12,157 research outputs found
On Galois-Division Multiple Access Systems: Figures of Merit and Performance Evaluation
A new approach to multiple access based on finite field transforms is
investigated. These schemes, termed Galois-Division Multiple Access (GDMA),
offer compact bandwidth requirements. A new digital transform, the Finite Field
Hartley Transform (FFHT) requires to deal with fields of characteristic p, p
\neq 2. A binary-to-p-ary (p \neq 2) mapping based on the opportunistic
secondary channel is introduced. This allows the use of GDMA in conjunction
with available digital systems. The performance of GDMA is also evaluated.Comment: 6 pages, 4 figures. In: XIX Simposio Brasileiro de Telecomunicacoes,
2001, Fortaleza, CE, Brazi
Tailoring magnetic anisotropy in epitaxial half metallic La0.7Sr0.3MnO3 thin films
We present a detailed study on the magnetic properties, including anisotropy,
reversal fields, and magnetization reversal processes, of well characterized
half-metallic epitaxial La0.7Sr0.3MnO3 (LSMO) thin films grown onto SrTiO3
(STO) substrates with three different surface orientations, i.e. (001), (110)
and (1-18). The latter shows step edges oriented parallel to the [110]
(in-plane) crystallographic direction. Room temperature high resolution
vectorial Kerr magnetometry measurements have been performed at different
applied magnetic field directions in the whole angular range. In general, the
magnetic properties of the LSMO films can be interpreted with just the uniaxial
term with the anisotropy axis given by the film morphology, whereas the
strength of this anisotropy depends on both structure and film thickness. In
particular, LSMO films grown on nominally flat (110)-oriented STO substrates
presents a well defined uniaxial anisotropy originated from the existence of
elongated in-plane [001]-oriented structures, whereas LSMO films grown on
nominally flat (001)-oriented STO substrates show a weak uniaxial magnetic
anisotropy with the easy axis direction aligned parallel to residual substrate
step edges. Elongated structures are also found for LSMO films grown on vicinal
STO(001) substrates. These films present a well-defined uniaxial magnetic
anisotropy with the easy axis lying along the step edges and its strength
increases with the LSMO thickness. It is remarkable that this step-induced
uniaxial anisotropy has been found for LSMO films up to 120 nm thickness. Our
results are promising for engineering novel half-metallic magnetic devices that
exploit tailored magnetic anisotropy.Comment: 10 pages, 10 figures, 1 tabl
Avaliação do nível de dano de Heliothis virencens (Lepidoptera: Noctuidae) em soja.
A lagarta-da-maçã Heliothis virescens (Lepidoptera: Noctuidae) é uma praga já conhecida pelos cotonicultores, e tem causando danos a cultura da soja em algumas regiões, alimentando-se de folhas de estruturas reprodutivas, flores e vagens. Diante dessa problemática esse trabalho teve como objetivo avaliar os níveis de dano de H. virencens em soja a partir do estádio R4 (Vagens completamente desenvolvidas). O experimento foi conduzido na área experimental da Fundação Goiás, situada na cidade de Santa Helena de Goiás na safra de 2011-2012, com a cultivar Monsoy 7211 RR (crescimento indeterminado) em gaiolas de contenção de 1 x 1 x 1 m, em duas linhas de semeadura com total de 30 plantas por parcela. O delineamento experimental foi de blocos ao acaso com quatro níveis de infestação (0, 1, 3, e 6 lagartas de 3º instar.gaiola-1) e quatro repetições, as lagartas foram mantidas nas gaiolas até a fase de pupa. Foram avaliados os seguintes parâmetros: porcentagem de vagens injuriadas (PVI), grãos danificados (PGD) e produtividade (kg.ha-1). Os dados foram submetidos à análise de variância, e as médias ao teste de Tukey (p ≤ 0,05). Entre os parâmetros avaliados verificou-se diferença estatística entre a porcentagem de vagens injuriadas e grãos danificados, de acordo com a densidade de lagartas. As PVI e PGD respectivas a cada infestação (lagartas.gaiola-1) foram: (0) 0,0; 0,0; (1) 3,3%; 3,3%; (3) 10,3%; 11,7% e (6) 23,0; 25,5%. Os valores de produtividade mesmo não diferindo estatisticamente, mostram um decréscimo entre os tratamentos, que foram respectivamente: (0) 2616,25; (1) 2510,50; (3) 2530,0 (6) 2487,25 kg.ha -1. Os maiores danos foram observados no tratamento com 6 lagartas.gaiola-1 em relação com demais tratamentos
Extra polarization states of cosmological gravitational waves in alternative theories of gravity
Cosmological Gravitational Waves (GWs) are usually associated with the
transverse-traceless part of the metric perturbations in the context of the
theory of cosmological perturbations. These modes are just the usual
polarizations `+' and `x' which appear in the general relativity theory.
However, in the majority of the alternative theories of gravity, GWs can
present more than these two polarization states. In this context, the
Newman-Penrose formalism is particularly suitable for evaluating the number of
non-null GW modes. In the present work we intend to take into account these
extra polarization states for cosmological GWs in alternative theories of
gravity. As an application, we derive the dynamical equations for cosmological
GWs for two specific theories, namely, a general scalar-tensor theory which
presents four polarization states and a massive bimetric theory which is in the
most general case with six polarization states for GWs. The mathematical tool
presented here is quite general, so it can be used to study cosmological
perturbations in all metric theories of gravity.Comment: 26 pages, 1 figure. Accepted for publication in Classical and Quantum
Gravity
Comitê da suinocultura da região da AMAUC: a trajetória do TAC da suinocultura.
Projeto: 06.09.06.001
Percepção sobre as perspectivas da agricultura familiar na região do Alto Uruguai Catarinense.
Projeto/Plano de Ação: 06.09.06.001
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