Browsing by Author "Wang, Yan"

Now showing 1 - 2 of 2

Color Difference and Thermal Stability of Flexible Transparent InGaN/GaN Multiple Quantum Wells Mini-LED Arrays
(2020-07-01)
Lu, Bo
;
Wang, Yan
;
Hyun, Byung-Ryool
;
Kuo, Hao-Chung
;
Liu, Zhaojun
We present studies of the color uniformity and thermal stability of a flexible and transparent 32 x 32 mini-LED array on polyethylene terephthalate (PET) substrate up to a brightness rating of 5000 nits at room temperature, whose brightness is required for outdoor display applications. Surprisingly, even at 5000 nits, the temperature variation on the surface of the LED array is less than 9 degrees C, despite the relatively low thermal diffusivity of the polymer substrates. The average surface temperature was 33 degrees C. This indicates that the heat dissipation of the fabricated LED array is superior with even a polymer substrate. Further, the narrow electroluminescent (EL) emissions from the mini-LED array help to realize wider color gamut than Rec. 2020 color gamut in display applications. The color differences from the EL spectra were calculated at three different brightness. The calculated values are far less than the color discrimination threshold of the human eye corresponding to 0.005 at all testing brightness and meet the display industry requirement for color difference.
Ultramicrostructural reductions in teeth: implications for dietary transition from non-avian dinosaurs to birds
(2020-04-21)
Li, Zhiheng
;
Wang, Chun-Chieh
;
Wang, Min
;
Chiang, Cheng-Cheng
;
Wang, Yan
Background Tooth morphology within theropod dinosaurs has been extensively investigated and shows high disparity throughout the Cretaceous. Changes or diversification in feeding ecology, i.e., adoption of an herbivorous diet (e.g., granivorous), is proposed as a major driver of tooth evolution in Paraves (e.g., Microraptor, troodontids and avialans). Here, we studied the microscopic features of paravian non-avian theropod and avialan teeth using high-spatial-resolution synchrotron transmission X-ray microscopy and scanning electron microscopy. Results We show that avialan teeth are characterized by the presence of simple enamel structures and a lack of porous mantle dentin between the enamel and orthodentin. Reduced internal structures of teeth took place independently in Early Cretaceous birds and a Microraptor specimen, implying that shifts in diet in avialans from that of closely related dinosaurs may correlate with a shift in feeding ecology during the transition from non-avian dinosaurs to birds. Conclusion Different lines of evidence all suggest a large reduction in biting force affecting the evolution of teeth in the dinosaur-bird transition. Changes in teeth microstructure and associated dietary shift may have contributed to the early evolutionary success of stemward birds in the shadow of other non-avian theropods.