Aart's Blog

I investigated the large variation observed in the graph of June 6. While babysitting the monitoring software, I noticed that occasionally the software would report bursts of over 200 CPM, even though the Geiger counter itself never measured such a spike. Two "faulty minutes" in one hour could easily explain the 400 clicks variation. Therefore, I first tried different serial/USB converters (settings were always as specified by the GC manufacturer), since low quality converters are notorious for messing up signals. But I noticed faulty burst even for expensive converters. Then I tried my only computer that still has a serial port. Now, no more faulty bursts occurred during several test runs. After that, I redid the 24 hours experiment. The results are shown below. A much more stable graph, reporting around 700 CPH, or .1 μSv/hour, which translates into about .9 mSv/year. I am glad I am now able to perform more reliable measurements. If anyone has suggestions on debuggi

I got a Digital Geiger Counter for my birthday (yes, I know, geeky). As a starter use, I measured the background radiation in our house in the East Bay over the past 24 hours. The results appear in the graph below, plotting the "counts per hour" and corresponding μSv/hour over the past 24 hours. The worst-case measured .2 μSv/hour translates to about 1.8 mSv/year, which luckily seems a bit below the worldwide average background dose.

We made a road trip to Mount Shasta and back to view the solar eclipse 2012, Armed with a home-made pinhole camera made by two shoe boxes, we watched the eclipse in a safe way.  

Bob Newell's The Checker Maven is a very interesting online publication on Checkers and Draughts. This week's issue features checkers applications for Android. Bob looked at many checkers programs but concluded that the only two application that merit consideration are Checkers Tutor, by world class checker programmer Martin Fierz (author of CheckerBoard and the Cake computer engine), and .... Checkers for Android by yours truly! I am honored to receive this special mention by The Checker Maven. You can find the summary article at the main page . A more elaborate overview, including interviews with Martin and myself and be found in the full article . Many thanks to Bob for posting this article.

Revisiting checkers programming, I just released version 2.5 of Checkers for Android, both at the Google Play and as direct download . New features include: simple animation of captured pieces added a slight delay in single-move response added transposition table to engine more time controls The new animation and delay will hopefully make it more clear what move was just played. The transposition table should improve the engine strength a bit. UPDATE: version 2.5.1 improves the animation as shrinking pieces (some users thought the older fading pieces were "drag delay"!), adds more endgame knowledge, and shows kings more clearly.