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3.1 Modelling properties

This section provides a model for properties interpreted in terms of the average thermal energy of all the constituent atoms of a material. Since absolute temperature T is a measure of average atomic kinetic energy, we shall expect to be looking at properties that change gradually with T, roughly proportionally, over a wide range. In terms of the classification introduced in Author(s): The Open University

2.3 How things change with temperature

The temperature-dependent effects used in most thermometers have a fairly steady change over a good range of temperature (Figure 3a). By contrast, phase changes, of which melting and boiling are the common examples, happen at sharply critical temperatures (Author(s): The Open University

Stage 5: Formulating measures of performance (how will we know when we have arrived?)

The hard systems approach emphasises the need to have measurable means of assessing the efficacy of any potential solution or design, but recognizes that this may not always be possible.


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5.7 Being ethical

As outlined in Table 2, ethics within systemic practice are perceived as operating on multiple levels. Like the systems concept of hierarchy, what we perceive to be good at one level might be bad at another. Because an epistemological position must be chosen, rather than taken as a given, the cho
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5.5 Distinctions about systems practice

A tension has existed throughout the history of Western thought around whether to focus on parts or the whole. The practice that springs from this history carries the same tension. This tension has been particularly visible within science and philosophy for a long time and it gives rise to different approaches.

Emphasizing the parts has been called mechanistic, reductionist or atomistic. An emphasis on the whole has been called holistic, organismic or ecological. As Fritjof Capra (1996)
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3.6.1 Stiffness

Just how compliant does an AFM cantilever have to be to enable it to follow the undulations in a surface on an atomic scale? How can we find out? It turns out that this is easier than at first it seems.

A simple assumption we can make is that the compliance of the cantilever should be appreciably greater than that of a typical bond that holds atoms to one another. Here's one way in which a rough estimate of the stiffness (the force required to cause a given deflection) of the bonds in a
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2.1 Introduction

One aspect of micro and nano scale engineering that distinguishes it from many other forms of manufacturing is the way it involves building both the devices themselves and the very materials from which they are made, in one place and at more or less the same time. In general, MEMS are made from thin layers of new material produced, and then shaped in some way, on the surface of a silicon wafer. The devices contain several different materials, and have a three-dimensional structu
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Conclusion

We have seen how a solution falls into one of three categories (innovation by context, innovation by development, and routine solution) according to the need that drives it. Furthermore, the need is shown to be the point of reference that should be kept in sight throughout the process of finding solutions. Unless the need is accurately stated, the ideal solution cannot be obtained – a case of 'garbage in, garbage out'.

We have examined the process of finding a solution step by step, u
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7.3 Ethics and safety

A practising engineer makes ethical decisions, with moral and physical implications of varying magnitudes, on a daily basis. Examples of ethical dilemmas are limitless, ranging from the engineer who takes home the odd pen, file or discarded paper 'for the children', to the engineer who signs off a project without checking the details and identifying a simple arithmetic error of magnitude. The implications of either may be negligible – such as where the cost is more than compensated in unpai
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4.8 Assess and review again

If you've been following the stages of our problem-solving map, then the chances are you're ahead of me here (Figure 19). Yes, if it works, hurrah; if it doesn't then off we go again, all the way back to 'possible solutions' and selecting the best of the rest. Or maybe even going back to the beginning. No one wil
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4.6 Assess and review

Following our problem-solving map, we have reached the stage of 'assess and review solution', Figure 16.

Figur</span><br><span class=Author(s): The Open University

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4.2 From a need to a problem

So, working from the top down, the process starts with 'need' and 'problem'; see Figure 8.

Although we usually work by identifying a need that converts to a problem, that requires a solution, don't forget the extra arrow at the side, taking this first part of the process full circle. The questions that draw
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4.1 Advancing knowledge

Over the centuries, engineers have faced and solved a huge number of problems of one sort or another. Each time a problem is solved, knowledge is advanced, something usually gets written down, and so today we have a wealth of experience to draw on. Equally, problem-solving techniques have also been developed and evolved through use and refinement, which is rather handy. Not only do we have some idea of existing solutions to similar problems, but we also have an indication of how to go
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1.1 Solving problems

It could be said that our species is defined by its irresistible urge to solve problems – it's what makes us human. Strange, then, that the word 'problem' has such negative overtones. I think that the root of this paradox is that the word is used both when we identify a need – the first link in the problem-solving chain – and when we undertake the process of meeting that need. It is the identification of the need and the realisation that it is real and must be met that creates the anxie
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5.15 Further investigation is possible

There are still many mysteries that surround the Tay Bridge disaster, largely because so little was recorded at the time of construction. For instance, questions remain about the details of reject rates for the castings, and modifications made to the first designs of the piers and their component parts.

Although enlargement of the BoT set of pictures has helped clarify the various failure modes described by Henry Law and others at the enquiry, it has also revealed yet more mysteries. Wh
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5.12 Pole and Stewart report

Apparently prepared using the same methodology as Law, Pole and Stewart produced a report that calculated the loads at various points in the bridge under live locomotive loads and wind loading at various pressures. Stewart was employed by Bouch to perform the original design calculations for the bridge, while Pole was brought in as an independent expert. He had extensive experience of use of different materials in bridges, and indeed, had written a standard text book for engineers on the subj
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5.10 Bridge stability

Any fracture of the diagonal wind brace tie bars could allow substantial lateral movement at the top of the piers. If these tie bars had already been injured by the previous train to cross the bridge, it would have only taken a little extra effort to complete the process as the mail train arrived over each pier supporting the high girders. Once the wind braces had failed completely, and the struts fractured at their connections each pier would behave as two separate supporting structures.


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5.5 Evidence of Henry Law

Henry Law's report is brief and to the point, and includes a substantial appendix giving detailed calculations of the effects of wind pressure on the structure (not included in Paper 1). Further information on his inspection of the remains – the two standing piers, the twelve wrecked piers the high girders and the train within – was given during his testimony before the enquiry.

Law was able to examine the extant remains in considerable detail, and noticed numerous defects in the br
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4.5 Photographs showing the detail: broken lugs

The bases of the columns to which they were attached originally on pier 3 deserve closer inspection. Even at this scale, the two fractured lugs where the tie bars were formerly fixed are clearly visible at the right-hand and left-hand sides of Figure 28 (arrowed). The southern (left-hand) column base in
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4.3 Photographs showing the detail: collapsed piers

Figures 23 and 24 present the east- and west-facing views of a collapsed pier, pier 5, which lay just ahead of the train be
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