9.7 Control-model diagrams Perhaps, like me, you are beginning to form the view there were some ambiguities about purpose in the case-study situation. Control models are a useful way of investigating purpose and the means in place to achieve it. They address issues like ‘What is X trying to achieve?’ ‘How are they trying to do it?’ and ‘How will they know when they've done it?’ Control-model diagrams provide a structure for exploring these questions. The drawing of the model allows you to decide whet
8.2 Stakeholder traps I've found it's not at all uncommon to discover I have a stake in a situation. Complex situations often spread their tentacles into all sorts of areas, so that the number of people touched by them can be very large. This increases the chances of an individual acquiring a stake, even an indirect or second hand one. The human capacity to empathise draws me into a situation so that I form pre-judgements about fairness, blame and so on without really trying. In many ways this is to be welcomed â€
2.5 Review The title of this unit could have been Juggling with complexity: searching for system. This title seemed to capture something essential about the unit. Juggling is a rich metaphor and will be used explicitly in Part 3. But it also carries the idea of a skill that needs to be practised and that might seem incredibly awkward to begin with. You may find this idea helpful as you review your work in Part 1. Juggling is also a skill that, once practised, becomes second nature. This too may b
2.3 Taking responsibility for your own learning Not much of this unit conforms to the traditional pattern I mentioned earlier – the theory-example-exercise pattern. In particular, you will find you are expected to discover much of it for yourself. Why is this? This is a legitimate question and deserves a full answer. One year, a student at a residential summer school complained I had not taught him properly. I was, he told me, an expert and so why did I not demonstrate how to tackle the problem he was working on and pass my expertise on
3.2 Learning by experience It's a familiar idea but it implies two activities: learning and experiencing. Both activities need to happen if I am to say that learning from experience has happened. Experiencing seems to have two components. The first is the quality of attention that allows me to notice the experience and its components. The second is memory. Calling experience to mind allows me to examine the experience and to think about it in ways that were not possible at the time. Learning is what I take away from th
3.1 What are you hoping to learn? Anticipations and preconceptions are an important determinant of how people learn, so before you read on, I would like to you to record some of what you are experiencing now as you begin the course. It's important to get these impressions noted down now, because new ideas and new impressions will quickly overlay the experience. What you are experiencing now will be re-interpreted as new understandings emerge. You are also likely to form some judgements about your expectations. So before
2 Part 1 Starting the unit Welcome to T306_2 Managing complexity: a systems approach – introduction. As I write, I experience a sense of excitement. For me, as for you, this is the beginning of the unit. These are the first few sentences I'm writing and so, although I have a good idea of how the unit is going to turn out, the details are by no means clear. Nevertheless, the excitement and anticipation I, and maybe you, are experiencing now is an important ingredient in what will become our experiences of the u
10.9.2 New technology The appearance of a new technology often results in the possibility of developing a whole range of new products. The invention of the transistor in the USA by Bardeen, Brattain and Shockley in 1947 led to a vast market of improved consumer electronics goods such as portable radios, hi-fi and television. Later on, the related inventions of the integrated circuit in 1959 (by Jack St Clair Kilby at Texas Instruments) and the microprocessor in 1971 (by Marcian E. Hoff at Intel) allowed the develo
10.7.2 Follow the leader Some companies have a defensive strategy and aim to follow the leader. Such companies hope to profit from the mistakes of the first-to-market company by devising incremental design and performance improvements and cost reductions compared with the original product. In addition they hope to exploit the new market that has started to grow, so timing is important. In the area of consumer electronics, for example, most of the inventions (radio, television, audio and video tape recording) w
7 Ergonomics and human factors This section discusses designing for human capabilities and limitations. It introduces the study of ergonomics which can offer general guidelines as well as specific suggestions for good, user-centred product design. Taking the user as the central point of reference for the design and evaluation of products is the approach encouraged by ergonomists. The field of ergonomics (also known as human factors engineering) is the systematic study of human capabilities, limitations and requ
5.14.3 Electrodialysis Electrodialysis is an electrochemical process in which ion transfer separates salt from water. It is effective only for substances that can be ionized: for example, salt (NaCl) becomes, in solution, a mixture of Na+ and Cl− ions. (Silica, on the other hand, does not ionize and hence is not removed by electrodialysis. It could, however, be removed by reverse osmosis.) When electrodes, connected to a suitable direct current supply, are immersed in a salt solution, curren
5.14 Desalination In many parts of the world, surface water or non-saline groundwater stocks are not adequate to satisfy the water demand. While one may immediately think of the Middle East as being one such area, it is less obvious that many islands (e.g. the Canary Isles, Madeira, the Channel Islands) also suffer the same problem. In such circumstances, people have been forced to consider the sea and brackish underground aquifers as water sources. To make these saline waters potable, the salt has first to be
5.8.1 Nitrate removal Nitrate in water has become a significant problem and the EU Directive sets a maximum admissible concentration of 50 g m−3 measured as NO3−. This is equivalent to 11.3 g m−3 as N. High nitrate levels can cause cyanosis or methaemoglobinaemia in babies. Legislation allows the designation of nitrate-vulnerable zones and these help to prevent nitrate levels in natural waters increasing in affected areas.
Ion exchange is used in some
3.4 Chemical characteristics of natural waters Since water is such a good solvent, it is not surprising to find many different chemical substances present in it. Water, on reaching a river, will contain inorganic and organic compounds which were dissolved as rainwater percolated through the soil and rocks. In addition, some gases will dissolve in rainwater during its passage through the air. The substances present in water may be conveniently grouped into: those from dissolved gases such as
3.3.3 Temperature All aquatic organisms have a fairly well-defined temperature tolerance range and this determines their distribution. Temperature affects the saturation concentration of dissolved oxygen (as seen in Table 2). An increase in water temperature will reduce the oxygen solubility as well as increase the metabolic activity of aquatic organisms. The combination of these two effects means that oxygen demand by organisms increases just when oxygen supply is being reduced. Coarse fish such as perc
3.3.1 Turbidity, colour and suspended solids As water runs off the land, there are some substances which do not dissolve but are taken along as
suspended solids. Then, depending on their sizes and the velocity of the river, the solid particles may settle out at a certain point or be carried on further. Quantities are affected by seasonal changes and tend to be higher in winter because of increased storm
runoff
due to higher rainfall and melting snow. The quantity of suspended solids (measured in g m<
3.2 Dissolved oxygen Organic and inorganic nutrients are the basic food supply essential for maintaining the plants and animals in natural watercourses. Equally essential to aquatic life is a supply of oxygen, needed for respiration. Oxygen dissolved in the water is also needed in the biodegradation of organic matter by aerobic (oxygen-consuming) bacteria. A measure of this
oxygen demand
can be obtained experimentally and is defined as the
biochemical oxygen demand
(BOD). The BOD i
3.1 Water, the medium of life The list of necessities for the provision of life includes various nutrients and water: water is one of the basic resources needed for the process of photosynthesis. Since it is an excellent solvent, water, even in its ‘natural’ state, is never pure H2O but contains a variety of soluble inorganic and organic compounds. Water can also carry large amounts of insoluble material in suspension. The amounts and types of impurities vary with location and time of year, and determine so
2.11 Storage In a given fixed space at any phase of the hydrological cycle, there is an inflow and an outflow of water, the rates of which vary with time. The total cumulative difference between inflow and outflow is the storage. So within that space there is a body of water whose mass is not directly controlled by instantaneous values of inflow and outflow. For example, in river flow the movement of the whole body of water in the channel is generally downstream, yet a given reach contains a volume whose
2.10 Aquifers
Groundwater
is water that, after infiltrating and percolating through surface soils, flows into an
aquifer, an underground water-bearing layer of porous rock. About one-third of the UK's drinking water is drawn from aquifers. To permit economic development, an aquifer must be able to transmit large quantities of water from one point to another and therefore it must have a high permeability. The groundwater contained in aquifers is released from springs an
