3.6.1 Stiffness Just how compliant does an AFM cantilever have to be to enable it to follow the undulations in a surface on an atomic scale? How can we find out? It turns out that this is easier than at first it seems. A simple assumption we can make is that the compliance of the cantilever should be appreciably greater than that of a typical bond that holds atoms to one another. Here's one way in which a rough estimate of the stiffness (the force required to cause a given deflection) of the bonds in a
Introduction This unit examines how small features can be etched and cut out of solid materials at a very small scale. This unit is an adapted extract from the Open University course Engineering small worlds: micro and nano technologies
(T356).
3.1.3 Micro lenses A smart way to compensate for surrendering area to data transfer is to build in microscopic lenses at each pixel: the processing sequence that is used to manufacture the MOS devices already involves transparent polymeric material and, calling again on the ingenuity of the designers of microelectronics, significant enhancement to optical efficiency can be won.
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. 7.1 The engineer and society Section 2 outlined some of the needs for engineering. Society relies on engineers to create solutions to the problems involved in meeting those needs. This is a good time to pause and point out that inevitably, in return for all this fun and power, engineers have a responsibility to society. The people who employ our services, directly or indirectly, have to have an assurance that we are working within certain social, safety and ethical boundaries. Particularly given the increasing tren 4.5.1 Mathematical models Computers in the last few decades have, in many cases, made mathematical modelling a lot easier. Models that used to require hours of manual cranking through long equations can now be created on a screen using specialist software. Processes can be recreated – modelled – in the time it takes to press a few buttons. For example, when designing a pipe network to carry a gas or fluid, such as in the village water supply problem, you might wish to know how the flow would be distributed w 5.9 Mechanical tests by David Kirkaldy In order to determine which of the several parts of the joint were weakest, and gain some idea of the scatter in strength, David Kirkaldy was employed by Henry Law to test various samples he had collected from the bases of the fallen piers. David Kirkaldy had a good reputation for accurate and rigorous mechanical testing of materials using a large tensometer he had designed and built in London (see Input 9, linked below). Click 'View document' below to open Input 9 5.4 Expert evidence: an overview The second part of the enquiry was devoted to analysis of the disaster. There were three engineers appointed: Mr Henry Law for the enquiry, and Dr William Pole and Mr Allan Stewart acting on behalf of the NBR. In addition, Mr Law collected samples of columnar material and wrought iron straps, bolts and struts for mechanical testing, as well as many broken parts to be shown as exhibits at the enquiry. He asked Mr David Kirkaldy to test the samples using a hydraulically operated tensometer. Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: This video extract is from Coast Se Module team
Academic staff
Dr Alec Goodyear (course chair) Professor Nicholas Braithwaite Jan Kowal Dr Tony Nixon Dr Sally Organ Robin Harding (critical reader) James McLannahan (critical reader) Dr Martin Rist (critical reader) Dr George Weidmann (critical reader) Peta Jellis (course manager) P 5.13.1 Rectangular bar If a solid rectangular bar is excited by striking it, energy is supplied that starts the bar vibrating transversely. The bar will vibrate in a number of modes simultaneously since the striking action supplies energy over a range of frequencies. The motion of the bar will be the superposition of the standing-wave patterns of the excited modes. Assume for the moment that the rectangular bar is supported in such a way that both ends are free to vibrate and the effects of the supports can b 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 10.1 Introduction For a variety of reasons, not least the very wide dynamic range of human hearing, the decibel (symbol dB) is often used as a unit for the amplitude of sound waves. The decibel is also used in other contexts, such as specifying the amplification of amplifiers or the degree to which a signal is affected by noise. In the context of sound, the use of the decibel as a unit captures something of the subjective impression of the way loudness changes with amplitude. The decibel unit has 6.1 Defining amplitude Another important property of a sine wave we need to be able to specify is its amplitude. In essence, the amplitude of a sine wave is its size. Unfortunately there are various ways of defining what is meant by the size of a sine wave, and you are likely to come across many of them in material you look at outside this unit. Before I explain what our definition is, it will help matters if we look at what is meant by the average value of a sine wave. Figure 16 shows a sinusoidally a 1.3 Describing sound Let's now take a closer look at my list of categories from Activity 3, starting with item (a). In each of my descriptions of this sort, I referred to the source–cause of the sound: that is, an object or an instrument (the source of the sound) and ways of using it to produce a sou 7.2.4 Trap 4: words and wordiness I have seen some effective rich pictures with lots of words in them but they are quite rare in my experience. More often, lots of words make the rich picture less rich. Part of the later use of a rich picture might include looking for patterns. Words inhibit your ability to spot patterns. If you do use speech bubbles, use what people say, not your interpretation, unless the bubble is about some general attitude. Examples might be ‘Aaagh!’, ‘Help!’, ‘Oops!’ – the sort of th 2 Part 1 Starting the unit Welcome to T306_2 Managing complexity: a systems approach – introduction. As I write, I experience a sense of excitement. For me, as for you, this is the beginning of the unit. These are the first few sentences I'm writing and so, although I have a good idea of how the unit is going to turn out, the details are by no means clear. Nevertheless, the excitement and anticipation I, and maybe you, are experiencing now is an important ingredient in what will become our experiences of the u 13 Part 2: 4 Preparing for innovation Many inventors have said that having the idea for an invention is the easy part. This is often demonstrated by the frequency of examples of simultaneous invention. At one exhibition of inventions I attended there were three separate portable ladders to escape from fires, two systems for using rainwater to flush toilets, two types of portable vehicle wheel clamp, and two methods of reducing red-eye in flash photography. In most cases of technological innovation only one of the competing techno 10.5 Desire to help others This is a less common motivation but it shows not everyone is driven by money. In 1991 the inventor Trevor Baylis saw a BBC documentary about the spread of HIV/AIDS in Africa. What was needed was a way of broadcasting the safe-sex message to people in areas without electricity and where batteries for a radio could cost a month's wages. Solar power wouldn't necessarily help as most people who could get to a radio listened in the evening after work. While absorbing this information he ima 9 Part 2: Invention Having taken a broad look at the whole innovation process from invention to diffusion, I'll go back and look more closely at what motivates individuals and organisations to invent. Then I'll consider how people generate ideas for inventions and the designs based on the inventions.
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