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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
Author(s): The Open University

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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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2 Construction with lipids

The cell membrane is constructed from lipids. Chemically, lipids are a rather varied group of compounds that include all the substances you might already think of as fats or oils. What they have in common is that they are all insoluble in polar liquids like water, but soluble in organic (carbon-based) solvents: by this I mean the sort of smelly solvents you tend to find in paints, glues and degreasing agents; chloroform is one example. Lipids make up the fatty components of living organisms a
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1 Biological materials

Materials engineers have long recognised the impressive range and combination of properties offered by biological materials. Figure 1 shows some representative examples of the combination of tensile strength and toughness (measured by Young's modulus, or elastic modulus for polymers) offered by natural mat
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Introduction

This unit examines how self-assembled structures based on lipids and proteins provide a framework for cellular processes.

This unit is an adapted extract from the Open University course Engineering small worlds: micro and nano technologies (T356).


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5.15 Summary of Section 5

It is probably worth summarising some of the main points you should take away from this section on primary vibrators. The first thing to remember is that when an instrument is excited, it vibrates strongly at certain frequencies called natural (or resonance) frequencies. The reason for this is that standing waves are set up in the instrument's primary vibrator at these frequencies. The next thing to note is that some primary vibrators, such as a string or an air column, have natural frequenci
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5.5 Vibrating string: pitches of notes produced by stringed instruments

When a string is bowed, plucked or struck, energy is supplied that starts the string vibrating. The string doesn't just vibrate in one single mode; instead, it vibrates in a combination of several modes simultaneously. The displacement along the string is the superposition of the standing-wave patterns corresponding to those modes. For example, if the string vibrated only in the first and second modes, the displacement at a given instant of time might appear as shown in Author(s): The Open University

5.2 Vibrating string: speed of wave propagation

If standing waves are set up when two travelling waves moving in opposite directions interact, then how are standing waves set up on a string and why are they set up only at certain frequencies?

To help answer these questions, I want you first to imagine a length of string that is fixed at one end and held in someone's hand at the other. Suppose the person holding the string flicks their end of the string in such a way that an upward pulse is sent along the string.

As the pulse pa
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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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8.2 Octave pitch and frequency increments

Because a doubling of frequency corresponds to an octave increase of pitch, it follows that there is no constant increment of frequency that always corresponds to a one-octave increment of pitch. That is to say, there is no fixed amount by which a frequency can be augmented that will always produce a one-octave pitch rise.

For instance, starting at the pitch A4 with a frequency of 440 Hz, we need to augment the frequency by 440 Hz to get the pitch one octave above (880 Hz). B
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