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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
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4.6.2 Material costs in manufacturing

For high added-value products like boats and cars, material costs form a relatively small proportion of total costs. For directly manufactured products, however, which are sold without much assembly or finishing, material costs do form a relatively large proportion of the total production cost. This applies particularly to polymeric containers for foods and drinks but not, for example, to containers for more sophisticated products like electronic or electrical goods. What is much more importa
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3.3.3 Higher aromatics

Benzene rings can be fused in various ways to create component parts for some of the complex aromatic repeat units shown in Table 5. One of the most important is bisphenol A, made by fusing two phenol rings with acetone:

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Introduction

Polymers are materials composed of long molecular chains that are well-accepted for a wide variety of applications. This unit explores these materials in terms of their chemical composition, associated properties and processes of manufacture from petrochemicals. The unit also shows a range of products in which polymers are used and explains why they are chosen in preference to many conventional materials.

This unit is from our archive and it is an adapted extract from Design and ma
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Learning outcomes

After working through these materials you should be able to:

  • describe and use a general classification of models;

  • outline and discuss the process of systems modelling, where models are used as part of a systemic approach to a range of different situations;

  • recognise that systems models may be used in different ways as part of a process for: improving understanding of a situation; identifying problems or formulating opportunities; supporting decision
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Introduction

Maps and plans, architects‗ and engineers‗ drawings, graphs and tables: all are models we use in everyday life. This unit will introduce you to the modelling process enabling you to recognise that systems models may be used in different ways as part of a process for: improving understanding of a situation; identifying problems or formulating opportunities and supporting decision making.

This unit is from our archive and is an adapted extract from a course which is no longer taught b
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Acknowledgements

The following material is Proprietary and is used under licence:

Text

Various pages: Arup, O., material accessed in January 2002 and December 2000, from.

Box 1: Inman, P. ‘Chaotic scheme that left families relying on food parcels’, The Guardian, 6 July 2005. © Guardian News and Media Ltd 2005.

Box 2: ‘Fly-away drones put robot air force plans off cou
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6 Summary

This unit has covered the background to systems engineering. It began by addressing the question ‘Why is systems engineering important?’ Two reasons were discussed:

  • projects go wrong, and the increasing incorporation of software means that they go wrong more often now than in the past

  • complication, complexity and risk are all increasing and need to be managed.

In the second section I examined the development of en
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5.3 The systems engineering methodology used in the course

The aim of systems engineering is to achieve a solution that is effective and sustainable through its life cycle, together with the associated processes and facilities needed to realise the system and introduce it into the real world. Therefore it is important that systems engineering is itself conducted in full consideration of the following five systems:

  • the technology development system that provides new or modified technology for the other systems
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5.1 Introduction: the general framework

The general framework of systems engineering adopted in the course consists of: a hierarchy of elements; aims associated within its outputs and process; a set of principles; a division into technical and managerial components of the process.

The lexicon of system engineering used in the course contains the hierarchy of elements:

  • strategy: meaning the accumulated decisions concerning the areas in which an organisation operates and its lon
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4.3 The use of systems engineering in organisations

The development of systems engineering was contemporaneous with that of systems analysis in public policy. Though its origins can be traced back to the 1930s and 1940s (Hall, 1962, p. 7), its more widespread application can be dated from the early 1950s. The earliest formal teaching of systems engineering was a course presented in 1950 at the Massachusetts Institute of Technology by G.W. Gilman, who was then Director of Systems Engineering at Bell Laboratories. Gilman was a strong promoter of
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4.2 The use of systems analysis in public policy

The application of mathematical techniques to military operations was pioneered in Britain during the Second World War (see Box 7) and became known by a variety of names (Hoos, 1972, p. 42). At the end of the war, the United States Air Force sponsored the application of those techniques and methods to problems of US national security. Funds to investigate the effects of new weapons systems and for the exploration of defence policy issues were allocated to defence contractors. From one of thes
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Stage 7: Implement changes

Finally, the agreed changes are implemented.

Like the hard systems approach, soft systems methodology is not seen as a ‘one pass’ procedure, but as a learning process. Iteration is a feature of the methodology's application. Learning is achieved in both approaches by the use of models, although soft systems has subsequently been enhanced to include a specific analysis of the culture and politics of the problem situation, as shown in Author(s): The Open University

Stage 6: Debate on feasible and desirable changes

The comparison undertaken in the previous stage can have two results.

  • It can cause opinions to change on the problem situation and the issues arising from it.

  • It can provide an agenda for change.

In either case (though both may result), the objective of this stage is to debate, with all concerned, the changes proposed to ensure that they are both desirable and feasible. The aim is to arrive at consensus about the prop
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Stage 2: The situation analysed

The first step is to develop a picture (called in soft systems terminology a rich picture) that encapsulates all the elements that people think are involved in the problem. Once the rich picture has been drawn, the analyst will attempt to extract ‘issues’ and key tasks.

Issues are areas of contention within the problem situation. Key tasks are the essential jobs that must be undertaken within the problem situation.

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Stage 8: Choice (OK, let's go)

You might imagine that after all that has gone before, the decision about whether to go ahead or not would be automatic, but this is rarely the case. There will still be much discussion and ‘fine tuning’ necessary to ensure that the proposal is acceptable. It is at this stage that any qualitative measures of performance are brought into play.


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Stage 4: Generation of routes to objectives (how could we get there?)

This stage explores the different ways of achieving the defined objectives. It is the most imaginative and free-thinking stage of the approach. The idea is initially to generate as many ideas as possible, then to whittle the list down to two or three ‘definite possibilities’ that can be carried further in the development stage.


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1.8 Increasing complication, complexity and risk: are systems becoming more complex?

Figure 17 shows the evolution of two commonly encountered applications of systems – for personal transport and for the reproduction of recorded music. In both cases the degree of complexity of the systems application has increased over time. One of the main reasons for this is technology
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1.1 Introduction: what is the problem?

In late June and early July 2005 a row erupted concerning the operation of a major flagship of government social policy, the tax credit system. Introduced in 2003, it was designed to help those on low incomes and whose social circumstances prevented them from working full-time (Citizens Advice Bureau, 2005). The article reprinted in Box 1 indicates the extent of the political unrest with a system that left families relying on food parcels, and that has been variously described as being ‘in
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References

IEC 60793-2-10 (1992) International Standard 60793-2-10 Optical Fibres – Part 2-10: Product Specifications – Sectional specification for category A1 multimode fibres, International Electrotechnical Commission.
IEC 60793-2-50 (1992) International Standard 60793-2-10 Optical Fibres – Part 2-;50: Product Specifications – Sectional specification for category B single mode fibres, International Electr
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