130,781 research outputs found
On the thermodynamics of Godel black holes
No full textAfter a brief review of Gbdel-type universes in string theory, we discuss some intriguing properties of black holes immersed in such backgrounds. Among these are the upper bound on the entropy that points towards a finite-dimensional Hilbert space of a holographically dual theory, and the minimum black hole temperature that is reminiscent of the Hawking-Page transition. Furthermore, we discuss several difficulties that are encountered when one tries to formulate a consistent thermodynamics of Godel black holes, and point out how they may be circumvented
-dimensional black hole background
No full textThe behavior of a quantum scalar field is studied in the metric ground state of the (2+1)-dimensional black hole of Ba~nados, Teitelboim and Zanelli which contains a naked singularity. The one-loop BTZ partition function and the associate black hole effective entropy, the expectation value of the quantum fluctuation as well as the renormalized expectation value of the stress tensor are explicitly computed in the framework of the -function procedure. This is done for all values of the coupling with the curvature, the mass of the field and the temperature of the quantum state. In the massless conformally coupled case, the found stress tensor is used for determining the quantum back reaction on the metric due to the scalar field in the quantum vacuum state, by solving the semiclassical Einstein equations. It is finally argued that, within the framework of the 1/N expansion, the Cosmic Censorship Hypothesis is implemented since the naked singularity of the ground state metric is shielded by an event horizon created by the back reaction
Context-aware spoken language understanding for human robot interaction
No full textL’interpretazione di comandi
espressi nei confronti di piattaforme
robotiche e un processo strettamente `
legato al contesto operativo in cui avviene
l’interazione. In questo lavoro, presentiamo
LU4R - adaptive spoken Language
Understanding 4 Robots, un sistema per
l’elaborazione automatica di comandi vocali,
dipendente dall’ambiente in cui il comando
viene espresso. Il sistema proposto,
implementato come una cascata
di passi di elaborazione semantica, e`
stato progettato seguendo un’architettura
Client/Server, per ridurre i requisiti di integrazione
con le piattaforme robotiche esistenti.Robots operate in specific environments and the correct interpretation of linguistic interactions depends on physical, cognitive and language-dependent aspects triggered by the environment. In this work, we present LU4R - adaptive spoken Language Understanding 4 Robots, a Spoken Language Understanding chain for the semantic interpretation of robotic commands, that is sensitive to the operational environment. The system has been designed according to a Client/Server architecture in order to be easily integrated with the vast plethora of robotic platforms
Central Charges and Boundary Fields for two Dimensional Dilatonic Black Holes
No full textIn this paper we first show that within the Hamiltonian description of general relativity, the central charge of a near horizon asymptotic symmetry group is zero, and therefore that the entropy of the system cannot be estimated using Cardy’s formula. This is done by mapping a static black hole to a two dimensional space. We explain how such a charge can only appear to a static observer who chooses to stay permanently outside the black hole. Then an alternative argument is given for the presence of a universal central charge. Finally we suggest an effective quantum theory on the horizon that is compatible with the thermodynamics behaviour of the black hole
Experimental Philosophy and Early Moden Ethics: Turnbull and Fordyce
No full textAlberto Vanzo writes... Experimental philosophy is often portrayed as an exciting or controversial new development in philosophy. Yet, some have claimed that the practice of experimental philosophy is traditional and that it ‘began to flourish’ in the early modern period. Is it true that the practices and methods of current-day experimental philosophy are traditional philosophical practices? To shed light on this question, I will focus on George Turnbull, David Fordyce and (in my next post) D..
Nitrocarburising of annealed and severe plastically deformed 16MnCr5 steel
No full textThe microstructure resulting from a gaseous multistage nitrocarburising treatment applied to a 16MnCr5 steel has been investigated to study the microstructural evolution during the process and the effects of severe plastic deformation. The depth of the compound layer and the porous zone has been measured by optical microscopy. The microstructure has been investigated by means of a scanning electron microscope equipped with both an electron backscatter diffraction detector, to assess the amount and the distribution of nitrogen nitrides, and an energy-dispersive X-ray microanalysis to reveal the N diffusion depth. Finally, microhardness investigations have been carried out. The results indicate that severe plastic deformation influences the microstructure of the compound layer, the N concentration trends and the hardness profiles. The effects of severe plastic deformation lead to a greater initial diffusivity of nitrogen, a subsequent premature N saturation in the diffusion zone and an increased porous/compact-layer thickness ratio
Grounded Language Interpretation of Robotic Commands through Structured Learning
No full textThe presence of robots in everyday life is increasing day by day at a growing pace. Industrial and working environments, health-care assistance in public or domestic areas can benefit from robots' services to accomplish manifold tasks that are difficult and annoying for humans. In such scenarios, Natural Language interactions, enabling collaboration and robot control, are meant to be situated, in the sense that both the user and the robot access and make reference to the environment. Contextual knowledge may thus play a key role in solving inherent ambiguities of grounded language as, for example, the prepositional phrase attachment. In this work, we present a linguistic pipeline for semantic processing of robotic commands, that combines discriminative structured learning, distributional semantics and contextual evidence extracted from the working environment. The final goal is to make the interpretation process of linguistic exchanges depending on physical, cognitive and language-dependent aspects. We present, formalize and discuss an adaptive Spoken Language Understanding chain for robotic commands, that explicitly depends on the operational context during both the learning and processing stages. The resulting framework allows to model heterogeneous information concerning the environment (e.g., positional information about the objects and their properties) and to inject it in the learning process. Empirical results demonstrate a significant contribution of such additional dimensions, achieving up to a 25% of relative error reduction with respect to a pipeline that only exploits linguistic evidence
Dielectric properties of crystalline organic molecular films in the limit of zero overlap
No full textWe present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided
A discriminative approach to grounded spoken language understanding in interactive robotics
No full textSpoken Language Understanding in Interactive Robotics provides computational models of human-machine communication based on the vocal input. However, robots operate in specific environments and the correct interpretation of the spoken sentences depends on the physical, cognitive and linguistic aspects triggered by the operational environment. Grounded language processing should exploit both the physical constraints of the context as well as knowledge assumptions of the robot. These include the subjective perception of the environment that explicitly affects linguistic reasoning. In this work, a standard linguistic pipeline for semantic parsing is extended toward a form of perceptually informed natural language processing that combines discriminative learning and distributional semantics. Empirical results achieve up to a 40% of relative error reduction
A context-based model for sentiment analysis in twitter
No full textMost of the recent literature on Sentiment Analysis over Twitter is tied to the idea that the sentiment is a function of an incoming tweet. However, tweets are filtered through streams of posts, so that a wider context, e.g. A topic, is always available. In this work, the contribution of this contextual information is investigated. We modeled the polarity detection problem as a sequential classification task over streams of tweets. A Markovian formulation of the Support Vector Machine discriminative model as embodied by the SVMhmm algorithm has been here employed to assign the sentiment polarity to entire sequences. The experimental evaluation proves that sequential tagging effectively embodies evidence about the contexts and is able to reach a relative increment in detection accuracy of around 20% in F1 measure. These results are particularly interesting as the approach is flexible and does not require manually coded resources
- …
