Performance of soft dielectric laminated composites

This paper contains a thorough investigation of the performance of electrically activated layered soft dielectric composite actuators under plane deformation. Noting that the activation can be induced controlling either the voltage or the surface charge, the overall behaviour of the system is obtained via homogenization at large strains taking either the macroscopic electric field or the macroscopic electric displacement field as independent electrical variable. The performance of a two-phase composite actuator compared to that of the homogeneous case is highlighted for few boundary-value problems and for different values of stiffness and permittivity ratios between constituents being significant for applications, where the soft matrix is reinforced by a relatively small volume fraction of a stiff and high-permittivity phase. For charge-controlled devices, it is shown that some composite layouts admit, on one hand, the occurrence of pull-in/snap-through instabilities that can be exploited to design release-actuated systems, on the other, the possibility of thickening at increasing surface charge density

La liberalizzazione dell'autotrasporto

Il valore della sicurezza, bene fondamentale e insito nella stes¬sa natura del trasporto e perseguito in tutta la materia in generale, nella presente normativa viene incoronato ufficialmente come “bene primario”. Mai il sistema della libera concorrenza può intaccare la sicu¬rezza: si può, infatti, affermare che il limite ufficioso alla libera¬lizzazione del commercio in generale è la tutela della sicurezza: garantire un certo standard è un dovere non solo nazionale e del singolo, ma ancor prima globale e sopranazionale. Si vuole col presente saggio indicare gli elementi di maggior interesse della nuova normativa. La normativa indirettamente induce le parti all’utilizzo della forma scritta, modalità di maggior trasparenza e certezza, poiché l’assenza della stessa determina degli obblighi in capo alle parti di concreta gravosa realizzazione. La normativa vuole gravare fortemente le parti di un contratto di trasporto che hanno preferito la superficialità e poca chiarezza di una contrattazione orale rispetto all’evidenza e tra¬sparenza di una contrattazione scritta. La nuova regolamentazione, così attenta alla sicurezza e netta¬mente distinta dalla precedente, mostra il suo obbiettivo diretto a far si che ogni soggetto interessato al servizio si trovi a rispondere per le conseguenze delle proprie volontà, prevedendo la sanzione della nullità per qualsivoglia patto contrario, così che il soggetto comunque debole contrattualmente, non sia costretto ad assumere totalmente le responsabilità del servizio per non perdere un cliente

Optimal energy-harvesting cycles for load-driven dielectric generators in plane strain

The performances of energy harvesting generators based on dielectric elastomers are investigated. The configuration is of a thin dielectric film coated by stretchable electrodes at both sides. The film is first stretched, then charged and subsequently, afterwards it is released, and finally the charge is harvested at a higher electric potential. The amount of energy extracted by this cycle is bounded by the electric breakdown and the ultimate stretch ratio of the film as well as by structural instabilities due to loss of tension. To identify the optimal cycle that complies with these limits we formulate a constraint optimization problem and solve it with a dedicated solver for two typical classes of elastic dielectrics. As anticipated, we find that the performance of the generator depends critically on the ultimate stretch ratio of the film. However, more surprising is our finding of a universal limit on the dielectric strength of the film beyond which the optimal cycle is independent of this parameter. Thus, we reveal that, regardless of how large the dielectric strength of the material is, there is an upper bound on the amount of harvested energy that depends only on the ultimate stretch ratio. We conclude the work with detailed calculations of the optimal cycles for two commercially available elastic dielectrics

LTE enhancements for Public Safety and Security communications to support Group Multimedia Communications

Currently Public Safety and Security communication systems rely on reliable and secure Professional Mobile Radio (PMR) Networks that are mainly devoted to provide voice services. However, the evolution trend for PMR networks is towards the provision of new value-added multimedia services such as video streaming, in order to improve the situational awareness and enhance the life-saving operations. The challenge here is to exploit the future commercial broadband networks to deliver voice and multimedia services satisfying the PMR service requirements. In particular, a viable solution till now seems that of adapting the new Long Term Evolution technology to provide IP-based broadband services with the security and reliability typical of PMR networks. This paper outlines different alternatives to achieve this goal and, in particular, proposes a proper solution for providing multimedia services with PMR standards over commercial LTE networks.Comment: IEEE Network Magazine, to appea

Instabilities in Multilayered Soft Dielectrics

Experimental observations clearly show that the performance of dielectric elastomeric-based devices can be considerably improved using composite materials. A critical issue in the development of composite dielectric materials toward applications is the prediction of their failure mechanisms due to the applied electromechanical loads. In this paper we investigate analytically the influence of electromechanical finite deformations on the stability of multilayered soft dielectrics under plane-strain conditions. Four different criteria are considered: (i) loss of positive definiteness of the tangent electroelastic constitutive operator, (ii) existence of diffuse modes of bifurcation (microscopic modes), (iii) loss of strong ellipticity of the homogenized continuum (localized or macroscopic modes), and (iv) electric breakdown. While the formulation is developed for generic isotropic hyperelastic dielectrics, results are presented for the special class of ideal dielectrics incorporating a neo-Hookean elastic response. The effect of material properties and loading conditions is investigated, providing a detailed picture of the different possible failure modes.Engineering and Applied Science

Il trasporto a fune: sviluppi tecnici per la sicurezza del trasportato

Si vuole ora sottoporre l’attenzione sullo sviluppo di dispositivi atti a prevenire uno dei più frequenti incidenti che occorrono durante l’eserci¬zio: la caduta di bambini dalle seggiole. Per evitare questo pericolo, molti Direttori d’Esercizio suggeriscono alle società esercenti di realizzare im¬pianti funiviari a veicoli chiusi (cabinovie). Non sempre le elevate portate come quelle offerte da tali impianti rispecchiano le effettive necessità dei tracciati o siti da asservire risultando a volte sovradimensionati. Oltre a tale tipologia d’impianti si è sviluppata la tecnica del TELEMIX che offre all’utenza che intende servirsi di un dato impianto la possibilità di scegliere tra un veicolo aperto (seggiola) ed uno chiuso (cabina) . In questa situazione un maestro con bambini può scegliere di viaggiare in sicurezza con i suoi giovani alunni in cabine chiuse. Contrariamente, chi intende viaggiare senza doversi staccare gli sci dagli scarponi può como¬damente optare per la risalita sulle seggiole. Tale decisione deve essere presa prima dell’incanalamento ai tornelli dal momento che i piani di im¬barco risultano separati e non comunicanti

Experimental investigation of the elastoplastic response of aluminum silicate spray dried powder during cold compaction

Mechanical experiments have been designed and performed to investigate the elasto-plastic behaviour of green bodies formed from an aluminum silicate spray dried powder used for tiles production. Experiments have been executed on samples obtained from cold compaction into a cylindrical mould and include: uniaxial strain, equi-biaxial flexure and high-pressure triaxial compression/extension tests. Two types of powders have been used to realize the green body samples, differing in the values of water content, which have been taken equal to those usually employed in the industrial forming of traditional ceramics. Yielding of the green body during compaction has been characterized in terms of yield surface shape, failure envelope, and evolution of cohesion and void ratio with the forming pressure, confirming the validity of previously proposed constitutive models for dense materials obtained through cold compaction of granulates.Comment: 17 pages; Journal of the European Ceramic Society, 201

LOS PROCESOS DE ACREDITACIÓN DE CARRERAS DE INGENIERÍA EN ARGENTINA: ANÁLISIS DE LOS COMPROMISOS ASUMIDOS Y LOS CAMBIOS EFECTIVAMENTE APLICADOS

Producir cambios en los planes de estudio de las carreras de grado y la modificación de las prácticas académicas que se desarrollan en torno a los mismos, suelen de ser proyectos, principalmente en las Instituciones de Educación Superior de gestión pública, que demandan gran esfuerzo y que tienen baja probabilidad de concluir con éxito. Durante los últimos años, se llevaron a cabo en Argentina procesos de acreditación de carreras de grado en el marco de lo establecido por el artículo 43º de la Ley de Educación Superior. El proceso de acreditación de algunas de las carreras de ingeniería, en particular el que se ejecutó para las carreras comprendidas por la Resolución 1231/01 del Ministerio de Educación, permite evaluar si los compromisos que se asumen como parte de los planes de mejora que derivan de dicho proceso llegan a cumplirse en los plazos previstos. En este trabajo, presentamos los resultados del análisis que llevamos a cabo respecto de los compromisos asumidos por todas las unidades académicas que se vieron involucradas en el proceso ya citado, utilizando como fuente los informes de la Comisión Nacional de Evaluación y Acreditación Universitaria, y el grado de cumplimiento de los mismos en los plazos previstos. Hemos verificado que, más allá de los cuestionamientos y resistencia que se generan en las instituciones al verse atravesadas por estos procesos de acreditación de carreras que ponen en tensión la autonomía universitaria, los mismos han dotado de un dinamismo significativo a aquellas carreras que se encontraron involucradas en estos procesos diferenciándolas, claramente, de aquellas carreras de las mismas unidades académicas que no debieron acreditarse

Treated incidence of psychotic disorders in the multinational EU-GEI study

Jongsma, H.E., Gayer-Anderson, C., Lasalvia, A., Quattrone, D., Mulè, A., Szöke, A., Selten, J.-P., Turner, C., Arango, C., Tarricone, I., Berardi, D., Tortelli, A., Llorca, P.-M., De Haan, L., Bobes, J., Bernardo, M., Sanjuán, J., Santos, J.L., Arrojo, M., Del-Ben, C.M., Menezes, P.R., Murray, R.M., Rutten, B.P., Jones, P.B., Van Os, J., Morgan, C., Kirkbride, J.B., Reininghaus, U., Di Forti, M., Hubbard, K., Beards, S., Stilo, S.A., Tripoli, G., Parellada, M., Cuadrado, P., Solano, J.J.R., Carracedo, A., Bernardo, E.G., Roldán, L., López, G., Cabrera, B., Lorente-Rovira, E., Garcia-Portilla, P., Costas, J., Jiménez-López, E., Matteis, M., Rapado, M., González, E., Martínez, C., Sánchez, E., Olmeda, M.S., Franke, N., Velthorst, E., Termorshuizen, F., Van Dam, D., Van Der Ven, E., Messchaart, E., Leboyer, M., Schürhoff, F., Jamain, S., Frijda, F., Baudin, G., Ferchiou, A., Pignon, B., Richard, J.-R., Charpeaud, T., Tronche, A.-M., La Barbera, D., La Cascia, C., Marrazzo, G., Sideli, L., Sartorio, C., Ferraro, L., Seminerio, F., Loureiro, C.M., Shuhama, R., Ruggeri, M., Tosato, S., Bonetto, C., Cristofalo, D