Phase transition in conservative diffusive contact processes

We determine the phase diagrams of conservative diffusive contact processes by means of numerical simulations. These models are versions of the ordinary diffusive single-creation, pair-creation and triplet-creation contact processes in which the particle number is conserved. The transition between the frozen and active states was determined by studying the system in the subcritical regime and the nature of the transition, whether continuous or first order, was determined by looking at the fractal dimension of the critical cluster. For the single-creation model the transition remains continuous for any diffusion rate. For pair- and triplet-creation models, however, the transition becomes first order for high enough diffusion rate. Our results indicate that in the limit of infinite diffusion rate the jump in density equals 2/3 for the pair-creation model and 5/6 for the triplet-creation model

The Highest Geomagnetic Storms of the Solar Cycle Observed at Ground Level

We report two ground-level observations, of geomagnetic storms of different origins; they are among the highest geomagnetic storms, in the solar Cycle 24. The first is St. Patrick’s Day storm on March 17, 2015, originated by the impact on Earth’s atmosphere of coronal mass ejections (CMEs), the storm reaching the condition of G4 (severe) level, in the NOAA geomagnetic scale. The second included the major geomagnetic storm whose origin is attributed to the interaction with the Earth of a High-Speed Stream (HSS) ahead of a positive polarity coronal hole on October 7, 2015. This storm reached the condition G3 (strong) level. We give emphasis to observations detected by the New-Tupi muon telescopes, located at sea level in Brazil (22.53° S, 43.13° W). We present a study of these observations in correlation with observations reported by multipoint space-based measurements, such as the ACE at Lagrange Point L1 and the geostationary GOES weather satellite, including two global geomagnetic indices and several ground-based detectors. Some considerations on the influence of these geomagnetic storms in the Earth weather are reported

On agent-based modelling of large scale conflict against a central authority: from mechanisms to complex behaviour

In this work, an Agent-Based model of large scale conflict against a central authority was developed. The model proposed herein is an extension of Epstein's Agent-Based model of civil violence, in which new mechanisms such as deprivation-dependent hardship, generalised vanishing of the risk perception (`massive fear loss') below a critical ratio between deterrence and `group support', legitimacy feedback, network influences and `mass enthusiasm' (contagion) were implemented. The model was explored a set of computer experiments and the results compared with statistical analyses of events in the "Arab Spring". The main contributions of the present work for understanding how mechanisms of large scale conflict lead to complex behaviour were (i ) a quantitative description of the impact of the \Arab Spring" in several countries focused on complexity issues such as peaceful vs violent, spontaneous vs organized, and patterns of size, duration and recurrence of conflict events; (ii ) the explanation of the relationship between the estimated arrest probability and the size of rebellion peaks in Epstein's model; (iii ) a new form of the estimated arrest probability with a mechanism of `massive fear loss'; (iv ) the derivation of a relationship between the legitimacy and action threshold for complex solutions to occur with both low and high values of the legitimacy; (v) a simple representation of political vs economic deprivation with a parameter which controls the `sensitivity' to value; (vi ) the effect of legitimacy feedback; and (vii ) the effect of network influences on the stability of the solutions.Neste trabalho, é apresentado um modelo baseado em agentes para o estudo do conflito massivo contra uma autoridade central. O modelo proposto é uma extensão do modelo baseado em agentes para o estudo da violência civil devido a Epstein, incluindo os mecanismos de relação entre a privação relativa e 'provação' (hardship), desaparecimento generalizado da percepção de risco abaixo de uma relação crítica entre a capacidade de dissuasão e o `apoio colectivo', a retroalimentação da legitimidade em função da contestação, as influências associadas as redes, e o mecanismo do `entusiasmo colectivo' (contágio). O modelo foi explorado através de um conjunto de experiências de simulação, e os resultados comparados com uma análise estatística de eventos ocorridos durante a "Primavera Árabe". Os principais contributos do presente trabalho foram (i ) a descrição quantitativa do impacto da "Primavera Árabe" em diversos países, focada em aspectos de complexidade; (ii ) a explicação da relação entre a função de estimativa de probabilidade de prisão e a magnitude dos picos de revolta social; (iii ) uma nova forma para a função de estimativa de probabilidade de prisão, como mecanismo de `perda generalizada do medo'; (iv ) a dedução de uma relação entre a legitimidade e o limiar de acção para a ocorrência de soluções com comportamento complexo, tanto para valores elevados como baixos da legitimidade; (v) uma representação simples da privação política e da privação económica, com um parâmetro regulador da `sensibilidade' ao valor; (vi ) a introdução do mecanismo de retroalimentação da legitimidade; e (vii ) o efeito das influências devidas a redes na estabilidade das soluções

Preservation of vernacular schist masonry farm walls

This paper complements the information presented at the CIAV2013 on vernacular build- ings in northern Portugal, and addresses the topic of masonry walls in the rural areas of the northwestern Portuguese coastline. These walls are structural schist masonry constructions, built using ancient tech- niques and locally available resources. The result is a territory built for agricultural exploration, and a landscape imprinted with past social hierarchies and structures. Using the information gathered by the fieldwork study, the paper will present studies on masonry walls with different morphologies, construction materials and building techniques employed. The information presented aims to contribute to enlighten researchers and technicians about these building specificities, to increase the scarce available literature about schist’s potential as construction material, and to enhance the importance of the cultural value of this particular kind of heritage

Impact of delays on costumers'safety perceptions and behavioral intentions

Purpose: The main objective of this paper is to examine how the customers' perceptions of delays and safety relate to each other and to behavioral intentions Design/methodology/approach: We modified a customer satisfaction questionnaire to include questions relating to the constructs we wanted to examine and collaborated with a major international airline to collect data from 797 customers through in-flight surveys. Findings: We obtain three key original findings. First, perceived safety exerts a direct positive effect on behavioral intentions. Second, perceived delays exert an indirect effect mediated by perceived safety. Finally, customers believe operational practices affect both delay and safety. Originality/value: This is the first paper that examines the customer's perspective on two of the most important aspects of airline operations management: delays and safety. Our findings are of great value to managers who want to evaluate the impact of delays and safety on customers and to researches interested in the theoretical relationships between these two constructs.Peer Reviewe

Stochastic thermodynamics of opinion dynamics

We show that models of opinion formation and dissemination in a community of individuals can be framed within stochastic thermodynamics from which we can build a nonequilibrium thermodynamics of opinion dynamics. This is accomplished by decomposing the original transition rate that defines an opinion model into two or more transition rates, each representing the contact with heat reservoirs at different temperatures, and postulating an energy function. As the temperatures are distinct, heat fluxes are present even at the stationary state and linked to the production of entropy, the fundamental quantity that characterizes nonequilibrium states. We apply the present framework to a generic-vote model including the majority-vote model in a square lattice and in a cubic lattice. The fluxes and the rate of entropy production are calculated by numerical simulation and by the use of a pair approximation