Planning the Restoration of an Open-cast Coal Site

This paper describes an operational research approach to planning the restoration of an open-cast coal site.No established operational research technique exactly fitted the problem, which was one of planning a large-scale earth-moving operation, where the quantities to be moved were not specified, but had to be planned to conform with stringent restrictions on gradients, continuity, drainage and total volume. A numerical technique was developed, used in conjunction with the dual solutions of successive transportation programmes to reach progressively an optimum solution.The nature of the problem allowed an unusually clear-cut comparison to be made between the previous conventional plan and the operational-research-based plan; the latter showed considerable savings and was put into practice.There would appear to be many other situations where the approach could be applied.     

Reflection of plane waves from the boundary of a pre-stressed compressible elastic half-space

The effect of pre-stress on the propagation and reflection ofplane waves in an incompressible isotropic elastic half-spacehas been examined recently by the authors (Ogden & Sotiropoulos,1997). In the present paper the corresponding analysis for compressiblematerials is detailed. In the two-dimensional context consideredfor incompressible materials the (homogeneous) plane waves werenecessarily shear waves. By contrast, in the compressible contextpure shear waves can propagate only in specific directions inthe considered principal plane and, in a general direction,a quasi-shear wave may be accompanied by a quasi-longitudinalwave, as is the case in the anisotropic linear theory. The dependenceof the (in-plane) slowness section on the pre-stress (and finitedeformation) and on the choice of constitutive law is elucidated.This information is used to determine the reflection coefficientsfor reflection of either a (quasi-) shear wave or a (quasi-)longitudinal wave from the boundary of the half-space and tocharacterize the different cases which arise depending on thegeometry of the slowness section. The theoretical results are illustrated by numerical calculationsfor the range of possible types of behaviour with referenceforms of strain-energy function and different states of finitedeformation and to the question of stability of the half-space.     

A Hospital Throughput Model in the Context of Long Waiting Lists

In a public health system, one of the problems is the size of the waiting list for admission to hospital. This research involves establishing a method of analysing the general surgery waiting list problem at hospital and district level. While there are many aspects to such a study, this paper concentrates on a linear programming model to plan the aggregate throughput of the general surgical department. Preliminary results from applying the techniques to actual health districts in the United Kingdom are reported.