the blog of small things

Kathy Sierra on teaching

2005-04-07T21:09:00.000-07:00

You really ought to check out Kathy Sierra's blog, "Creating Passionate Users". It is full of interesting nuggets about how to transfer stuff -- concepts, ideas, info, etc. -- from one brain to another brain, through books, courses, seminars, conferernces, whatever. Kathy is one of the authors of the "Head First ..." series of books (published by O'Reilly) that teach concepts in programming and software development using highly informal -- but tremendously attractive -- techniques. Her posts on teaching are informed by her experience with the "Head First" series of books.

Here are the links to Kathy's posts that are relevant to teaching:

I am sure you too would agree that she has lots of interesting things to say!

Annals of academic angst

2005-04-05T05:09:00.000-07:00

Well, it has been a while since I posted here. Things were very hectic at home, with everyone deciding to fall sick, almost as if on cue, at the same time. However, everyone is back to their normal business, and it feels good to be back.

Today, I provide links to just a couple of posts; while the posts are by academics in liberal arts / humanities, everyone should be able to identify with the deeply felt views expressed by them.

The first one is from Adam Kotsko (probably a budding academic), who is grappling with what he needs to do to pass academic muster in his chosen field of philosophy. Though he likes conversing with great minds (by reading their texts), he seems exasperated by the "need to make these texts into something, turn them toward the goal of producing my own piece of writing so that I will continue to meet the requirements of scholarly productivity which graduate study is socializing into me". He finds himself trying to "figure out some way to squeeze out a paper on Zizek's use of Kierkegaard, so that I can send it off and people will publish it, so that I can write down on a piece of paper that it has been published".

Look at how an experienced academic -- Prof. Bradford DeLong, a Berkeley economist -- poses the same problem. Academia should really be about conversing with great minds and finding a compelling voice for yourself -- all the while having a great deal of fun. Academic pursuit's resemblance to a game whose goal is to build a CV of professional achievements, if it is taken seriously, will only lead to cynicism that makes you feel let down.

Best thing about both these posts is how beautifully they are able to express -- through just, plain words -- the deepest feelings of their authors. I wish I could do that ...

Update: Over at Uncertain Principles, Chad Orzel displays a different type of angst. This time, his musings are about "really important work" vs. "good enough" work, with the former being defined as that worthy of Physical Review Letters (we know what the latter is, don't we? ;-). Thankfully, his inner voice has put him back on track:

[...] every little bit helps. Small papers count almost as much as important ones, when it comes to demonstrating a research track record for a tenure review. By continuing to think big, I'm shooting myself in the foot ...

The big one is here!

2005-03-20T23:15:00.000-08:00

Nano-2006, The next edition of the mother of all nano-related conferences, has been announced. It will be held here in our Institute during 21-26 August 2006. The Conference is chaired by two of our colleagues in our Department: Prof. Kamanio Chattopadhyay and Prof. Atul Chokshi.

The previous edition, Nano-2004 (the Seventh International Conference on Nanostructured Materials), was held at Weisbaden in Germany during June 2004. You might want to take a look at its website to get a flavour for this series of conferences.

Let it be noted that, in direct contrast to their subject matter, these conferences tend to be rather Giga in scale ...

The Monty Hall puzzle

2005-03-12T06:07:00.000-08:00

An article by Junpei Sekino begins thus:

On one Sunday of September 1990, the following question appeared in the Ask Marilyn column in Parade, a Sunday supplement of local newspapers.

Suppose you're on a game show, and you're given the choice of three doors; Behind one door is a car; behind the others, goats. You pick a door, say No.1 and the host, who knows what's behind the doors, opens another door, say No.3, which has a goat. He then says to you, "Do you want to pick door No.2?" Is it to your advantage to switch your choice? -Craig F. Whitaker, Columbia, Md.

Now, having read the original version of the Monty Hall puzzle, try to find an answer. Then read various excellent accounts of this puzzle in the article by Junpei Sekino, as well as here, and here. I found all these links in a comment by Enrico Scalas to a post by Tommaso Dorigo over at the Quantum Diaries website, through which you can "follow physicists from around the world as they live the World Year of Physics 2005"

Finally, let me quote Tommaso Dorigo: "...several Professors of Physics got it [the puzzle] wrong when I tried it with them, and one well-known theoretical physicist actually had to run a Monte Carlo simulation in order to become convinced of the solution".

What are colleges good for?

2005-03-08T04:34:00.000-08:00

Matthew Yglesias, a Harvard alumnus, has a couple of interesting posts about this subject. Also, take a look at Tim Burke's views in this thoughtful essay.

Google's recruiting technique

2005-03-08T03:28:00.000-08:00

In an earlier post, I linked to some posts about a very effective recruiting technique employed by Google. Somehow, I missed this MathWorld post, which has answers to these and other clever and geeky puzzles from Google.

Charming ...

An altogether impure metal

2005-02-07T23:02:00.000-08:00

Whatever can be the motivation for academic life? Nietzsche's answer is simply delicious! I found this extended quote -- a passage from Nietzsche's essay, "Schopenhauer as Educator" -- in a post by John Holbo over at Crooked Timber:

It can hardly originate in any supposed 'desire for truth': for how could there exist any desire at all for cold, pure, inconsequential knowledge! What it really is that impels the servants of science is only too obvious to the unprejudiced eye: and it is very advisable to prove and dissect the men of learning themselves for once, since they for their part are quite accustomed to laying bold hands on everything in the world, even the most venerable things, and taking them to pieces. If I am to speak out, I would say this: the man of learning consists of a confused network of very various impulses and stimuli, he is an altogether impure metal. First of all there is a strong and ever more intense curiosity, the search for adventures in the domain of knowlege, the constant stimulation exercised by thte new and rare in contrast to the old and tedious. Then there is a certain drive to dialectical investigation, the huntsman's joy in following the sly fox's path in the realm of thought, so that it is not really truth that is sought but the seeking itself, and the main pleasure consists in the cunning tracking, encircling and correct killing. Now add to this the impulse to contradiction, the personality wanting to be aware of itself and to make itself felt in opposition to all others; the stuggle becomes a pleasure and the goal is personal victory, the struggle for truth being only a pretext. Then, the man of learning is to a great extent also motivated to the discovery of certain 'truths', motivated that is by his subjection to certain ruling persons, castes, opinions, churches, governments: he feels it is to his advantage to bring 'truth' over to their side.

Impure metal, indeed!

Online books in Materials Science?

2005-01-24T03:14:00.000-08:00

Note: Originally posted on 24 January 2005.

Towards the end of his Netspeak column in today's Hindu, J. Murali points to the Internet Text Archive, "an excellent web location that hosts links to several free open source textbook digitizing [or] hosting projects that include Project Gutenberg, Children's Library, Million Books Project and Open Source Books". It is probably worth a look.

If you look around on the web, you will find quite a few books whose authors (and in some cases, publishers too) have chosen to offer them for free. Among the publishers, the following are noteworthy:

Open Book project of O'Reilly, a well known publisher in the fields of programming and software development
eScholarship program of the California Digital Library, one of the University of California libraries. Some of the books in CDL are open for public; check out this subject list to see if there is anything of interest to you.

Then there are books that live both in shelves and in hard disks. Sure, some of them are quite specialized (with a potential readership of, say, a few hundreds); but, there are a few others which are at the undergraduate or equivalent level in popular subjects (software development!). Examples of the latter include:

Bruce Eckel: Thinking in C++
Bruce Eckel: Thinking in Java
Gerald Jay Sussman and Jack Wisdom: Structure and Interpretation of Classical Mechanics
Harold Abelson, Gerald Jay Sussman and Julie Sussman: Structure and Interpretation of Computer Programs

I am not sure about the others, but I do know that the first two are very popular: they are still in print, you can buy them in shops, and apparently, many people do! In fact, Eckel loves this publishing model, and says, "All of my future books will be electronically published on my site first, and will stay on the site".

There are still a few other books which live almost entirely in the electronic world; for example, The Temple of Quantum Computing is an introductory book that its author has described as quantum computing for dummies.

Is there a good reason why there are not many online books (available either for free or for a reasonably small price) in materials science and engineering? I found two online texts in Chemistry: Dynamic Textbook of Physical Chemistry and Concepts in Chemistry. I listed them in my Thermodynamics course website.

It is entirely possible that there are more such books that are available online, and are useful for students of materials science and engineering. If you know of any, do please send me its URL, and let us start compiling a list here!

Update (25 Jan 2005): The process of building up this list begins here! Here we go:

Harry Bhadeshia: Bainite in Steels
Harry Bhadeshia: Worked Examples in the Geometry of Crystals
Edgar Bain: Alloying Elements in Steel (Harry Bhadeshia has produced this electronic version with permission from ASM International, and hosts it on his website)
Kaushik Bhattacharya: Theory of Martensitic Microstructure and the Shape-Memory Effect
John A. Venables: Lecture notes on "Surfaces and Thin Films" (Their near-completeness and organization should make these notes a 'book', and indeed, they form the basis for a dead-tree version from the Cambridge University Press)

If you know more such online texts, bring'em on!

Phase field models: Chapter outline

2005-01-19T06:13:00.000-08:00

I have accepted an invitation to be a co-author of a chapter on simulation techniques in alloy physics; this chapter will cover Monte Carlo, molecular dynamics and phase field techniques. You have guessed it: my main contribution is in the last section.

I am still trying to figure out who the audience will be (senior undergraduates, graduate students, or practising researchers), and whether they may be expected to know some of this stuff. So, I am still not able to decide how to pitch the section on phase field models. For example, should it be a high level overview, a tutorial, or something in between? Should I (a) try to solve some example problems, (b) include (possibly gory) details of numerical implementation, (c) give chapter-end problems? I need answers to these questions before I can decide on things such as the number of sketches and microstructures, number and level of equations, etc.

As for content, which has to be covered in about 15 pages or so, I am looking at the following generic outline:

Accessible length and time scales
Cahn-Hilliard and Cahn-Allen models as prototypes
Their extension to models with multiple order parameters
Implementation details: periodic boundary conditions, finite difference methods, Fourier spectral methods
Survey of applications: phase separation, ordering, precipitation of an ordered phase, elastic stress effects, grain boundary effects, grain growth, solidification

When I did a quick mind-map of phase field models, I realized that they can be introduced or approached from quite a few different angles: (a) models rooted in statistical physics (e.g., Cahn-Hilliard or Cahn-Allen models), (b) models that "just happen to" mimic real systems (grain growth models), or (c) models that simply provide mathematical convenience (solidification models with a rather fictitious order parameter that helps differentiate a solid from a liquid). There are probably other angles as well.

I guess I am in for a rather interesting experience. I am sure it will be fun, and I am excited.

Weightless wonders

2005-01-14T23:29:00.000-08:00

Note: This was originally posted on 13 January 2005.

Today, Prof. John Banhart, Chairman of the Department of Materials at Hahn-Meitner Institute Berlin, gave an excellent talk on metal foams, those delightfully weightless wonders. His lecture is indeed a great example of how to present an overview; he covered several aspects of metal foams: (a) how foams can be made, (b) why they might be useful, (c) their actual and potential applications, and (d) the scientific challenges they pose.

The moment Prof. Banhart said he was going to give an overview, my first reaction (which turned out to be rather misplaced -- more on this below) was: "God, are we in for another one of those light weight (please pardon the pun) talks?"; I was delighted to be disappointed! Prof. Banhart showed us how to present an overview without having it perceived as short on scientific content. While his chosen format forced him to spread himself thin by covering a lot of material, he made sure that he said something about the scientific issues in almost every topic.

For example, when he talked about the powder metallurgy route for making aluminium alloy foams (quite a bit like making bread), he showed an X-ray video of the process of foaming, which indicated large, almost crack-like pores that appeared first. His commentary for the video went like this: "Look, this is an important issue because it will have a bearing on the properties. We have done some work to understand why this happens, and what can be done to ensure the initial pore formation is more uniform, and more rounded". He did eventually cover these issues when his talk turned to the open scientific issues.

Similarly, in the section on properties of foams, he first showed the stress-strain response of foamy materials, followed by how these properties can be exploited in particular ways: light weight (stiffness per unit weight and unit thickness), high energy absorption during impact (at efficiency levels as high as 85 %) and better damping of vibrations. He gave specific examples of applications (those that are in wide use as well as those that are at the prototype or demonstration stage). Once again, he used science and mechanics based arguments to show why these applications make sense.

What was absolutely impressive was Prof. Banhart's rather disarming way of lightening (pardon the pun again; "light" seems to be the word of the day for me) the talk. For example, he showed a video of a coffee cup that remained a coffee cup after falling on a piece of metal foam, but shattered when it fell on the floor; after the video, he said, "Now you know why foams are so attractive as construction materials; they will protect your coffee cups!". Another example of his disarming charm was on display when he revealed that he doesn't believe now some of the things he said 5 to 10 years ago (in journal articles, no less!) and, by the same token, he may not believe -- say, five years from now -- some of the things he said in today's seminar!

All in all, it was a wonderful lecture. It was well worth coming to work on a Saturday morning!

Just a couple of quick links to sites with more information on metal foams: Metal Foams section of HMI, and the metalfoam.net.

Think small with phase field models

2005-01-05T22:47:00.000-08:00

Note: This was originally posted on 6 January 2005.

Phase field (PF) models are truly great for studying a wide variety of problems and phenomena. Given all the buzz (not to mention the beautiful microstructures), more and more people are getting interested in using them in their work. More importantly, the buzz is not just confined to academia; it has spread to others (particularly, those in industrial research centers) as well. Clearly, the PR has been fantastic!

We now have a larger community of people who will be applying PF models to lots of new, practical and industrially relevant problems. These new problems, together with the new ideas that are generated for solving them will broaden as well as deepen the field. There is no doubt that this is a positive development.

Much of the buzz arises from the impression that any materials problem involving migrating interfaces (or other structural discontinuities, such as dislocations) is ripe for PF models. There is certainly a strong basis for this impression. You just have to look at the range of materials problems for which PF models have been applied: solidification, diffusional and diffusionless phase transformations, recrystallization and grain growth, sintering, dislocations. Still, I want to pose this question: is this impression correct? In other words, are there problems that PF models are not good for?

The way I see it, PF models are good for two broad kinds of problems: those that examine some key (minute or microscopic) details of evolution of a microstructural feature, and those that require large scale simulations. Studies on the former type of problems can be called “small-scale” or “local", while those of the latter type, “large-scale” or “global".

Local studies would focus, for example, on:

details (morphology, growth rate) of a single microstructural entity such as a dendrite or a precipitate
topological transitions during grain growth
nucleation morphologies of multiple variants in a martensitic-like transformation

In each case, the aim is to examine the microscopic details of the process to elucidate the role of different factors during nucleation and further development of the microstructure.

Global studies, on the other hand, focus on the microstructure in a large region. Clearly, the larger the simulation box, the better. With larger simulations, statistics become better; more importantly, effects of long range interactions (electrical, elastic, diffusional) can be better studied, and finite-size effects are smaller.

However, even in the large-scale studies, the simulation box is not truly large or macroscopic - we will consider an example below - they are “large-scale” only in relation to the current computational capabilities. With this understanding, it is now clear that we can use such studies only for those problems where it is reasonable to assume that the simulation box is representative of the entire sample. This “representative-box” assumption is not unique to PF models, however; it is central to many experimental studies. For example, in detailed microscopic characterization of materials (and TEM in particular), we implicitly assume that what we see in one area is truly representative of the entire sample. For this assumption to be fulfilled, the obvious requirement is that the experimental conditions experienced by every sub-region in a macroscopic sample must be identical; so, for example, we ensure that the sample is kept under constant temperature and pressure.

To get back to the question: are there problems that PF models are not good for? The answer, unfortunately, is that there indeed are. Many problems of practical interest fail this “representative-box” test. Examples include solidification in a casting or a weld, phase transformations or grain growth under temperature gradients, etc. For problems of this kind, PF models are just inappropriate. This assertion follows from a fundamental feature of all PF models: their characteristic length scale, which is the width of the interface, ‘w’. For practical problems where microstructures change (i.e., exhibit gradients) over length scales that are too large compared to ‘w’, we have no hope of using PF models. Let me take an example problem: grain growth.

In using PF models, we are basically interested in probing microstructures with a characteristic length scale. For example, in a typical polycrystalline metal, the grain size is about 1 micron, and we are interested in studying how, and how fast, this microstructure evolves. For this we rig up a PF model with an interface width, ‘w’. In simulations, in the interest of stable numerical computation, we want at least four grid points to span this width, so we have w = 4 * Delta x. In our example, we would further like two parallel boundaries (which we may take as d, the grain size) to be separated at least by several (say, 10 times) widths: thus, d = 10 * w = 40 * Delta x. If we have a 2D simulation box with 1000 x 1000 grid points with a grid spacing of Delta x, we will have approximately n=25 grains to a side, to yield a total of about n-squared = 625 grains in the simulation box.

This brings us to the key point: the simulation box is only about 25*d = 25 microns wide! What if the problem involves microstructural gradients which extend over hundreds or thousands of microns? We have to come to the sad conclusion that PF models are just not good enough for such problems. Remember, we are not even talking about the third dimension that is so important to all of us! In 3D, the impact of this conclusion is even stronger.

It is going to take a giant leap in computational capabilities (well beyond the already fantastic, exponential progress that follows from Moore’s law) before we can contemplate solving practical problems involving graded microstructures. Until then, we just have to live with this fundamental limitation.

So, you now have the answer: with PF models, you can only think small! I bet you will (probably truthfully) say that you knew it all along …

Three great texts on microstructures

2005-01-03T13:34:00.000-08:00

Here they are, in the order of increasing level of generality, presentation and discussion:

J.W. Martin, R.D. Doherty and B. Cantor, 1997: ‘Stability of microstructures in metallic systems’, Second edition, Cambridge University Press (IISc Main Library, 620.94 N97).
As the name implies, this book contains “pure metallurgy", and it is great. The approach makes use of macroscopic thermo and kinetic ideas, that are familiar to those with undergraduate training not only in metallurgy, but also in materials engineering and ceramics.
Rob Phillips, 2001: ‘Crystals, defects and microstructures’, Cambridge University Press (Metallurgy Library, 168829).
This book straddles the fields of physics, continuum mechanics and materials science, and does it rather well. I would bet that it could become a bestseller in India if a low-priced edition is available; this is so particularly because of its ability to talk to, and interpret the languages of, people working in diverse fields: physics, mechanics, materials science and engineering.
P.M. Chaikin and T.C. Lubensky, 1998: ‘Principles of condensed matter physics’, Cambridge University Press (IISc Main Library, 530.41 N98).
This book is oriented towards graduate students in physics, and requires some serious facility with math. It is not just about microstructures, of course. It has an excellent discussion of models for all kinds of systems and phase transitions: crystalline solids, liquid crystals, liquids, magnetic materials, …

It turns out that all these books are published by the Cambridge University Press (CUP). The Indian paperback edition of Chaikin and Lubensky, at under Rs. 300 (about 6 US Dollars), is eminently affordable; my friends in physics tell me that it is a bestseller of sorts among physics students in India. Now, if only CUP can be convinced to bring out Indian editions of the others …

The first post

2004-12-17T07:00:00.000-08:00

Note: This was originally posted on 17 December 2004.

Hello, there! Welcome to my blog of small things.

Right now, things that interest me professionally happen to be small: microstructures in materials, and this blog is largely about them. You will, therefore, find thoughts, opinion, commentary, speculations, and yes, rants on whatever I find interesting in the science of microstructures. Given my research interests, there will be a bias towards modelling and simulations.

Since I am an academic, there will naturally be some stuff on doing science, research and teaching, and especially on being an academic in India. There will also be, when appropriate, some posts on what we all affectionately call The Institute : Indian Institute of Science.

As Paul Graham states in this memorable essay, I too find that when I put my thoughts down in writing, things become clearer to me. So, you see, the main reason for this blog is purely personal (did I hear someone mutter “navel-gazing”?). Having said that, I do want to make sure that what I say is sensible, even to those who happen to just visit this blog (perhaps by accident). So, I promise to do my best to write clearly, coherently and convincingly.

Enough of this for now! Let's get on with it!

Update (13 April 2005): The content here is an import (cross-posting) of some (only some) of the posts I made (and continue to make) over at my blog hosted on our Department's server. So, datestamps here may not be accurate (though I will try to keep to the original date stamps; for example, I moved this post here only today, but it was posted on 17 December 2004). I will keep moving some of the posts that are already there to this location over the next few days; after this job is done, posting must be almost simultaneous.

The reason I have here a copy is that I now have some sense of permanence; on a more practical level, I also find it much easier to manage my blog at blogger.