Silica micro-tube resonators were studied by using a prism-coupled method and act as refractive index sensing elements. Two types of refractive index sensing modes were observed experimentally by tuning the incident angles in the prism-coupled configuration. The resonance mode with sensitivity below 100nm/RIU is a result of the typical evanescent wave interaction with the fluid, while the mode with record high sensitivity of ~ 600nm/RIU is a form of non-evanescent wave with high optical field in the low index fluid region. An analysis of the field distribution of the resonance modes in the micro-tube also revealed the existence of high order modes with strong optical field inside the low index liquid core, which leads to the high index sensitivity. Theoretical calculation of the sensitivity for this specific mode obtained by the Mie scattering method is consistent with the experimental result. A ray optics picture is presented to elucidate the physical nature of this special resonance mode observed in the micro-tube resonator.
Abstract:The summer maize yields and partial factor productivity of nitrogen (N) fertilizer (PFP N , grain yield per unit N fertilizer) on smallholder farms in China are low, and differ between farms due to complex, sub-optimal management practices. We collected data on management practices and yields from smallholder farms in three major summer maize-producing sites-Laoling, Quzhou and Xushui-in the North China Plain (NCP) for two growing seasons, during 2015-2016. Boundary line analysis and a Proc Mixed Model were used to evaluate the contribution of individual factors and their interactions. Summer maize grain yields and PFP N ranged from 6.6 t ha −1 to 14.2 t ha −1 and 15.4 kg kg −1 to 96.1 kg kg −1 , respectively, and averaged 10.5 t ha −1 and 49.1 kg kg −1 , respectively. The mean total yield gap and PFP N gap were 3.6 t ha −1 and 43.3 kg kg −1 in Laoling, 2.2 t ha −1 and 24.5 kg kg −1 in Xushui, and 2.8 t ha −1 and 41.1 kg kg −1 in Quzhou. A positive correlation was observed between the yield gap and PFP N gap; the PFP N gap could be reduced by 6.0 kg kg −1 (3.6-6.6 kg kg −1 ) by reducing the yield gap by 1 t ha −1 . The high yield and high PFP N (HH) fields had a higher plant density and lower N fertilization rate than the low yield and low PFP N (LL) fields. Our results show that multiple management factors caused the yield gap, but the relative contribution of plant density is slightly higher than that of other management practices, such as N input, the sowing date, and potassium fertilizer input. The low PFP N was mainly attributed to an over-application of N fertilizer. To enhance the sustainable production of summer maize, the production gaps should be tackled through programs that guide smallholder farmers on the adoption of optimal management practices.
A liquid filled, low refractive index material inner-coated silica micro-tube has been proposed and studied as a coupled micro-resonator sensor to greatly enhance biochemical sensor sensitivity. Its unique coupling phenomenon has been analyzed and utilized to boost the device's refractive index sensitivity to 967nm/RIU. Through optimization of the coupling strength between the two micro-resonators, further improvement in refractive index sensitivity up to 1100nm/RIU has been achieved. This mode coupling strategy allows us to design robust, thickwalled micro-tube sensors with ultra-high sensitivity which is useful in practical biochemical sensing applications a
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.