Peer and authority pressure in information-propagation models (MA thesis)

Existing models of information diffusion assume that peer influence is the main reason of the observed propagation patterns. This work examines the role of authority pressure on the observed information cascades. We model this intuition by characterizing some nodes in the network as “authority” nodes. These are nodes that can influence large number of peers, while themselves cannot be influenced by peers. We propose a model that associates with every item two parameters that quantify the impact of peer and the authority pressure on the item’s propagation. Given a network and the observed diffusion patterns of the item, we learn these parameters from the data and characterize the item as peer- or authority-propagated. We also develop a randomization test that evaluates the statistical significance of our findings and makes our item characterization robust to noise. Our experiments with real data from online media and scientific-collaboration networks indicate that there is a strong signal of authority pressure in these networks

Ubiquitousness of link-density and link-pattern communities in real-world networks

Community structure appears to be an intrinsic property of many complex real-world networks. However, recent work shows that real-world networks reveal even more sophisticated modules than classical cohesive (link-density) communities. In particular, networks can also be naturally partitioned according to similar patterns of connectedness among the nodes, revealing link-pattern communities. We here propose a propagation based algorithm that can extract both link-density and link-pattern communities, without any prior knowledge of the true structure. The algorithm was first validated on different classes of synthetic benchmark networks with community structure, and also on random networks. We have further applied the algorithm to different social, information, technological and biological networks, where it indeed reveals meaningful (composites of) link-density and link-pattern communities. The results thus seem to imply that, similarly as link-density counterparts, link-pattern communities appear ubiquitous in nature and design

Corrosion induced cracking modelled by a coupled transport-structural approach

Transport of corrosion products into pores and cracks in concrete must be considered when predicting corrosion induced cracking in reinforced concrete structures, since this transport significantly delays the onset of cracking and spalling by reducing the amount of radial displacement imposed on the concrete at the steel/concrete interface. We aim to model this process by means of a coupled transport-structural approach, whereby the transport of corrosion products is determined by a pressure gradient generated by the confined volumetric expansion due to the transformation of steel into corrosion products. This pressure driven transport was studied by using both an axisymmetric thick-walled cylinder model and a network approach. The network approach was then applied to corrosion induced cracking experiments reported in the literature

Underwater acoustic impulsive noise monitoring in port facilities: Case study of the Port of Cartagena

Recording underwater impulsive noise data is an important aspect of mitigating its environmental impact and improving maritime environmental management systems. This paper describes the method used and results of the spatial monitoring of both the baseline noise level and the impulsive noise sources in the Port of Cartagena. An autonomous vessel was equipped with a smart digital hydrophone with a working frequency range between 10 and 200 kHz and a received voltage response (RVR) of, approximately, −170 dB re 1V/µPa. A GIS map was drawn up with the spatiotemporal distribution of the basal sound pressure levels by coupling the acoustic data with the vessel’s GPS positions to identify the sources of the impulsive noise of interest and their temporal characteristics. The loading of cargo containers was identified as the main source of impulse noise. This study is the first of a series designed to obtain accurate information on underwater noise pollution and its potential impact on biodiversity in the Port of Cartagena.We would like to thank the Cartagena Port Authority for their general support in the operational campaign. This research was funded by the Cátedra de Medio Ambiente Autoridad Portuaria de Cartagena-Campus Mare Nostrum

Look Before You Leap: A Skeptical View of Proposals to Meld Macro- and Microprudential Regulation

G-20 ministers should avoid creating a new layer of regulation to counter future systemic financial risks, according to a newly released C.D Howe Institute study. The Commentary by Nick Le Pan, former Superintendent of Financial Institutions, cautions against current G-20 proposals to expand regulation to include system-wide macroeconomic risks.financial services, Bank of Canada, OSFI, systemic risk, procyclicality, Basel II