Interest in network analysis has grown in recent years. Many social, economic and financial syste... more Interest in network analysis has grown in recent years. Many social, economic and financial systems with large numbers of interacting agents can be conveniently described by a network. In the last decade, new theories have been developed to highlight the topological properties of network architectures, despite their apparent randomness. Networks, moreover, once included in a dynamic setting, prove to be convenient mathematical tools in modeling many phenomena. This special issue of Quality and Quantity aims at providing a state-of-the-art overview of the research currently in progress at the global level, with a special focus on applications to Economics and Social Sciences. A wide range of recent advances is offered, both theoretical and methodological, that can be of interest for academics as well as practitioners. It includes nine papers, selected through a process of blind refereeing among the communications held at NET 2010 (IULM, Milano) and NET 2011 (Milano-Bicocca, Milano) Conferences. The issue comprises roughly four Sections: Network Dynamics, Network Applications, Network Modeling, Decision Modeling.
Topological structures of real networks are investigated using some relevant descriptive indicato... more Topological structures of real networks are investigated using some relevant descriptive indicators suitable for specific applicative contexts.
In this paper we present a theoretical analysis in order to establish maximal and minimal vectors... more In this paper we present a theoretical analysis in order to establish maximal and minimal vectors with respect to the majorization order of particular subsets of \Re ^n: Afterwards we apply these issues to the calcula- tion of bounds for a topological descriptor of a graph known as the second Zagreb index. Finally, we show how our bounds may improve
... Rosanna Grassi Silvana Stefani University of Milano-Bicocca, Milano, Italy ... Among the seve... more ... Rosanna Grassi Silvana Stefani University of Milano-Bicocca, Milano, Italy ... Among the several measures of centrality proposed in the literature (for a survey on centrality see Borgatti, 2005;Gomez et al., 2003; Hanneman and Riddle, 2005; Wasserman and Faust, 1997), we ...
[en]Since the academic year 2005 - 2006 a few elearning projects are active at the University Mil... more [en]Since the academic year 2005 - 2006 a few elearning projects are active at the University Milano-Bicocca, and at the Catholic University of Milano, both Faculty of Economics, with CILEA as the technological partner. They involve a large number of students attending basic courses of Mathematics. The common platform is Moodle (URL: http://moodle.org), contents are in HTML, PDF, Flash format using LO in SCORM 1.2 format.[/en]
In this paper we studied the Shareholding Network (SN) embedded in the Italian Stock Market (MIB)... more In this paper we studied the Shareholding Network (SN) embedded in the Italian Stock Market (MIB). We identified the central companies both in the role of transferring information flows and controlling companies. To this end we used betweenness and flow betweenness centrality measures, together with in and out degree. We tested the scale-free property on in and out degree, betweenness and flow betweenness centrality. The effect of external shocks to SN and the different extent on which companies react to them is measured relating asset volatility and betweenness.
The aim of this paper is to examine the effects of arbitrary changes in technological coefficient... more The aim of this paper is to examine the effects of arbitrary changes in technological coefficients on the prices in Input-output models. This analysis has been performed by splitting M-matrices into the product of suitable matrices.
Journal of Statistics and Management Systems, 2001
ABSTRACT Some new results are described, useful for locating the spectrum of a matrix through mea... more ABSTRACT Some new results are described, useful for locating the spectrum of a matrix through mean, standard deviation and third centered moment of the spectrum distribution which can be expressed in terms of traces. Sufficient conditions for a graph to be connected are given. Numerical examples are also provided, showing how former results in the literature are improved through these methods.
In this article, we investigate several issues related to the use of the index , known as the Zag... more In this article, we investigate several issues related to the use of the index , known as the Zagreb index (see Gutman and Das, 2004) or “S-metric” (Alderson and Li, 2007). We present some new upper and lower bounds for S(G), in terms of the degree sequence of G. Then, we concentrate on trees and prove that in trees with
International Journal of Intelligent Systems, 2010
In this paper we discuss the role of centrality in organizational networks. We will present some ... more In this paper we discuss the role of centrality in organizational networks. We will present some new results related to the different concepts of centrality. A case study of an ICT consulting company concludes.
This paper presents a unified approach for localizing some relevant graph topological indices via... more This paper presents a unified approach for localizing some relevant graph topological indices via majorization techniques. Through this method, old and new bounds are derived and numerical examples are provided, showing how former results in the literature could be improved.
Given a simple connected graph on N vertices with size |E| and degree sequence d 1 ≤ d 2 ≤ ... ≤ ... more Given a simple connected graph on N vertices with size |E| and degree sequence d 1 ≤ d 2 ≤ ... ≤ d N , the aim of this paper is to exhibit new upper and lower bounds for the additive degree-Kirchhoff index in closed forms, not containing effective resistances but a few invariants (N, |E| and the degrees d i ) and applicable in general contexts. In our arguments we follow a dual approach: along with a traditional toolbox of inequalities we also use a relatively newer method in Mathematical Chemistry, based on the majorization and Schur-convex functions. Some theoretical and numerical examples are provided, comparing the bounds obtained here and those previously known in the literature.
Some properties of M-matrices are investigated in order to analyze the closure of the class with ... more Some properties of M-matrices are investigated in order to analyze the closure of the class with respect to perturbations introduced in the matrix. An algorithm is derived by means of the implicit Gauss-Cholesky algorithm in the ABS class for linear systems: a lower estimation of the ...
Interest in network analysis has grown in recent years. Many social, economic and financial syste... more Interest in network analysis has grown in recent years. Many social, economic and financial systems with large numbers of interacting agents can be conveniently described by a network. In the last decade, new theories have been developed to highlight the topological properties of network architectures, despite their apparent randomness. Networks, moreover, once included in a dynamic setting, prove to be convenient mathematical tools in modeling many phenomena. This special issue of Quality and Quantity aims at providing a state-of-the-art overview of the research currently in progress at the global level, with a special focus on applications to Economics and Social Sciences. A wide range of recent advances is offered, both theoretical and methodological, that can be of interest for academics as well as practitioners. It includes nine papers, selected through a process of blind refereeing among the communications held at NET 2010 (IULM, Milano) and NET 2011 (Milano-Bicocca, Milano) Conferences. The issue comprises roughly four Sections: Network Dynamics, Network Applications, Network Modeling, Decision Modeling.
Topological structures of real networks are investigated using some relevant descriptive indicato... more Topological structures of real networks are investigated using some relevant descriptive indicators suitable for specific applicative contexts.
In this paper we present a theoretical analysis in order to establish maximal and minimal vectors... more In this paper we present a theoretical analysis in order to establish maximal and minimal vectors with respect to the majorization order of particular subsets of \Re ^n: Afterwards we apply these issues to the calcula- tion of bounds for a topological descriptor of a graph known as the second Zagreb index. Finally, we show how our bounds may improve
... Rosanna Grassi Silvana Stefani University of Milano-Bicocca, Milano, Italy ... Among the seve... more ... Rosanna Grassi Silvana Stefani University of Milano-Bicocca, Milano, Italy ... Among the several measures of centrality proposed in the literature (for a survey on centrality see Borgatti, 2005;Gomez et al., 2003; Hanneman and Riddle, 2005; Wasserman and Faust, 1997), we ...
[en]Since the academic year 2005 - 2006 a few elearning projects are active at the University Mil... more [en]Since the academic year 2005 - 2006 a few elearning projects are active at the University Milano-Bicocca, and at the Catholic University of Milano, both Faculty of Economics, with CILEA as the technological partner. They involve a large number of students attending basic courses of Mathematics. The common platform is Moodle (URL: http://moodle.org), contents are in HTML, PDF, Flash format using LO in SCORM 1.2 format.[/en]
In this paper we studied the Shareholding Network (SN) embedded in the Italian Stock Market (MIB)... more In this paper we studied the Shareholding Network (SN) embedded in the Italian Stock Market (MIB). We identified the central companies both in the role of transferring information flows and controlling companies. To this end we used betweenness and flow betweenness centrality measures, together with in and out degree. We tested the scale-free property on in and out degree, betweenness and flow betweenness centrality. The effect of external shocks to SN and the different extent on which companies react to them is measured relating asset volatility and betweenness.
The aim of this paper is to examine the effects of arbitrary changes in technological coefficient... more The aim of this paper is to examine the effects of arbitrary changes in technological coefficients on the prices in Input-output models. This analysis has been performed by splitting M-matrices into the product of suitable matrices.
Journal of Statistics and Management Systems, 2001
ABSTRACT Some new results are described, useful for locating the spectrum of a matrix through mea... more ABSTRACT Some new results are described, useful for locating the spectrum of a matrix through mean, standard deviation and third centered moment of the spectrum distribution which can be expressed in terms of traces. Sufficient conditions for a graph to be connected are given. Numerical examples are also provided, showing how former results in the literature are improved through these methods.
In this article, we investigate several issues related to the use of the index , known as the Zag... more In this article, we investigate several issues related to the use of the index , known as the Zagreb index (see Gutman and Das, 2004) or “S-metric” (Alderson and Li, 2007). We present some new upper and lower bounds for S(G), in terms of the degree sequence of G. Then, we concentrate on trees and prove that in trees with
International Journal of Intelligent Systems, 2010
In this paper we discuss the role of centrality in organizational networks. We will present some ... more In this paper we discuss the role of centrality in organizational networks. We will present some new results related to the different concepts of centrality. A case study of an ICT consulting company concludes.
This paper presents a unified approach for localizing some relevant graph topological indices via... more This paper presents a unified approach for localizing some relevant graph topological indices via majorization techniques. Through this method, old and new bounds are derived and numerical examples are provided, showing how former results in the literature could be improved.
Given a simple connected graph on N vertices with size |E| and degree sequence d 1 ≤ d 2 ≤ ... ≤ ... more Given a simple connected graph on N vertices with size |E| and degree sequence d 1 ≤ d 2 ≤ ... ≤ d N , the aim of this paper is to exhibit new upper and lower bounds for the additive degree-Kirchhoff index in closed forms, not containing effective resistances but a few invariants (N, |E| and the degrees d i ) and applicable in general contexts. In our arguments we follow a dual approach: along with a traditional toolbox of inequalities we also use a relatively newer method in Mathematical Chemistry, based on the majorization and Schur-convex functions. Some theoretical and numerical examples are provided, comparing the bounds obtained here and those previously known in the literature.
Some properties of M-matrices are investigated in order to analyze the closure of the class with ... more Some properties of M-matrices are investigated in order to analyze the closure of the class with respect to perturbations introduced in the matrix. An algorithm is derived by means of the implicit Gauss-Cholesky algorithm in the ABS class for linear systems: a lower estimation of the ...
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Papers by Anna Torriero