Sunday, 2 August 2015

BARCODE

                                                                     BARCODE(1948)

The development of barcodes stemmed from comments made by a food-chain president to a dean at The Drexel institute of technology, Philadelphia, in 1948, and overhead by graduate student Bernard Silver (1924-1962). The company wanted some sort system to collect product information at the Checkout automatically, but the dean had little interest in initiating such research. Silver decided that He and his friend Norman woodland (b.1921) should pursue the solution. eventually the pair turned To a combination of movie  soundtrack technology invented by lee de forest in the 1920s and Morse Code dots and dashes; "I just extended the dots and dashes downward and made narrow lines and Wide lines out of them," said woodland.


  De forest's film included a varying transparency pattern on its edge. When a light was shined Through it, sensing equipment on the other side converted the changes in brightness into electronic Waveforms that translated into sound. Woodland adapted this system by reflecting the light off his Wide and narrow lines and coupling the sensor to an oscilloscope. They had invented the first Electronic reader of printed data. the advent of affordable, low-power, laser light sources, and "Compact" computers to process the captured data, did not occur until several years later.
 
      The first product with a barcode [chewing gum] was scanned at a checkout counter.

Saturday, 1 August 2015

MAGLEV TRAIN

                                                               MAGLEV TRAIN (1979)

Magnetically levitated (maglev) trains glide above a track, propelled by superconducting Electromagnets. the principal is more than century old, but initially the huge electrical currents Needed to provide a sufficiently strong magnetic field were impractical. The breakthrough came When two physicists,Gordon Danby and James Powell, at Brookhaven national laboratory decided to Use high temperature superconductors as electromagnets. They obtained a patient for the technology In 1968, and by 1979 visitors to a transportation exhibition in Hamburg, Germany, where enjoying a Short test run on a Transrapid maglev train.


   Maglev trains need a guiding track and the carriages flat just above it. changing the field produced By the electromagnetic guideway pulls the train along. the only friction is due to air resistance, so Extremely high speed are possible. changes in field strength can produce very high accelerations, and Much more variable track gradients can be accommodated than with normal trains, so cuttings and Embankments would not be needed.
    There are serious disadvantage to maglevs. TMhe guideways are extremely expensive, and the train Cannot be diverted from the maglev track to normal railways to take existing inner city termini.

            
   Maglev trains were introduced in the united kingdom in 1984,linking Birmingham airport to the Nearby railway station. In china, another system links Shanghai to Pudong international airport. the Success of the TGV trains that run on normal tracks, however, has reduced the appeal of maglev.