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21 Chevenard, Pierre Antoine Jean Sylvestre
SUBJECT AREA: Metallurgy[br]b. 31 December 1888 Thizy, Rhône, Franced. 15 August 1960 Fontenoy-aux-Roses, France[br]French metallurgist, inventor of the alloys Elinvar and Platinite and of the method of strengthening nickel-chromium alloys by a precipitate ofNi3Al which provided the basis of all later super-alloy development.[br]Soon after graduating from the Ecole des Mines at St-Etienne in 1910, Chevenard joined the Société de Commentry Fourchambault et Decazeville at their steelworks at Imphy, where he remained for the whole of his career. Imphy had for some years specialized in the production of nickel steels. From this venture emerged the first austenitic nickel-chromium steel, containing 6 per cent chromium and 22–4 per cent nickel and produced commercially in 1895. Most of the alloys required by Guillaume in his search for the low-expansion alloy Invar were made at Imphy. At the Imphy Research Laboratory, established in 1911, Chevenard conducted research into the development of specialized nickel-based alloys. His first success followed from an observation that some of the ferro-nickels were free from the low-temperature brittleness exhibited by conventional steels. To satisfy the technical requirements of Georges Claude, the French cryogenic pioneer, Chevenard was then able in 1912 to develop an alloy containing 55–60 per cent nickel, 1–3 per cent manganese and 0.2–0.4 per cent carbon. This was ductile down to −190°C, at which temperature carbon steel was very brittle.By 1916 Elinvar, a nickel-iron-chromium alloy with an elastic modulus that did not vary appreciably with changes in ambient temperature, had been identified. This found extensive use in horology and instrument manufacture, and even for the production of high-quality tuning forks. Another very popular alloy was Platinite, which had the same coefficient of thermal expansion as platinum and soda glass. It was used in considerable quantities by incandescent-lamp manufacturers for lead-in wires. Other materials developed by Chevenard at this stage to satisfy the requirements of the electrical industry included resistance alloys, base-metal thermocouple combinations, magnetically soft high-permeability alloys, and nickel-aluminium permanent magnet steels of very high coercivity which greatly improved the power and reliability of car magnetos. Thermostatic bimetals of all varieties soon became an important branch of manufacture at Imphy.During the remainder of his career at Imphy, Chevenard brilliantly elaborated the work on nickel-chromium-tungsten alloys to make stronger pressure vessels for the Haber and other chemical processes. Another famous alloy that he developed, ATV, contained 35 per cent nickel and 11 per cent chromium and was free from the problem of stress-induced cracking in steam that had hitherto inhibited the development of high-power steam turbines. Between 1912 and 1917, Chevenard recognized the harmful effects of traces of carbon on this type of alloy, and in the immediate postwar years he found efficient methods of scavenging the residual carbon by controlled additions of reactive metals. This led to the development of a range of stabilized austenitic stainless steels which were free from the problems of intercrystalline corrosion and weld decay that then caused so much difficulty to the manufacturers of chemical plant.Chevenard soon concluded that only the nickel-chromium system could provide a satisfactory basis for the subsequent development of high-temperature alloys. The first published reference to the strengthening of such materials by additions of aluminium and/or titanium occurs in his UK patent of 1929. This strengthening approach was adopted in the later wartime development in Britain of the Nimonic series of alloys, all of which depended for their high-temperature strength upon the precipitated compound Ni3Al.In 1936 he was studying the effect of what is now known as "thermal fatigue", which contributes to the eventual failure of both gas and steam turbines. He then published details of equipment for assessing the susceptibility of nickel-chromium alloys to this type of breakdown by a process of repeated quenching. Around this time he began to make systematic use of the thermo-gravimetrie balance for high-temperature oxidation studies.[br]Principal Honours and DistinctionsPresident, Société de Physique. Commandeur de la Légion d'honneur.Bibliography1929, Analyse dilatométrique des matériaux, with a preface be C.E.Guillaume, Paris: Dunod (still regarded as the definitive work on this subject).The Dictionary of Scientific Biography lists around thirty of his more important publications between 1914 and 1943.Further Reading"Chevenard, a great French metallurgist", 1960, Acier Fins (Spec.) 36:92–100.L.Valluz, 1961, "Notice sur les travaux de Pierre Chevenard, 1888–1960", Paris: Institut de France, Académie des Sciences.ASDBiographical history of technology > Chevenard, Pierre Antoine Jean Sylvestre
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22 Strachey, Christopher
SUBJECT AREA: Electronics and information technology[br]b. 16 November 1916 Englandd. 18 May 1975 Oxford, England[br]English physicist and computer engineer who proposed time-sharing as a more efficient means of using a mainframe computer.[br]After education at Gresham's School, London, Strachey went to King's College, Cambridge, where he completed an MA. In 1937 he took up a post as a physicist at the Standard Telephone and Cable Company, then during the Second World War he was involved in radar research. In 1944 he became an assistant master at St Edmunds School, Canterbury, moving to Harrow School in 1948. Another change of career in 1951 saw him working as a Technical Officer with the National Research and Development Corporation, where he was involved in computer software and hardware design. From 1958 until 1962 he was an independent consultant in computer design, and during this time (1959) he realized that as mainframe computers were by then much faster than their human operators, their efficiency could be significantly increased by "time-sharing" the tasks of several operators in rapid succession. Strachey made many contributions to computer technology, being variously involved in the design of the Manchester University MkI, Elliot and Ferranti Pegasus computers. In 1962 he joined Cambridge University Mathematics Laboratory as a senior research fellow at Churchill College and helped to develop the programming language CPL. After a brief period as Visiting Lecturer at the Massachusetts Institute of Technology, he returned to the UK in 1966 as Reader in Computation and Fellow of Wolfeon College, Oxford, to establish a programming research group. He remained there until his death.[br]Principal Honours and DistinctionsDistinguished Fellow of the British Computer Society 1972.Bibliography1961, with M.R.Wilkes, "Some proposals for improving the efficiency of Algol 60", Communications of the ACM 4:488.1966, "Systems analysis and programming", Scientific American 25:112. 1976, with R.E.Milne, A Theory of Programming Language Semantics.Further ReadingJ.Alton, 1980, Catalogue of the Papers of C. Strachey 1916–1975.M.Campbell-Kelly, 1985, "Christopher Strachey 1916–1975. A biographical note", Annals of the History of Computing 7:19.M.R.Williams, 1985, A History of Computing Technology, London: Prentice-Hall.KF -
23 Thomson, Elihu
SUBJECT AREA: Electricity[br]b. 29 March 1853 Manchester, Englandd. 13 March 1937 Swampscott, Massachusetts, USA[br]English (naturalized) American electrical engineer and inventor.[br]Thomson accompanied his parents to Philadelphia in 1858; he received his education at the Central High School there, and afterwards remained as a teacher of chemistry. At this time he constructed several dynamos after studying their design, and was invited by the Franklin Institute to give lectures on the subject. After observing an arc-lighting system operating commercially in Paris in 1878, he collaborated with Edwin J. Houston, a senior colleague at the Central High School, in working out the details of such a system. An automatic regulating device was designed which, by altering the position of the brushes on the dynamo commutator, maintained a constant current irrespective of the number of lamps in use. To overcome the problem of commutation at the high voltages necessary to operate up to forty arc lamps in a series circuit, Thomson contrived a centrifugal blower which suppressed sparking. The resulting system was efficient and reliable with low operating costs. Thomson's invention of the motor meter in 1882 was the first of many such instruments for the measurement of electrical energy. In 1886 he invented electric resistance welding using low-voltage alternating current derived from a transformer of his own design. Thomson's work is recorded in his technical papers and in the 700plus patents granted for his inventions.The American Electric Company, founded to exploit the Thomson patents, later became the Thomson-Houston Company, which was destined to be a leader in the electrical manufacturing industry. They entered the field of electric power in 1887, supplying railway equipment and becoming a major innovator of electric railways. Thomson-Houston and Edison General Electric were consolidated to form General Electric in 1892. Thomson remained associated with this company throughout his career.[br]Principal Honours and DistinctionsChevalier and Officier de la Légion d'honneur 1889. American Academy of Arts and Sciences Rumford Medal 1901. American Institute of Electrical Engineers Edison Medal 1909. Royal Society Hughes Medal 1916. Institution of Electrical Engineers Kelvin Medal 1923, Faraday Medal 1927.Bibliography1934, "Some highlights of electrical history", Electrical Engineering 53:758–67 (autobiography).Further ReadingD.O.Woodbury, 1944, Beloved Scientist, New York (a full biography). H.C.Passer, 1953, The Electrical Manufacturers: 1875–1900, Cambridge, Mass, (describes Thomson's industrial contribution).K.T.Compton, 1940, Biographical Memoirs of Elihu Thomson, Washington, DCovides an abridged list of Thomson's papers and patents).GW -
24 Watson-Watt, Sir Robert Alexander
[br]b. 13 April 1892 Brechin, Angus, Scotlandd. 6 December 1973 Inverness, Scotland[br]Scottish engineer and scientific adviser known for his work on radar.[br]Following education at Brechin High School, Watson-Watt entered University College, Dundee (then a part of the University of St Andrews), obtaining a BSc in engineering in 1912. From 1912 until 1921 he was Assistant to the Professor of Natural Philosophy at St Andrews, but during the First World War he also held various posts in the Meteorological Office. During. this time, in 1916 he proposed the use of cathode ray oscillographs for radio-direction-finding displays. He joined the newly formed Radio Research Station at Slough when it was opened in 1924, and 3 years later, when it amalgamated with the Radio Section of the National Physical Laboratory, he became Superintendent at Slough. At this time he proposed the name "ionosphere" for the ionized layer in the upper atmosphere. With E.V. Appleton and J.F.Herd he developed the "squegger" hard-valve transformer-coupled timebase and with the latter devised a direction-finding radio-goniometer.In 1933 he was asked to investigate possible aircraft counter-measures. He soon showed that it was impossible to make the wished-for radio "death-ray", but had the idea of using the detection of reflected radio-waves as a means of monitoring the approach of enemy aircraft. With six assistants he developed this idea and constructed an experimental system of radar (RAdio Detection And Ranging) in which arrays of aerials were used to detect the reflected signals and deduce the bearing and height. To realize a practical system, in September 1936 he was appointed Director of the Bawdsey Research Station near Felixstowe and carried out operational studies of radar. The result was that within two years the East Coast of the British Isles was equipped with a network of radar transmitters and receivers working in the 7–14 metre band—the so-called "chain-home" system—which did so much to assist the efficient deployment of RAF Fighter Command against German bombing raids on Britain in the early years of the Second World War.In 1938 he moved to the Air Ministry as Director of Communications Development, becoming Scientific Adviser to the Air Ministry and Ministry of Aircraft Production in 1940, then Deputy Chairman of the War Cabinet Radio Board in 1943. After the war he set up Sir Robert Watson-Watt \& Partners, an industrial consultant firm. He then spent some years in relative retirement in Canada, but returned to Scotland before his death.[br]Principal Honours and DistinctionsKnighted 1942. CBE 1941. FRS 1941. US Medal of Merit 1946. Royal Society Hughes Medal 1948. Franklin Institute Elliot Cresson Medal 1957. LLD St Andrews 1943. At various times: President, Royal Meteorological Society, Institute of Navigation and Institute of Professional Civil Servants; Vice-President, American Institute of Radio Engineers.Bibliography1923, with E.V.Appleton \& J.F.Herd, British patent no. 235,254 (for the "squegger"). 1926, with J.F.Herd, "An instantaneous direction reading radio goniometer", Journal ofthe Institution of Electrical Engineers 64:611.1933, The Cathode Ray Oscillograph in Radio Research.1935, Through the Weather Hours (autobiography).1936, "Polarisation errors in direction finders", Wireless Engineer 13:3. 1958, Three Steps to Victory.1959, The Pulse of Radar.1961, Man's Means to his End.Further ReadingS.S.Swords, 1986, Technical History of the Beginnings of Radar, Stevenage: Peter Peregrinus.KFBiographical history of technology > Watson-Watt, Sir Robert Alexander
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