2,714 research outputs found
Aspectos geológicos do Estado do Acre e implicações na evolução da paisagem.
bitstream/item/32345/1/doc104.pd
Zoneamento geológico e geomorfológico entre Feijó e Mâncio Lima: Acre.
Introdução; Metodologia; Geologia da área; Geomorfologia da área; Anexosbitstream/CPAF-AC/15627/1/doc99.pd
Electrostatics of electron-hole interactions in van der Waals heterostructures
The role of dielectric screening of electron-hole interaction in van der
Waals heterostructures is theoretically investigated. A comparison between
models available in the literature for describing these interactions is made
and the limitations of these approaches are discussed. A simple numerical
solution of Poissons equation for a stack of dielectric slabs based on a
transfer matrix method is developed, enabling the calculation of the
electron-hole interaction potential at very low computational cost and with
reasonable accuracy. Using different potential models, direct and indirect
exciton binding energies in these systems are calculated within Wannier-Mott
theory, and a comparison of theoretical results with recent experiments on
excitons in two-dimensional materials is discussed.Comment: 10 pages, 8 figure
All-strain based valley filter in graphene nanoribbons using snake states
A pseudo-magnetic field kink can be realized along a graphene nanoribbon
using strain engineering. Electron transport along this kink is governed by
snake states that are characterized by a single propagation direction. Those
pseudo-magnetic fields point towards opposite directions in the K and K'
valleys, leading to valley polarized snake states. In a graphene nanoribbon
with armchair edges this effect results in a valley filter that is based only
on strain engineering. We discuss how to maximize this valley filtering by
adjusting the parameters that define the stress distribution along the graphene
ribbon.Comment: 8 pages, 6 figure
Logarithmic periodicities in the bifurcations of type-I intermittent chaos
The critical relations for statistical properties on saddle-node bifurcations
are shown to display undulating fine structure, in addition to their known
smooth dependence on the control parameter. A piecewise linear map with the
type-I intermittency is studied and a log-periodic dependence is numerically
obtained for the average time between laminar events, the Lyapunov exponent and
attractor moments. The origin of the oscillations is built in the natural
probabilistic measure of the map and can be traced back to the existence of
logarithmically distributed discrete values of the control parameter giving
Markov partition. Reinjection and noise effect dependences are discussed and
indications are given on how the oscillations are potentially applicable to
complement predictions made with the usual critical exponents, taken from data
in critical phenomena.Comment: 4 pages, 6 figures, accepted for publication in PRL (2004
Evolução geológica e geomorfológica do Estado do Acre e implicações na estratificação de ambientes.
Os dados apresentados neste capítulo são baseados, em grande parte, no banco de dados de recursos naturais do Sipam/IBGE (Sistema de Proteção da Amazônia/Instituto Brasileiro de Geografia e Estatística) e foram gerados em escala 1:100.000, mas publicados em escala 1:250.000, servindo como um dos temas primários para a elaboração do mapa de gestão territorial do ZEE/AC
- …