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CeramicsCeramics is the art of creating useful and/or decorative objects from clay.
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Ceramics is the term used for the study of ceramic materials, both in the traditional sense of pottery, and in a modern sense of oxide- or nitride-based materials.
Ceramic materials are usually hard and strong. However, imperfections in the ceramic make them brittle. Under some conditions, such as extremely low temperature, some ceramics exhibit superconductivity.
Some ceramic materials can withstand extremely high temperatures without losing their strength. These are called refractory materials. They generally have low thermal conductivities, and thus are used as thermal insulators. For example, the belly of the Space Shuttles are made of ceramic tiles which protect the spacecraft from the high temperatures caused during reentry.
A couple of decades ago, Toyota researched on producing a ceramic engine which can run at a temperature of over 6000°. Ceramic engines do not require a cooling system and hence a major weight reduction in fuel-efficient vehicles. Fuel efficiency of the engine is also higher at high temperature. In conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Despite all the desirable properties, such engines are not in production because the manufacturing of ceramic parts is difficult. Imperfection in the ceramic leads to cracks. Such engines are possible in laboratory research, but manufacturing difficulties prevent them from becoming reliable products.
Most ceramics must either be processed at high temperatures or by chemical methods. A common form of ceramic processing is Sintering a method of forming ceramic objects by mixing a ceramic powder with a binder and water to form a slurry, Spray Drying it, compressing the spray dried powder in a mold to form a "Green Body, and then heating it until atoms from the ceramic particles have diffused from one to another forming bridges between each particle and its neighbors.
permissions are set.html">set.html">set.html">set up for an ftp.html">ftp.html">ftp.html">ftp.html">FTP session to write to a remote
specify a different name for the file.html">file.html">file on the remote system.
ascii.html">ASCII vs binary.html">Binary
In the example above, the file newthisweek.Z was transferred, but
transfer.html">transfer (the default), certain characters are translated between
files (those containing non-ASCII characters) are transferred, this
program---a few changed characters can render it completely useless.
To avoid this problem, it's possible to be in one of two modes---ASCII
What's on the remote system is precisely what's received. The
200 Type set to A. (Note the A, which signifies ASCII mode.)
ftp> binary
Note that each command.html">command need only be done once to take effect; if the
binary mode (that is, unless ascii is typed later).
The transfer of newthisweek.Z will work if done as:
ftp> binary
ftp> get newthisweek.Z
150 Opening BINARY mode data connection for newthisweek.Z (42390 bytes).
local: newthisweek.Z remote: newthisweek.Z
Note: The file size (42390) is different from that done
in the listing of UUNET's top directory. We can be relatively sure
transfers using wildcards to get several files, or a whole set of
example, to get all files that begin with the letter f, one
consult a local manual for more information on wildcard matching
mget or mput operation. You'll often need to get a whole set of
right. In that case, use the prompt command to turn the queries off.
ftp> prompt
be issued again.
Joe Granrose's list.html">List
(Usenet News) an extensive list of sites offering anonymous FTP
.
On
wordlookup.net
All is still licensed under the GNU FDL.
It uses material from the wikipedia.
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