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Analysis of Perturbed Fractals for Antenna Synthesis
No full textIn the last years there has been an increasing demand for compact and multi‐service systems driven by the great expansion of telecommunications sectors such as mobile telephony or personal communications. The development of these systems involves the synthesis of innovative antennas characterized by small dimensions and able to manage simultaneously different communication standards [1]. In this framework, fractal‐shaped antennas are promising solutions thanks to their properties. Among them, the self‐similarity property and the possibility to shrink an infinite‐length curve in a finite area make fractal geometries excellent candidates for both multi‐band [2][3] and miniaturization [4] purposes. However, standard fractal‐shaped antennas, as the Koch monopole [5], usually present an harmonic behavior rather than a real multi‐band behavior. Possible solutions to such a limitation are based on the perturbation of the fractal shape [6][7] in order to increase the degrees of freedom during the synthesis process for better tuning and controlling the working frequencies of the arising structure
Improving the Reconstruction Accuracy of Gas-Based NDE/NDT Methods Through a Level Set Approach
No full textIn the framework of nondestructive testing and evaluation (NDE/NDT), this paper deals with the problem of the detection of unknown anomalies in dielectric materials. The proposed inverse scattering approach consists of a two�]step procedure aimed at firstly estimating the region�]of�]interest where the defect is supposed to be located and then improving the qualitative imaging (i.e., the shape and position) of the crack. In order to assess the effectiveness of the proposed approach, an illustrative result from representative numerical test cases is presented and discussed
Detection of Multiple Defects in Industrial Products by Means of a Non-Destructive Microwave Approach
No full textThis paper proposes an approach for the detection of multiple defects inside a known host medium. Two innovative GA-based techniques are developed by using different strategies for the minimization of a suitably defined cost function. The first implementation is based on a set of parallel GA-based optimization sub-processes, whereas the other consists of a single process based on a variable length coding of the GA chromosomes. A set of representative test cases is analyzed for assessing potentialities and current limitations of the proposed strategy
A Percolation Model for the Wave Propagation in Non-Uniform Random Media
No full textThe statistical characterization of the electromagnetic propagation in urban radio channels is investigated. Towards this end, the propagation medium is modeled with a semi-infinite percolating lattice of lossless scatterers whose density varies in space according to a known one-dimensional distribution. The scenario is illuminated by a monochromatic plane wave that propagates according to the geometrical optics laws. By applying the random processes’ theory, a closed form analytical formula is provided, which allows a statistical estimation of the penetration capability of the electromagnetic wave into the medium. The analytical result has been validated through an exhaustive numerical assessment that demonstrates the effectiveness of the proposed model for a wide range of incidence conditions and scatterers’ density distribution
An integrated stochastic multi-scaling strategy for microwave imaging applications
No full textThis work presents an improved Multi-Scale algorithm for microwave imaging of two-dimensional scatterers. The proposed methodology includes a feedback between high- and low-resolution reconstructions in order to correlate the iterative reconstruction steps. Towards this end, the appealing features of a Particle Swarm-based algorithm are fully exploited. Such an integration is aimed at better matching a suitable representation of the unknowns with the global optimization properties of the stochastic optimizer to allow faithful reconstructions
La dimensione religiosa: problemi di metodo
No full textLa sociologia delle religioni presenta, come poche altre, dei problemi notevoli sul piano della ricerca. La stessa posizione della dimensione religiosa nel contesto della società moderna apre due fronti di problemi sia per il soggetto credente, sia per il ricercatore che si definisce a partire dalla sua stessa esteriorità rispetto al proprio oggetto. Al soggetto credente, proprio a partire dal momento in cui la dimensione religiosa è privata e interiore, l’osservazione del sociologo come quella dell’etnologo appaiono inevitabilmente intrusive e implicitamente provocatorie. Al ricercatore invece, ogni singola manifestazione dell’agire religioso – sia sul piano delle pratiche, sia su quello delle credenze che le attivano – appare rilevante solo per le conseguenze che provoca più che per le verità che dichiara di veicolare. Riuscire a fare ricerca in un tale contesto diventa problematico, ma ciò spiega anche l’interesse di questo working papers nel quale diversi giovani ricercatori, ciascuno con un proprio specifico percorso di ricerca, hanno affrontato e risolto i problemi metodologici connessi agli specifici oggetti di indagine che, di volta in volta, sono emersi nel corso del loro lavoro. Obiettivo del presente testo è pertanto quello di alimentare la riflessione sui problemi connessi all’analisi dei fenomeni religiosi e riguarda sia quanti operano in questo settore, sia quanti sono comunque interessati ai problemi metodologici che questa disciplina deve affrontare
Politics, Identity, Territory. The "Strength" and "Value" of Nation-State, the Weakness of Regional Challenge
No full textThe post Cold War age reveals itself as being characterized mostly by the flourishing of “identity politics”. Identitary issues affect the public dimension of collective life and they often develop into economic, legal, political terms. There are many types of collective identity. We would clarify some of them in order to focus the analytical tools that are necessary to face the phenomena we are interested with: national and regional identities. Crucial in our argument are the concept of “political identity” and its “territorial” dimension. This concept and this dimension consent to compare Nation-State and (sub-national) region as space of collective life, and their “authoritative” degree. According to this subject this essay will treat the following points: the return of identity politics nowadays (section 1); the concept of collective identity (section 2); the many faces of collective identity (section 3); the relationship among politics, territory and identity, analyzed through the paradigmatic case of Nation-state and national identity (section 4); the structuring of political space between centre and peripheries, where we consider how the dominance of Nation-State model has to face persisting of territorial cleavages (section 5); the case of the regional issue (section 6); the “strength” and the “value” of Nation-State (sections 7 and 8)
The Regulatory Anticommons of Green Infrastructures
No full textDevelopment of green infrastructures (renewable energy plants and transmission networks) is urgently needed if significant reductions of greenhouse emissions are to be accomplished in the next few decades. But the huge financial investments required by these infrastructures will not be undertaken without a well-designed regulatory framework. This paper argues that barriers to the implementation of such a framework can best be understood by drawing analogies to the Law and Economics literature on anticommons. This analytic framework is employed to assess and criticize EU and US proposals to regulate planning and siting of green infrastructures. Questo paper © Copyright 2011 by Giuseppe Bellantuono è pubblicato con Creative Commons Attribuzione-Non commerciale-Non opere derivate 2.5 Italia License. Maggiori informazioni circa la licenza all’URL: <http://creativecommons.org/licenses/by-nc-nd/2.5/it/
Immagini e metafore della società in età moderna
No full textImmagini e metafore della società nel loro insieme ci permettono di cogliere le modalità con le quali una società legge se stessa e si autodefinisce. Esse non necessariamente corrispondono pienamente ad una realtà, ma descrivendola o suggerendo un paragone per essa contribuiscono a costruirla o a consolidarla. Il testo descrive tre immagini con le quali la società è stata descritta e raffigurata tra medioevo ed età moderna. Nella prima essa è immaginata come un corpo, il cui capo è il sovrano e le cui membra sono i sudditi; in quella tripartita si suppone che esistano fra gli uomini tre grandi categorie funzionali e tre soltanto, quelli che pregano, quelli che combattono e quelli che lavorano; l’ultima infine vede la società come una piazza, al cui centro passeggiano governanti e uomini illustri, e nei cui angoli bui si rifugiano le professioni infamanti o le condizioni socialmente incerte. Ognuna di queste tre immagini ha contribuito a costruire aspetti della vita sociale e politica dei paesi in cui sono radicate. Il legame fra immagine sociale e realtà storica specifica mostra dunque anche la stretta connessione fra le diverse scienze sociali, la sociologia, l’antropologia, la politologia e la storia
Dual-Band Spline-Shaped PCB Antenna for Wi-Fi Applications
No full textIn this letter, a dual-band PCB antenna suitable for Wi-Fi applications is described. The antenna geometry is modeled by means of a spline curve and a partial metallic ground plane. The proposed antenna is suitable for Wi-Fi bands and it guarantees good impedance matching conditions at the working frequencies centered at 2.448GHz and 5.512GHz, respectively. A prototype of the synthesized antenna, built on an Arlon substrate, is analyzed to assess the effectiveness of the proposed antenna model in terms of VSWR values as well as radiation patterns. (c) 2009 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