89,551 research outputs found
First-principles study of vacancy formation and migration energies in tantalum
No full textThe vacancy formation and migration enthalpies H-f and H-m in tantalum are calculated by means of ab initio pseudopotential techniques. The results obtained after relaxation with supercells containing 54 atomic sites (H-f = 3.0 eV and H-m = 0.8 eV) are in excellent agreement with experiments (H-f = 3.1 eV and H-m = 0.7 eV). The electronic entropy has a moderate influence on their temperature dependence. The effects of structural relaxation, which reduce H-f by 14%, are significantly larger than for group-VI elements and are typical of a normal behavior for the bcc structure. The experimental tracer self-diffusion coefficient is well reproduced within the rate theory using an estimate of the vibrational formation entropy and the attempt frequency. [S0163-1829(99)12133-7]
Note sulla separazione della rete di Telecom Italia
No full textLo scritto affronta in chiave interdisciplinare il novero di problemi giuridici posti dalla separazione della rete di Telecom Itali
Prefix probabilities for linear context-free rewriting systems
No full textWe present a novel method for the computation of prefix probabilities for linear context-free rewriting systems. Our approach streamlines previous procedures to compute prefix probabilities for context-free grammars, synchronous context-free grammars and tree adjoining grammars. In addition, the methodology is general enough to be used for a wider range of problems involving, for example, several prefixes
Unveiling co-operative networks and ‘hidden families’ in the container port industry
No full textOver the last few years, the progressive scarcity of land for greenfield projects in ports and the enormous financial resources required to realize new terminal facilities have induced international terminal operators (ITOs) to enter in various types of agreements. In particular, ITOs have growingly resorted to equity joint-ventures (EJVs) to develop new infrastructures and share project risks.
This manuscript introduces a multi-layer conceptual framework and investigates the extent of EJVs through a network analysis of inter-firm communities across various nations. The study has been performed on a data set that includes all port facilities operated in 2010 by ITOs. Indeed, 427 terminal facilities and 250 container port operators, that is 40 ITOs and 210 local firms, have been examined. Results show the different co-operative attitudes of ITOs and demonstrate that firms co-operate in a selective way, disclosing emerging patterns and hidden networks of relationships
Letture di Gramsci nell'antropologia italiana del dopoguerra
No full textIl saggio analizza la diversa ricezione delle Osservazioni sul folclore di Gramsci nel dibattito che si svolge a Roma, presso il Teatro delle arti, all'inizio di Giugno del 1951. Al dibattito, organizzato dall'Istituto Gramsci, partecipano Paolo Toschi, Vittorio Santoli, Ernesto De Martino. L'analisi si concentra in particolare sulla distanza tra la lettura disciplinare di Toschi, che respinge in toto le osservazioni di Gramsci, riducendone la portata teorica, e quella molto politica di De Martino, piuttosto in linea con l'approccio pedagogico e "anti-populista" del PCI dell'epoca, nonostante le sue precedenti prese di posizione riguardo alla possibilità di individuare un nucleo progressivo del folclore. Il giovane CIrese, presente alla giornata di studio, avrebbe in seguito dato una lettura disciplinare rovesciata rispetto a quella di Toschi, facendo di Gramsci il fondatore della demologia
Computation of distances for regular and context-free probabilistic languages
No full textSeveral mathematical distances between probabilistic languages have been investigated in the literature, motivated by applications in language modeling, computational biology, syntactic pattern matching and machine learning. In most cases, only pairs of probabilistic regular languages were considered. In this paper we extend the previous results to pairs of languages generated by a probabilistic context-free grammar and a probabilistic finite automaton.Peer reviewe
Computing partition functions of PCFGs
No full textAcknowledgement provided in erratum at DOI:10.1007/s11168-009-9062-1We investigate the problem of computing the partition function of a probabilistic context-free grammar, and consider a number of applicable methods. Particular attention is devoted to PCFGs that result from the intersection of another PCFG and a finite automaton. We report experiments involving the Wall Street Journal corpus.Peer reviewe
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