Fare geografia con un video. L’esperienza del documentario “Cos’è geopolitica”

Tra ottobre e dicembre 2017 il prof. Edoardo Boria è stato animatore di un ciclo di seminari organizzati presso la Società Geografica Italiana dal titolo Nuovi orizzonti del pensiero geografico: la geopolitica oggi. Occasione di questi incontri è stata la realizzazione del documentario “Cos’è Geopolitica” che ha avuto tra l’altro il pregio di evidenziare come l’uso degli strumenti audiovisivi possa contribuire efficacemente alla divulgazione del pensiero geografico, assolvendo dunque al duplice compito di sostegno alla didattica e alla divulgazione scientifica, producendo al contempo nuove modalità narrative del sapere geografico rileggendo in chiave spaziale la dimensione politica della società. Questo breve dialogo nasce così da una duplice esigenza. Da un lato, nei termini cioè che più direttamente competono agli obiettivi che questa rubrica si prefigge, evidenziare il nesso tra comunicazione del sapere geografico e profondità della riflessione teorico-metodologica sulla spazialità e la territorialità; dall’altro proporre, per quanto qui possibile, esempi di pratiche della didattica innovanti

Enhanced backward wave propagation in evanescent waveguides loaded with split ring resonators

This paper reports on the design and experimental characterization of evanescent waveguides loaded with split ring resonators SRRs supporting enhanced backward wave propagation. With respect to previous negative refractive index devices based on metallic waveguides, the use of a direct coaxial probe excitation inside an evanescent waveguide drastically improves transmission and reflection characteristics of the periodic structure. Moreover, the addition of metallic windows interleaved between consecutive resonators offers an extra degree of freedom in order to control interresonator couplings, and hence, device parameters like overall transmission, reflection, and bandwidth of the backward wave pass band. A numerical and experimental analysis of different structures overcoming the high loss issue of previously published results is detailed. An experimental validation of the proposed enhancements is done for periodic structures, where no individual tuning of the resonator sections is performed. The proposed technology mainly offers the advantage of miniaturization, and it could be combined in a further step with standard design techniques to provide frequency selective devices.Ministerio de Educación y Ciencia, Gobierno de España-TEC-2004-04313-C02-01 y TEC-2004-04249.C02-02Generalitat Valenciana-ACOMP06/013 y GVA/2007/21

Propagation Characteristics of Groove Gap Waveguide Below and Above Cutoff

(c) 2015 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.Recently, gap waveguides have been shown as a potential alternative to convenational waveguides in the millimeter-wave band. Until now, groove gap waveguide (GGW) has been studied through direct correspondence with rectangular waveguide with the same physical dimensions. However, there have been observed differences in the above cutoff propagation characteristics between these two waveguide types. Furthermore, the behavior of GGW below cutoff remains unknown. This work presents a discussion of both below and above cutoff propagation characteristics of GGW, and introduces a simple model that explains the observed GGW behavior and establishes well its propagation characteristics. Two thru-reflect-line calibration kits have been manufactured, and the measurements have good agreement with the proposed analysis model results.This work was supported by the Spanish Ministerio de Economia y Competitividad under Project TEC2013-47360-C3-3-P and Project TEC2013-47037-C5-1-R and by the Spanish Ministerio de Educacion under FPU Research Fellowship Program AP2010-4227.Berenguer Verdú, AJ.; Fusco, V.; Zelenchuk, DE.; Sánchez-Escuderos, D.; Baquero Escudero, M.; Boria Esbert, VE. (2016). Propagation Characteristics of Groove Gap Waveguide Below and Above Cutoff. IEEE Transactions on Microwave Theory and Techniques. 64(1):27-36. https://doi.org/10.1109/TMTT.2015.2504501S273664

Design Procedure for Band-Pass Filters based on Integrated Coaxial and Rectangular Waveguide Resonators

In this paper, we present a novel band-pass filter based on dual-mode resonators. The dual-mode operation is based on integrated coaxial and rectangular waveguide cavities. Furthermore, we also discuss a systematic design procedure for the selection of the dimensions of the various constituent elements of the filter, that is based on the well-known aggressive space mapping technique. The design of a 5-pole band-pass filter operating in the X-band is discussed in detail, including also measured data. The comparison between simulations and measurement shows very good agreement, thereby fully validating both the new filter structure, and the design procedure

A Novel Technique for Mitigating Multipactor by Means of Magnetic Surface Roughness

Multipactor phenomena which are closely linked to the SEY (secondary electron yield)can be mitigated by many different methods including groves in the metal surface as well as using electric or magnetic bias fields. However frequently the application of global magnetic or electric bias field is not practicable considering the weight and power limitations on-board satellites. Additionally, surface grooves may degrade the RF performance. Here we present a novel technique which is based on a magnetostatic field pattern on the metallic surface with fast spatial modulation in the order of 30 micron. This field pattern is produced by proper magnetization of an underlying ferromagnetic layer such as nickel. Simulations and preliminary experimental results will be shown and a number of applications, both for particle accelerators and satellite microwave payloads are discussed