A USB plug with a multi-directional rotation structure, adopted for a portable electronic device, is used for mating with an electronic product having a USB port. The method may further comprise a step of ceramic hydroxyapatite chromatography prior to the hydrophobic chromatography. The invention is also directed to an alkaline battery. The composition for a photoreactive organic polymer gate insulating layer has a photochemical characteristic that enables micropatterning, and can be formed into a layer having excellent chemical resistance, thermal resistance, surface characteristics and electrical characteristics. The actual logic to determine access permissions need not be part of the interceptor. The method is implemented in real time by performing a cross-correlation between pairs of average power signals originating from pairs of beamformers.