>Hi Folks!
>
>This interesting article about using sound to recycle paper many more
>times than is possible with current technologies. An excerpt from the
>article is included below with the full article being at the following
>URL;
>
>http://www.discover.com/science_news/gthere.html?article=envirscience.html
>
>Sameer Madanshetty, a mechanical engineer at Kansas State University,
>has come up with another way. He has devised a recycling procedure that
>dispenses with chemicals entirely; it also does so little damage to the
>paper fibers that pages can be reused multiple times. And all he needs
>to do it is some water and precisely controlled pulses of sound.
>
>As a sound wave travels, it creates a ripple of expansion and
>compression: a low-pressure pulse followed by a high pressure pulse, and
>so on. Tiny bubbles that can sometimes form in water and other liquids
>react to this change in pressure. The low pressure pulse expands the
>bubbles and the high pressure pulse makes them contract.
>
>With certain sound waves, the contraction caused by the high pressure
>part of the sound wave can be strong and fast enough to make the bubble
>collapse in on itself, creating a surprisingly large concentration of
>energy.
>
>Called cavitation, this process is powerful enough that it can damage
>things like ship propellers and water pipes, eventually eroding them
>away. Engineers therefore usually try to create cavitation-proof
>designs, but this goal is hampered by the unpredictable nature of
>cavitation.
>
>Madanshetty does not see cavitation as a bad thing. "It's such a
>fascinating energy manifestation, but we are removing it because we
>don't understand it and we can't control it," he says. "If you think of
>fire, any fire is devastating, but if you contain it you can do some
>good cooking."
>
>Indeed, Madanshetty has found a way to control when and where cavitation
>will occur. Along with a strong sound pulse that causes the bubbles to
>expand and contract, he uses a weaker background sound wave that
>destabilizes the bubbles so that they collapse at a lower pressure; the
>result is that they release less energy and their effect is more
>localized.
>
>When a piece of paper is placed in water, tiny bubbles are most likely
>to form around the inked parts of the page, because the ink repels
>water.
>
>Madanshetty's sound system blasts these microbubbles; when they
>collapse, they literally explode the ink off the page. "It's like
>micro-jackhammers," he explains. "It chisels away the ink and throws it
>up." The process can strip the ink from a page in a few seconds, and the
>ink particles can then be filtered out of the water.
>
>Although the bubbles have enough energy to destroy the ink,
>Madanshetty's control process keeps them weak enough that they do not
>seriously damage the paper fibers below. In most cases, the paper need
>not be mashed up to be recycled--the microbubbles erase the ink
>effectively enough that the original paper is as good as new,
>Madanshetty says.
>
>"Present practice mechanically pulps the paper, and in the churning
>process they damage the paper fibers, so it limits the recycleability to
>three times," he notes. "In this case, you are not touching the paper
>fibers at all, so the number of times you can recycle the paper would be
>endless."
>--
> Jerry Wayne Decker / jdecker@keelynet.com
> http://keelynet.com / "From an Art to a Science"
> Voice : (214) 324-8741 / FAX : (214) 324-3501
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