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What's the World's Worst Smell?

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Dr. Pamela Dalton is a chatty, mild-mannered scientist—a sensory psychologist at the Monell Chemical Senses Center in Philadelphia—who just happens to have authored the world's worst smell. Her client: The U.S. Department of Defense, which wanted a world-class stink bomb, a violently potent, no-kill weapon all but guaranteed to make enemies drop their weapons and run away.

Here's how Dalton made her Frankensteinian creation, affectionately named "stench soup."

The Recipe:

Research shows that certain smells are hated in cultures the world over. Dalton surveyed the vilest odors from around the globe (fish oil factories, old toilet brushes, etc., ad nauseum—literally) and identified the key elements. Specifically, she focused on two kings of the stench world—rotting corpses and human waste—and recreated them in her lab. To these she added sulfur (that yummy rotting egg smell) and a sweet, fruity overtone. The exact recipe, of course, is a secret—we can't have Al-Qaeda running around cooking up batches of stench soup, after all—but suffice it to say that the final product smells something like a putrescent corpse lying on a mound of human excrement laced with rotten eggs and overripe fruit. Only worse.

How She Knows It's The Worst: Dalton tested her smell on volunteers. That's right—for the sake of science, people signed waivers saying that, yes, they were about to whiff something mind-blowingly, paint-peelingly hideous. Happily, all of the volunteers completed the study uninjured; Dalton says that it's very unusual for a smell, no matter how bad, to cause actual physical harm.

Why People Love Stench Soup: Once completed, stench soup got a lot of press—and a surprisingly enthusiastic responses. After reading about her creation, hundreds of people wrote and called Dalton to tell her about the God-awful smells that only she, as an expert, would appreciate.

Unsolicited "discoveries" shared with Dalton:
Burning cat poop (This person confided that, in the spirit of discovery, she had actually put her cat's poop on a lit barbeque.)
Five pounds of raw shrimp left in a vacation home over the winter
The fluid excreted by a dog's anal glands
"My mother's basement"
The socks and underwear of a guy named Gary. Wrote a friend of Gary: "All you would have to do is throw a pair of his socks in the Taliban caves in Afghanistan and I promise you they would come running out."

(For the record, last year Dalton told The Times of London that her favorite smell was diesel exhaust.)

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iStock // Ekaterina Minaeva
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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