To measure the concentration of CH4, we developed a thin film piezoelectric acoustic sensor (TFPAS), it accomplishes the detection of CH4 by the absorption of CH4 which can change the oscillation frequency of the piezoelectric crystal. The sensor is mainly composed by the piezoelectric film, sensitive film, silicon substrate and electrodes. The sensitive film is made up of nanometer-sized MgO scattered on pitch-based activated carbon fibers which has a strong adsorption of CH4. The piezoelectric film is a ZnO film which has very high piezoelectric characteristic parameters. The experimental results show that the sensitivity of the sensor to CH4 is very high. The response of the sensor to the presence of CH4 tested was found to be linear within a certain detection range and the detection error is less than 5%.
Based on RFID and WSN, this paper designs a wireless attendance system. This system is mainly used for the corporate sector attendance.It can be able to overcome the problems such as error-prone and complicated wiring of existing attendance system. This system mainly includes RF information collection module, wireless transmission module, wireless receiver module and attendance information processing system. Multi-zone RF card information can be collected to send, receive and deal with so that this system can achieve the function of multi-sectoral attendance.
A tellurite photonic crystal fiber (PCF) sensor structure is proposed for simultaneous measurements of the methane and hydrogen. The structure is a simple hexagonal three-cladding structure, and six air holes in the inner cladding are coated with methane-sensitive film and hydrogen-sensitive film respectively. Based on the degenerate four-wave mixing (DFWM) theory, the direct relationship between the wavelength shifts of Stokes spectrum or anti-Stokes spectrum and the variations of gas concentration can be established to realize the accurate detection of gas concentration. The influences of pump wavelength and gas-sensitive film thickness on the gas sensitivity are investigated, and the maximum sensitivity of methane and hydrogen after parameter optimization are -2.052nm/% and -0.236nm/%, respectively. The linearity of the fitting can reach up to 99.95%, and the low detection limit of methane is 450ppm and hydrogen is 2500ppm. The sensing method based on four-wave mixing in non-silica photonic crystal fiber also can be extended to other detections of gas-mixture in the mid-infrared field.
A piezoelectric sensor array is introduced for the analysis of gas in mine. This sensor array is made of three different gas-sensitive piezoelectric sensors to detect an explosive gas mixture of methane, butane and hexane. The gas analysis is very important to reliable warning of explosion risk in mine. Because of cross sensing to gas for each sensor of sensor array, we use BP neural network in the artificial neural networks to process the sensing signal to get the concentration of methane, butane and hexane in the combustible gas mixture. Experimental results show that the analysis error is less than 5% and meets the requirements of safety monitoring.
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.