4.7 Summary Human activity has been responsible for some extinctions and othe deleterious changes to habitats. These changes have not always been the result of thoughtless or selfish behaviour; often intentions were worthy, but outcomes were not as predicted. The importance of genetic diversith is demonstrated here in relation to Dutch Elm disease. The need to retain genetic diversity in plants, used for food and medicine, is recognized in such initiatives as the Kew Milennium Seed Bank Appeal.
Learning outcomes After studying this unit you should be able to: understand how the world is in the process of ‘being made’, right down to the earth beneath our feet; consider how islands are shaped by a dynamic relationship between territories and flows; show how human life is entangled with non-human forces and processes in the making of today's globalised world.
1.1Aim The aim of this section is to practise the use of diagramming techniques as part of a fundamental shift in interpreting issues – from an assembly of static objects to a network of dynamic relationships.
4.2.3 The significance of the distribution of energies Near room temperature (300 K), the average bundle of thermal energy associated with a particle is 0.026 eV (look back at Box 2 Temperature and energy). This is not going to do much damage to something stuck together with bonds that have an energy of a few eV – just as the average wage earne
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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
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
6.3.1 Prototyping The first prototypes may be made of any convenient material, such as clay, plaster-of-Paris or wood. Plastic models can also be made by fabrication or vacuum forming of thin sheet. Their primary function is to ensure that the product has ‘customer appeal’ when considered in aesthetic or ergonomic terms. This is particularly important for products which are to be consumer durables. It may be the first time in the design process that the concept sketches and initial engineering drawings are
6.3 Materials selection Good design fulfils the product specification under the required service conditions as well as contributing to the cost effectiveness of its manufacture and maintenance. The product specification itself must be an interpretation of the market needs. Hence good design means giving product appeal at the point of sale. Selecting the polymer is just one stage in this design exercise, both in terms of information on various properties of materials, as well as the detailed evaluation and selection
3.2.2 Ethane cracking Although ethane can be cracked thermally, the reaction is slow and does not necessarily yield ethylene at high severity. Careful control of reaction conditions, however, allows the reaction to occur The yield of ethylene is typically nearly 50 wt% with the rest composed o
Stage 6: Developing the options (what would the options be like?) The objective here is to develop the routes to objectives generated in Stage 4 to the position where they could be implemented if the decision to go ahead were given. This involves doing sufficient work on each option for technical and other details to be defined, and for costs and benefits to be assessed, and for a sound decision to be taken, while at the same time minimising the time and resources devoted to the task.
2.2 A modern view Modern attempts to define engineering recognise the importance of the resources identified by Sage, and that the subject can be divided into two components: engineering knowledge – the ‘know-what’, and engineering process – the ‘know-how’. Engineering knowledge is: […] the growing body of facts, experience and skills in science, engineering and technology disciplines; coupled to an understanding of th 4.4.1 FTTCab, FTTC, FTTB and hybrid coaxial fibre The equipment needed at optical-fibre transmitters and receivers (lasers, photodiodes and the associated electronics) is more expensive than the equivalent for transmission over copper cables. With FTTH this equipment is needed in every home, and a substantial cost reduction is possible with schemes where the fibre doesn't go all the way to the home, but stops short, and copper links run from a shared fibre to several homes (Author(s): 3.1 Introduction The basic optical-fibre link consisted of the source (laser or LED), the fibre and the detector, as was shown in Figure 1. Improvements in these components can increase the data rate, but the system is still a point-to-point transmission link and all signal processing, such as routeing 2.3 Attenuation At approximately what wavelength is the attenuation of optical fibre lowest? What, approximately, is the attenuation at that wavelength? What other wavelengths are used and why? 6.5 Appreciating some implications for practice I think for most people, the National Health Service would be experienced as a complex situation. If so this would be a good example of perceived complexity. Remember though, if you engaged with it as if it were a difficulty you would not describe the situation as one of perceived complexity. I could not call it a complex system unless I had tried to make sense of it using systems thinking and found, or formulated, a system of interest within it. This means I would have to have a stake in the 7.2.3 Chemical composition As outlined in Table 2, some deposition techniques are best suited to conducting materials, whereas others come into their own only for chemical compounds. In either case, chemical composition may be an important consideration. Impurities can interfere with the conduction properties of the material (notably in t 6.6 Oscillators in general Although this section has dealt only with mass-spring systems, the analysis can be extended to any system where there is an oscillating driving force acting on a mass which is located by a restoring force. In fact, the analysis is even more general than this and can be applied to electronic networks where voltages and currents oscillate in much the same way as the mass on the spring. 4.2 The piezoelectric effect at the atomic scale It has been mentioned above that by changing the state of polarisation of a piezoelectric material we can generate movement, and vice versa. Let's examine a little more deeply what is meant by ‘state of polarisation’ and how we can maximise its effect to get the best out of electrically controlled micro-actuators. In order to electrically polarise a material we need, by definition, to cause a separation of charges within the material. The more we can do this the greater the d
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