Dressed tunneling approximation for electronic transport through molecular transistors

A theoretical approach for the non-equilibrium transport properties of nanoscale systems coupled to metallic electrodes with strong electron-phonon interactions is presented. It consists in a resummation of the dominant Feynman diagrams from the perturbative expansion in the coupling to the leads. We show that this scheme eliminates the main pathologies found in previous simple analytical approaches for the polaronic regime. The results for the spectral and transport properties are compared with those from several other approaches for a wide range of parameters. The method can be formulated in a simple way to obtain the full counting statistics. Results for the shot and thermal noise are presented.Comment: 11 pages, 11 figures. Accepted for publication in Physical Review

Efficient MIMO detection for high-order QAM constellations in time dispersive channels

In this paper, we apply a generalized form of the alternating direction method of multipliers (ADMM) and derive a multiple-input multiple-output (MIMO) detection algorithm for single carrier transmissions in time dispersive channels. The proposed algorithm supports different penalty parameters for each individual subcarrier and antenna and also includes a relaxation coefficient in the iterations. Besides evaluating the impact of these parameters, a method is presented for the automatic selection of the penalty. It is shown through simulations that very competitive performances can be obtained with the proposed approach for systems with high-order modulation combined with large antenna settings.info:eu-repo/semantics/acceptedVersio

Degradation characteristics of hydroxyapatite coatings on orthopedic TiAlV in simulated physiological media investigated by electrochemical impedance spectroscopy

This paper concentrates on the degradation characteristics of hydroxyapatite (HA) coatings on orthopaedic Ti-6Al-4V alloy while immersed in Ringer's salt solution, which were investigated by electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy measurements were used to in situ characterize the electrochemical behavior of the passivated alloy covered with HA during aging in Ringer's solution. Comparison of the electrochemical data for the coated material with that for the uncoated metal substrate was also performed. The characteristic feature that describes the electrochemical behavior of the coated material is the coexistence of large areas of the coating itself with pores where the substrate is exposed to the aggressive media. The interpretation of results was thus performed in terms of a two-layer model of the film, in which the precipitation of hydrated oxide or phosphate compounds seals the pores left by the ceramic coating. The blocking effect due to salt precipitation inside the pores produces an enhancement of the resistance values, thus effectively diminishing the metal ion release in the system.Collaborative Research Programme (Acción Integrada No. HP1995-0092 and HP1996-0109) between Spain and Portugal

Uma introdução às técnicas de avaliação multicritério para planejamento urbano, territorial e de transportes

Co-financiado por uma agência de fomento à pesquisa brasileira (CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) e outra portuguesa (ICCTI - Instituto de Cooperação Científica e Tecnológica Internacional de Portugal)Documento elaborado no âmbito do projeto de pesquisa intitulado "PLANEJAMENTO INTEGRADO: EM BUSCA DE DESENVOLVIMENTO SUSTENTÁVEL PARA CIDADES DE PEQUENO E MÉDIO PORTES", co-financiado por uma agência de fomento à pesquisa brasileira (CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) e outra portuguesa (ICCTI - Instituto de Cooperação Científica e Tecnológica Internacional de Portugal). A presente versão foi produzida para um curso no Brasil, ministrado pelo Professor Rui António Rodrigues Ramos no Departamento de Transportes da Escola de Engenharia de São Carlos da USP, tendo sido a sua organização e edição realizada por Antônio Nélson Rodrigues da Silva, Professor Associado desta Universidade e coordenador do projeto no Brasil junto à CAPES

Production of optical phase space vortices with non-locally distributed mode converters

Optical vortices have been observed in a wide variety of optical systems. They can be observed directly in the wavefront of optical beams, or in the correlations between pairs of entangled photons. We present a novel optical vortex which appears in a non-local plane of the two-photon phase space, composed of a single degree of freedom of each photon of an entangled pair. The preparation of this vortex can be viewed as a "non-local" or distributed mode converter. We show how these novel optical vortices of arbitrary order can be prepared in the spatial degrees of freedom of entangled photons.Comment: To appear in upcoming special issue "Orbital Angular Momentum" of the Journal of Optic

Performance bound for generalized M-QAM constellations in time-discrete multipath rayleigh fading channels with channel estimation errors

In this paper we derive a lower bound on the bit error rate (BER) for the individual bit streams that can be mapped simultaneously in an hierarchical way onto generalized multilevel quadrature amplitude modulations (M-QAM). The expressions are valid for time-discrete multipath Rayleigh fading environments with imperfect channel estimation and can be regarded as an extension of the well-known matched filter bound (MFB).info:eu-repo/semantics/acceptedVersio