Some suggested time-pass (including ideas for Python scripts involving vectors and tensors)

Actually, I am busy writing down some notes on scalars, vectors and tensors, which I will share once they are complete. No, nothing great or very systematic; these are just a few notings here and there taken down mainly for myself. More like a formulae cheat-sheet, but the topic is complicated enough that it was necessary that I have them in one place. Once ready, I will share them. (They may get distributed as extra material on my upcoming FDP (faculty development program) on CFD, too.)

While I remain busy in this activity, and thus stay away from blogging, you can do a few things:


Think about it: You can always build a unique tensor field from any given vector field, say by taking its gradient. (Or, you can build yet another unique tensor field, by taking the Kronecker product of the vector field variable with itself. Or, yet another one by taking the Kronecker product with some other vector field, even just the position field!). And, of course, as you know, you can always build a unique vector field from any scalar field, say by taking its gradient.

So, you can write a Python script to load a B&W image file (or load a color .PNG/.BMP/even .JPEG, and convert it into a gray-scale image). You can then interpret the gray-scale intensities of the individual pixels as the local scalar field values existing at the centers of cells of a structured (squares) mesh, and numerically compute the corresponding gradient vector and tensor fields.

Alternatively, you can also interpret the RGB (or HSL/HSV) values of a color image as the x-, y-, and z-components of a vector field, and then proceed to calculate the corresponding gradient tensor field.

Write the output in XML format.


Think about it: You can always build a unique vector field from a given tensor field, say by taking its divergence. Similarly, you can always build a unique scalar field from a vector field, say by taking its divergence.

So, you can write a Python script to load a color image, and interpret the RGB (or HSL/HSV) values now as the xx-, xy-, and yy-components of a symmetrical 2D tensor, and go on to write the code to produce the corresponding vector and scalar fields.

Yes, as my resume shows, I was going to write a paper on a simple, interactive, pedagogical, software tool called “ToyDNS” (from Toy + Displacements, Strains, Stresses). I had written an extended abstract, and it had even got accepted in a renowned international conference. However, at that time, I was in an industrial job, and didn’t get the time to write the software or the paper. Even later on, the matter kept slipping.

I now plan to surely take this up on priority, as soon as I am done with (i) the notes currently in progress, and immediately thereafter, (ii) my upcoming stress-definition paper (see my last couple of posts here and the related discussion at iMechanica).

Anyway, the ideas in the points 1. and 2. above were, originally, a part of my planned “ToyDNS” paper.


You can induce a “zen-like” state in you, or if not that, then at least a “TV-watching” state (actually, something better than that), simply by pursuing this URL [^], and pouring in all your valuable hours into it. … Or who knows, you might also turn into a closet meteorologist, just like me. [And don’t tell anyone, but what they show here is actually a vector field.]


You can listen to this song in the next section…. It’s one of those flowy things which have come to us from that great old Grand-Master, viz., SD Burman himself! … Other songs falling in this same sub-sub-genre include, “yeh kisine geet chheDaa,” and “ThanDi hawaaein,” both of which I have run before. So, now, you go enjoy yet another one of the same kind—and quality. …

A Song I Like:

[It’s impossible to figure out whose contribution is greater here: SD’s, Sahir’s, or Lata’s. So, this is one of those happy circumstances in which the order of the listing of the credits is purely incidental … Also recommended is the video of this song. Mona Singh (aka Kalpana Kartik (i.e. Dev Anand’s wife, for the new generation)) is sooooo magical here, simply because she is so… natural here…]

(Hindi) “phailee huyi hai sapanon ki baahen”
Music: S. D. Burman
Lyrics: Sahir
Singer: Lata Mangeshkar

But don’t forget to write those Python scripts….

Take care, and bye for now…



It’s Hot…

It’s hot—I mean the weather. I mean that in Pune. I mean the one right now.

The temperatures in the city have consistently been hovering around/above 40 degrees, and this is unusual. That way, it’s possible that the the max. temp. figures themselves might not be very much above the average. It could also be that the min. temp. is way above the normal temp. Or, if not that too, then at least the temp profile throughout the day—the total flux received per day as such—might have gone significantly up. Or, the wind is unusually low… Whatever. But the fact is that it’s been very much hot for the past many days—not just in Pune but also for most of Maharashtra (and other parts of the country). … Hmmm….

…Is it just me, or have our daily newspaper-wallahs from Pune really forgotten to print photographs or news-stories on one or more of the following (listed in no particular order):

  1. Naked urchins caught mid-air on camera while jumping into: (a) Mula, (b) Mutha, (c) Mula-Mutha, or (d) a canal
  2. A vendor of water-melons caught napping on a heap of the fruit at the market-yard, right on the hot afternoon
  3. A sparrow or a crow perched on a municipality water-tap, its neck strenuously bent down towards the outlet of the tap, trying to drink the infrequent droplets of water coming out of the tap
  4. A close-up of a dry river-bed showing that typical criss-cross patterns of cracks developed in the baked mud
  5. A color photograph of a bright-red “gulmohor” tree, say on the NDA road, snapped by some practising general physician (who has not let his finer sensibilities die despite the demands of his profession and his obviously busy schedule (from 10 to 1 and 4:30 to 7:30, this being Pune))
  6. A photo of the fallen levels of water in the dams nearby. Here, two options are available to the newspaper editor: (i) If he likes a long-shot, show the dry contours of the near-empty reservoir. (ii) If he likes a close-up, show the vertical water level-gauge near the dam wall which used to have red and white markings in a previous life-time.
  7. A photo showing the audience in a small meeting hall, the audience consisting solely of working journalists, the photo itself appearing with a caption that the event was organized for discussing P. Sainath’s book: “Everyone Loves a Good Draught”. … Even without reading anything further from the news, it is easy to make out that they all are working journalists, because:
    1. all the males in the audience have beards and no female seems to have any kind of a make-up put on
    2. regardless of their gender, they all: (a) appear in cotton/khaadi “kurtas,” (b) record news the old-fashioned way, by scribing down in a school-student’s notebook, i.e. without using audio/video recorder, (c) carry “shabnam” bags

I don’t think I have seen any one of the above-mentioned news items in any one of our Pune newspapers (including the local editions of the National Newspapers) … Why is it so? Why? Have our H’ble Ministries/Departments of Information and Broadcasting, Environment, Irrigation, Water Supply, Science and Technology, Meteorology, etc. all been sleeping? Shouldn’t they be more careful and see to it that proper news items are punctually published in all our newspapers? … Weren’t the matters soooo much for the better during those BJP years?

..Err… Leaving aside the dark-grey [“nothing is all black or all white”] humor…

…Ok. Really leaving humor aside and getting serious about something that is worth getting serious about:

Here is a reminder that now is the time to execute at full-speed all those micro-level projects like “paaNi aDavaa, paaNi jiravaa.”

… I don’t know if it is true but it’s a widely held belief that if a summer is unusually hot, as this summer seems to be turning into, then the monsoon following it also tends to be more intense. … A greater rain-fall ought to make for good news in a heavily rains-dependent country like India, but, unfortunately, this always is not true—even a greater rain-fall is only a mixed blessing. In India, just the way we waste any other natural resource (including time), we also put to waste most of the water that falls in this land… The way we function, typically, people wake up about the need to put up small dams in their places only in the month of July (just the way we wake up to the need to put up large dams in place only in mid-May).

The time to act to for the next monsoon is now—at least for those micro-level projects.

– – – – –

A Song I Like:

(Marathi) “nav laakh taLapatee, deep vijeche yeth_…”
Lyrics: “kusumaagraj” (V. V. Shirwadkar)
Music: “aNNasaaheb chitaLkar” (C. Ramchandra)
Singer: “aNNasaaheb chitaLkar” (C. Ramchandra)

PS: If someone can locate a record/CD for this particular song, please drop me an email (aj175tp AT yahoo DOT co DOT in). Thanks in advance!

PPS: Now that I have begun writing shorter blog-posts covering only one-two topics (and so long as I continue doing so) I am going to reduce the number of songs listed in this last section—one, at most two.

[To be streamlined at the time of the next post]

Monsoon / Rains Prediction—My New Interest

Some day in (not too distant a) future I would like to take up studies of weather modeling. Actually, “weather modeling and prediction” would be a much bigger (or general) field. My curiosity and interests lie only with prediction of rains in India.

I am serious.

With my PhD work, I have grown familiar with computer numerical modeling tools and techniques. I would like to put them to some different kind of use. Purely as a matter of a personal hobby—i.e., irrespective of what happens on the job front.

I am well aware of the phenomenon called chaos—both in the strict and the not-so-strict senses of the term. But, really, the way I see it, chaos does *not* matter, or at least, it should not—not to the extent it is made out to… For instance, I want to know why, despite the so-called “butterfly effect”, monsoon does arrive only around the month of June in India. I mean, if the world (or at least its weather) were really to be that “chaotic” (in the sense random),  monsoon might have arrived in December one year, and in March some years later. But this, somehow, does not happen. Ever. Obviously, the world is not really as “chaotic” as chaos theorists would like us to believe.

I am also aware of the rather fine record of the earlier models, e.g., the Govarikar model, and also the new models that the meteorological dept. has been testing/using. I am not entering this field with any ideas that I will necessarily be able to do better than other people.

And yet, I know that unless I give it a real good try on my own, it would always be so very difficult for me to believe that monsoon prediction is really as hard as it is generally made out to be. I mean, it doesn’t matter if it’s hard, and so, I fail in it. The point is, I want to realize just in what way it is hard. By directly “doing it.”

My motivation thus, is, really speaking, purely intellectual curiosity, and even generosity—but not altruism. But, yes, if it will help millions in India who are so crucially dependent on the (timely) arrival of monsoons, why not? I mean, if it’s not going to hurt me in any way, then, why not?

People often confuse generosity with altruism. A good clarification in this context is this: “…Whether I care or not, is irrelevant. I have a right not to care. You have no right to force me to care. …” [Taken from here. Emphasis mine.] Now, altruism, in its actual sense, is not my motivation. It’s just that in this issue (prediction of weather) I would happen to share my knowledge without charging anyone any money, that’s all.

BTW, allow me a real quick aside on this entire issue… Situations are often not quite what meets the eye. For instance, just think who would be willing to fund my research: The government? Of course not. (Independent newcomers are never welcome or funded; amateurs are not even entertained.) The private business? For instance, Reliance or Walmart? LOL! That’s even more remote a possibility. How about VC’s or alumni associations in USA or India? ROTFL. Of course not… Conclusion: Situations are not always what they seem to be. …

… I mean, oh yes. The argument that it is only the government interference in economy in the first place which makes the matters come to such a pass that even the staunchest supporters of privatization wouldn’t come forward to support any research such as mine privately, is, in principle, a valid argument. But my point here is, it’s not the only significant fact which can be stated in matters like this.

It’s, of course, true that businessmen wouldn’t come forward to fund my research. Not even if they themselves are rich. And, more importantly (from an ethical point of view), not even if they themselves are actively looking forward to invest money in the industries that are directly dependent on monsoons, e.g., agro-products. For example, people like Reliance or Walmart. Or, the shipping and airline companies (whose business, too, depends at least in part on weather prediction). None of these companies or characters is going to come forward. Not even if my total budget is never going to exceed 0.1 million  US $ or so. Not even then.

Institutions are, in a physical or raw-power kind of sense, bigger than individuals, and so, in a mixed economy, over a period of time, even the people who come to occupy the top or influential positions at least in dominant businesses or industries are the people who are “businessmen” more in title than in spirit… And, that’s the sad part…

A different kind of businessman comes to occupy the centerstage when the statist elements in the economy become powerful… This has always been the case with India, whether under the Brits or after independence. (Statism precisely is the reason some specific communities like Marwaris and Gujrathis dominate private businesses—there is no such a thing as a “business gene”.)

And, these days, the “different kind of businessman” also is the case with so American businesses. Though, of course, Americans do not like to acknowledge it. Still, this is a fact. Some people seem to be so much in love with the strings “American” and “businessman” taken one at a time or in extaposition that they would rather never acknowledge the facts now-a-days denoted by these words.

This “different” kind of businessman is of the kind to whom you can never sell any idea such as, for instance, the present research. Not because your ideas have no business-value (or “worth”) but because this kind of businessman knows that he can always accumulate far more money far more easily, simply by bribing around and manipulating government controls. Naturally, a character like him would only ask: “What’s the point behind this kind of research? Go to government who take so much taxes from us…” Or worse: “Why all this verbal diarrhea?”

(I must add here that JRD was truely something of an exception—judging by his business practice, that is, and not by his words. His words oftentimes were utterly socialistically inclinded… So, don’t go by his random quotes…. But the fact is, he had extraordinarily high business standards. And vision. … None comes even close to him in today’s India, despite all this privatization and globalization that has been going on 1.5 decades by now. None. Leading Tata managers/owners included. All present-day luminaries of the Indian IT world included.)

But anyway, the research/study itself is going to be interesting… Fluid Mech. and Heat Transfer (in general Thermal Sciences), but in an unusual sort of way… There is this truly real-life i.e. a large-scale application, directly staring in your face, year in and year out…

If you have any directions to give me in my new pursuit, drop me a line. (If you wish not to be named here, that’s fine, just say so…)


Odds and Ends:

Have been thinking about quite a few things in the meanwhile—things of research / science. Will post them here as they become mature enough.

Oh yes, another thing I propose to do is also to list a few recent papers (esp. those appearing at which I have found noteworthy (strictly for my own purposes/random interests). I might discuss a few of them via separate posts here soon.

The above idea had struck me about a month or two back. And then, just a week or two back, I happened across a very good site: … I got to know of it once I happened to pursue a “Trackback” link at an arXiv paper that I had got interested in… Anyway, do have a look at that site and also tell about it to your friends…

I wonder why we don’t have a single such a site/blog in engineering sciences… Sigh…

Anyway, back to <Hindi>”Rim Zim Gire Saawan…”</Hindi> But, <Hindi>”Quon?”</Hindi>

[This post revised and considerably expanded on July 13, 2008, about 11 AM IST. Also coming up very soon: My thoughts on irrigation and water availability in India.]