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6.4.2 A broad view of technology

This dual nature is not because machines or chemicals are inherently good or bad; it arises from the way societies decide to use them (or not). This makes sense if you take a broad view of technology, outlined at the beginning of this Introduction. This is the understanding that technology, and it's uses from artefacts to infrastructure, is the product of human and social action. It is a major driver of the development of societies and their economies, but the forms and directions thes
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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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5.1 Food preservation and the development of refrigeration

Most societies have had traditional methods of preserving food: drying, baking, pickling, salting, smoking, the use of sugar, and in cold climates, freezing or chilling, with the use of ice houses in the summer. These techniques were usually carried out at a local level, which meant that most perishable food was consumed near to where it was produced, and any food processing was usually small-scale and localised. Cattle and livestock, for example, were moved 'on the hoof' from their pastures
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1.2.1 Managing risk in conditions of uncertainty

Earlier we considered what is meant by ‘environmental responses’. There are two aspects to this concept. One is the response made by the environment to processes of change, whether brought about by natural or human causes or a combination of both. The other is the response to environmental changes made by humans or non-humans. In this section we shall consider both of these aspects of response by focusing on an issue of particular significance in the Blackwater: how the envi
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Groups and teamwork
Are you always the quiet one when it comes to group discussion? This free course, Groups and teamwork, will help you improve your working relationships with other people in groups of three or more. The course also deals with project life cycles, project management and the role of the leader. First published on Mon, 10 Dec 2018 as Author(s): Creator not set

Superconductivity
The fascinating phenomenon of superconductivity and its potential applications has attracted the attention of scientists, engineers and businessmen. Intense research has taken place to discover new superconductors, to understand the physics that underlies the properties of superconductors, and to develop new applications for these materials. In this free course you will read about the history of superconductors, taking a brief look at their properties. You will also learn about modelling the pro
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Except for third party materials and otherwise stated (see http://www.open.ac.uk/conditions terms and conditions), this content is made available under a http://creativecommons.org/licenses/by-nc-sa/2

2.3 Negative feedback and stability

If positive feedback results in change, then another mechanism must exist that creates stability. This is negative feedback.

What stops water hyacinth from taking over the world? Clearly, it is the lack of tropical freshwater. As the number of water hyacinth reaches the limits of their water body, there is a sudden increase in the death rate as offspring compete for the ever decreasing levels of sunlight. The sudden overcrowding allows the establishment of a negative feed
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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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1.3 Activities

Activity 4A engages you in developing a more sophisticated visual model of one of the themes raised in the ‘Powerdown Show’ programme. The sign graph diagramming technique is the ultimate visual modelling approach for revealing positive and negative feedback relationships, so you will be using this technique to first explore, and then communicate, the dynamic nature of the complex situation you have chosen to investigate.

The first sign graph you will develop will focus on r
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2.1 Boiling water

Whether it's to wash clothes, make a cup of tea, or just make it safe to drink, water often has to be heated – sometimes to boiling point. There are many ways to do this, but a very common means is some form of electric water-boiler, such as a kettle or an urn. In all but the crudest ones, a device is fitted to ensure that heating does not continue once the boiling point of water is reached.

In deciding on the type and design of such a device, we can suppose that a company manufacturi
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Keep on learning

Study another free course

There are more than 800 courses on OpenLearn for you to
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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.


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5.8 Reviewing some implications for systems practice

The following anecdote exemplifies one of the main reasons why I think juggling the B ball is important for systems practice. The story relates to two practitioners who were able to connect with the history of organizational complexity ideas. It describes the process they chose to take in response to a highly specific organizational-development tender document couched in traditional ways:

Our first decision was to
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3.1 Introduction

I wonder if you experience complexity in your daily life? For much of the time I struggle to keep my head above water as I try to understand and manage the complexity I experience as part of everyday life. I find social commentator and cartoonist Michael Leunig's depiction of a solitary figure looking through an ‘understandascope’ (Author(s): The Open University

2.3 Appreciating epistemological issues

Common sense tells me my experience and understanding of the world are limited. I am 173 cm in height. That limits my view of the world. It may not matter much that I cannot see what my house looks like from above but it does mean there will be things going on in the roof I may not notice until they impinge on areas that I can experience.

More significantly, there is a real limitation on understanding the experiences of other people. You might tell me about your experience but your desc
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8.3.6 Deep silicon etching

MEMS structures often require etching to a much greater depth than is needed for microelectronics. A rate of 1–2 μm min−1 may be quite sufficient for making transistors less than 1 mm deep, but to etch through 600 mm of silicon to form an accelerometer would take all day. The advent of MEMS and wafer-level packaging applications, therefore, brought a need for yet faster anisotropic etches, requiring advances both in the process and in the etching equipment.

Capacitive co
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8.2 Wet etches: acids and bases

The simplest etches use a liquid solvent that converts the material into a soluble compound or a gas. Unfortunately, most materials used in micro-devices have few soluble compounds, so some very aggressive chemicals are needed to attack them. Here is a list of some of the most commonly used ones:

  • Hydrofluoric acid (chemical formula HF) is used to convert silicon dioxide into water-soluble H2SiF6 (plus some hydrogen and water). It
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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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2.1 Introduction

One aspect of micro and nano scale engineering that distinguishes it from many other forms of manufacturing is the way it involves building both the devices themselves and the very materials from which they are made, in one place and at more or less the same time. In general, MEMS are made from thin layers of new material produced, and then shaped in some way, on the surface of a silicon wafer. The devices contain several different materials, and have a three-dimensional structu
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4.10 High girders and the train

Divers found the high girders lying on their sides in the shallow water of the river bed a short distance away (Figure 22), within which the almost intact remains of the train itself was found. No bodies were recovered because they had all been washed away by the river or tide. Although bodies were recovered
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