Long-Range Connections in Transportation Networks

Since its recent introduction, the small-world effect has been identified in several important real-world systems. Frequently, it is a consequence of the existence of a few long-range connections, which dominate the original regular structure of the systems and implies each node to become accessible from other nodes after a small number of steps, typically of order $\ell \propto \log N$. However, this effect has been observed in pure-topological networks, where the nodes have no spatial coordinates. In this paper, we present an alalogue of small-world effect observed in real-world transportation networks, where the nodes are embeded in a hree-dimensional space. Using the multidimensional scaling method, we demonstrate how the addition of a few long-range connections can suubstantially reduce the travel time in transportation systems. Also, we investigated the importance of long-range connections when the systems are under an attack process. Our findings are illustrated for two real-world systems, namely the London urban network (streets and underground) and the US highways network enhanced by some of the main US airlines routes

On time-varying collaboration networks

The patterns of scientific collaboration have been frequently investigated in terms of complex networks without reference to time evolution. In the present work, we derive collaborative networks (from the arXiv repository) parameterized along time. By defining the concept of affine group, we identify several interesting trends in scientific collaboration, including the fact that the average size of the affine groups grows exponentially, while the number of authors increases as a power law. We were therefore able to identify, through extrapolation, the possible date when a single affine group is expected to emerge. Characteristic collaboration patterns were identified for each researcher, and their analysis revealed that larger affine groups tend to be less stable

Informações tecnológicas para a exportação de coco verde livre da podridão-basal-pós-colheita.

bitstream/item/48172/1/CIT11001.pd

Random walks in directed modular networks

Because diffusion typically involves symmetric interactions, scant attention has been focused on studying asymmetric cases. However, important networked systems underlain by diffusion (e.g. cortical networks and WWW) are inherently directed. In the case of undirected diffusion, it can be shown that the steady-state probability of the random walk dynamics is fully correlated with the degree, which no longer holds for directed networks. We investigate the relationship between such probability and the inward node degree, which we call efficiency, in modular networks. Our findings show that the efficiency of a given community depends mostly on the balance between its ingoing and outgoing connections. In addition, we derive analytical expressions to show that the internal degree of the nodes do not play a crucial role in their efficiency, when considering the Erd\H{o}s-R\'enyi and Barab\'asi-Albert models. The results are illustrated with respect to the macaque cortical network, providing subsidies for improving transportation and communication systems

Controle da lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) na cultura do milho com inseticidas aplicados via irrigacao por aspersão.

No periodo de 1988 a 1994 foram conduzidos experimentos para avaliar a eficiencia de inseticidas aplicados via irrigacao por aspersao com equipamento tipo lateral portatil, para o controle da lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith) atacando a cultura do milho (Zea mays L.). No estadio de cinco a seis folhas, as parcelas experimentais foram infestadas artificialmente usando 10 lagartas recem-eclodidas/planta, dois dias antes da aplicacao dos inseticidas. A eficiencia dos inseticidas foi avaliada tres, 10 ou 15 dias apos a aplicacao, contando-se o numero de lagartas vivas coletadas em 50 plantas ao acaso por parcela. Clorpirifos (288,0 gi.a/ha) foi o mais eficiente (82,9 a 98,7%) no controle de S. frugiperda, sendo seguido por carbary (1105.0 gi.a/ha) (84,0%) diazinon (480,0 gi.a/ha) (83,4%), lambdacialotrina (10,0 gi.a/ha) (81,3%), triflumuron (2,5 gi.a/ha) (79,9%) e diflubenzuron (50.0 gi.a/ha) (73,3%)

Fitomolestias identificadas na microrregiao do litoral piauiense: 1988-1997.

bitstream/item/96085/1/CT740001.pd