The effects of surface traps on surface flashover remain controversial. To clarify the relation between surface flashover and surface trap level, in this work, the surface trap level of epoxy composites was modified by nanoparticles incorporation, electron beam irradiation, and ozone treatment. Surface trap characteristics were analyzed by surface potential decay. Surface flashover voltages were measured in a vacuum for dc voltage and in SF 6 for ac voltage. The ''U-shaped'' curve is founded to describe the relation between surface flashover voltage and surface deep trap level, surface flashover voltage first decreases and then increases with surface deep trap level. Enhancement of surface flashover voltage is attributed to reduced surface charge density, which was calculated by a double-trap flashover model. The simulation results indicate that the surface charge density on left side of ''U-shaped'' curve is controlled by surface shallow traps, whereas that on the right side is determined by surface deep traps. The effects of surface shallow and deep traps on surface charge accumulation and dissipation are used to demonstrate the reduced surface charges and improved surface flashover voltage for the ''U-shaped'' curve. The proposed ''U-shaped'' curve offers a promising way to improve surface flashover performance for high-voltage applications by tailoring surface trap characteristics with surface modifications. INDEX TERMS Surface flashover, surface trap level, surface charge, epoxy composites.

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To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity (EA) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite.

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The present study was designed to determine the fungal post-harvest pathogens of peach from fruit markets of Dhok kala khan, Raja Bazaar and Mandi Mor located in Rawalpindi, Pakistan. During the year 2016-17, 36 fruits from were collected randomly and morphological characterization of fungal isolates confirmed that Botrytis cineria, Aspergillus niger, Rhizopus stolinifer and M. piriformis are causing post-harvest rot of peach. Among all these, R. stolinifer was found to be most prevalent pathogen. The essential oil of brassica, taramira and ginger were used for management of R. stolinifer with 0.05%, 0.5% and 5% concentration. Taramira oil at 5% concentration resisted the growth of R. stolinifer after 3 and 5 days while only 0.1 mm growth was recorded after 7 days.