Electrical properties of nanostructured polypropylene: a matter of morphology?

This work investigates an alternative view on the mechanisms behind the modification of electrical properties in a filled dielectric, based on the variation of morphological properties of materials. The case of a nanostructured polypropylene-based blend will be analysed, highlighting the morphological changes observed in the bulk of the material with modifications of electrical properties such as space charge accumulation, dielectric strength and conductivity. Results show that nanofillers help inducing an enhanced morphology of the bulk material, with a reduction of phase separation. This in turn results in better breakdown voltage and lower conductivity, but also an increase in space charge accumulation characteristics to unacceptable levels. On the other hand, functionalization of nanoparticles has been proven to be able to reduce charge accumulation to levels lower than the neat base material, despite a similar polymeric morphology. This must be due to the improved filler dispersion observed, clearly showing the added value carried by nanostructuring

Polypropylene/SIO2 Nanocomposite with Improved Dielectric Properties for DC Cables

A new generation of nanostructured polymeric insulating material is being developed under the GRIDABLE European project framework. One of the main objectives of this project is the improvement of the dielectric properties and the life performance of High Voltage DC cables insulating materials. The dielectric performance of pre-production grade PP/SiO2 with different formulations are evaluated in this work by means of space charge accumulation measurements, electrical conductivity tests and statistical analysis of breakdown voltage. Results are compared with state of the art XLPE and PP

Sterilization by Means of a Surface Dielectric Barrier Discharge: Effects of Electro- Hydro- Dynamics and Reactive Species

Since the 1970s, plasma’s capability to increase gases sterilizing potential has been demonstrated. During the 2000s some studies started to investigate the possibility to use plasmas to add sterilizing properties to non-germicidal gases (air, helium…). Years of studies and development have shown how they can be useful to inactivate different bacteria, spores, fungi and yeasts. The high amount of variables influencing a plasma bring to big differences in the effects it can have on a biological payload. Several different chemical compounds can be found in a plasma, depending on the kind of gas one is using and the operating conditions one is igniting the plasma with. In this thesis my work was focused on trying to better understand the differences in sterilizing efficacy of different chemical compounds produced by an atmospheric pressure Dielectric Barrier Discharge (DBD) plasma in air. In particular, the influence of the plasma source design on the Electro-Hydro-Dynamic effect and its products, and the relative importance of NOx species production and concentrations over the Ozone is investigated

Investigating Energization Transients and the Potentiality of Partial Discharge Inception and Damage in Nanofilled Polypropylene Insulation for DC Cables and Capacitors

New nanostructured insulating materials are investigated, within the European project GRIDABLE, to be used for DC cable and capacitors. Besides electrical, thermal and mechanical properties, and life behavior, work is being done to evaluate their capability to endure highly stressing conditions as those cause by the inception of partial discharges, PD. This paper, in particular, analyzes what happens during energization of a DC cable or capacitors, when voltage goes from zero to the nominal value in a few seconds, while the internal electrical field takes longer time to reach the DC steady state configuration. During an energization transient, indeed, electrical field in insulation, and insulation defects (as cavities), is driven by permittivity, not conductivity as in steady state. Hence, PD might occur with high repetition rate, which would not occur, or at much lower repetition rate, in steady state. The way to evaluate the time constant of the transient, that is, through charging current measurement, is described and successfully fitted to the results of PD measurements performed on two types of polypropylene, PP: neat and nanostructured, and a cross-linked polyethylene, XLPE, having significantly different electrical characteristics

Partial discharge measurements of DC insulation systems: the influence of the energization transient

This paper introduces techniques for partial discharge, PD, recognition under DC, both in steady state and in transient condition, during which the field in insulation varies slowly from a permittivity-driven to a conductivity-driven profile. This transient can be significantly long, depending on insulating material characteristics, and condition PD phenomenology and impact of PD on insulation life. Focusing mainly on the behavior of PD repetition rate as a function of time, after insulation energization by a DC voltage step, PD triggered by transient field can be separated from those relevant to steady state, which may indicate a criterion to estimate the partial discharge inception voltage, PDIV, under DC supply

Editoriale: “La PA digitale: un ossimoro italiano?”

This is the Editorial of a special issue of the journal Prisma on: "Innovation in Public Administration: Technologies, Services and Outcomes"

Editoriale: “La PA digitale: un ossimoro italiano?”

This is the Editorial of a special issue of the journal Prisma on: "Innovation in Public Administration: Technologies, Services and Outcomes"

Diffusion and usage of public e-services in Europe: An assessment of country level indicators and drivers

We analyze the state of the art of indicators on eGovernment, eHealth, eProcurement and ePartecipation. We survey the main methodological properties of these indicators, and uncover the principal stylized facts and trends; at the same time, we highlight their heuristic limits and potential inconsistencies. Finally, we address empirically the issue of the explanation of the indexes scores – i.e. how the supply of the various eServices in each country is affected by political, institutional and socio-economic differences, and is followed by actual usage. The econometric analysis uncovers the importance of broadband penetration and higher education as drivers for most of the types of eServices and users (citizens and businesses). Moreover, a corruption-free and agile public sector shows up to be an important pre-condition for more effective supply and usage. Despite severe data limits and the complexity of the underlying diffusion phenomena, our study of eServices availability and usage across European countries is a first empirical contribution aimed at disentangling broad empirical trends – with their correlates - from unresolved methodological issues. As such, this work appears useful to inform the policy debate and practice, in a phase characterized by a prospective reorientation of public eServices provision

Diffusion and usage of public e-services in Europe: An assessment of country level indicators and drivers

We analyze the state of the art of indicators on eGovernment, eHealth, eProcurement and ePartecipation. We survey the main methodological properties of these indicators, and uncover the principal stylized facts and trends; at the same time, we highlight their heuristic limits and potential inconsistencies. Finally, we address empirically the issue of the explanation of the indexes scores – i.e. how the supply of the various eServices in each country is affected by political, institutional and socio-economic differences, and is followed by actual usage. The econometric analysis uncovers the importance of broadband penetration and higher education as drivers for most of the types of eServices and users (citizens and businesses). Moreover, a corruption-free and agile public sector shows up to be an important pre-condition for more effective supply and usage. Despite severe data limits and the complexity of the underlying diffusion phenomena, our study of eServices availability and usage across European countries is a first empirical contribution aimed at disentangling broad empirical trends – with their correlates - from unresolved methodological issues. As such, this work appears useful to inform the policy debate and practice, in a phase characterized by a prospective reorientation of public eServices provision