X-Type Interface for Management of Multidomain Multitechnology Networks

The specification and implementation of Xcoop interfaces has received great attention in the last few years. In fact, the appropriate design of this system component is a key aspect for efficient and seamless co-operative management. In this context it is worth mentioning the EURESCOM P408 project and the standards of the European Telecommunication Standards Institute (ETSI) in Europe and the ITU-T and Telemanagement Forum related work worldwide. The Xcoop specification presented in this paper, produced as part of the results of the project MISA co-funded by the Commission of the European Union, is a step ahead in the evolution of this system interface. Distinguished from preceding works, this one allows interactions between management systems independently to the underlying network technology, ATM, SDH or hybrid. This is achieved by defining appropriate functionality and an information model, indeed, where the specific characteristics of ATM and SDH resources are abstracted and merged in common classes.Peer ReviewedPostprint (published version

Interaction of oxygen with TiN (001): N↔O exchange and oxidation process

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O2 on TiN(001) was investigated at temperatures between 250 and 450K. At the lowest temperature, there was chemisorption of oxygen (O2,gas→2Oads) without significant surface oxidation. In contrast, at 450K the amount of O2 adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiOx species, and desorption of both N2 and NO was detected. The DFT calculations show that the adsorption/dissociation of O2 is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process (ΔE=2.84eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O2 and the formation of N2 or NO. Both experimental and theoretical results lead to conclude that a TiN+mO2→TiOx+NO reaction is an important exit channel for nitrogen in the oxidation process.Ministerio de Educación y Ciencia de España, MEC. MAT2005-01872Junta de Andalucía. FQM-132División de Ciencias Químicas del Departamento de Energía de EE. UU. DE-AC02-98CH10086Fundación japonesa para la Ciencia de los Materiale

A polynomial rooting approach for synchronization in multipath channels using antenna arrays

The estimation of the delay of a known training signal received by an antenna array in a multipath channel is addressed. The effect of the co-channel interference is taken into account by including a term with unknown spatial correlation. The channel is modeled as an unstructured FIR filter. The exact maximum likelihood (ML) solution for this problem is derived, but it does not have a simple dependence on the delay. An approximate estimator that is asymptotically equivalent to the exact one is presented. Using an appropriate reparameterization, it is shown that the delay estimate is obtained by rooting a low-order polynomial, which may be of interest in applications where fast feedforward synchronization is needed.Peer ReviewedPostprint (published version

Biological carbon dioxide utilisation in food waste anaerobic digesters

Carbon dioxide (CO2) enrichment of anaerobic digesters (AD) was previously identified as a potential on-site carbon revalorisation strategy. This study addresses the lack of studies investigating this concept in up-scaled units and the need to understand the mechanisms of exogenous CO2 utilisation. Two pilot-scale ADs treating food waste were monitored for 225 days, with the test unit being periodically injected with CO2 using a bubble column. The test AD maintained a CH4 production rate of 0.56 ± 0.13 m3 CH4·(kg VSfed d)−1 and a CH4 concentration in biogas of 68% even when dissolved CO2 levels were increased by a 3 fold over the control unit. An additional uptake of 0.55 kg of exogenous CO2 was achieved in the test AD during the trial period. A 2.5 fold increase in hydrogen (H2) concentration was observed and attributed to CO2 dissolution and to an alteration of the acidogenesis and acetogenesis pathways. A hypothesis for conversion of exogenous CO2 has been proposed, which requires validation by microbial community analysis