Effect of plasma step gradient modification on surface electrical properties of epoxy resin

In this paper,plasma fluorination is combined with plasma silicon deposition to achieve step gradient modification on an epoxy resin surface.The physicochemical characteristics of samples are investigated and the electrical performances measured.The obtained results show that compared with untreated and single treated samples,the samples treated by step gradient modification significantly improve the flashover performance.According to experiment and simulation,the mechanism explanations are summarized as follows.First,it is found that the step gradient conductivity can effectively optimize the electric field distribution of a needle-needle electrode.Then,step gradient modification suppresses the accumulation of surface charge at the triple junction and makes the charge distribution more uniform.Furthermore,it can accelerate the surface dissipation on a high electrical field region and control the dissipation rate on a low electrical field region.All these results can restrain surface discharge and increase the flashover voltage.The step gradient modification method proposed in this paper provides a new idea for improving the surface insulation performance.

Watershed segmentation based on hierarchical multi-scale modification of morphological gradient

Watershed segmentation is sensitive to noises and irregular details within the image,which frequently leads to a serious over-segmentation Linear filtering before watershed segmentation can reduce over-segmentation to some extent,however,it often causes the position offset of object contours.For the purpose of reducing over-segmentation to preserve the location of object contours,the watershed segmentation based on the hierarchical multi-scale modification of morphological gradient is proposed.Firstly,multi-scale morphological filtering was employed to smooth the original image.Then,the gradient image was divided into multi-levels by the volume of three-dimension topographic relief,where the lower gradient layers were further modifiedby morphological closing with larger-sized structuring-elements,and the higher layers with the smaller one.In this way,most local minimums caused by irregular details and noises can be removed,while region contour positions corresponding to the target area were largely preserved.Finally,morphological watershed algorithm was employed to implement segmentation on the modified gradient image.The experimental results show that the proposed method can greatly reduce the over-segmentation of the watershed and avoid the position offset of the object contours.