17,041 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
Geometric Phase, Curvature, and Extrapotentials in Constrained Quantum Systems
We derive an effective Hamiltonian for a quantum system constrained to a
submanifold (the constraint manifold) of configuration space (the ambient
space) by an infinite restoring force. We pay special attention to how this
Hamiltonian depends on quantities which are external to the constraint
manifold, such as the external curvature of the constraint manifold, the
(Riemannian) curvature of the ambient space, and the constraining potential. In
particular, we find the remarkable fact that the twisting of the constraining
potential appears as a gauge potential in the constrained Hamiltonian. This
gauge potential is an example of geometric phase, closely related to that
originally discussed by Berry. The constrained Hamiltonian also contains an
effective potential depending on the external curvature of the constraint
manifold, the curvature of the ambient space, and the twisting of the
constraining potential. The general nature of our analysis allows applications
to a wide variety of problems, such as rigid molecules, the evolution of
molecular systems along reaction paths, and quantum strip waveguides.Comment: 27 pages with 1 figure, submitted to Phys. Rev.
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