Inextensional Packaging of Thin Shell Slit Reflectors

Carbon-fibre-reinforced-plastic reflector antennas based on a thin shell that is folded elastically have been recently developed; this paper presents a new concept for packaging reflectors of this type. The idea is to cut the surface into 6-8 petals along curved lines, whose shape is such that in the packaged configuration the petals wrap around a central part. During deployment, they open out and unwrap, driven by the energy stored during folding. Analytical expressions are derived for the stresses induced by inextensional elastic folding of a doubly-curved shell. A simple, approximate method for analysing the packaging scheme is introduced, and its predictions are used to set up an optimization scheme that determines the cutting pattern required to achieve optimal packaging of the reflector, for a given yield stress and elastic modulus of the material. For a dish with diameter of 0.9 m an optimised cutting pattern is determined, and then a detailed finite-element analysis and an experimental verification of the curvatures induced by packaging are carried out. These results confirm that these predictions from the approximate analysis are accurate and conservative. A reduction in diameter of 3 is achieved for this particular dish

Public squares in European city centres

During the latter part of the twentieth century, while a small number of exemplar city centre squares continued to be attractive places, the vast majority acquired either an image of empty spaces or an unattractive picture as traffic islands. This was emphasised by the decline of traditional community activities and the perception of comfort generated by internalising external space; coupled with a commodifying of cities in which they were merely viewed as commercial and retail opportunities. Communities need public spaces as places for assembly. They are the physical manifestation that each community is coherent and vibrant. Increasingly, it is being recognised that identity and place have enormous roles in reinforcing society. The re-introduction of public squares is part of reversing the erosion of the public sector and the public realm, and reclaiming city centres from private interests for the benefit of communities. Criteria for comfortable external spaces have been researched, and these recognise the differences between Northern and Southern Europe. The most recent advances are in the simulation of city centre design; which includes geometry, uses, pedestrian movement and environmental conditions. There is confidence to be gained from visualisation of how squares will look, feel and be used; and will make a real contribution to sustainable urban design