In order to improve the measurement accuracy of cylinder shell resonating density meter, the paper presents many means
of methods to lower the measurement error from the liquid temperature, pressure, viscidity and gas bubble in the liquid,
and designs a novel cylinder shell resonating density meter. Taking typical calibration experiments as example, the paper
gives the detailed steps of calculating uncertainty component of the cylinder shell resonating density meter, and values
the combined uncertainty. The experiments and analysis show the combined uncertainty is 0.96kg/m3 when the
measurement result is 785.16 kg/m3, and the relative uncertainty is 0.12%.
GaN-based light-emitting diode (LED) has been widely used in recent years, and tremendous progress has been achieved in GaN-based semiconductor materials and relevant process. However, owing to the large refractive index contrast between GaN-based semiconductor materials and air, light can be easily totally internally reflected at the semiconductor/air interface, and the critical angle for light to escape from the semiconductor is small. Therefore, the light extraction efficiency for GaN-based LED is still low and needs improving. Some of the leading approaches to enhance light extraction efficiency of GaN-based LED such as surface texturing or roughening, omnidirectional reflectors, photonic crystals, laser liftoff, transparent electrode, patterned substrate and so on are introduced in detail. For each approach, how the variation in device structure or material improves the light extraction efficiency is analyzed thoroughly. At last, some of mentioned approaches that are promising are evaluated and viewed briefly.