Unfair Coin Tossing


Suppose you want a fair coin, one that yields heads and tails with equal probability, but only have a bizarre coin that yields a side more often than the other. Can we remove the bias?


John von Neumann gave us a surprisingly simple procedure to remove bias from a coin and yield a fair toss.

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Building a Book Scanner (Part II: Tray)


Last week, I showed how I built the lectern for my book scanner prototype. This week, let’s have a look at the tray holding the glass needed to keep the book evenly opened.


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Building a Book Scanner (Part I: Lectern)


I’ve been thinking of making my own book scanner for a while now. Since only thinking about something doesn’t get you anywhere, I’ve actually started building it.


But before we get to the building of the device—still in progress—let me explain by design goals. The first and foremost goal is that the scanner has to be book-friendly. If you’re going to destroy the book, you might as well use a bandsaw and cut its back off, and use a paper-feed scanner of some sort. So to avoid damage, the lectern on which the book will rest has to be soft, and avoid the need to split the book open.

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I’ve been using fountain pens for a long time, but I only recently began to appreciate ink. Yes, there are more colors than black and blue-black.


One of the more difficult thing is to choose a color that actually pleases you. Of course, you can browse online stores to get ink, but the colors presented in the swatches are not all that fateful to the actual color you will get out of your fountain pen. Sometimes you have a nice surprise, sometimes you’re disappointed.

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