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6.4.1 The dual nature of technology

Exercise 5

List the main advantages to you of using a refrigerator in your home, then list some of the potential environmental hazards that using a fridge might entail.


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4.1 Domestic appliances and fossil fuels

For this second case study I shall look specifically at the energy use of domestic 'cold appliances', that is freezers and refrigerators, and discuss whether efficiency measures can play a significant role in reducing their energy consumption. The reason for this is quite simple. For many years there has been well-documented evidence of the damage to the environment and cost to human life associated with the extraction, transport and consumption of fossil fuels such as coal and oil, from smog
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3.1 Refrigeration and chlorofluorocarbons

A domestic refrigerator consists essentially of two elements. First, it has a well-insulated box that minimises the flow of heat energy from the warmer outside environment to the cold space inside. Second, it has a motor to circulate a cooling liquid or refrigerant which extracts heat from the cold space and carries it to the outside, where it is released, usually through a radiator at the back. Most refrigerators make use of the principle that when liquids vaporise – that is, change
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2.2 We are part of nature

Take a few minutes to look around at your surroundings before you read on. What do you see? Obviously this depends on where you are at the moment: at home, at work, or perhaps travelling in between, or maybe you have the misfortune to be laid up in hospital. Possibly like me you are at home. I am fortunate to have a study where I do much of my writing and you won't be surprised to hear that I'm looking at a computer screen at the moment. What else can I see? Books and bookshelves, furniture o
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Learning outcomes

After studying this course, you should be able to:

  • demonstrate an awareness of different ways in which our use of technology can affect the environment

  • demonstrate a set of skills in reading and interpreting texts and diagrams containing some technical descriptions.


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3.1 Voyages of discovery and settlement

In Section 2, we saw that there are momentous new and recently transformed flows that are impacting on island territories. Some flows have important precedents, and others may not be quite as novel as they first appear. In this section, we look more closely at some of the flows that have helped make, remake and sometimes unmake is
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1.1 Introduction

Looking back over the 1970s, it is perhaps hard now to appreciate just how dramatic were the changes to the global map of industry taking place at that time. As more and more of the world's industry shifted from the affluent nations to the poorer, less developed countries in search of a cheaper labour force, the global economic map had to be redrawn to take account of the borders crossed and the distances traversed by firms from wealthier countries seeking to generate higher profits by reloca
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2.5 Living systems and information flows

Understanding the role of information flows in feedback relationships is often confusing. It is relatively easy to visualise flows of energy and matter (ecosystem food webs, water flowing through a rainforest ecosystem, etc). But how does information ‘flow’ within feedback loops, and how does this affect systems?

The first point to make clear is that information is only meaningful to those systems that can perceive it. In other words, these systems need to have components th
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2.2 Positive feedback and change

Simple positive feedback loops are easily illustrated since they are the mechanism through which anything changes rapidly. Take for example the explosion of water hyacinth when introduced into new environments:

Water hyacinth is a floating plant that has spread from South America to waterways around the world. It can cover the water so completely that it obstructs the movement of boats. Imagine a lake that is 10
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Glossary

Click on the link below to open the course glossary.

Open glossary now...


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2.4 Oral and written communication

Humans use language to communicate. This is an obvious statement, but what is language and how do we use it? Language is basically a set of symbols with associated meanings. These symbols are delivered using a set of rules for stringing the symbols together to generate additional meaning. Humans use mostly sounds to represent these symbols, although as an Italian I can communicate common meanings by only using a range of hand gestures! We string together phonetic sounds to make words, and we
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6.1 Review

Let's see if we have made any progress in studying thermal effects. The following SAQ is based on Exercise 3, although this time I have a higher expectation of how much you should be able to do.


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References

Checkland, P. (1981) Systems Thinking, Systems Practice, Chichester, Wiley.

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2.3 Summary and conclusions

This topic has addressed the question ‘What is modern engineering?’ The conclusion must be drawn that, until recently, engineers were content with fairly simplistic definitions of their profession, thinking that it consisted of little other than craft skills or practical experience grafted on to a knowledge of mathematics and appropriate natural sciences. It has been methodologically naive, and definitions of the processes of engineering either lack detail (
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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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8.3.1 Fluorine-based etching of silicon

Given the noxious chemistry needed to etch silicon with a liquid, it is perhaps surprising that a gas can do the job at all. However, both xenon fluoride (XeF2) and chlorine trifluoride (ClF3) gases have been used successfully for just this purpose. Each acts as a source of fluorine atoms, which are just barely bound together into molecules and are easily rearranged around silicon atoms with which they form strong bonds, turning them into inert SiF4 gas. These
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7.4.3 Chemical vapour deposition (CVD)

If step coverage or equipment cost is more critical than purity, then PVD is supplanted by CVD.

There are many variants on the chemical vapour deposition technique, but the concept is simple: gases adsorb onto the wafer surface where a chemical reaction forms a solid product. Any other products are gases, or at least volatile liquids, and are pumped away.

There is one obvious restriction: the wafer surface must be the only place where the reaction can occur. If it is not, particle
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3.5.2 Non-contact (tapping) mode

If the probe is taken further away from the sample, into the region beyond the maximum on the force-separation curve of Figure 7, it can be operated in non-contact mode. Typically, the separation required is of the order of 10 nm. The attractive force is much smaller than the repulsive force of the contact mode
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2.3 The fabrication process for a MEMS Pirani sensor

This section is fairly long, but is best read in one go. If you run out of time, reschedule your study to allow you to start again from here.

Thin layers of material are added to the surface by a variety of means, depending on the material to be deposited, and what is already on the wafer.

The sensor starts off, as so many microsensors do, with a silicon wafer, shown in cross section in Author(s): The Open University

1 Structural devices: a static role

The superb manufacturing techniques of microelectronics enable designers of integrated circuits to exercise complete control over the electrical characteristics of each component, such as a transistor, by specifying the shapes and sizes of their active regions. Using photolithographic mask-drawing software on their workstations, they can copy and paste blocks of identical devices all over the chip, knowing that when the design is finally realised in silicon, this extreme uniformity wil
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