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How to Fight a Rip Tide

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Thinkstock

Getting caught in a rip current is no day at the beach. But it doesn’t have to ruin your vacation. With a few easy steps, you can slip out of a rip tide and get back to working on that tan.

1. Know Your Enemy

The best way to conquer a rip tide is to avoid it entirely. Rip tides occur when breaking waves cross underwater obstacles separated by a small gap, like a pair of sandbars, before being forced back out to sea. Rip currents can be tough to spot, but if you see breaks in waves rolling into shore, water that’s a different shade than its neighbors, or lines of particularly choppy water, swim somewhere else.

2. Don’t Fight It

It sounds crazy, but if you still stumble into a rip tide, don’t try to battle back to shore against the current. You will lose. The rip tide is stronger than you are, and the water can hit speeds of up to eight feet per second. (That’s faster than Olympic swimmers!) Fighting back against the current won’t get you anywhere, but it’s sure to wear you out.

3. Take a Parallel Path

Instead of fighting back towards the beach against the rip tide, swim parallel to the shore. Think of the rip tide as a conveyor belt that you need to get off of. Make your move for one of the edges, where the water will be behaving normally.

4. Wait It Out

If you can’t swim out of the rip current, don’t give up. Simply stay calm and conserve your energy by floating or treading water as the current carries you out to sea. Eventually, the rip tide’s pull will weaken, allowing you to swim out of its range.

5. Head Home

Once you’re clear of the rip current, it’s time to use that energy you saved. Swim back towards shore using the incoming waves to help propel you towards the beach. Take it easy swimming in, and let a lifeguard know about the rip current that caught you.
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Once you’re safely back on the sand, you will have gotten a full day’s exercise. It’s now the perfect time to sit back with an ice-cold Dos Equis and enjoy the view.

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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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May 23, 2017
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