The Nancay Multifrequency Radioheliograph

The 1024 channel digital correlator receiver of the Gauribidanur radioheliograph

A low frequency (40–150 MHz) radioheliograph for observations of the solar corona is in operation for the last few years at the Gauribidanur radio observatory, about 100 km north of Bangalore. The array has 32 antenna groups and a 1-bit digital correlator system consisting of 1024 channels is used as the back-end receiver. This paper describes the latter and results of the associated system tests.

Perceptual Quality Improvement for Synthesis Imaging of Chinese Spectral Radioheliograph

Chinese Spectral Radioheliography can generate the images of the Sun with good spatial resolutions. It employs the Aperture Synthesis principle to image the Sun with plentiful solar radio activities. However, due to the limitation of the hardware, specifically the limited number of antennas, the recorded signal is extremely sparse in practice, which results in unsatisfied solar radio image qual...

Multifrequency tympanometry in infants

INTRODUCTION  The use of conventional tympanometry is not sufficiently sensitive to detect all cases of middle ear changes, and this hinders accurate diagnosis. OBJECTIVE  To characterize acoustic immittance measures of infants from 0 to 3 months of age using multifrequency tympanometry in a prospective study. METHOD  54 infants from 0 to 3 months of age were evaluated. The inclusion criter...

Multifrequency Ultrasound Radiation

The differential parameter method for multifrequency

Helicopter EM resistivity mapping began to be accepted as a means of geologic mapping in the late 1970s. The data were first displayed as plan maps and images. Some 10 years later, sectional resistivity displays became available using the same ‘‘pseudolayer’’ half-space resistivity algorithm developed by Fraser and the new centroid depth algorithm developed by Sengpiel. Known as Sengpiel resist...