Archive for March, 2012

Photo by flickr user tobyct used under Creative Commons License

Aircraft were first extensivly used for war during World War I,  but until the implementation of radar nearly thirty years later the only early warning system for aircraft attacks was listening.  The unaided human ear isn’t keen enough to be especially helpful, so lots of people put lots of effort into advancing the science of acoustics.  The result of all that work was the acoustic mirror.  Acoustic mirrors work similarly to the external part of the human ear but on a much larger scale.  They are large devices shaped so that they reflect and focus sound waves so that they can be more easily heard.   It’s a method used by modern day parabolic microphones and satellite dishes.

Note the use of different shapes. (From Wikipedia Commons)

The British built an impressive system of acoustic mirrors for coastline defense along the English Channel before World War II.  These mirrors consisted of large structures built of concrete.  There were several different shapes as the British experimented with the best design, but each shape reflected sound waves and focused them in a particular area where a microphone or human listener could be located.  Focusing the sound waves allowed listeners to hear aircraft much farther away than the unaided human ear and gave the defenders a little more time to call up their own aircraft for defense.  If placed properly multiple acoustic mirrors could be used to determine an approximate distance and location for the incoming aircraft through a triangulation process similar.  The British acoustic mirrors were rendered obsolete when radar was successfully implemented, but several are still in place along the Channel coastline as the below satellite images from Google Maps show.

Image via Google Maps

War tubas from Wikipedia Commons

The Japanese had a similar, more mobile, system humorously called ‘war tubas’.  I’m not going to try and describe them, the picture speaks for itself.  The picture is mostly laughable at this point, but it was serious business 80 years ago as you can judge by the presence of the large anti-aircraft guns in the background nearby.

I originally wrote this post after running across a random picture of the war tubas last fall.  Investigating the war tubas naturally led to acoustic mirrors which led to reading up on acoustic location and made for an interesting line of reading.  I should have posted in last November because in the course of updating my links so I could post it this week I discovered io9 had scooped me a month ago.  Bad Science has an interesting post as well.

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The Hunger Games by Suzanne Collins is set in North America in a dystopian future where blah blah blah…

I’m going to give you the plot summary this time.  If you don’t know it already you can find a plot blurb just about anywhere at the moment.  I read the trilogy back around the time they were trying to cast the big movie adaption that comes out today.  That was over a year ago so I’m not up to doing a review either.  I am going to share a few thoughts on the book series, and I might review the movie after I see it, but I mostly want to point out some impressive fan geekery I ran across recently.

First, the book thoughts………. The first book was definitely a page turner.  It sets up a pretty desperate situation in micro with Katniss, and in macro with an entire continent of poor folk catering to the whims of one city of lucky elites.  The majority of the books is about the games themselves providing a locked room situation with a bunch of teens trying to kill each other.  It’s hard not to be interested in a situation that tense.  It is also written for the young adult market so it’s a little easier to read than most adult fiction.  The combination of those two factors makes it hard not to stay up late reading.  The sequel, Catching Fire, is a little repetitive because it puts the characters back in the hunger games, but it’s different enough to still be a worthwhile read.  Mockingjay, the final book in the trilogy, departs from the hunger games completely and tackles some more complex issues.  I didn’t care for Mockingjay all that much, but it was still worth reading just to see how everything turned out.

Now, with that out of the way we can move on to the business at hand.  A couple of fans of the series pieced together a very well thought out map of North America as it would exist in the books.  I was especially interested because I was doing something internally as I was reading each book.  North America is ruled by a country called Panem (from the Latin ‘panem et cirense’ translated asbread and circuses which is a strategy that has been popular among politicians since Rome ruled Europe).  Panem is divided into a capital area somewhere in the Rockies and thirteen separate districts.  Each district has its own specialty product which it supplies to the capital and Collins hints at some of the locations but rarely includes any specific details leaving it up to the reader to connect things going on in the book with their own knowledge of current geography.

Collins doesn’t go into any detail explaining how the current U.S. ended up as a totalitarian state (really disappointed about that) but she does vaguely mention war and natural disasters.  Fan consensus is that a portion of both coasts ended up under water and the continent is a lot smaller so different disaster scenarios were examined to determine which fit the best with the situation in the novels.  After that was done the remaining land area was portioned into the districts based on the few details Collins included.

If you’re curious, Tennessee is part of District 11, which specializes in growing crops to feed the country.  I highly recommend the original post (though it devolves into a commercial) even if you don’t know anything about the books.  I always enjoy the reasoning that goes into piecing together a larger picture based on scattered facts and I really admire the time and effort that was put into this.  It reminds me of genealogy or even military intelligence.  I feel like I’m not doing it justice, but I was really very impressed at how they merged natural disaster research, details from the book, and current land use.  I could quibble with a few things, but in all it’s a better effort than I would have made.

Found via the AV Club.

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Kitchen Sink Chemistry

I was trying to show the dual chambers and opening, but it didn’t entirely come out.

Meta commentary: Much like my post on Hawaiian currency during World War II, this is one of those posts where pop culture entertainment ended up spurring actual research.  I thought the end result was interesting so of course I’m sharing.

Liquid Plumr has this neat product called a Foaming Pipe Snake.  (The name apparently comes from someone without much imagination, because the result of using it is literally a foam equivalent of a plumber’s snake.)  When you dump it in your drain it cleans the organic crap that is gunking up your pipes.  It comes in a plastic jug split in half with two separate chambers that pour out of the same opening.  The chambers have visibly different liquids in them and a noteworthy lack of foam.  The magic happens when you pour them into the drain and they become something different as they mix.  (Just like having a kid.)

Note the dual chambers. (That’s just colored water that I added after dumping the actual product down my drain.)

The dual chambered container and the chemical reaction when the two mixed reminded me of something I read many years back in a war story.  In the story one of the armies was using something called a binary chemical weapons.  The theory behind these is simple.  Take a hollow artillery shell and fill it with two separate chemical compounds separated by a thin wall.  Separately these chemicals aren’t that dangerous, but when mixed they become deadly.  The stress of being shot from a cannon destroys the interior partition and causes the two chemicals to mix as the shell flies through its trajectory.  When it explodes upon landing the gas is spread over a wide area.  It’s an elegant system and it really does exist.

The similarity between a deadly weapon system and the drain cleaner sitting on my counter was disconcerting.  I assumed the mixture was forming some sort of dangerous acid that had to be kept separate until it safely away from my frail pink skin so I took to Google to investigate.  I discovered that Liquid Plumr, and most other drain cleaners, is mostly combination of sodium hypochlorite and sodium hydroxide (street names: bleach and lye*).  It unclogs a drain because it’s caustic (acid) and it generates heat when it reacts with water.

* Must resist Lewinsky joke that would have been hilarious 15 years ago…..

I assumed the foaming product would be more potent because of the binary container and because it’s advertised as cleaning your pipe walls in a way the regular stuff won’t.  I was wrong.  I looked at the material safety data sheets for both products and the only major difference between the regular and foaming varieties seems to be the addition of hydrogen peroxide.  My working theory is simple: one side is regular ole Liquid Plumr, and the other is hydrogen peroxide.  The regular stuff is heavier than water so gravity makes it flow down the pipe until it hits a clog it can react with, but when you mix it with hydrogen peroxide the foaming action causes it to expand toward the pipe walls so it can break up the gunk on the walls rather than just gravity flow until it hits an obstruction.

This is just a working theory on my part.  I’m sure the manufacturer adds some other ingredients, and for legal purposes I don’t advocate any home experimentation no matter how many episodes of Breaking Bad you’ve seen.

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iPhone Review: Hero Academy

"It's not wise to upset a wookie."

The original Star Wars movie (I still can’t think of it as A New Hope) has a scene when everyone is holed up in the Millennium Falcon for the long trip to Alderan. Two of the characters are playing a vaguely chess-like game with holographic projections of monsters. I like to think of Hero Academy as the closest current technology can get us to that on-screen game.

Hero Academy is a vaguely chess-like game with a fun mix of strategy and tactics. It’s a capture the flag variant played on a chess board. Each player has 1-2 crystals on their side of the board and the idea is to smash your opponent’s crystals before he gets yours or to destroy all her pieces before losing your own. You’re presented with a Scrabble style slate of pieces to use in your attempt at domination.

You can use one of three different teams of pieces based on various fantasy races (Dwarves, Elves, etc…). Abilities of the pieces roughly correspond, but the strengths and weaknesses vary a bit from team to team and it takes a little practice to get familiar with them all. You also have the ability to add armor or offensive power through the use of various power-ups. You start with a random mixture of six pieces and power-ups to put on the board each turn. In the early game the pieces you use are replaced, but supply quickly dries up and you’ll find yourself making a lot of strategic choices about when to use your best stuff. Each turn you and your opponent get five actions which you can use to move a piece, attack your opponent, or use a power-up.

There’s a random match making system to find opponents, but there’s no attempt at equalizing player skills so you can end up facing a veteran of 100 games or a brand new rookie. The app does have a built in hook to Facebook and Twitter so you can recruit friends to play as well. You’re also required to set up a player account with the game developer, but they don’t require any personal info beyond email.

The game uses an asynchronous play style so that both players don’t have to be playing at the same time. It’s your basic ‘play by mail’ set-up. One player makes his moves and the game saves them and sends them for the other player to contemplate at his leisure. This is handy because you can play at your own pace and the game doesn’t need your full attention for an extended game time. Sadly, this is also the biggest drawback because your opponent has the same leisure to take his turn and you could end up waiting a long time if they aren’t paying attention. It also includes an option to cause your pieces to taunt your opponent and a rudimentary chat program for trash talking.

Hero Academy works on the ‘freemium’ business model. The basic game is a free ad-supported download and comes with the Council team enabled. You can pay $1.99 for access to one of the other teams and various cosmetic enhancements. I picked up the Dark Elf team because I spent enough time playing that I felt like the developers had earned some of my money (and it was also a small price to pay to get rid of the ads and the extra load times they caused).

I’ve been really enjoying the game, and for a while I had as many as a dozen games going at a time. My win-loss record was pretty favorable until I convinced a friend to play. Unfortunately, not only was he was a quick study, but he also lets his son ‘help’ so I’m doomed to being trash talked by a four year old who I’m not even allowed to put in time out for no good reason.

I’m always in the market for new opponents, so if you decide to try Hero Academy leave me a note in the comment section and we’ll start a game.

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Photo via Wikipedia

The botany department at Cornell University is enjoying a day in the sun while science and aesthetics combine.  They acquired the seeds of a Titan Arum in 2002 and have been growing the plant ever since.  The plant only grows in the wild on the Indonesian island of Sumatra and is rare in culvtivation as well.  Cornell’s plant has been nurtured by grad students for the last decade and is finally flowering for the first time right now.  Since the plant is so rare Cornell has put up a streaming web cam and opened the green house to the public.

I’ve been reading up on the Titan Arum since I saw the story this morning.  The plant is remarkable for a couple of reasons beyond simply being rare.  It’s commonly known as the Corpse Plant because when it blooms a deep purple color it also smells like rotting meat.  In a really odd evolutionary twist, the purple color and the rotten stench are meant to attract carrion flies to pollinate the flowers.  Cultivated Corpse Plants take 7 to 10 years to bloom and the bloom lasts for two days.  After the first bloom they then bloom once every few years after.  An early specimen cultivated in England bloomed in 1889 and went dormant until finally coming to life in 1926.

The size is what impresses me about the most, at least until I have opportunity to smell one in bloom.  They group as tall as 3 meters (10 ft for you Yanks) and they develop a tuber root that comes in at 200 lbs.  The folks at Cornell has posted a growth chart for their bloom that’s pretty amazing.  They started at 38 inches on March 4 and the most recent measurement was 66.5 inches on March 18.  That’s a growth of over two feet in just two weeks.  The Cornell plant flowered some time on Sunday and according to a local paper the university is trying to pollinate it with pollen frozen in 2010 when a plant at Binghamton University bloomed.


From the Cornell webcam.

This event is going to make some lucky grad students famous.  The researchers at Cornell are taking the most advantage of the rare blooming that they can.  They’re sampling the odor so they can study it, and on their website you can see thermal imaging of the plant (which apparently uses an internal heat of 96.8 F to disperse the odor) and some endoscopic photography of the inside taken before it bloomed.  (The endoscopic shots could be someone’s colon for all I can tell, but it’s still pretty cool.)  Even at 6:30 AM when I first looked at the webcam there were fascinated grad students and bystanders looking at it.  I checked in again before posting this, as you can see from this screenshot, it was getting pretty busy in the green house.

Apparently the first known flowering in the US was at the New York Botanical Garden in 1937 and the Corpse Flower was the official flower of the Bronx from 1939 until 2000.  There’s got to be some good jokes there, but I’ll leave that to my friends in New York.

Check out the webcam and basic info.  If you’re interested enough, I recommend clicking through to the blog after you’ve looked at the webcam.  The blog has some interesting info on the researchers attempts to pollinate the plant.

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This post is a continuation of my previous post about mathematical modeling.

Modeling is a tricky proposition. Good results require a fair amount of judgement on the part of the person using the model, and developing the model usually requires some simplifying assumptions. Let’s jump back to the example about grandmother. In that discussion I said grandmother’s average speed is 45 mph. The wiggle room in that statement is average speed. Grandmother is going to have to stop at a couple of traffic lights before she gets on the interstate, and she’s probably going to have to slow down once or twice for someone else’s grandmother driving even slower. She’ll have to drive extra slow while she squints at the street signs looking for Old Hickory Boulevard. While she’s driving on the interstate she’ll actually be driving a little faster than 40 mph most of the time, but we have to average it out.

That brings you to one of the difficulties of modeling. The basic equation is a given. It’s always the same. But how do we figure out that average speed we’re using? Well, grandmother has driven to our house many times before and we have a pretty good idea of how long it takes her so you we figured it out by observing previous instances of the process we’re modeling. Sadly though, our model only works if she’s driving to our house. If grandmother is driving to our sister’s house in Knoxville, that average speed is going to be different because her route is different. She’ll be stopping at a different number of traffic lights, and she’ll be driving through town instead of mostly interstate driving. So sister will have to figure out her own model (just send her a link to this post). And when grandmother goes to Chattanooga to visit mom and dad, they’ll have to figure out their own model. The basic framework stays the same, but the average speed will be different.

But let’s jump back to our model for grandmother’s trip to our house. What happens if it’s raining and grandmother has to drive slower? We can adjust our average speed downward, but then that messes up our nice simple model because we have to change it every time the weather changes. Instead, we can add a ‘weather adjustment factor’. That way speed is still 40 mph, but the weather adjustment factor will change it as needed. So now our model is:

Distance = Travel time x Average speed x Weather factor

When the weather is nice and sunny grandmother’s cruising speed is 40 mph, the weather factor is 1 so nothing changes. If it rains, well then grandmother drives about 90% of her usual speed. So the weather factor is 0.9. If it’s snowing then grandmother’s going to creep along at half speed so the weather factor is 0.5.

Sunny day => Distance = Travel time x 40 x 1

Rainy day => Distance = Travel time x 40 x 0.9 = Travel time x 32

Snow day => Distance = Travel time x 40 x 0.5 = Travel time x 20

The adjustment factor can be used for other things too. Say, for instance, grandmother has some good gossip about Uncle Ed. She’s going to drive a little bit faster so she can get there and share the juicy stuff with you.

Gossipy grandmother => Distance = Travel time x 40 x 1.25 = Travel time x 50 (grandmother enjoysr gossip)

If you like, you can start stacking the variables and using more than one. What happens if grandmother wants to gossip about Uncle Ed’s first born getting arrested on a rainy day?

Rainy, gossipy grandmother => Travel time x 40 x 0.9 (rain adjustment) x 1.25 (gossip adjustment)

Distance = Travel time x 45

You can get as complex as you want. What if grandmother stops at the grocery on her way? What if your dad is riding with her and she drives slower when she talks to him?

When developing a model the dilemma is always in deciding how complicated to make it. The more variables you add, the more accurate your model will probably be. But there comes a point when adding variables is not worth the extra effort. Does it really matter to you whether it will take grandmother 4 hours or 4 hours and 5 minutes?

So you have to consider whether it’s worth the effort to put extra work into the model just to make it a little more accurate. This is a question most young engineers struggle with and it requires a fair amount of judgement that usually comes with experience. Bridge modeling can tell you how much concrete to pour down to 0.01 cubic ft, but the concrete truck bringing it to the work site has 75 cubic feet in it and the trough that pours it out of the back of the truck doesn’t have a measuring device on it. So you can spend as much time as you want calculating the concrete thickness down to the nearest 0.01 inch, but you’re going to get the closest eyeball estimate the site supervisor or the concrete truck driver can make.

I’ve got one more post coming up about modeling. We’re going to discuss some real world uses and hopefully look at a specific modeling example or two.

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Mathematical Modeling 101

I have a particular colleague who, when he was out socially, would occasionally tell people who asked what he did for a living “I work with models”.  I’m pretty sure he was doing it as a funny ice breaker rather than any serious attempt to impress people (I always found that just saying I design bridges worked for me).  What he was actually referring to was mathematical modeling, the way most detailed engineering design is done now that computers are advanced enough to handle it.

The easiest understanding of mathematical modeling is just a literal interpretation of the phrase.  Mathematical modeling is building a model of a thing or a process through the use of math.  A mathematical equation or process is used to determine what happens when you put something into a system.

Let’s start with a simple example.  The model for distance traveled is:

Distance = Travel time x Average speed

Say your grandmother is driving through the woods and over the river to visit you.  Grandmother doesn’t see so good anymore so you worry about her when she drives.  You could just call herr on her cellphone every 20 minutes, but she gets annoyed when you do that too often.  Besides, distracted driving is dangerous driving and finding anything in grandmother’s purse IS distracting.  You can maybe call maybe once without ticking off the old lady, so you should probably do it right after she makes the turn onto Old Hickory Boulevard, because even people who’ve lived in Nashville for 50 years get a little confused about Old Hickory Boulevard.  So how do you know when she gets to that spot?  Well, you put together a little mathematical model.  You know she drives 40 mph no matter how many honks she gets from the people behind her on I-40 so you use our equation above.

Grandmother’s driving distance so far = Time on the road x 40mph

or D = T x 40

Grandmother tells you she’s going to leave at 7 AM, which really means 6:30 AM because great-grandmother didn’t raise no Late Louise.  So at 8 AM she has been on the road for 1.5 hours and she has traveled:

D = 1.5 hours x 40 miles per hour = 60 miles

Not quite to the turn at Old Hickory Boulevard yet.  So we have to wait a little longer.  If you prefer, we can rearrange our model a little.  We know that the important turn is 80 miles from grandmother’s house and we really need to know what time to call her.  So we can use a little algebra (did everyone quit when I typed ‘algebra’?) to rearrange the equation how we want it.

T = D/40 or T = 80/40 = 2 hours

Now add grandmother’s starting time and our model is complete and we know what time to set the alarm to wake up and call grandmother.

T = Start time + (Distance/Average Speed)

T = 6:30 AM + (80 miles/ 40 mph) –> T = 6:30 AM + 2 hours

So set that alarm and call grandmother at 8:30 AM, just to make sure she turned left on Old Hickory Boulevard.

This is getting long, and I’m sure I lost a lot of you at ‘algebra’ so we’ll wrap it up for now.  Next time I’m going to talk some more about modeling complexity and variables, so get a good nights sleep.  Now, please excuse me while I work on the model for reader loss whenever I say ‘algebra’.

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