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Electronic linear-scanning ultrasonic diagnostic equipment so far has suffered from low resolution. In the study presented here, improvement in resolution was obtained by electronic focusing and improved image quality by small-angle deflection. Electronic focusing is a method obtaining a narrow ultrasonic beam by means of phase control. Small-angle deflection is a method to increase scanning line density by deflecting slightly the ultrasonic beam also by means of phase control and thus to obtain information existing between the successive scanning lines of a conventional linear scanning system. Both experimental investigation and clinical application have shown that these techniques are highly effective in increasing lateral resolution and image quality. It has been confirmed that the equipment is practical for routine use.

A new spectoscope recording continuously the amplitude-frequency spectrum of VLF atmspherics has been developed. The receiver sweeps the frequency giving complete coverage of the band of 5-70kc/s repeatedly and the output is displayed on an intensity modulated cathode-ray tube, which is photographed on a slowly moving film.Observations have been carried out and it appears that the result provides an excellent experimental base for the mode theory of VLF ionospheric propagation. It is found that the frequency-spectrum of distant atmospherics shows a broad intensity maximum around 10kc/s and decreases its intensity towards higher frequencies with undulating peaks. Marked selective absorption bands appeared in the spectrum are variable according to the time of day, and they might be assoiated with cut-off frequencies of the waveguide bounded by the earth and the ionosphere. The solar flare effect on VLF atmospherics propagation is also revealed, which indicates a sudden shift of the spectrum to higher frequencies owing to the increase of ionization and the lowering of a reflecting height of the ionosphere.