Introduction to Systems Approach

Main aspects of systems theory are outlined. Emphasis is on the interface of between time and systems - natural or artificial

Synchronization and fault-masking in redundant real-time systems

A real time computer may fail because of massive component failures or not responding quickly enough to satisfy real time requirements. An increase in redundancy - a conventional means of improving reliability - can improve the former but can - in some cases - degrade the latter considerably due to the overhead associated with redundancy management, namely the time delay resulting from synchronization and voting/interactive consistency techniques. The implications of synchronization and voting/interactive consistency algorithms in N-modular clusters on reliability are considered. All these studies were carried out in the context of real time applications. As a demonstrative example, we have analyzed results from experiments conducted at the NASA Airlab on the Software Implemented Fault Tolerance (SIFT) computer. This analysis has indeed indicated that in most real time applications, it is better to employ hardware synchronization instead of software synchronization and not allow reconfiguration

Pilot Survey – Queue Management Strategies for Urban Traffic Control Systems

BACKGROUND 1.1 Advances in traffic signal optimization have produced increases in the capacity of urban road networks, but recent growth in demand has meant that many junctions operate at or above saturation levels. Delay costs increase dramatically when queues extend to block upstream junctions and queue management strategies are now required to ensure that local traffic signals operate effectively when oversaturated conditions occur. 1.2 The aims of this SERC-funded "Queue Management Strategies" project are as follows: (a) To generalise the strategies for queue management that were developed and tested empirically in Bangkok (See ITS WP 249 and WP 251); (b) To develop a computer graphics model to represent queue propagation; (c) To test the strategies' applicability and performance in UK networks; (d) To investigate their incorporation into standard signal optimization programs