Friday, October 30, 2009

Can a human being outrun a horse?

Apparently over long distances.

I was listening to Ira Flatow on NPR, in my car today. Since the New York marathon is tomorrow he was talking about it, and one of his guests claimed that when it comes to long distances, human beings can essentially outrun all other animals - including horses.

Since I heard only that snippet (I reached my destination), and I had a few minutes, I googled, and no kidding! Here is a fascinating NYT link on the topic.

Some interesting numbers.

The fastest marathon was run just under 2:04 hours by Haile Gebrselassie of Ethiopia which translates to an average speed of 12.67 mph, or 4:44 minutes per mile. A horse can gallop at about 25-30 mph over short distances, but like I said before, they often underperform humans in marathons.

Over short distances, Usain Bolt of Jamaica ran a 9:58 at the 100m dash, which translates to 23.35 mph, or 2.57 minutes per mile, while a cheetah can go at a top speed of 60mph, which is about three times as fast.

We clearly weren't built to outrun such predators.

So what tilts the balance in our favor as distance increases? Apparently it has all to do with cooling.

When a horse gallops, it produces heat at a rate greater than what it can easily dissipate. Humans are much better at dissipating energy.

A simple energy balance tells us that if the input is greater than the output, there is accumulation of heat which leads to a rise in temperature - which is clearly undesirable. The evidence for this hypothesis is the fact that humans have a much better chance of beating animals in marathons when it is hot, sunny, and humid - conditions that make heat dissipation even harder for the poor animals.

Tuesday, October 27, 2009

LaTeX tips: eqnarray and detex.

1. Handling equation numbers in the eqnarray environment

If you have an equation array environment and don't want to number certain equations use the \notag command. Thus (click to enlarge),


where an equation number has only been assigned to the second "equation" in the array.

2. The "detex" command
I bumped into this command by chance today. Funny thing was, it was installed by default on both my CentOS box at work, and my Mac OS X which runs BSD. It doesn't preserve formatting, but essentially gets rid of all LaTeX tags.

You say:

detex file.tex

You can then pipe it to a spell check or save it as a simple text file, and do whatever you want with the un-LaTeXed file.

This works well if you have command line spell-checker available on your Unix/Linux system.

Friday, October 23, 2009

Interesting Links

1. A visualization of the S&P universe.
Color, size, and transparency represent percent change, market capitalization, and moving average, respectively. Percent change relative to the rest of the market determines the speed at which a stock orbits - fast movers so to speak.
2. A new excuse for students. It would definitely work on me.
Check out the actual website!
3.  A visualization of job losses
Via FlowingData: Red means loss and green means gain, and as you can see above, there isn't much green (read that zero) on the map. The larger the circle is, the greater the number of net loss or gain compared to that of the numbers of the year before in the respective metropolitan statistical area.

Saturday, October 17, 2009

Linux/Unix is Sleazy!

Rediscovered this on the internet!

$ unzip
$ strip
$ touch
$ finger
$ mount
$ fsck
$ more
$ yes
$ unmount
$ sleep


Thursday, October 15, 2009

Active Learning in Science and Engineering

According to wikipedia:
Active learning is an umbrella term that refers to several models of instruction that focus the responsibility of learning on learners.
These days it is a teaching buzzword. Big time.

If you are a teacher and not employing active learning techniques, then you are a stubborn, old-school, ineffective, uninspiring, bumbling idiot. There are entire journals dedicated to enhancing student engagement using these "active learning" techniques.

To be perfectly honest, I do read this literature and find a lot of it fascinating. This site (Felder's webpage), for example, is chock full of interesting ideas.

My problem with it originates from the obsession with employing active learning techniques, especially in science and engineering.

In many social science classes, opinion is as important as fact, which facilitates a natural two-way dialogue. For example, what you think of Shakespeare's "Twelfth Night" is perhaps as important as what an expert thinks about it. Both opinions are "valid" - even if they are diametrically opposed to each other.

But the same cannot be said of Newton's third law.

You can't have an opinion about it. It is what it is. And this very fact reduces the number of meaningful avenues for increasing student participation.

Another confession.

I actually like teaching, and my courses usually review well, both with students and with peers (which is important because it is easy to win a popularity contest by making a course "easy").

My favorite teachers, themselves, have been old-fashioned role models. A common denominator among them was passion, super-smartness, depth, humor, and genuine love for being challenged by a newbie.

Those are things you can't fake just by reading the latest educational literature. Sure one ought to try to make a class interesting.

But sometimes, passion + humor + depth automatically transforms into "interesting".

Friday, October 9, 2009

Calvin is funny!

We were trying to take passport-size pictures of our daughter recently, and to say it was a circus, is putting it mildly.

I remembered the Calvin and Hobbes strip, where Calvin makes all sorts of faces, when his dad wants to get a good picture for their Christmas card.

To recall, this is what he gets when he develops his film:

Our experience wasn't very different! Thank God for digital cameras.

How to convert a set of eps pictures to jpg format?

If you have a linux system with ImageMagick installed this is easy.

While I refer to jpg and eps files in this howto, conversion between any two formats that ImageMagick supports is similar.

Let us say you have a directory full of eps files along with non eps files. A simple shell script using "sed" will do the trick

for i in *.eps
  prefix=`echo $i | sed 's/\.eps//'`
  newfile=`echo "$prefix$suffix"`
  convert -density 300 -units PixelsPerInch $i $newfile

Wednesday, October 7, 2009

We like cocky!

Check out this New Scientist article. It suggests that the public, at large, likes absolutes uttered by overconfident individuals. Jim Cramer, Dick Cheney, Rush Limbaugh and company, immediately come to mind.

If you are trying to persuade, it probably means that a nuanced, multifaceted argument is probably going to lose out to a black-white pronouncement. This has policy implications as the article points out:
There are times, however, when this link breaks down. With complex but politicised subjects such as global warming, for example, scientific experts who stress uncertainties lose out to activists or lobbyists with a more emphatic message.
On the other hand, one of the reasons I like to listen to Warren Buffett, for example, is also because he can distill complexity into something simple that I can understand.

So I guess, the knife cuts both ways.

Installing LAMMPS with AtomEye on your Desktop

Recently, I wrote a brief on how to upload files on blogger using a Google docs as the intermediary.

Here I am testing, whether I can upload a presentation (pdf) on how to install LAMMPS and AtomEye for the molecular dynamics class I am teaching this fall.

Update: Need to share it with you :(

Here it is on Scribd.
Getting LAMMPS

Thursday, October 1, 2009

Paper or On-screen reading?

I spend a significant fraction of my waking life reading. About ten years ago, most of my reading, and writing for that matter, was paper-based.

I distinctly remember that during my senior thesis, and the first few years in grad school - I couldn't read and think, off a computer screen at all. Writing was even harder, and I used to write stuff down on paper before composing a serious document.

Any technical paper, I had to download, print, and scribble on to really digest.

Here are articles from the Boston Globe and a University of Florida website which support the thesis that reading from paper is better. The latter website claims reading paper is 20-30% faster, more accurate (in terms of the ability to identify grammatical and typographic errors), and less taxing on the eyes.

But things change.

Personally I can now read much better off a screen. With a high-resolution monitor, I prefer it. My main reasons are the following:
  1. zoom
  2. place my paper online, and read it from any computer.
  3. "Go Green"
  4. read and create color documents at no additional cost
  5. follow hyperlinks
  6. organizing/searching papers is easier 
  7. search for a word in a long document
In fact, I write much better on a keyboard too. Not only has my speed increased, I can correct spelling errors, and especially because I use a sophisticated word processor invented in the 70s called LaTeX, I worry less about appearance and more about content.

Indeed, a not-so-new paper cited at the end claims that paper and on-screen reading have now become equivalent.

Something that my own experience mirrors.

Harrison, B, ‘E-Books and the Future of Reading’, IEEE Computer Graphics and Applications, Volume 20 , Issue 3 (May 2000) , pp. 32 - 39.