Doctor woohoo

I've just got off a late-night phone call from my rather excited parents in Sydney; turns out my long suffering PhD manuscript has finally passed the last hurdle, and I am now officially a doctor.

Goodbye phdcomics!

*sob*

(not)

uni-bling

As Briony alluded to, the final, not-going-to-tweak-this-bugger-any-more version of my thesis is printed, handed in, and forgotten about. Four copies had to be printed - doublespaced, ring bound, and sprayed with special pheromones to make the PhD assessors think they are poultry.

So I went on down to the graduate research school at UNSW, and I uprooted my thesis from its moorings, and hurled it across the desk into the willing arms of the PhD review machine. I filled in a little survey on my postgraduate life (What was your best experience? Worst? Discuss, with examples), and was promptly rewarded.

I received a box and a little congratulatory letter, wrapped up in a ribbon:

Inside the box, a little slice of flavoursome UNSW bling:

I plan to attach it to a huge gold chain and wear it around my neck at my graduation. That said, with bling in hand, I decided to pay homage to an old, old uni tradition.

You see, back in the halcyon days of being an undergraduate, we had this thing with exams. Our loosely knit group of friends (think of it more as a cardigan than a jumper), we'd turn up to an exam, and variously nervously twitch, scribble and fluster our way through it. About halfway though the exam, one of us would leave. This would prompt the rest of us to follow shortly thereafter, where we would congregate at the biggest dive that was nearby - in our case, invariably Mickey D's on Barker Street.

I exchanged some cash for a greasy apple pie from the equally greasy, spotty teenager behind the counter, and I wondered what he was going to write his PhD dissertation on. I munched on down on it, and realised the apple pies tasted better when they were made from chokos.

We're going to be moving in a few weeks, so now it's back to the unenviable task of re-packing all of our stuff into a small, small space. Luckily, I think I'll try to get a machine to do some of the work :P

Scientific analysis!

Is Hiren writing up? Let's answer the question with some scientific analysis!

Here is a unquestionably thorough look at the question, performed by carefully selecting five sample points and extrapolating a trendline in Excel. I can see you screwing up your face in disgust, but you cannot question my study, I have a PhD!

As you can see from the above graph, by the time we reach June, if Hiren is still writing, he'll be making at least 12 blog posts a day. This is a clear sign that procrastination has kicked in and the PhD has been kicked out. Can you imagine the horror?

Firefox users, you want this extension. Frames and tabs are FTW!

chapter 7: conclusion

Burning the candle at both ends, dousing it in kerosene and then taking to it with a blowtorch helped me sail past the deadline only 24-hours late. My thesis draft (beta2, 'MC-Hammer' edition, for those that take an interest) has been sent to the supervisor-A for reviewing and editing. That will come back to me, endure a few days of fairly heavy fixing and corrections, and will be bundled off overseas and locally for final assessment before the end of the month (this will be beta3, 'Fresh-Prince' edition).

In Australia, unusually, there is no PhD defence process - you write your thesis, and it's sent off for review overseas. A few months later, it comes back with requests for corrections, and then you can go and wear the silly hat for graduation (I'm going to keep that hat, probably nailed above the doorframe of the lavatory of whichever house we finally end up getting).

The most tedious part of my PhD work is now well behind me, and I'm slowly resuming normal life. I can't quite describe how it is not having that nagging feeling in the back of your mind all the time, telling you that you should be running an experiment, or writing up. I don't think I'll be able to fully count it as 100% over until I send my final version in, but it's extremely close and I'm sufficiently unwound now to enjoy life. Five years is an awfully long time to have been doing anything, and with this whole combined working and PhD thing, I seem to have been doing a bit of everything. It's good to be done.

Linear vs. Nonlinear FEM in biomechanics

The situation goes like this: in a biomechanical FE (Finite Element) simulation, the actual mechanical parameters of tissue are difficult to accurately determine. You can't just go poking tissue inside a live human being to get parameters because, well, they're alive. Dead tissue in cadavers responds differently, and the use of data from animal tissue is debatable - as well as having its own ethical problems.

So, given the issue of modeling tissue using near-real- or real-time FEM, is it worth using a more accurate mechanical model - say, nonlinear elasticity - over a simpler model, such as linear elasticity, which is easier to simulate?

Unless the deformations are really small, my own take on it is to use nonlinear FE (such as Neohookean elasticity) if at all possible. This is not because of precision, but because of better behavior under large strains. Let's look at an example.

Here I've meshed the infamous Stanford bunny using my own octree-based meshing technique into about 22,000 tetrahedra. I've fixed anchor points at the top of the left ear and near the lower rear of the bunny. Gravity is applied to the object, and we observe what happens as the FE-solver (in this case, a modified version of salmon by Nienhuys) converges to a rest-state (which is never completely reached, for the sake of brevity). The visualisation is done in VTK and computed on a 3.2Ghz Intel PC running kubuntu.

Linear Elasticity:



Initially, the solution is great, but eventually, the volume blows up. Not much practical use.

Neohookean (nonlinear) Elasticity:



Much better. The right ear makes a concerted effort to flop about a bit, and we see the mass of the object roughly rotating around the axis formed by the left ear and the anchor points in the bunny's rear end.

conversations with a bagel

There aint nothing you can do to make me talk mister. Nuh-uh. Never!

No! Not the knife! OK boss, I'll talk! I'll talk!

I'll... yeaarrrrgh!!! *gurgled scream*

Don't talk to your food, folks.

Apologies to these guys; you might also want to see this collection of oddness (check out the 'how-to' archive, very funny). And then, there are these links :)

writing thesis up now..

source

..gah!