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…

Submitted on 29 October 2012

The Spectacular Landing of Curiosity

Curiosity descent [image: NASA/JPL-Caltech]

Quite a while ago, I briefly reported on the spectacular Mars Science Laboratory mission that is currently under way. As you are probably aware, the Curiosity rover has now safely landed, and is already exploring the Red Planet. In this article, I want to tell you about the spectacular way in which the rover was put down on the surface. For previous Mars rovers like…

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Submitted on 17 September 2012

Lena

Lena test image

There are two kinds of people in the world. The first have seen the Lena (or Lenna) image before; most of them have done at least some work in image processing, or happen to have read the November 1972 issue of Playboy magazine. The second have probably never seen it.

Submitted on 30 August 2012

Fractal Dimension

The concept of a fractal dimension is based on the idea of measuring things with differently sized rulers, as already mentioned in the article on the Mandelbrot Mandelbrot set. Mathematically (but very loosely), the fractal dimension is defined as: if I cover an object with…

Submitted on 17 June 2012

Fractint

Detail of the Mandelbrot set When I was writing an article on the Mandelbrot set, I looked for software to generate illustrations. Needless to say that there is lots of stuff available for a colorful subject like that. But, lo and behold, I discovered that the venerable Fractint still exists, and is actually still maintained! The program…

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Submitted on 1 May 2012

Where to Launch Your Rocket?

If you want to launch a rocket into space, as I’m sure practically all of you are at least contemplating, where should you do that? The main thing is of course to avoid populated areas, to limit the damage if the thing blows up. The launch pad itself should be located away from people, and there should be a large uninhabited region to the east of the launch site…

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Submitted on 10 April 2012