Papers by Author: Yi Wang

Abstract: Nanocrystalline Al₂O₃-ZrO₂ powders were prepared through controlled crystallization of amorphous phase, and kinetic studies on crystallization and grain growth were carried out. Based on Kissinger equation, the activation energies for crystallization were determined to be 981.8 kJ·mol^-1 for (Zr_0.94Y_0.06)O_1.88 and 1364.1 kJ·mol^-1 for α-Al₂O₃. Average size of crystallite was obtained by Scherrer equation according to FWHMs in XRD peaks; the grain growth was slow below 1100°C, and turned severe at higher temperatures. The appropriate calcination temperatures was determined to be 1100°C, at which stable phases were formed and further severe grain growth can be restrained. SEM micrograph of Al₂O₃-ZrO₂ powder after calcination at 1100°C revealed uniform distribution of spherical particles with size of about 20 nm, close to that determined by XRD results.

Abstract: The corresponding discharge waveforms were detected by ultrasonic sensor. The dimension of feature vectors extracted from discharge waveforms were reduced by local linear embedding algorithm. The processed vectors were used as input to train and test BP_Adaboost classifier. Recognition results show that, high voltage reactor insulating defects recognition with this method can reduce the calculation and maintain a high recognition rate at the same time. This shows its effectiveness in the application of partial discharge pattern recognition.