The refractive index profile of germanium doped preforms for optical fibers is determined by the radial distribution of germanium concentration. Knowing that there is a correlation between the germanium doping profile and the deposition surface profile of vapor-phase axial deposition (VAD) preforms, the study of this correlation has been carried out in order to estimate, indirectly, the refractive index profile of VAD preforms for optical fibers during the deposition stage. This correlation was studied through the parameterization of the preform deposition surface using two parameters: the power law index profile that best fits the preform bottom profile (α) and the axial distance from the bottom tip to a reference height (h). A range of values of these parameters to produce VAD preforms with standard and special doping profiles has been presented. Preforms with triangular index profile can be fabricated with α and h values of about 2.0 and 5.0 mm, respectively, and preforms with parabolic index profiles can be produced with α and h values of about 2.0 and 4.0 mm, respectively.
Small-angle X-ray scattering was employed to investigate heterogeneities in growth sectors of a large Z-bar synthetic quartz. The measurements were performed in as-grown and heat-treated samples. As a result, X-ray scattering was observed in all samples. The Guinier approximation revealed a polydispersive distribution of heterogeneities in as-grown samples with a radius of gyration ranging from 80 to 250 Å. Infrared spectroscopy and X-ray fluorescence analysis were used to elucidate the nature of these heterogeneities. Considerable variations in the intensity of scattered X-rays due to heat treatments were only noticed in growth sectors with high OH-content. The results suggest that tiny aggregates of molecular water are the main reason for the scattering patterns observed in the range 0.006 < q < 0.1 Å -1 .
Bioethanol is produced by bio-chemical process that converts sugar or biomass feedstock into ethanol. After bio-chemical process, the solution is distilled under controlled conditions of pressure and temperature, in order to obtain an ethanol-water solution. However, the ethanol concentration analysis is generally performed off-line and, sometimes, a re-distillation process becomes necessary. In this research, an optical apparatus based on Fresnel reflection has been used in combination with artificial neural networks for determination of bioethanol concentration in hydro-alcoholic solution at any temperature. The volumetric concentration and temperature effect was investigated. This intelligent system can effectively detect and update in real-time the correction of distillation parameters to reduce losses of bioethanol and also to improve the quality in a production plant.
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.