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.
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
1.1 Overview Why are disasters important? They attract public attention because there is great loss of life, or because the event happened suddenly and quite unexpectedly, or because the accident occurred to a new project that had been regarded as completely safe. Certainly, the aspect of suddenness is one that features in many catastrophes, and indeed, it is this feature by which a catastrophe is defined. Great disasters are always traumatic, especially for those who endure them and come through al
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
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2 Conclusion The Forth Road Bridge, connecting Edinburgh with Fife, continues to face a number of problems regarding its deteriorating condition. Both structural issues and the increasing wear and tear of the traffic upon the bridge are causes of concern for the engineers who maintain it.
4 Unit summary Sound recording really took off once the public's demand for recorded music had been acknowledged. The choice of technology, cylinder or disc, was determined more by the selection of the artist and material than the quality of the sound. Development of disc technology was slow due to the lack of better alternatives, remaining substantially unchanged for over fifty years. The development of radio broadcasting caused a slump in the record industry but eventually it not only provided improvement
3.4 Compact cassettes The use of magnetic tape for home use has always been somewhat problematic. Whilst it offers several advantages over discs, being capable of high-quality sound, substantially free from surface noise and able to make personal recordings, tape never became so popular as to make any serious inroads into the sales of discs. Why should this be the case? The answer is one of convenience, for magnetic tape has always been difficult to handle compared with discs – threading the tape through the mac
2.7 Music matters There was little difference in sound quality between the phonograph cylinder and the gramophone disc. The limited frequency response of the acoustic recording and playback process restricted the sounds that could be reproduced. Instruments tended to be limited to brass and piano, and middle-register voices (alto and tenor) were the most suitable. So why did the disc succeed over the cylinder? The answer has little to do with technology and much more to do with the tenor Enrico Caruso and the
2.6 Turning the handle The owners of the original hand-cranked gramophones were instructed that the standard velocity for ‘seven-inch plates’ was about 70 revolutions per minute. The owner was also warned that failure to turn the plate at the correct speed would lead to a lowering of the pitch if turned too slow, or a raising of the pitch if turned too fast. It is doubtful if true reproduction of the recorded sound was ever achieved by the owners of these machines! A better power source was needed and as electr
Acknowledgements Grateful acknowledgement is made to the following sources:
Figure 7 (a): PDB ID 1BKV Kramer, R. Z., Bella, J., Mayville, P., Brodsky, B. and Berman, H. M. (1990) ‘Sequence dependent conformational variations of collagen triple-helical structure’, Natural Structural Biology, vol. 6, pp. 454–57
Figure 7(b): PDB ID 1ATN Kabsch, W., Mannherz, H. G., Suck, D., Pai, E. F. and Holmes, K. C. (1990) ‘Atomic structure
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3.3 Spider silk The presence of regions of helical and sheet-like structures within a protein will affect its properties in different ways: a particularly striking example of this is provided by spider silk. Imagine a polymer that forms fibres stronger, by mass, than steel and can be processed from water at ambient temperature and low pressure. As a consequence of its biological origin, it is extremely environmentally friendly and totally recyclable. It may sound like science fiction, but this i
2 Construction with lipids The cell membrane is constructed from lipids. Chemically, lipids are a rather varied group of compounds that include all the substances you might already think of as fats or oils. What they have in common is that they are all insoluble in polar liquids like water, but soluble in organic (carbon-based) solvents: by this I mean the sort of smelly solvents you tend to find in paints, glues and degreasing agents; chloroform is one example. Lipids make up the fatty components of living organisms a
5.13.4 Pitches of notes produced by percussion instruments We have seen that none of the rectangular bar, the circular membrane and the circular plate have harmonically related natural frequencies. It may not surprise you to learn, therefore, that instruments containing these primary vibrators tend to produce notes that don't have a very well-defined sense of pitch. This is certainly true in the case of the cymbal, which has a circular plate as its primary vibrator. Whether a single cymbal is struck with a drumstick or two cymbals are crashed t
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
5.13 Other primary vibrators You saw in the previous two sections that stringed instruments and wind instruments possess primary vibrators that have harmonically related natural frequencies. As a result, these two classes of instruments produce notes that have a well-defined sense of pitch. In this section, I want to briefly introduce you to some primary vibrators that don't have harmonically related natural frequencies. Specifically we shall take a look at a rectangular bar, a circular membrane and a circular plat
5.10 Vibrating air column: end effects In the previous two sections on standing waves in cylindrical tubes, we assumed that at an open end there must be a pressure node. In fact, the pressure node (and the corresponding displacement antinode) actually lies a small distance outside the tube. The effect is that the air column behaves as though it were a little longer than it really is by an amount called the end correction. Because of this end correction, the resonance frequencies will be a little lower than originally expect
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
5.7 Vibrating air column: reflection at the end of an air column When a sound wave reaches the end of an air column, it is clear that it will be reflected if the tube end is closed. You only have to imagine yourself standing some distance, let's say 50 metres, away from a flat wall. If you shout, you will hear an echo – the reflection of the sound wave you projected. There is one difference, though, between the reflection of a sound wave and the reflection of the wave on a string that you met previously. When a sound wave is reflected from a closed
5.6 Vibrating air column You learned in the previous section that for standing waves to be set up on a string there must be reflection. A travelling wave reaches the end of the string and is reflected. This results in a second travelling wave, which moves back up the string in the opposite direction to the first wave. The two travelling waves interact to produce a standing wave. Standing waves are set up in an air column enclosed within a tube in a very similar way. Again there must be reflection. In this case,
5.5 Vibrating string: pitches of notes produced by stringed instruments When a string is bowed, plucked or struck, energy is supplied that starts the string vibrating. The string doesn't just vibrate in one single mode; instead, it vibrates in a combination of several modes simultaneously. The displacement along the string is the superposition of the standing-wave patterns corresponding to those modes. For example, if the string vibrated only in the first and second modes, the displacement at a given instant of time might appear as shown in Author(s):
