5.4 Expert evidence: an overview

The second part of the enquiry was devoted to analysis of the disaster. There were three engineers appointed: Mr Henry Law for the enquiry, and Dr William Pole and Mr Allan Stewart acting on behalf of the NBR. In addition, Mr Law collected samples of columnar material and wrought iron straps, bolts and struts for mechanical testing, as well as many broken parts to be shown as exhibits at the enquiry. He asked Mr David Kirkaldy to test the samples using a hydraulically operated tensometer.

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Video Materials

This video extract is from Coast Se
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Module team

T356 course team

Academic staff

Dr Alec Goodyear (course chair)

Professor Nicholas Braithwaite

Jan Kowal

Dr Tony Nixon

Dr Sally Organ

Robin Harding (critical reader)

James McLannahan (critical reader)

Dr Martin Rist (critical reader)

Dr George Weidmann (critical reader)

Peta Jellis (course manager)

External assessor

P
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5.13.1 Rectangular bar

If a solid rectangular bar is excited by striking it, energy is supplied that starts the bar vibrating transversely. The bar will vibrate in a number of modes simultaneously since the striking action supplies energy over a range of frequencies. The motion of the bar will be the superposition of the standing-wave patterns of the excited modes.

Assume for the moment that the rectangular bar is supported in such a way that both ends are free to vibrate and the effects of the supports can b
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10.3 The decibel as a measure of sound amplitude

As I mentioned earlier, because a decibel is a way of expressing a ratio, it cannot by itself express the absolute size of anything. To express absolute values it must be referred to a fixed reference quantity, against which whatever is being measured can be compared. In the context of acoustics the reference used is the lower limit of audibility – the threshold of audibility. This varies from person to person, but has a nominal value that can be expressed as a pressure wave with an
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10.1 Introduction

For a variety of reasons, not least the very wide dynamic range of human hearing, the decibel (symbol dB) is often used as a unit for the amplitude of sound waves. The decibel is also used in other contexts, such as specifying the amplification of amplifiers or the degree to which a signal is affected by noise. In the context of sound, the use of the decibel as a unit captures something of the subjective impression of the way loudness changes with amplitude.

The decibel unit has
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6.1 Defining amplitude

Another important property of a sine wave we need to be able to specify is its amplitude. In essence, the amplitude of a sine wave is its size. Unfortunately there are various ways of defining what is meant by the size of a sine wave, and you are likely to come across many of them in material you look at outside this unit. Before I explain what our definition is, it will help matters if we look at what is meant by the average value of a sine wave.

Figure 16 shows a sinusoidally a
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1.3 Describing sound

Let's now take a closer look at my list of categories from Activity 3, starting with item (a). In each of my descriptions of this sort, I referred to the source–cause of the sound: that is, an object or an instrument (the source of the sound) and ways of using it to produce a sou
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7.2.4 Trap 4: words and wordiness

I have seen some effective rich pictures with lots of words in them but they are quite rare in my experience. More often, lots of words make the rich picture less rich. Part of the later use of a rich picture might include looking for patterns. Words inhibit your ability to spot patterns.

If you do use speech bubbles, use what people say, not your interpretation, unless the bubble is about some general attitude. Examples might be ‘Aaagh!’, ‘Help!’, ‘Oops!’ – the sort of th
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2 Part 1 Starting the unit

Welcome to T306_2 Managing complexity: a systems approach – introduction. As I write, I experience a sense of excitement. For me, as for you, this is the beginning of the unit. These are the first few sentences I'm writing and so, although I have a good idea of how the unit is going to turn out, the details are by no means clear. Nevertheless, the excitement and anticipation I, and maybe you, are experiencing now is an important ingredient in what will become our experiences of the u
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13 Part 2: 4 Preparing for innovation

Many inventors have said that having the idea for an invention is the easy part. This is often demonstrated by the frequency of examples of simultaneous invention. At one exhibition of inventions I attended there were three separate portable ladders to escape from fires, two systems for using rainwater to flush toilets, two types of portable vehicle wheel clamp, and two methods of reducing red-eye in flash photography. In most cases of technological innovation only one of the competing techno
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10.5 Desire to help others

This is a less common motivation but it shows not everyone is driven by money.

In 1991 the inventor Trevor Baylis saw a BBC documentary about the spread of HIV/AIDS in Africa. What was needed was a way of broadcasting the safe-sex message to people in areas without electricity and where batteries for a radio could cost a month's wages. Solar power wouldn't necessarily help as most people who could get to a radio listened in the evening after work. While absorbing this information he ima
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9 Part 2: Invention

Having taken a broad look at the whole innovation process from invention to diffusion, I'll go back and look more closely at what motivates individuals and organisations to invent. Then I'll consider how people generate ideas for inventions and the designs based on the inventions.

4.4 What was innovative about the telephone?

The most obvious innovative aspect was that speech was being transmitted, so in principle anyone could use a telephone for communication. The use of the telegraph required skilled operatives. A message had to be translated into the dots and dashes of Morse code and transmitted using a single keypad making and breaking the connection in an electrical circuit. At the other end of the wire another Morse operator translated the received clicks into the words of the message. With the telephone no
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1.2.2 Visualisers and verbalisers

A major point about diagrams is that some people naturally relate well to them and use them frequently, while others tend to prefer textual material. The former are sometimes referred to as visualisers and the latter as verbalisers. There is nothing wrong with either of these tendencies, but in subjects like systems thinking, social science or technology, where text and diagrams support each other, it is important to be comfortable with both. In addition, it is helpful to rememb
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1.1.3 Features of diagrams

As there is variety in the types of diagrams we can see and use we need to think more broadly about what diagrams are trying to represent. One distinction which follows on from the discussion above is:

• Analogue representations: these diagrams look similar to the object or objects they portray. At their simplest they are photographs of real objects and at their most complicated they are colourful, fully labelled drawings of the inner workings o
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Text

Case Study 2: Inclusive power tools,
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4 Who are the users?

This section reveals that ‘users’ can include a wide variety of people – not just the final purchasers or consumers of a product. The section also makes the case for strong user representation in the design process.

Of course, it is not only me who uses the various products in my home; other people use them as well, both members of the family and visitors. Sometimes the range of users of a product, and their different needs, can be diverse. And in addition to the obvious or intend
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5.8.1 Nitrate removal

Nitrate in water has become a significant problem and the EU Directive sets a maximum admissible concentration of 50 g m⁻³ measured as NO₃⁻. This is equivalent to 11.3 g m⁻³ as N. High nitrate levels can cause cyanosis or methaemoglobinaemia in babies. Legislation allows the designation of nitrate-vulnerable zones and these help to prevent nitrate levels in natural waters increasing in affected areas.

Ion exchange is used in some
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