Search results for "Complex networks"
showing 9 items of 49 documents
Analysis of the Structure and Dynamics of European Flight Networks
2022
We analyze structure and dynamics of flight networks of 50 airlines active in the European airspace in 2017. Our analysis shows that the concentration of the degree of nodes of different flight networks of airlines is markedly heterogeneous among airlines reflecting heterogeneity of the airline business models. We obtain an unsupervised classification of airlines by performing a hierarchical clustering that uses a correlation coefficient computed between the average occurrence profiles of 4-motifs of airline networks as similarity measure. The hierarchical tree is highly informative with respect to properties of the different airlines (for example, the number of main hubs, airline participa…
Community-based method for extracting backbones
2022
Networks are an adequate representation for modeling and analyzing a great variety of complex systems. However, understanding networks with millions of nodes and billions of connections can be pretty challenging due to memory and time constraints. Therefore, selecting the relevant nodes and edges of these large-scale networks while preserving their core information is a major issue. In most cases, the so-called backbone extraction methods are based either on coarse-graining or filtering approaches. Coarse-graining techniques reduce the network size by gathering similar nodes into super-nodes, while filter-based methods eliminate nodes or edges according to a statistical property. In this wo…
A primer on statistically validated networks
2019
In this contribution we discuss some approaches of network analysis providing information about single links or single nodes with respect to a null hypothesis taking into account the heterogeneity of the system empirically observed. With this approach, a selection of nodes and links is feasible when the null hypothesis is statistically rejected. We focus our discussion on approaches using i) the so-called disparity filter and ii) statistically validated network in bipartite networks. For both methods we discuss the importance of using multiple hypothesis test correction. Specific applications of statistically validated networks are discussed. We also discuss how statistically validated netw…
Anagraphical relationships and crime specialization within Cosa Nostra
2021
Abstract The aim of the present work is to investigate the relationships established within Cosa Nostra, by making use of networks and complex-systems methods. The analysis is performed at three different levels, that is, individuals, groups within mafia syndicates, and relationships amongst mafia syndicates. The reported empirical analysis is based on the criminal records of 632 affiliates to Cosa Nostra selected from a set of 125 judgements emitted by the Palermo courts from 2000 to 2014. According to the criminal records of the Palermo Prosecutor Office, such a dataset includes approximately 10% of the whole population of Cosa Nostra affiliates in western Sicily. Furthermore, the vital s…
Persistence in complex systems
2022
Persistence is an important characteristic of many complex systems in nature, related to how long the system remains at a certain state before changing to a different one. The study of complex systems' persistence involves different definitions and uses different techniques, depending on whether short-term or long-term persistence is considered. In this paper we discuss the most important definitions, concepts, methods, literature and latest results on persistence in complex systems. Firstly, the most used definitions of persistence in short-term and long-term cases are presented. The most relevant methods to characterize persistence are then discussed in both cases. A complete literature r…
Transitions out of unemployment: The role of social networks' topology and firms' recruitment strategies
2011
In this paper we study the effects of job contact networks on out-of-unemployment transitions. We find that social connections produce sizable increases in upward mobility from unemployment and, caeteris paribus, symmetric network topologies perform better than asymmetric ones. Furthermore, in scale-free networks the probability of transitions out of unemployment increases in the exponent of the power-law degree distribution, but its value is much lower than the one attainable in Poisson random networks. In addition, and most interestingly, these results strongly depends on the different hypotheses on the firms' recruitment strategy.
Science of success: An introduction
2019
Performance and success are often used as synonyms to express individual accomplishment. However, from a scientific perspective they cover very different concepts: performance is about individual effort, while success is a collective quantity capturing the community's acknowledgment of effort and performance. In these notes, we investigate the quantitative rules that govern both, trying to model their interdependence within the framework of complex systems. We explore different fields, ranging from online crowdfunding platforms to academia, with the idea of applying scientifically sound methods to uncover the universal laws that determine the allocation of merit in science and society.
A bibliometric analysis of cultural heritage research in the humanities: The Web of Science as a tool of knowledge management
2023
AbstractSubstantial research on the topic of cultural heritage has been conducted over the past two decades. At the same time, the overall output volume of journals and citation metrics have become important parameters in assessing and ranking researchers’ performance. Even though the scholarly interest in cultural heritage has recently increased world-wide, a comprehensive analysis of the publication output volume and its correlation to the shift in the cultural heritage regime starting in 2003 is still lacking. The article aims to understand the role of Web of Science (WOS) as a tool of knowledge management in academia by drawing on the scholarly output volume, the patterns displayed by t…
Sparsity-aware multiple relay selection in large multi-hop decode-and-forward relay networks
2016
In this paper, we propose and investigate two novel techniques to perform multiple relay selection in large multi-hop decode-and-forward relay networks. The two proposed techniques exploit sparse signal recovery theory to select multiple relays using the orthogonal matching pursuit algorithm and outperform state-of-the-art techniques in terms of outage probability and computation complexity. To reduce the amount of collected channel state information (CSI), we propose a limited-feedback scheme where only a limited number of relays feedback their CSI. Furthermore, a detailed performance-complexity tradeoff investigation is conducted for the different studied techniques and verified by Monte …