A model of assessment of collateral damage on power grids based on complex network theory

As power grids are gradually adjusted to fit into a smart grid paradigm, a common problem is to identify locations where it is most beneficial to introduce distributed generation. In order to assist in such a decision, we work on a graph model of a regional power grid, and propose a method to assess collateral damage to the network resulting from a localized failure. We perform complex network analysis on multiple instances of the network, looking for correlations between estimated damages and betweenness centrality indices, attempting to determine which model is best suited to predict features of our network

Computation of generalized matrix functions

We develop numerical algorithms for the efficient evaluation of quantities associated with generalized matrix functions [J. B. Hawkins and A. Ben-Israel, Linear and Multilinear Algebra 1(2), 1973, pp. 163-171]. Our algorithms are based on Gaussian quadrature and Golub--Kahan bidiagonalization. Block variants are also investigated. Numerical experiments are performed to illustrate the effectiveness and efficiency of our techniques in computing generalized matrix functions arising in the analysis of networks.Comment: 25 paged, 2 figure

Can the observed large scale magnetic fields be seeded by helical primordial fields?

Gravitational wave production induces a strong constraint on the amplitude of a primordial magnetic field. It has been shown that the nucleosynthesis bound for a stochastic gravitational wave background implies that causally generated fields cannot have enough power on large scales to provide the seeds necessary for the observed magnetic fields in galaxies and clusters, even by the most optimistic dynamo amplification. Magnetic fields generated at inflation can have high enough amplitude only if their spectrum is very red. Here we show that helicity, which leads to an inverse cascade, can mitigate these limits. In particular, we find that helical fields generated at the QCD phase transition or at inflation with red spectrum are possible seeds for the dynamo. Helical fields generated at the electroweak phase transition are instead excluded as seeds at large scales. We also calculate the spectrum of gravitational waves generated by helical magnetic fields.Comment: 41 pages, 12 figure

Regularized solution of a nonlinear problem in electromagnetic sounding

We propose a regularization method to solve a nonlinear ill-posed problem connected to inversion of data gathered by a ground conductivity meter

How to increase reach effeciency and effectiveness of MEO's Digital marketing campaings: programmatic buying & targeting techniques

Field lab: Business projectThis paper draws on two new trends in the digital marketing environment: programmatic buying and targeting techniques. These topics arose as the main responses to increase digital marketing campaigns’ efficiency and effectiveness, as requested during a Field Lab carried out at a leading Portuguese telecommunication and media services operator. Once the reader is introduced to the environment in which the project was performed and the reference literature, theoretical recommendations for a strategic implementation of these techniques, and a practical example to increase the targeting efficiency, are provided, passing through the conclusions of four main research techniques that led to these choices