1,721,526 research outputs found
Algebraic connectivity of interdependent networks
No full textThe algebraic connectivity μN-1, i.e. the second smallest eigenvalue of the Laplacian matrix, plays a crucial role in dynamic phenomena such as diffusion processes, synchronization stability, and network robustness. In this work we study the algebraic connectivity in the general context of interdependent networks, or network-of-networks (NoN). The present work shows, both analytically and numerically, how the algebraic connectivity of NoNs experiences a transition. The transition is characterized by a saturation of the algebraic connectivity upon the addition of sufficient coupling links (between the two individual networks of a NoN). In practical terms, this shows that NoN topologies require only a fraction of coupling links in order to achieve optimal diffusivity. Furthermore, we observe a footprint of the transition on the properties of Fiedler's spectral bisection. © 2014 Elsevier B.V. All rights reserved
Todorov. Il vagabondaggio umano di un grande intellettuale
No full textIl saggio riflette sui temi affrontati da Tzvetan Todorov in uno dei suoi ultimi libri, Una vita da passatore
When a text is translated does the complexity of its vocabulary change? Translations and target readerships
No full textIn linguistic studies, the academic level of the vocabulary in a text can be described in terms of statistical physics by using a ''temperature'' concept related to the text's word-frequency distribution. We propose a ''comparative thermo-linguistic'' technique to analyze the vocabulary of a text to determine its academic level and its target readership in any given language. We apply this technique to a large number of books by several authors and examine how the vocabulary of a text changes when it is translated from one language to another. Unlike the uniform results produced using the Zipf law, using our ''word energy'' distribution technique we find variations in the power-law behavior. We also examine some common features that span across languages and identify some intriguing questions concerning how to determine when a text is suitable for its intended readership. Copyright
Cascades in interdependent flow networks
No full textIn this manuscript, we investigate the abrupt breakdown behavior of coupled distribution grids under load growth. This scenario mimics the ever-increasing customer demand and the foreseen introduction of energy hubs interconnecting the different energy vectors. We extend an analytical model of cascading behavior due to line overloads to the case of interdependent networks and find evidence of first order transitions due to the long-range nature of the flows. Our results indicate that the foreseen increase in the couplings between the grids has two competing effects: on the one hand, it increases the safety region where grids can operate without withstanding systemic failures; on the other hand, it increases the possibility of a joint systems' failure. © 2015 Elsevier B.V. Graphical abstract
The complexity science approach vs. the simulative approach
No full textThe chapter starts with the description of the state-of-the-art and the literature review, while introducing the general context of the simulative and complexity science methodologies applied to the critical information infrastructure protection. While introducing the general context, the authors illustrate the methodologies and their applications. The major objective is to investigate the pros and cons to facilitate the choice between the mainstream lines of research in critical information infrastructure protection. Theoretical and practical issues are balanced in order to provide the reader with a wider understanding of the problems at hand and with the appropriate methodological tools to face them. This discussion on the state-of-the-art by no means can be considered exhaustive, depending on the personal views of the authors and on the room available, nevertheless it is meant to explain the trends and the relevant points in the field. It is also worth mentioning, moreover, that with respect to other CI (oil, gas, power grid, etc.), only a small number of CII modelling case studies are available. The reader should be aware that the intention of the authors is not to provide a deep, theoretical, or philosophical analysis of the issue under consideration, rather to help from a practical point of view. © 2013, IGI Global
Effect of the interconnected network structure on the epidemic threshold
No full textMost real-world networks are not isolated. In order to function fully, they are interconnected with other networks, and this interconnection influences their dynamic processes. For example, when the spread of a disease involves two species, the dynamics of the spread within each species (the contact network) differs from that of the spread between the two species (the interconnected network). We model two generic interconnected networks using two adjacency matrices, A and B, in which A is a 2N×2N matrix that depicts the connectivity within each of two networks of size N, and B a 2N×2N matrix that depicts the interconnections between the two. Using an N-intertwined mean-field approximation, we determine that a critical susceptible-infected- susceptible (SIS) epidemic threshold in two interconnected networks is 1/λ1(A+αB), where the infection rate is β within each of the two individual networks and αβ in the interconnected links between the two networks and λ1(A+αB) is the largest eigenvalue of the matrix A+αB. In order to determine how the epidemic threshold is dependent upon the structure of interconnected networks, we analytically derive λ1(A+αB) using a perturbation approximation for small and large α, the lower and upper bound for any α as a function of the adjacency matrix of the two individual networks, and the interconnections between the two and their largest eigenvalues and eigenvectors. We verify these approximation and boundary values for λ1(A+αB) using numerical simulations, and determine how component network features affect λ1(A+αB). We note that, given two isolated networks G1 and G2 with principal eigenvectors x and y, respectively, λ1(A+αB) tends to be higher when nodes i and j with a higher eigenvector component product x iyj are interconnected. This finding suggests essential insights into ways of designing interconnected networks to be robust against epidemics. © 2013 American Physical Society
Adopting the cloud to manage the electricity grid
No full textPublic utilities, such as electricity, telecommunication, natural gas, water or sewage, constitute services whose proper functioning is of paramount importance for the whole society. Among these critical infrastructures, power grid and telecommunication network are, probably, the most critical ones. Their interdependency could exacerbate the consequence of a failure since the telecommunication network devices are powered by the mains, while the nationwide power grid is managed through a SCADA system that relies on the public telecommunication network. Cloud technology could reduce costs and improve performance but its adoption should be cautiously evaluated relatively to a critical infrastructure. We qualitatively discuss the cloud adoption in such a kind of infrastructure. Then, a topological analysis, concerning network reliability and robustness, is performed focusing on the SCADA system of the Italian power transmission network. Results show that a certain cloud configuration could be beneficial for the power transmission network. © 2016 IEEE
Come il mondo ha cambiato i social media
No full textCome il mondo ha cambiato i social media è il volume complessivo di comparazione
dei risultati di un’ampia indagine etnografica, coordinata da Daniel
Miller, dall’eloquente titolo Why we Post. Nove ricercatori, incluso Miller,
hanno trascorso 15 mesi sul campo, in diversi paesi del mondo (Italia del
sud, Turchia sudorientale, due siti in Cina, area rurale e area industriale,
Trinidad, Inghilterra, India del sud, Cile settentrionale e Brasile) a osservare
e studiare, con un approccio etnografico, i modi in cui le persone usano i
social media. È un fatto indiscutibile che i social sono entrati nella nostra
vita con prepotenza, in modo capillare, per certi aspetti invasivo. Con un
linguaggio fluido, talvolta anche colloquiale, il lettore è condotto all’interno
di un ambito che gli sembra di conoscere, se non altro perché ne siamo tutti,
più o meno, utenti, scoprendo però quanto di valori, di comportamenti
culturalmente codificati, di ‘polizia morale’ ci sia dentro i social media.
L’approccio qui presentato parte infatti da un’idea un po’ diversa rispetto a
quelle più diffuse, e avvalorata nel corso della ricerca: se è indubbio che i social
media hanno cambiato il mondo, la questione più interessante riguarda
però il modo in cui il mondo li ha cambiati
The robustness of assortativity (short paper)
No full textComplex networks are ubiquitous in real word and represent a key model for both human made and natural systems. An important characteristics that distinguishes technological networks from biological networks is the assortativity, i.e. the correlation among the degrees of connected nodes. We apply spectral analysis to investigate how assortativity influences the robustness of a network with respect to failure propagations or epidemic spreading. We find a no free lunch situation: while disassortative networks are more robust since they have a higher failure threshold, in assortative networks there is more time for intervention before total breakdown. © 2013 Springer-Verlag
The formation of the "Verb" category: from Pre-Semitic to Semitic
Full text linkThe present work aims at describing the formation of the Semitic verb, with close reference to the Akkadian period. Thus, I will provide a detailed analysis of the basic conjugation of the Old Babylonian dialect. During the discourse, it will emerge that the basic conjugational forms (i.e., the perfective iprVs and the stative parVs) come from pre-Semitic nominal and adjectival elements that have gradually entered into a fully-fledged verbal system. More specifically, it will be argued that the Akkadian iprVs develops from a nominal nucleus to which personal pronouns are attached (later, it will be used for the conjugation of the fientive verbs), whereas parVs is said to be originally engaged as the predicative form of adjectives (later, it will be used for the conjugation of the state verbs). The specific formal modifications, like the coalescence of the nominal and pronominal elements into one and semantic redefinitions underlying the verbalization process will be shown in detail
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