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Cheetah vs. Leopard: What's the Difference?

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AFP/AFP/Getty Images

Editor's Note: Earlier this week, reader Caitlin Rogers asked, "I was planning on being a cheetah for Halloween and I've come up with a cheetah print dress, leopard print ears and tail, and a cheetah print clutch. The spots look the same to me. What's the difference between a cheetah and a leopard?" To prevent a Halloween faux pas, Matt Soniak is here with a special edition of 'What's the Difference?'

The Dilemma: You want to be a cheetah for Halloween. You do NOT want to be confused for a leopard.

People You Can Impress: Biologists, African tribes.

The Quick Trick: It's all in the spots. Cheetahs have simple black spots, while leopards have a more complex pattern.

The Explanation:

Both cats can be found across Africa, the Arabian Peninsula and southern Asia, and when encountered, both really just look like a scary mass of spots and teeth. When viewed from a safe vantage point, though, there are a number of physical and behavioral characteristics that set them apart.

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A cheetah, at left, and a leopard.

Cheetahs have solid black round/oval spots and black "tear lines" that run from the corner of their eyes down the sides of their nose to their mouth (the lines keep sunlight out of the cheetahs' eyes while hunting). They're also lankier than rest of the big cats and have smaller jaws and longer tails. They hunt during the day and rely on bursts of speed (up to 75mph over short distances). When walking and running, they pace, moving their two left legs and then their two right legs. Unlike leopards and other big cats, they can purr while they inhale, but can't roar.

Leopards have more complex spotting pattern of clusters of black and brown spots which look like roses, called rosettes. This pattern simulates shifting plants and shadows, providing camoflage as the leopards stalk their prey from tall grass and underbrush. Leopards in eastern Africa have circular rosettes, while their southern African brethren have square rosettes. Leopards are also noticeably bulkier looking than cheetahs. They're not built for speed, but surprise attacks. The extra strength helps leopards drag their prey up trees, where hide the kill to feed on at their leisure. Leopards walk using their legs in diagonal pairs (i.e. left front and right back leg, then right front and left back leg). Like the rest of the big cats, leopards can roar but can't purr except while they're exhaling.

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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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Opening Ceremony
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These $425 Jeans Can Turn Into Jorts
May 19, 2017
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Opening Ceremony

Modular clothing used to consist of something simple, like a reversible jacket. Today, it’s a $425 pair of detachable jeans.

Apparel retailer Opening Ceremony recently debuted a pair of “2 in 1 Y/Project” trousers that look fairly peculiar. The legs are held to the crotch by a pair of loops, creating a disjointed C-3PO effect. Undo the loops and you can now remove the legs entirely, leaving a pair of jean shorts in their wake. The result goes from this:

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Opening Ceremony

To this:

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Opening Ceremony

The company also offers a slightly different cut with button tabs in black for $460. If these aren’t audacious enough for you, the Y/Project line includes jumpsuits with removable legs and garter-equipped jeans.

[h/t Mashable]

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