Skill Bubbles

Skill Bubbles

This colorful bubble chart is a simple way of freshening up your CV by adding the time dimension to your skill list. A simple list has relatively little value, since it doesn’t indicate the importance of each skill. This can be improved by including an estimate of its strength. To do this, you could simply add the number of years of experience, but I propose to go a bit further… read more

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Submitted on 1 February 2013

How to Ensure that Visitors Always See Cached Pages in Drupal 7

All the standard caching options of my Drupal 7 site are enabled. I expected those mechanisms to ensure that the access to a cached page would always be quick, both for human visitors and for web spiders like Googlebot. However, for a small site, this is not so. The Drupal caching mechanism does not work as you might expect. For me, there is a clear difference between… read more

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Submitted on 21 January 2013

GiraffePhoto Page

Giraffe

A Giraffe at Utah’s Hogle Zoo, Salt Lake City, Utah, United States. read more

7 Cool Reference Sites on Mathematics

We all have to look things up once in a while, and I can tell you right now that Wikipedia is the best source for practical information on mathematics. But, there are some others out there that are also worth knowing. Most of these sites are encyclopedic, and not meant for browsing top down, so I’ve used the entry for eigenvector as an example for… read more

Submitted on 9 January 2013

Skirmish with Spam

I was going to call this article War on Spam. But, given how well my experiments went, I had to retitle it Skirmish with Spam. Lately, the number of spam attempts has risen so much that even Mollom lets through enough spam to get me a bit miffed. So, I decided to go “old school”… I was going to add math problems of increasing difficulty until… read more

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Submitted on 22 December 2012

Tomography, Part 4: Algebra!

The first three articles on tomography focused on analytic techniques, in which the reconstruction problem is attacked using mathematical analysis. When the step to real world scanners is made, the problem is discretized. Both the projections and the reconstruction area are divided into pixels, and a numerical approximation of the true mathematical technique is introduced. The algebraic techniques assume… read more

Submitted on 9 December 2012

Tomography, Part 2: Yes, You Can

Sinograms of box with ball

This article shows that it is possible to reconstruct the inside of a person or object from (lots of) projections of that person or object. Mathematically, tomography is based on the fact that the function values of a two-dimension functional \(f(x,y)\) can be calculated from projections of that function. This basic fact was discovered… read more

Submitted on 11 November 2012

Tomography, Part 1: Projections

Projection of box with ball

Have you ever wondered how a CT (or CAT) scanner creates an image of the inside of a person? The answer is computing. CT and CAT are short for computed (axial) tomography. Computing is the secret sauce that is poured over the hundreds or thousands of X-ray photos that make up a CT scan, to merge them into a single image. This first article on tomography explains projections, the essential input data for tomography… read more

Submitted on 29 October 2012

Designer QR Codes

Angry Birds QR code [image: Visualead]

In the article Color QR Codes Done Right, I’ve tried to convince you to create your color QR codes in a way that keeps them easily scannable. This week, I’ve discovered Visualead, a startup that is currently in Public Beta, that lets you combine any artwork with a QR code. Graphically, they have nailed it. They seem to have found out that… read more

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Submitted on 12 October 2012

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