People are sensitive to hypothesis sparsity during category discrimination

Previous work has shown that the information value of requests can be manipulated by controlling the sparsity of hypotheses, the degree to which category members are rare or common in the domain under consideration when making those requests. However, the degree to which people are sensitive to expected information value is unknown. This study examined a binary sorting task where sparsity differed across conditions. In contrast to previous work using hypotheses representable as visual areas, the stimuli in this study defined hypotheses in an abstract similarity space over geometric shapes. Participants could request labels for either category members or non-members. While both request types were used in all conditions, most often evenly, the proportion of participants showing a preference for one type of request was strongly impacted by the information value of that request type. A small tendency to prefer requests from the designated target category was also observed.Steven Langsford, Andrew T. Hendrickson, Amy Perfors, Daniel J. Navarr

Nucleon charge exchange on the deuteron: A critical review

The existing experimental data on the d(n,p)nn and d(p,n)pp cross sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data, allow a direct construction of the np -> np scattering amplitude in the backward direction with few ambiguities.Comment: 7 pages with 3 figure

Report on Technical Committee on Water Needs: NT Missions & Settlements, Position at 30th June 1971.

Made available by the Northern Territory Library via the Publications (Legal Deposit) Act 2004 (NT).Date:1972-0

Feed radiation patterns modified by a dichroic plate

The 20 GHz copolar radiation patterns of a feed 4.25 cm from a flat dichroic plate 15 cm in diameter have been computed using a mode-matching technique. The results are in good agreement with the measured patterns

Cross polarisation of electromagnetic waves transmitted through waveguide dichroic plates

Dichroic or frequency-sensitive surfaces modify the cross-polar performance of feeds transmitting through them. In the paper we investigate the influence of two flat waveguide dichroic plates 1 cm thick and 15 cm in diameter, placed 4 cm in front of a simple, linearly-polarised, choked waveguide feed. Measured cross-polar levels, mainly in the 45° planes, are compared with the levels predicted by a modal analysis in the frequency range 19¿26 GHz. The results agree well. With these particular plates the cross-polar levels over most of the frequency range are lower when the guides are arranged on a close-packed equilateral triangular lattice than when on the more-symmetrical square lattice. Ten wave guide modes are included in the analysis, and their relative importance is discussed. Two cumulative radiation patterns are illustrated, comparing the development of the farfield radiation patterns for the two lattices as the contributions of successive guide modes are summed