Multi-microprocessor control of processes with pure time delay

In 1967 a novel scheme was proposed for controlling processes with large pure time delay (Fellgett et al, 1967) and some of the constituent parts of the scheme were investigated (Swann, 1970; Atkinson et al, 1973). At that time the available computational facilities were inadequate for the scheme to be implemented practically, but with the advent of modern microcomputers the scheme becomes feasible. This paper describes recent work (Mitchell, 1987) in implementing the scheme in a new multi-microprocessor configuration and shows the improved performance it provides compared with conventional three-term controllers.

Minimising the latency induced by consistency control, within a large scale multi-user distributed virtual reality system

Where users are interacting in a distributed virtual environment, the actions of each user must be observed by peers with sufficient consistency and within a limited delay so as not to be detrimental to the interaction. The consistency control issue may be split into three parts: update control; consistent enactment and evolution of events; and causal consistency. The delay in the presentation of events, termed latency, is primarily dependent on the network propagation delay and the consistency control algorithms. The latency induced by the consistency control algorithm, in particular causal ordering, is proportional to the number of participants. This paper describes how the effect of network delays may be reduced and introduces a scalable solution that provides sufficient consistency control while minimising its effect on latency. The principles described have been developed at Reading over the past five years. Similar principles are now emerging in the simulation community through the HLA standard. This paper attempts to validate the suggested principles within the schema of distributed simulation and virtual environments and to compare and contrast with those described by the HLA definition documents.

Planning delay and the responsiveness of English housing supply

There is growing international interest in the impact of regulatory controls on the supply of housing. Most research focuses on the supply impacts of prescribed limits on land use but housing supply may also be affected by the process of planning monitoring and approval but this is hard to measure in detail. The UK has a particularly restrictive planning regime and a detailed and uncertain process of development control linked to it, but does offer the opportunity of detailed site-based investigation of planning delay. This paper presents the findings of empirical research on the time taken to gain planning permission for selected recent major housing projects in southern England. The scale of delay found was far greater than is indicated by average official data measuring the extent to which local authorities meet planning delay targets. Hedonic modelling indicated that there is considerable variation in the time it takes local authorities to process planning applications. Housing association developments are processed more quickly than those of large developers and small sites appear to be particularly time-intensive. These results suggest that delays in development control may be a significant contributory factor to the low responsiveness of UK housing supply to upturns in market activity.