Upper bounds for number of removed edges in the Erased Configuration Model

Models for generating simple graphs are important in the study of real-world complex networks. A well established example of such a model is the erased configuration model, where each node receives a number of half-edges that are connected to half-edges of other nodes at random, and then self-loops are removed and multiple edges are concatenated to make the graph simple. Although asymptotic results for many properties of this model, such as the limiting degree distribution, are known, the exact speed of convergence in terms of the graph sizes remains an open question. We provide a first answer by analyzing the size dependence of the average number of removed edges in the erased configuration model. By combining known upper bounds with a Tauberian Theorem we obtain upper bounds for the number of removed edges, in terms of the size of the graph. Remarkably, when the degree distribution follows a power-law, we observe three scaling regimes, depending on the power law exponent. Our results provide a strong theoretical basis for evaluating finite-size effects in networks

Directedness of Information Flow in Mobile Phone Communication Networks

Without having direct access to the information that is being exchanged, traces of information flow can be obtained by looking at temporal sequences of user interactions. These sequences can be represented as causality trees whose statistics result from a complex interplay between the topology of the underlying (social) network and the time correlations among the communications. Here, we study causality trees in mobile-phone data, which can be represented as a dynamical directed network. This representation of the data reveals the existence of super-spreaders and super-receivers. We show that the tree statistics, respectively the information spreading process, are extremely sensitive to the in-out degree correlation exhibited by the users. We also learn that a given information, e.g., a rumor, would require users to retransmit it for more than 30 hours in order to cover a macroscopic fraction of the system. Our analysis indicates that topological node-node correlations of the underlying social network, while allowing the existence of information loops, they also promote information spreading. Temporal correlations, and therefore causality effects, are only visible as local phenomena and during short time scales. Consequently, the very idea that there is (intentional) information spreading beyond a small vecinity is called into question. These results are obtained through a combination of theory and data analysis techniques

Caractérisation électrique non destructive de couches semiconductrices par mesures d'effet Hall en hyperfréquences

In this paper, a novel microwave cell is proposed, which allows Hall effect measurement for the nondestructive characterization of epilayers. This system, controlled by a microcomputer, gives the sheet resistance, the density and the mobility of the sample free carriers with the same accuracy as with the van der Pauw method. The $3\times 3$ mm sample is pressed straight on the cell without any previous technological process. We deal with the determination of the two apparatus factors from a simple calibration procedure made only once. At last, we give results concerning GaAs superficial or buried layers.Dans cet article, nous proposons une technique de caractérisation non destructive de couches semiconductrices qui utilise une cellule hyperfréquence originale permettant des mesures d'effet Hall. Ce dispositif, piloté par calculateur, fournit avec une précision analogue à celle de la méthode de van der Pauw, les grandeurs : résistance carrée, densité volumique et mobilité des porteurs libres de la couche active. L'échantillon de $3\times 3$ mm est appliqué directement sur la cellule, sans subir l'opérations technologiques préalables. Nous détaillons le procédé de détermination des deux coefficients d'appareil obtenus à partir d'un étalonnage très simple effectué une fois pour toutes. Enfin, nous donnons un ensemble de résultats relatifs à des couches de GaAs superficielles ou enterrées

Interactions between Congestion Control Algorithms

Congestion control algorithms are crucial in achieving high utilization while preventing overloading the network. Over the years, many different congestion control algorithms have been developed, each trying to improve over others inspecific situations. However, their interactions and co-existence has, to date, not been thoroughly evaluated, which is the focus of this paper. Through head-to-head comparisons of loss-based, delay-based and hybrid types of congestion control algorithms, we reveal that fairness in resources claimed is often not achieved,especially when flows sharing a link have different round-trip times or belong to different groups.<br/

Microfluidic design rules for capillary slot-based electrospray sources

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