AC losses in Bi,Pb(2223) multifilamentary wires with square cross-section

We have fabricated prototype Bi,Pb(2223)/Ag superconduting multifilamentary wires with a square cross-section. The AC losses of these wires were measured, compared with those of tapes and also compared with the theory. Wires show largely reduced AC magnetic field losses at 47 Hz, compared to those of tapes in a perpendicular magnetic field. The effects of the twist pitch and of the use of the high resisitive barriers were also investigated. The results show that the use of a twist pitch of about 10 mm is sufficient for decoupling the filaments, and that the use of very short twist pitches does not further reduce the absolute value of the AC losses. The losses in the wires are still higher than those of tapes in a parallel magnetic field, but the results show that the square or round configurations are interesting for applications where a perpendicular component of the magnetic field cannot be avoided, or for applications in rotating magnetic fields.Comment: 8 pages, 11 figures, submitted to Physica

The Micro-Pillar Shear-Stress Sensor MPS3 for Turbulent Flow

Wall-shear stress results from the relative motion of a fluid over a body surface as a consequence of the no-slip condition of the fluid in the vicinity of the wall. To determine the two-dimensional wall-shear stress distribution is of utter importance in theoretical and applied turbulence research. In this article, characteristics of the Micro-Pillar Shear-Stress Sensor MPS3, which has been shown to offer the potential to measure the two-directional dynamic wall-shear stress distribution in turbulent flows, will be summarized. After a brief general description of the sensor concept, material characteristics, possible sensor-structure related error sources, various sensitivity and distinct sensor performance aspects will be addressed. Especially, pressure-sensitivity related aspects will be discussed. This discussion will serve as ‘design rules’ for possible new fields of applications of the sensor technology

Think positive? Examining the impact of optimism on academic achievement in early adolescents

Objective: Although optimism\u27s beneficial role for various life areas is well documented, previous findings regarding its significance for students\u27 achievement at school are inconclusive. This study examined the relation between optimism and academic achievement in early adolescents. It investigated the functional form of this relation, addressed whether the initial achievement level moderates this association, and compared this with effects on self-esteem. Method: We used a large German sample (N56,010; 53.2% females; baseline Mage514.1) with two measurement points over a period of 5 months (middle and end of 7th grade). Estimating LOESS curves and latent change-regression models revealed three main findings. Results: (a) Optimism showed a nonlinear association with subsequent changes in academic achievement: Optimism promoted academic achievement, but this positive association reached a plateau in above-average optimism ranges and a minimum value in below-average ranges of optimism. (b) The achievement level at t1 moderated this relation so that high optimism exerted a more positive effect for high-achieving adolescents. (c) By contrast, optimism had an overall positive effect on self-esteem. Conclusions: The results therefore broaden the evidence on benefits of optimism by linking optimism to academic success in early adolescents but indicate only small and nonlinear associations. (DIPF/Orig.

The 2015 Illapel earthquake, central Chile: A type case for a characteristic earthquake?

On 16 September 2015, the MW = 8.2 Illapel megathrust earthquake ruptured the Central Chilean margin. Combining inversions of displacement measurements and seismic waveforms with high frequency (HF) teleseismic backprojection, we derive a comprehensive description of the rupture, which also predicts deep ocean tsunami wave heights. We further determine moment tensors and obtain accurate depth estimates for the aftershock sequence. The earthquake nucleated near the coast but then propagated to the north and updip, attaining a peak slip of 5–6 m. In contrast, HF seismic radiation is mostly emitted downdip of the region of intense slip and arrests earlier than the long period rupture, indicating smooth slip along the shallow plate interface in the final phase. A superficially similar earthquake in 1943 with a similar aftershock zone had a much shorter source time function, which matches the duration of HF seismic radiation in the recent event, indicating that the 1943 event lacked the shallow slip