Current Issue : April - June Volume : 2016 Issue Number : 2 Articles : 6 Articles
The structural modification of Ba0.5Sr0.5TiO3 (BST) nanocatalyst was successfully synthesized via sol-gel process. The BST\ncatalyst was modified by A-site (A-BST), A-B-site (A-B-BST), and B-site (B-BST) in order to investigate the effect of structurally\nmodified BST catalyst for photocatalytic decolorization of methylene blue. The structurally modified BST catalysts can increase\nthe non radiation energy such as phonon energy compared to that of BST one. The partial incorporation of the A-BST catalyst\nwas evidenced by the higher-ordered structure by increasing number of Ti4+ ions and the lattice oxygen. The A-B-BST and ABST\ncatalysts were given more electron-transfer in the TiO6 than that of BST and B-BST catalysts, respectively. The A-B-BST\ncatalyst promoted the oxidation of the lattice oxygen by holes capturing to form the chemisorbed oxygen, presenting the highest\nphotobleaching activity of methylene blue. On the other hand, more oxygen vacancies recombination of BST catalyst compared to\nthat of structurally modified BST catalysts presented the reduction of photocatalytic activity....
An optical encryption of three-dimensional (3D) object with digital holography was implemented.\nIn the process of encryption, two holograms involved recording key information and 3D object\nwere obtained. In the process of decryption, the 3D object was reconstructed from the two holograms\nby extracting the object and key information, followed by multiplication of the two holograms\nand inverse Fresnel transform numerically. The robustness of the method was also tested\nfor different occlusions attacks and Gaussian noises. The results showed that the method was able\nto encrypt and decrypt the 3D object while being robust under different occlusions attacks and\nGaussian noises....
This paper reviews the work on huge capacity fiber-optic sensing network based on\nultra-weak draw tower gratings developed at the National Engineering Laboratory for Fiber Optic\nSensing Technology (NEL-FOST), Wuhan University of Technology, China. A versatile drawing\ntower grating sensor network based on ultra-weak fiber Bragg gratings (FBGs) is firstly proposed\nand demonstrated. The sensing network is interrogated with time- and wavelength-division\nmultiplexing method, which is very promising for the large-scale sensing network....
Based on the Collins diffraction formula and by means of the expansion of a hard aperture function\ninto a finite sum of complex Gaussian functions, two analytical approaches of the Finite Olver\nbeams (FOBs) passing through a paraxial ABCD optical system with a circular annular aperture or\na rectangular one are developed in this paper. The propagation properties of the FOBs through an\nun apertured ABCD optical system or through this last with a circular (or rectangular) aperture or\na circular (or rectangular) black screen are deduced, from the main results, as particular cases.\nAlso, the characteristics of Finite ordinary Airy beam passing through the all considered optical\nsystems are derived here that correspond to zeroth-order of the FOBs. According to the predicted\nformulas, computer simulation examples are given to deepen the understanding of the characteristics\nof the FOBs passing through some optical systems of annular aperture basis....
A thin optical reflector is often introduced to the backside of the standard mesa type\nlight emitting diode (LED) chip with the aim to enhance its light output. However,\nmost of the reported light output enhancements because of backside reflector (BR)\nintroduction might not be relevant. This is because the reported measurement is\noften from a naked LED chip instead of a packaged LED emitter, and those based\non the packaged emitters employing conventional silver based die attach adhesive\n(DAA). The actual role of BR, which is expected to be greatly influenced by the\npackaging materials and processes, is investigated for the monotonic blue color\nand white LED emitters using Monte-Carlo simulations. Contrary to prior reports, it\nis demonstrated for the first time that the role of BR can be diminished when the\noptically transparent DAA is used and other key packaging materials and processes\nare optimized, i.e., the light output for a packaged emitter with a BR-free chip can be as\nhigh as that of the packaged emitter using the same chip but with an added BR....
A compact portable and standalone point sensor has been developed for the detection and identification of precursors of improvised\nexplosive devices (IEDs) and to be part of a network of sensors for the discovery of hidden bomb factories in homeland security\napplications. The sensor is based on quartz enhanced photoacoustic spectroscopy (QEPAS), and it implements a broadly tunable\nexternal cavity quantum cascade laser source (EC-QCL). It makes use of an optical cell purposely designed with a miniaturized\ninternal volume, to achieve fast response and high sensitivity, and that can also be heated to improve sensitivity towards less volatile\ncompounds. The sensor has been assembled and successfully tested in the lab with several compounds, including IED�s precursors\nsuch as acetone, nitromethane, nitric acid, and hydrogen peroxide. The identification capability and limits of detection near the\nppm level have been estimated for all these compounds....
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