The use of a polymer fiber as a refractive index sensor is proposed. A fiber Bragg grating is inscribed near the fiber tip and the fiber is cut shorter thus creating a Fabry-Perot cavity. The reflections between the fiber Bragg grating and the fiber end-face create a Fabry-Perot interferometer. The sensor was characterized to refractive index changes at constant temperature and to temperature at constant refractive index using a fast Fourier transform analysis of the interference signal. The sensor revealed a sensitivity of −1. 94 RIU −1 with a resolution of 1×10 RIU −3 and low sensitivity to temperature, with a cross sensitivity to temperature of 3. 6×10 RIU/°C −4 .
power divider incorporating k/4 transformers is properly designed to feed the array elements. The elements of the array are spaced at a distance of 0.8k 0 from each other in both x-and y-directions.ABSTRACT: A new microstructured optical fiber is presented as a sensor of acetone evaporation. Sensing is performed by observing the time response of the reflected signal at 1550 nm when the device is dipped in acetone or a 50% acetone-50% water mixture. The sensor consists on a caterpillar-like microstructured fiber spliced to a single-mode fiber, where the spliced end of the sensor has a transversal microfluidic channel etched using focused ion beam. Upon heating, different behaviors are visible between the dipping and the evaporation of acetone. The sensor is able to track the evaporation of acetone and to distinguish between pure acetone and a 50% acetone-50% water mixture. The sensor is also able to detect when the acetone in a mixture with water is fully evaporated. The detection of water vapor with no particular orientation of the sensor is achieved due to the presence of the microfluidic channels.ABSTRACT: This article presents a thorough investigation of the use of shorting posts to widen the bandwidth and coupling coefficient range of a patch quadrature coupler. The lumped equivalent circuit is used to analyze the characteristics of two proposed shorting posts loaded patch configurations. It is shown that by loading shorting post on the center of a patch, the bandwidth of coupler with loose coupling can be significantly improved. The patch configuration with four shoring posts is also proposed to provide a loose coupling coefficient up to 15 dB, which cannot be achieved using the conventional configuration. For demonstration purposes, two quadrature couplers were designed to exhibit 10 and 15 dB coupling coefficients with bandwidths of 29% and 19.2%, respectively. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:683-688, 2016; View this article online at wileyonlinelibrary.com.
In this work, X-ray fluorescence (XRF) and Laser-induced breakdown spectroscopy (LIBS) analyses were applied to samples of quartz, montebrasite, and turquoise hydrothermal veins in the Argemela Tin Mine (Central Portugal). Montebrasite (LiAl(PO4)(OH,F)) is potentially the main ore mineral; with its alteration, lithium (Li) can disseminate into other minerals. A hand sample was cut and analyzed by XRF and LIBS for several elements of interest including Cu, P, Al, Si, and Li. Although XRF cannot measure Li, results from its analysis are effective for distinguishing turquoise from montebrasite. LIBS analysis complemented this study, making it possible to conclude that turquoise does not contain any significant Li in its structure. The difference in spot size between the techniques (5 mm vs. 300 µm for XRF and LIBS, respectively) resulted in a poorer performance by XRF in accurately identifying mixed minerals. A thin section was petrographically characterized and mapped using LIBS. The mapping results demonstrate the possibility of the successful identification of minerals and their alterations on a thin section. The results of XRF analysis and LIBS mapping in petrographic sections demonstrate the efficacy of these methods as tools for element and mineral identification, which can be important in exploration and mining phases, complementing more traditional techniques.
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