3.2.2 Group size Another significant feature of a work group is its size. To be effective it should be neither too large nor too small. As membership increases there is a trade-off between increased collective expertise and decreased involvement and satisfaction of individual members. A very small group may not have the range of skills it requires to function well. The optimum size depends partly on the group's purpose. A group for information sharing or decision making may need to be larger than one for prob
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
2.4.1 Multimode distortion With multimode fibre, the main cause of pulses spreading is the multiple paths that signals can traverse as they travel along the fibre. This phenomenon of multimode distortion is illustrated in Figure 5. 7 Summary This course presents an understanding of ‘ethics’ as something related with ‘good’ and ‘bad’. There are other derivative words like ‘optimal’ that might also be used, and there are parochial words which are related to particular communities. When we talk about ethical things, we are liable to confront cultural differences that are reflected in differences in vocabulary. But there are other kinds of differences too. Things have different properties; for example, ‘appearance†5.10 Conscience Ned responds with the use of another ethical concept. He feels what he is proposing is ‘right’, regardless of any relationships at play, and he refers to his ‘conscience’. This is perhaps a way of saying, firstly, that he feels very strongly that he is right and, secondly, that any speculation about signing away the IP gives him a great deal of discomfort. This appeal to a ‘conscience’ is an interesting rhetorical move because it neither requires nor provides any reasoned justific 5.2 Material comparisons I want to depart from the specific example of the bicycle to make some more general points. In most simple structural analysis the self-weight of the structure is ignored, as it is considered to be small in comparison with the loads carried. However, as an illustration of engineering practice in the search for efficient structures to employ in product design, it is worth examining how the strength and weight of particular materials compare. These comparisons are illustrated throug 5.1 The development of the bicycle Section 4 has looked at how we can follow a logical route or map, from the expression of a need, to arrive at possible solutions to a problem. In Sections 5 and 6 we look in more detail at two quite different examples of engineering problems. Our first example is the historical development of the bicycle frame; the second concerns a vital component of a car's airbag system. The weight of a bicycle frame is a major burden that the cyclist has to bear. There have certainly been times when 4.9 Final implementation The line you take here obviously depends on the problem you set out to solve. If you were creating a new product for retail or industry, then the final step of the process would be to put that product into manufacture and watch it go off into the world to begin its life cycle (Figure 20). If the s 4.3 Possible solutions According to Figure 7, our map of the problem-solving process, once we've defined the problem according to the need the next step is the creative bit – to look for 'possible solutions', Author(s): 3 Needs and problems The last section has established that engineering is about satisfying needs. In fact, with so many needs, it's a wonder that not everyone is an engineer! So, now that we have talked about both needs and problems, the logical progression is to examine the relationship between them. Take the water example as being a fundamental need. We can state it thus: This village needs a supply of clean water. 5.13.2 Circular membrane When a membrane that is stretched over a circular frame is struck, energy is supplied, which again causes the membrane to vibrate in a number of modes simultaneously. The first six modes in which the circular membrane can vibrate are shown in Figure 20. The diagrams comprise circles that are conce 5.5 Vibrating string: pitches of notes produced by stringed instruments When a string is bowed, plucked or struck, energy is supplied that starts the string vibrating. The string doesn't just vibrate in one single mode; instead, it vibrates in a combination of several modes simultaneously. The displacement along the string is the superposition of the standing-wave patterns corresponding to those modes. For example, if the string vibrated only in the first and second modes, the displacement at a given instant of time might appear as shown in Author(s): 5.3 Vibrating string: standing waves on a string We still haven't answered the question of how standing waves are set up on a string. To do so we need to return to our string, fixed at one end and held in someone's hand at the other end. Imagine now that instead of sending a single pulse along the string, the person flicks their hand up and down periodically and sends a sinusoidal wave along the string. This wave gets reflected and inverted at the fixed end and travels back towards the person holding the string. There are now two waves of t 4.7 Summary Water in its 'natural' state supports a complex, yet fragile, ecosystem. The ability of natural watercourses to sustain aquatic life depends on a variety of physical, chemical and biological conditions. Biodegradable compounds, nutrients and dissolved oxygen must be available for the metabolic activities of the algae, fungi, bacteria and protozoa which are at the lowest level of the food chain. In addition, plant and animal growth cannot occur outside narrow ranges of temperature and pH. Susp 4.6 Tidal rivers and estuaries Most of the major cities and harbours in the world are located on estuaries. The estuarine ecosystem is a unique intermediate between the sea, the land and fresh water. A rather precise definition of an estuary is 'a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with fresh water derived from land drainage'. This excludes large bays with little or no freshwater flow, and large brackish seas and inland 3.5.5 Biological indicators A great many biological species and individuals occur in normal streams. These often differ markedly in their sensitivity to environmental factors, and likewise the tolerances of various species to different types of pollution vary considerably. The major groups of organisms that have been used as indicators of environmental pollution include bacteria, fungi, protozoa, algae, higher plants, macroinvertebrates and fish. The benthic 'bottom living' macroinvertebrates are particularly suitable a 2.7 Infiltration Entry of precipitation through the soil surface and on downwards, by gravity, is known as infiltration. The rate at which this process can take place is governed by the permeability (a measure of the ease with which water can flow through the subsurface layer) and by the existing degree of saturation of the soil. Infiltration can be impeded by outcropping impermeable rocks or by paved areas, and also by the presence of finegrained soils with a low permeability (such as clay). At certain times 3.1 The acquisitive model of learning The three models are introduced in turn, and each is followed by an activity that invites you to apply the model to your studies. This model of learning starts from a focus on the observable behaviour of the learner and on the idea that this can be changed by feedback from the learning environment. It is associated with the idea that learning has to do with reproducing some desirable behaviours or measurable outcomes. The learning process is seen as a process of accretion. Learner 3.4.5 Fretting fatigue An additional possibility was considered. It was known that there was significant movement of the bridge during passage of traffic, because users had noticed it many times when crossing. The joints would thus have been subjected to rotary motion around the pin in order to accommodate such vibrations. Could these have caused fatigue crack growth at the bearing surfaces? Contact between a circular and a flat plate creates so-called Hertzian stresses at the contact zone: compressive at the 3.4.1 Fracture surface One half of the eye at the joint is shown in Figure 38(a), and it shows two breaks in the limbs either side of the pin-hole. Although both appear brittle in this picture, in fact one side showed signs of ductile deformation. The way it had fractured was unique when compared with the other eye
