A few-mode fiber (FMF)-embedded long-period fiber grating is proposed as a sensor for simultaneous measurement of refractive index and temperature. Periodically embedding the FMFs induces the local refractive index modulation to achieve a compact sensor size and obtains a low insertion loss. The simulated results show that the two resonance dips have opposite waveguide dispersion coefficients. Therefore, they show different refractive indices and temperature sensitivities in the experiment. At the same time, the spectral characteristics of double-resonance dips provides a condition for simultaneous measurement of two parameters. By monitoring wavelength shift of the two dips, the simultaneous measurement of refractive index and temperature is easily realized.
To analyze the relationship between air quality index (AQI) and housing price, six relationship indexes between air quality index and housing price were calculated using grey spectrum theory, specifically grey association spectrum, grey cospectrum, grey amplitude spectrum, grey phase spectrum, grey lag time length, and grey condense spectrum. Three main change periods were extracted. There was a negative correction between the air quality and the housing price in Handan. The results provide a basis for the government’s measures to prevent haze.
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