21,662 research outputs found
Segurança operacional de exploração florestal mecanizada.
bitstream/item/33956/1/CPATU-CirTec42.pd
Construção de estradas florestais e transporte florestal rodoviário na região amazônica.
bitstream/item/33677/1/CPATU-CirTec6.pd
Long-Time Behaviour and Self-Similarity in a Coagulation Equation with Input of Monomers
For a coagulation equation with Becker-Doring type interactions and
time-independent monomer input we study the detailed long-time behaviour of
nonnegative solutions and prove the convergence to a self-similar function.Comment: 30 pages, 5 Figures, now published in Markov Processes and Related
Fields 12, 367-398, (2006
Topology and Dynamics in Complex Networks: The Role of Edge Reciprocity
A key issue in complex systems regards the relationship between topology and
dynamics. In this work, we use a recently introduced network property known as
steering coefficient as a means to approach this issue with respect to
different directed complex network systems under varying dynamics. Theoretical
and real-world networks are considered, and the influences of reciprocity and
average degree on the steering coefficient are quantified. A number of
interesting results are reported that can assist the design of complex systems
exhibiting larger or smaller relationships between topology and dynamics
Exploração mecanizada da floresta tropical úmida sem babaçu.
bitstream/item/33767/1/CPATU-CirTec9.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
Fruticultura tropical: o biribazeiro Rollinia mucosa (Jacq.) Baill.
bitstream/item/61171/1/CPATU-Doc84.pd
Biologia floral e sistema de reprodução de Annona Squamosa L. (Annonaceae) na região de Petrolina-PE.
Aspectos da biologia da polinização e do sistema de reprodução de Annona squamosa L. foram estudadas em Petrolina-PE, Nordeste do Brasil, no período de junho de 1999 a fevereiro de 2000, entre 6:00 e 18:00h. As flores de A. squamosa são hermafroditas, axilares, com cálice e corola carnosos, formando uma câmara floral, que funciona como abrigo, fonte alimentar e/ou local de acasalamento para os visitantes florais. As flores apresentam características da síndrome de cantarofilia, tais como pétalas carnosas, de coloração clara e emissão de odores fortes e desagradáveis. A antese é crepuscular, iniciando por volta das 17 horas e a duração das flores é de aproximadamente dois dias. As flores se apresentam em fase feminina nas primeiras 20 horas e em fase masculina nas 20 horas seguintes, caracterizando a dicogamia. Carpophilus hemipterus, Carpophilus sp e Haptoncus ochraceus (Nitidulidae) são os principais visitantes, sendo considerados como polinizadores desta anonácea. A espécie autocompatível, contudo, os testes de germinação indicam que as sementes obtidas por polinização cruzada apresentam maior viabilidade do que as resultantes de geitonogamia
2D pattern evolution constrained by complex network dynamics
Complex networks have established themselves along the last years as being
particularly suitable and flexible for representing and modeling several
complex natural and human-made systems. At the same time in which the
structural intricacies of such networks are being revealed and understood,
efforts have also been directed at investigating how such connectivity
properties define and constrain the dynamics of systems unfolding on such
structures. However, lesser attention has been focused on hybrid systems,
\textit{i.e.} involving more than one type of network and/or dynamics. Because
several real systems present such an organization (\textit{e.g.} the dynamics
of a disease coexisting with the dynamics of the immune system), it becomes
important to address such hybrid systems. The current paper investigates a
specific system involving a diffusive (linear and non-linear) dynamics taking
place in a regular network while interacting with a complex network of
defensive agents following Erd\"os-R\'enyi and Barab\'asi-Albert graph models,
whose nodes can be displaced spatially. More specifically, the complex network
is expected to control, and if possible to extinguish, the diffusion of some
given unwanted process (\textit{e.g.} fire, oil spilling, pest dissemination,
and virus or bacteria reproduction during an infection). Two types of pattern
evolution are considered: Fick and Gray-Scott. The nodes of the defensive
network then interact with the diffusing patterns and communicate between
themselves in order to control the spreading. The main findings include the
identification of higher efficiency for the Barab\'asi-Albert control networks.Comment: 18 pages, 32 figures. A working manuscript, comments are welcome
Far Infrared Slab Lensing and Subwavelength Imaging in Crystal Quartz
We examine the possibility of using negative refraction stemming from the
phonon response in an anisotropic crystal to create a simple slab lens with
plane parallel sides, and show that imaging from such a lens should be possible
at room temperature despite the effects of absorption that are inevitably
present due to phonon damping. In particular, we consider the case of crystal
quartz, a system for which experimental measurements consistent with all-angle
negative refraction have already been demonstrated. Furthermore, we investigate
the possibility of subwavelength imaging from such materials, and show that it
should be possible for certain configurations.Comment: 12 pages, 10 figure
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