Thin-walled aerospace structures can be idealised as dimensionally reduced shell models. These models can be analysed in a fraction of the time required for a full 3D model yet still provide remarkably accurate results. The disadvantages of this approach are the time taken to derive the idealised model, though this is offset by the ease and rapidity of design optimisation with respect to parameters such as shell thickness, and the fact that the stresses in the local 3D details can not be resolved.A process for automatically creating a mixed dimensional idealisation of a component from its CAD model is outlined in this paper. It utilises information contained in the CAD feature tree to locate the sketches associated with suitable features in the model. Suitable features are those created by carrying out dimensional addition operations on 2D sketches, in particular sweeping the sketch along a line to create an extruded solid, or revolving the sketch around an axis to create an axisymetric solid. Geometric proximity information provided by the 2D Medial Axis Transform is used to determine slender regions in the sketch suitable for dimensional reduction. The slender regions in the sketch are used to create sheet bodies representing the thin regions of the component, into which local 3D solid models of complex details are embedded. Analyses of the resulting models provide accurate results in a fraction of the run time required for the 3D model analysis.Also discussed is a web service implementation of the process which automatically dimensionally reduces 2D planar sketches in the STEP format.

Processing geometric models for finite element analysis is a major factor in the time required to develop and optimise a design. Efficient analysis may require simplification of the geometric model by dimensional reduction (replacing thin sheets or slender bars of material with equivalent line or surface elements) or detail suppression (the removal of small features below the scale of interest in the analysis). There are many situations where detailed local models of full dimension could be combined with global models containing reduced dimensional elements, or in which the abstract models used in preliminary design could be used to generate an initial version of the 3D solid model. Furthermore, the most appropriate representation of an object is dependent on the analysis type. These requirements provide significant challenges for future generations of CAE software in feature recognition and the modelling and representation of geometric objects.

This paper applies the use of parallelism in program design to the subject of data processing problems. It describes how parallelism is used as a tool in program design, showing the techniques involved and proceeding step by step through various stages from the initial design to a final implementation. This is illustrated by considering a particular data processing application.

Abstract It has been our experience that, when writing software for operating systems, the synchronization techniques available in Communicating Sequential Processes are inconveniently primitive. In this paper we investigate how different types of queue can be represented in C.S.P., and we show how this approach can be developed into a general queuing mechanism.

Abstract This brief paper describes the considerations behind the design and use of a programming language and editor for use by children of primary school age.

This paper demonstrates how the notation of Communicating Sequential Processes may be used in the design of an operating system.It goes further to show how such an approach assists in the design and development of a system distributed over a network of computers.The technique uses a welldefined design methodology.

Abstract This paper describes the development of a program to solve the Henderson and Snowdon ‘Telegrams Problem’, the program being expressed as a set of communicating sequential processes (Hoare7).