The ones that rolled the strangest turned out to have voids inside when cut open (with a hydrogen-cooled laboratory saw, to avoid melting the plastic while doing this). I seriously doubt the pips contributed significantly.
I'm a bit leery of the "we removed statistical anomalies" bit. They also didn't compute confidence intervals for their result, but it's been long enough since I've done a chi-squared calculation that I'm having trouble doing it too.
This is still a good argument for building a miniature x-ray tomography widget for testing dice, though };>.
It's probably more a case of equipment that *absolutely never* produces voids being expensive. Any entrained gas from melting/mixing the plastic will do it. At least, that's my best guess.
Still plotting kytteny tomography };>. The cheapest way to do it is probably to discharge a known amount of charge across a 10-20 kV spark gap (with a separation of a few mm or less, so that you strike a stable arc quickly), and put as big a CMOS image sensor as you can on the other side of the die. A CCD sensor will give you lower noise, but would be more expensive. Both will pick up x-ray photons just fine, and your gap is close to a point source if you use a needle as a cathode and have a rounded anode (so there's a tiny spot that's closest, rather than a wide area). The anode has to be fairly thin (1 mm or less if you're doing tomography of 1 cm dice). Add a not-too-imprecise way to reposition the die, and you're there.
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timeasmymeasure
no subject
Date: 2010-06-22 03:05 am (UTC)I'm a bit leery of the "we removed statistical anomalies" bit. They also didn't compute confidence intervals for their result, but it's been long enough since I've done a chi-squared calculation that I'm having trouble doing it too.
This is still a good argument for building a miniature x-ray tomography widget for testing dice, though };>.
no subject
Date: 2010-06-22 06:22 am (UTC)no subject
Date: 2010-06-22 06:32 am (UTC)Still plotting kytteny tomography };>. The cheapest way to do it is probably to discharge a known amount of charge across a 10-20 kV spark gap (with a separation of a few mm or less, so that you strike a stable arc quickly), and put as big a CMOS image sensor as you can on the other side of the die. A CCD sensor will give you lower noise, but would be more expensive. Both will pick up x-ray photons just fine, and your gap is close to a point source if you use a needle as a cathode and have a rounded anode (so there's a tiny spot that's closest, rather than a wide area). The anode has to be fairly thin (1 mm or less if you're doing tomography of 1 cm dice). Add a not-too-imprecise way to reposition the die, and you're there.
no subject
Date: 2010-06-22 07:08 am (UTC)Actually, this gets me wondering about the quality control casinos impose on their dice suppliers? I understand they're pretty strict about cards...
no subject
Date: 2010-06-22 07:22 am (UTC)