Ode to Inverse Problems

Deep into the night and before calling it a day for today (disgusting rhyme but “lasciamo stare“) this is one of my geek-break-musing from actual work. The topic is a fascinating family of mathematical problems called “inverse problems”.  Wikipedia is a good place to get some more formal information but to make it really short here is a definition by example: 2+4=6, no doubt about it and this constitutes our “forward problem”, i.e. given a defined input we calculate a unique result; but what if some one asked to find out what you had to add up to get 6 but had no way to ask you or otherwise determine the exact combination? There are 4 different combinations to get 6 by adding two numbers and even more if you can add more than that, so how can you say? Well you can’t really and this is what makes an “inverse problem”, i.e. when you are trying to deduce the right answer from a pool of equally plausible alternatives. Welcome to the mathematical equivalent of delusion.  Now for the necessary soundtrack I will go for something very mathematical and at the same time delusional: enter sandman in the form of Gould.

 

In the very essence this is an area of applied mathematics but us lowly engineers sneak in, as always, to muddle elegant theory into crude and practical results. The later, the muddle bit, is in a broader sense the topic of my doctoral dissertation.  In my thesis I look into the problems arising in the stochastic reconstruction of random heterogeneous materials, like porous rocks for instance.  In simple terms I ma trying to come up with ways to get from a statistical description of 2D images to a fully 3D representation of the material that is true to the very nature of the original. Now, how can you describe statistically a 2D image? This is hard if you think in terms of a complex full colour image but if you picture  a simple black & white checkerboard this might become easier to grasp. Such a

El Tunel

El Tunel

 pattern can easily be translated to some rule (read statistic) that simply says “every 1 step of 10cm paint a black square, immediately followed by the same in white and then repeat  until you have reached so-and-so dimensions”. This is the recipe to make a black-and-white Rubik-type of cube were each sub-cube is of alternate colour. This is the idea that is applied to complex heterogeneous materials, a nasty term that means “something like a (natural) sponge, all irregular and weird but also the same way weird no matter which way you look at it”.  Now that we have established our toolbox of statistical descriptors we can venture to the real world. This methodology suffers from a serious practical limitation: it is not computationally feasible and to an extend even theoretically possible to have a complete statistical description of the intricate morphology of a complex material just by examining 2D sections of it. As always the mathematicians did their brilliant part and then we engineers started cutting corners and trying to fit our need to the delusional nature of this endeavour. My contribution, more like a mashup really, was to pick-and-choose ways to improve getting to a realistic representation of the real material by (in effect) cheating.  The “cheat”  consist of some educated guesses that use previously know information on how nature or industry generates/constructs a material and use this information to guide our solution algorithm through the maze of multiple plausible solutions to the one like the actual material we are trying to recreate. I’ve written about 180 pages of instructions manual to practising (dis)illusionists, called it a thesis and hope to get a PhD out of it the 17-Feb-09.

To end this musing I want to draw the attention to an intriguing and very personal experience of  inverse problems, that is learning from experience. Now at this point a disclaimer is of order; I am going to misuse and abuse scientific terms a little to make this artsy-fartsy, literary ending sound pompous. Don’t buy it, it is just fluff with no substance but I can’t resist making analogies out of analogies.  Think about it every time you are trying make a rational choice based on previous experience. What you  (we)  are really trying to solve is a horribly inverse problem. We are trying to estimate a new state of future affairs based on the (arguably) incomplete evaluation of past events, a classic in parameter estimation for those versed in reaction engineering. Now how much this helps when getting into an argument with your concubitus is another story and I wish you my best of luck!

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Marketing advice to Twitter

Now don’t get me serious on this. I am an engineer by training and only worked in R&D so marketing is something I only read about and never actually practised. So, again this is just a musing on my beloved new social web tool or micro-blogging or whatever-makes-the-poets-happy you wanna  call it.  Please you people on Twitter inc. don’t fail! Make sure that in these difficult times you end up with a viable revenue stream to keep the service alive.  Now to my naif suggestions that could also be read as genuine questions to satisfy my curiosity.

1. Set up a “pro” or if you don’t like the connotations a “plus” type of account were you get a tick next to your name (say @mgpolitis +plus) and charge a pettiness for it, say 5 USD per year via paypal or similar.  For some icing in the cake through non-cost options in the deal like extra templates only for “+plus” users, more space for the short bio field in the user profile or any silly perk you can come up to that in reality costs zilch.

2. Set up a more professional offering with one-click backup and restore account options, added features like transparent user switch off (a.k.a. “muting”: removing the updates of  selected followers without un-following them), click and pick thematic group creation and charge even more for this.

Now this is just what I came up with in some milliscoble worth of my time. I am pretty sure you have brilliant people working for you. Can you please explain to me why on earth you are not doing even the most obvious to raise some money? Please, I am really interested because it is impossible for me (I said I’m an R&D Chemical Engineer) to understand why you are not doing it.

thank you!

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taking a break to talk to myself

“In the internet no one knows you are a dog”, this was the defining moment of the proto-internet, the one before web 2.0 shenanigans that really transformed  the way we interact with the medium. This post is an almost surrealistic automated-writing type of musing that is not fact-checked and pretends to be my idea of having a break from actual work to do something relaxing.  Yes, for me this is actually relaxing, I’m a geek you see… Since every self-respecting brake needs a song, I am starting with a taste of Mina in a monumental live cover of Lucio Battisti’s “Io vivro”.  

I’ve been around since the beginning of the web as we know it, seen the ‘dogs’ chatting, the ‘personal web page’ era and the return of the blogs (they were relational databases of html archives, hand-coded by super-geeks, at their conception).  But what really changed everything was facebook, the teenage, hormonal and in-your-face uber-popular eponymous-by-explicit-choice web experience. By all means FB was not there first but as always the winner takes all the credit but the concept applies equally to friendster, orkut and other ‘social media’.  The implications are profound and moving to a virtual world with all the “stone age” social constructs is a profound shift in human evolution of co-operative interactions. As it is expected, this also makes Orwellian scenarios a scary prospect and marketing based on data-mining user habits and real-life choices a very appealing tool for all sorts of products, not always tangible but also political or ideological. If we sprinkle some twitter on this and look at this time-shifted, cached, instant peer-to-peer communication network the effect can be transformative in many ways.  I think of politics and participatory democracy but this is drab and Cornelious Castoriadis already preached about technology enabling the return of direct citizen democracy back in the ’80.

As a more fun closing to this musing and as my 30min brake comes to an end, I was thinking of the way eponymous web transforms people networks, how it can complement, extend and enhance the way you share a moment with your kid that studies abroad, with your wife while you are away and sneak a tweet of two or even how you actually create or add-to your network of friends, those of the real-life-variety, those that you have a drink with.  The parting song of this musing I feel like it must be  King Crimson’s Epitaph cause “Knowledge is a deadly friend | When no one sets the rules”; but sod the lyrics, the guitar part is just mind-blowing.

Addentum: on a second thought Billy Bragg’s “Greetings to the New Brunette” from Talking with the taxman about poetry, is what this piece of verbal diarrhea needs for a soundtrack

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Recipe: Greek Magiritsa style Chicken soup with a verve

During Easter in Greece it is a tradition to have “Magiritsa“, a soup of  lamb innards. This is a bit too much even for Greeks to have on a regular basis so this is my wife’s take on a more ordinary version with a verve, the chicken Magiritsa  fricassee. For a professional presentation of a similar dish this NYT piece is excellent.

We will need:
big fat Chicken, ~2kg, quarterted
12 fresh scallions
two big dry red onions
1 cup fresh parlsey
1/2 cup fresh dill
1/2 cup fresh mint
2 tsp olive oil
salt to taste
3 eggs
3 lemons
1 cup white risotto type rice
Heat the oil in a saucepan and simmer the chopped dry onions and chicken quarters. Add 6-8 cups of water and when it starts boiling add the rest of the greens (scallions, dill, mint, parsley) properly chopped. Reduce heating to the point the soup barely boils (no bubble brake up at the top). After about 40mins add the cup of rice. After 20-30 mins or when the meat is tender enough we take it off the heat, carefuly place the chicken quarters in a platter and separate out the bones. Put just the chicken meat back in the pan. Just before serving we make the avgolemono:
Beat vigorously the juice of 3 lemons with 3tbs of the broth and a pinch of salt, to taste, using a whisk or spoon. Caution: the soup should be taken off the heat for at least 15mins before adding the avgolemono to avoid curdling. When the lemon + broth mix foams add it to the soup and voila, a hearty chicken soup with a Magiritsa verve.
enjoy! (responsibly 😉
magiritsa_kotas

magiritsa_kotas

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Friday Summa 3, December 12

1. This was a week of turmoil and grief.  In Greece we have tolerated state and police brutality for too long and now it is back-firing. The December riots were nicely presented in this Guardian piece. We will remember Alex and the best part of the country will try to have the events mark a societal turning-point.
2. Feeling pissed off with all the above I had my healthy diet of Rage Against the Machine and System of a Down. I had Revenga and Toxicity looped on my playlist.
3. The recursive transpositions of Philip Glass in Akhnaten: Funeral of Amenhotep III somehow felt like the perfect soundtrack for the days.
He flies who flies
This king flies away from you
Ye mortals
He is not of the earth
He is of the sky
He flaps his wings like a zeret bird
He goes to the sky
He goes to the sky
On the wind
On the wind
4. Finished reading “Outliers” by Malcom Gladwell.  I had mixed feeling initially because of the preconditioning from the flood of reviews (some trashing it) and promo talks that preceded it but in the end it is not bad.  Just don’t expect anything original.  It makes a decent airplane read or in my case an audiobook for my hour-long runs. The last chapter is a more personal account about the story of his (black) mother getting to UCL from poor rural upbringings in Jamaica and meeting his (white) Math professor father.  This is the most interesting read of the book.
5. In case someone is still uncertain about why non-cellulosic biofuels are a dead-end, here is another review “19 Hurdles for Large-Scale Biofuel Use
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Posted in Akhnaten, Friday Summa, Greek riots 2008, Malcom Gladwell, Philip Glass, System of a Down | Leave a comment

Friday Summa 2, December 6

1. I have audited (i.e. listened to the audiobook) “The Predictably Irrational, The Hidden Forces That Shape Our Decisions” by Dan Ariely (MIT/Duke – Behavioral Economics). If you have fallen from another planet and missed on the Freakonomics school of irrationality studies along with an assortment of blinking Gladwell lights then you might mind it interesting. If you are a regular on NYT, Harpers, New Yorker and the like skip. To listen during my short winter runs (~7km) it was OKish.

2. Clean Coal and Carbon sequestration are topic that interest me both professional and intellectually. I have read on The New Republic a good piece on the subject, with ref to a recent McKinsey report carbon sequestration for Europe.

3. I am proud to be part of it: “The babies born between 1965 and 1970 were historic” says in an article about peak population Alex Steffen in worldchanging.com. This is the generation also of a longevity boom on a global scale and the implications for the economy and the environment can be dramatic if you just continue business as usual.

4. I ‘live-by-Google’, use most of their tech and absolutely admire the company and their corporate ethos. (with some glitches, cf China censoring, but we have to keep a perspective; not an easy good/bad dichotomy). This presentation dissects Google and their business. I must thank the tweet of Jeremiah Owyang for suggesting it. My kvetch is that it misses out on the scientific/technical aspect and scale of Google’s data processing. Thankfully Mark Chu has a nice post about this.

5. I was listening to some ten-odd different covers of ‘Hit me baby one more time’ ranging from excellent (Travis, Type O Negative, Children of Bodom) to some that make Britney sound artistic.

6. Another very intriguing cover is that of Elena Roger from Argentina covering ‘Io Vivro’ of Lucio Battisti that was majestically performed in the 70’s by the great Mina. Compare and contrast.

7. Lang Lang plays with the China Philharmonic Orchestra on Mozart’s Piano Concert nr24 C-moll Kv 491, heard it on youtube and got very impressed. I will try to get hold of a studio reccording. The article that brought this to my attention is also very amusing. It looks like China will also be suppling the world with classical musicians!

Posted in Alex Steffen, Dan Ariely, Elena Roger, Friday Summa, Google, Jeremiah Owyang, Predictably Irrational | Leave a comment

Friday Summa 1, November 28

Summa comes from latin, means “the whole” and it is meant to be my weekly note-keeping diary of songs, films, books, articles, tweets and the kitchen sink of all I have come across that made it past my attention threshold over the past week. I am shamelessly copying the idea from the excellent “Friday Random ” of the extraordinary gentleman of Good-Math-Bad-Math Mark Chu-Carroll. I hope he does mind 😉
1. Daniele Sepe: I have reaffirmed how much I like the crazy ethnic jazz variations of .
2. Watched the Brasilian film “Elite Squad” and I liked it. Think of a SWAT team action movie but with more flair. The starting song “Rap das Arma”, a brasilian gangsta rap about guns and the favela, is also very nice, in samba style!
3. Finished reading “The Post-American World” by Fareed Zakaria. Nice, easy read on geopolitics.
4. I was mesmerized by the cover of “Venus in furs” in a live of Mandrugada. Strike, dear mistress, and cure his heart…
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