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Missing data imputation is often required in wireless sensor networks (WSNs) to fill up missing measurements due to transmission loss, hardware failure and other factors. In this paper, we propose new variable forgetting factor (VFF) and regularization extensions to the recursive dynamic factor analysis (RDFA) algorithm for imputation of missing data in WSN data. It takes advantage of the correlated...
A liquid refractive index sensor based on a fiber loop mirror (FLM) combined with an etched polarization maintaining fiber (PMF) is proposed. As the etched section of the PMF is immersed in liquid with different refractive indices, the interference spectrum of the FLM presents high sensitivity to the surrounding-medium refractive index. High sensitivity of 25.29 nm/refractive index unit (RIU) and...
In this paper, a novel strain sensor is proposed and demonstrated by employing a modified photonic crystal fiber (PCF)-based Mach–Zehnder interferometer, in which a collapsed region is introduced at the middle point of the PCF to improve the extinction ratio. Experimental results show that this proposed structure has a high sensitivity of 11.22 over a range of 1.28 ...
In the present study, fast response resistive-type PI/multiwall carbon nanotube (MWNT) composite films were demonstrated. A composite film with a loading of 3 wt% MWNTs (PIC30) possesses a very linear response nature, a linearity correlation (R2) of 0.99157 and a sensitivity of 0.00146/%RH. The response time were less than five seconds and the resistance changed synchronously with different humidities...
A novel two-dimensional (2D) clinometer has been demonstrated by attaching two fiber Bragg gratings (FBGs) on a deliberately designed pendulum composed of a tapered cylindrical beam and a mass. Due to the nonuniform tilt-induced strain field applied along the length of the FBGs, the bandwidths of their reflection spectra vary linearly with the applied inclination. By monitoring the reflected optical...
A novel two-dimensional (2-D) accelerometer based on three fiber Bragg gratings (FBGs) has been developed. Both the magnitude and the direction of the acceleration can be detected simultaneously. Preliminary experimental results show that high sensitivity of 1.23 nm/(m??s-2) and resolution of 0.0008 m/s2 have been achieved. Furthermore, it is insensitive to temperature variations.
A novel two-dimensional tilt sensor is demonstrated by using four fiber Bragg gratings (FBGs) interacting with a cylindrical cantilever-based pendulum. Preliminary results show that tilt accuracy of 0.4° and resolution of 0.013° can be easily achieved in a large measurement range from −40° to 40°, with no temperature dependence.
A novel two-dimensional (2-D) tilt sensor based on three optical fiber Bragg gratings (FBGs) is proposed and demonstrated. Preliminary experiments show that a high measurement sensitivity of 64 pm/° and resolution of 0.016° can be achieved and this sensor is insensitive to temperature.
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