New Publication on ordering in vertically vibrated Granular Rods


Here is a link to my new publication on ordering in vertically vibrated granular rods. This work was featured on kaleidoscope section of Physical Review-E and appeared on front page of PR-E website. Here is a pic 🙂


The paper also details a method for tracking hollow rods in 3-d using X-ray Computer Tomography data. The tracking code was written in Matlab and requires Image Processing Toolbox. I’ll write a separate blog entry detailing the algorithm used for tracking rods in 3d.

Following were the main observations of this experiment:

  1. Vertically vibrated Granular rods go to vertically ordered crystalline state.
  2. Global ordering depends on aspect ratio of granular rods. Longer rods tends to form perfectly order crystalline states with hexagonal order in interior, whereas shorter rods tend to form more defects (regions of horizontally ordered rods).
  3. The temporal evolution of ordering can be explained using a void filling model.
  4. Using a point-correlation function we can show that extent of hexagonal ordering increases with aspect ratio of rods.
  5. By adding more number of rods (than required to grow a perfectly crystalline layer) we can grow a multiple layer crystal. Though we observe that higher layer tend to have more defects. We attribute this to inefficient energy transfer from bottom of shaker to top layers due inelastic collision in intermediate layers.

If you are interested in this work but do not have access to Physical Review-E send me an email at and i’ll send you a copy of this work.

Refresh and Restart


So, after quite a while I have decided to get back to blogging. Though I have never been an active blogger, I have tried my hands at it now and then. Recently one of my close friend manish, got me into habit of reading HBR (Harvard Business Review). HBR has a blog section that can be accessed freely. I was amazed by the width of useful articles being published there on a daily basis. I think i can find something personally useful almost everyday or at most every other day. I restart with a hope that someone somewhere finds the stuff on this blog useful.

Remembering V. I. Arnold

V. I. Arnold

I believed that i understood Classical Mechanics. When i look back i see this idea originated when i was preparing for IIT-JEE. Since i could solve mechanics problems from H.C. Verma, Resnick and Halliday, and a few from I.E. Irodov, i thought i was the king of classical mechanics. Years later even when i took a graduate course on Mechanics (Goldstein) i felt the same. The techniques of solving problems changed but it was all the same mechanics.

Someone (I think it was Shakir) once told me about an excellent but extremely difficult Russian text on mechanics. It was titled “Mathematical Methods of Classical Mechanics” by V.I. Arnold. As i was the greatest Physicist the earth has ever seen (i really believed so), i quickly grabbed a copy of this text from my library. That night i sat down with this book, a few pages and a pen, determined to finish a chapter or two.

The next one hour changed me.

I realized how little i knew. I realized there is much more than just being able to solve problems. I realized power of a different viewpoint, the power of geometry.

Ever since then, Arnold became a God for me and his books became the sacred texts. The untimely death of Prof. Arnold on 3rd June, 2010 (aged 72) is a huge loss to Physics community worldwide. It’s a shame that American Physical Society (APS) didn’t even cared to publish an Obituary in any of their publications.

My first post is dedicated to my hero prof V.I. Arnold. His works and texts have guided and given insight to generations of Physicists and Mathematicians and will keep on doing so till eternity.