2.1 Environment and technology A central concern of environmental studies is the relationship between technology and our environment: how people use technology to transform materials into forms which can meet our needs and wants. In the process of doing this we inevitably change the environment which provides these materials but which also supports all life. A few moments ago I went to my fridge and took some milk out to add to a cup of coffee. I used this common example of a modern domestic appliance without a secon
6.1 Introduction The international level can be viewed as an arena of politics in its own right and not just as a context for states and other actors. If we think of the international world in this way, how should relations between states, and other actors on the international stage, be constructed? To what extent should those relations be regulated? We can ask whether relations between states, and states' policy making, should be dictated by allegedly universally shared human rights principles, or by other o
2.1 Issues of responsibility The aftermath of the 2004 Indian Ocean tsunami saw an unprecedented aid effort to assist the affected regions. In the early days after the disaster, pledges of financial assistance from overseas governments were often outstripped by the generosity of their own populaces. This was a case when ordinary people around the world saw and were moved by the tragic circumstances of others far away (Rose, 2006), and they responded with gifts of money and provisions, and even with offers of their own sk
Module team Gillian Rose, Professor of Cultural Geography Chris Brook, Senior Lecturer in Geography Peter Jackson, Professor of Human Geography, University of Sheffield
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1.6 Defining global markets Global markets for manufactured goods, as opposed to, say, primary commodities such as oil and timber, arose largely in the second half of the twentieth century as trade between countries intensified. The lowering of transport costs and the relative fall in trade barriers enabled firms in one country to compete wit Introduction This unit interrogates the idea of a globalised world by showing how inequalities in access to material wealth and expectations of lifestyle, which have been created historically between the US and Mexico, produces border tensions as Mexicans seek entry to the US to do jobs that resident American citizens will not undertake for the wages offered. It is particularly relevant currently in the context of debates about free trade and movement of workforce to where they could find work, and that 1.1 Aim The activities and resources in this section engage you in an interdisciplinary investigation of your personal ecology by looking at a range of temporal, spatial, and organisational scales – from the personal to the global, from the short term to the long term. The aim is to gather evidence to he 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 1.1 Aim This study unit introduces you to the proposition that our mental models change through learning, and 5.1 Sudden changes The third category of thermal effects identified in Section 2 are those associated with sudden changes. Here are some technically important examples where things change suddenly at a particular temperature: Pure water boils at 100 °C (at atmospheric pressure).< 4.4 Summary of Section 4 Thermal energy is a random thing, so any group of particles possessing it will have a distribution of kinetic energies. The fraction of particles with energy greater than an amount E1 is proportional to exp(−E1/kT). Thermally activated rates follow Arrhenius's law and are characterised by an activation energy. Diffusion in solids and electrical conduction i 4.3.3 Getting at the activation energy The final trick I want to show you with Arrhenius's law is how to extract the constants r0 and Ea from experimental data. If the Arrhenius equation (Section 4.3.1) is ‘turned inside out’ by taking natural logarithms of both sides it becomes: 2.2 Thermal effects in outline Temperature is, of course, the measure of ‘thermal’ conditions. Nowadays it is measured by thermometers and expressed as a number on an agreed scale. Some features of thermometers and of their use are discussed in Thermometers and process control
The theoretical construct of temperature relates it to the kinetic energies of atoms. This gives clear insights into the way temperature affects the behaviour of materials. Energy is given to things to make them hot and taken 7 Summary Polymers are long chain molecules with properties dominated by their chain behaviour and the nature of their chemical make-up or constitution. The distinction between thermoplastics and thermosets has become rather blurred with the development of new materials for more demanding environments than previously. They include high performance polymers which are more resistant to high temperatures, possess greater moduli or strengths, and can be combined with additives to enhance their intrinsic pr 4.3.4 Ionic polymerization Free radicals are indiscriminate in the compounds they attack, and their non-selective nature in polymerization reactions leads to problems such as chain branching and transfer which affect the structure of the polymer produced. Anionic polymerization overcomes many of these problems. A typical commercial (but also see Box 8 4.3.2 Propagation Once a small number of chains have been started, propagation involves successive addition of monomer units to achieve chain growth. At each step the free radical is regenerated as it reacts with the double bond. So in the case of styrene the propagation step is
The free radical can also add on in a 4.3.1 Initiation Initiation is the mechanism which starts the polymerization process. Vinyl monomers are quite easily polymerized by a variety of activating methods. Styrene, for example, can be converted to solid polymer simply by heating, and ultraviolet light can have exactly the same effect. Usually, however, an activating agent is used. This is an unstable chemical which produces active species that attack the monomer. A good example is benzoyl peroxide which splits up when heated:
Author(s): 5.2 The aims and principles of system engineering The aims of systems engineering can be divided into those to do with its outputs and those associated with the process itself. As far as its outputs are concerned, systems engineering aims to ensure that: the requirements of all the stakeholders are taken into account in engineering the system the system, as engineered and realised, meets the requirements of stakeholders the system, while meeting the req Stage 4: Conceptual model The conceptual (or activity) model contains all the activities that the relevant system would have to perform. The model is usually drawn as a block diagram. Introduction This unit is from our archive and it is an adapted extract from Digital Communications (T305) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area. By using optical fibre, very high data rates (gigabits per second and higher) can be transmitted over long d
