I have not been understanding the discussion of solving percolation problems by punching holes in conductive paper. My problem is this: One is typically looking for the critical probability, a phase boundary at which (among other things) the modeled material changes from a conductor to an insulator. But on the insulator side of this transition, the paper will physically fall into separate pieces! Rather than go to the trouble of acquiring conducting paper and putting a voltage across it, why not just pull gently on opposite edges and see if it comes apart? I don't see how insulation can be achieved without physically disconnecting the material. Perhaps a more perspicacious funster can resolve my difficulty. On Wed, Feb 12, 2014 at 4:45 PM, Tom Knight <tk@ginkgobioworks.com> wrote:
Real 20th century engineers used Teledeltos paper, not carbon paper. See this article, and the comments about Bob Widlar, probably the best analog electrical engineer ever (well, maybe Faraday...). Google still thinks you can buy it in the UK. http://electronicdesign.com/analog/whats-all-teledeltos-stuff-anyway
On Feb 12, 2014, at 4:34 PM, meekerdb <meekerdb@verizon.net> wrote:
When I sailed to Cuba a few years ago the Harbor Master came aboard to fill out paper work. He needed three copies but he only had one (used) piece of carbon paper so he had to fill out two by hand.
Brent
On 2/12/2014 6:55 AM, Henry Baker wrote:
Perhaps it would be difficult to reproduce this experiment today.
Is it even possible to purchase carbon paper anymore?
I heard a program on NPR (Planet Money, perhaps?) where they said that the last bastion of carbon paper was India, where the govt still records lots of official stuff typed on paper with carbon duplicates/triplicates/...
At 02:25 PM 2/11/2014, Richard E. Howard wrote:
The most fun paper in this field (in my opinion) is by Last and Thouless in 1971.
In this era of Higgs Boson-sized experimental budget, it is a study in elegance. They punched carefully randomized holes in carbon paper (2D conducting sheet) and measured the resistivity as a function of hole density.
The experiment trumped the theory at the time and the apparatus (for once) actually cost less than the pencil/paper theory...
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