Monolithic broadband GaAs f.e.t. amplifiers

A unique monolithic X-band f.e.t. amplifier is described. Wideband matching circuits, using lumped elements, are integrated with the transistor on semi-insulating gallium arsenide to produce an amplifier chip 1.8×1.2 mm. Gains in excess of 4.5 dB over 7.5 to 11.5 GHz have been measured. The chip has been installed into a low-parasitic package to produce a gain module suitable for the microwave engineer.     

Application of feedback techniques to the realisation of hybrid and monolithic broadband low-noise-and-power GaAs FET amplifiers

The implementation of ultrabroadband low-noise GaAs FET amplifiers operating up to 20 GHz is shown to be possible with the use of a low-parasitic high-gm device, which can only be implemented using monolithic circuit techniques. An example of a 0.1 to 6 GHz hybrid low-noise amplifier to illustrate the circuit technique is described.     

Design data for interdigital directional couplers

The letter presents graphical information relating the performance of interdigital microstrip directional couplers to the geometrical parameters of the circuit. The theoretical background is summarised, and a comparison is made with reported experimental results.     

Workplace exposure to rosin-based solder flux fume during hand soldering

The patterns and extent of exposure to rosin based solder flux fume have been investigated in two surveys and a number of individual site visits carried out by the UK Health and Safety Executive (HSE). Determination of solder fume was by measurement of airborne resin acid particulate. Both static and personal sampling was carried out over time periods ranging from 15 minutes to several hours. Resin acid concentrations were found to vary from less than 1 microgram m-3 to 2289 micrograms m-3. The effects of various types of local exhaust ventilation on resin acid concentrations have been observed. On-tool tip extraction systems were generally found to be the best control measure available; however good design, positioning and system maintenance is essential for efficient capture of the fume. The resin acid concentrations detected at these twenty-six sites suggest that the proposed British long and short term occupational exposure limits are realistically attainable targets, particularly where good working practices and/or effective fume control measures are in place.     

Distributing Operational Support to Transform Business Operations

Operational support is increasingly a key differentiator for telecommunications operators. It is an essential part of launching and delivering telecommunications services. However, the quickening pace of new product and service launches, together with increasing customer expectations and changes in commercial structures for service delivery, all highlight the need for more imaginative ways of providing operational support. This paper describes some innovative work at BT to introduce collaborative working into the end-to-end processes of operational support, between supplier and customer. It has applied the principles of community of interest networks (running over extranets) to back-office processing in the carrier business, between operators. Distributed systems principles and technologies underpin the technical design, and business benefits are available to all the organisations using it.     

Situated learning with co-operative agent simulations in team training

The paper describes pedagogic aspects of the theory, design, analysis techniques used and implementation experience acquired during the development of a team training simulation system with a virtual reality interface for learning from emergencies. In particular we demonstrate: the desirability of team training strategies; the value of using training scenarios for constructing shared mental models with intelligent agents, and the use of a virtual reality interface. We present a tool designed and developed to reify the communication acts of team members that demonstrates support for reflective learning. An evaluation tests the acceptability of the simulation and provides feedback from an observation study. The paper then shares some of the emergent questions raised through the project particularly those relating to the management of errors, the fidelity of simulations for training and communications between agents, and the organisational context of integration.