5.3.3 Contingency theories Contingency theories are based on the idea that there is no single best style of leadership but that the most effective style depends upon the circumstances. The aspects of the circumstances identified as significant are: the leader's characteristics and style (thus absorbing the two earlier theories). the subordinates' expectations and experience. the nature of the task and the organisational environment.
2.3.2 The project (single) team The project, or single, team consists of a group of people who come together as a distinct organisational unit in order to work on a project or projects. The team is often led by a project manager, though self-managing and self-organising arrangements are also found. Quite often, a team that has been successful on one project will stay together to work on subsequent projects. This is particularly common where an organisation engages repeatedly in projects of a broadly similar nature – for e
2.1 What is a group? Our tendency to form groups is a pervasive aspect of organisational life. As well as formal groups, committees and teams, there are informal groups, cliques and cabals. Formal groups are used to organise and distribute work, pool information, devise plans, coordinate activities, increase commitment, negotiate, resolve conflicts and conduct inquests. Group working allows the pooling of people's individual skills and knowledge, and helps compensate for individual deficiencies. It has been
Learning outcomes After completing this unit you should be able to: describe the main features of work groups and teams; discuss the main group processes that affect work group or team effectiveness; describe the main features of projects, project teams and project management; discuss some types of theories about effective leadership.
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7 Summary Polymers are long chain molecules with properties dominated by their chain behaviour and the nature of their chemical make-up or constitution. The distinction between thermoplastics and thermosets has become rather blurred with the development of new materials for more demanding environments than previously. They include high performance polymers which are more resistant to high temperatures, possess greater moduli or strengths, and can be combined with additives to enhance their intrinsic pr
6.5 Market experience It is some 20 years since the Topper project was conceived by Peter Bean, Technical Director of Rolinx and Ian Proctor, the designer of the original GRP boat. Sales initially were excellent, especially to sailing schools and clubs where there was much demand for a small, light and very safe sailing boat for children. But after that, the market became saturated, sales were heavily dependant on individuals and families, so decreased despite attempts to export the boat to the USA and Israel, for
6.4 Case history: the Topper boat Replacement of one polymeric material by another may be undertaken entirely for manufacturing reasons, and this is what happened in the redesign of the Topper dinghy for thermoplastic polymer. The dinghy was originally designed for hand lay-up GRP in 1969 by Ian Proctor, a well known designer of small boats and yachts (Figure 61
6.1 A fresh approach? Polymeric materials offer substantial benefits over conventional materials in terms of their low density, relative freedom from corrosion, transparency or translucency, and a range of physical properties which cannot be achieved with metals, glasses or ceramics. Such unique properties include low coefficients of friction (e.g. PTFE), resistance to extreme environments (e.g. PTFE, silicones) as well as the ability to absorb and modulate damaging vibrations (e.g. most rubbery polymers). It is t
5.6.3 Conformation and crystallinity If there are key connections between the chain configuration and crystallisation, you might also expect some more subtle effects from rotation about chain bonds. After all, polymer chains must be able to twist into the regular conformation demanded for crystal structures (Figure 57(a)). And what influence will rotation have on
5.5.2 Molecular orientation As polymers are processed and shaped by flowing into moulds the shear stress fields induce preferred orientations in the molecules. The hydrostatic components of the stress field cause packing. These orientation and packing effects will relax with time if the temperatures are high enough, but the moulding cycle is frequently such that they are ‘frozen-in’ by cooling or perhaps fixed into the structure because the material has been crosslinked. The consequent moulded-in or residual stresse
5.3 Viscoelasticity and master curves An immediate consequence of the viscoelasticity of polymers is that their deformations under stress are time dependent. If the imposed mechanical stress is held constant then the resultant strain will increase with time, i.e. the polymer creeps. If a constant deformation is imposed then the induced stress will relax with time (stress relaxation). Author(s):
4.6.2 Material costs in manufacturing For high added-value products like boats and cars, material costs form a relatively small proportion of total costs. For directly manufactured products, however, which are sold without much assembly or finishing, material costs do form a relatively large proportion of the total production cost. This applies particularly to polymeric containers for foods and drinks but not, for example, to containers for more sophisticated products like electronic or electrical goods. What is much more importa
4.4 Step growth polymerization 4.3.5 Co-ordination polymerization While most free radical and ionic polymerizations are carried out homogeneously, there is another important class of reaction which is often performed with solid catalysts. These reactions, discovered in the mid-fifties, have revolutionized polymer manufacture by permitting much less severe polymerization conditions than with other systems and by allowing a greater degree of control of polymer structure. Ziegler-Natta catalysts, as they are called, will convert vinyl and diene monomers 3.3.3 Higher aromatics Benzene rings can be fused in various ways to create component parts for some of the complex aromatic repeat units shown in Table 5. One of the most important is bisphenol A, made by fusing two phenol rings with acetone:
References Appendix 2 Acronyms 4.6 Conclusion to Section 4 This brief account has introduced a few of the most rapidly developing areas of optical-fibre communications as of January 2004. By the time you are reading it things will certainly have moved on, and if you want to find the current state of the art you should read journals such as IEEE Communications Magazine or trade magazines such as Lightwave. It is also possible to find out more on the world wide web. I hope you will agree that this is a fascinating field, and that yo 4.3 Optical networking DWDM improves the utilisation of optical fibre for point-to-point links, but a further step in exploiting the potential of optical fibre comes from optical networking in which routeing or switching is done optically. Optical networking is in its infancy, but the concept of the optical layer based upon wavelength channels is emerging. The optical layer effectively sits below the SDH layer in the network, and provides wavelength channels from one location to another. An analogy can
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APC angle-polished convex (connector) ASE amplified spontaneous emission ASK amplitude shift keying cw continuous wave DSF dispersion-shifted fibre DWDM dense wavelength division multiplexing EDFA erbium-doped fi
