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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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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions) and is used under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.

Grateful acknowledgement is made to the following sources:

Text

Cas
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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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5.6 Filtration

In filtration, the partially treated water is passed through a medium such as sand or anthracite, which acts as a ‘strainer’, retaining the fine organic and inorganic material and allowing clean water through. The action of filters is complex and in some types of filter biological action also takes place. Sand filters are used in water treatment to remove the fine particles which cannot be economically removed by sedimentation. They have been effective in removing Cryptosporidium,
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1.7 Conclusions

Could both of these students have got more from their involvement with the course if they had taken time to reflect on their goals and their strengths and weaknesses, especially at the beginning of study? Alan, whose reaction to the course was positive, for example, could have learned more about how the course succeeded if he had reflected rather more in the beginning about his initial scepticism and his preference for communicating verbally rather than in writing. What was the reason for his
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1.2 Learning beyond course study

Learning how to learn has become an important goal in higher education. There is a national context in which an emphasis on ability to learn has come to prominence. It is now widely asserted that an ability to learn is as important an outcome of university study as knowledge of a discipline. This is a view put forward strongly by employers, for example, who have an interest in the employability of graduates and the skills they bring into the work place. It is a view which has been reiterated
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1.1 Effective course study

Research into how people study effectively suggests that it is important to pay attention not only to the content of what we are trying to learn but also to the process of our learning. Time spent on the process of how you are learning need not be a distraction from achieving your learning goals. It should support your efforts to achieve them.

However, thinking about the process of your own learning is not something which typically forms part of most formal courses of study. Most people
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1 Learning to learn

(Please refer to Reading 1, Learning and reflection, by Mary Thorpe)This unit is about developing your effectiveness as a learner. For example, there are activities which invite you to apply theories to practice and also to criticise theories in the light of practical experience. In these and other ways you will be encouraged to bring your own experience into the study of the unit. The idea of asking you to use ideas, not just to remember them, and to bring your own experience into studying,
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Learning outcomes

After completing this unit you should be able to:

  • assess your learning styles and capabilities, using a learning file in which to record your progress;

  • describe the main definitions of learning as a process, and the role played by memorising, understanding and doing;

  • explain the three main categories of theories about learning, namely the acquisitive, constructivist and experiential models of learning;

  • discuss the main conceptions of
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Introduction

This unit is from our archive and it is an adapted extract from Systems thinking: principles and practice (T205) which is no longer in presentation. If you wish to study formally at the Open University, you may wish to explore the courses we offer in this curriculum area.

This unit has been written because it is al
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The content acknowledged below is Proprietary (see terms and conditions) and is used under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.

Grateful acknowledgement is made to the following sources for permission to reproduce material within this book:


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3.7 Aftermath

In the immediate aftermath of the disaster, it was vital to prevent any further collapses, especially on bridges of similar design. Two other bridges were built to a design similar to that of the Silver Bridge, one upstream at St Mary's, West Virginia and the other in Brazil at Florianopolis. The bridge upstream on the Ohio river, at St Mary's, was the focus of concern, and it was closed to traffic immediately after the disaster. The eye-bar design was actually quite widespread in other bridg
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3.6 Failure sequence

Following the discovery of the broken eye bar near the top of the northern suspension chain on the Ohio side of the bridge (Figure 36), it was possible to reconstruct the sequence of events during the collapse.

When the side chain separated, the entire structure was destabilised, simply b
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3.5 Design of the bridge

The design of the original structure was governed by applicable standards in 1926. The official inquiry found that the design and build fell within those limits, the most important being the allowable stress in the eye-bar chain of 345 MPa. The steel was to be made with a maximum elastic limit of 520 MPa, with a safety factor on the strength of the steel of 2.75. It was argued at the time that over 70 per cent of the load was from the self-weight of the structure. Other suspension bridges of
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3.4.6 Residual stress

One factor that can cause serious problems in any material is the presence of residual tensile stress. The problem often arises as a direct result of manufacturing, when hot material is shaped and then allowed to cool to ambient temperatures. For large castings like those needed to make the eye bars, such residual stress would be modified by the subsequent heat treatment to strengthen the steel, but had to be studied as part of the research effort into the catastrophic failure of the bridge.<
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3.4.4 Stress concentration at joint

Although it is known that a round hole in a flat sample will theoretically produce a stress concentration of about 3, the issue was decided experimentally. A tensile test at 25 °C was undertaken on an intact eye-bar-pin assembly from the bridge, being some 8 m long and from a lower part of the chain. It yielded at about 7 MN, and fractured in the shank at a stress of about 770 MPa. The yield stress in the shank was about 520 MPa, and the failed eye bar showed ductile behaviour with a reducti
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3.4.3 Simulated environmental tests

The investigators wanted to know about the fatigue properties of the component, to find a feasible explanation of why it took 39 years for the eye bar to break. They needed information on the several stress corrosion mechanisms that were possible in the material, including hydrogen embrittlement, the effects of sulphur compounds such as H2S (hydrogen sulphide) and the effects of moisture and salt. Notched eye-bar material was loaded to failure in various environments.

In fact
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