Relation between radar detection and the observer's concept of a target.

An experiment tested the hypothesis that target detectability on a PPI radar display depends on O's knowledge of the attributes defining a target. Equal numbers of O's were given either a brightness, a form, or a combined brightness-form set during training. A 4th group was given only demonstration training. The criterion test involved detection of 2 target sizes in 2 levels of visual noise for 3 target speeds. Analysis of variance revealed an interaction between set and noise level, confirming the hypothesis for the high noise level only. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A corona-stabilised plasma closing switch

Corona-stabilised plasma closing switches, filled with electronegative gases such as SF6 and air, have been used in pulsed-power applications as repetitive switching devices for the last 10 years. Their high repetition-rate capabilities coupled with their relatively simple design and construction have made them suitable alternatives to thyratrons and semi-conductor switches. As well as having repetitive switching capabilities, coronastabilised plasma closing switches have the potential to operate at elevated voltages through the incorporation of multiple electrode sets. This allows high-voltage operation with inherent voltage grading between the electrodes. A further feature of such switches is that they can have relatively low jitter under triggered condition. This paper reports on some of the operational features of a new design of corona-stabilised, cascade switch that utilises air as the insulating gas. At pressures between 0 and 1 bar gauge the switch has be shown to operate over the voltage range of 40 to 100 kV with a jitter below 2 ns.