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Glosse bibliografiche a una selezione di scritti di Luciano Berio
No full textQuesto paper © Copyright 2011 by Marco Uvietta è pubblicato con Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported. Maggiori informazioni circa la licenza all’URL: <http://creativecommons.org/licenses/by-nc-nd/3.0/
Automated Reasoning on TBoxes with Qualified Number Restrictions via SMT
No full textThe problem of reasoning with qualified number restrictions in Description Logics (DLs) has been investigated since the very first research steps in automated reasoning for DLs. Moreover, developing techniques for optimized reasoning with qualified number restrictions and has gained further importance since qualified number restrictions have been added to the forthcoming standard OWL 2 for Semantic Web applications. On the one hand, however, actual DL reasoning techniques, often lack of efficiency in handling those features, especially when the number of restrictions or the values involved are high. On the other hand the manifold problem of reasoning including numerical constraints is a well-established and thoroughly investigate problem in the SMT community, in which a lot of effort is continuously spent in order to enhance the efficiency of reasoning techniques for such kind of problems. In this paper we propose and investigate a novel approach for concept satisfiability in acyclic ALCQ ontologies. The idea is to encode an ALCQ ontology into a formula in Satisfiability Modulo the Theory of Costs (SMT(C)), which is a specific and computationally much cheaper subcase of Linear Arithmetic under the Integers (LA(Z)), and to exploit the power of modern SMT solvers to compute every concept-satisfiability query on a given ontology. We have implemented and tested our approach (called ALCQ2SMT_C) and some optimizations on a wide set of synthesized benchmark formulas, comparing the approach with the main state-of-the-art tools available. Our empirical evaluation confirms the potential of the approach
PSO-Based Real-Time Control of Planar Uniform Circular Arrays
No full textThis paper is aimed at assessing the effectiveness of the phase-only control strategy based on a customized PSO when applied to planar uniform circular arrays (PUCA) and in the presence of interferences both in the near-field and far-field of the antenna. The employed geometry seems to be suitable for a reliable and effective implementation of adaptive arrays in mobile devices thanks to its symmetry and geometric simplicity. For validation purposes, the proposed architecture is evaluated in the presence of a complex time-varying scenario both in terms of synthesized beam patterns and signal-to-interference-plusnoise ratio. (c) 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
Hybrid design of a fractal-shaped GSM/UMTS antenna
No full textIn this paper, the synthesis of a three-band planar antenna working in the GSM (900 and 1800 MHz) and UMTS frequency bands is presented. As reference geometry, a hybrid pre-fractal shape has been adopted by integrating a sierpinski-like and a Meander-like structure. The synthesis of the antenna has been performed by optimizing the descriptive geometrical parameters of the reference shape by means of a customized Particle Swarm strategy to comply with the electrical and geometrical requirements
Electromagnetic passive localization and tracking of moving targets in a WSN-infrastructured environment.
No full textIn this paper, an innovative strategy for the passive localization of transceiver-free objects is presented. The localization is yielded by processing the received signal strength data measured in an infrastructured environment. The problem is reformulated in terms of an inverse source one, where the probability map of the presence of an equivalent source modeling the moving target is looked for. Toward this end, a customized classification procedure based on a support vector machine is exploited. Selected, but representative, experimental results are reported to assess the feasibility of the proposed approach and to show the potentialities and applicability of this passive and unsupervised technique. “(c) Institute of Physics
Rectangular Thinned Array Design by McFarland Difference Sets
No full textThe problem of reducing the number of elements of large arrays is of great importance in satellite, remote sensing, radar and biomedical imaging applications in which the cost, weight, power consumption, mutual coupling effects, HW and SW complexity have to be as low as possible. Thinned arrays, however, are known to exhibit high peak sidelobe levels (PSL) if not suitably designed [1]. As a consequence, design techniques able to control and reduce the PSL of non‐regular arrays have been subject of research since their introduction [1]‐[5]
Antenna Array Synthesis Through Time Modulation
No full textIn the last years, there has been a renewed interest towards the use of time‐modulated arrays (TMAs) thanks to the simplicity in reconfiguring the average pattern of the antenna just modifying the on‐off sequence controlling a set of radio‐frequency (RF) switches. TMAs have been originally introduced for the generation of low and ultra‐low sidelobe patterns for radar arrays [1] thus avoiding the implementation of impracticable excitation tapering with high dynamic range ratios. However, they haven’t received a large diffusion because of the power losses due to the generation of harmonic radiation at multiples of the time‐modulation frequency. As a matter of fact, the periodic modulation of the static excitations causes a shift of the radiated power in the sideband radiation (SR) [2] with a consequent reduction of the directivity of the pattern at the carrier frequency
A SVM-Based Three-Dimensional Multi-Resolution Approach for Biomedical Inverse Scattering Problems
No full textIn the last few years, microwave imaging techniques have been successfully used to provide the spatial distribution of tissues. In particular, because of the significant contrast of the dielectric properties between the normal tissue and the malignant tissue at microwave frequencies, microwave methods seem to be very promising diagnosis methods for the early cancer detection [1]
Percolation-Based Approaches For Ray-Optical Propagation in Inhomogeneous Random Distribution of Discrete Scatterers
No full textWe address the problem of optical ray propagation in an inhomogeneous half�]plane lattice, where each cell can be occupied according to a known one�]dimensional obstacles density distribution. A monochromatic plane wave impinges on the random grid with a known angle and undergoes specular reflections on the occupied cells. We present two different approaches for evaluating the propagation depth inside the lattice. The former is based on the theory of the Martingale random processes, while in the latter ray propagation is modelled in terms of a Markov chain. A numerical validation assesses the proposed solutions, while validation through experimental data shows that the percolation model, in spite of its simplicity, can be applied to model real propagation problems
A Design Procedure for Sum and Difference Patterns by Means of Reactive Sorting Algorithm
No full textA new approach for the synthesis of both sum and difference antenna pattern is proposed. The approach allows to obtain an optimal sum pattern and a sub-optimal difference pattern through the search of a minimal cost path inside an incomplete binary tree