4.5 Fibre in LANs Fibre has been slower to be exploited in LANs than in the core transmission network, for similar reasons to the delay in the use of fibre in the access network, but as the data rate demanded of LANs has increased, the case for using fibre has strengthened. Although Ethernet specifications (IEEE 802.3 series) have contained standards for the use of fibre backbones for some time, it was with the development of Gigabit Ethernet and 10 Gigabit Ethernet (10 GbE) standards that fibre became t
4.3 Optical networking DWDM improves the utilisation of optical fibre for point-to-point links, but a further step in exploiting the potential of optical fibre comes from optical networking in which routeing or switching is done optically. Optical networking is in its infancy, but the concept of the optical layer based upon wavelength channels is emerging. The optical layer effectively sits below the SDH layer in the network, and provides wavelength channels from one location to another. An analogy can
2.4.1 Multimode distortion With multimode fibre, the main cause of pulses spreading is the multiple paths that signals can traverse as they travel along the fibre. This phenomenon of multimode distortion is illustrated in Figure 5. Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence Grateful acknowledgement is made to the following sources for permission to reproduce material within this unit: References 6.5 Appreciating some implications for practice I think for most people, the National Health Service would be experienced as a complex situation. If so this would be a good example of perceived complexity. Remember though, if you engaged with it as if it were a difficulty you would not describe the situation as one of perceived complexity. I could not call it a complex system unless I had tried to make sense of it using systems thinking and found, or formulated, a system of interest within it. This means I would have to have a stake in the 4.6 What matters? When the laptop is confirmed to be uncompromised, it is interesting that none of the characters cheers, although they all seem to be relieved. In other words, when the statement comes up, ‘laptop is uncompromised’, people seem to think that is ‘good’, the outcome is fine. They seem to have forgotten that the technician is probably dead at the time. So, in their deliberations, a person's life is forgotten. I am sure that, if they were reminded of it, they would, of course, say that thi References 6.9 Supporting evidence 20. Are all the assertions concerning costs, benefits and risks backed up by relevant supporting evidence? 21. If not, how can this evidence be collected and presented? As was mentioned in Author(s): 6.7 Cost-benefit analysis 17. Does the case clearly and unequivocally demonstrate that benefits outweigh costs? In some contexts ‘cost-benefit analysis’ implies some specific formal method of assessing costs in relation to expected benefits. For example, i 3.2 Business operations: function or process? Traditionally, an enterprise's activities are organised according to a structure based on the well-known business functions: marketing, purchasing, finance, human resources, research and development (R&D), operations, and so on. The exact function title varies from organisation to organisation, but each function has its own more or less well-defined sphere of activity. It carries out its various tasks and passes on information or artefacts to other functions for them to work on. For example, 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 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 7.3.3 Plasmas More control can be achieved in vapour deposition if a plasma is generated. A plasma is simply a gas where a proportion of the molecules have been ionised. The ions remain in an uneasy equilibrium with the electrons they have released, prevented from recombining only because the electrons are hot and fast-moving, and so are difficult to trap. Plasmas are widely used in materials processing, with pressure ranging from 10−3 mbar to 1 mbar and typically up to 1% of the molecul 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 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
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