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In this work, various nano-sized samples of Y₂O₃, Y₂O₃:Eu and Y₂O₃:Eu, Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y₂ O₃:Eu phosphor was enhanced while crystallite size was decreased.

In this paper, we present an efficient and simple shadow detection algorithm for indoor environments, as well as give a brief description on the advantages of this method. In this method, we use three types of approaches: image enhancement, chromaticity consistency, and gradient features. Multiple shadow direction is becoming an increasingly challenging task for many moving shadow detection algorithms because some objects have large self-shadows. Our system is able to achieve good performance solving spread shadow problems in indoor scenes, leading to improved foreground segmentation in surveillance scenarios. The image enhancement approach is first employed to input images to generate high-quality images for artificial light source indoor areas. Afterwards, the chromaticity information is utilized to create a mask of possible candidate shadow pixels. Subsequently, gradient features are applied to remove foreground pixels that have been incorrectly included in the mask. In comparison with existing algorithms, the proposed method can correctly detect and remove shadow pixels to identify original foreground shapes without distortion for delivering object recognition and tracking tasks.

Y₂O₃:Eu nanopowders were synthesized by urea combustion method containing different concentration of Eu. The synthesized Y₂O₃:Eu nanopowders were characterized by X-ray diffractometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy dispersive X-ray analysis (EDX) and photoluminescence spectroscopy (PL). The particle size was calculated to be in the range of 15–30 nm using Scherrer's formula. The Ia-3 structure of synthesized Y₂O₃:Eu nanopowders were confirmed with X-ray diffractometry. The crystallinity of Y₂O₃:Eu nanopowders were confirmed by SAED and TEM images. The ⁵D₀–∑⁷F_J (J = 0, 1, 2, 3) and ⁵D₁–⁷F₁ transitions bands were observed at 575–650 and 530–550 ranges in the photoluminescence spectrum. The concentration quenching was estimated to be about 5 mol% of Eu. The best chromaticity to the standard red color was observed with the sample containing 3 mol% of Eu.

This paper describes the design of a 5.5:1 bandwidth feed antenna and reflector system, intended for use in hydrogen intensity mapping experiments. The system is optimized to reduce systematic effects that can arise in these experiments from scattering within the feed/reflector and cross-coupling between antennas. The proposed feed is an ultra-wideband Vivaldi style design and was optimized to have a smooth frequency response, high gain, and minimal shadowing of the reflector dish. This feed can optionally include absorptive elements which reduce systematics but degrade sensitivity. The proposed reflector is a deep parabolic dish with $f/d=0.216$ along with an elliptical collar to provide additional shielding. The procedure for optimizing these design choices is described.