Archive for August, 2007

Calculating the van der Waals binodal curve with Maple

So, I finally scraped some Maple code together to solve this, but it needed guesses to be very close, mostly, to the actual answers. I’m currently working on some scipy code that will do this in a less accurate way – will try to post both sets of code here.


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Intrigued by algae

I’m intrigued at the possibility of algae farming for oil.

Forget higher order hydrocarbons (note to self: revise organic chemistry), just in terms of producing a straight vegetable oil, with no spectacular properties. Is there a plant/microbe that could conceivably be farmed, in a small scale facility, as to produce a cost effective fuel?

Could this have an application as a developing world technology (same mode as the rugged laptop with a manual battery charger)?

What are the numbers?

My connotea reading list is at

It appears that the maximum possible energy yield possible using photosynthesis can’ possibly produce anywhere near enough fuel to be viable on a small scale. This is just my impression from reading a few discussions, I’ll get to the physics myself at some point.

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Minor PC crisis

Oh dear. So, I took advantage of the fact that my institution provides a legit copy of windows xp for it’s staff’s home machines. Now it appears I’ve broken my existing windows installation. At first the installation was halting because one of the files it was trying to replace was ‘being used by another application’. Then when I booted from CD and chose to reinstall-repair, it froze at the ’34 minutes to go’ mark every time.

And so the troubleshooting begins. Memtest came back fine.

Ouch. The good news is Marnie’s files are ok, on the first partition. The bad news is it looks as though the partition with all my files is broken. Knoppix says: “Could not mount device. The reported error was: MFTMirr does not match MFT. Failed to mount /dev/sda5: Input/output error. NTFS is inconsistent. Run chkdsk /f on Windows then reboot it TWICE! The /f parameter is very IMPORTANT…”

Ok, sounds like reasonable advice.

Update: did what the man said, ran chkdisk which took an awful long time, but repaired the files enough for me to Knoppix some backups. Looks as though the Windows installation is taking.

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Graphics in Octave – multiplots

Even though I’ve decided Octave is probably best avoided for publication quality graphics, sometimes it’s nice to be able to spit out a nice graph. Probably the best way to learn to do this sort of thing in Octave is to browser the Matlab documentation. Be warned though, not everything works! Behold the octave multiplot scriptlet:

%a,d are sets of data points
%t is the common axis for each data set
%param1 and param2 are numbers that characterise
%the graph - useful if you want to toy with some
%parameters and print out images of everything
ofname = sprintf("my_image-%d-%d",param1,param2)
%plot the first data set. '-or' means '-' for line style 'o' to draw on the data points, and 'r' for red
%tell octave you've got more plotting to do
hold on
%plot the second data set as just points
legend('data set one','data set two')
title('my happy graph')
hold off
%print it as a png image

And you’re done. Here’s an example:nice_picture.png

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Drag and drop images for Tiddlywiki (no solution)

UPDATE: I am not aware of a simple solution to drag and drop images into tiddlywiki that will result in links, and not embedded files. Please enlighten me!
I’ve been using a Tiddlywiki as my electron notebook – so far so good. However, it’s been annoying have to type/cut and paste or otherwise do work to insert images.

Behold TiddlyTools”.

The process of import Tiddlywiki plugins is straightforward, but not obvious – make sure you’ve backed up before you start playing with it. This is how I imported AttachFilePackage.

  1. Navigate to the TiddlyTools page and work out what plugins/packages you want. Sadly I have not figured out yet how to import packages in one operation.
  2. Find a link to the main TiddlyTools, and use right-click save as to save the file
  3. Open the local copy of TiddlyTools
  4. Open your tiddlywiki in another tab, and choose import from the backstage menu
  5. Enter the location of the file you just downloaded, and follow the prompts
  6. This is where I think I missed something – I manually checked all the individual plugins comprising the package. It’s not that much extra work
  7. Note that if you want the attach menu to appear backstage you’ll need the backstage package too

And there you have it – one upgraded Tiddlywiki!

err, I should point out that this doesn’t work in Firefox on Ubuntu. Grrrrr

The other drawback is that it saves the image in the file itself – leading to rapid bloat of your Tiddlywiki.

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Wireless Christmas lights may become a reality!

Wireless power transfer via strongly coupled magnetic resonances.(RESEARCH ARTICLES)(Author abstract). Andre Kurs, Aristeidis Karalis, Robert Moffatt, J.D. Joannopoulos, Peter Fisher and Marin Soljacic. Science 317.5834 (July 6, 2007): p83(4).

This is bloody tremendous. I remember once, many years ago, my father commenting that whoever could invent a wireless christmas light would make their fortune. I’m sure I’m not the only one who thought exploiting resonance was one way to do this. Looks as though this team has done it!

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Computational Modelling in Social Science

Social science goes virtual

I’ve always been interested in the application of simulation techniques to economic and social systems. All my peers at the time found the first few chapters of Capital (simple commodity producing society, etc) dry and boring. I thought it was brilliant. The article above is a book review that looks at the state of the art.

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