6.4 Driven oscillations and resonance

Finally I need to consider the situation where the oscillator is driven, as in the case of the AFM cantilever. The driving force will depend on the application, but for my mass on a spring it might be a small motor driving what was the fixed end of the spring up and down. The simplest expression for an oscillating driving force FD will be something like:

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2.4 Thermal and electrical conductance

Thermal conductance, Gt, is analogous to electrical conductance, Ge. The longer a conductor is and the smaller its cross section, the lower its conductance will be.

Thermal conductance is given by:

and electrical conductance by:


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1.3 The capacity of an MOS structure to store charge

Figure 1 shows a schematic section through an MOS structure and sets up a colour scheme that distinguishes the different layers. In this case the M-layer is provided by heavily doped polysilicon and the semiconductor base material is p-type silicon.


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5.1 The development of the bicycle

Section 4 has looked at how we can follow a logical route or map, from the expression of a need, to arrive at possible solutions to a problem. In Sections 5 and 6 we look in more detail at two quite different examples of engineering problems. Our first example is the historical development of the bicycle frame; the second concerns a vital component of a car's airbag system.

The weight of a bicycle frame is a major burden that the cyclist has to bear. There have certainly been times whe
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4.8 Assess and review again

If you've been following the stages of our problem-solving map, then the chances are you're ahead of me here (Figure 19). Yes, if it works, hurrah; if it doesn't then off we go again, all the way back to ‘possible solutions’ and selecting the best of the rest. Or maybe even going back to the be
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5.10 Bridge stability

Any fracture of the diagonal wind brace tie bars could allow substantial lateral movement at the top of the piers. If these tie bars had already been injured by the previous train to cross the bridge, it would have only taken a little extra effort to complete the process as the mail train arrived over each pier supporting the high girders. Once the wind braces had failed completely, and the struts fractured at their connections each pier would behave as two separate supporting structures.


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5.9 Vibrating air column: standing waves in a cylindrical tube closed at one end

We'll now turn our attention to the setting up of standing waves in an air column contained within a cylindrical tube that is open at one end but closed at the other. Straight away we can say that the closed end must be a displacement node since the air molecules can't move at this boundary. That means it must be a pressure antinode. The open end, as we saw previously, will be a displacement antinode (that is, a pressure node).

Now, you may recall that the distance between a node and a
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4.1 The experimental result

One way to establish the speed of sound is to measure it experimentally. That is, one measures how long the sound takes to travel a known distance, and from this works out the speed. The answer turns out to depend somewhat on the prevailing temperature and humidity. At an air temperature of 14 °C the speed is 340 metres per second and at about 22.5 °C it is 345 metres per second. That is a change of speed of less than 1.5 per cent for an appreciable change of temperature. To a reasonable ap
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2.4 Period

You saw in Section 2.3 that the prongs of the tuning fork vibrate cyclically. You also learned that a cycle of the prongs' vibration is a complete sequence of motion up to the point at which the motion starts to repeat itself. Another term for this repetitive kind of motion is periodic motion. The t
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1.1 Music and technology

Music technology in one guise or another is part of everybody's life, because music is a part of almost everybody's life. For instance, if you are an instrumental performer of music, professional or not, then your instrument, be it the harp or the rock'n'roll drums, will be the result of considerable technological expertise on the part of the instrument maker. On the other hand, if you are not a performer but like to listen to music, the chances are that most of your listening is done via a h
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17.1 Part 4: 1 Revising your understanding

By now, it is probably apparent that those of us writing this unit are enthusiastic about the possibilities for systems thinking and complexity thinking. Our enthusiasm extends beyond just thinking, to applying systems thinking to a situation in the world that we experience as complex for the purpose of doing something about it. Our focus is on improving a situation experienced as problematical or on grasping some opportunity. It is the act of relating systems thinking to action in a given co
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9.1 Making sense of complexity

This section is about finding ways of thinking about complex situations – making sense of complexity. This is a process of discovery. It involves thinking about complexity in an orderly way that allows you to enter a deeper understanding of the complexity. It goes beyond immersion in, and representation of, complexity.

The invitation I am making in this section is to move into the possibility of structuring complexity. Notice I am not suggesting there is structure in the
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18.5 Government regulations and legislation

You saw earlier in Part 2 how governments can stimulate invention by providing incentives for manufacturers to develop new products. The example given was in the field of alternative fuel vehicles in the USA and Europe. As well as influencing the development of innovations, government legislation and regulations can also affect diffusion by creating conditions that encourage consumers to buy and use particular innovations.

In the UK the government has introduced a mixture of incentives
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18.2.1 Relative advantage

In order to succeed, an innovation has to be perceived as offering advantages relative to existing comparable products or services. For example, it has more chance of selling if it is cheaper to make and buy, does the job better or does something previously not possible, offers more features, is easier to use, or is reliable and safe. Relative advantage is sometimes called competitive advantage.

A good example is how the steady reduction in size and increase in efficiency of the electri
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17.3 Choosing appropriate materials and manufacturing process

The choice of materials and manufacturing process for a particular new product is an important aspect of the innovation process. It is not necessarily the case that the materials chosen for the early prototypes of an invention are those best suited for the larger-scale manufacture of the innovation. Choice of materials can affect the performance, quality and economic manufacture of most new products, so it's important to choose wisely.

While inventors and designers usually need to seek
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17.2 Getting finance and organisational backing

Like talk, ideas are cheap. Even generating a prototype of an invention can be cheap compared with the resources needed to produce and market an innovation. The independent inventor or designer is likely to have to rely on family and friends for financial backing, particularly in the early stages. Seed capital is sometimes available in the form of innovation grants from government bodies, such as the Department for Trade and Industry in the UK, which offers development funding to individuals
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11.7 Characteristics of inventors

In their classic book The Sources of Invention (1969) John Jewkes, David Sawers and Richard Stillerman observe the following about inventors, whether working outside or inside an organisation.

  • Inventors tend to be absorbed with their own ideas and to feel strongly about their importance and potential.

  • Inventors can be impatient with those who don't share their optimism.

  • Inventors are often isolated because they are
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11.6 Step 5 – critical revision

Once a solution has been obtained it is then necessary to explore the extent to which it effectively solves the problem and where necessary revise it. Although more attention has been given to the moment of inspiration during the act of insight than to any other stage of invention, it is this process of critical revision that is usually the longest, most difficult and costly stage.

Genius is 1 per cent inspirati
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11.5.4 Analogy

Analogy draws on similar situations to provide ideas for invention and design. Alexander Graham Bell used the analogy of the human ear when designing telephone apparatus to receive sound. As mentioned above, his first receivers were much better than his transmitters where the analogy with the ear didn't work as well. When devising their flying machine, the Wright brothers used the analogy of soaring birds twisting their wings to restore balance. They designed the wings of their aircraft to be
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11.1 Five steps to invention

I've looked at what motivates people and organisations to invent. I'll look more closely now at what's actually involved in inventing something.

Wherever invention occurs, whether with a lone inventor or in a creative team within an organisation, there seem to be common factors involved. There have been many attempts over the past 100 years to explain the creative process that occurs while people are attempting to solve problems. I'm going to combine ideas from two such models of the st
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