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871.
Whenever one justification for learning mathematics is questioned, educationists have usually been ready to offer an alternative rationale. Often this involves presenting (or re-presenting) the subject in a new light. This paper will consider the implications of trying to invoke creativity in mathematics. We shall argue that 'creativity' is a complex notion and should only be applied to mathematics with caution and attention to meaning. 相似文献
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Tim D.W. Claridge Maksim Mayzel Ēriks Kupče 《Magnetic resonance in chemistry : MRC》2019,57(11):946-952
A series of NMR supersequences are presented for the time-efficient structure characterisation of small molecules in the solution state. These triplet sequences provide HMBC, HSQC, and one homonuclear correlation experiment of choice according to the NMR by Ordered Acquisition using 1H detection principle. The experiments are demonstrated to be compatible with non-uniform sampling schemes and may be acquired and processed under full automation. 相似文献
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877.
The influence of airfoil kinematics on the formation of leading-edge vortices in bio-inspired flight
The formation process of leading-edge vortices has been investigated experimentally using Particle Image Velocimetry. Various
airfoil kinematics have been tested, including asymmetric and peak-shifted plunging motions, and are evaluated for Re = 30,000 and a reduced frequency range of 0.2 ≤ k ≤ 0.33. By measuring the growth in the leading-edge vortex during the dynamic-stall process, the vortex pinch-off process
is examined based on the concept of an optimal vortex formation time. The various kinematics are then evaluated with respect
to their associated vortex strength, timing and convection into the wake. 相似文献
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Tim Fiedler Stephanie Dirksmeyer Dr. Markus Seibald Dr. Franziska Hummel Dr. Simon Peschke Dr. Gina M. Achrainer Dr. Daniel Bichler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):795-798
Innovative materials for phosphor-converted white light-emitting diodes (pc-LEDs) are much sought after due to the huge potential of the LED technology to reduce energy consumption worldwide. One of the main levers for further improvements are the conversion phosphors. The system Ca1−xSrxAlSiN3:Eu2+ currently provides one of the most important red-emitting phosphors for pc-LEDs. We report the discovery of the new polymorph β-Ca1−xSrxAlSiN3:Eu2+ which allows for significant improvements to LED efficacies. It crystallizes in the orthorhombic space group Pbcn with lattice parameters a=982.43(10) pm, b=575.2(1) pm and c=516.12(5) pm. Compared to α-Ca1−xSrxAlSiN3:Eu2+, its emission shows a significantly reduced spectral full-width at half maximum (FWHM). With that, we demonstrated 3 % efficacy increase for white light-emitting pc-LEDs. The new polymorph can easily be industrialised, because the synthesis works on the same equipment as α-Ca1−xSrxAlSiN3:Eu2+. 相似文献