546 research outputs found
Enhancing crowdsourcing success: the role of creative and deliberate problem-solving styles
A growing number of firms are using crowdsourcing platforms to actively solicit the skills of external entities to help them solve innovation-related problems. Despite its increasing popularity, crowdsourcing has produced mixed success, because few external experts provide helpful solutions. The current research examines this issue by exploring why some external solvers are more successful than others. Grounded in dual-processing theory, this study combines survey and archival data to assess the impact of creative versus deliberate problem-solving styles on solving success. The results indicate that both styles can be effective, but their relative success depends on the amount of time a solver invests in a solution and his or her degree of contextual familiarity with the problem. Specifically, creative (deliberate) styles are more effective under conditions of high (low) contextual familiarity and shorter (longer) time investments. When solvers employ both styles, overall problem-solving success declines. Data source: surve
The critical current density of advanced internal-Mg-diffusion-processed MgB2 wires
Recent advances in MgB2 conductors are leading to a new level of performance.
Based on the use of proper powders, proper chemistry, and an architecture which
incorporates internal Mg diffusion (IMD), a dense MgB2 structure with not only
a high critical current density Jc, but also a high engineering critical
current density, Je, can be obtained. In this paper, a series of these advanced
(or second - generation, "2G") conductors has been prepared. Scanning electron
microscopy and associated energy dispersive X-ray spectroscopy were applied to
characterize the microstructures and compositions of the wires, and a dense
MgB2 layer structure was observed. The best layer Jc for our sample is 1.07x105
A/cm2 at 10 T, 4.2 K, and our best Je is seen to be 1.67x104 A/cm2 at 10 T, 4.2
K. Optimization of the transport properties of these advanced wires is
discussed in terms of B-powder choice, area fraction, and the MgB2 layer growth
mechanism.Comment: 13 pages, 3 tables, 7 figures (or 8 pp in published version
Effect of Heat Treatments under High Isostatic Pressure on the Transport Critical Current Density at 4.2 K and 20 K in Doped and Undoped MgB2 Wires
Annealing undoped MgB2 wires under high isostatic pressure (HIP) increases transport critical current density (Jtc) by 10% at 4.2 K in range magnetic fields from 4 T to 12 T and significantly increases Jtc by 25% in range magnetic fields from 2 T to 4 T and does not increase Jtc above 4 T at 20 K. Further research shows that a large amount of 10% SiC admixture and thermal treatment under a high isostatic pressure of 1 GPa significantly increases the Jtc by 40% at 4.2 K in magnetic fields above 6 T and reduces Jtc by one order at 20 K in MgB2 wires. Additionally, our research showed that heat treatment under high isostatic pressure is more evident in wires with smaller diameters, as it greatly increases the density of MgB2 material and the number of connections between grains compared to MgB2 wires with larger diameters, but only during the Mg solid-state reaction. In addition, our study indicates that smaller wire diameters and high isostatic pressure do not lead to a higher density of MgB2 material and more connections between grains during the liquid-state Mg reaction
Drawing induced texture and the evolution of superconductive properties with heat treatment time in powder-in-tube in-situ processed MgB2 strands
Monocore powder-in-tube MgB2 strands were cold-drawn and heat-treated at 600C
and 700C for times of up to 71 hours and structure-property relationships
examined. Drawing-induced elongation of the Mg particles led, after HT, to a
textured macrostructure consisting of elongated polycrystalline MgB2 fibers
separated by elongated pores. The superconducting Tc, Jc and Fp were correlated
with the macrostructure and grain size. Grain size increased with HT time at
both 600C and 700C. Jc and hence Fp decreased monotonically but not linearly
with grain size. Overall, it was observed that at 700C, the MgB2 reaction was
more or less complete after as little as 30 min; at 600C, full reaction
completion did not occur until 71 h. into the HT. Transport, Jct(B) was
measured in a perpendicular applied field, and the magnetic critical current
densities, Jcm\bot(B) and Jcm{\phi}(B), were measured in perpendicular and
parallel (axial) applied fields, respectively. Particularly noticeable was the
premature dropoff of Jcm\bot(B) at fields well below the irreversibility field
of Jct(B). This effect is attributed to the fibrous macrostructure and its
accompanying anisotropic connectivity. Magnetic measurements with the field
directed along the strand axis yielded a critical density, Jcm\bot(B), for
current flowing transversely to the strand axis that was less than and dropped
off more rapidly than Jct(B). In the conventional magnetic measurement, the
loop currents that support the magnetization are restricted by the lower of
Jct(B) and Jcm{\phi} (B). In the present case the latter, leading to the
premature dropoff of the measured Jcm(B) compared to Jct(B) with increasing
field. This result is supported by Kramer plots of the Jcm{\phi} (B) and Jct(B)
data which lead to an irreversibility field for transverse current that is very
much less than the usual transport-measured longitudinal one, Birr,t.Comment: 41 pages, 14 figure
- …