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Real-Time Tracking of Transceiver-Free Objects for Homeland Security
No full textThe increasing demand in homeland security speeds up the development of innovative and non‐invasive systems to localize and track moving objects in complex environments. In this paper the real‐time localization of transceiver‐free targets is addressed by means of learning by example methodology that exploits the received signal strength indicator available at the nodes of a wireless sensor network as input data. This approach uses neither dedicated sensors nor active devices put on the target to localize both idle and moving objects. The definition of a customized classifier during an offline training procedure enables the real‐time generation of a probability map of presence by processing the output of the support vector machine. Some selected experimental results validate the effectiveness of the proposed methodology applied in real scenarios
Evolutionary Techniques For Inverse Scattering: Current Trends and Envisaged Developments
No full textThe possibility of sensing a given region from the measurements of the scattered field when it is illuminated through low‐power microwave electromagnetic waves is still a topic of great interest due to the wide range of applications in many different areas of medical, industrial, and civil engineering. For instance, let us consider problems related to biomedical engineering, non‐invasive thermometry, non‐destructive testing and evaluation, geophysical analysis, remote sensing, and archeology. Although this list is certainly non‐exhaustive, it is sufficient to justify the great attention devoted to the solution of inverse scattering problems both from a theoretical and algorithmic point of view, as demonstrated by the large amount of papers and books available in the scientific literature. The issues that actually limit the proliferation of practical imaging systems are the intrinsic theoretical difficulties (i.e., ill‐posedness and non‐linearity), which characterize an inverse scattering problem. The ill‐posedness can be avoided by using additional (a‐priori) information directly taken from the physics of the problem at hand. This strategy allows one to avoid the reconstruction of artifacts and obtain the so‐called regularized solutions. Concerning the non‐linearity of the inverse scattering model, it must be considered to take into account the multiple‐scattering effects, since linear approximations (e.g., Born‐like approaches) can be rarely applied to real objects. Accordingly, many non‐linear inversion techniques have been proposed for the optimization of a suitable cost function taking into account the mismatch between the measured data and the reconstructed ones. Originally, various deterministic approaches based on steepest‐descent algorithms [e.g., conjugate‐gradients (CG)] were proposed [1]. Although they have shown to provide successful results, they suffer the presence of local minima when initial solution does not belong to the “attraction basin” of the global optimum
Computationally-Effective Optimal Excitation Matching for the Synthesis of Large Monopulse Arrays
No full textAntenna arrays able to generate two different patterns are widely used in tracking radar systems [1]. Optimal (in the Dolph�]Chebyshev sense) sum [2] and difference patterns [3] can be generated by using two independent feed networks. Unfortunately, such a situation generally turns out to be impracticable because of its costs, the occupied physical space, the circuit complexity, and electromagnetic interferences. Thus, starting from the optimal sum pattern a sub�]optimal solution for the difference pattern is usually synthesized by means of the sub�]array technique. The array elements are grouped in sub�]arrays properly weighted for matching the constrains of the difference beam. Finding the best elements grouping and the sub�]array weights is a complex and challenging research topic, especially when dealing with large arrays. As far as linear arrays are concerned, McNamara proposed in [4] an analytical method for determining the �gbest compromise�h difference pattern. Unfortunately, when the ratio between the elements of the array and sub�]arrays increases, such a technique exhibits several limitations mainly due to the ill�]conditioning of the problem and the computational costs due to exhaustive evaluations. A non�]negligible saving might be achieved by applying optimization algorithms (see for instance [5] and [6]) aimed at minimizing a suitable cost function. Notwithstanding, optimization�]based approaches still appear computationally expensive when dealing with large arrays because of wide dimension of solution space to be sampled. In order to properly deal with these computational issues, this contribution presents an innovative approach based on an optimal excitation matching procedure. By exploiting the relationship between independently�]optimal sum and difference patterns, the dimension of the solution space is considerably reduced and efficiently sampled by taking into account the presence of array elements more suitable to change sub�]array membership. In the following, the proposed technique is described pointing out, through a representative case, its potentialities and effectiveness in dealing with large arrays. This is the author's version of the final version available at IEEE
A SVM-Based Multi-Resolution Procedure for the Estimation of the DOAS of Interfering Signals in a Communication System
No full textIn this work, the use of a planar antenna system for the estimation of the directions of arrivals (DOAs) of multiple signals impinging on the receiver has been considered. Towards this end, an efficient multi-resolution method based on a SVM-classifier is proposed for determining a probabilitic map of the DOAs of the unknown interfering signals. Numerical results dealing with multiple interferers scenarios in noisy environments are provided in order to assess the feasibility as well as the capability of the proposed approach
Beam Pattern Optimization in Time-Modulated Linear Arrays
No full textTime‐modulated arrays exploit time as an additional degree of freedom [1] where a set of radio‐frequency (RF) switches are used to modulate the static excitations to arbitrarily shape the radiation pattern. Firstly, time‐modulation has been considered for the synthesis of radar array to obtain low and ultra‐low sidelobe patterns [2]. Unfortunately, the periodic on‐off of the RF switches causes the generations of undesired radiations, the so‐called sideband radiation (SR) [3], which represents a loss of the radiated power. Such a drawback has limited the use of time‐modulated array in real world applications. This is the author's version of the final version available at IEEE
Existence and Stability of Square-Mean almost periodic Solutions to a Spatially Extended Neural Network with Impulsive Noise
No full textOur work is concerned with a neural network with n nodes, where the activity of the k-th cell depends on external, stochastic inputs as well as the coupling generated by the activity of the adjacent cells, transmitted through a diusion process in the network. This paper aims to throw some light on time-varying, stochastically perturbed, neuronal networks. We show that when the coecients oscillate around a reference value, with ascillations that are almost periodic and suitably small in percentage, then there exists a unique solution for the system, that is almost periodic and uniformly bounded in the mean square norm for all times
Lifelog Event Management: Crowd Research Case Study
No full textLifelog research involves complex event analysis that requires the efforts of many advanced experts in different disciplines. It also handles privacy and/or copyrighted materials where mutual consent on the use of data is very important. Thus we propose a secure Web-based lifelog database service to help researchers concentrate efforts to solve difficult research issues. This paper details many aspects of lifelog research topics and technical challenges that the author has experienced over one year case study. It also describes economical and efficient methods to implement the back-end system and services for real lifelog event management. © ACM, 2011. This is the author’s version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in the ACM Multimedia 2011: Joint ACM Workshop on Modeling on Events in Multimedia (EiMM11)
L'Auctoritas plautina nelle 'Derivationes' di Osberno di Gloucester
No full textAfter the overview of the inherent status quaestionis, the essay offers a statistical-quantitative analysis of Plautus’ quotations in Osbernus of Gloucester’s Derivationes, with a view to a later critical-textual exam. Particularly, on the base of the frequency and the dislocation of the single quotations, it may be confirmed the hypothesis that Osbernus read directly Plautus’ first eight comedies, probably in a manuscript of the Palatini subfamily, to which also the codex J belongs
La responsabilità per linking a files audiovisivi contraffatti e l'incerta natura del motore di ricerca Nota a ord. Trib. Roma 22 marzo 2011)
Get PDFCon l'ordinanza qui in commento, il Tribunale di Roma prova a porre le basi per sancire la responsabilità del gestore del motore di ricerca che, in risposta alle ricerche degli utenti, fornisca link a copie non autorizzate di file audiovisivi. Nell'applicare la disciplina degli artt. 14-16 D.Lgs. n. 70/2003, tuttavia, non mancano notevoli incertezze circa la qualificazione del motore di ricerca quale hosting o caching provider
Determination of the complex permittivity values of planar dielectric substrates by means of a multifrequency PSO-based technique
No full textIn this paper, an innovative technique for the determination of the dielectric properties of planar substrates is presented. Starting from a set of impedance measurements performed on a section of a microstrip transmission line built on the planar dielectric substrate under test, the proposed technique formulates the reconstruction problem in terms of an optimization one successively solved by means of an effective stochastic algorithm. Such a method allows one the reconstruction of the permittivity values at multiple frequencies by simply using a vector network analyzer and a standard calibration procedure for the impedance measurement. The results of some representative experimental tests are shown for a preliminary assessment of the effectiveness of the proposed approach. (c) The Electromagnetics Academy - The final version of this article is available at the url of the journal PIER M: http://www.jpier.org/PIERM/pier.php?paper=0911290