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The Quick 10: 10 Pieces of Stolen Artwork

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August 22 is a bad day for artwork: on this day in 1911, it was discovered that the Mona Lisa was stolen, and on this day in 2004, two Edvard Munch paintings were stolen at gunpoint from a museum in Oslo. So, it makes sense to me that today's Q10 should be about famous works of art that were snatched out from under the collective noses of museums.

1. The Mona Lisa, 1911. After movies with incredibly complicated plots to steal art, like The Thomas Crown Affair and Oceans 12, it seems almost unbelievable that an employee at the Louvre just strolled out with the Mona Lisa stashed under his coat. But that's what happened. He kept it in his apartment for a couple of years before attempting to sell it to the Uffizi Gallery in Florence. He was caught and served a few months in jail for his crime.

2. The Gardner Museum, 1990. A total of 13 pieces were stolen from Boston's Gardner Museum, including a few Rembrandts, a Manet, a Vermeer and five drawings by Degas. The total value of the pinched items is about $500 million. If you know anything, there's a reward of $5 million.

jacob3. The Jacob de Gheyn III, 1966 (among others). This Rembrandt is the most stolen painting in the world "“ it's gone missing four times to date. It keeps turning back up, though, and is living (for now) at London's Dulwich Picture Gallery. The fact that it's barely bigger than a piece of typing paper "“ 11.8 by 9.8 inches "“ certainly makes it easier to steal than most famous works.

4. The Van Gogh Museum, 1991.

Twenty of Van Gogh's most famous works were stolen from his namesake museum in Amsterdam, but were quickly found about 35 minutes later in an abandoned car. I guess the thieves lost their nerve(s).

5. Emile Bührle Foundation, 2008. A similar theft happened just earlier this year, this time in Zurich. Works by Monet, Degas, Van Gogh and Cézanne were taken from the Foundation, for a total of $163 million in missing masterpieces. However, the Van Gogh and the Monet were found not too long after the theft in a parked car near the museum.

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6. Ghent Altarpiece panels, 1934. Two panels of the altarpiece were stolen and held for ransom. One of them was found, but the thief died before the other one could be safely returned and never told anyone its location. It's still missing to this day.

7. The Scream and the Madonna, 2004. Edvard Munch's pieces were famously stolen in Norway. An alarm went off when the thieves broke in, but the guard ignored it. I guess they were well-mannered thieves, because they left a note thanking the guard for his poor security.

8. Last Judgment triptych, 1473. Art theft is definitely not a recent phenomenon. An altarpiece like the Ghent panels, the Last Judgment was stolen from the de'Medici chapel in Florence. It's not lost, though "“ the thief gave it to the Gdansk cathedral in Poland. It was moved to the museum in Warsaw in the 1940s, but I believe it has since been returned to the cathedral.

9. The Duchess of Devonshire, 1878. The theft of this Gainsborough piece is kind of funny, I think "“ it was stolen so the thief could demand his friend's release from jail. Except, his friend has already gotten out of jail. Whoops. He made lemonade out of lemons, though, and demanded a ransom instead.

10. Quedlinburg medieval artifacts, 1945. During WWII, a soldier stole eight artifacts from a mineshaft "“ they had been hidden there by clergy members who feared that Nazis would steal them. He was still in possession of them when he died in 1980 "“ when his brothers attempted to sell some of the items in 1990, they were charged. That statute of limitations had passed, though, so the brothers were let off the hook.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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