Electro-optic (EO) polymers, possessing high EO coefficient and low dielectric constant, are considered to be a new generation of nonlinear optical materials that have great application prospect in photo-communication, information storage, and data processing. The host-guest structure of EO polymers is the most typical one in this field. However, the phase separation during polarization between the host polymer and the guest nonlinear optical molecule (NLO) limits potential applications of the material. To solve the problem, a new synthetic method was designed in this paper. First, 2,4-dinitroaniline was grafted to phenol polyphosphazene by chemical method for polar improvement of the main chain. Then, another small NLO molecule was mixed into the polymer by physical method for further improvement of EO coefficient. The preparation process was studied and the structure of the product was characterized. The effects of different NLO mixing proportions and different polarizing temperatures on EO coefficient were investigated in details. Orientation stability of the sample was tested. Experimental results show that our products possess not only high EO coefficient but also good phase stability, which makes them good candidates for the application in information technology.
An Ms7.0 earthquake occurred in Jiuzhaigou, Sichuan Province, China, on August 8, 2017. In this study, we used the vertical component data from 31 seismic stations near the epicenter from May 1 to August 20, 2017, to calculate the amplitude spectrum hourly using the fast Fourier transform method. Furthermore, the spectral area of the low frequency band (0.02–1 Hz), which represents the energy of low frequency motion, was calculated. In this way, the temporal and spatial variations in the vertical ground motion in this region were determined. Four high-value processes occurred in mid-June, mid-July, late July, and early August (the last three are discussed in this article). Based on a comparison with the local meteorological data, the meteorological factors had no influence, local geological factors did not affect the results, and typhoon factors did not show obvious correlation. Combined with the results of previous studies, we believe that the increase in the spectral area reflects the intense movement of deep material in the region related to the Jiuzhaigou earthquake. The spatial distribution of the spectral area (energy) reveals that the deep material moved eastward rapidly, was obstructed by the Sichuan Basin, and expanded to the northwest in a U-shaped channel, which may be the main dynamic factor for the formation or triggering of the earthquake.