We report phase locking of a diode-pumped multicore fiber laser with a circular array of 18 Nd-doped emitters (microcores) acting as an active medium. Phase locking was achieved in a Talbot resonator configuration. We present calculations of the effective reflection coefficients that are due to self-imaging. Far-field distributions and near-field pattern of several supermodes are calculated and compared with experimental results.
How can firms engaged in distributed innovation attract external volunteers and direct their efforts efficiently and effectively? Extant research proposes financial rewards as suitable management practice, maintaining that extrinsic financial rewards and intrinsic motivation have a unidimensionally positive effect on volunteers' motivation. In contrast, using the same theory underlying these studies, we argue that the effect of payment is far more complex. To do so, we introduce the concept of payment norms as a moderator of the effect of payment on motivation. Conducting a scenario experiment with open source software developers, we find that intrinsic motivation decreases for individuals with norms against payment, and that self‐determination mediates this effect. Furthermore, payment has a direct positive effect on total motivation, but not for individuals with strong norms for payment. Our findings help explain conflicting earlier results on motivation crowding and contribute to the debate on how to manage external volunteers in distributed innovation settings.
This paper deals with a crack propagation analysis of welded structures and rehabilitation after pre-fatigue loading by the high-frequency mechanical impact (HFMI) posttreatment technique. The investigated specimen type is a thinwalled longitudinal stiffener made of mild steel S355. Fracture mechanical calculations are primarily performed on the basis of the weight-function approach. Thereby, the local residual stress condition at the weld toe is considered by the aid of a structural weld simulation, whereas the numerically evaluated residual stress distribution in depth agrees well to X-ray measurement results. The fracture mechanical analysis illustrates that by incorporating the residual stress state, the calculated lifetime is in good accordance to the conducted fatigue test results. By application of the HFMI-treatment as rehabilitation method, it is found that the beneficial post-treatment effect increases especially by a reduction of the applied load-level. Hence, particularly for minor nominal stress ranges near the high-cycle fatigue region, the mechanical post-treatment as repair method is utmost effective leading to almost equal fatigue strength as for the HFMI-treated specimens without pre-cycling. Finally, proposals for the crack growth assessment of welded structures and a conservative application of HFMI as rehabilitation method for mild steel joints are provided.
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