Solar silicon from directional solidification of MG silicon produced via the silicon carbide route

A process of metallurgical grade (MG) silicon production is presented which appears particularly suitable for photovoltaic (PV) applications. The MG silicon is prepared in a 240 KVA, three electrode submerged arc furnace, starting from high grade quartz and high purity silicon carbide. The silicon smelted from the arc furnace was shown to be sufficiently pure to be directionally solidified to 10 to 15 kg. After grinding and acid leaching, had a material yield larger than 90%. With a MG silicon feedstock containing 3 ppmw B, 290 ppmw Fe, 190 ppmw Ti, and 170 ppmw Al, blended with 50% of off grade electronic grade (EG) silicon to reconduct the boron content to a concentration acceptable for solar cell fabrication, the 99% of deep level impurities were concentrated in the last 5% of the ingot. Quite remarkably this material has OCV values higher tham 540 mV and no appreciable shorts due to SiC particles

Phase diagram of magnetic domain walls in spin valve nano-stripes

We investigate numerically the transverse versus vortex phase diagram of head-to-head domain walls in Co/Cu/Py spin valve nano-stripes (Py: Permalloy), in which the Co layer is mostly single domain while the Py layer hosts the domain wall. The range of stability of the transverse wall is shifted towards larger thickness compared to single Py layers, due to a magnetostatic screening effect between the two layers. An approached analytical scaling law is derived, which reproduces faithfully the phase diagram.Comment: 4 page

Layer-resolved imaging of domain wall interactions in magnetic tunnel junction-like trilayers

We have performed a layer-resolved, microscopic study of interactions between domain walls in two magnetic layers separated by a non-magnetic one, using high-resolution x-ray photoemission electron microscopy. Domain walls in the hard magnetic Co layer of a Co/Al2O3/FeNi trilayer with in-plane uniaxial anisotropy strongly modify the local magnetization direction in the soft magnetic FeNi layer. The stray fields associated to the domain walls lead to an antiparallel coupling between the local Co and FeNi moments. For domain walls parallel to the easy magnetization axis this interaction is limited to the domain wall region itself. For strongly charged (head-on or tail-to-tail) walls, the antiparallel coupling dominates the interaction over radial distances up to several micrometers from the centre of the domain wall.Comment: Published version, J. Phys.: Condens. Matter 19, 476204 (2007

Do Higher Wages Pay for Themselves? An Intra-firm Test of the Effect of Wages on Employee Performance

Conference: AAA 2015 Management Accounting Section (MAS) Meeting, AAA 2015 Annual meeting, Volume: http://ssrn.com/abstract=2482829This study uses field data from 490 hotels in a single lodging chain to investigate three questions related to the efficiency-wage hypothesis. (1) Does paying workers higher relative wages ex ante result in better ex post actual performance, either by motivating workers to exert greater effort or by attracting higher quality workers? (2) Is the magnitude of the relation between performance and wages the same when workers are overpaid versus underpaid? (3) Do the overall benefits of paying higher wages outweigh the costs? The data enable us to perform powerful tests of wageperformance relations because exogenous factors that likely affect employee behavior are standardized across hotels. Our results suggest that actual performance (measured by customer satisfaction, revenues, and profit) is increasing in the relative wage, and that higher performance is the result, and not the cause, of higher wages. We find that the magnitude of the wageperformance relation is at least as large for workers who are overpaid compared to those who are underpaid. This result, which differs from the results of experimental studies, suggests that overpaid workers do not rationalize away wage premiums. Finally, our results indicate that increases in wages do, in fact, pay for themselves. A $1,000 increase in the general manager’s relative wage results in a$1,080 increase in profit for the mean hotel. This research contributes to a series of studies that investigates the extent to which wages influence performance (e.g., Levine, 1992; Fehr and Falk, 1999; Hannan, Kagal, and Moser, 2002; Hannan, 2005), and whether the marginal benefit of wage increases justifies their costs (Levin, 1993)