called neighborhoods. The more frequent of these can then be understood as motifs of the network, being therefore important for better characteri…