Archive for November, 2009
armstrong and buzz aldrin, get ready for some more company! in the next ten years or so , an indian astronaut will be setting his foot on moon. it has been 37 years since a man has walked on moon – but when one does again , it is quite likely that it will be a desi-naut! keep those fingers crossed.
there are three layers of protocol
at the lowest level is IP (internet protocol) , which defines the
data grams or packets that carry blocks of data from one node to
another .the vast majority of today,s internet uses version four of
the IP protocol although IPv6 is standardisednext name is TCP (transmission control protocol0 , UDP (user datagram
protocol ), and ICMP (internet control message protocol) – the
protocols by which data is transmitted. TCP makes a virtual
‘connection” which gives level of some guarantee of reliability . UDP
is a best effort, connectionless transport , in which data packets
that are lost in transit will not be resent.ICMP is a coneectionless,
it is used for control and signaling purposes.on top comes the application protocol . this defines the specific
messages and data formats sent and understood by the applications
running at each end of the communication.
…he would attented a blacks – only kindergarten. until 1954, black
children in some states in the united states of america could not
attend the same schools as white children. that year, the supreme
court finally banned seperate schools for black children
…he would have had to give up his seat and stand on the public bus
everytime a white passenger needed one.in 1955 in montgomery tennessee
, a black women called ROSA PARKS refused to give up her seat.
…he would have felt like a second class citizen of united states
of america. in1963 , a black priest called martin luther king ,
jr.made his famous “i have a dream” speach . king had lead 3 lakh
protesters to lincoln memrial in washington dc
piston engines today are mainly used to power the vast numbers of
light aircraft and microlights , as well as crop sprayers and
crop-dusters, small helicopters, and fire bombers.virtually all
heavier aircraft are now powered by by jet engines. modern piston
aero-engines work on the same basic principles as the engine used by
the Wright brothers in the first powered flight in 1903. however,
today,s engines are more sophisticated than earlier engines. for
example , modern aero- engines may use a two stroke or a four stroke
combustion cycle : they may have from one to nine air – or water
cooled cylinders, which may be arranged horizontally , in a line , in
v formation or radially :and they may drive the aircraft,s propeller
either directly or through a reduction gearbox.
when world war 2 began in 1939, air forces had already replaced most
of their fabric skinned biplanes with all metal, stressed skin
monoplanes. aircraft played a far greater role in military operations
during world war 2 than ever before . the wide range of aircraft
duties , and the introduction of radar tracking and guidance systems,
put pressure on designers to improve aircraft performance . the main
areas of improvement were speed,range and engine power. bombers became
larger and more powerful-converting from two to four engines- in order
to carry a heavier bomb load: the US B-17 Flying fortress could carry
up to 6.2 tonnes of bombs over a distance of 3,200 km. some aircrafts
increased their range by using drop tanks.fighters needed speed and
manoeuvrability : the Hawker Tempest shown had a maximum speed of
700kph and was one of the few allied aircraft capable of catching the
German jet-powered V1″flying bomb”.
the microchip or silicon chip has completely changed the color of
the electronic world by providing a new direction to it. it has lead
to the invention of electronic calculators, personal computers,digital
watches and microwave ovens.
the silicon chips are tiny crystals of silicon which contain large
number of electronic components. silicon is the most abundant element
on earth as the crust of the earth is largely made of silicon. but
silicon is not always found in free state as it always combined with
one or more additional elements. in an one sq.cm chip, about one
million electronic components can be squeezed. the size of chip is
smaller than our fingertips. they can be made to carry very small
electrical circuits
