We have measured the low-temperature transport properties of a high-mobility front-gated GaAs/Al 0.33 Ga 0.67 As heterostructure. By changing the applied gate voltage, we can vary the amount of disorder within the system. At a Landau level filling factor ν = 1/2, where the system can be described by the composite fermion picture, we observe a crossover from metallic to insulating behaviour as t...

Electrical insulation is an important part of all electrical systems. The level of insulation safety provided by an insulator depends on the amount of leakage current flowing on its surface. Actually increased leakage current causes a part of high voltage to appear at dead end of insulator. This voltage may sometimes be of order of 1000 to 5000 Volts depending upon weather conditions. Such a le...

The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We discuss a non-Fermi liquid gapless metallic surface state of the topological band insulator. It has an odd number of gapless Dirac fermions coupled to a noncompact Uð1Þ gauge field. This can be viewed as a vortex dual to the conventional Dirac fermion surface state. This sur...

One of the important factors influencing outdoor insulators performance is pollution phenomenon. The pollution, especially during humidity condition, reduces superficial resistance of insulator and lead to a flow of Leakage Currents (LC) on the insulator surface, which may result in total flashover. The LC characteristics are affected by parameters such as nature and severity of pollution. Loca...

Two large electric utilities, located on the US West Coast, use a considerable number of composite insulators on their power transmission lines. Some of these insulators may be prone to premature insulation degradation caused by poor design, manufacturing defects, pollution or construction mishandling, or gunshot vandalism. This may result in flashover and power outages, unless the state of the...

A composite material of a polyethylene matrix filled by a fine silver powder was prepared with different Ag contents and physical behaviours ranging from insulator to conductor. Ac differential magnetic susceptibility χ measurements show the samples are paramagnetic up to an Ag concentration of ∼65%. At low temperatures the composite is spin-glass type, whereas the transition from insulator to ...

A comprehensive review of the giant Hall effect (GHE) is presented, with emphasis on novel experimental data obtained in Ni–SiO2 and Co–SiO2 films prepared by co-sputtering. GHE is observed close to and on both sides of the metal–insulator transition. From the point of view of microscopic conduction mechanisms, this means a crossover from metallic conductivity with weak localization to tunnelin...

The detection of composite insulator defects in substations still relies on manual inspection. In this paper, we propose a method for crack shape features by improving the RCNN convolution kernel. can meet premise insufficient training sample data, but also get better CNN effect, and finally achieve accurate recognition. phase, RGB three-channel decomposition is used to expand data set; median ...