Test a l'oxyde de carbone en régime stable /

Overdruk uit: Bulletin de Physio-pathologie respiratoire ; 2(1966), p. [189]-19

Comparison of alternating-current losses in two-layer superconducting cables constructed by shell-type and solid-core cylindrical wires

Alternating-current losses in two-layer power transmission cables of type-II superconducting wires with cylindrical geometry are numerically investigated with regard to wire cross section. Losses in shell-type and solid-core superconducting wires are calculated through the Finite Element Method for an applied alternating current with 50 Hz frequency. Each cable layer is composed of 20 wires which have 1.0 mm radii, while the thickness of shell-type wires is 0.1 mm. The two wire layers are wound over a copper core such that the inner and outer layer radii are 20.0 and 25.0 mm, respectively. Alternating-current losses at small applied current amplitudes in shell-type wires are three-times smaller than in solid-core wires, where the discrepancy diminishes for high current amplitudes above 90 % of the critical current. Besides, losses in both configurations are considerably higher in outer-layer wires for current amplitudes less than half the critical current, while they converge at higher amplitudes. The reason for smaller losses in shell-type wires at low applied current amplitudes is associated to the fact that current distribution is more homogeneous, whereas magnetic field lines penetrate into the hollow core of these wires. © Springer International Publishing Switzerland 2014

Evaluation of biomass burning across North West Europe and its impact on air quality

Atmospheric particulate pollution is a significant problem across the EU and there is concern that there may be an increasing contribution from biomass burning, driven by rising fuel prices and an increased interest in the use of renewable energy sources. This study was carried out to assess current levels of biomass burning and the contribution to total PM10 across five sites in North-West Europe; an area which is frequently affected by poor air quality. Biomass burning was quantified by the determination of levoglucosan concentrations from PM10 aerosol filters collected over a 14 month period in 2013/2014 and continued for a further 12 months at the UK site in Leicester. Levoglucosan levels indicated a distinct period of increased biomass combustion between November and March. Within this period monthly average concentrations ranged between 23 ± 9.7 and 283 ± 163 ng/m3, with Lille showing consistently higher levels than the sites in Belgium, the Netherlands and the UK. The estimated contribution to PM10 was, as expected, highest in the winter season where the season average percentage contribution was lowest in Wijk aan Zee at 2.7 ± 1.4% and again highest in Lille at 11.6 ± 3.8%, with a PM10 mass concentration from biomass that ranged from 0.56 μg/m3 in Leicester to 2.08 μg/m3 in Lille. Overall there was poor correlation between the levoglucosan concentrations measured at the different sites indicating that normally biomass burning would only affect atmospheric particulate pollution in the local area; however, there was evidence that extreme burning events such as the Easter fires traditionally held in parts of North-West Europe can have far wider ranging effects on air quality. Network validation measurements were also taken using a mobile monitoring station which visited the fixed sites to carry out concurrent collections of aerosol filters; the result of which demonstrated the reliability of both PM10 and levoglucosan measurements