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3.11 Summary

This topic has introduced the systems approach, which is the foundation of systems engineering. The systems approach consists of three elements.

  • A set of concepts that can be used to understand the structural and dynamic features of operations systems.

  • Methodologies for managing change. Two current methodologies have been presented: the hard systems approach can be applied in situations where there is a measure of agreement about the
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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 4: Conceptual model

The conceptual (or activity) model contains all the activities that the relevant system would have to perform. The model is usually drawn as a block diagram.


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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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Stage 2: Analysis of the existing situation (where are we now?)

Having defined and agreed on the problem, it is necessary to decide on the system in which you consider it plays a part. In practice the two stages are closely linked and the analysis of the existing system nearly always means a redefinition or refinement of the problem or opportunity. Identifying and defining the problem and the system or systems that relate to it are critical for the success of subsequent analysis.


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3.5 Systems concepts: dynamic behaviour: input-transformation-output

Utilitarian systems, as previously discussed, are the means we use to transform resource inputs into useful goods and services. Any system can be divided into a set of input-transformation-output blocks. These are usually represented as in Figure 31. This way of looking at systems can be use
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1.9 Increasing complication, complexity and risk: summary

The three levels of change problem, simplicity, complication and complexity, can be associated with craft, engineering and systems engineering knowledge. The three categories of change problem represent different levels of uncertainty of what needs to be done and how to do it. The greater uncertainty brings increased risk. Although we tend to be risk averse we will take on greater risk if the returns are commensurate with doing so.

Human experience can be divided into three worlds. The
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Introduction

The aim of this unit is to answer five questions:

  • Why is systems engineering important?

  • What is modern engineering?

  • What is systems?

  • What is systems engineering?

  • What approach to systems engineering does the course adopt?

This unit is from our archive and is an adapted extract from Systems engineering (T837) which is no longer taught by The Open University. If you wan
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Acknowledgements

Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

Grateful acknowledgement is made to the following source for permission to reproduce material within this unit:

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5 Summary

The building blocks of a basic optical-fibre communications link are the modulated light source, the fibre and the detector. There are choices to be made between different types of light source and fibre, with trade-offs between cost and performance. For example, for high signalling rates over long distances single-mode fibre will be used with a single-mode laser (possibly with external modulation) operating in the 1550 nm window, whereas for short-distance links operating at lower signalling
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4.5.1 Gigabit Ethernet

Gigabit Ethernet specifies four categories:

  • 1000BASE-SX, for transmission over multimode fibre using an LED in the 800 nm window (the wavelength is specified to be between 770 and 860 nm). The specification is for up to 275 m on 62.5/125 mm multimode fibre, or 550 m on 50/125 mm multimode fibre;

  • 1000BASE-LX, for transmission over multimode or single-mode fibre using a laser in the 1300 nm window (specified to be between 1270 and 1355
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4.5 Fibre in LANs

Fibre has been slower to be exploited in LANs than in the core transmission network, for similar reasons to the delay in the use of fibre in the access network, but as the data rate demanded of LANs has increased, the case for using fibre has strengthened.

Although Ethernet specifications (IEEE 802.3 series) have contained standards for the use of fibre backbones for some time, it was with the development of Gigabit Ethernet and 10 Gigabit Ethernet (10 GbE) standards that fibre became t
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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
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4.5 Torture

The question of torture is also raised in the play. Herrenvolk claims that he does not do the torture; it is some Uzbekistan outfit that does it. He actually gives them a justification by saying, in a rather glib way, that it is a lot easier to open a human being than an encrypted laptop. Of course, the question is, is it ever ‘right’ to exploit this as a means of finding things out? I suspect most of us would say ‘no’.


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2 An introduction to the process view of business operations

As we touched on in Section 1, the course that this unit is taken from is concerned with how best to manage the set of business processes that are directly responsible for converting a variety of resources (such as materials, money and the effort of people) into outputs (such as manufactured goods and/or
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8.3.3 Reactive ion etching: chlorine/argon plasma etching of aluminium

In a reactive ion etch (RIE), a chemical reaction is used to weaken the bonding of the surface of the material and assist the sputtering process. This combines the high rate and selectivity of a gas-phase etch with the directionality of a sputter etch.

For example, consider aluminium etched anisotropically by a Cl2/Ar mixed-gas plasma, which etches at up to 1 μm min−1:

  • Power pumped into the plasma breaks the gases up, rel
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1.4 Sensitivity

Since a biased MOS structure builds up a depletion region with an electric field similar to that in a p–n junction, it's worth thinking about what would happen if light were to be absorbed in an MOS capacitor, generating electron–hole pairs.

Exercise 2

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3.2 Recording on the wire

A paper published by Oberlin Smith in an 1888 issue of Electrical World discussed the possibilities for recording sound using the property of magnetism. He envisaged a cotton thread impregnated with steel dust passing through a coil carrying a current controlled by a microphone. The variations with the sound in the strength of the current would cause corresponding magnetic fluctuations in the magnetic medium. Unfortunately he dismissed his idea because, as he said in his paper, he thou
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3.2 Protein structure

Proteins are one example of a biopolymer. You will already be familiar with synthetic polymers such as polyethylene and nylon: long chains made up of many thousands of repeating units, called monomers, linked together by strong covalent bonds. Polymers are particularly versatile materials because of the very different strengths of the bonds between monomer units in the chain (strong) and between one chain and another (weak). By varying the arrangement of chains within a material a huge
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