3.1 The steps to systems modelling

Systems modelling in practice usually involves six broad steps, within each of which there may be many subsidiary steps and some checking and revision. There is also likely to be iteration back to the earlier steps, as issues which call for changes in earlier decisions are uncovered.

Nevertheless, in my experience, the following six steps are likely to cover the basics.

1. Identify the system of interest, in particular specify the system boundary a
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Stage 5: Formulating measures of performance (how will we know when we have arrived?)

The hard systems approach emphasises the need to have measurable means of assessing the efficacy of any potential solution or design, but recognizes that this may not always be possible.

3.7 Systems methodologies for managing change

The use of systems concepts and models forms part of a process of investigation that is often described in the literature of systems, design and decision-making as a ‘methodology’, where a methodology is a process of enquiry, not a method to produce a predetermined result.

A systems methodology has the following characteristics.

• It is, or it provides, the means for the investigator to draw up a plan for studying a situation. This encourages
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1.5 Increasing complication, complexity and risk: the underlying relationship

Figure 3 showed five commonly encountered problems of effecting different types of change. These are notionally located on a spectrum of change that ranges from no change at all, to complete revolution. The relationship suggested on the figure is that as the degree of change – represented
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1.3 Example 1 The Workcenter that didn't

Autodesk Inc. is the world's largest supplier of design and engineering software. It currently markets over thirty products but is most famous for its AutoCAD® two- and three-dimensional design and drafting software. The company is the market leader in this type of application, with over 4 million customers worldwide.

The Autodesk story began in 1982 with a group of programmers, centred on San Francisco, writing code for design software in their spare time. The group demonstrated a cob
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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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Conclusion

This free course provided an introduction to studying Computing & IT. It took you through a series of exercises designed to develop your approach to study and learning at a distance, and helped to improve your confidence as an independent learner.

3.2 Making sense of the metaphor

The metaphor of the juggler keeping the four balls in the air is a powerful way for me to think about what I do when I try to be effective in my practice. It matches with my experience: it takes concentration and skill to do it well. But metaphors conceal features of experience, as well as calling them to attention. The juggler metaphor conceals that the four elements of effective practice often seem to be related. I cannot juggle them as if they were independent of each other. I can imagine
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8.5 Review

We can sum up the distinctive features of wet etching with a few key points:

• Wet etching, in general, is a simple process to operate. Wafers are immersed in a solution for a while before being taken out, rinsed, and dried. However, certain etches require more sophistication. They may need one or more of the following: heating and agitation of the solution; reflux of vapours to maintain concentrations; protection of back side of the wafer; incorporation
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8.4.1 Open-loop control

Open-loop is the crudest way of controlling etch depth. It relies on ensuring that every aspect of the process that can affect the rate of progress of the etch is kept under tight control. This can add up to a sizeable list. Table 5 shows just some parameters that affect both wet and dry etching.

Whethe
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3.3 The scanning tunnelling microscope

The first scanning probe microscope, the scanning tunnelling microscope (STM), was invented by Heinrich Rohrer and Gerd Binnig in 1981, and used the quantum-mechanical effect of electron tunnelling (in which electrons ‘tunnel’ through an energy barrier that classical physics would suggest is too high to cross). In this instance, the energy barrier is the tendency of the metal of the probe tip to want to hang on to its electrons. In effect, as you try to remove an electron from the surface
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3.2 The principles of scanning probe microscopes

Scanning probe microscopy is a term that is applied to a set of imaging methods based on a common element: a fine stylus. In many ways, what scanning probe microscopes do is similar to what a gramophone does. A gramophone stylus scans a spiral groove (by travelling along it) on which information has been encoded in the form of undulations in the groove wall. Side-to-side and up-and-down movements of the stylus (which is mounted on one end of a rod supported and pivoted at its centre) as it fo
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