A power conversion apparatus, such as a UPS, includes a first waveform reference signal generator circuit operative to generate a first waveform reference signal responsive to an AC bus, and a second waveform reference signal generator circuit operative to generate a second waveform reference signal, e. 70 gcm3 or less, the microspheres being present in an amount sufficient to lower the first density to about 1. The virtual objects available for targeting are categorized and the categories are correlated to viewing population information to determine the optimum targeting of the virtual objects. computes and transmits to the unit R a plurality of sender’s quantities.