The evaluation of the spatial luminance coefficient, Feu, and average luminance, Lav, can improve the lighting quality from both subjective and objective aspects. In the design survey, the determination of these indicators relies on the manual sampling of the luminance of measurement points, which is time-consuming and labour-intensive. This article proposes a grayscale−luminance converting polynomial function, and a method for the determination of Feu and Lav from digital images via the function. The acceptability index, Nallow, is created as the key parameter of the polynomial function, which reduces the number of required measurement points to 9. Taking visual comfort as the criterion, three types of low-contrast working conditions with different luminance distributions – namely an actual scene, simulated scenes and experimental scenes – were set, the luminance ratios of which were less than 100 and the luminance of which was less than 1000 cd/m2. To minimise the error to within 10%, the piecewise function of Nallow determined by the luminance ratio was constructed, which is obtained via the data verification and correction of 20 working conditions. The experimental results of a test scene demonstrate that the accuracies of Feu and Lav produced by the proposed polynomial function were better than those produced by an exponential function.
17The insulin-secreting cells generated from stem cells in vitro are less glucose responsive than 18 primary β-cells. To search for the missing ingredients that are needed for β-cell maturation, we 19 have longitudinally monitored function of every β-cell in Tg (ins:Rcamp1.07) zebrafish embryos 20 with a newly-invented two-photon light-sheet microscope. We have shown that β-cell maturation 21 begins from the islet mantle and propagates to the islet core during the hatching period, coordinated 22 by the islet vascularization. Lower concentration of glucose is optimal to initiate β-cell maturation,
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