RESUMEN
Polypropylene (PP) has gained attention in the industry as an environmentally friendly material. However, its electrical properties are compromised due to space charge accumulation during operation, limiting its application in high-voltage DC cable insulation. This study investigates the effect and mechanism of SiO2 with a DDS surface hydrophobic treatment on space charge suppression and the electrical properties of PP composites. The PP matrix was doped with SiO2 nanostructures, both with a DDS surface hydrophobic treatment and untreated as a control group. The functional group structure and dispersion of nanostructured SiO2 in the matrix were characterized. The findings reveal that the incorporation of SiO2 nanostructures effectively mitigates charge accumulation in PP composites. However, a high concentration of unsurfaced nanostructures tends to agglomerate, resulting in inadequate space charge suppression and a diminished DC breakdown field strength. Nonetheless, surface treatment improves the dispersion of SiO2 within the matrix. Notably, the composite containing 1.0 wt% of surface hydrophobic SiO2 exhibits the least space charge accumulation. Compared to the base material PP, the average charge density is reduced by 83.9% after the 1800 s short-circuit discharges. Moreover, its DC breakdown field strength reaches 3.45 × 108 V/m, surpassing pure PP by 19.4% and untreated SiO2/PP composites of the same proportion by 24.0%.
RESUMEN
PURPOSE: To investigate the value of anteroposterior-to-transverse ratio (ATR) and the effect on features of nodules in ultrasound (US) diagnosis of thyroid nodules in different locations. Methods: The nodules were divided into three groups according to the different nodule location: isthmus group; upper and lower poles of bilobed thyroid group; and the middle of the bilobed thyroid group. The diameters of the nodules were recorded, and ATR of the nodule was calculated on the transverse and longitudinal sections. The transverse and the longitudinal sections of ATR of thyroid nodules in different groups were compared. Result: The transverse section of ATR was significantly different among the three groups (p = 0.001). In addition, there are significant differences in many US features among three groups, including nodule composition, thyroid parenchyma, morphology, echogenicity, shape, calcifications, vascularity, nodule ACR TI-RADS and histopathologic (all p < 0.05). In the group of upper and lower poles of bilobed thyroid, significant difference was found between the transverse and the longitudinal section of ATR (p = 0.019). The cut-off values of transverse section and longitudinal section of ATR were 0.967 and 0.750, respectively. Conclusion: The transverse section of ATR at different location of thyroid may be a predictor for malignancy with clinical diagnostic significance.