10,790 research outputs found
Negative-Energy Perturbations in Circularly Cylindrical Equilibria within the Framework of Maxwell-Drift Kinetic Theory
The conditions for the existence of negative-energy perturbations (which
could be nonlinearly unstable and cause anomalous transport) are investigated
in the framework of linearized collisionless Maxwell-drift kinetic theory for
the case of equilibria of magnetically confined, circularly cylindrical plasmas
and vanishing initial field perturbations. For wave vectors with a
non-vanishing component parallel to the magnetic field, the plane equilibrium
conditions (derived by Throumoulopoulos and Pfirsch [Phys Rev. E {\bf 49}, 3290
(1994)]) are shown to remain valid, while the condition for perpendicular
perturbations (which are found to be the most important modes) is modified.
Consequently, besides the tokamak equilibrium regime in which the existence of
negative-energy perturbations is related to the threshold value of 2/3 of the
quantity , a new
regime appears, not present in plane equilibria, in which negative-energy
perturbations exist for {\em any} value of . For various analytic
cold-ion tokamak equilibria a substantial fraction of thermal electrons are
associated with negative-energy perturbations (active particles). In
particular, for linearly stable equilibria of a paramagnetic plasma with flat
electron temperature profile (), the entire velocity space is
occupied by active electrons. The part of the velocity space occupied by active
particles increases from the center to the plasma edge and is larger in a
paramagnetic plasma than in a diamagnetic plasma with the same pressure
profile. It is also shown that, unlike in plane equilibria, negative-energy
perturbations exist in force-free reversed-field pinch equilibria with a
substantial fraction of active particles.Comment: 31 pages, late
Negative-energy perturbations in cylindrical equilibria with a radial electric field
The impact of an equilibrium radial electric field on negative-energy
perturbations (NEPs) (which are potentially dangerous because they can lead to
either linear or nonlinear explosive instabilities) in cylindrical equilibria
of magnetically confined plasmas is investigated within the framework of
Maxwell-drift kinetic theory. It turns out that for wave vectors with a
non-vanishing component parallel to the magnetic field the conditions for the
existence of NEPs in equilibria with E=0 [G. N. Throumoulopoulos and D.
Pfirsch, Phys. Rev. E 53, 2767 (1996)] remain valid, while the condition for
the existence of perpendicular NEPs, which are found to be the most important
perturbations, is modified. For ( is the
electrostatic potential) and ( is
the total plasma pressure), a case which is of operational interest in magnetic
confinement systems, the existence of perpendicular NEPs depends on ,
where is the charge of the particle species . In this case the
electric field can reduce the NEPs activity in the edge region of tokamaklike
and stellaratorlike equilibria with identical parabolic pressure profiles, the
reduction of electron NEPs being more pronounced than that of ion NEPs.Comment: 30 pages, late
Manejo e utilização de plantas forrageiras dos genêros Panicum brachiaria e Cynodon.
bitstream/item/37976/1/Documentos34-0.pdf2. ed. rev
Conservação de propágulos de cajueiro anão precoce para enxertia por borbulhia.
No presente trabalho, foram testados varios tipos de materiais com o objetivo de se determinar as condicoes mais adequadas para o acondicionamento de propagulos, fornecedores de borbulhas de cajueiro anao precoce, mantendo sua viabilidade, mesmo quando se necessitar de mais de tres dias para se proceder a enxertia.bitstream/CNPAT-2010/5352/1/Ct-020.pd
Produção de propágulos em jardim clonal de cajueiro anão precoce irrigado e adensado.
bitstream/CNPAT-2010/5596/1/Pa-025.pd
Produção de propágulos de acerola (Malphighia glabra L.) em jardim clonal irrigado e com alta densidade de plantio.
bitstream/CNPAT-2010/5597/1/Pa-026.pd
Evaluation of Physical Properties of Coffee during Roasting
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 5 (2003): M. Rodrigues, M. Borges, A. Franca, L. Oliveira, and P. Correa. Evaluation of Physical Properties of Coffee during Roasting. Vol. V. December 2003
Recuperação de pomares jovens de cajueiro anão precoce pela substituição de copa.
A substituicao de copaem plantas jovens de cajueiro anao-precoce e uma alternativa eficaz para dar iniformidade e aumentar a producao dos pomares formados com mudas propagadas por semente; (...) A substituicao de copa permite, a partir do quarto ano de frutificacao ...bitstream/CNPAT-2010/5354/1/Ct-023.pd
Efeito do número de brotações enxertadas na produção do cajueiro anão precoce com copa substituída (Anacardium occidentale L.).
Trabalho ... demostra a viabilidade da substituicao de copa, como alternativa de recuperar pomares de cajueiro constituidos de mudas de pe franco.bitstream/CNPAT-2010/5353/1/Ct-024.pd
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