Nuclear density and distribution ratio of abandoned cropland in the study area.

Nuclear density and distribution ratio of abandoned cropland in the study area.</p

Estimation results of impact factor model for cropland abandonment in the study area.

Estimation results of impact factor model for cropland abandonment in the study area.</p

Spatial distribution map of abandoned farmland in the study area.

Spatial distribution map of abandoned farmland in the study area.</p

Variable rotation component matrix.

Variable rotation component matrix.</p

Sample points and box diagram of cultivated plots and non-cultivated plots.

Sample points and box diagram of cultivated plots and non-cultivated plots.</p

Factors influencing cropland abandonment at the plot scale.

Factors influencing cropland abandonment at the plot scale.</p

Statistical table of the characteristics of abandoned cropland.

Statistical table of the characteristics of abandoned cropland.</p

A map showing the geographical location of the study area.

A map showing the geographical location of the study area.</p

NDVI time series variation curves of cultivated land and abandoned land.

NDVI time series variation curves of cultivated land and abandoned land.</p

Fluorinated Barium Titanate Nanoparticles for Wearable Piezoelectric Power Generation

In this paper, to improve the compatibility of poly­(vinylidene difluoride) (PVDF) with barium titanate (BaTiO3) and the piezoelectric property of wearable piezoelectric nanogenerators (PENGs), fluorinated BaTiO3 (F-BaTiO3) nanoparticles were prepared by the simple thermal annealing of BaTiO3 prepolymer with PVDF powder, a modified composite nanofiber was prepared by electrospinning with a dispersed liquid consisting of F-BaTiO3 nanoparticles and PVDF solution, and a PENG was prepared with the modified composite nanofiber as a piezoelectric functional material. Scanning electron microscopy (SEM) showed that F-BaTiO3 nanoparticles were more uniformly dispersed in the modified composite nanofiber than BaTiO3 nanoparticles, the analysis of Fourier infrared (FT-IR) spectroscopy showed that the β-phase content of the modified composite nanofiber compounded with F-BaTiO3 (F-BaTiO3/PVDF nanofiber) was higher than that of the modified composite nanofiber compounded with BaTiO3 (BaTiO3/PVDF nanofiber), and when the dosage of F-BaTiO3 nanoparticles was 5 wt %, the β-phase content of the modified composite nanofiber reached the maximum value (91%), which was about three times that of BaTiO3/PVDF nanofiber. The output voltage of the PENG could reach as high as 1.5 V under an external force of 2N and does not decrease obviously after 300 cycles in a vertical pressing test. Furthermore, PENG was demonstrated to be sensitive to the detection of human motions, for instance, elbow flexion, hand slapping a table, and walking. These results indicated that by BaTiO3 being fluorinated with PVDF, the dispersity of F-BaTiO3 in PVDF nanofiber, the β-phase content of F-BaTiO3/PVDF nanofiber, and the output voltage of F-BaTiO3/PVDF PENG were improved