• 37………. from a random selection of four, and a 38………………
  • 39………….. or 40………….. Autoganzfeld studies 1987 41…………..
  • 45…………… (as with most ganzfeld studies). 102 READING PASSAGE 9
  • Few words to say about this book




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    THE-BIBLE-OF-IELTS-READING-BOOK

     
    Questions 36-45 
    Complete the table below.
    Choose 
    NO MORE THAN THREE WORDS
     from the passage for each answer.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
    Telepathy Experiments 
    Name/Date
    Description
    Result
    Flaw
    Ganzfeld 
    studies 
    1982 
    Involved a person acting as 

    36…………….
    who 
    picked out 
    one
    37……….
    from a 
    random selection of four, 
    and 

    38………………
    , who 
    then tried to identify it. 
    Hit-rates were higher 
    than with random 
    guessing. 
    Positive results could be 
    produced by factors such 
    as 
    39…………..
    or 
    40…………..
    Autoganzfeld 
    studies 
    1987 
    41…………..
    were used for 
    key tasks to limit 
    the amount 
    of 
    42………..
    in carrying 
    out the tests. 
    The results were 
    then subjected 
    to a 
    43……………..
    The 
    44…………
    between different 
    test results was put down to the fact 
    that sample groups were 
    not
    45……………
    (as with most 
    ganzfeld studies). 


    102 
    READING PASSAGE 9 
    Sheet glass manufacture: the float process 
    Glass, which has been made since the time of the Mesopotamians and Egyptians, is little more than a mixture 
    of sand, soda ash and lime. When heated to about 1500 degrees Celsius (°C) this becomes a molten mass that 
    hardens when slowly cooled. The first successful method for making clear, flat glass involved spinning. 
    This method was very effective as the glass had not touched any surfaces between being soft and becoming 
    hard, so it stayed perfectly unblemished, with a 'fire finish'. However, the process took a long time and 
    was labour intensive. 
    Nevertheless, demand for flat glass was very high and glassmakers across the world were looking for 
    a method of making it continuously. The first continuous ribbon process involved squeezing molten glass 
    through two hot rollers, similar to an old mangle. This allowed glass of virtually any thickness to be made non-
    stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and 
    polished. This part of the process rubbed away around 20 per cent of the glass, and the machines were very 
    expensive. 
    The float process for making flat glass was invented by Alistair Pilkington. This process allows the 
    manufacture of clear, tinted and coated glass for buildings, and clear and tinted glass for vehicles. Pilkington 
    had been experimenting with improving the melting process, and in 1952 he had the idea of using a bed of 
    molten metal to form the flat glass, eliminating altogether the need for rollers within the float bath. The metal 
    had to melt at a temperature less than the hardening point of glass (about 600°C), but could not boil at a 
    temperature below the temperature of the molten glass (about 1500°C). The best metal for the job was tin. 
    The rest of the concept relied on gravity, which guaranteed that the surface of the molten metal was perfectly 
    flat and horizontal. Consequently, when pouring molten glass onto the molten tin, the underside of the glass 
    would also be perfectly flat. If the glass were kept hot enough, it would flow over the molten tin until the top 
    surface was also flat, horizontal and perfectly parallel to the bottom surface. Once the glass cooled to 604°C or 
    less it was too hard to mark and could be transported out of the cooling zone by rollers. The glass settled to a 
    thickness of six millimetres because of surface tension interactions between the glass and the tin. By fortunate 
    coincidence, 60 per cent of the flat glass market at that time was for six-millimetre glass.
    Pilkington built a pilot plant in 1953 and by 1955 he had convinced his company to build a full-scale plant. 
    However, it took 14 months of non-stop production, costing the company £100,000 a month, before the plant 
    produced any usable glass. Furthermore, once they succeeded in making marketable flat glass, the machine 
    was turned off for a service to prepare it for years of continuous production. When it started up again it took 
    another four months to get the process right again. They finally succeeded in 1959 and there are now float 
    plants all over the world, with each able to produce around 1000 tons of glass every day, non-stop for around 
    15 years. 
    Float plants today make glass of near optical quality. Several processes - melting, refining, homogenising - 
    take place simultaneously in the 2000 tonnes of molten glass in the furnace. They occur in separate zones in 
    a complex glass flow driven by high temperatures. It adds up to a continuous melting process, lasting as long 
    as 50 hours, that delivers glass smoothly and continuously to the float bath, and from there to a coating zone 
    and finally a heat treatment zone, where stresses formed during cooling are relieved. 
    The principle of float glass is unchanged since the 1950s. However, the product has 
    changed dramatically, from a single thickness of 6.8 mm to a range from sub-millimetre to 25 mm, from a 
    ribbon frequently marred by inclusions and bubbles to almost optical perfection. To ensure the highest quality, 
    inspection takes place at every stage. Occasionally, a bubble is not removed during refining, a sand grain 
    refuses to melt, a tremor in the tin puts ripples into the glass ribbon. Automated on-line inspection does two 
    things. Firstly, it reveals process faults upstream that can be corrected. Inspection technology allows more than 


    103 
    100 million measurements a second to be made across the ribbon, locating flaws the unaided eye would 
    be unable to see. Secondly, it enables computers downstream to steer cutters around flaws. 
    Float glass is sold by the square metre, and at the final stage computers translate customer requirements into 
    patterns of cuts designed to minimise waste. 
     

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