Glossary Click on the link below to open the course glossary.
1.3 Activities In Activity 3A, you will be exploring your 'personal ecology' – the relationship between the physical places w
References 3.1 (2A): Exploring the global implications of different mindsets In this activity the aim is to investigate the implications of different mindsets with regards to the future unfolding of events on a global scale. So far, you have focused your attention on exploring your p 2.4 Oral and written communication Humans use language to communicate. This is an obvious statement, but what is language and how do we use it? Language is basically a set of symbols with associated meanings. These symbols are delivered using a set of rules for stringing the symbols together to generate additional meaning. Humans use mostly sounds to represent these symbols, although as an Italian I can communicate common meanings by only using a range of hand gestures! We string together phonetic sounds to make words, and we 1.2 Readings In considering the environmental and social challenges that we are currently facing, we are clearly dealing with so-called 'wicked' problems: the 'problems' manifest themselves only as you try to engage and change society and the Author(s): 6.1 Review Let's see if we have made any progress in studying thermal effects. The following SAQ is based on Exercise 3, although this time I have a higher expectation of how much you should be able to do. References 2.3 Summary and conclusions This topic has addressed the question ‘What is modern engineering?’ The conclusion must be drawn that, until recently, engineers were content with fairly simplistic definitions of their profession, thinking that it consisted of little other than craft skills or practical experience grafted on to a knowledge of mathematics and appropriate natural sciences. It has been methodologically naive, and definitions of the processes of engineering either lack detail ( 1.1 Introduction: what is the problem? In late June and early July 2005 a row erupted concerning the operation of a major flagship of government social policy, the tax credit system. Introduced in 2003, it was designed to help those on low incomes and whose social circumstances prevented them from working full-time (Citizens Advice Bureau, 2005). The article reprinted in Box 1 indicates the extent of the political unrest with a system that left families relying on food parcels, and that has been variously described as being ‘in Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence. Grateful acknowledgement is made to the following sources: Course image: Author(s): 8.4.2 Closed-loop control Very often in the manufacture of microsystems, the etching steps are meant to remove a layer of material entirely from within the areas defined by the mask pattern. This offers the opportunity to detect the moment the etch is complete by spotting a change in composition of the reaction products from the etching. This is particularly useful in dry etching, where very small numbers of molecules can be detected using optical or mass-spectrometry-based residual gas analysis. Gaseous reaction prod 8.3.1 Fluorine-based etching of silicon Given the noxious chemistry needed to etch silicon with a liquid, it is perhaps surprising that a gas can do the job at all. However, both xenon fluoride (XeF2) and chlorine trifluoride (ClF3) gases have been used successfully for just this purpose. Each acts as a source of fluorine atoms, which are just barely bound together into molecules and are easily rearranged around silicon atoms with which they form strong bonds, turning them into inert SiF4 gas. These 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 7.4.2 Reactive PVD For a simple compound, such as a metal oxide or nitride, a modification to the sputter deposition technique can be used. The plasma is formed from a reactive gas, such as nitrogen, instead of the inert argon used for conventional PVD. A side effect of the plasma excitation is that chemical bonds are broken in the source gas to release copious unpaired atoms (radicals), which are extremely reactive and form a monolayer coating of nitride on the target surface. These can then be sputtere 3.5.2 Non-contact (tapping) mode If the probe is taken further away from the sample, into the region beyond the maximum on the force-separation curve of Figure 7, it can be operated in non-contact mode. Typically, the separation required is of the order of 10 nm. The attractive force is much smaller than the repulsive force of the contact mode 2.3 The fabrication process for a MEMS Pirani sensor This section is fairly long, but is best read in one go. If you run out of time, reschedule your study to allow you to start again from here. Thin layers of material are added to the surface by a variety of means, depending on the material to be deposited, and what is already on the wafer. The sensor starts off, as so many microsensors do, with a silicon wafer, shown in cross section in Author(s): 1 Structural devices: a static role The superb manufacturing techniques of microelectronics enable designers of integrated circuits to exercise complete control over the electrical characteristics of each component, such as a transistor, by specifying the shapes and sizes of their active regions. Using photolithographic mask-drawing software on their workstations, they can copy and paste blocks of identical devices all over the chip, knowing that when the design is finally realised in silicon, this extreme uniformity wil Learning outcomes After studying this course, you should be able to: understand how to relate physical dimensions and materials properties to static and dynamic behaviour demonstrate an awareness of how small features are cut out in solid materials, and how small features are built up in solid materials describe the piezoelectric effect and its use for producing small-scale movement in mechanical devices state the relative significance of different for Acknowledgements This free course is adapted from a former Open University course called 'Engineering: mechanics, materials, design (T207).' Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommerc
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