101,968 research outputs found
Imaging ecografico delle vie biliari: riduzione del rischio radiologico e benefici clinici
No full textExperimental Investigation of the Effect of Transient Overvoltages on XLPE-Insulated HVDC Cables
No full textHVDC cables are subject to several types of impulses superimposed on the rated DC voltage during their service lifetime. Temporary Overvoltages (TOVs) and Superimposed Switching impulses (SSIs) are considered some of the most challenging due to the relatively long impulse duration. This paper aims at investigating experimentally the effect of TOVs and SSIs on XLPE insulation for extruded HVDC cables. 0.15-mm-thick DC-XLPE specimens, aged by applying TOVs and SSIs, are characterized using dielectric analyzer and Fourier Transform InfraRed spectroscopy (FTIR) to detect the aging effects on the insulation. Results show an increase in the imaginary part of permittivity, ε", accompanied with the appearance of additional dipolar polarization losses peaks. The amplitude and frequency of the aforementioned peaks vary with the amplitude and the number of applied TOVs and SSIs. An increase in electrical conductivity is also noticed with aging. FTIR results show absorbance peaks in the aged specimens likely due to the intramolecular bonds rupture accompanied with the formation of aging products. In summary, SSIs and TOVs cause a noticeable reduction of insulating properties in XLPE specimens. The higher the peak of the transient, the greater the aging effect
L'Ultrasonografia nelle rotture traumatiche del tendine di Achille: valutazione con sonde ad altissima frequenza di un raro caso.
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Uomini e seconde unioni in Italia
No full textThis paper investigate individual characteristic influencing the risk to engage a new relationship after a union disruption for Italians men. In particular, we analyze the transition from first union and the successive one, for both marriage and cohabitation. Among other characteristics we stress on the effect of son on repartnering possibility and territorial differences . Presence of son are mainly investigated in the analysis of women repartnering but we find that also for men children from previous unions induce a decrease on the risk to engage a new relationship. The decreasing effect on the risk estimates show a temporal dependency with stronger relationship for new union beginning more than two year after first disruption. Our tested hypothesis is that temporal dynamics depend on the way man could be considered the “principal actor” in taking the decision of interrupt first union or suffer this decision
Safer plasticized polyvinyl chloride synthetic leathers for the automotive industry: Evaluation of alternatives to antimony compounds as flame retardants
No full textAutomotive interiors materials, like plasticized polyvinyl chloride (pPVC) synthetic leathers (SLs), require additives for improving their flame behavior. The preferred flame retardant (FR) used in pPVC is antimony trioxide (Sb 2 O 3 , ATO), though the use of antimony poses several issues, for both human health and the environment, related to its extraction, processing, and use. In order to investigate alternatives to ATO in high-performance pPVC SLs, various commercial FRs have been selected and tested in a typical, highly plasticized formulation. These additives have been used either alone or combined to evaluate synergistic effects. Samples have been tested to assess mechanical properties, thermal stability, and flame resistance. Data have been compared with those of neat pPVC and a foil with 2 phr of ATO. Several FRs are effective in improving the flame response compared with neat pPVC, without compromising the other properties, in detail calcium hypophosphite and mixtures containing zinc hydroxystannate (ZHS). Finally, aluminum hydroxide and ZHS (ATH + ZHS) yields the cheaper among the alternatives here proposed, even though higher than ATO (+193%) whose price/performance ratio is difficult to overcome. POLYM. ENG. SCI., 2019. © 2019 Society of Plastics Engineers
Optimization of Pyro-gasification of Carbon Fiber Reinforced Polymers (CFRPs)
No full textThis work focuses on the optimization of pyro-gasification process of carbon fiber reinforced polymers (CFRPs) with the aim of recovering carbon fibers (CFs) with properties suitable for the production of new more sustainable composites with high performances. In particular, the pyro-gasification process is carried out on cured CFRPs panels based on both epoxy (EC) and vinyl ester (VC) matrices, which are the two most used resins for CFRPs. The matrix degradation is evaluated via sample's weight loss measurement and the recovered CFs obtained after different time of treatment are analyzed to identify convenient pyro-gasification conditions to avoid damaging of the recovered CFs. The obtained results highlight the importance of the thickness of the composites to be treated for the identification of the more suitable pyro-gasification conditions
Descrizione di un caso clinico di neurinoma del nervo surale: ruolo della diagnostica ecografica.
No full textThe effects of the industrial processing on commercial polyhydroxyalkanoates
No full textIn the last years polyhydroxyalkanoates (PHAs) gained increasing attention as potential sustainable replacement of current plastics from fossil sources. PHAs are biodegradable polymers which can be produced from bacteria exploiting waste as feedstock. In order to bring these polymers on the market, it is necessary to know their properties and assess the effects of industrial processing stages on the final material. For this reason, in this work different industrial PHAs were investigated. These materials were structurally characterized and their thermal properties were assessed. Furthermore, they were subjected to different thermal and thermo—mechanical treatments (various time, temperature and frequency of rotation in the extruder) in order to study the effect of the applied conditions on the properties of the final material
Recycling of carbon fiber reinforced composite waste to close their life cycle in a cradle-to-cradle approach
No full textCarbon fiber reinforced polymers (CFRPs), with a demand expected to reach 194 ktons by 2022 and a global market increase to $48.7 billion are increasingly popular materials because of their ability to conjugate superior mechanical resistance and lightness, thus allowing their widespread application ranging from aerospace and wind turbines to automotive and sporting goods. A foreseeable consequence is the growth of production scraps and end-of-life composites. Considering the still high cost of the virgin carbon fiber (CF) and a CF demand expected to reach 117 ktons by 2022 (average of 30 €/kg and energetic cost of 183–286 MJ/kg), this review outlines recent advances of the existing methods to recycle cumulative composite wastes, still with many unresolved problems and issues, with emphasis on CF recovery and understanding their retained properties. Finally, a brief overview on the companies that offer carbon fiber reinforced polymer recovery services with the aim of addressing the issue of end of life is presented
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