Google’s PageRank (Sort of) Explained

In this post we’ll take a look at the algorithm which defines Google’s pagerank (PR) analysis. A webpage’s PR is a number between 0 and 10 that Google uses to estimate the usefulness of that page. For example, CNN.com has a PR of 9. A “typical” web site might have a PR of 5. Pages […]

Physics Puzzle: a Race Between Two Marbles

For our weekly puzzle, here is a physics brainteaser to test your mechanics skills (did I mention already those are my favorite puzzles?)

Consider a marble which rolls from start to finish along one of two paths: either an inclined, yet straight plane (B), or a series of valleys and hills passing below that plane (A). […]

Neural Networks Tutorial, Part #3

In our previous tutorial we’ve laid out the basic form of our two layer feed-forward neural network (FFNN). In this installment we’ll derive a way of training it. Just to remind you, here is the basic outline of our neural network, along with all relevant variables:

In general, when training a network, one prepares a […]

Physics Puzzle: Rope Between Two Poles

A good puzzle, someone once told me, is one that can be solved by a bright high-schooler, and yet challenge even a seasoned practitioner. As a puzzle-aficionado, I second that notion, which is why mechanics puzzles are my favorites. It is the most intuitive discipline and the first to be studied in both high school […]

Neural Networks Tutorial, Part #2

A Short Review
In the previous part of our tutorial, I’ve spoken about feed forward neural networks (FFNN), and said that the basic building block of a FFNN is a layer, which can be concisely summarized using the following diagram:

A layer has N inputs and M outputs (schematically represented here by a single line at […]

MATLAB Speed: Using the M-Lint Utility

A great deal of my work is done in MATLAB these days, and I come across many neat little features of the language and the IDE that are hidden among the menus. Sure, you’d know all about them if you read the manual, but who has time for that?
Here is a little trick to help […]

The Pendulum and Truck Puzzle

Still working on the next part of our neural networks tutorial, but in the meantime, a puzzle.
A stationary truck has a pendulum of length L and mass m attached to the top of its insides (see figure A below). The truck driver hits the acceleration and as a result everything sort of gets “thrown back” […]