1,594 research outputs found
Avaliação do impacto ambiental de sistemas intensivos de produção de carne bovina conduzidos em pastagens.
bitstream/CPPSE/17576/1/Boletim14.pdfISSN 1981-207
Field-theoretical renormalization group for a flat two-dimensional Fermi surface
We implement an explicit two-loop calculation of the coupling functions and
the self-energy of interacting fermions with a two-dimensional flat Fermi
surface in the framework of the field theoretical renormalization group (RG)
approach. Throughout the calculation both the Fermi surface and the Fermi
velocity are assumed to be fixed and unaffected by interactions. We show that
in two dimensions, in a weak coupling regime, there is no significant change in
the RG flow compared to the well-known one-loop results available in the
literature. However, if we extrapolate the flow to a moderate coupling regime
there are interesting new features associated with an anisotropic suppression
of the quasiparticle weight Z along the Fermi surface, and the vanishing of the
renormalized coupling functions for several choices of the external momenta.Comment: 16 pages and 22 figure
Condutividade hidráulica saturada de campo em pastagens tropicais submetidas a exploração intensiva da pastagem.
Foram realizadas medições de CHSC, utilizando permeâmetro de Guelph, em Latossolo Vermelho-Amarelo Distrófico tÃpico (26% argila), Latossolo Vermelho Distrófico tÃpico (29% argila), Latossolo Vermelho Distroférrico (antigo Latossolo Roxo; 40% argila) e Nitossolo Vermelho Eutroférrico (antiga Terra Roxa Estruturada; 45% argila), nas profundidades de 10, 20 e 60 cm. O objetivo foi verificar se os manejos das pastagens são adequados para manter as propriedades fÃsicas favoráveis do solo. Os resultados mostraram que tanto na exploração extensiva como intensiva da pastagem, evitando-se superpastejo, houve manutenção ou mesmo aumento da CHSC na camada de 0 a 10 cm, e que variou de 0,8 a 4,1 m/h, dependendo do tipo de solo
Final-state, Open-loop Control of the Heat equation in Tensorial Domains (full version)
In this paper, a quadratic optimal control problem will be considered for the
heat equation in tensorial domains with homogeneous Dirichlet boundary
conditions, in which the control function (depending only on time) constitutes
a source term. These problems involve choosing a control function (with or
without "peak-value" constraints) to approximately steer the solution of the
heat equation to a desired function at the end of a prescribed (finite)
time-interval. To compute approximations to the desired optimal control
functions, semi-discrete, spectral (with eigenfunctions) Galerkin
approximations to the corresponding heat equation and the corresponding
(approximating) control problems are tackled. Two simple, illustrative examples
are presented in the final section.Comment: 32 pages, 11 figures, submitte
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