Monthly Archives: June 2009

The Littlest Birds: Answer on Swarming

Today Damon theorized an answer to my previous question — why big birds select V formation flying while little birds seem to prefer swarms.

The aerodynamic effects that bigger birds rely on to help reduce drag don’t help little birds that much, and more importantly thanks to the way little birds keep a roughly constant spacing in a swarm information from disturbances (like an incoming hawk swooping down) gets passed along as a wave like a traffic jam through the swarm, spreading the alert much more quickly than would be possible if each little bird had to look up and see the diving hawk.  As a result the birds can react much more quickly and hopefully stay alive!  Cool!

For more info, Damon suggests Princeton robotics, swarming & controls expert Prof. Naomi Leonard.

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Memory of the Day

Lyon

I’m going through some photos from my most recent crazy adventure — traveling around the UK and the European continent from west as Barcelona to east as Istanbul, and found this shot I took from the cab of a grocery-hauling semi.

Here I’m crossing from Lyon to Montpelier, it’s my first time riding in a semi truck (they have these crazy-comfy gimbaling seats!), I’m speaking franglais with the highly intelligent Moroccan driver who retired from an IT career to drive trucks and we’re listening to some pretty rocking music.

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This is Why Birds Fly in V Formation

Some friends and I were on the beach the other day, staring up at the sky watching pelicans and seagulls fly by in big Vs. “Did you hear that the military is considering having its planes fly in ad-hoc assembled V formation, no matter where any particular plane is supposed to land, to save fuel?” “That’s really cool!  Why does flying in V formation save fuel?”

Downwash must be involved, I thought.

Downwash is the vortex of air that shoots straight for the ground on the back of a wing. Downwash actually exists in sort of a square behind any foil moving through the fluid: Imagine a square-shaped drain in a sink, with all the water pouring in over the edges.  That’s what the air’s doing after a wing passes by — one rolling wave of air coming off behind the wing, two waves that extend backwards from the wingtips, and a fourth wave that counteracts the first one, sort of chasing after the plane.  THESE, I thought, must have the greatest effect.

Turns out that’s right! In short; the lead bird makes some vortices that curl upwards on the outside. The next bird floats on this small updraft of air. This updraft lets the bird pitch more horizontally (or reduce its angle of attack), because it doesn’t have to work so hard to try and keep the same altitude. Reducing the angle of attack significantly decreases the drag on the bird. And, this is no extra work for the first bird, because it would be producing these vortices anyway!  Hooray!

downwash

downwash in those curly clouds

Next I wanna figure out why small birds like swarms better than flying in Vs.

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Sita Sings the Blues + MonkeyLectric + Creative Commons = Win!

I work at MonkeyLectric, and one of the things I’ve been doing is trying to find good Creative Commons-licensed/free use images for MonkeyLectric’s POV bike wheel demos, so that we can make and publish videos showing what our bike wheel display can do, without fear of litigation, and it’s been a bit tough to find good images that work really well on our wheel.

UNTIL! I learned of the animated movie Sita Sings the Blues (previously posted).

It’s gorgeous.  It’s high-contrast.  The characters look great.  It’s perfect!

Here are the first test images, a couple of stills.  By the magic of shutter speed, these photos make the display look almost as good as they do in real life.

When I can find a tool to convert movies to GIFs, I should be able to upload moving excerpts to the wheel as well!  (More pictures coming soon). Click pictures to see the large version!

lake1

jazz5

shadow4

hanuman4

sun2

eyes1

PS, Nina Paley’s (who created the movie) dilemma/reasons which led to creative-commons licensing Sita are pretty interesting — there’s a good interview with her here at the internet archive. (“How Copyright Restrictions Supress Art”, ~25 mins)

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Awesome Engineering out of MITERS!

Whoah, my friend Charles just finished making this totally awesome race car shopping cart, “LolRio Kart”:

It took him about a year to build at MITERS.  Charles also works at the Car of the Future research group.  Therefore I think cars are going to be really cool in the future!

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on creating actions

“Who are you to decide to play small in this world?”

good quote by Nelson Mandela via John Gilmore

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Totally excellent new favorite Word of the Day! ratiocination

ratiocination:  to form judgments by a process of logic, reasoning.

YESSSS

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