1,713 research outputs found
Spin relaxation times in disordered graphene
We consider two mechanisms of spin relaxation in disordered graphene. i) Spin
relaxation due to curvature spin orbit coupling caused by ripples. ii) Spin
relaxation due to the interaction of the electronic spin with localized
magnetic moments at the edges. We obtain analytical expressions for the spin
relaxation times, tau_SO and tau_J due to both mechanisms and estimate their
values for realistic parameters of graphene samples. We obtain that spin
relaxation originating from these mechanisms is very weak and spin coherence is
expected in disordered graphene up to samples of length L ~ 1 micron.Comment: To appear in the Proceedings of the Graphene Conference, MPI PKS
Dresden, September 2006. Corrected typo
Elementary Charge Transfer Processes in a Superconductor-Ferromagnet Entangler
We study the production of spatially separated entangled electrons in
ferromagnetic leads from Cooper pairs in a superconducting lead. We give a
complete description of the elementary charge transfer processes, i) transfer
of Cooper pairs out of the superconductor by Andreev reflection and ii)
distribution of the entangled quasiparticles among the ferromagnetic leads, in
terms of their statistics. The probabilities that entangled electrons flow into
spatially separated leads are completely determined by experimentally
measurable conductances and polarizations. Finally, we investigate how
currents, noise and cross correlations are affected by transport of entangled
electrons.Comment: 5 pages. Rewritten manuscript with 2 new figures. Title changed from
v
Spin transport in proximity induced ferromagnetic graphene
Magnetic gates in close proximity to graphene can induce ferromagnetic
correlations. We study the effect of such induced magnetization dependent
Zeeman splittings on the graphene transport properties. We estimate that
induced spin splittings of the order of \Delta ~ 5 meV could be achieved with
the use of magnetic insulator gates, e.g. EuO-gates, deposited on top of
graphene. We demonstrate that such splittings in proximity induced
ferromagnetic graphene could be determined directly from the tunneling
resonances in the linear response conductance, as the top gate creates also a
tunable barrier in the graphene layer. We show how such splittings could also
be determined independently by magnetoresistance measurements in a spin-valve
geometry. Because the spin polarization of the current near the Dirac point
increases with the length of the barrier, long magnetic gates are desirable for
determining \Delta experimentally.Comment: 9 pages, 11 figure
The role of road freight in Uberlândia (Brazil), logistics epicenter of wholesaler-distributor sector
In structured analysis from the theory of geographical space and the circuits of urban economy, this article aims to demonstrate the peculiarities and territorial dynamics that confirmed the insertion of the Uberlândia (MG) nodal point like one of centralities of road freight transport geographical network, whose territorial configuration consists of nodals and lines which together express the organization and structuring of this activity in the Brazilian social and spatial formation. Furthermore, it show a selective spatial process that privileged certain points and areas in detriment of others, marked by concentration and action of its agents. The research concludes that the inclusion of Uberlândia in the geographical proposed network occurs because of the close relationship between the agents of road freight and wholesaler-distributor sector.Em análise estruturada a partir da teoria do espaço geográfico e dos circuitos da economia urbana, este artigo pretende demonstrar as peculiaridades e dinâmicas territoriais que corroboram a inserção do ponto nodal de Uberlândia (MG) como uma das centralidades da rede geográfica do transporte rodoviário de carga, cuja configuração territorial é composta por linhas e nodais que em seu conjunto expressam a organização e estruturação desta atividade na formação socioespacial brasileira. Além disso, evidenciam um processo de seletividade espacial que privilegiou certos pontos e áreas em detrimento de outros, demarcado pela concentração e atuação de seus agentes. A pesquisa conclui que a inserção de Uberlândia na rede geográfica proposta se dá por causa da estreita relação entre os agentes do transporte rodoviário de carga e do setor atacadista-distribuidor.Universidade Federal de São Paulo (UNIFESP)UNIFESP, EPPEN, Osasco, BrazilSciEL
Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids
The electrical resistance of ferromagnetic/normal-metal (F/N)
heterostructures depends on the nature of the junctions which may be tunnel
barriers, point contacts, or intermetallic interfaces. For all junction types,
the resistance of disordered F/N/F perpendicular spin valves as a function of
the angle between magnetization vectors is shown to obey a simple universal
law. The spin-current induced magnetization torque can be measured by the
angular magnetoresistance of these spin valves. The results are generalized to
arbitrary magnetoelectronic circuits
From Digital to Analogue Magnetoelectronics: Theory of Transport in Non-Collinear Magnetic Nanostructures
Magnetoelectronics is mainly digital, i.e. governed by up and down
magnetizations. In contrast, analogue magnetoelectronics makes use of phenomena
occuring for non-collinear magnetization configurations. Here we review
theories which have recently been applied to the transport in non-collinear
magnetic nanostructures in two and multiterminal structures, viz. random matrix
and circuit theory. Both are not valid for highly transparent systems in a
resistive environment like perpendicular metallic spin valves. The solution to
this problem is a renormalization of the conventional and spin-mixing
conductance parameters.Comment: To be published in "Advance in Solid State Physics", edited by B.
Kramer, Springer Verlag, Berlin, 200
Adaptive comfort control implemented model (ACCIM) for energy consumption predictions in dwellings under current and future climate conditions: A case study located in Spain
Currently, the knowledge of energy consumption in buildings of new and existing dwellings is essential to control and propose energy conservation measures. Most of the predictions of energy consumption in buildings are based on fixed values related to the internal thermal ambient and pre-established operation hypotheses, which do not reflect the dynamic use of buildings and users’ requirements. Spain is a clear example of such a situation. This study suggests the use of an adaptive thermal comfort model as a predictive method of energy consumption in the internal thermal ambient, as well as several operation hypotheses, and both conditions are combined in a simulation model: the Adaptive Comfort Control Implemented Model (ACCIM). The behavior of ACCIM is studied in a representative case of the residential building stock, which is located in three climate zones with different characteristics (warm, cold, and mild climates). The analyses were conducted both in current and future scenarios with the aim of knowing the advantages and limitations in each climate zone. The results show that the average consumption of the current, 2050, and 2080 scenarios decreased between 23% and 46% in warm climates, between 19% and 25% in mild climates, and between 10% and 29% in cold climates by using such a predictive method. It is also shown that this method is more resilient to climate change than the current standard. This research can be a starting point to understand users’ climate adaptation to predict energy consumption
Análisis comparativo de plataformas cloud con soporte orientado a servicios de internet de las cosas
Investigación TecnológicaSe realiza un estudio de la infraestructura requerida para implementar una solución
IoT; en base a este estudio se realizan dos implementaciones probando la
efectividad de dos de los proveedores cloud más usados para este tipo de
desarrollos, evaluando métricas y la experiencia obtenida para poder dar una guía
a personas que requieran implementar IoT.INTRODUCCIÓN
1. GENERALIDADES
2. ALICACION IOT
3. AMAZON VS AZURE
4. DISEÑO MANUALES DE LABORATORIO
5. CONCLUSIONES
6. RECOMENDACIONES
BIBLIOGRAFÍAPregradoIngeniero de Sistema
Semiclassical Concepts in Magnetoelectronics
Semiclassical theories of electron and spin transport in metallic magnetic
structures are reviewed with emphasis on the role of disorder and electronic
band structures in the current perpendicular to the interface plane (CPP)
transport configuration.Comment: Proceedings of the NEC Symposium on "Spin-related Quantum Transport
in Mesoscopic Systems", to be published in the Journal of Materials Science
and Engineering
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