Robert Eisele
Engineer, Systems Architect and DBA

# Creating an Advent Calendar with HTML5 and CSS3

Christmas is near and I wanted to soothe the remaining time till Christmas Eve for my friends with something special. So I thought, why not building an Advent calendar with HTML5 and CSS3 for them, which gets filled with personal things I want to give to them? It turned out to be a very cool project and I wanted to share the thing in order to let you make one yourself for your own friends. If you just want to download the source, you can check it out on github, for everyone else, I'll guide you through the process of making an own Advent calendar. The final calendar for the public can be seen here (you can come every day and find a new gift):

# Constructing Hexagonal Baseplate for a Stewart Platform

A Stewart platform is a nice way to learn lots of motion dynamics. I'm in the process of creating an own prototype myself, so stay tuned. For now I want to focus on constructing a typical baseplate, which can be 3D printed or cut out off acrylic glass or aluminium.

# Derivation of Pagination Calculation

I have already devoted two articles to the topic of Pagination, one for the jQuery Pagination plugin and the other one on how to optimize MySQL queries for pagination. I'd like to add another one for the mathematical derivation, I used there.

# Calculate the intersection point of two Lines

Given two lines $$L_1$$ and $$L_2$$, how is it possible to calculate the point $$P$$ of intersection of these two objects? Like always, set the equations of the objects involved equal and solve for the parameters. For the two lines this means:

# Calculate the Tangent Line of a Circle

Given a circle with it's center point $$M$$, the radius $$r$$ and an angle $$\alpha$$ of the radius line, how can one calculate the tangent line on the circle in point $$T$$? The trick is, that the radius line and the tangent line are perpendicular. This means, that their dot-product must be zero.

# How to write a PHP Daemon

PHP is a language primarily used by web developers, but even these have problems which have to be scheduled to background processes, like sending newsletters, analysing stats, or simply maintaining the database. The most common way to solve this, is abusing crond for almost everything. When things are getting more complicated, like running jobs every 10 seconds people get really creative like blocking the execution or whatever silly custom.

# Calculate the intersection area of two circles

Similarly to the article about intersection points of two circles we're now interested in the area that is formed by the intersection of two overlapping circles. We could formulate cases to step through the same as in the other article, but I will do it a little shorter this time.

# Improving Interval Conditions

Checking if a certain number $$x$$ falls into a given range between $$a$$ and $$b$$ is a quite easy task: