ferent distances from the Moon, and are therefore attracted ... Moon's attraction for an element at P and the average ... effort of finding the words to express.
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Crosstalk Tides — a further explanation In the February 1987 issue of Electronics & Power we published a Crosstalk article by R. Wells on the subject of 'Tides — the real explanation'. This article provoked much correspondence to the Editor and we asked Prof. Sir Brian Pippard of the Cavendish Laboratory, University of Cambridge, to consider the original article and some of the correspondence.
Mr. Wells' article on tides has elicited a considerable correspondence from readers, which there is insufficient space to publish. His argument concentrated, quite correctly, on the important idea that it is the horizontal forces that move water over the Earth's face, and he showed in his diagram, without mathematical details, how this force arises and how it varies over the surface. What he did not make clear is that different parts of the surface lie at different distances from the Moon, and are therefore attracted differently by it. This must be taken into account in a detailed mathematical theory. Nevertheless the general picture that he presented is correct, and forms the basis of all calculations of tidal phenomena. Imagine the Earth (E) and the Moon (M) rotating about a common centre of mass C, with E and M presenting the same faces to one another. What forces act on an element of water at E's surface? The force on an element at P is made up of: F,, gravitation from Earth, which is uniform and can cause no tides. Therefore, we can forget it. F2, centrifugal force = mio2 * (distance from C to P) if element of water has mass m and the whole system has angular velocity co. F3, gravitation from Moon. Now F2 can be dissected into F2' + F2", of which F2' is constant, independent of the position of P, and F2" is radial and,
like the Earth's attraction, incapable of producing tides. It is F2 which is balanced by the Moon's attraction to keep the Earth and Moon in stable orbit about C.
So we can forget centrifugal effects as producers of tides. What we are left with is the difference between the Moon's attraction for an element at P and the average attraction, i.e. for an element at O. At some point like Q, the Moon's attraction is the same as at O, though differently directed. The difference between these forces is radial and has no tendency to move water. Nearer the Moon than Q, the Moon's attraction is stronger and pulls water towards M; further away it is weaker and the water is accordingly pulled away from M. PROF. SIR BRIAN PIPPARD
0
Engineering your own improvement It has become fashionable to reproach British managers and engineers for their tendency to shun formal training. In view of the investment it requires in time and money, as well as the uncertain yield on that investment one can understand their reticence. Yet there is a simple means of reconciling their inclination for 'on-the-job' learning and the need for a more systematic approach to improving performance — the answer lies in the use of a personal diary. Too long regarded in narrow terms of private gratification, the potential of diary keeping in the professional context remains largely untapped. Noting one's thoughts, feelings and ideas on a regular basis can prove an invaluable aid to managerial performance. The very act of commiting thoughts to paper results in a number of immediate benefits. Not least of these is the consequent release of stress. The therapeutic value of writing down one's preoccupations is well known — diary keeping is analogous to graffiti writing in its liberating effect. The diary provides an ideal outlet in moments of exasperation — an opportunity to vent those irritations which, if kept pent up, provoke a fixation out of all proportion to their importance. The diary enables one to let off steam in private. As a corollary to stress relief, the diary can also be used to monitor symptoms of stress such as stomach pains, headaches or simple irritability. Over time this record should help to pinpoint the major stressors in one's job — and having identified them, will increase one's control over them. Another advantage accrues from the effort of finding the words to express one's preoccupations — the reflection and precision demanded will, in themselves, help define those concerns more clearly. It is far easier to handle a problem once it is articulated, as its translation into written form necessitates breaking it down, reorganising it and rendering it coherent. Simultaneously, one casts aside those peripheral issues which, in the chaos of one's mind, have grafted themselves onto the core problem. As a result, a leaner, more 'tangible' problem emerges from the previously weighty and amorphous mass. In fact, the mere process of description may be enough to prompt a ready-made solution. What's more, by verbalising one's thoughts, they become clearer and spring readily to mind in subsequent conversation. Thus the diary might be used to prepare for a meeting. By jotting down alternative scenarios and thinking through the likely arguments one's advocacy will be all the more powerful and convincing. Instead of searching for words, the 'set phrases' will trip lightly off the tongue, allowing more time to think — and enhancing one's influence in the decision-making process.
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The diary also provides muchneeded perspective as it forces the manager or engineer to stand back from the operational difficulties of the day. The individual assumes a 'schizophrenic' participant/observer mentality and, as a result of the artificial distance created, adopts a more reflective approach — the day's activities will no longer be viewed in terms of memorable offensives; there will be a new-found awareness of the less dramatic actions: threats warded off, fears allayed, conflicts averted . . . Clearly then, there are several instantaneous benefits to be derived from the process per se, but there are more lasting benefits stemming from an analysis of the 'product'. The possibility of referring back to past entries allows one to judge one's judgment in the light of experience; to eavesdrop on one's thinking at a time when only a partial view of the situation was available. Careful scrutiny of the entries over time may reveal significant traits — possibly a tendency to make hasty decisions or to delay excessively when embryonic manifestations of a problem were noted earlier. Unmodified by the distorting lens of hindsight, the daily entries will bring to light the haphazardness of events, the fragmentation of problems and the intuitive way in which they are tackled. of The self-deluding veneer contemplation and rationality which shroud decisions in retrospect will be laid bare. The result will be greater understanding of the job and a greater insight into one's own behaviour. Increased self-awareness is the first step towards reinforcing strengths and eliminating weaknesses. Moreover, if the adage about learning from one's mistakes is to prove more than an empty boast, then some conscious effort must be made to keep a record of mistakes. It seems to be taken for granted that learning and failure are natural partners — but this is true only for as long as the memory decides to retain the lesson. The diary will help to ensure that experiences are accumulated and that errors are not repeated — that several years' experience amounts to more than one year's experience several times over. Finally, in practical terms, the diary can provide a useful back-up for the memory on technical points, on personnel matters or even for purely anecdotal purposes. A further source of interest lies in the possibility of testing out one's predictive ability without having to expose one's hopes or apprehensions to another party. As an aid to management development, the diary has several merits; notably the fact that it is neither costly nor intrusive. It puts the onus for improvement squarely on the individual and supplies the means (in other words, the mental detachment) by which to critically examine one's actions and motives. Above all though, the diary approach is a product which is adapted to its market — a population which is unconvinced by conventional training and favours experienced-based learning. For these pragmatic managers and engineers it may prove a worthwhile self-development tool. JEAN-LOUIS BARSOUX
Letters Engineers and pay Dear Sir — I had B. Pearce's problem (April 1987 E&P, p.233) 30 years ago and fortunately solved it very quickly. I became part of the original 'Brain drain'. May I recommend this strategy which I and 30-40 other engineers used at that time when we emigrated to join Westinghouse Electric at Baltimore, USA. While we nearly all left the UK and other European countries for higher pay (at least double) and half the taxes, we discovered the work was far more interesting and challenging than we had experienced in the UK. For example, I have worked on spread-spectrum systems, payload system design for IV and almost all the satellite systems designed by Ford Aerospace. During this time I travelled to Europe visiting the UK, Italy etc. I was very surprised to meet several British engineers working in Italy who were there because of the better pay and respect they commanded. My advice to Mr. Pearce, and others
like him, is do not fight what you cannot change. Go elsewhere where you will be respected and when asked, 'What do you do?', you may be able to answer, 'I am an Engineer at Ford Aerospace, designing satellite systems'. No one will mistake you for a heating engineer — do you note the difference? There was another engineer among us who did not leave the UK, per se, for more money. He left because no one would recognise his ability despite an honours degree from Kings College in maths. His problem was that his accent was from the East End of London. At Westinghouse he quickly became head of the mathematics department. If B. Pearce or any other readers have questions about the United States they are welcome to write to me. — Yours faithfully, B. PEGG (F) 26, Avenue de la Resolution Cite Marine de Port La Galere 06590 Theoule-sur-Mer, France 5th May 1987
THE JOURNAL OF THE INSTITUTION OF ELECTRICAL ENGINEERS
IN RETROSPECT 25 years ago Only one-third of the working population in the United Kingdom is employed in manufacturing, and a fractional increase in productivity in manufacturing contributes only one-third of that fraction to the standard of living. The scope for automation in industries like agriculture and in services like distribution, transport, medicine and teaching is therefore an important matter. The immediate prospects for progress are limited, with one important exception, namely the replacement of routine clerical labour by data-handling machines and by computers. This tends to be useful when units of operation are large and favour an increase in scale. The conclusion that emerges from these considerations is that the technical possibilities of product-cheapening by automation are restricted by existing economic structures and by .psychological habits. If economic changes facilitated faster progress, the possibilities might still be restricted by a shortage of technologists having the necessary breadth and imagination. Such developments are always restricted by the availability of capital, associated with the risks present in a rapidly changing and somewhat disorganized world. — from A. Tustin: 'Is automation making satisfactory progress?', June 1962
50 years ago It is well known that it is possible to control the variations in intensity of radio signals in long-distance communication by combining the effects of two or more signals which have been transmitted on adjacent frequencies. T.L. Eckersley has advocated the use of multi-frequency transmissions and has outlined a simple theory by which the optimum frequency separation can be calculated, it being shown that the path-lengths of the received sky rays determine this quantity. In the application of his system to the beam telegraphic services, however, the true criterion of optimum frequency separation seems to have been overshadowed by the need for selecting frequencies whose separation was appropriate to the decrements of the tuned circuits in the receiver and to the telegraphic speed required. Under these somewhat arbitrary conditions, Wells found that a modulated carrier generally gave better results than an unmodulated one but that the reverse might be the case when the fading was slow. — from A.L. Green and G. Builder: 'Control of wireless signal variations', June 1937
