5,858 research outputs found
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 .
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
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