Macroscopic thermal entanglement due to radiation pressure

Can entanglement and the quantum behavior in physical systems survive at arbitrary high temperatures? In this Letter we show that this is the case for a electromagnetic field mode in an optical cavity with a movable mirror in a thermal state. We also identify two different dynamical regimes of generation of entanglement separated by a critical coupling strength.Comment: Accepted in Phys. Rev. Let

Inovação em betões: nova normalização e produção de betões especiais

Universidade do Minho (UM).Parque de Exposições de Braga (PEB)

Technological evolution of concrete : from ancient times to ultra high performance concrete

Since the fall of the Roman Empire, concrete only suffered significant advances with the discovery of portland cement. The technological knowledge that the Romans held was empirical, based on the principle of trial and error, and allowed the discovery of new materials which properties could be reproduced but not explained. The ability to go beyond empiricism was only acquired by the scientific development that occurred mainly from the twentieth century onwards. In fact, no other binder materials were used other than those used by the Romans by the beginning of the nineteenth century. Only in the late eighteenth century was there a concrete renaissance. Nowadays, we can produce high-performance concrete with relative ease, maintaining the versatility of conventional concrete with the durability and strength of natural stone. However, it can be easily shaped, armed, hard-working pre and post tensioned with cables and mixed with different kind of fibers. In this paper, an overview of the use of concrete from ancient times to the most sophisticated ultra-high performance concrete in use is presented

Microscopic linear response theory of spin relaxation and relativistic transport phenomena in graphene

We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin relaxation processes and associated charge-to-spin interconversion phenomena in response to generic external perturbations, including spin density fluctuations and electric fields. A controlled diagrammatic evaluation of the generalized spin susceptibility in the diffusive regime of weak spin-orbit interaction allows us to show that the spin and momentum lifetimes satisfy the standard Dyakonov-Perel relation for both weak (Gaussian) and resonant (unitary) nonmagnetic disorder. Finally, we demonstrate that the spin relaxation rate can be derived in the zero-frequency limit by exploiting the SU(2) covariant conservation laws for the spin observables. Our results set the stage for a fully quantum-mechanical description of spin relaxation in both pristine graphene samples with weak spin-orbit fields and in graphene heterostructures with enhanced spin-orbital effects currently attracting much attention

Factores climáticos no consumo de energia eléctrica: um caso com utilização de data mining.

4ª Conferência Ibérica de Sistemas e Tecnologias de Informação, 17 a 20 de Junho de 2009, Póvoa de Varzim.Este trabalho tem por objectivo identificar causas responsáveis por variações no consumo horário de energia com base na identificação de padrões e relações entre os dados de consumo e várias variáveis climatéricas. Para tal utilizam-se técnicas de data mining, nomeadamente a metodologia CRISP-DM e software de data warehouse MS SQL Server. Assim, foi possível verificar que as variáveis climatológicas têm influência muito significativa na produção de energia eléctrica, tendo sido possível prever os consumos de 2007 com um erro absoluto médio de 1,4 MW. Identificam-se ainda vários padrões no comportamento do consumo ou produção de energia eléctrica, nem todos espectáveis face ao conhecimento actual de domínio

Emergencies in a Territory of Mobility

UID/SOC/04647/2013The Mediterranean Sea is a historical stage of mobilities and has been a witness to important movements of people and goods since ancient times. In this liquid territory, different social processes of globalization can be observed; yet, in recent years, it has been predominantly depicted as an emergency scene, a crossing platform for those in search of refuge in Europe. This scenario becomes connected to a set of dimensions of securitization and quests for control that redirect the debates about national and European responsibilities regarding maritime territories. In this article, this issue is addressed exploring the construction and development of the social problem of refugees in the Mediterranean, departing from a frame analysis of news items thematically filtered from the digital platforms of two Italian newspapers in 2013-2015. The problem is contextualized in time and content progression, deepening the framing of some critical events, and reframing the Mediterranean as a referent/emergent territory of mobility.publishersversionpublishe

Theory of spin–charge-coupled transport in proximitized graphene: an SO(5) algebraic approach

Establishing the conditions under which orbital, spin and lattice-pseudospin degrees of freedom are mutually coupled in realistic nonequilibrium conditions is a major goal in the emergent field of graphene spintronics. Here, we use linear-response theory to obtain a unified microscopic description of spin dynamics and coupled spin–charge transport in graphene with an interface-induced Bychkov–Rashba effect. Our method makes use of an SO(5) extension of the familiar inverse-diffuson approach to obtain a quantum kinetic equation for the single-particle density matrix that treats spin and pseudospin on equal footing and is valid for arbitrary external perturbations. As an application of the formalism, we derive a complete set of drift–diffusion equations for proximitized graphene with scalar impurities in the presence of electric and spin-injection fields which vary slowly in space and time. Our approach is amenable to a wide variety of generalizations, including the study of coupled spin–charge dynamics in layered materials with strong spin–valley coupling and spin–orbit torques in van der Waals heterostructures

A new multi-criteria approach for sustainable material selection problem

Sustainable material selection is a crucial problem given the new demands of society and novel production strategies that consider the concepts of sustainability. Multi-criteria decision-making methods have been extensively used to help decision-makers select alternatives in different fields of knowledge. Nonetheless, these methods have been criticized due to the rank reversal problem, where the independence of the irrelevant alternative principle is violated after the initial decision problem is changed. Over the course of this study, we observed that the solutions that are proposed for this problem, in the context of sustainable material selection, are insufficient. Thus, we present a new material selection approach that is based on the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, which is immune to rank reversal. We also demonstrate the causes of rank reversal in the TOPSIS method, how the R-TOPSIS method was designed to solve them, and how it can be applied to sustainable material selection

Suporte à Decisão em Tecnologias de Comunicação : um caso com utilização de metodologias OLAP e Data Mining

Este artigo descreve um Sistema de Apoio à Decisão capaz de fornecer informação precisa e de qualidade sobre as comunicações na Electricidade Dos Açores (EDA). A decisão imediata a apoiar consistia em saber se as comunicações entre ilhas deveriam passar para tecnologias Voice over IP (VoIP), um serviço actualmente contratado a uma empresa de comunicações externa. Num projecto de business intelligence e usando tecnologias Microsoft SQL Server, o sistema lê e pré-processa ficheiros CSV de grande dimensão, recebidas da empresa de comunicações, combina esses dados com bases de dados existentes e apresenta os resultados sobre a forma de cubos multidimensionais. Posteriormente, este trabalho foi integrado num projecto de data minig, usando a metodologia CRISP-DM, tendo sido possível além de apoiar a decisão pretendida identificar situações ineficientes e mesmo de utilização fraudulenta de equipamentos de comunicação. Vários modelos foram construídos e disponibilizados a diferentes decisores para apoiar decisões estratégicas e de controlo.info:eu-repo/semantics/publishedVersio

Magnetic Oscillation of Optical Phonon in ABA- and ABC-Stacked Trilayer Graphene

We present a comparative measurement of the G-peak oscillations of phonon frequency, Raman intensity and linewidth in the Magneto-Raman scattering of optical E2g phonons in mechanically exfoliated ABA- and ABC-stacked trilayer graphene (TLG). Whereas in ABA-stacked TLG, we observe magnetophonon oscillations consistent with single-bilayer chiral band doublets, the features are flat for ABC-stacked TLG up to magnetic fields of 9 T. This suppression can be attributed to the enhancement of band chirality that compactifies the spectrum of Landau levels and modifies the magnetophonon resonance properties. The drastically different coupling behaviour between the electronic excitations and the E2g phonons in ABA- and ABC-stacked TLG reflects their different electronic band structures and the electronic Landau level transitions and thus can be another way to determine the stacking orders and to probe the stacking-order-dependent electronic structures. In addition, the sensitivity of the magneto-Raman scattering to the particular stacking order in few layers graphene highlights the important role of interlayer coupling in modifying the optical response properties in van der Waals layered materials.Comment: 25 pages, 6 figure