5.3 Summary The term phase is used to refer to the part of a cycle that an oscillating system is in at a particular moment. For two sine waves of the same frequency that are not in step, one wave lags or leads the other in time. We can express the amount by which they are out of step as a phase difference. Usually phase difference is expressed as a fraction of a cycle or as a certain number of degrees (one complete cycle corresponding to 360°). If two (or more) sine waves are completely out of pha
2.2 Pressure in the atmosphere The sounds we hear generally consist of rapid fluctuations of air pressure in the atmosphere that surrounds us. Sound can also be transmitted through other media, for instance water, so not all sound consists of fluctuations in air pressure. However, for the purposes of this discussion I shall confine myself to sound in air. These fluctuations in air pressure are caused by a local disturbance to the air pressure, which might be sudden and transient – for example, when a paper bag is b
Learning outcomes After studying this unit, you should be able to: explain correctly the meaning of the emboldened terms in the main text and use them correctly in context; describe simply what a pressure wave is and give a simple explanation of sound in terms of a travelling pressure wave;
explain ‘cycle’ in terms of an oscillating source and the pressure wave it produces;
relate amplitude (including peak-to-peak and r.m.s.), frequency, period a
16.4 Managing for emergence and self-organisation It might be useful to re-read Box 4 before starting this section. In this example, the terms ‘open’ and ‘closed’ were used on several occasions. You have already encountered the term ‘closed system’. You were told that human beings are closed systems in terms of inputs to
6.3 Clarifying purposefulness Research conducted by Ralph Stacey (1993) shows how business managers often behave in a way contrary to espoused policies and expectations. Rather than adhering to conventions of long-term planning, and accepted orthodoxies and procedures, they actually tend to make a succession of unrelated, adaptive responses to changing situations as the need arises. This is often, and rather disparagingly, labelled muddle-through or crisis management but can result in adaptive action and organisation.
6.2 Modes of managing systemically Now I want to describe some of the possibilities I see as being available in the repertoire of an aware systems practitioner able to connect with the history of systems thinking and with the new theories of complexity. David Robertson, in a presentation to the Society for Research into Higher Education in late 1998 entitled ‘What employers really, really want’ reported that: ‘research on employers in a number of English-speaking countries (an elite survey with senior corporate peo
3.5 Distinctions about systems practice A tension has existed throughout the history of Western thought around whether to focus on parts or the whole. The practice that springs from this history carries the same tension. This tension has been particularly visible within science and philosophy for a long time and it gives rise to different approaches. I will be addressing these tensions in Author(s):
Part 2: 1 Introduction I have a number of purposes in mind as I write Part 2. You can read these in conjunction with Figure 4. 14 Part 2: 5 Self-assessment questions What are the four main factors that motivate individuals to invent? Individuals are motivated to invent by one or more factors: 11.3 Step 2 – exploration This is the period when, following the identification of the problem, attempts are made to understand it better and to make a stab at designing a solution. This might be a short process or it could take years and involve a detailed search for information, experimenting with different designs, even redefining the problem as a result of this activity. Alexander Graham Bell adopted a problem-focused strategy when exploring the problem of designing a working telephone. This strategy is one 10.6 What drives invention in organisations? Much invention and nearly all innovation nowadays take place inside organisations – from small start-up companies to well-established multinationals. This is mainly because increasingly invention and innovation require access to technology and resources beyond the scope of most individuals. But it is also because competitiveness and survival depend on the continual improvement of a company's products and processes. This provides a strong incentive for companies to invest in both the increme 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 Introduction Pictures speak louder than words. But how can you use diagrams to help you? This unit looks at how diagrams can be used to represent information and ideas about complex situations. You will learn how to read, draw and present diagrams to help illustrate how ideas or processes are connected.
This unit is from our archive and is an adapted extract from Systems thinking and practice: diagramming (T552) which is no longer taught by The Open University. If you want to study formally with us 12.1.1 Survey questionnaires Questionnaires are lists of questions that enable information to be gathered efficiently from a relatively large number of respondents. Most questionnaires require a fixed type of response, such as a choice between available answers, or along a scale of response. For example, a product design questionnaire might suggest, ‘I found the product easy to use’ and provide a five-point scale of response from ‘agree strongly’ to ‘disagree strongly’. Or a question might be, ‘how often do 10 User research techniques: observing users This section introduces an alternative to basing user research on yourself. This is observation of experienced and inexperienced users either in experimental or natural situations. One way around the difficulties of basing research on oneself is to observe other people acting as users and to choose naive or different kinds of experienced users, depending on what information you want to gather. Begin by identifying those experienced users who will be able to provide you with releva 9.1.1 Point of view Decide first of all which user's point of view you are taking: consumer, operator, maintenance person, and so on. You may want to make several trips, from different user perspectives, or try special user perspectives, such as that of a disabled person. It is usually easiest to take a consumer's trip because you may need special permission, access, and perhaps skills, before you can take any other. 8.1.1 Visibility Recall that a key usability design feature identified by Donald Norman – from his analysis of using everyday objects such as doors – was visibility. An everyday object such as a door, or a control such as a button on a product should appear to be obvious about how it is used, and indeed it should perform that obvious function. For example, is it obvious how you insert a disc into a player? Is it obvious how you switch the machine on, adjust volume, and so on? 8.1 Making usable products This section reveals that many modern products need to usable by our minds as much as our bodies. Products need to be understandable, and present information and feedback in meaningful ways. A lot of ergonomics research is aimed at establishing guidelines, standards or rules that can be applied by designers in a variety of situations. Where this applies to the physical use of products, much of it is based on standard body measurements. These body measurements are known as anthropomet 4 Who are the users? This section reveals that ‘users’ can include a wide variety of people – not just the final purchasers or consumers of a product. The section also makes the case for strong user representation in the design process. Of course, it is not only me who uses the various products in my home; other people use them as well, both members of the family and visitors. Sometimes the range of users of a product, and their different needs, can be diverse. And in addition to the obvious or intend 5.7.1 Mixed oxidant gases system This is a relatively new system of disinfection. It involves electrolysis of high-purity NaCl brine to produce a mixture of chlorine dioxide, ozone and hypochlorite. This mixture is separated within the electrochemical cell by a membrane, or by exploiting density difference, and is then metered into the water requiring disinfection. The mixed oxidant gases are generated on demand and this is a great safety advantage, compared with having storage tanks of chlorine on site. The source for the d
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